Assessment of cervical spine morphology by computed tomography and its utility as a presurgical planning tool

Transcription

1 The University of Toledo The University of Toledo Digital Repository Theses and Dissertations 2004 Assessment of cervical spine morphology by computed tomography and its utility as a presurgical planning tool Jan Martensen Medical College of Ohio Follow this and additional works at: Recommended Citation Martensen, Jan, "Assessment of cervical spine morphology by computed tomography and its utility as a presurgical planning tool" (2004). Theses and Dissertations This Dissertation is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's About page.

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3 Assessment of Cervical Spine Morphology by Computed Tomography and Its Utility as a Presurgical Planning Tool. Jan Martensen Medical College of Ohio, Toledo, OH May 2004

4 Acknowledgements: When one completes a project like this there are many people to thank. Dr Michael Dennis, my major advisor, thank you for being a patient guy, for your guidance, encouragement and a friend. This degree and project would not have happened, if not for your efforts. Dr. Brinker for taking me into the program, asking good questions and always the encourager. Dr. Potvin for opening the doors to medical physics for me. I had no clue how exciting it could be. Dr Yeasting for always being willing to help, for being the consummate teacher and your encouragement. Dr Ebraheim for helping me cast the vision for this project and being a great example of doing the work. There are many others that need to thanked, Tech s in radiology, professors at MCO, staff in the library, staff in student services, staff in the Dean s office, etc. There is, however, always one person that stands out from the rest who has no personal gain from being involved but who goes beyond the call of duty. For me at MCO, this person was Dean Schlender. Thank you! Finally, I want to thank my lovely wife Leah for putting up with me during this process. It was long and hard but you persevered. Thank you. Jan Martensen May 2004 (James 1:5) 2

5 Table of Content Title page 1 Acknowledgements 2 Table of Content 3 Introduction 4 Review of pertinent literature 12 Methods 19 Results 25 Discussion 36 Conclusion 47 References 49 Appendix 53 Abstract 169 3

6 INTRODUCTION For years the study of the low back anatomy, biomechanics, treatment protocols, surgical techniques and rehabilitation techniques has dominated the spine literature. The cervical spine has received a lot more attention in the last two decades from the medical and biomedical community. The interest from the biomedical community has in large part related to biomechanics, particularly associated with motor vehicle accidents and sports related injuries. High speed accidents and roll-overs are not uncommon anymore. The medical community has had great interest in the cervical spine due to its prominence in traumatic situations with its neurological or possible neurological complications. A 1992 estimate of about 10,000 people per year in the United States sustain spinal cord injury with a prevalence of approximately 200,000 in any given year. (Flanders 1992) Surgical treatment of the cervical spine is complicated by a variety of factors. The anatomy of the cervical spine is compact, the cervical spine is situated deep underneath multiple layers of muscle posteriorward and muscle, neurovascular and upper GI tract (specifically, the esophagus) and respiratory tract anteriorly. The anatomy of each individual segment varies according to level and gender. A variety of studies in the past have quantified the morphological characteristics of the cervical vertebrae, including Panjabi et al. (Panjabi 1993) describing the cervical facet articulations; Bailey et al. (Bailey 1995) describing the relationships between the bony and soft tissue structures and gradient of variation; Ebraheim et al. (Ebraheim1) describing the intervertebral foramen and cervical nerve root groove; Xu (Xu 1999) describing the lateral mass and its relationship to the spinal nerve and dorsal ramus; Ebraheim et al. (Ebraheim 1997) describing the subaxial cervical pedicle and its projection; Kameyama et al. (Kameyama 1994) describing the cadaveric 4

7 cervical spina cord; Karaikovic et al. (Karaikovic 1997) describing the human cervical pedicle morphology; Ebraheim et al. (Ebraheim 1996) describing the location of the vertebral artery foramen and its relation to the lateral mass; and Ebraheim et al. (Ebraheim 1997) describing the cervical facet and the posterior projection of the inferior facet. Common features of these studies are the detailed morphological analysis of the anatomy, the reference to the use of radiography and occasionally computed tomography as a reference tool for pre-surgical planning and post-op evaluation, however without measurement of the anatomy on radiographs and or computed tomography images to correlate the accuracy with the morphological measures. Xu (Xu 1999) indicate that CT is not able to evaluate if the spinal nerve has been violated by a screw penetrating the anterior cortex of the lateral mass. Another common feature is the variability between each segment morphology and difference between male and female morphology. The surgical techniques available for the cervical spine has developed over the last three to four decades providing a variety of choices and decisions for the surgeon prior to operating on the patient. Posterior approaches include laminotomy/discectomy for osteophyte and disc decompression; laminectomy/foraminotomy creating a window of variable size +/- disc removal if bulging is present; a variety of wiring procedures, including facet wiring, interspinous wiring and sublaminar wiring; a variety of screwplate fixation procedures including Roy-Camille in France (1964), followed by Louis in France (1972) and Magerl in Switzerland (1970). The Roy-Camille procedure for lateral mass fixation was introduced to the USA by Ebraheim. (Ebraheim 1999) Since other surgeons in the USA have introduced variations of lateral mass fixation, including An 5

8 (An 1991) and Anderson. (Anderson 1991) Anterior approaches likewise are numerous. Initially anterior approaches by Cloward and Smith-Robinson did not use instrumentation. Orozco in 1970 indicated the use of screw-plate fixation gained significant stability and expanded the indications for the anterior approach. A number of companies have developed a variety of hardware for internal fixation. Included are Caspar plates, Morscher plates and Cervical Spine Locking Plates (CSLP) for the anterior approaches and Tubular plates, Haid plates, Hook plates and Halifax clamps for posterior approaches. (Kaplan 2002; Huckell ) In addition to deciding the most appropriate type of hardware, the surgeon must also consider the effect the hardware will have on future imaging studies. MRI is used heavily in neurological imaging due to its signal intensity characteristics and its ability to differentiate white matter from grey matter, fat from muscle and nerve, marrow from neoplasm and marrow edema from normal marrow. If the patient has complications or develop a new symptom picture, MRI would be the primary imaging tool used (unless other contra-indications exist). If the surgeon use metals with high magnetic susceptibility, such as ferrous containing metals, significant artifact ensues, however if metals such as titanium or nickel are used little artifact formation ensues. (Lufkin 1990) In addition to trauma as an origin of instability, degenerative, rheumatologic and neoplastic conditions may also contribute to instability. Considering the above factors it is obvious the surgeon must be knowledgeable of the anatomy of cervical spine, knowledgeable of hardware choices and possess great surgical skill. Complications of cervical spine surgical procedures include impingement and violation of the all important 6

9 vertebral artery, located anterior lateral to the lateral mass, the spinal nerve exiting in the intervertebral foramen located immediately anterior to the lateral mass and above the pedicle, the spinal cord and dorsal ramus extending posterior along the lateral mass. Other soft tissue complications include would infection, seroma, epidural scar, epidural hematoma and hoarseness. Bone and bone graft complications include nonunion, end plate fracture, graft collapse, graft reabsorption, displaced strut graft and instability. Hardware complications include screw in disc space, screw displacement, screw backing out, screw in spinal canal, screw loosening, screw loosening and hematoma, broken screw and slipped rod. This study will focus primarily on anatomy and imaging of anatomy of the cervical spine but information gained through this study will affect hardware choices and will enhance the surgeon's ability to perform his skill with excellence. Knowledge of anatomy of the cervical spine is essential however. As previously mentioned, there is variability in the size, shape, orientation and configuration of individual anatomical parts of each segment as well as variability between sexes. Imaging atlases detailing the anatomy of cervical spine have been published, however usually generalize the subject and overall are not useful as a pre-surgical planning tool for an individual patient. Imaging studies of each individual patient are obtained prior to surgery and may include plain film radiography, computed tomography, fluoroscopy, myelography, tomography and magnetic resonance imaging. Each imaging modality has advantages and disadvantages. Plain film radiography is excellent for evaluation of gross bone pathology however evaluation of soft tissues is mostly indirect. Also plain radiography is three-dimensional anatomy 7

10 pictured in two dimensions with limited contrast. Computed tomography adds the advantage of obtaining thin slices in the axial plane with a significant increase in the level of contrast. Reconstruction in other planes is available as well as three-dimensional reconstruction. Disadvantage again is in regard to soft tissue. CT is not able to distinguish between muscle, ligament, tendon, vascular or neurological tissues unless separated by tissue of higher or lesser density. MRI has the main advantage of separating soft tissues however some tissues of low signal intensity such as ligament, cartilage and tendons are very difficult to distinguish from osseous tissues, which also have low signal intensity. This disadvantage makes measurements on MRI of osseous structures difficult and possibly precarious for the patient. Fluoroscopy is resolution limited but very useful for instant localization during a surgical procedure. Tomography is also resolution limited and only displays the anatomy in the slice of interest. It is primarily used for bony detail with very little to no soft tissue detail. Tomography also lacks contrast. Myelography can demonstrate contour defect of the spinal cord or thecal sac from processes that originate from intra- or extra-dural locations. This study will use CT for evaluation of osseous anatomy of the cervical spine due to the high detail and contrast obtained for osseous structures as well as its capacity for reformatting in orthogonal planes. Several studies have evaluated the performance of CT for morphological evaluation and as a pre-surgical planning tool. Yoo et al. (Yoo 1997) used CT to identify pedicle screw placement in cadaveric human lumbar spines. The study showed a sensitivity rate of 67% for detection of misplaced cobalt-chrome alloy screws and concluded that CT data alone is not sufficient for determining accuracy of 8

11 screw placement in the pedicle. This study was a post surgical evaluation and in lumbar spine, but does demonstrate the difficulties associated with the type of surgical procedure. In addition, the lumbar pedicles are significantly larger compared to cervical pedicles with much fewer essential structures in the immediate vicinity that may be permanently damaged. This study will use CT a pre-planning tool to help minimize the misplacements described by Yoo. A Hangartner et al. (Hangartner 1996) study to determine the minimum thickness of cortical bone required for the accurate measurement of cortical material density by CT. they concluded that the thickness of the cortex must exceed mm to measure material density. The implications for this study from Hangartner are the partial volume averaging associated with measurements of cortical thickness less than mm must be considered and result in an overestimation of cortical thickness. Second, the study was done to simulate appendicular skeleton, hence providing straight cortex with little to no curvature. The measurements were also taken perpendicular to the cortex, again to minimize error and partial volume averaging. Dougherty and Newman (Dougherty 1999) did a modeling study and demonstrated that blurring due to convolution of an image profile with the PSF of a CT scanner is directly responsible for the overestimation of physical thickness and underestimation of the density of thin structures. They show the blurring effect depends on the object profile shape, field of view (FOV) and reconstruction kernel and that it is significant for structures that are smaller than about times the FWHM of the overall point spread function of the CT scanner. They also indicate that thresholding alone will not provide an accurate estimate of the cortical shell thickness. Dougherty and Newman used a titanium wire for the PSF and a modeled a Gaussian shape to simulate the cortex. This study will use 9

12 cadaveric spines. Newman et al. (Newman 1998) demonstrated with their study that above 3 mm thickness peak CT number and FWHM are independent of both FOV and algorithm. Below 3 mm peak CT number fall progressively and FWHM remains constant. The study used aluminum sheets to simulate cortical thickness and care was taken to be perpendicular to the sheets to minimize partial volume averaging. Again, this study will use cervical spine cadaver specimens. Smith et al. (Smith 1993) measured vertebral foraminal dimensions using 3D CT and found the measurements underestimated the true foraminal dimensions. The authors conclude 3D CT is not recommended for measurement of foraminal dimension but indicate it may be an adjunct in assessment and planning surgical management. Smith use only conventional axial images and 3D reconstructions whereas this study will use sagittal and coronal reconstructions as well as oblique reconstructions in addition to conventional axial images. Ahlqvist and Isberg (Ahlqvist 1993) used temporomandibular joints assessed by CT found that partial volume averaging effects can result in an overestimation of bone dimensions amounting to 200% for thin bones. Previous studies quoted above demonstrate that small structures, particularly less than 2-3 mm thickness, will be overestimated in size by up to two hundred percent and measurements are influenced by algorithm, field of view, threshold, partial volume averaging and system PSF. These factors all come into play when the cervical spine is imaged by CT, since the structures are small, use small field of view, which further emphasizes partial volume effects, and choice of algorithm. The following objectives are then formulated for this study. 10

13 OBJECTIVES 1. Measure the size and angulations of the cervical vertebra as depicted on CT images such as lamina length, lamina angle, lateral mass vertical height and horizontal width, facet angle, pedicle length and width, pedicle angle, A-P and left to right dimension of vertebral body. 2. Measure the size and angulations of the cervical vertebra morphologically. 3. Measure and evaluate methods of determining cortical width of structures in the cervical spine. 4. Determine the relative difference d r between the true distance d t and measured distance d m and dependence on slice thickness, imaging algorithm and angulation of structure. 5. Determine the utility of axial and reformatted CT images and if they can help in the choice of surgical hardware such as length and width. Determine if CT reformatted images can accurately depict the exact location, angulation and depth to be used during a surgical procedure. Specifically can a CT reformatted image accurately depict the entrance hole for lateral mass or pedicle insertion? 6. Evaluate the cortical and trabecular pattern of the vertebral body and determine the optimal path and angulation for surgical screws for anterior instrumentation. 7. Evaluate the effect of smoothing, sharpening and thresholding on the CT anatomy and effect on reformatted images. 8. Correlate data obtained in this study with data available in the literature. 11

14 LITERATURE Morphology Of The Cervical Spine Panjabi et al. (Panjabi 1993) assessed human articular facets from C2 through L5 on 12 human cadaver spines. The study quantifies a number of parameters for articular facets including linear measurements of height, width, interfacet height and interfacet width; facet surface area; and facet orientation in sagital and transverse planes. This comprehensive data set separate the cervical spine articular facets into three regions, C2, C3-C4 and C5-C7, each region demonstrate distinct orientation of the facet angle about the y-axis, actually reversing direction at C2-3 and C4-5. one additional site of reversal in direction noted at T12-L1. another feature noted about the cervical spine from this study is the ratio of interfacet width to height was above 1.5, a particular characteristic of the cervical spine. Bailey et al. (Bailey 1995) analyzed the anatomic relationships of the cervicothoracic junction from sections approximately 5 mm thick. This detailed study measured morphology of the cervicothoracic junction vertebrae, including lamina thickness, pedicle width and axial thickness, lateral mass or transverse process intervertebral foramen thickness, vertebral body sagital diameter and vertebral body coronal diameter. The study also include distances from key spine bony structures to essential soft tissue structures, such as spinal cord, dura mater, vertebral artery and spinal nerve and ganglia. The study demonstrates consistent and predictable patterns in bony and soft tissue anatomy size and orientation, but also indicates that variation in size and orientation can vary from side to side and segment to segment. 12

15 Ebraheim et al. (Ebraheim 1998) evaluated the cervical nerve root groove and intervertebral foramen using dry bony vertebrae and cadaveric cervical spine segments. The study defines three zones of the nerve root groove, medial, middle and lateral with the medial zone being very important in its role in the etiology of cervical radiculopathy. Little difference between genders was noted. The range of measurement differential varied from 2 to 10 mm with standard deviations of about mm. the study demonstrated predictable patterns in a cranio-caudad direction, again varying from segment to segment. Side to side comparison not reported. Xu (Xu 1999) reported the dimensions of the lateral mass and the relationship of the lateral mass to the adjacent nerve roots. Second phase determined if a too long screw could be detected radiographically. The height, width and depth of the lateral mass from dry vertebrae and relationship of the dorsal ramus and the superior articular facet identified. Author concluded that preoperative radiographs and CT scan should be routinely obtained due to anatomic variation between individuals and that the dorsal ramus may be at greater risk on injury for the Magerl and Anderson techniques than for the Roy-Camille and An techniques for posterior plating procedures. Ebraheim et al. (Ebraheim 1997) performed a morphological analysis of the pedicle in the lower cervical spine measuring dimensions height, width, effective length and angle with the transverse process and sagital angle. Location of the entrance point on the posterolateral lateral mass identified. The study concluded that individual variation 13

16 between individuals exist as well as between segments and that preoperative CT scans and radiographs be obtained to enhance safety of the procedure. Kameyama et al. (Kameyama 1994) measured transverse area and diameters of the spinal cord and found considerable individual variation in spinal cord size. Karaikovic et al. (Karaikovic 1997) detailed morphological characteristics of cervical pedicles using cervical spine C2-C7 followed by CT scanning of the segments. measurements included width, height and length, lateral mass-pedicle length and similar measurements on the CT scans. Conclusions by the authors include CT measurements of pedicles are accurate and valuable for preplanning, that the pedicles are not uniformly sized, variations between segments exist that would necessitate carefully selection of screws for fixation and that individual height may correlate better with pedicle height than gender. One major detractor for this study was the authors inability to cut specimens for detailed measures due to agreement with curators. Ebraheim et al. (Ebraheim 1996) studied the anatomic relationship between the vertebral artery foramen and the posterior midpoint of the lateral mass. The distance and angle from the midpoint to the vertebral artery foramen were noted and results indicated some variation from male to female. Conclusion of the study indicate that a screw placed perpendicular to the posterior aspect of the lateral mass at C3-C5 and 10 degree lateral to sagital plane at C6 starting at midpoint of the lateral mass would result in no risk to the vertebral artery during posterior plating procedure. 14

17 Ebraheim et al. (Ebraheim 1999) did a quantitative evaluation of the cervical facet and the projection of the inferior facet on the posterior aspect of the lateral mass relative to screw placement. The study found that variations between male and female exist and segment to segment. The authors conclude that a screw might be a great risk of violating the inferior facet joint if the screw placement is starting at the midpoint or below the midpoint of the lateral mass and directed perpendicular to the posterior aspect of the lateral mass at C3-C7. Ebraheim (Ebraheim 1999) provides and review of and details the five separate techniques for posterior lateral mass fixation and relationship of anatomy of the cervical spine. In this review some the previous literature mentioned above is reviewed along with a detailed description of insertion techniques for posterior lateral mass screws according to each technique. The essential soft tissue anatomy at risk is described. The author conclude that preoperative CT scans and radiographs should be obtained and evaluated due to individual variation along with meticulous surgical technique. Computed Tomography Hangartner and Gilsanz (Hangartner 1996) undertook a study to determine the minimum thickness of cortical bone required for the accurate measurement of cortical material density by computed tomography. A phantom with several wall thicknesses of bone like material was used to simulate various cortical widths. The CT density was measured at 15

18 each thickness and minimum with required to attain correct material density was determined for each scanner used. The minimum thickness necessary for accurate density evaluation of the walls of the phantom by CT was mm. Below this threshold the values fall linearly relative to width and the influence of partial volume averaging must be considered. This study was done to simulate appendicular cortical bone. Dougherty and Newman (Dougherty 1999) did a simulation study that experimentally determined point spread functions with the rectangular and Gaussian profiles, full various fields of view and reconstruction algorithms. The authors conclude that the simulations indicate that in order to accurately measure the thickness and density the minimum thickness of cortical bone should be times the system full width at half maximum. This corresponds to a thickness between 1.5 and 3 mm depending on reconstruction algorithms and field of view. The blurring effect due to convolution with PSF of a CT scanner is directly responsible for the overestimation of physical thickness and underestimation of the density of thin structures. Newman et al. (Newman 1998) demonstrated with their study that above 3 mm thickness peak CT number and FWHM are independent of both FOV and algorithm. Below 3 mm peak CT number fall progressively and FWHM remains constant. The study used aluminum sheets to simulate cortical thickness and care was taken to be perpendicular to the sheets to minimize partial volume averaging. At small thicknesses the effect of FOV 16

19 on peak CT number is more pronounced when bone algorithms is used while FWHM remains relatively constant and independent of both FOV and algorithm. Smith et al. (Smith 1993) measured dimensions of lumbar intervertebral foramina in cadaver spines using three-dimensional computerized tomography. Six different image reconstruction protocols were used in results were compared with measurements of the same foramina using calibers after dissection. All 3-D CT measurements underestimated the true foraminal dimensions. The authors conclude three-dimensional CT measurements may not be accurate enough to determine foraminal dimensions however a may play a role in assessment of surgical planning. Ahlqvist and Isberg (Ahlqvist 1998) studied the CT depiction of bone in the temporomandibular joint using conventional window level and window width to estimate bone thickness in these images. Specimens were imaged by CT and then cryosectioned. The measurements all bone wall thickness in the images were compared to the true bone thickness. The relative difference between CT reproduction and true bone thickness was small full walls thicker than 2 mm. The difference between CT reproduction and true wall thickness increased with a decreasing bone thickness and increase in the inclination of the bone wall from perpendicular to the imaging plane. Bone walls thicker than 1 mm were produced with an overestimation of bone dimensions and monitoring to approximately 200% due to partial volume averaging. 17

20 Goodenough et al. (Goodenough 1982) demonstrated theoretically and experimentally that simple volume averaging leads to significant errors in CT attenuation values for mixtures of high and low density materials such as bone with tissue, particularly when they are distributed in thin flat structures. Diederichs et al. (Diederichs 1996) did a study evaluating blurring of vessels in spiral CT angiography and the effect of collimation with pitch and windowing. Conclusions from this study relating to the present study include use of thin sections to minimize partial volume averaging and using appropriate window levels. 18

21 METHODS: Five sectional spine cadaver specimens, including segments C2 through T2, from the Medical College of Ohio (MCO) anatomy department, were utilized for this study. Each section had skin, subcutaneous fat, trachea, esophagus and extra-spinal vasculature removed. The paravertebral muscle, ligaments, tendons, capsules, spinal cord and dura mater as well as spinal nerves were left in place for imaging. Each cervical spine section were scanned in the MCO radiology department computed tomography (CT) scanner (General Electric (GE) Highspeed CT scanner, Milwaukee, Wisconsin) using several protocols. The first protocol is the standard protocol for cervical spine. The spine segments were placed on wax block on the CT table and aligned in the gantry with the CT laser alignment system, with the horizontal axis passing through the anterior spinal canal for the middle segments and posterior body margin for the upper cervical and upper thoracic segments. The scanogram in the sagittal and coronal plane was accomplished and the C2 segment and T2 segments identified. The prescription was set from the inferior aspect of C2 vertebral body, to include the superior elements of the C3 posterior arch, through the superior aspect of T2 vertebral body, if available, or 3 mm inferior to the T1 disc, if T2 vertebral body not available. The scan parameters were set as follows. Helical mode scanning 3 x 3 mm (slice thickness of 3 mm with slice spacing of 3 mm) in standard algorithm utilizing 120 kvp, 220 ma and scanning field of view (FOV) of 25 cm. the standard matrix size of 512 x 512 was assigned. While the original raw data was still in the CT computer, reconstruction in bone algorithm and detail algorithm were performed. All the data were stored on DAT tape for permanent storage. The data were also sent via MCO network to the GE workstation in the radiology department film 19

22 reading area. From the GE workstation, the data were transferred to the medical physics computer laboratory via the MCO network. The data was stored in standard DICOM format as obtained from the CT scanner to preserve the original header information, matrix and voxel data. Sections were scanned using a second protocol, similar to the first protocol, differing only in the slice thickness and slice spacing. The new slice thickness was 1 mm and slice spacing 1 mm, i.e. 1 x 1 mm helical scanning. The protocol again called for scanning in standard algorithm, followed by reconstruction in bone algorithm from the original data. The original data for this set was also utilized to reconstruct to a 0.5 mm slice thickness in standard and bone algorithms. Again, the data was transferred to the GE workstation as well as to the medical physics computer laboratory via the MCO network. During the time of this study, the department obtained a new CT scanner (Toshiba Aquilion). This CT scanner is a 16 slice, multi-detector CT scanner, capable of obtaining a large quantity of high resolution data within a short period of time. The Aquilion is capable of isotropic voxel size, meaning all sides of the voxel are identical in size. This feature allows for reconstruction in planes other than the imaging plane (axial) without loss of information or resolution seen previously. The third protocol utilize the Aquilion CT scanner in helical mode. The spine section set up is identical to the protocol one and two, with the spine section place on a wax block. A scanogram is obtained and the slice prescription done in a similar fashion to the GE 20

23 Lightspeed and described in protocol one. The scan mode is helical, no gantry tilt, 0.5 mm slice thickness and 0.5 mm slice spacing, i.e. 0.5 x 0.5 mm scanning, in standard algorithm. With the original raw data in the computer, reconstruction in bone and detail algorithms and sagittal and coronal imaging planes was done. The image data were transferred to and stored on the medical physics laboratory computer. The image data were transferred from the medical physics laboratory computers to a number of CD-ROMs for easier evaluation off site. The spine section were taken to the MCO anatomy department for disarticulation of the segments, morphological analysis and further sectioning. The muscles, ligaments, tendons capsules were removed by blunt dissection. The disc annuli were transected, thereby disarticulating the segments. Morphological measurements of the individual vertebrae were made, see below for details. The individual segments were then chosen at random to be sectioned through the vertebral body, pedicle, lateral mass, lamina or midline. The sectioning of the segments was done utilizing the anatomy department diamond blade cutter. This particular device only cuts away about 0.5 mm of tissue, which is acceptable for the purposes of this study. The cut segments were photographed with a reference ruler and measured utilizing ImageJ software from NIH. The measurements on the images were made utilizing the GE workstation for protocol 1 and 2 and Aquilion workstation for protocol 3. All images were then measured using a 21

24 publicly available program from the National Institutes of Health, named ImageJ and VolumeJ. Measurements were also made in a program called E-film from Merge-Efilm. Measurement were made using the curser placement tool depositing the curser at beginning of measurement and second curser at end measurement; simple line measurement tool, which measure the length of the line but also provide a profile of the voxel values along the line; and angle measures where three points are selected and the angle between them given. The following definitions apply to all measures, both on images and morphological. Lamina length: distance from the spinolaminar junction, or visually where the two laminae join together. Lamina width: the width of the lamina, from outside cortex to inside cortex (including the cortex) about mid-lamina. Lateral mass horizontal width: from the junction of the lamina with the lateral mass to the lateral aspect of the lateral mass. Lateral mass vertical dimension: from the superior most aspect of the lateral mass to the inferior most aspect of the lateral mass measured posteriorly. Lateral mass depth dimension: measured from the outside of the posterior cortex to the outside of the anterior cortex. length: from the origin on the lateral mass to the insertion on the posterolateral vertebral body. width: from the outside cortex to the inside cortex (including the cortex). 22

25 Spinal canal sagittal dimension: from the posterior outside cortex of the vertebral body to the junction of the laminae. Spinal canal transverse dimension: from the medial aspect of the facet articulation right to left. Intervertebral foramen vertical dimension: from the cortex of the pedicle above to the cortex of the pedicle below. Intervertebral foramen width: from the cortex of the posterior aspect of the vertebral body to the cortex of the anterior lateral mass. Cortical width is measured from the outside to the inside of the cortex. The cortical width of the anterior vertebral body cortex; posterior vertebral body cortex; lateral mass anterior cortex; lateral mass posterior cortex; pedicle cortex medial/lateral and superior/inferior; lamina medial and lateral cortex. Lamina angle: the lateral projection of the lamina from the sagittal plane. angle: the medial/lateral projection of the pedicle from the sagittal plane. The effects of smoothing algorithms on the images were measured. In particular, the effect on smaller structures, such as lamina width, pedicle width, cortical width and lateral mass dimensions. The smoothing algorithm selected is the standard supplied with ImageJ. To better visualize the smooth effect on the structures, magnification of the images using the ImageJ zoom tool was accomplished. 23

26 The effects of sharpening on the same structures were then similarly done, again with image zoom to better see the effect on the small structures. Again, the smoothing algorithm was the standard supplied with ImageJ. The effect of thresholding on the structures was then evaluated. Eight different threshold levels were selected (four lower threshold and four upper threshold) and the effects on images and small structures again evaluated. The threshold levels selected were variably selected at 79 HU (HU = Hounsfield Unit); 157 HU, 303 and 482 HU for lower threshold limits and 1997 HU, 2300 HU, 2502 HU and 2805 HU for upper threshold limits. Using image zoom measurements of small structures using line measuring tool measuring from pixel representing an edge of structure to pixel representing other dimension of structure. These measurements are compared to linear measurements made without magnification. Measurements are made along paths that screws would be inserted. Using a reconstructed image of the posterior lateral mass the entrance point for insertion of screw is determined and compared to physical measurement on the vertebra. Insertion point for pedicle screw insertion is also noted and compared to physical measures. 24

27 RESULTS Measurements for the AP vertebral body midline dimension on the respective CT images are done at the level where both pedicles are in the imaging plane. This corresponds approximately to the middle third of the vertebral body, a portion of the vertebral body that has very thin or minimal cortical margin. (Figure 1) Figure 1. A representative CT image demonstrating the region of measurement for the AP midline vertebral body measurement, AP vertebral body measurement 1 cm lateral to midline and AP and R-L canal dimensions. 25

28 Some degree of image magnification was necessary to ensure the measurement placements were accurate in respect to the cortical margin. The average vertebral body AP dimension increases in size progressively inferior from 15.4 mm at C3 to 17.4 mm at C7. The standard variation increases by almost 2 mm from C5 to C7 indicating the greater degree of size range in this region from specimen to specimen. The measurements for each specimen do not vary more than 2-3 mm from C3 to C7, except specimen D, which varies almost 8 mm from C3 to C7. Measurements of the anatomic sections demonstrate good correlation with CT measurements. There is approximately mm difference between the CT measurements and the measurements on the specimens. This might be accounted for by the placement of measurements on the specimens. (Figure 2; Tables A1; A66; A68; Figure B1a and b) Figure 2. One of the specimens cut at the approximate level corresponding to the CT scan images. 26

29 The AP parasagittal measurement 1 cm from midline demonstrates a smaller dimension compared to the midline measurement. The variation ranges from 12.2 mm for specimen C to 19.4 mm for specimen D and when comparing segments C3, C4 and C5, they demonstrate almost 2 mm variance with less variance of approximately 1 mm for C6 and C7. (Tables A2; A68) Measurements of the central spinal canal were made in the AP dimension and the right to left dimension between the medial aspect of the facet articulations. There is a range of measurements with the smallest AP dimension being specimen C at 13.8 mm and the largest dimension being specimen D with 17.0 mm. Averaging segmental levels the largest AP dimension is at C3 with C4 through C7 varying only approximately 0.5 mm. The right to left dimension variation is from 20.2 mm for specimen D to 27.4 mm for specimen B. The segments vary with the smallest right to left dimension at C3 and less variation of C4 through C7 with C5 and C6 being the largest dimensions. Comparing CT measurements to the physical specimen measurements there is again in good correlation within 1 mm, which again could be accounted for by the placements of the measurement on physical specimens. (Tables A3; A4; A67; A68) Measurements on the pedicles were made at three different locations for height and width. First location is at the body pedicle junction, second location is mid pedicle and third location is in pedicle lateral mass junction. The measurements demonstrate the pedicle is larger at the vertebral body pedicle junction and lateral mass pedicle junction and the smallest at the center of the pedicle. The variation of segments between the 27

30 midline and other two measurements is between 0.5 mm-1.0 mm. There is variation in size between right and left side by almost 1.0 mm. This finding appears to be consistent on all of the specimens. The pedicle length appears to be approximately the same on all specimens and all levels varying 0.6 mm or less, however again with variation between right and left side. The pedicle angle is the angle between the sagittal plane and the pedicle. The angle appear to be larger in the upper cervical spine and less acute progressively inferior in the cervical spine. Again there is some variation between right and left side. Comparing physical specimen measurements with the CT measurements there appears to be good correlation particularly with thinner slice measurements. Variation is approximately less than 0.5 mm. (Tables A5-A25; A68) The lateral mass was measured in multiple dimensions inclusive of the height posteriorly measured from the edge of the superior facet to the edge of the inferior facet, the AP dimension of the lateral mass in the sagittal plane as well as the width of the lateral mass. The vertical height varies very little when averaging segments, only varying from side to sign. However, comparing specimen to specimen there is a much larger degree of variance by approximately 3 mm. The vertical height measurement on the specimens does not correlate as well with the CT measurements varying by almost 2 mm. This may be accounted for by some soft tissue still been present on the specimens resulting in larger physical specimen measurements. The magnification available on the CT from measurements may also help in a more accurate measurement. The depth of the pedicle increases slightly from C3 through C7 when averaging segments for the specimens but varies greatly when looking between different specimens. Comparing physical 28

31 measurements on specimens with CT measurements the physical measurements again appear to exceed by almost 2 mm the CT measurements. Again soft tissue on the specimens appears in part to contribute. The pedicle width is largest in the mid-cervical spine and smallest in the upper cervical region with an intermediate measurement in the lower cervical region. Again a variation between right and left side is demonstrated more prominent in the upper and lower and with less variation in the center of the spine. Again a large variance between specimens exists. Measurements on physical specimens compared with the CT measurements demonstrate good correlation within 1 mm. This measurement compared to depth and height was less influenced by soft tissue on the side and posterior aspect of the lateral mass. (Tables A26-A31; A69) The lamina appears to be largest at the C3 level with smaller and less variation for the remaining segments. Right to left variation exists by almost 1.0 mm and specimen to specimen variation of almost 4 mm. Measurements on physical specimens compared to CT measurements demonstrate variation of less than 2 mm. This variation in parts was due to soft tissues around the lamina lateral mass region interfering with accurate measurement and possibly over estimation of the junction as well as a less precise location for the spinolamina junction on physical specimen compared to a much defined location on CT images. The width of the lamina appears to be consistent comparing specimen to specimen and segment to segment averages. The lamina width is larger in the upper and lower cervical area and smaller in the mid cervical region. The variation is from 2.6 mm in the mid cervical spine at C5 to 5.4 mm at C7. Comparing physical specimens to CT images there is a very good correlation with less then 0.3 mm variation. 29

32 The angulation of the lamina measures between 50 and 56 with a minor variation from side to side. Looking at individual segment averaging the upper cervical area shows the larger measurements with smaller measurements in the lower cervical region. Comparing physical specimens to the CT measurements there is a reasonable approximation with about 2 variation. This may be accounted for by the placement of the measurement tool. (Tables A32-A37; A69) Measurements to simulate the screw path for three representative surgical fixation techniques inclusive of Roy-Camille, Magerl and An approaches were measured. For the Roy-Camille measurement there is a slight increase in size from C3 through C7 by 1-2 millimeters with variation from side to side by 1 mm. The Magerl measurements are larger than the Roy-Camille measurements by 3-5 millimeters and likewise demonstrate an increasingly larger dimension from superior to inferior with variation from side to side up to 2 mm. The An measurements were between Roy-Camille and Magerl measurements showing less variation in size from superior to inferior than the Magerl technique but greater than the Roy-Camille technique. Variation from side to side less than 1 mm noted. Correlation of physical specimen measurements with CT measurements demonstrate the physical measurements to be slightly larger for several of the specimens due to the inability to determine where the cortex on the anterior surface of the lateral mass was located and the previously mentioned soft tissues attached. One cut specimen along the plane of the Magerl and Roy-Camille techniques demonstrate measurements on physical specimen that correlate to less than 0.3 mm. (Figure 3) 30

33 Figure 3. Specimen demonstrating the cut planes of the Roy-Camille and Magerl techniques. Thinner CT slices appears to correlate better than larger CT slices. (Tables A38-A43; A69) Intervertebral foramina height appears to be consistent within 1 mm for all segments with minimal variation from side to side. The width of the intervertebral foramen increases slightly in size in the lower cervical region but demonstrates only minor variation from side to side. Comparing each specimen one with another right to left side appears to demonstrate greater variation in size. (Tables A44; A45; A70) Comparison is made between the older standard technique performed on the GE using 3 mm slice thickness and the new Toshiba standard technique using 0.5 mm slice thickness. 31

34 AP vertebral body measurements the small slice thickness demonstrates a larger measurement by 1.6 mm. (table A51) Measurements along the surgical approach planes show that there is a small increase in size for thinner slice thicknesses for the Roy-Camille measurements and An measurements but a smaller average size for thinner slices compared to thicker slices for the Magerl measurements. This is consistent from side to side. (Table A52-A57) Comparing the intervertebral foramen height between thick and thin slices demonstrate no consistent pattern, one section showing no measured size difference, one demonstrating thinner slices yielding larger measurements yet another showing thinner slices yielding smaller measurements. The intervertebral foramen width demonstrates increased size on thinner slices consistently. (Table A58-A61) Measurements on the CT scans of the lateral mass width were made on both axial and coronal images. The coronal images demonstrate a 3 mm larger average size of the lateral mass width compared to axial images. Similar measurements were also made on the lamina width again demonstrating a larger width on the coronal images by up to 22 mm. (Table A62-A65) A simple theoretical calculation of CT numbers was performed using five different mixtures of bone, water and fat. Water and fat adequately represent soft tissue structures that surround the osseous structures of the cervical spine and allow a simple 32

35 approximation for the purposes of this study. The five mixtures were as follows: bone and water; bone and fat; bone and mix of water-fat; bone and mix of waterfat; and bone and mix all water-fat. For each mixture there are 12 mixes varying the percentage of bone within the voxel. The mixtures were calculated at three separate effective kev levels: 60, 80 and 100. The results demonstrate that higher CT numbers are generated at effective 60 kev, intermediate CT numbers generated at effective 80 kev and the lowest CT numbers generated at 100 effective kev for each mixture. When comparing mixtures at one effective kev there is less variation in higher percentage of bone present within the voxel. The typical effective energy for a CT x-ray beam is between 60 and 80 kev for 120 kvp beams. The variation at lower percentage of bone within the voxel is greater and appears to depend on the amount of fat within the voxel. It appears consistently that a 20% mix of bone within the voxel results in a CT number high enough to be identified as bone and result in partial volume averaging. (Tables A71-A75; Figures A1-A13) Several limited data sets obtained at one vertebral level using a 1 mm slice thickness were obtained. The technical parameters of image algorithm, kvp, mas and pitch were varied one parameter at a time with all other parameters remaining unchanged. Measurements of midline AP vertebral body, mid pedicle width and mid lamina width on all data sets were obtained. The results demonstrate that varying the kvp influences the CT number. At 80 kvp there appears to be an overestimation of cortical width due to higher average CT numbers compared to 120 kvp. Varying the mas for a small structure 33

36 like the cervical spine does not appear to influence the measurements, algorithm or processing. (Figures B1-B21) Comparing the various algorithms it appears that the detail and standard algorithms appear statistically identical at 80 kvp but various slightly from the bone algorithm. At 120 kvp the algorithm profiles vary slightly at upper and lower boundaries however at the midpoint of the graph they appear statistically identical. This would be the region of the graph used for measurement (full width half max). (Figures C19-C2-3) Comparing the slices using a pitch of one to the slices using a pitch of two demonstrate a slight widening of the profile for the larger pitch. (Figure B25) The effects of image processing on the limited data sets were assessed in each algorithm. The image processing include: smoothing 1X; smoothing 2X; sharpening 1X; sharpening 2X; Gaussian blur two pixels; Gaussian blur four pixels; and unsharp mask. Specific measurements are made of the identical row of pixels in all images starting at the same pixel location in each image and ending at the same pixel location in each image. Effects of smoothing were readily visible on bone and detail algorithms and less pronounced on the standard or soft tissue algorithm. Multiple levels of smoothing further enhanced the results of the initial smoothing. The effects of sharpening result in a greater distinction between bone and soft tissue and are readily visible on all image algorithms. Sharpening multiple times result in further enhancement of the effect. Gaussian blur demonstrate 34

37 similar findings as smoothing with equal weighting. Unsharp mask demonstrate identical findings to sharpening. (Figures C1-C8; C24-C36) A single image was selected to evaluate the effects of threshold. Thresholds were selected as an upper and lower limit. Lower threshold include: 79, 157, 303 and 482 Hounsfield units. Upper threshold include: 1997, 2300, 2502 and 2805 Hounsfield units. Comparing the images it appears that a lower threshold of 482 and Upper threshold of 1997 results in the greatest depiction of cortical margins and outline of structure. (Figure C10-C18) 35

38 CONCLUSIONS: The following are conclusions regarding the utilization of CT scanning as a useful method for presurgical evaluation of the cervical spine osseous structures. 1. CT is useful for morphological evaluation of osseous structures in the cervical spine. It demonstrates adequately the relationship of osseous structures to essential neurovascular structures. 2. In order to avoid overestimation of size, particularly of small structures, and to minimize the effect of partial volume averaging, small slice thickness should be utilized. 3. Partial volume averaging exhibit a large effect on thicker slices resulting in either over or under estimation of morphology. Partial volume averaging presents particular problems on multiplanar reconstruction of smaller anatomical structures, such as the pedicle. Partial volume averaging also resulted in an overestimation of the screw path length on the Magerl technique. This could result in overpenetration of cortex and possible insults to neurovascular structures. 4. The profile tool appears to be more accurate in its assessment of size and length compared to measurements made with pure observation. 5. A higher kvp technique is appropriate. The mas did not seem to affect the image profile and can be lowered without detrimental effects to image quality and improvement in patient dose. 6. Multiplanar reformatted images in the plane of the structure being investigated are very useful. Sagittal and coronal images may be less useful for measurements and 47

39 assessment for presurgical planning due to overestimation of structure size from partial volume averaging % bone by volume within the voxel result in identification as bone by CT numbers alone and appear to contribute to partial volume averaging and overestimation of size of morphology. 8. Filtering techniques affects the appearance of the image and may enhance multiplanar reconstruction images and accuracy of measurements on these images. 9. The choice of algorithm for imaging osseous anatomy should be the bone algorithm. The soft tissue or standard algorithm results in an overestimation of size. 48

40 References Ahlqvist J.B. and Isberg A.M Bone Demarcation of the Temporomandibular Joint. Acta Radiologica, Vol An HS, Gordin R, Renner K: Anatomic Considerations for Screw-Plate Fixation of the Cervical Spine. Spine, Vol 16 supplement, Anderson PA, Henley MB, Grady MS: Posterior Cervical Arthrodesis with AO Reconstruction Plates and Bone Graft. Spine, Vol 16 supplement, 1991 Bailey AS, Stanescu S, Yeasting R, Ebraheim, NA, Jackson WT: Anatomic Relationships of the Cervicothoracic Junction. Spine, Vol 20, No 13, Diederichs C. G; Keating D. P.; Glatting G.; Oestmann J.W. Blurring of Vessels in Spiral CT angiography: Effects of Collimation Width, Pitch, Viewing Plane, and Windowing in Maximum Intensity Projection. J. Comput. Assist. Tommogr., Vol 20, No Dougherty G. and Newman D. Measurement of Thickness and Density of Thin Structures by Computed Tomography: A Simulation Study. Med Phys, Vol 26, No Ebraheim NA, An HS, Xu R, Ahmad M, Yeasting R: The Quantitative Anatomy of the Cervical Nerve Root Groove and the Intervertebral Foramen. Spine, Jul 15; Vol 21, No

41 Ebraheim NA, Xu R, Knight T, Yeasting R: Spine, Vol 22, No 1, Ebraheim NA, Xu R, Yeasting R: The Location of the Vertebral Artery Foramen and Its Relations to Posterior Lateral Mass Screw Fixation. Spine, Jun 1; Vol 21, No Ebraheim NA, Xu R, Challgren E, Yeasting R: The Quantitative Anatomy of the Cervical Facet and the Posterior Projection of Its Inferior Facet. J Spinal Disord, Aug; Vol 10, No Ebraheim NA: Posterior Lateral Mass Screw Fixation: Anatomic and Radiographic Considerations. Ortho J, Vol 12, Spring Flanders AE, Tartaglino LM, Friedman DP, Aquiolone LF: Magnetic Resonance Imaging in Acute Spinal Injury. Seminars in Roentgenology, Vol XXVII, No 4, 1992 Goodenough D; Weaver K.; Davis D.; LaFalce S Volume Averaging Limitations of Computed Tomography. AJR vol 138. Hangartner T.N. and Gilsanz V Evaluation of Cortical Bone by Computed Tomography. J. Bone and Mineral Research vol 11, no 10. Huckell, CB: Clinical Outcomes after Cervical Spine Fusion. Simmons Orthopedic and Spine Associates, LLP Physician Literature web site. 50

42 alspine.html Kameyama T, Hashizume Y, Ando T, Takahashi A: Morphometry of the Normal Cadeveric Cervical Spinal Cord. Spine, Vol 19, No Kaplan A, Gentili A: Review of Radiologic Findgins Associated with Complications of Cervical Spine Fixation Surgery. RSNA Educations Exhibits, Nov, Karaikovic EE, Daubs MD, Madsen RW, Gaines RW: Morphologic Characteristics of Human Cervical s. Spine Vol 22, No 5, 1997 Laxer EB, Aebi M: Management of Subaxial Cervical Spine Injuries with Internal Fixation: The Anterior Approach. Seminars in Spine Surgery, Vol 8 No 1, 1996 Lufkin RB: The MRI Manual. Year Book Medical Publishers Newman D.L; Dougherty G; Al Obaid A.; Al Hajrasy H. Limitations of Clinical CT in Assessing Cortical Thickness. Phys. Med. Biol. Vol Panjabi MM, Oxlnad T, Takata K, Goel V, Duranceau J, Krag M: Articular Facets of the Hunan Spine. Spine Vol 18, No 10,

43 Smith G.A.; Aspden R.M.; Porter R.W.; Meaasurement of Vertebral Foraminal Dimensions Using Tgree-Dimensional Computerized Tomography. Spine vol 18, no Xu R: Anatomic and Radiologic Considerations of Lateral Screw Placement for Posterior Cervical Plating. Spine, Oct 1; Vol 24, No Yoo, J.U.; Ghanayem A.; Petersilge C.; Lewin J. Accuracy of Using Computed Tomography t Identify Pedicel Screw Placement in Cadaveric Human Lumbar Spine. Spine Vol 22, No

44 APPENDIX The appendix is divided into multiple sections. Appendix A is a tabular and graphic format of image measurements. Appendix B consists of images with associated pixel profile and appendix C demonstrates images with differences of a variety of imaging factors and image processing. All measurements are in millimeters. Table A1: Anterior To Posterior Vertebral Body Dimension in mm at Midline. Table A2: Anterior To Posterior Vertebral Body Dimension in mm, Measured 1 mm Lateral to Midline. Table A3: Spinal Canal Anterior To Posterior Dimension in mm at Midline. Table A4: Spinal Canal Right to Left Dimension in mm, Measured Between the Medial Aspect of the Facet Articulation. Table A5: Width at -Body Junction, Right Side. Table A6: Width at -Body Junction, Left Side. Table A7: Width at Mid-, Right Side. Table A8: Width at Mid-, Left Side. Table A9: Width at -Lateral Mass Junction, Right Side. Table A10: Width at -Lateral Mass Junction, Right Side. Table A11: Length, Right Side. Table A12: Length, Left Side. Table A13: Height at -Body Junction, Right Side. Table A14: Height at -Body Junction, Left Side. Table A15: Height at Mid-, Right Side. Table A16: Height at Mid-, Left Side. Table A17: Height at -Lateral Mass Junction, Right Side. Table A18: Height at Lateral Mass Junction, Left Side. Table A19: C3 Measurements of the. Table A20: C4 Measurements of the. Table A21: C5 Measurements of the. Table A22: C6 Measurements of the. Table A23: C7 Measurements of the. Table A24: Angle from Midline, Right Side. Table A25: Angle from Midline, Left Side. Table A26: Lateral Mass Height, Right Side. Table A27: Lateral Mass Height, Left Side. Table A28: Lateral Mass Depth Measured On Axial Projection, Right Side. Table A29: Lateral Mass Depth Measured On Axial Projection, Left Side. Table A30: Lateral Mass Width Measured On Axial Projection, Right Side. Table A31: Lateral Mass Width Measured On Axial Projection, Left Side. 53

45 Table A32: Lamina Length, Right Side. Table A33: Lamina Length, Left Side. Table A34: Lamina Width Measured On Axial Projection, Right Side. Table A35: Lamina Width Measured On Axial Projection, Left Side. Table A36: Lamina Angle from Midline, Right Side. Table A37 Lamina Angle from Midline, Left Side. Table A38: Lateral Mass Measurement for Roy-Camille Technique, Right Side. Table A39: Lateral Mass Measurement for Roy-Camille Technique, Left Side. Table A40: Lateral Mass Measurement for Magerl Technique, Right Side. Table A41: Lateral Mass Measurement for Magerl Technique, Left Side. Table A42: Lateral Mass Measurement for An Technique, Right Side. Table A43: Lateral Mass Measurement for An Technique, Left Side. Table A44: Intervertebral Foramen, Right Side. Table A45: Intervertebral Foramen, Left Side. Table A46: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle. Table A47: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle. Table A48: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle. Table A49: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle. Table A50: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle. Table A51: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to anterior to posterior vertebral body dimension at midline. Table A52: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right lateral mass for Roy-Camille technique. Table A53: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right lateral mass for Magerl technique. Table A54: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right lateral mass for An technique. Table A55: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to left lateral mass for Roy-Camille technique. 54

46 Table A56: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to left lateral mass for Magerl technique. Table A57: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to left lateral mass for An technique. Table A58: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen height, right side. Table A59: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen height, left side. Table A60: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen width, right side. Table A61: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen width, left side. Table A62: Comparison of axial and coronal measurements of the lateral mass, right side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation. Table A63: Comparison of axial and coronal measurements of the lateral mass, left side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation. Table A64: Comparison of axial and coronal measurements of the lamina, right side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation. Table A65: Comparison of axial and coronal measurements of the lamina, left side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation. Table A66: Average (Ave) and standard deviation (SD) for AP vertebral body dimension of C3-C7 for each specimen. Table A67: Average (Ave) and standard deviation (SD) for AP canal dimension of C3-C7 for each specimen. Table A68: Statistical summary 1 Table A69: Statistical Summary 2 Table A70: statistical Summary 3 Table A71: Data for effect of partial volume averaging calculation. Bone + water. Table A72: Data for effect of partial volume averaging calculation. Bone + fat. Table A73: Data for effect of partial volume averaging calculation. Bone + 50/50 water/fat mix Table A74: Data for effect of partial volume averaging calculation. Bone + 75/25 water/fat mix Table A75: Data for effect of partial volume averaging calculation. Bone + 25/75 water/fat mix. 55

47 A76. Physical Specimen Measurements. Figure A1. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone, Fat and Water. Figure A2. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone, Fat and Water. Figure A3. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone, Fat and Water. Figure A4. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone and Water. Figure A5. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone and Fat. Figure A6. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 60 kev. Figure A7. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 80 kev. Figure A8. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 100 kev. Figure A9. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 60 kev. Figure A10. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 80 kev. Figure A11 Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 100 kev. Figure A12. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures. Comparison of CT Numbers at 1-20% Bone Figure A13. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures. Comparison of CT Numbers at 10% and 20% Bone. Figure B1a and b. 1 mm slice thickness at 80 kvp and 80 mas, 10 cm DFOV. Figure B2a and b. 1 mm slice thickness at 80 kvp and 200 mas, 10 cm DFOV Figure B3a and b. 1 mm slice thickness at 80- kvp and 300 mas, 10 cm DFOV Figure B4a and b. 1 mm slice thickness at 120 kvp and 80 mas, 10 cm DFOV Figure B5a and b. 1 mm slice thickness at 120 kvp and 200 mas, 10 cm DFOV Figure B6a and b. 1 mm slice thickness at 120 kvp and 280 mas, 10 cm DFOV Figure B7a and b. 1 mm slice thickness at 80 kvp and 80 mas, 10 cm DFOV Figure B8a and b. 1 mm slice thickness at 80 kvp and 200 mas, 10 cm DFOV Figure B9a and b. 1 mm slice thickness at 80 kvp and 300 mas, 10 cm DFOV Figure B10a and b. 1 mm slice thickness at 120 kvp and 80 mas, 10 cm DFOV Figure B11a and b. 1 mm slice thickness at 120 kvp and 200 mas, 10 cm DFOV Figure B12a and b. 1 mm slice thickness at 120 kvp and 280 mas, 10 cm DFOV Figure B13a and b. 1 mm slice thickness at 80 kvp and 80 mas, 10 cm DFOV Figure B14a and b. 1 mm slice thickness at 80 kvp and 300 mas, 10 cm DFOV 56

48 Figure B15a and b. 1 mm slice thickness at 120 kvp and 80 mas, 10 cm DFOV Figure B16a and b. 1 mm slice thickness at 120 kvp and 200 mas, 10 cm DFOV Figure B17a and b. 1 mm slice thickness at 120 kvp and 280 mas, 10 cm DFOV Figure B18a and b. 1 mm slice thickness at 120 kvp and 80 mas, 25 cm DFOV Figure B19a and b. 1 mm slice thickness at 120 kvp and 80 mas, 25 cm DFOV and pitch of 2 Figure B20. Comparison of pedicle measurement profiles at the various technique setting for bone algorhitm. Figure B21. Comparison of lamina measurement profiles at various technique settings for bone algorithm. Figure B22. measurement profile at same technique but different algorithms. Figure B23. Measurement profiles of pedicle width on MPR reconstructions with 0.5 mm slice thickness perpendicular to the pedicle length. Figure B24. Measurement of the intervertebral foramen at C4-5 on MPR reconstruction perpendicular to pedicle length using 0.5 mm slice thickness. Figure B25. Comparison of S with a table pitch of 1 to S with a table pitch of 2. Measurement profile of lamina used. Figure C1. B Original Image Figure C2. B Smoothing 1x Figure C3. B Smoothing 2x Figure C4. B Gaussian Blur Figure C5. B Original Image Figure C6. B Sharpening 1x Figure C7 B Sharpening 2x Figure C8. B Unsharp Mask Figure C9. Threshold level 79 and 1997 Figure C10. Threshold level 79 and 2300 Figure C11. Threshold level 79 and 2502 Figure C12. Threshold level 79 and 2805 Figure C13. Threshold level 157 and 1997 Figure C14. Threshold level 157 and 2502 Figure C15. Threshold level 303 and 1997 Figure C16. Threshold level 303 and 2502 Figure C17. Threshold level 482 and 1997 Figure C18. Threshold level 482 and 2502 Figure C19. Original image comparison BDS Figure C20. Original image comparison BDS Figure C21. Original bone Figure C22. Original detail Figure C23. Original standard Figure C24. Effects of processing B80-80 Figure C25. Effect of smoothing B Figure C26. Effects of sharpening B

49 Figure C27. Effect of blur and unsharp B Figure C28. Comparison of sharp with unsharp B Figure C29. Effects of processing D80-80 Figure C30. Effects of processing D Figure C31. Effects of processing D Figure C32. Effects of processing D Figure C33. Effects of processing S80-80 Figure C34. Effects of processing S80-80 Figure C35. Effects of processing S Figure C36. Effects of processing S

50 Appendix A: Table A1: Anterior To Posterior Vertebral Body Dimension in mm at Midline. C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A2: Anterior To Posterior Vertebral Body Dimension in mm, Measured 10 mm Lateral to Midline. C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

51 Table A3: Spinal Canal Anterior To Posterior Dimension in mm at Midline. Specimen A C3 C4 C5 C6 C Specimen B Specimen C Specimen D Specimen E Table A4: Spinal Canal Right to Left Dimension in mm, Measured Between the Medial Aspect of the Facet Articulation. C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

52 Table A5: Width at -Body Junction, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A6: Width at -Body Junction, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

53 Table A7: Width at Mid-, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A8: Width at Mid-, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

54 Table A9: Width at -Lateral Mass Junction, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A10: Width at -Lateral Mass Junction, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

55 Table A11: Length, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A12: Length, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

56 Table A13: Height at -Body Junction, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A14: Height at -Body Junction, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

57 Table A15: Height at Mid-, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A16: Height at Mid-, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

58 Table A17: Height at -Lateral Mass Junction, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A18: Height at Lateral Mass Junction, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

59 Table A19: C3 Measurements of the. (mm). C3 A B C D E Width 1 R Width 2 R Width 3 R LENGTH R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L LENGTH L Height 1 L Height 2 L Height 3 L

60 Table A20: C4 Measurements of the. (mm). C4 A B C D E Width 1 R Width 2 R Width 3 R LENGTH R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L LENGTH L Height 1 L Height 2 L Height 3 L

61 Table A21: C5 Measurements of the. (mm). C5 A B C D E Width 1 R Width 2 R Width 3 R LENGTH R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L LENGTH L Height 1 L Height 2 L Height 3 L

62 Table A22: C6 Measurements of the. (mm). C6 A B C D E Width 1 R Width 2 R Width 3 R LENGTH R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L LENGTH L Height 1 L Height 2 L Height 3 L

63 Table A23: C7 Measurements of the. (mm). C7 A B C D E Width 1 R Width 2 R Width 3 R LENGTH R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L LENGTH L Height 1 L Height 2 L Height 3 L

64 Table A24: Angle from Midline, Right Side. (degrees). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A25: Angle from Midline, Left Side. (degrees). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

65 Table A26: Lateral Mass Height, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A27: Lateral Mass Height, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

66 Table A28: Lateral Mass Depth Measured On Axial Projection, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A29: Lateral Mass Depth Measured On Axial Projection, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

67 Table A30: Lateral Mass Width Measured On Axial Projection, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A31: Lateral Mass Width Measured On Axial Projection, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

68 Table A32: Lamina Length, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A33: Lamina Length, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

69 Table A34: Lamina Width Measured On Axial Projection, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A35: Lamina Width Measured On Axial Projection, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

70 Table A36: Lamina Angle from Midline, Right Side. (degrees). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A37 Lamina Angle from Midline, Left Side. (degrees). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

71 Table A38: Lateral Mass Measurement for Roy-Camille Technique, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A39: Lateral Mass Measurement for Roy-Camille Technique, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

72 Table A40: Lateral Mass Measurement for Magerl Technique, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A41: Lateral Mass Measurement for Magerl Technique, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

73 Table A42: Lateral Mass Measurement for An Technique, Right Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E Table A43: Lateral Mass Measurement for An Technique, Left Side. (mm). C3 C4 C5 C6 C7 Specimen A Specimen B Specimen C Specimen D Specimen E

74 Table A44: Intervertebral Foramen, Right Side. (mm). SPECIMEN A HEIGHT SPECIMEN A WIDTH SPECIMEN B HEIGHT SPECIMEN B WIDTH SPECIMEN C HEIGHT SPECIMEN C WIDTH SPECIMEN D HEIGHT SPECIMEN D WIDTH SPECIMEN E HEIGHT SPECIMEN E WIDTH C3 C4 C5 C6 C

75 Table A45: Intervertebral Foramen, Left Side. (mm). SPECIMEN A HEIGHT SPECIMEN A WIDTH SPECIMEN B HEIGHT SPECIMEN B WIDTH SPECIMEN C HEIGHT SPECIMEN C WIDTH SPECIMEN D HEIGHT SPECIMEN D WIDTH SPECIMEN E HEIGHT SPECIMEN E WIDTH C3 C4 C5 C6 C

76 Table A46: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle in mm. C3 C (3 MM GE) C (0.5 MM TOS) E (3 MM GE) E (0.5 MM TOS) Width 1 R Width 2 R Width 3 R Length R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L Length L Height 1 L Height 2 L Height 3 L

77 Table A47: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle in mm. C4 C (3 MM GE) C (0.5 MM TOS) E (3 MM GE) E (0.5 MM TOS) Width 1 R Width 2 R Width 3 R Length R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L Length L Height 1 L Height 2 L Height 3 L

78 Table A48: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle in mm. C5 C (3 MM GE) C (0.5 MM TOS) E (3 MM GE) E (0.5 MM TOS) Width 1 R Width 2 R Width 3 R Length R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L Length L Height 1 L Height 2 L Height 3 L

79 Table A49: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle in mm. C6 C (3 MM GE) C (0.5 MM TOS) E (3 MM GE) E (0.5 MM TOS) Width 1 R Width 2 R Width 3 R Length R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L Length L Height 1 L Height 2 L Height 3 L

80 Table A50: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right and left pedicle in mm. C7 C (3 MM GE) C (0.5 MM TOS) E (3 MM GE) E (0.5 MM TOS) Width 1 R Width 2 R Width 3 R Length R Height 1 R Height 2 R Height 3 R Width 1 L Width 2 L Width 3 L Length L Height 1 L Height 2 L Height 3 L

81 Table A51: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to anterior to posterior vertebral body dimension at midline in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C Table A52: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right lateral mass for Roy-Camille technique in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C

82 Table A53: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right lateral mass for Magerl technique in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C Table A54: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to right lateral mass for An technique in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C

83 Table A55: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to left lateral mass for Roy-Camille technique in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C Table A56: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to left lateral mass for Magerl technique in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C

84 Table A57: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to left lateral mass for An technique in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C Table A58: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen height, right side in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C

85 Table A59: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen height, left side in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C Table A60: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen width, right side in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C

86 Table A61: Comparison of 3 mm slices obtained on GE-scanner vs. 0.5 mm slices obtained from Toshiba scanner on specimens C and E. Measurements related to intervertebral foramen width, left side in mm. C 3 MM GE C 0.5 MM TOS E 3 MM GE E 0.5 MM TOS C3 C4 C5 C6 C Table A62: Comparison of axial and coronal measurements of the lateral mass, right side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation in mm. Lateral Mass Width Axial E R Lateral Mass Width Coronal E R Lateral Mass Width Axial C R Lateral Mass Width Coronal C R C3 C4 C5 C6 C

87 Table A63: Comparison of axial and coronal measurements of the lateral mass, left side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation in mm. Lateral Mass Width Axial E L Lateral Mass Width Coronal E L Lateral Mass Width Axial C L Lateral Mass Width Coronal C L C3 C4 C5 C6 C Table A64: Comparison of axial and coronal measurements of the lamina, right side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation in mm. Lamina Width Axial E R Lamina Width Coronal E R Lamina Width Axial C R Lamina Width Coronal C R C3 C4 C5 C6 C

88 Table A65: Comparison of axial and coronal measurements of the lamina, left side. Toshiba 0.5 mm slices. Axial images without gantry tilt and coronal images are generated without obliquity or angulation in mm. Lamina Width Axial E L Lamina Width Coronal E L Lamina Width Axial C L Lamina Width Coronal C L C3 C4 C5 C6 C

89 Statistical Summaries: Table A66: Average (Ave) and standard deviation (SD) for AP vertebral body dimension of C3-C7 for each specimen in mm. AP VB Ave AP VB SD Parasag AP ave Parasag AP SD Specimen A Specimen B Specimen C Specimen D Specimen E Table A67: Average (Ave) and standard deviation (SD) for AP canal dimension of C3-C7 for each specimen in mm. Canal AP ave Canal AP SD Canal R-L ave Canal R-L SD Specimen A Specimen B Specimen C Specimen D Specimen E

90 Table A68: Statistical summary 1 (in mm except pedicle angle in degrees) C3 Ave C3 SD C4 Ave C4 SD C5 Ave C5 SD C6 Ave C6 SD C7 Ave AP VB Parasag AP Canal AP Canal R- L Ped W1 R Ped W2 R Ped W3 R Ped W1 L Ped W2 L Ped W3 L Ped Len R Ped Len L Ped H1 R Ped H2 R Ped H3 R Ped H1 L Ped H2 L Ped H3 L Ped Ang R Ped Ang L C7 SD 99

91 Table A69: Statistical Summary 2 (in mm except lamina angle in degrees). C3 Ave C3 SD C4 Ave C4 SD C5 Ave C5 SD C6 Ave C6 SD C7 Ave C7 SD LM H R LM H L LM D R LM D L LM W AX R LM W AX L Lam Len R Lam Len L Lam W R Lam W L Lam Ang R Lam Ang L RC R RC L Mag R Mag L An R An L

92 Table A70: statistical Summary 3 (in mm) C3 Ave C3 SD C4 Ave C4 SD C5 Ave C5 SD C6 Ave C6 SD C7 Ave C7 SD IVF H R IVF W R IVF H L IVF W L Table A71: Data for effect of partial volume averaging calculation. Bone + water. mix # Bone Water Fat CT # of mix at 60 kev CT # of mix at 80 kev CT # of mix at 100 kev ,

93 Table A72: Data for effect of partial volume averaging calculation. Bone + fat. mix # Bone Water Fat CT # of mix at 60 kev CT # of mix at 80 kev CT # of mix at 100 kev (108.98) (93.88) (87.15) (82.56) (74.33) (70.36) (56.13) (54.77) (53.58) (5.89) (11.61) ,

94 Table A73: Data for effect of partial volume averaging calculation. Bone + 50/50 water/fat mix mix # Bone Water Fat CT # of mix at 60 kev CT # of mix at 80 kev CT # of mix at 100 kev (47.88) (42.05) (39.38) (23.91) (24.57) (24.50) (6.06) (8.67) ,

95 Table A74: Data for effect of partial volume averaging calculation. Bone + 75/25 water/fat mix mix # Bone Water Fat CT # of mix at 60 kev CT # of mix at 80 kev CT # of mix at 100 kev (18.56) (17.17) (16.45) (1.57) ,

96 Table A75: Data for effect of partial volume averaging calculation. Bone + 25/75 water/fat mix. mix # Bone Water Fat CT # of mix at 60 kev CT # of mix at 80 kev CT # of mix at 100 kev (78.43) (67.97) (63.26) (52.01) (48.41) (46.48) (26.81) (29.90) (30.64) , A76. Physical Specimen Measurements. Specimen Part Measurement in mm AP MidlineVertebral body 22 AP Midline Vertebral Body 20 AP Midline Vertebral Body 24 AP Midline Vertebral Body 20 AP Midline Vertebral Body 17 AP Midline Vertebral Body 15 AP Midline Vertebral Body 16 AP Midline Vertebral Body 18 Mid Height 7.3 Mid Height 4.2 Mid Height 4.3 Mid Height 5.0 Mid Height 6.9 Mid Height 9.3 Mid Height 11.1 Lateral Mass Junction Height 6.1 Mid Width 4.2 Mid Width

97 Mid Width 3.6 Mid Width 3.3 Mid Width 4.1 Mid Width 4.5 Mid Width 5.7 Mid Width 4.3 Lateral Mass Junction Width 4.2 Lamina Length 16 Lamina Length 14 Lamina Length 19 Lamina Length 17 Lamina Length 16 Lamina Length 17 Lamina Length 16 Lamina Length 14 Lamina Length 19 Lamina Length 17 Lamina Length 19 Lamina Length 21 Lamina Length 17 Lamina Length 16 Lamina Width 4.4 Lamina Width 1.9 Lamina Width 3.5 Lamina Width 3.7 Lamina Cortex 0.4 Lamina Cortex 0.3 Lamina Cortex 0.2 AP Canal 13 AP Canal 15 AP Canal 15 AP Canal 19 AP Canal 14 AP Canal 12 R-L Canal 25 R-L Canal 24 R-L Canal 28 R-L Canal 25 Lateral Mass Height 13 Lateral Mass Height 17 Lateral Mass Height 14 Lateral Mass Height 15 Lateral Mass Height 15 Lateral Mass Height

98 Lateral Mass Width 13 Lateral Mass Width 13 Lateral Mass Width 14 Lateral Mass Width 15 Lateral Mass Width 14 Lateral Mass Width 11 Lateral Mass Width 16 Lateral Mass Width 15 Lateral Mass Width 13 Lateral Mass Width 14 Lateral Mass Roy-Camille 14 Lateral Mass Roy-Camille 19 Lateral Mass Roy-Camille 15 Lateral Mass Roy-Camille 14 Lateral Mass Roy-Camille 13 Lateral Mass Magerl 18 Lateral Mass Magerl 22 Lateral Mass Magerl 27 Lateral Mass Magerl 24 Lateral Mass Magerl 20 Lateral Mass Magerl 24 Superior Cortex 1.9 Superior Cortex 1.7 Superior Cortex 1.7 Superior Cortex 3.2 Superior Cortex 3.1 Medial Cortex 1.2 Medial Cortex 1.4 Medial Cortex 1.0 Medial Cortex 2.0 Medial Cortex 1.4 Inferior Cortex 2.4 Inferior Cortex 1.9 Inferior Cortex 1.6 Inferior Cortex 3.2 Inferior Cortex

99 Figure A1. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone and Water. Bone Mix w/ Water Only 1, , CT # (HU) % Bone Mix at 60 kev Mix at 80 kev Mix at 100 KeV 108

100 Figure A2. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone, Fat and water. 1, Bone Mix w/ 75/25 Water/Fat 1, CT # (HU) (200.00) % Bone Mix at 60 kev Mix at 80 kev Mix at 100 kev 109

101 Figure A3. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone, Fat and Water. Bone Mix w/ 50/50 Water/Fat 1, , CT # (HU) (200.00) % Bone Mix at 60 kev Mix at 80 kev Mix At 100 kev 110

102 Figure A4. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone, Fat and Water. Bone Mix w/ 25/75 Water/Fat 1, , CT # (HU) (200.00) % Bone Mix at 60 kev Mix at 80 kev Mix at 100 kev 111

103 Figure A5. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing a Mixture of Bone and Fat. Bone Mix w/ Fat Only 1, , CT # (HU) (200.00) % Bone Mix at 60 kev Mix at 80 kev Mix at 100 kev 112

104 Figure A6. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 60 kev. CT Numbers at 60 kev 1, , CT # (HU) (200.00) % Bone Bone mix w/ water Bone mix w/ fat Bone mix w/ 50/50 water/fat Bone mix w/ 75/25 water/fat Bone mix w/ 25/75 water/fat 113

105 Figure A7. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 80 kev. CT Numbers at 80 kev CT # (HU) (100.00) (200.00) % Bone Bone mix w/ water Bone mix w/ fat Bone mix w/ 50/50 water/fat Bone mix w/ 75/25 water/fat Bone mix w/ 25/75 water/fat 114

106 Figure A8. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Mixtures at 100 kev. CT Numers at 100 kev CT # (HU) (100.00) (200.00) % Bone Bone mix w/ water Bone mix w/ fat Bone mix w/ 50/50 water/fat Bone mix w/ 75/25 water/fat Bone mix w/ 25/75 water/fat 115

107 Figure A9. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 60 kev. CT Numbers at 60 kev 1, , CT # (HU) (200.00) % Bone Bone mix w/ fat Bone mix w/ 25/75 water/fat Bone mix w/ 50/50 water/fat Bone mix w/ 75/25 water/fat Bone mix w/ water 116

108 Figure A10. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 80 kev. CT Numbers at 80 kev CT # (HU) (100.00) (200.00) % Bone Bone mix w/ fat Bone mix w/ 25/75 water/fat Bone mix w/ 50/50 water/fat Bone mix w/ 75/25 water/fat Bone mix w/ water 117

109 Figure A11. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures at 100 kev. CT Numbers at 100 kev CT # (HU) (100.00) (200.00) % Bone Bone mix w/fat Bone mix w/ 25/75 water/fat Bone mix w/ 50/50 water/fat Bone mix w/ 75/25 water/fat Bone mix w/ water 118

110 Figure A12. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures. Comparison of CT Numbers at 1-20% of Bone CT # (HU) (50.00) (100.00) (150.00) % Bone Bone w/ 60 kev Bone w/ 80 kev Bone /w fat 100 kev Bone 60 kev Bone w/ 25/75 80 kev Bone w/ 25/ kev Bone w/ 50/50 60 kev Bone w/ 50/50 80 kev Bone w/ 50/ kev Bone w/ 75/25 60 kev Bone w/ 75/25 80 kev Bone w/ 75/ kev Bone w/ 60 kev Bone w/ 80 kev Bone w/ 100 kev 119

111 Figure A13. Theoretical Calculation of Linear Attenuation Coefficient of Voxel Containing Various Mixtures. Comparison of CT Numbers at 10% and 20% bone mix Ct # (HU) (50.00) % Bone Bone w/ 100 kev Bone w/ 80 kev Bone w/ 60 kev Bone w/25/ kev Bone w/ 25/75 80 kev Bone w/ 25/75 60 kev Bone w/ 50/ kev Bone w/ 50/50 80 kev Bone w/ 50/50 60keV Bone w/75/ kev Bone W/ 75/25 80 kev Bone w/ 75/25 60 kev Bone w/ 100 kev Bone w/ 80 Kev Bone w/ 60 kev 120

112 Appendix B Figure B1a and b. B CT number (H) Lamina Body mm 1 mm slice thickness at 80 kvp and 80 mas, 10 cm DFOV. 121

113 Figure B2a and b. B CT number (H) mm 1 mm slice thickness at 80 kvp and 200 mas, 10 cm DFOV Lamina Body 122

114 Figure B3a and b. B CT number (H) mm mm slice thickness at 80- kvp and 300 mas, 10 cm DFOV Lamina Body 123

115 Figure B4a and b. B CT number (H) mm mm slice thickness at 120 kvp and 80 mas, 10 cm DFOV Lamina Body 124

116 Figure B5a and b. B CT number (H) Lamina Body mm 1 mm slice thickness at 120 kvp and 200 mas, 10 cm DFOV 125

117 Figure B6a and b. B CT number (H) mm mm slice thickness at 120 kvp and 280 mas, 10 cm DFOV 126 Lamina Body

118 Figure B7a and b. D CT number (H) mm 1 mm slice thickness at 80 kvp and 80 mas, 10 cm DFOV Lamina Body 127

119 Figure B8a and b. D CT number (H) mm 1 mm slice thickness at 80 kvp and 200 mas, 10 cm DFOV Lamina Body 128

120 Figure B9a and b. D CT number (H) mm 1 mm slice thickness at 80 kvp and 300 mas, 10 cm DFOV Lamina Body 129

121 Figure B10a and b. D CT number (H) mm 1 mm slice thickness at 120 kvp and 80 mas, 10 cm DFOV Lamina Body 130

122 Figure B11a and b. D CT number (H) Lamina Body mm 1 mm slice thickness at 120 kvp and 200 mas, 10 cm DFOV 131

123 Figure B12a and b. D CT number (H) Lamina Body mm 1 mm slice thickness at 120 kvp and 280 mas, 10 cm DFOV 132

124 Figure B13a and b. S CT number (H) mm 1 mm slice thickness at 80 kvp and 80 mas, 10 cm DFOV Lamina Body 133

125 Figure B14a and b. S CT number (H) Pecdicle Lamina Body mm 1 mm slice thickness at 80 kvp and 300 mas, 10 cm DFOV 134

126 Figure B15a and b. S CT number (H) mm mm slice thickness at 120 kvp and 80 mas, 10 cm DFOV Lamina Body 135

127 Figure B16a and b. S CT number (H) mm mm slice thickness at 120 kvp and 200 mas, 10 cm DFOV Pecicle Lamina Body 136

128 Figure B17a and b. S CT number (H) Lamina Body mm 1 mm slice thickness at 120 kvp and 280 mas, 10 cm DFOV 137

129 Figure B18a and b. S CT number (H) mm mm slice thickness at 120 kvp and 80 mas, 25 cm DFOV 138 Lamina Body

130 Figure B19a and b. S Double Pitch CT number (H) mm mm slice thickness at 120 kvp and 80 mas, 25 cm DFOV and pitch of 2 Lamina Body 139

131 - Variable Techniques CT number (H) mm D D D D D D Figure B20. Comparison of pedicle measurement profiles at the various technique setting for bone algorhitm. 140

132 Lamina Various Techniques CT number (H) D D D D D D mm Figure B21. Comparison of lamina measurement profiles at various technique settings for bone algorithm. 141

133 Various Algorithms CT number (H) mm Figure B22. measurement profile at same technique but different algorithms. 142 B D S

134 pedicle profiles - width C4 pedicle width C5 pedicle width C6 pedicle width Figure B23. Measurement profiles of pedicle width on MPR reconstructions with 0.5 mm slice thickness perpendicular to the pedicle length. 143

135 C4/5 IVF Measurement CT number (H) mm C4/5 IVF Figure B24. Measurement of the intervertebral foramen at C4-5 on MPR reconstruction perpendicular to pedicle length using 0.5 mm slice thickness. 144

136 Comparison of table pitch pitch of 1 pitch of CT number (H) mm Figure B25. Comparison of S with a table pitch of 1 to S with a table pitch of 2. Measurement profile of lamina used. 145

137 Appendix C Figure C1. B Original Image Figure C3. B Smoothing 2x Figure C2. B Smoothing 1x Figure C4. B Gaussian Blur 146

138 Figure C5. B Original Image Figure C7 B Sharpening 2x Figure C6. B Sharpening 1x Figure C8. B Unsharp Mask 147

139 Figure C9. Threshold level 79 and 1997 Figure C11. Threshold level 79 and 2502 Figure C10. Threshold level 79 and 2300 Figure C12. Threshold level 79 and

140 Figure C13. Threshold level 157 and 1997 Figure C15. Threshold level 303 and 1997 Figure C14. Threshold level 157 and 2502 Figure C16. Threshold level 303 and

141 Figure C17. Threshold level 482 and 1997 Figure C18. Threshold level 482 and