Cone Beam Computed Tomography: Clinical Applications in Musculoskeletal Imaging.

Transcription

1 Cone Beam Computed Tomography: Clinical Applications in Musculoskeletal Imaging. Poster No.: C-1412 Congress: ECR 2014 Type: Scientific Exhibit Authors: E. De Smet 1, G. De Praeter 1, K. L. Verstraete 2, F. M. H. M. Keywords: DOI: Vanhoenacker 3 ; 1 Duffel/BE, 2 Gent/BE, 3 Antwerp, Ghent, Mechelen/BE Trauma, Comparative studies, Conventional radiography, Cone beam CT, Musculoskeletal joint, Musculoskeletal bone /ecr2014/C-1412 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 17

2 Aims and objectives Cone-Beam Computed Tomography (CBCT) differs from conventional CT in both the acquirement and processing of imaging data. In conventional CT, a fan-shaped beam is aimed at a linear receptor, creating a one-dimensional projection. The small width of the beam obliges a helical movement of both radiation source and receptor around the patient in order to scan a certain surface. (Fig. 1A) This is avoided in CBCT by using a cone-shaped beam and a flat detector: a single rotation around the patient is sufficient to scan a given volume and to create a twodimensional projection. (Fig. 1B) As a result, CBCT has a higher spatial resolution and lower radiation dose than conventional CT. [1] Despite the major advantage of the high spatial resolution when imaging small osseous structures, musculoskeletal applications of CBCT have been scarcely reported. The purpose of this study is twofold: 1. To assess the sensitivity and specificity of conventional radiography (CR) compared to CBCT in detecting fractures after acute trauma of small bones and joints. 2. To compare radiation doses of CR and CBCT in the examined joints. Images for this section: Page 2 of 17

3 Fig. 1: A. Conventional CT B. Cone Beam CT Page 3 of 17

4 Methods and materials This prospective study, approved by the ethical committee of our institution, was conducted between June 1 and November 15, 2013 and informed consent was given by all patients. A total of 212 patients were included, based on the following criteria: 1. recent (<1 week old) small bone/joint trauma 2. patient's ability to perfect immobilisation during the examination. All patients underwent both conventional radiography followed by CBCT. The examinations were performed on a New Tom 5G CBCT (Fig. 2) with the following protocol: 110 kv, variable mas (1-20, based on examined joint), slice thickness 0.5 mm and scan surface 8x8 cm. The acquired data were reconstructed in axial, sagittal and coronal planes. All images were interpreted by 2 radiologists in consensus, with interpretation of plain films blinded to the information derived from the CBCT (which was regarded as golden standard). Images for this section: Page 4 of 17

5 Fig. 2: New Tom 5G CBCT Page 5 of 17

6 Results The most frequent examined joints were the wrist (n=48) and ankle (n=41), followed by finger (n=33), midfoot (n=26), elbow (n=22), toe (n=19), hand (n=17) and knee (n=6). In total, 65 fractures were diagnosed on conventional radiography compared to 96 fractures on CBCT. Most of these additional fractures visualized on CBCT were located at the ankle (n=5), foot (n=4), wrist (n=4) and finger (n=4). (Fig. 3) In particular non-displaced fractures (n=15) and avulsion fractures (n=11) were better depicted on CBCT. (Fig 4-6) CBCT was also helpful in the work-up of more complex lesions and enabled visualization of additional fracture lines. (Fig. 7) The sensitivity of CR compared to CBCT for fracture detection ranged between 63 and 100%. In one examination of the wrist, a fracture was described on CR, which could not be withheld on CBCT and was therefore considered as false positive. Therefore, the specificity ranged between 96 and 100%. (Table 1) Radiation dose The mean radiation dose of CBCT exceeded that of CR in all examined joints. (Table 2) The difference in radiation dose between CR and CBCT was inversely related to the size of the examined joint or bone; in fingers, the mean radiation dose of CBCT was up to 10 times higher than of CR. When joint size increased, the difference in radiation dose (relatively) decreased. Images for this section: Page 6 of 17

7 Fig. 3: Total number of examinations per joint (in black) and visualized fractures on conventional radiography (blue) and CBCT (red). Fig. 4: Conventional radiograph (A) and CBCT (B,C) of a 16-year-old patient after inversion injury of the left ankle. Conventional images show a subtle soft tissue swelling Page 7 of 17

8 at the lateral malleolus, but no osseous lesions. CBCT reveals a small avulsion fracture at the lateral malleolus (arrow). Page 8 of 17

9 Fig. 5: Conventional radiographs (A,B) and CBCT (C,D) of a 57-year-old man after fall on the left elbow. A radial head fracture is evident on conventional imaging (arrow). On CBCT, an additional intra-articular fracture fragment (arrowhead) is visualized. Page 9 of 17

10 Fig. 6: 17-year-old boy after fall on the left wrist. Conventional radiographs (A,B) reveal a displacement of the prescaphoid fat pad (arrowhead), but can not identify the fracture. Page 10 of 17

11 On CBCT (C,D), a small cortical irregularity (arrow) indicates a (minimally displaced) scaphoid fracture. Fig. 7: 43-year-old man with pain at the left ankle after a fight. A subtle fracture line is noted on conventional radiographs (A,B). The fracture is better depicted on CBCT (C-E), as are several additional fracture lines. Page 11 of 17

12 Table 1: Sensitivity and specificity of conventional radiography in the detection of fractures, compared to CBCT. Table 2: Comparison of mean radiation dose (DAP, mgy x cm²) in CR and CBCT in the examined joints/bones. Values between brackets present the dose range in each joint/ bone. Page 12 of 17

13 Conclusion CBCT is a relatively new technique with very high spatial resolution, relatively low radiation dose and excellent 3D-reconstuction possibilities. [2,3] These characteristics made it the new 'golden standard' in dental imaging and in the last decades, dental applications of CBCT have been extensively reported. [4] CBCT has also an established place in the imaging of paranasal sinuses, temporal bone and maxillofacial trauma. [4-9] Musculoskeletal applications of CBCT have been more scarcely reported. Faccioloi et al. compared CBCT and Multi-Detector CT (MDCT) in the evaluation of finger fractures in 173 patients and concluded that the accuracy of CBCT equalled that of MDCT in the detection of fractures but was slightly less sensitive in visualising all fracture fragments. [10] The use of CBCT in arthrography of the wrist has been reported as well with excellent results in the assessment of TFCC ligaments and articular cartilage. [2,11] Additionally, CBCT has been reported as a valuable tool in the evaluation of occult scaphoid fractures and the follow-up of fracture treatment especially when osteosynthesis material was present (due to reduced metal artefacts). [2,12] Our study directly compared the sensitivity and specificity of conventional radiography compared to CBCT in the detection of fractures in small bones and joints. On conventional radiography, % of the fractures were visible, depending of the visualised bones/ joints. Specificity was excellent, with only one false positive fracture identified. Particularly small avulsion fragments and non-displaced fractures of the wrist and ankle were better depicted on CBCT. Radiation doses of CBCT and CR were measured in dose area product (DAP, mgy x cm²), which offers more precise measurement than Computed Tomography Dose Index (CTDI), used in MDCT. [13,14] The effective dose on each joint can be obtained by the use of a conversion table. (Table 3) [15] Radiation doses in CBCT exceeded those of conventional radiography in all examinations, and this difference was the highest in small bones/joint (e.g. fingers). We did not make a comparison with radiation doses in MDCT. Other authors have reported the effective radiation doses in MDCT to be 1.5- >100 times higher than in CBCT. [16-18] For example, Peltonen et al. measured an effective radiation dose in CBCT of the middle ear of 13µSv, which is 60 times lower than in an average MDCT examination. [19] We acknowledge some limitations of this study: 1. the limited number of patients for some joints (in particular knee) Page 13 of 17

14 2. potential selection bias, due to exclusion of patients who were not able to lie perfectly still e.g. children under the age of 5 or the very elderly patients). 3. incomplete follow-up of some patients (who were treated in other hospitals). 4. absence of comparison with MDCT. This study demonstrates that CBCT increases the detection rate of fractures at the expense of higher radiation dose. However, due to the relatively low biological effect on small peripheral joints (see table 3, conversion coefficients), the radiation dose for the patient remains acceptable. In cases where there is a high clinical suspicion for a fracture and plain films are negative, CBCT could be used as an accurate tool to confirm or exclude fractures. Furthermore, CBCT could be helpful to analyze complex fractures. A potential drawback of CBCT could be the decreased soft tissue contrast compared to MDCT, making evaluation of indirect markers of osseous trauma (e.g. displaced fat pads) more difficult. Whether CBCT can replace plain radiography as primary examination is still an open question and therefore, further prospective studies are mandatory. Images for this section: Page 14 of 17

15 Table 3: Conversion factors (µsv/mgy x cm) for each examined joint. (after Biswas et al. [15]) Page 15 of 17

16 Personal information References 1. Mozzo P, Procacci C, Tacconi A et al. A new volumetric CT machine for dental imaging based on the conebeam technique: preliminary results. Eur Radiol. 1998; 8: De Cock J, Mermuys K, Goubau J et al. Cone-beam computed tomography: a new lowdose, high-resolution imaging technique of the wrist, presentation of three cases with technique. Skeletal Radiol. 2012; 41: Miracle AC, Mukherji SK. Conebeam CT of the head and neck, part 2: clinical applications. Am J Neuroradiol 2009; 30: De Vos W, Casselman J, Swennen GRJ. Cone-Beam computerized tomography (CBCT) imaging of the oral and maxillofacial region : A systematic review of the literature. Int J Oral Maxillofacial Surg 2009; 38: Maillet M., Bowles W.R., McClanahan S et al. Conebeam computed tomography evaluation of maxillary sinusitis. J Endod 2011; 37: Zoumalan RA, Lebowitz RA, Wang E et al. Flat panel conebeam computed tomography of the sinuses. Otolaryngology- Head and Neck Surgery 2009; 140: Kuhweide R, Offeciers E, Casselman JW. Cone beam computed tomography, a lowdose imaging in the postoperative assessment of cochlear implantation. Otol Neurotol 2009; 30: Penninger RT, Tavassolie TS, Carey JP: Cone-beam volumetric tomography for applications in the temporal bone. Otol Neurotol 2011; 32: Shintaku WH, Venturin JS, Noujeim M. Applications of conebeam computed tomography in fractures of the maxillofacial complex. Dental Traumatology 2009; 25: Faccioli N, Foti G, Barillari M et al. Finger fractures imaging: accuracy of conebeam computed tomography and multislice computed tomography. Skeletal Radiol 2010; 39: Koskinen SK, Haapamäki VV, Salo J et al. CT arthrography of the wrist using a novel, mobile, dedicated extremity cone-beam CT (CBCT). Skeletal Radiol 2012: 1-9. Page 16 of 17

17 12. Smith E., Al-Sanawi HA, Gammon B et al. Volume slicing of cone-beam computed tomography images for navigation of percutaneous scaphoid fixation. Int J CARS 2012; 7: Lofthag-Hansen S, Thilander-Klang A, Ekestubbe A et al. Calculating effective dose on a cone beam computed tomography device: 3D Accuitomo and 3D Accuitomo FPD. Dentomaxillofac Radiol 2008; 37: Vassileva J, Stoyanov D. Quality control and patient dosimetry in dental cone beam CT. Radiat Prot Dosim 2010; 139: Biswas D, Bible JE, Bohan M et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone & Joint Surgery 2009; 91(8): Tsiklakis K, Donta C, Gavala S et al. Dose reduction in maxillofacial imaging using low dose cone beam CT. Eur J Radiol 2005; 56: Roberts JA, Drage NA, Davies J et al. Effective dose from cone beam CT examinations in dentistry. Br J Radiol 2009; 82(973): Koong B. Cone beam imaging: is this the ultimate imaging modality? Clin Oral Implants Res 2010; 21(11): Peltonen LI, Aarnisalo AA, Kortesniemi MK et al. Limited cone-beam computed tomography imaging of the middle ear: a comparison with multislice helical computed tomography. Acta Radiol 2007; 48: Page 17 of 17