Scaphoid imaging with digital tomosynthesis as an adjunct to Radiography: A Single Department's experience

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1 Scaphoid imaging with digital tomosynthesis as an adjunct to Radiography: A Single Department's experience Poster No.: C-1036 Congress: ECR 2016 Type: Educational Exhibit Authors: B. Gibney, L. Murphy, D. Ryan, D. Hynes, P. J. MacMahon; Dublin/IE Keywords: Experimental, Digital radiography, Trauma, Bones, Diagnostic procedure, Cost-effectiveness, Socio-economic issues DOI: /ecr2016/C-1036 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 18

2 Learning objectives To compare Digital Tomosynthesis (DTS) feasibility, ease of use and diagnostic accuracy with plain radiographs in the diagnosis of scaphoid fractures. Page 2 of 18

3 Background Scaphoid fractures, the second most common wrist injury, represent 5% of all fractures and 71% of all carpal bone fractures 1,2. Scaphoid fractures most commonly involve the 3. waist (70%), proximal (20%) or distal pole (10%) The scaphoid is one of eight carpal bones, articulating with the radius, lunate, capitate, trapezium, and trapezoid. The scaphoid is almost entirely covered by cartilage and its blood supply is almost entirely intraosseous coming from a branch of the radial artery which enters the scaphoid distal to its waist. The blood supply can be severed in a fracture of the waist which may result in avascular necrosis of the proximal pole fragment. Diagnosis of scaphoid fracture on plain radiographs in the acute setting can be difficult, % of fractures can be missed on initial radiographs. This is, in part, due to overlapping osseous structures in the wrist joint and multiple curved surfaces of the scaphoid bone. If there is clinical suspicion of a fracture, conventional practice is to typically immobilise the wrist and perform follow up imaging after 2 weeks when the fracture may have become more apparent due to bone resorption at the fracture site. Failure to immobilise a wrist with a fracture can lead to complications such as non-union, avascular necrosis, development of carpal instability and osteoarthritis. Conversely, in cases where no fracture has occurred, unnecessary immobilisation can lead to 5,6 overtreatment, potential morbidity and loss of productivity for the patient. MRI is the current gold standard for diagnosis of scaphoid fractures however availability is limited, some patients are not suitable and bone contusions can be misidentified as fractures. Computed Tomography (CT), Radionuclide Bone Scan (planar, SPECT or SPECT-CT) are also used to investigate suspected occult scaphoid fractures however these modalities typically require scheduling, and are associated with increased costs and radiation doses. A readily available imaging modality for initial assessment that has a strong negative predictive value could potentially reduce unnecessary immobilisation. Digital tomosynthesis (DTS) is a novel radiographic technique which is being used in clinical practice imaging the chest, breast and for musculoskeletal indications, including scaphoid and wrist fracture detection 7,8. It involves sweeping the x-ray tube over an Page 3 of 18

4 angular range of about 50 with multiple low dose exposures to reconstruct a series of 9 slices of single planes (Fig.1). In the literature DTS has been found to be more sensitive and specific than plain 7 radiographs in diagnosing fractures at the wrist. It is faster, cheaper and has significantly less radiation dose when compared with CT. A comparison chart of DTS, CT, MRI and plain film was made using costings from our institution, national estimated waiting times 10 and radiation doses from previous studies (Fig. 2). Page 4 of 18

5 Images for this section: Fig. 1: Diagram of digital tomosynthesis system. Li et al. X-ray digital intra-oral tomosynthesis for quasi-three-dimensional imaging: system, reconstruction algorithm, and experiments. Opt. Eng. 52(1), (Jan 07, 2013). Doi: /1.OE Page 5 of 18

6 Fig. 2: Comparison of Tomosynthesis to other imaging modalities: Cost, Radiation dose, Outpatient Department waiting time and Duration of scan. - Dublin/IE Page 6 of 18

7 Findings and procedure details 143 patients presenting to the Emergency Department with acute wrist trauma and clinical suspicion of wrist fractures were immobilised and referred for follow up at the orthopaedic outpatient clinic for clinical and radiological review. The average age was 41 (median 38, range 16-82) and the male:female ratio was 1:1.55. At clinic, the patients had standard 4-view plain radiographs and lateral tomosynthesis of the injured wrist (Fig. 3). Plain film imaging was performed using a GE Discovery XR656 and digital tomosynthesis was captured with the same system using VolumeRAD software. The average number of tomosynthesis slices obtained was 46 (range ). The images were reviewed by an orthopaedic registrar and a consultant emergency radiologist. 39 fractures were identified in 36 patients (25% of patients). The identified fractures consisted of 11 scaphoid (Fig. 4), 15 distal radius (Fig. 5) and 13 other carpal/metacarpal fractures (Fig. 6). Eleven of the fractures identified with DTS were not identified on initial radiographs (Fig. 7). Two fractures were not seen on DTS and were identified later, a triquetrum fracture on plain radiographs 4 weeks after trauma and a scaphoid fracture seen on a second DTS 5 weeks after trauma. During the trial period a number of adjustments were made to the imaging protocol which subjectively improved ease of review and diagnostic accuracy. These included switching from lateral tomograms to DP tomograms and angling the forearm 20 degrees above the horizontal plane of imaging and placing the hand in ulnar deviation (Fig. 8). Discussion of the experience and impressions of those using the new imaging technique are as follows: Radiographers' Experience This new technique requires some training to utilise but once training has been received it is simple to perform. Difficulty in taking satisfactory images is low and similar to that of plain radiography of the scaphoid once one is familiar with performing a tomogram. Similarly, the time taken to perform imaging is approximately the same as plain radiography of the scaphoid. The only issue with tomography is the time taken for the series of images to be formatted. Computer processing can take up to 5 minutes for each tomogram and this could potentially introduce delays for radiographers. Orthopaedic Experience Page 7 of 18

8 Adjustment to the new technology can be slow with many preferring initially to use plain radiography images over tomograms. Some issues arise from simple technical problems which can be easily overcome with adjustments to PACs station settings. Others require practice such as discerning fractures from the artefacts of overlying structures. DP tomosynthesis is preferred as it is the plane usually used to view plain films of scaphoid. Tomosynthesis has been particularly sensitive for non-scaphoid occult wrist fractures. It is useful to have an additional imaging modality which can be accessed during clinic hours rather than rescheduling and potentially incurring prolonged patient waiting times for typical second line imaging modalities. Radiologists' Experience Experience in wrist tomosynthesis is required to be able to confidently diagnose abnormalities due to relatively pronounced DTS specific artefacts which can simulate fracture lines. The lateral position is good for distal radius and triquetal fractures but DP best for scaphoid, capitate and probably hamate. A combination of both is probably optimal. On our PACs the DTS imaging presents as a series of single images rather than a series such as in other cross sectional imaging modalities but this could likely be fixed in the future. It means zooming/windowing only affects the single image this is performed on rather than the whole series. There is definite room for improvement in the technology, namely reducing the effective slice thickness and overlying artefacts. Page 8 of 18

9 Images for this section: Fig. 1: Diagram of digital tomosynthesis system. Li et al. X-ray digital intra-oral tomosynthesis for quasi-three-dimensional imaging: system, reconstruction algorithm, and experiments. Opt. Eng. 52(1), (Jan 07, 2013). Doi: /1.OE Page 9 of 18

10 Fig. 3: Sample lateral DTS image showing good isolation of scaphoid bone with comparison of scaphoid fractures (arrows) to lateral plain radiograph. - Dublin/IE Page 10 of 18

11 Fig. 4: DP view Tomogram of a subacute scaphoid fracture (GIF) - Dublin/IE Page 11 of 18

12 Fig. 5: Sample undisplaced distal radius fracture, comparison of Plain radiography (LEFT) to DTS (RIGHT) - Dublin/IE Page 12 of 18

13 Fig. 6: Sample DP tomogram demonstrating hamate fracture (arrow) (GIF) - Dublin/IE Page 13 of 18

14 Fig. 8: Sample DTS with adjusted protocol: DP tomogram angling the forearm 20 degrees above the horizontal plane of imaging and placing the hand in ulnar deviation. Clearly demonstrates scaphoid fracture and cyst. - Dublin/IE Page 14 of 18

15 Fig. 7: DTS image (LEFT) compared to Plain Radiograph (Right) demonstrating a subtle scaphoid fracture (arrows) not diagnosed on initial Plain Film. - Dublin/IE Page 15 of 18

16 Conclusion DTS is a useful adjunct to fracture imaging. It is performed quickly and inexpensively with the same resources as used in plain film imaging of the limbs. The radiation dose is times less than that of wrist CT and similar to the dose from 4 views of plain radiographs. Interpretation of images can be challenging because of blurring of structures that are outside of the fulcrum plain and DTS specific artefacts. In our experience it does not currently appear to have a sufficiently high negative predictive value to rule out scaphoid fractures on initial assessment. However, it may be a beneficial adjunct in the follow up of suspected occult fractures and there is room for improvement in the technology. Page 16 of 18

17 Personal information B Gibney, Department of Radiology, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland. L Murphy, Department of Radiology, Cork University Hospital, Wilton, Cork, Ireland. DT Ryan, Department of Radiology, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland. N Compton, Department of Radiology Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland. J Cashman, Department of Orthopaedic Surgery, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland. D Hynes, Department of Orthopaedic Surgery, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland. P MacMahon, Department of Radiology, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland. Page 17 of 18

18 References 1. Larsen CF, Brondum V, Skov O. Epidemiology of scaphoid fractures in Odense, Denmark. Acta Or- thop Scand 1992; 63: Hove LM. Epidemiology of scaphoid fractures in Bergen, Norway. Scand J Plast Reconstr Surg Hand Surg. (1999); 33 (4): Bridgforth G, Cherf J. Lippincott's Primary Care Musculoskeletal Radiology. LWW (2010). 4. Pines JM, Everett WW. Evidence-Based Emergency Care, Diagnostic Testing and Clinical Decision Rules. BMJ Books. (2011) ISBN: Dorsay TA, Major NM, Helms CA. Cost-effective- ness of immediate MR imaging versus traditional follow-up for revealing radiographically occult scaphoid fractures. AJR 2001; 177: Burns MJ, Aitken SA, McRae D et al. The suspected scaphoid injury: resource implications in the absence of magnetic resonance imaging. Scott Med J. 2013; 58(3): Ottenin MA, Jacquot O, et al. Evaluation of the Diagnostic Performance of Tomosynthesis in Fractures of the Wrist. AJR 2012; 1: Geijer M, Borjesson A, Gothlin J. Clinical utility of tomosynthesis in suspected scaphoid fracture. A pilot study. Skeletal Radiology 2011; 7: Li L, Chen Z, Zhao Z, Wu D; X-ray digital intra-oral tomosynthesis for quasi-three-dimensional imaging: system, reconstruction algorithm, and experiments. Opt. Eng. 0001;52(1): doi: /1.oe Noel A, Ottenin MA, Germain C, et al. Comparison of irradiation for tomosynthesis and CT of the wrist [in French]. J Radiol 2011; 92:32-39 Page 18 of 18