Comparison of 3D X-ray tomography with computed tomography in patients with distal extremity fractures

Objective To compare fracture detection, image quality, and radiation dose in patients with distal extremity fractures using 3D tomography and computed tomography (CT). Materials and methods IRB approval was obtained including informed consent for this prospective study from June to December 2016. Patients diagnosed with an acute fracture at CT were consecutively scanned on the same day using 3D tomography. Anatomical location (effected bone and location within the bone) and morphological characteristics of fractures (avulsion, articular involvement, mono- vs. multifragmented, displacement), visibility of bone/soft tissue structures, and image quality were assessed independently by two blinded readers on a 5-point Likert scale. Dose-length-product (DLP; mGy*cm) was compared between both modalities. Descriptive statistics, Wilcoxon signed rank test (P < 0.05), Student'sttest (P < 0.05), and Cohen's kappa (kappa) for interreader reliability were calculated. Results In 46 patients (28 males; 18 females; mean age, 53 +/- 20 years) with 28 hand/wrist and 18 foot/ankle examinations, 86 out of 92 fractures were diagnosed with 3D tomography compared with CT. No false-positive finding occurred at 3D tomography. The six missed fractures on 3D tomography were five avulsion fractures of the carpals/metacarpals or tarsals/metatarsals, respectively, and one nondisplaced fracture of the capitate. Interreader agreement of anatomical location and morphological characteristics was substantial to almost perfect for upper (kappa = 0.80-0.96) and lower (kappa = 0.70-0.97) extremity fractures. Visibility of bone and soft tissue structures and image quality were slightly inferior using 3D tomography compared with CT (upper extremityP < 0.001-0.038 and lower extremityP < 0.001-0.035). DLP of a comparable scan coverage was significantly lower for 3D tomography (P < 0.001) for both upper (3D mean, 19.4 +/- 5.9 mGy*cm; estimated CT mean, 336.5 +/- 52.2 mGy*cm) and lower extremities (3D mean, 24.1 +/- 11.1 mGy*cm; estimated CT mean, 182.9 +/- 6.5 mGy*cm). Even the highest DLP with 3D tomography was < 30% of the mean estimated CT dose of a comparable area of coverage. Conclusion Fracture assessment of peripheral extremities is reliable utilizing a low-dose 3D tomography X-ray system, with slightly reduced image quality.