Monoenergetic imaging of dual energy CT in the evaluation of metal fixation of fractures

Objective: To evaluate monoenergetic imaging of dual energy CT in the visualization of metal fixation of fractures. Methods: In total, 29 patients with fractures underwent 36 metal fixations, including 11 extemal fixations implanting in tibiofibula (n=11) and 25 internal fixations (cervical spine, n=10; lumbar spine, n=4; tibiofibula, n=8; radial bone, n=3). They were recruited into this study. After dual energy CT scan, monoenergetic software was used to post-process with the following 6 photon energies: 40, 70, 100, 130, 160, 190 keV. Two radiologists evaluated and rated the reformatted images with 6 different photon energies and average weighted 120 kV images according to the following 4-score scale. Score 1: nonassessable, with marked artifact; score 2: assessable, moderate artifact; score 3: good, mild artifact, good visualization of bony structures; score 4: excellent, no artifact. Kruskal-Wallis was used to perform statistical analysis of image quality for total fixations, external and internal fixations with various selective keV settings and average weighted 120 kV. Results: For total fixations, monoenergetic imaging of dual energy CT has 25 fixations with score 3 and 4, but 120 kV has only 4 fixations with score 3 and 4, Monoenergetic imaging of dual energy CT improved image quality of fractures with metal fixation compared to average weighted 120 kV images (F=116.487, P<0.01). Images of 130 keV had the best image quality for external metal fixation (9 fixations with score 3 and 4, F=60.902, P<0.01), while 70 keV was best for internal metal fixation (F=122.149, P<0.01). Conclusions: Monoenergetic imaging of dual energy CT improves image quality of fractures with metal fixation. Reformatted images at 70 keV and 130 keV have the optimal image quality for internal and external metal fixation, respectively. (authors)