Dual energy CT arthrography in shoulder instability: successful iodine removal with virtual non-contrast images and accurate 3D reformats of the glenoid for assessment of bone loss

Objective To evaluate the image quality of dual energy CT (DECT) of the shoulder after arthrography and of virtual non-contrast (VNC) 3D reformats of the glenoid and to compare glenoid measurements on VNC 3D reformats and on 2D CTs. Materials and methods DECT arthrography (80 kV/140 kV) was performed in 42 shoulders of 41 patients with instability using diluted iodinated contrast media (80 mg/ml). VNC images and VNC 3D reformats of the glenoid were calculated using image postprocessing. Dose parameters, CT values of intraarticular iodine and muscle, image contrast (iodine/muscle), and image quality (5-point scale: 1 = worst, 5 = best) were evaluated. Two independent readers assessed glenoid morphology and performed glenoid measurements on 2D and 3D images. Results Calculation of VNC images and VNC 3D reformats was successful in 42/42 shoulders (100%). The effective dose was mean 1.95 mSv (+/- 0.9 mSv). CT values of iodine and muscle were mean 1014.6 HU (+/- 235.8 HU) and 64.5 HU(+/- 8.6 HU), respectively, and image contrast was mean 950.2 HU (+/- 235.5 HU). Quality of cross-sectional images, VNC images, and VNC 3D reformats was rated good (median 4 (4-5), 4 (3-4), 4 (3-5), respectively). Detection of an osseous defect was equal on 2D and 3D images (13/42, P > 0.99) with no difference for measurement of the glenoid diameter with mean 28.3 mm (+/- 2.8 mm) vs. 28.4 mm (+/- 2.9 mm) (P = 0.5), width of the glenoid defect with 3.2 mm (+/- 2.1 mm) vs. 3.1 mm (+/- 2.3 mm) (P = 0.84), surface area with 638.5 mm(2) (+/- 127 mm(2)) vs. 640.8 mm(2) (+/- 129.5 mm(2)) (P = 0.47), and surface area of the defect with 46.6 mm(2) (+/- 44.3 mm(2)) vs. 47.2 mm(2) (+/- 48.0 mm(2)) (P = 0.73), respectively. Conclusion DECT shoulder arthrography is feasible and allows successful iodine removal with generation of VNC images and accurate VNC 3D reformats of the glenoid for assessment of bone loss.