16-row multidetector CT of the pelvis after iliosacrally inserted osteosynthetic screws: experimental study of dose adjustment on preserved human cadaver specimens

Purpose: the study was performed to assess the necessity of dose adjustment (kV or mAseff.) in 16-slice CT (MDCT) in postoperative controls of iliosacrally inserted osteosynthetic screws (OS) on preserved human cadaver specimens. The minimal tube settings for diagnostic imaging of the pelvic bone were analyzed and the effective doses and important organ doses were calculated. Materials and methods: 16 preserved human cadaver specimens with transiliac osteosynthetic screws were scanned on a 16-slice CT (collimation 16 x 0.75 mm, pitch 0,7) with 10 different tube settings (35, 50, 75, 100, 150mAseff. and 120 and 140 kV). 32 datasets (blinded for name and scan parameters) with and without OS were independently evaluated by four observers. The 10 series were sorted by subjective image quality (image noise, contours, artifacts), and the series with the lowest but still diagnostic quality was selected. The statistical analysis included multi-rater-kappa-test and Wilcoxon test for paired samples. Results: the multi-reader agreements for sorting the series were fair (κ=0.38). The agreements in comparing the lowest diagnostic image qualities were slight to fair (κ=0.08-0.23). The paired sample test comparing the lowest diagnostic image quality with and without OS showed no statistical significance (p=0.29). 87.5% of the readouts (n=64 [16 examinations, 4 readers]) with OS and 78.1% of those without OS could be adequately diagnosed using the three series with the lowest effective doses (0.9 - 1.4 mSv for men, 1.4 - 2.0 mSv for women: 120 kV-35 mASeff., 120 - 50, 140-35). (orig.)