Low-Dose Computed Tomography Reduces Radiation Exposure by 90% Compared With Traditional Computed Tomography Among Patients Undergoing Hip-Preservation Surgery

Purpose: To compare the delivered radiation dose between a low-dose hip computed tomography (CT) scan protocol and traditional hip CT scan protocols (i.e., “traditional CT”). Methods: This was a retrospective comparative cohort study. Patients who underwent hip-preservation surgery (including arthroscopy, surgical hip dislocation, or periacetabular osteotomy procedures) at our institution between 2016 and 2017 were identified. Patients were excluded if they had a body mass index (BMI) greater than 35, they underwent previous surgery, or a radiation dose report was absent. The low-dose group included patients who underwent hip CT at our institution using a standardized protocol of 100 kV (peak), 100 milliampere-seconds (mAs), and a limited scanning field. The traditional CT group included patients who had hip CT scans performed at outside institutions. The total effective dose (E _hip ), effective dose per millimeter of body length scanned, patients' age, and patients' BMI were compared by univariate analysis. The correlation of E _hip to BMI was assessed. Results: The study included 41 consecutive patients in the low-dose group and 18 consecutive patients in the traditional CT group. Low-dose CT resulted in a 90% reduction in radiation exposure compared with traditional CT (E _hip , 0.97 ± 0.28 mSv vs 9.68 ± 6.67 mSv; P <.0001). Age (28 ± 11 years vs 26 ± 10 years, P =.42), sex (83% female patients vs 76% female patients, P =.74), and BMI (24 ± 3 vs 24 ± 3, P =.75) were not different between the 2 groups. E _hip had a poor but significant correlation to BMI in the low-dose CT group (R ² = 0.14, slope = 0.03, P =.02) and did not correlate to BMI in the traditional CT group (R ² = 0.13, P =.14). Conclusions: A low-dose hip CT protocol for the purpose of hip-preservation surgical planning resulted in a 90% reduction in radiation exposure compared with traditional CT. Level of Evidence: Level II, diagnostic study.