Radiation dose reduction for musculoskeletal computed tomography of the pelvis with preserved image quality

ObjectiveTo analyze the impact of pelvic computed tomography (CT) technique optimization on estimated dose and subjective and objective image quality. Materials and methods: An institutional review board (IRB)-approved retrospective records review was performed with waived informed consent. Five CT scanners (various manufacturers/models) were standardized to match the lowest dose profile on campus via subjective assessment of clinical images by experienced musculoskeletal radiologists. The lowest dose profile had previously been established through image assessment by experienced musculoskeletal radiologists after a department-wide radiation dose reduction initiative. A consecutive series of 60 pre- and 59 post-optimization bony pelvis CTs were analyzed by two residents, who obtained signal-to-noise ratio for femoral cortex and marrow, gluteus medius muscle, and subcutaneous and visceral fat in a standardized fashion. Two blinded attending radiologists ranked image quality from poor to excellent. Results: Pre- and post-optimization subjects exhibited no difference in gender, age, or BMI (p>0.2). Mean CT dose index (CTDIvol) and dose-length product (DLP) decreased by approximately 45%, from 3914 to 18 +/- 12mGy (p<0.0001) and 1,227 +/- 469 to 546 +/- 384mGy-cm (p<0.0001). Lower body mass index (BMI) was associated with a larger dose reduction and higher BMI with higher DLP regardless of pre- or post-optimization examination. Inter-observer agreement was 0.64-0.92 for SNR measurements. Cortex SNR increased significantly for both observers (p<0.02). Although qualitative image quality significantly decreased for one observer (p<0.01), adequate mean quality (3.3 out of 5) was maintained for both observers. Conclusion: Subjective and objective image quality for pelvic CT examination remains adequate, despite a substantially reduced radiation dose.