Quantifying the Performance of Enhanced Radiation Output, Dual-Source CT Relative to Traditional CT in Patients With Severe Obesity.

Objective: In CT imaging of severely obese patients, demanding clinical tasks like liver imaging may be constrained by scanner radiation output limits. This may impose an unavoidable increase in image noise and loss of image quality. In such patients, scan parameters may be restricted, leading to excessive x-ray tube heating and increased scan times that degrade exam and image consistency relative to other patients. In this study, the performance of dual-source (DS) CT with enhanced radiation output capacity was quantified relative to conventional single-source (SS) CT. The focus was on abdominopelvic imaging in severely obese patients (BMI >45 kg/m2).

Methods: Abdominopelvic portal venous phase CT exams performed using DSCT were compared with exams using SSCT. General usage characteristics of the DSCT protocol were analyzed for >3000 exams over a 42-month period. More specifically, a total of 95 matched SS and DS scan pairs for the same patients were assessed in detail. The tube voltage, reconstruction method, and scanner platform were consistent in matched SS and DS scans, and changes in patient weight, diameter, and water equivalent diameter were <5%. Image global noise (GN), radiation dose (CTDIvol), and key scan parameters were compared between matched SS and DS exams.

Results: The median (IQR) patient BMI was 48.4 kg/m2 (45.9-52.1 kg/m2). In the matched scan pairs, SS scans had a median (IQR) CTDIvol of 36.5 mGy (35.2-42.9 mGy) and median (IQR) GN of 14.1 HU (12.6-15.9 HU). DS scans had a significantly increased median (IQR) CTDIvol of 62.5 mGy (55.8-69.8 mGy) and reduced median (IQR) GN of 11.4 HU (10.6-12.4 HU; both P<0.001). Relative to SSCT, the DSCT protocol also enabled faster scan times at equal CTDIvol, lower tube current per x-ray tube, and improved GN consistency throughout axial slices.

Conclusion: It is feasible to utilize a DSCT protocol to significantly increase radiation output, bringing image noise characteristics in line with the general patient population in abdominopelvic imaging of severely obese patients. The DSCT protocol offers a more straightforward option to attain consistency in a group of patients where achieving diagnostic CT quality has proved challenging.