Low-concentration contrast abdominopelvic CT: A comparison with high-concentration contrast CT image quality

Objective This study aimed to compare abdominopelvic computed tomography (APCT) image quality using low and high concentrations of a contrast agent in patients with cancer via a noninferiority design. Methods This study prospectively included 99 patients with malignancies who underwent dual-source APCT following injection of 1.5 mL/kg of iohexol 270 (low-concentration group). The control group included patients who were retrospectively matched 1:1 based on weight, body mass index, and sex. These patients (high-concentration group) received 1.1 or 1.2 mL/kg of iohexol 350, reconstructed at two tube voltages (80 kVp and 80/Sn150 kVp). The noninferiority margins were set at −0.21 for overall image quality. Two radiologists blindly and independently analyzed the subjective and objective image quality of matching focal lesions. Results A total of 198 patients with 102 focal lesions (44 liver lesions, 58 renal lesions) were assessed. The total iodine amount was slightly higher in the low-concentration group than in the high-concentration group without significant differences (24580.0 ± 3745.6 vs. 24190.2 ± 3954.3 mg I/mL; p = 0.051). Overall image quality did not differ significantly between the groups (2.6 ± 0.5 vs. 2.6 ± 0.5 on 80 kVp; p = 0.484; 3.4 ± 0.5 vs. 3.4 ± 0.6 on 80/Sn 150 kVp, p = 0.891). Margin sharpness and conspicuity also showed no significant differences between the low- and high-concentration groups at 80 kVp ( p = 0.890, 0.103) and 80/Sn 150 kVp images ( p = 0.278, 0.369). Liver attenuation was slightly higher in the low-concentration than in the high-concentration group (80 kVp, 127.3 ± 16.8 vs. 122.4 ± 13.0, p = 0.013; 80 kVp/Sn 150 kVp, 108.2 ± 13.3 vs. 104.5 ± 10.9, p = 0.025). No major or minor adverse reactions occurred during or immediately after contrast agent injection in either group. Five patients in the low-concentration group experienced below-average vascular pain. Conclusions The low-concentration group offered noninferior overall image quality compared to the high-concentration group among patients with cancer.