Balancing Radiation and Contrast Media Dose in Single-Pass Abdominal Multidetector CT. Prospective Evaluation of Image Quality

Rationale and Objectives: As both contrast and radiation dose affect the quality of CT images, a constant image quality in abdominal contrast-enhanced multidetector computed tomography (CE-MDCT) could be obtained balancing radiation and contrast media dose according to the age of the patients. Materials and Methods: Seventy-two (38 Men; 34women; aged 20-83years) patients underwent a single-pass abdominal CE-MDCT. Patients were divided into three different age groups: A (20-44years); B (45-65years); and C (>65years). For each group, a different noise index (NI) and contrast media dose (370 mgI/mL) was selected as follows: A (NI, 15; 2.5mL/kg), B (NI, 12.5; 2mL/kg), and C (NI, 10; 1.5mL/kg). Radiation exposure was reported as dose-length product (DLP) in mGy × cm. For quantitative analysis, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated for both the liver (L) and the abdominal aorta (A). Statistical analysis was performed with a one-way analysis of variance. Standard imaging criteria were used for qualitative analysis. Results: Although peak hepatic enhancement was 152±16, 128±12, and 101±14 Hounsfield units (P<.001) for groups A, B, and C, respectively, no significant differences were observed in the corresponding SNR<inf>L</inf> with 9.2±1.4, 9.1±1.2, and 9.2±3. Radiation (mGy × cm) and contrast media dose (mL) administered were 476±147 and 155±27 for group A, 926±291 and 130±16 for group B, and 1981±451 and 106±15 for group C, respectively (P<.001). None of the studies was graded as poor or inadequate by both readers, and the prevalence-adjusted bias-adjusted kappa ranged between 0.48 and 0.93 for all but one criteria. Conclusions: A constant image quality in CE-MDCT can be obtained balancing radiation and contrast media dose administered to patients of different age.