Reducing Iodine Contrast Volume in CT Angiography of the Abdominal Aorta Using Integrated Tube Potential Selection and Weight-Based Method Without Compromising Image Quality.

OBJECTIVE: The purpose of this study is to determine whether image quality was maintained when a weight-based protocol incorporating tube potential selection was used to select lower iodine contrast volumes for aortic CT angiography (CTA).

MATERIALS AND METHODS: Patients with potentially decreased renal function underwent CTA performed with the iodinated contrast volume determined using a table incorporating different tube potentials and patient weights. The image quality of CTA examinations performed with a reduced iodine volume (hereafter known as "low-iodine CTA examinations"), internal control CTA examinations (i.e., prior examinations), and size-matched control CTA examinations was evaluated in separate reading sessions conducted by three vascular radiologists who were blinded as to the contrast volume and tube potential used. Side-by-side unblinded comparison of the examinations was also performed. Aortic attenuation and the contrast-to-noise ratio were measured. Comparisons were performed using the Wilcoxon signed rank test.

RESULTS: Fifty low-iodine CTA examinations, 36 internal control CTA examinations, and 50 size-matched control CTA examinations were performed. Contrast volumes were 63% lower when the protocol based on tube potential and patient weight was used (mean contrast volume, 49 mL for low-iodine CTA vs 133 mL for internal control CTA and 138 mL for size-matched control CTA). The mean volume CT dose index was 15.1 mGy for low-iodine CTA versus 18.8 mGy for internal control CTA (p < 0.001), and 15.3 mGy for low-iodine CTA versus 17.1 mGy for size-matched control CTA (p = 0.11). Of the image quality and diagnostic confidence evaluations for low-iodine CTA examinations, over 97% had acceptable image quality and diagnostic confidence for blinded (50/50) and unblinded (35/36) comparisons. Aortic attenuation was similar between groups (p = 0.13-0.71).

CONCLUSION: A weight-based protocol that incorporates tube potential selection allows the use of substantially lower volumes of iodinated contrast material in aortic CTA while maintaining acceptable image quality.