Comparison Between Weight-Based Variable-Voltage and Fixed Volume-Voltage Protocols in Cancer Surveillance Computed Tomography

Objective: This study assessed whether the weight-based, variable tube voltage (Bayer MEDRAD Centargo SMART) protocol compared with a fixed contrast, fixed tube voltage (referred to as the ‘OLD’) protocol for cancer patients undergoing CT chest, abdomen, and pelvis (CAP) scans could reduce contrast dose, without a reduction in contrast enhancement. Methods: A total of 149 oncology patients, each underwent 2 surveillance CT CAP scans using both the OLD and SMART protocols, typically with a 3-month interval between scans. Contrast volume was recorded for each protocol as well as the CT attenuation measurement Hounsfield unit (HU) at the ascending aorta, pulmonary trunk, right atrial appendage, middle hepatic vein, main portal vein, and renal cortex, as well as dose-length product (DLP, mGy/cm) and CT Dose Index volume (CTDIvol, mGy). Results: The SMART protocol used less contrast per patient with a median volume of 80 versus 100 mL representing a 20% absolute reduction. Quantitative contrast enhancement measurements demonstrated non-inferior HU values in the SMART protocol at all sites. This was achieved with a 19% DLP and 9% CTDIvol decrease in radiation exposure. Conclusions: The weight-based contrast, variable tube voltage protocol effectively reduces contrast volume without increasing radiation dose and does not reduce contrast enhancement.