Modest radiation dose reduction leads to inferior CT detection of liver lesions

CT evaluation of colorectal liver metastases was less effective after reducing the radiation dose by more than 50 percent, according to new findings published in Radiology.

The study included 52 adult patients with biopsy-proven colorectal cancer and suspected hepatic metastases. Each patient underwent two CT scans—a standard dose (SD) contrast CT scan and a reduced radiation dose (RD) CT scan—during the same breath hold. A team of three radiologists, blinded to which scan they were reading, performed detection and characterization of the lesions and assessed image quality. The specialists also compared filtered back projection (FBP) and seven iterative reconstruction algorithms.

Overall, the RD CT scans detected 82 percent of lesions, and the SD CT scans detected 97 percent of lesions. Per-lesion sensitivity was 79 percent for RD CT and 94 percent for SD CT. In addition, qualitative scores determined the quality of the SD CT images was higher than that of the RD CT images. The authors also noted that using iterative reconstruction algorithms was not enough to maintain observer performance.

“If the clinical task requires the detection of small low-contrast liver lesions, radiation dose levels should be maintained at levels that may be higher than those listed in the American College of Radiology dose index registry,” wrote Corey T. Jensen, MD, department of diagnostic radiology at the University of Texas MD Anderson Cancer Center in Houston, and colleagues.

The team added that its study did have limitations, including the fact that only two radiation levels were measured and the study focused on participants with “a single cancer type with already suspected hepatic metastases.” Further research is needed, they concluded, to determine how these findings correlate to other body regions, radiation dose levels and reconstruction methods.