Reduced-dose CT protocols for renal colic are used infrequently in the U.S., demonstrating need for appropriate reduction in the dose index for these protocols to reduce patient exposure and lower risk for long-term malignancy, according to a study published in the May issue of Radiology.

Although research has demonstrated reduced-dose CT’s accuracy in detecting renal stones, the extent to which this technique has been adopted in the U.S. is not known. Lead author Adam Lukasiewicz, MS, of the Yale University School of Medicine in New Haven, Conn., and colleagues conducted their study to determine the radiation dose indexes for CT exams performed with renal colic protocols in the U.S., as well as how frequently reduced-dose techniques are used and institutional-level factors associated with high or low dose indexes.

Lukasiewicz and colleagues examined CT dose indexes at the institutional level for CT performed with renal colic protocols from the Dose Imaging Registry (DIR). Data gathered included 43,903 renal colic protocol examinations performed at 93 institutions from May 2011 to January 2013. The mean age of the study group was 49 and 53.9 percent of the patients were female.

A median of 268 CT studies was contributed by the institutions. The overall mean institutional dose-length product (DLP) was 746 mGy ⋅ cm, with an effective dose of 11.2 mSv. There was a range of 307 to 1,497 mGy ⋅ cm found in the data for mean DLPs. Only 1,010, or 2 percent, of the studies were performed with a DLP of 200 mGy ⋅ cm or less, and only ten percent, or nine of the institutions maintained DLP at 400 mGy ⋅ cm or less in at least 50 percent of the patients.

The researchers found that DLP was highly correlated with weight and body mass, but was loosely correlated with age and height.

“Our results suggest that reduced-dose techniques for renal colic protocol CT studies are underused, and dose indexes could likely be lowered substantially, particularly at institutions with very high mean dose indexes,” wrote the authors.

However, “Because patient populations vary considerably geographically and between healthcare settings, the adoption of reduced-dose protocols by a given institution needs to be evaluated in the context of the patient population it serves,” they added.