The use of abdominal MRI doubled over the past eight years, partly due to concerns about ionizing radiation inherent to other exams such as CT. As awareness about the potentially harmful effects of imaging spreads, providers have switched to non-ionizing modalities, particularly for conditions such as Crohn’s disease that require frequent imaging.

Vinit Baliya, MD, research fellow at Massachusetts General Hospital, presented the results of a retrospective study examining trends in Crohn’s disease imaging at RSNA 2016 in Chicago.

Baliya and other researchers from Harvard Medical School found a nine-fold increase in the use of MR since 2006, with no significant change in the usage rate for CT. These trends held true for all age groups and for all stages of treatment, except the initial diagnosis.

As it turns out, the switch to MR is reducing dose, with average dose length product (DLP) decreasing from 988 mG/year to just under 400 mG/year. Baliyan noted a divide in modality usage for complications, saying that MR is better for perforation and obstruction injuries while CT is more useful for abscesses.

These trends in patients with Crohn's matched non-disease-specific utilization rates in abdominal imaging, albeit at a less magnified rate. According to fourth year radiology resident Sarah Kamel, MD, of Thomas Jefferson University in Philadelphia, MR utilization merely doubled overall and CT remained stable.

While high-cost scans like CT and MR are almost always performed by radiologists, non-radiologist physicians have been reading simpler and cheaper modalities, according to Kamel.

“Ultrasound was the most-used modality by non-radiologist physicians, who consistently performed around 30 percent of all abdominal ultrasound exams,” said Kamel. “The majority of non-radiologist exams were in outpatient settings.

A major contributor to the lack of growth in CT was the 2011 bundling of certain abdominal CT scans, significantly reducing the relative value units attributed to radiologists compared to the separate billing codes.

“Abdominal imaging is now largely driven by CT and ultrasound, and code bundling in 2011 had a large impact on utilization rates,” concluded Kamel.