Organ Effective Modulation: Does it reduce radiation dose during CT?

As CT grows in popularity, radiologists around the world are working toward finding new ways to limit the amount of radiation patients receive during such examinations. Organ Effective Modulation (OEM), an automatic exposure control technique, can reduce radiation dose during CT without compromising image quality, according to a new study published in European Journal of Radiology.

Hiroyuki Akai, MD, PhD, Institute of Medical Science at the University of Tokyo, and colleagues studied data from 196 consecutive patients referred to their institution for thoracoabdominal CT on one specific scanner. All CT exams were performed with adaptive iterative dose reduction with 3D processing (AIDR-3D). The team then divided the patients into two groups—those who were scanned using OEM and those who were not—and compared radiation doses of the two groups.

Overall, the CTDI_vol for the OEM patients was more than 8 percent lower than the CTDI_vol of the non-OEM group.

“We believe that our 8 percent dose reduction is important because CT scans should aim for the lowest levels of radiation possible, consequently reducing the risk of radiation-induced carcinoma and leukemia,” the authors wrote.

This reduction, Akai and colleagues said, occurred “without affecting image quality or the diagnostic acceptability of the image.”

The data also revealed where image noise was reduced or increased, as a result of the OEM.

“At the thoracic level, image noise was significantly higher in the ventral air space in the OEM group,” the authors wrote. “No significant difference was observed at the other five measuring points at the thoracic level. At the abdominal level, image noises were slightly lower at all five measuring points in the OEM group, only achieving a statistical difference at the posterior segment of the right hepatic lobe.”

Akai et al. also noted that patients with higher body mass indexes (BMIs) had higher dose reductions.

The team did write that its study had limitations. For instance, the study population did not include any patients with a BMI of 30 or more who were scanned using OEM.

“We believe that this was only a minor limitation because our results indicated the effectiveness of OEM in higher-BMI patients,” the authors wrote.

Another limitation, according to the researchers, was that all exams were performed with AIDR 3D, making it “uncertain” if OEM reduces radiation when CT scans are performed by “other imaging algorithms such as filter-back projection.”