Shelley Wood

June 02, 2014

LAS VEGAS, NV — Increasing reports of left-sided malignancies among interventional cardiologists has prompted researchers in California to test whether the left side of the head does indeed receive more radiation than the right and whether a nonlead protective cap can help guard against exposure.

The findings provide some of the first real evidence that the left side of the brain is likely at increased exposure risk and that a lightweight cap may help.

Dr Ryan Reeves (University of California, San Diego) presented the results of the BRAIN study as a poster at last week's Society for Cardiovascular Angiography and Interventions (SCAI) 2014 Scientific Sessions .

For the study, investigators asked seven interventional fellows and four attending physicians to wear a barium sulfate and bismuth oxide cap (BioXR), an FDA-approved cap shown to reduce radiation exposure. Three dosimeters were placed on the outside of the cap—one each on the left, right, and center—and three more on the inside of the cap, mirroring the outside placements. Another dosimeter was placed outside the procedure room to control for ambient radiation.

Radiation measurements were taken with physicians wearing the caps for an average of 50 consecutive procedures, then cumulative radiation-exposure measurements were compared.

Three Key Findings

There were three key study findings, Reeves told heartwire . The first was that radiation exposure was twice as much on the outside left and outside center of the cap as on the right side of the cap, a highly statistically significant difference. "This is the first time it's been shown that the left side of the head receives more radiation during invasive procedures than the right," Reeves said.

Dr Ryan Reeves

Moreover, dosimeters on the inside of the cap picked up radiation levels that were 55% lower than those on the corresponding outer surface of the cap, with the exception of the right-sided dosimeters, which picked up similar levels of radiation on the inside and outside of the caps.

"These findings suggest that this cap does have the ability to significantly attenuate the exposure, so that's . . . a very easy way to protect the brain from radiation exposure that may be responsible for these very rare left-sided glioblastomas," Reeves said. Of note, the relative increase in cumulative exposure within the cap was 9% higher than the control dosimeter placed outside the room.

In a third and provocative finding, Reeves et al showed that the supervising physicians received higher radiation exposure to the left and center cranium than the trainees.

"The standard [thinking] is that the primary operator gets the most radiation exposure," because he or she is usually standing closer to the patient, senior author Dr Ehtisham Mahmud (University of California, San Diego) explained. "Our findings [suggest] that the attending physician, who is primarily a secondary operator in a teaching institution, is getting greater radiation to the head per case."

Their working theory, Reeves added, is that radiation shielding in catheterization labs is typically designed to protect the primary operator. As a result, the secondary operator gets more radiation scatter. Backing up that hypothesis, dosimeters in the caps of taller physicians tended to pick up higher radiation levels to the left and center locations than was seen in their shorter colleagues.

Despite the growing concern about the risk of left-brain malignancies, interventionalists often leave their heads unprotected because existing protection—lead caps or leaded-glass shields—are too heavy, Mahmud noted.

This cap, however, weighs just under 150 g, and the physicians wearing it, Reeves said, "didn't even notice it was there."

BioXR Corp supplied the caps for the study. Neither Reeves nor Mahmud had any financial conflicts of interest.

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