Bras increase effect of dose reduction in chest CT

Wearing a bra during chest CT increases the percentage of breast tissue within the region of reduced tube current and therefore improves the performance of angle-dependent tube current modulation technique, according to a study published in the May issue of the American Journal of Roentgenology.

The glandular tissue of the female breast is more susceptible to radiation exposure than other tissues, which is troubling given that radiation exposure is regarded as a potential source of cancer induction. Because many institutions have adopted the standard practice of instructing female patients to remove their bras before undergoing chest CT, lead author Anna Seidenfuss, of the University Erlangen-Nuremberg in Germany, and colleagues assessed the proportion of the female breast and glandular tissue that is within the range of angle-dependent tube current modulation and whether the proportion could be optimized by keeping the bra on.

The study included 578 female patients who were undergoing chest CT and were divided into two groups: group A that was comprised of 209 patients who were prospectively examined wearing a bra and group B featuring the remaining 369 that acted as the control group and were scanned using the previous standard. The two groups were also subdivided according to cup size.

An angle-dependent tube current modulation that reduces the tube current for anterior tube position to minimize direct exposure to anteriorly located organs was used by the researchers. The proportion of breast and glandular tissue located within and outside the region of tube current reduction was assessed.

In group B, 60.4 percent of total breast tissue and 67.1 percent of glandular tissue was inside the region of tube current reduction. The proportions significantly improved in group A, increasing to an average of 91.3 percent and 96 percent, respectively. Diagnostically relevant artifacts were not introduced in any of the patients. Patients’ age was correlated with this effect, and higher rates of improvement were seen in the older patient group.

Angle-dependent tube current modulation was most effective in patients with cup size A while wearing a bra. In that group, 97.5 percent of breast tissue and 98.1 percent of glandular tissue was inside the region of tube current reduction. Women with a cup size of E had the largest effect of wearing a bra, as the rate of breast tissue that was affected by angle-dependent tube current modulation increased from 30 percent to 83.3 percent. Glandular tissue increased from 31.8 percent to 90 percent.

“We have shown in a large patient cohort that 'placement' of the female breast by keeping a brassiere on during chest CT does not negatively influence image quality but increases the effect of dose reduction of angle-dependent tube current modulation algorithms,” wrote Seidenfuss and colleagues.