Organ-based tube current modulation: are women's breasts positioned in the reduced-dose zone?

PURPOSE To retrospectively determine the potential of organ-based tube current modulation ( OBTCM organ-based tube current modulation ) to reduce the radiation dose delivered to breast tissue by computed tomography (CT) by determining breast angular position in relation to the zones of decreased versus increased radiation. MATERIALS AND METHODS The authors obtained institutional review board approval for this study and patients' written informed consent. In two academic centers (center A: Beth Israel Deaconess Medical Center, Boston, Mass; and center B: Hôpital André Vésale, Montignies-le-Tilleul, Belgium), data were collected from clinical thoracic CT examinations performed in 498 women (mean age, 60 years; age range, 18-95 years) in the supine position and 34 women (mean age, 53 years; age range, 18-84 years) in the prone position. One radiologist in each center determined breast tissue location and measured its inner and outer boundaries with respect to the isocenter of the CT examination. The percentages of women with breast tissue within and those with breast tissue outside the zone of decreased radiation delivered by OBTCM organ-based tube current modulation were determined. The location of breast tissue was correlated with patient age and with sagittal and coronal diameters of the thorax by using the Student t test, Fisher exact test, and Pearson correlation. RESULTS None of the women lying in the supine position had the entirety of the breast tissue located within the reduced-dose zone. Breast tissue was located in the increased-dose zone in 99% of women lying supine and in 82% of women lying prone. CONCLUSION The breast angular position of almost all women was higher than the angular limit of the reduced versus the increased dose in OBTCM organ-based tube current modulation . No woman, regardless of supine or prone position, had all breast tissue within the reduced-dose zone.