Breast dose during electron-beam CT: Measurement with film dosimetry

PURPOSE: To measure the breast dose and dose distribution from examinations performed with electron-beam computed tomography (CT). MATERIALS AND METHODS: Radiographic film was placed bilaterally at three depths in the breasts of an anthropomorphic phantom and exposed with clinically relevant protocols. The average breast dose and the dose distribution were obtained from the digitized and calibrated film and compared with those obtained with conventional CT. RESULTS: Breast doses from electron-beam CT chest, coronary artery calcium, and cardiac function examinations were 21.9, 2.87, and 1.55 mGy, respectively. Within the breast, the dose decreased linearly by a factor of three from the axilla to the sternum. The breast dose from a conventional CT chest examination ranged from 18 to 33 mGy and did not vary substantially across the breast. CONCLUSION: For chest examinations, the average breast dose from an electron-beam CT scanner was comparable to that from conventional CT scanners, despite the differences in dose distribution.