PURPOSE: To evaluate the feasibility of breast computed tomography (CT) in
terms of radiation dose and image quality.
MATERIALS AND METHODS: Validated Monte Carlo simulation techniques were use
d to estimate the average glandular dose (AGD). The calculated photon fluen
ce at the detector for high-quality abdominal CT (120 kVp, 300 mAs, 5-mm se
ction thickness) was the benchmark for assessing the milliampere seconds an
d corresponding radiation dose necessary for breast CT. Image noise was mea
sured by using a 10-cm-diameter cylinder imaged with a clinical CT scanner
at 10-300 mAs for 80, 100, and 120 kVp. A cadaveric breast was imaged in th
e coronal plane to approximate the acquisition geometry of a proposed breas
t CT scanner.
RESULTS: The AGD for 80-kVp breast CT was comparable to that for two-view m
ammography of 5-cm breasts (compressed breast thickness). For thicker breas
ts, the breast CT dose was about one-third less than that for two-view mamm
ography. The maximum dose at mammography assessed in 1-mm(3) voxels was far
higher (20.0 mGy) than that at breast CT (5.4 mGy) for a typical 5-cm 50%
glandular breast. CT images of an 8-cm cadaveric breast (AGD, 6.3 mGy) were
subjectively superior to digital mammograms (AGD, 10.1 mGy) of the same sp
ecimen.
CONCLUSION: The potential of high signal-to-noise ratio images with low ana
tomic noise, which are obtainable at dose levels comparable to those for ma
mmography, suggests that dedicated breast CT should be studied further for
its potential in breast cancer screening and diagnosis.