AbstractID: 7164 Title: The Potential for Breast CT
Mammography is an effective screening procedure for breast cancer; however, the
median lesion diameter at detection is 11 mm. Dedicated CT screening for breast cancer
is alternative that can potentially provide greater sensitivity at similar dose levels of a
two-view screening mammography exam. In dedicated breast CT, only the breast is
scanned, with gantry rotation in the coronal plane and the x-ray source rotating around
each breast. Monte Carlo techniques were used to assess the radiation dose to the breast.
A total of 107 x-ray photons at energies from 10 keV to 140 keV at 1 keV intervals were
followed, and energy deposition was tracked. A polyenergetic tungsten anode x-ray
spectral model was used. Dose to the breast at constant SNR was computed from 30 kVp
to 140 kVp in 5 kVp intervals, and converted to Computed Tomography Dose Index
(CTDI). For subjective assessment, a cadaver breast was scanned at 80 kVp using 1 mm
contiguous slices of 0.3 x 0.3 x 1.0 mm voxels. The CTDI at the center of a 10 cm
diameter breast of 50% glandular/ 50% adipose tissues was 6.1 mGy/100 mAs at 80 kVp.
A reference SNR acceptable in terms of image quality required 63 mAs, resulting in a
glandular dose of 3.87 mGy, comparable to a two-view screening mammogram. Images
of the cadaver breast at 80 kVp and 63 mAs showed impressive detail of the breast
parenchyma and ductal structure. Dedicated CT of the breast may provide a doseefficient technique for breast cancer screening.