III this study we theoretically investigated the minimum scan time of an invel'se-geornetry dedicated breast CT system that provides sufficient sampling and dose equivalent to mammography without exceeding the lirnits of source power or detector count rate. The inverse geometry, which utilizes a large-area scanned source and a narrower photon-counting detector, is expected to have improved dose efficiency compared to cone-bealll methods dne to reduced scatter effects and improved detector

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... ency. The analysis assumed the specifica(;ions of available inverse-geometry source and detect.or hardware (SBDX, NovaRay, Inc, Newark CA). The scan time was calculated for a 10, 14, and 18-crn diameter breast composed of 50% glandular / 50% adipose tissue. The results demonstrate a minimum scan time of 6.5, 14.3, and 14.7 seconds for a 10, 14, and 1S-cm-diameter breast, respect.ively. The scan times are comparable to those of proposed cone-beam systems. For all three breast sizes, the scan time was limited by the detector count rate. For example, for the iLl-cm-diameter breast, the minimum scan time that met the source power limitation was 1.1 seconds, and the rninimum scan time that achieved sufficient sampling was 0.8 seconds. The scan time can be reduced by increasing the detect.or count rate or area. Effective bowtie filters will be required to prevent detector saturation at the object edges. Overall, the results support preliminary feasibility of dedicated breast CT with an inverse geometry.