Design of an Adjustable Anti-Scatter Grid for Tomosynthesis Mammography

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Date
2013-12-02
Authors
Chen, X.
Cooke, S.F.
Grauer, S.J.
Xu, K.
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CancerCare Manitoba is preparing to transition its facilities from film mammography to full-field digital mammography. During this process, CancerCare Manitoba will evaluate the incorporation of tomosynthesis mammography into their breast cancer detection regime. CancerCare Manitoba's Division of Medical Physics is responsible for procuring and maintaining medical devices for the organization. Our team has been tasked with the conceptualization of an anti-scatter device that can be adapted to operate in commercially available tomosynthesis scanners. As the Department of Medical Physics has not yet selected a scanner for purchase, they requested our anti-scatter solutions be presented as general concepts. Anti-scatter devices eliminate X-rays that are scattered in breast tissue, while permitting primary X-rays to pass through. This filtration process dramatically improves the contrast of the X-ray image, but increases the radiation dose to the patient. The dose increase required to produce an X-ray image with a grid is called a Bucky Factor and the scatter reduction is captured in a contrast improvement factor. Together, these factors quantify grid performance and guide the selection of an anti-scatter device. Estimating the Bucky factor and contrast improvement factor is not within the scope of this report, but after close consultation with our client's representative, we selected three designs to present for CancerCare Manitoba's consideration. These designs have several common elements including the dimensions of the grid, the X-ray attenuation material (lead), and a Bucky. The Bucky is a device that moves anti-scatter grids back and forth perpendicular to the gridline alignment. This movement reduces the shadow of gridlines on the X-ray detector, improving the final image. Our first design is a reoriented permutation of traditional focused anti-scatter grids. In our design, the grid's attenuation lines are aligned with the moving X-ray source's path, reducing scatter while permitting primary X-rays to hit the detector. The gridlines are to be constructed using an additive lithographic process, and the grid is expected to cost $5,000. The second anti-scatter design presented in this report is a flexible adaptation of our reoriented grid. Since the X-ray source moves along an arc to preserve its distance from the breast […]

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