Modeling Gamma Ray Penetration in a
Variable-Angle Slant-Hole (VASH) Collimator
Student: Bethany Wissmann
School: University of Virginia
Mentored By: Seung Joon Lee and Drew Weisenberger
Three dimensional molecular breast imaging (MBI) uses radioisotope labeled molecules to provide positional information about breast cancer lesions but traditionally requires multiple, or moving, gamma cameras for complete angular sampling. The VASH collimator replaces the typical parallel-hole collimator in a gamma camera, making three dimensional MBI more feasible. The angle of the collimator changes continuously within a limited specified angle range, providing multiple image projections, but using a single stationary camera. These projections, though not covering 180 degrees, can be reconstructed into a useful three dimensional image. A penetration model was designed to aid in the creation of the image reconstruction algorithm for a gamma camera utilizing the VASH collimator. The gamma ray penetration through the collimator was modeled using MATLAB. In addition to the expected spike in penetration at the gamma radiation source position, the model also showed increasing intensity of penetration at the edges of the collimator, showing that the gamma camera will likely detect radiation in these areas which needs to be accounted for by the reconstruction algorithm to accurately represent the radiation-source position, and thus lesion position.