Better 3D Imaging of the Breast with Less Radiation
A new device may enable breast cancer imagers to provide up to six times better contrast of tumors in the breast, while halving the radiation dose to patients.
In breast cancer screening, imaging based on nuclear medicine is currently being used as a successful secondary screening alongside mammography to reduce the number of false positives. Now, researchers are hoping to improve this imaging technique, known as molecular breast imaging or breast specific gamma imaging, by adding a new type of collimator - the variable angle slant hole collimator - to allow better image quality and precise location (depth information) within the breast.
When used in a molecular breast imager, the variable angle slant hole collimator allows the imager to capture 3D molecular breast images at higher sensitivity than current 2D scans. It provides up to six times better contrast of tumors in the breast, while maintaining the same or better image quality and halving the radiation dose to patients.
In breast cancer screening, imaging based on nuclear medicine is currently being used as a successful secondary screening alongside mammography to reduce the number of false positive results rendered by mammography alone. While a mammogram uses X-rays to show the structure of breast tissue, molecular breast imagers show tissue function. For instance, cancer tumors are fast growing, so they gobble up certain compounds more rapidly than healthy tissue. A radiopharmaceutical made of such a compound will quickly accumulate in tumors and can be spotted by the molecular breast imager. Current molecular breast imaging systems use a traditional collimator, which is essentially a rectangular plate of dense metal with a grid of holes, to “filter” the gamma rays for the camera for a clear, well-defined image of any cancer tumors. The variable angle slant hole collimator, or VASH collimator, is a new collimator developed and patented for 3D imaging of the breast by researchers at the Department of Energy's Thomas Jefferson National Accelerator Facility, Dilon Technologies and the University of Florida Department of Biomedical Engineering. It is constructed from a stack of 49 tungsten sheets, each one a quarter of a millimeter thick and containing an identical array of square holes. The angle of the array of square holes in the stack can be easily slanted by two small motors that slide the individual sheets by their edges. The result is a systematic varying of the focusing angle of the collimator during the imaging procedure. In system tests, the development team found that while using the VASH collimator with an existing breast molecular imaging system, they could get six times better contrast of tumors in the breast, which could potentially reduce the radiation dose to the patient by half from the current levels, while maintaining the same or better image quality. The test results match a published paper that predicted this performance via a Monte Carlo simulation.
Thomas Jefferson National Accelerator Facility
The collimator was built at Jefferson Lab and the test results were analyzed at the the University of Florida Department of Biomedical Engineering with funds provided by a Commonwealth Research Commercialization Fund grant from the Commonwealth of Virginia’s Center for Innovative Technology, and with matching support provided by Dilon Technologies.
D.R. Gilland, B.L. Welch, S. Lee, B. Kross, and A.G. Weisenberger, “Evaluation of a novel collimator for molecular breast tomosynthesis.” Med. Phys. 44, 5740 (2017). doi:10.1002/mp.12564