Exposure Determination in Gamma-Ray Radiography for Mammography Applications

Previous studies explored the feasibility of using gamma-ray as an alternative to X-ray in medical imaging. The feasibility studies reported that gamma radiography could be an effective alternative to X-ray radiography. Exposure is the factor that decides noise level and contrast quality in the produced image; the two crucial factors for the diagnosis and patient safety. This research aims to foster the feasibility of gamma-ray mammography by proposing a method for exposure determination. Geant4 Application for Tomographic Emission toolkit was used to simulate the required exposure on the American College of Radiology Mammography phantom using photon energies of 17.5, 19, 20, 22, 23.5, 25, 26, 27.5, and 30 keV. The quality of the produced image was evaluated against a reference experimental X-ray mammographic image. A visual assessment procedure was adopted to determine the minimum contrast-to-noise ratio required to detect the various sets of phantom features. Based on the visual assessment, a method for exposure determination was established and verified. The results will support the application of radioisotopes for mammography.