This research aims to study gamma radiography feasibility in mammography through simulation. GATE simulation package was used to define the feasibility limits and to test several parameters including energy range, activity, source size and dose. An ACR-like mammography phantom was generated in simulation and the produced images were used for visual and analytical assessments. Some images were processed and enhanced by an application developed using the Visualization Toolkit. A special technique was developed to correct the gamma radiation field inhomogeneity and a morphological operator based technique was used to automatically extract regions of interest from the simulated images to estimate the contrast and signal-to-noise ratio. The results of the analytical and visual assessments demonstrated that gamma radiation of 35 keV energy or less produces acceptable mammography images. Higher energy photons produced mammography images but did not pass the rigorous clinical acceptable tests. The maximum feasible cylindrical source size was found to be 4 mm in diameter and 5 mm in thickness. An Am-241 source showed to produce acceptable mammography images in simulation using energy sensitive detectors with an average glandular dose of 1.2 mGy.

Each Medical Imaging system has features that are more suitable to be used in certain medical situations than other systems. This motivates the continuous development of imaging systems with better features and fewer drawbacks. Some of the drawbacks are related to the radiation energy. For instance, X-ray is widely used in many imaging modalities such as CT, fluoroscopy and mammography. The ability to control the beam energy is a process shared among all X-ray modalities, because X-ray is produced as a spectrum that includes undesired low and high energy photons. The low energy photons produced will not give useful diagnostic information and will contribute in unnecessary radiation dose to the patient. The high energy photons will contribute to the decrease in image contrast. This shortcoming is minimized by using certain types of filters In addition; X-Ray imaging systems are electronically complicated and require a high voltage generator to produce the beam as well as continuous maintenance. These drawbacks may be overcome by the use of gamma radiation instead of X-ray. Unlike X-ray, gamma radiation doesn’t require a generator or an electronically complicated system to produce the mono-energetic beam. These features of gamma radiation are advantageous in certain rough environments recently; gamma was used in several studies to produce clinically acceptable radiographic medical images. These studies suggested that better quality images could be obtained with the use of proper activity, an image enhancement system, and the use of a scattering removal technique. The main difference between mammography and conventional radiology is the useful energy range. Breast contains several soft tissues that have very similar attenuation properties. The attenuation difference between these soft tissues is higher at lower energies (10-15 keV) and becomes lower at higher energies (>35 keV. This means that the main challenges to utilizing gamma in mammography lies in finding a source that produced energy within or close enough to the mammography range

With Regards,
Sara Giselle
Associate Managing Editor
 Journal of Medical Physics and Applied Sciences