| Summary: | 碩士 === 元培科學技術學院 === 影像醫學研究所 === 96 === American College of Radiology (ACR) has stipulated that each mammography exposure to have an Average Glandular Dose (AGD) of less than 3mGy on a standard phantom. However, clinical Full-Field Digital Mammography (FFDM) use has resulted in AGD between 1mGy and 7.5mGy. Based on the principle of As Low As Reasonably Achievable (ALARA), this research project aims to evaluate the impact of filter and voltage exposure parameters on breast AGD.
We used FFDM with Mo cathode and Mo/Rh filter. In total we had 8 acrylic filters of 10x10x2cm and 10x10x0.5cm phantoms to evaluate the AGD. We observed and recorded the outcome of using Mo/Rh filter with variable tube voltage and acrylic thickness, and extended this observation to clinical test subjects. By using Automatic Exposure Control (AEC) and manual dose adjustments we evaluated the differences in AGD thereby clinically reducing the effective dose.
Our results showed that it is possible to reduce AGD of the phantom by 20% to 41% by using filters and tube voltage adjustments with AEC. Correspondingly, in clinical use AGD can be reduced by 42% to 51%. The effective combined use of filter/voltage exposure can help reduce AGD to achieve ALARA.
If this research was broadly extended, the use of different thickness of phantoms (different densities), under different tube voltage parameter to test for AGD, the density can then be inferred. In this manner the clinician is then able to assess the breast density.
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