Anatomically adaptable automatic exposure control (AEC) for amorphous selenium (a-Se) full field digital mammography (FFDM) system

摘要

This paper will present new anatomically adaptable automatic exposure control (AEC), called Flex-AEC~+ , for amorphous selenium (a-Se) full field digital mammography (FFDM) system. The AEC operation is based on a principle where the imaging chain components are all modelled into the system software. Once the imaging parameters are all known it enables the system to exactly define the tissue composition imaged and utilize exposure parameters optimal for it. Based on the detected object composition together with the other imaging parameters the amount of signal produced by the amorphous selenium flat panel is exactly calculated and the desired dose of the exposure on the detector is thereby reached accurately. The AEC consists of 48 individual detection areas that cover a selenium flat panel area of 100 cm~2. It is therefore able to measure a well representative sample of the tissue to be exposed and adjust the exposure parameters optimal for the breast tissue composition. Clinical benefits of AEC are found because of fully understanding the behaviour of the x-ray beam together with the calculation models of the AEC. This gives better understanding of breast anatomy in all mammography screening and diagnostic cases, and responses to various tissue compositions by optimizing the image quality and dose. The spectrum of the x-ray radiation changes remarkably when passing through the various materials on its path. Optimal image quality and dose requires anatomically adjusted imaging parameters, which will represent the true breast tissue composition taking account in all different glandular tissue in the breast. Based on the detected object composition together with the other imaging parameters the amount of signal produced by the selenium flat panel is exactly calculated, and the desired image quality and dose is reached accurately.