| Summary: | 碩士 === 元培醫事科技大學 === 醫學影像暨放射技術系碩士班 === 105 === The incidence and mortality of breast cancer is increasing in recent years. Mammography provides high resolution and contrast, increasing the imaging accuracy that can improve the effectiveness of breast cancer screening. Image quality and dose evaluation of skin and surrounding organs for mammography is relative important. The purpose of this paper is to evaluat the of skin and surrounding organs for mammography, and the experiment with different mAs and kVp, influence of scattering effect on image contrast.
The usage of mammography to examine breast tissue, the TLD (Thermo lummescent detectors) were distributed in the skin, thyroid and other organs tissues of the prosthesis surface for dose measurement. To evaluate the images that mentioned in the Nuclear Associates 18-220 prosthesis with the different mAs and kVp dose irradiation prosthesis, to find out the best image contrast.
American college of radiology has stipulated that each mammography exposure to have an AAD (average absorbed dose) of less than 3mGy on standard phantom. After the experiment get the dose and the danger degree, find that each mammography exposure used has resulted in AAD between 1.36 mGy~1.74 mGy, and the increase in kVp, the AAD will drop. According to the measurement results, the radiation dose on the surface of the skin around the breast is the highest, the dose of the armpit lymphatic and thyroid surface is the second, and the surface dose of the distal part of the eye is lower with dose within the tolerated level.
After the experiment, we can find in the case of fixed kVp, the mAs can determine the dose. If were asked to wake the contrast better, it is necessary to increase the mAs. On the other hand, if the mAs were fixed and the kVp is higher such that the attenuation of the radiation through the object is reduced and increasing the resolution. That is to say, appropriate adjustment of kVp and mAs can obtain better mammography images.
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