| Summary: | 碩士 === 國立陽明大學 === 醫學工程研究所 === 91 === There are several clinical devices being used for measuring radiation dose, such as ion chamber, TLD, or radiographic film, etc. But there are some difficulties in utilizing these devices to get three-dimensional absorbed radiation dose distribution directly. On the contrary, the MRI-Fricke-infused gel dosimetry is a useful tool for conformal and three-dimensional absorbed radiation dose distribution measurements.
In the past we used MRI-Fricke-infused gel to simulate the human body and to measure radiation dose with magnetic resonance imaging. Nowadays the Fricke-gel dosimetry has been widely applied in stereotactic radiosurgery, IMRT, LINAC, brachytherapy, etc. dose measurement. However, it was found that the longer time MRI acquisition takes, the more severe ferric ion diffusion effects, which results in the error of dose measurement. A straightforward solution is to use faster MRI scanning methods to acquire images.
In this study, we examine the optimal parameters of the three-dimensional fast spin echo（3-D FSE）, combined with the intensity-based method for analyzing three-dimensional absorbed radiation dose distribution. The use of 3-D FSE parameters can greatly reduce MRI acquisition time and image slice thickness. The results reveal that 3-D FSE pulse sequences can accomplish three-dimensional imaging in 10 to 20 minutes, during which time ferric ion diffusion effects can be ignored, thus enabling an accurate absorbed radiation dose measurement.
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