| Περίληψη: | Absolute quantification of I-131 activity in tumors and normal tissue is essential for internal dose estimates and is one of the greatest challenges in contemporary Nuclear Medicine. Therefore, for obtaining more accurate results, the most suitable and clinical applicable method, for both patients and scientists, for the quantification of I-131 has to be found. In the theoretical part of this project, the two methods for the quantitation are explained and analyzed as well as the factors that affect the obtained clinical image followed by the corrections that must be applied for gaining a more discrete image. For the planar technique, two methods for scatter and septal penetration correction were used applying two different matrix sizes specifically, 256x256 and 512x512 matrix sizes. On the other hand, for the SPECT technique, a 64x64 matrix size was used and a comparison between an auto-ROI and a same pattern of ROI segmentation that was produced manually for the purpose of this project, was performed. Furthermore, for patient specific dosimetry the total absorbed dose for the thyroid gland was calculated. Figures and tables for planar and SPECT technique were produced for each matrix size along with the final curve of the absorbed dose of the patient. For the planar technique it was observed that the method proposed by Anne Larsson, according to statistical analysis, gives results with lower statistical errors than the method proposed by Macey. In addition, 512x512 matrix size for the planar technique leads to lower statistical errors when compared with the results from using the 256x256 matrix size. Moreover, for the SPECT technique, the auto-sum that the software of the camera provides gives exactly the same results compared with the manual-sum. Finally, the total thyroid absorbed dose was 45,0472 Gy a result very close to the ICRU proposed dose value.
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