Measurement of image quality and radiation dose of compressible breast phantoms in mammography

Autor: Ting-Yin Wang, 王亭尹
Rok vydání: 2018
Druh dokumentu: 學位論文 ; thesis
Popis: 106
Purpose At present, the rigid-type breast phantoms are frequently used for assessments of image quality and radiation dose in mammography. These breast phantoms cannot accurately simulate imaging factors, image quality, and radiation dose under clinical compression procedures in digital breast tomosynthesis (DBT). The purpose of this study is the measurement of image quality and radiation dose in DBT using compressible breast phantom. Materials and methods The DBT system (Selenia Dimensions, Hologic) was used in this study. The contrast-detail mammographic phantom (Artinis CDMAM 3.4) and the thermoluminescent dosimeter TLD-100 microcubes (Harshaw/Bicron, Solon, OH) were used for measuring image quality and radiation dose, respectively. To measure the image quality, 4-8 cm Bolus phantoms (MT-CB-410S, CIVCO, Medical Solution, France) with the CDMAM were irradiated and the CDMAM images were constructed with FFDM and SM mode. These CDMAM images were read and scored by three observers. To measure the radiation doses, 3-10 cm Bolus phantoms with 50 microcubes of TLD-100 were irradiated under FFDM and DBT modes. The TLDs were placed in the different depths of the Bolus phantoms for the assessment of depth dose distribution. In the clinical compression applications, the 4-8 cm Bolus phantoms with TLDs were compressed with forces of 58.8-156.8 N. The depth of each TLD in the Bolus phantom was investigated using the sectional image of DBT and the dose of each TLD was measured. Results In the assessment of image quality, the correction observation ratios of CDMAM images of FFDM was those of CDMAM images of SM mode. For example, the correction observation ratios of CDMAM images with the 6-cm Bolus phantom for FFDM and SM modes were 49.4% and 35.1%, respectively. In the assessment of radiation dose, the measured dose decreased with the increasing depth of TLD. For example, the measured doses of TLDs in the 6-cm Bolus phantom for FFDM and DBT modes were 0.61-5.46 and 0.92-5.55 mGy, respectively. In the clinical application, the depth of TLD decreased with the increasing compression forces. The measured doses of TLDs around the central layer were comparable to the average glandular dose (AGD) of the compressible breast phantoms. Conclusion Results from this study demonstrated that the image quality of FFDM is superior to that of SM for a compressible breast phantom with large thickness. We also observed that the impact on radiation doses caused by changing compression forces is significant for a compressible breast phantom with large thickness. Therefore, the Bolus phantoms and TLD-100 microcubes are suitable for the measurements of the image quality and radiation dose in different clinical DBT applications.
Databáze: Networked Digital Library of Theses & Dissertations
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