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A Novel Approach for Effective Dose Measurements in Dual-Energy

dc.contributor.advisor Yoshizumi, Terry T
dc.contributor.author Mattison, Brett
dc.date.accessioned 2015-01-28T18:11:13Z
dc.date.available 2015-01-28T18:11:13Z
dc.date.issued 2014
dc.identifier.uri http://hdl.handle.net/10161/9448
dc.description.abstract <p><bold>Purpose:</bold></p><p>Our goal was to test a novel concept approximating organ dose measurements using the single mean energy of the two sources in dual-energy (DE) CT environment. Therefore, the purpose of this study was two-fold: (1) To obtain experimental validation of dose equivalency between MOSFET and ion chamber (as gold standard) under a dual-energy environment; (2) To estimate the effective dose (ED) using MOSFET detectors and an anthropomorphic phantom in DE CT scans.</p><p><bold>Materials and Methods:</bold></p><p>A commercial dual source CT (DSCT) scanner was employed for the study. The scanner was operated at 80kV/140kV (Sn added) using an abdomen/pelvis scanning protocol. A five-phase approach was used. Specific goals for each phase are as follows: (1) Characterize the mean energy from the combined clinical 80kV/Sn140kV beams; (2) Estimate the f-factor for tissues from the mean energy; (3) Calibrate the MOSFET detectors using the mean energy; (4) Validate MOSFET calibration with a CTDI phantom; (5) Measure organ doses for a typical abdomen/pelvis scan using a male anthropomorphic phantom and derive ED using ICRP 103 tissue weighting factors. For validation of dose equivalency, a MOSFET detector and ion chamber measured the dose at the center cavity of a CTDI body phantom. A student t-test was used to determine if the difference between the two was statistically significant.</p><p><bold>Results:</bold></p><p>The mean energy was calculated to be 67 kVp based on the corresponding spectra for the clinical DE beams. Using the Mean Energy Method, the tissue dose in the center cavity of the CT body phantom was 2.08 ± (2.70%) cGy with an ion chamber and 2.20 ± (4.82%) cGy with MOSFET respectively with a percent difference of 5.91% between the two measurements. The results (p = 0.15) showed no statistically significant difference. ED for DE abdomen/pelvis scan was calculated as 5.01 ± (2.34%) mSv by the MOSFET method and 5.56 mSv by the DLP method respectively.</p><p><bold>Conclusion:</bold></p><p>There has been no physical method to measure organ doses in DE CT scans. We have developed and validated a novel approach, the Mean Energy Method - for organ dose estimation in DE CT scans. ED from the anthropomorphic phantom compared well (within 11%) between the MOSFET method and DLP method.</p>
dc.subject Medical imaging and radiology
dc.subject Drosophila
dc.subject Dual Energy
dc.title A Novel Approach for Effective Dose Measurements in Dual-Energy
dc.type Master's thesis
dc.department Medical Physics


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