| Summary: | 博士 === 國立陽明大學 === 生物醫學影像暨放射科學系 === 101 === The aim of this dissertation was to establish the relationship between the optimum imaging scanning parameters and radiation dose on coronary artery calcium quantification with 64 and 320 multi-detector computed tomography (MDCT) by using an anthropomorphic cardiac phantom. Three score methods, first is Agaston, which used electron beam CT (EBCT) for the quantification of cardiac artery calcium score (CACS) in 1990, together with volume (1998) and mass (2002) score are necessary for quantification. According to the literature, mass score is more robust than others, but a calcification factor is required. First, all the simulations of the CT examinations with the Rando and polymethylmethacrylate phantoms (PMMA) embedded thermoluminescence dosimety, (TLD-100H) with different weights: 90, 70, 50, 30, and 10 kg, which were conducted using a 64-detector row CT scanner (Aquillion 64, Toshiba Medical Solutions, Japan) to evaluate the relationship between the radiation dose and different weights. The measurement results show that effective doses (E) of CT examinations involving patients weighting from 90 to 10 kg range from 7.72 ± 1.41 to 14.5 ± 2.61 mSv. The E decreased exponentially in an inverse correlation with increasing patient weight. A simple equation of effective dose relative to different body weight was fitted and can be used as advisory for radiation protection and assessment in Taiwan. Then the calcification factor was developed by using homemade Matlab algorithm to calculate the cardiac calcium score. At the end, the scan mode, regardless of sequential or spiral scan, slice thickness, field of view (FOV), kVp, mAs and reconstruction algorithm, was used to figure out the relationship between the optimum scanning parameter and the radiation dose by using a cardiac QRM phantom.
Lower-dose imaging protocols were sequential scan with 3 mm slice thickness, 150 × 150 mm2 proposed for optimization with the parameters of 120 kVp and 10 mAs for small-size (0.336 mSv) of 64 MDCT, (0.2 mSv) of 320 MDCT and 120 kVp, 80 mAs for medium-size (2.73 mSv) of 64 MDCT, (1.58 mSv) of 320 MDCT. It has a good potential to use these suggested lower-dose protocols in the clinical use for early finding of the coronary disease without sacrificing the diagnostic accuracy.
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