What is it about?
Methods. Scan parameters of 90 patients undergoing retrospective electrocardiographic gating spiral CCTA exam were recorded during a period on a single-source 64-MDCT and a dual-source 128-MDCT, and average scan parameters were derived that were used for dosimetry. The computed tomography dose index (CTDI) with a pencil ionisation chamber and polymethyl methacrylate body phantom with diameter of 32 cm was measured on both scanners. The dose–length product (DLP) was calculated and the DLP to effective dose conversion factor (for chest scan at 120 kV of 0.014 mSv mGy–1 cm–1) was used to estimate effective dose (ED).
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Why is it important?
Results. Patients' heart rate, scan length, pitch factor, CTDIv, DLP and ED for 128-MDCT were 64 (5) (beats min–1), 161 (10) (mm), 0.26, 47 (12) (mGy), 769 (212) (mGy cm) and 10.3 (3.1) (mSv), respectively [mean (one standard deviation)]. Patients' heart rate, scan length, pitch factor, CTDIv, DLP and ED for 64-MDCT were 60 (7) (beats min–1), 172 (14) (mm), 0.2, 60 (6) (mGy), 1068 (98) (mGy cm) and 14.9 (1.4) (mSv), respectively.
Perspectives
Conclusion. Our results indicated that the CTDIv, DLP and the effective dose with 128-MDCT is significantly lower than with 64-MDCT (p < 0.05). As differences between the exposure parameter mAs on two CT scanners was not significant (p > 0.05) and the kV was constant for both scanners (120 kV), the differences resulted from a shorter scan length on the 128-MDCT and use of a higher pitch factor (0.26 and 0.2 in the 128-MDCT and 64-MDCT, respectively). Comparison with other published studies confirms the findings and indicates methods for reducing patient dose.
Daryoush Khoramian
Tarbiat Modares University
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This page is a summary of: Estimation and comparison of the radiation effective dose during coronary computed tomography angiography examinations on single-source 64-MDCT and dual-source 128-MDCT, Journal of Radiological Protection, September 2017, Institute of Physics Publishing,
DOI: 10.1088/1361-6498/aa823f.
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