Abstract
Aim. To determine absorbed radiation dose (ARD) in radiosensitive organs during prospective and full phase dose modulation using ECG-gated MDCTA scanner under 64- and 320-row detector modes. Methods. Female phantom was used to measure organ radiation dose. Five DP-3 radiation detectors were used to measure ARD to lungs, breast, and thyroid using the Aquilion ONE scanner in 64- and 320-row modes using both prospective and dose modulation in full phase acquisition. Five measurements were made using three tube voltages: 100, 120, and 135 kVp at 400 mA at heart rate (HR) of 60 and 75 bpm for each protocol. Mean acquisition was recorded in milligrays (mGy). Results. Mean ARD was less for 320-row versus 64-row mode for each imaging protocol. Prospective EKG-gated imaging protocol resulted in a statistically lower ARD using 320-row versus 64-row modes for midbreast (6.728 versus 19.687 mGy, P < 0.001), lung (6.102 versus 21.841 mGy, P < 0.001), and thyroid gland (0.208 versus 0.913 mGy; P < 0.001). Retrospective imaging using 320- versus 64-row modes showed lower ARD for midbreast (10.839 versus 43.169 mGy, P < 0.001), lung (8.848 versus 47.877 mGy, P < 0.001), and thyroid gland (0.057 versus 2.091 mGy; P < 0.001). ARD reduction was observed at lower kVp and heart rate. Conclusions. Dose reduction to radiosensitive organs is achieved using 320-row compared to 64-row modes for both prospective and retrospective gating, whereas 64-row mode is equivalent to the same model 64-row MDCT scanner.
Highlights
Multidetector computed tomography angiography (MDCTA) is uniquely suited to study cardiac anatomy and coronary artery disease (CAD) in a noninvasive manner and may even provide additional prognostic information to the baseline risk stratification [1]
Linear mixed effects models were fitted to study the effects of tube voltage and heart rate variation on absorbed radiation dose (ARD) while adjusting for all other imaging factors (Tables 2 and 4)
The reduction of kVp from 135 to 100 kVp for prospective ECG gated MDCTA performed on Protocols 320-row mode 64-row mode Protocols 320-row mode 64-row mode kVp 100 10.98 14.47
Summary
Multidetector computed tomography angiography (MDCTA) is uniquely suited to study cardiac anatomy and coronary artery disease (CAD) in a noninvasive manner and may even provide additional prognostic information to the baseline risk stratification [1]. The high sensitivity (85%–95%) and specificities (83–90%) of the newer generation scanners have already been documented [2, 3]. The high negative predictive value to rule out coronary artery disease (CAD) has prompted current European Society of Cardiology guidelines on management of stable angina to recommend MDCTA for patients with a low pretest probability of CAD and inconclusive stress testing [4]. As MDCT is considered a major source of ionizing radiation in medicine, further in depth study of radiation exposure with these new scanners is paramount [8, 9]
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