Abstract
AimTo investigate the potential of reducing the radiation dose in prospectively electrocardiogram-triggered coronary computed tomography angiography (CCTA) while maintaining diagnostic image quality using an iterative reconstruction technique (IRT).Methods and MaterialsProspectively-gated CCTA were first performed on a phantom using 256-slice multi-detector CT scanner at 120 kVp, with the tube output gradually reduced from 210 mAs (Group A) to 125, 105, 84, and 63 mAs (Group B–E). All scans were reconstructed using filtered back projection (FBP) algorithm and five IRT levels (L2-6), image quality (IQ) assessment was performed. Based on the IQ assessment, Group D(120 kVp, 84 mAs) reconstructed with L5 was found to provide IQ comparable to that of Group A with FBP. In the patient study, 21 patients underwent CCTA using 120 kV, 210 mAs with FBP reconstruction (Group 1) followed by 36 patients scanned with 120 kV, 84 mAs with IRT L5 (Group 2). Subjective and objective IQ and effective radiation dose were compared between two groups.ResultsIn the phantom scans, there were no significant differences in image noise, contrast-to-noise ratio (CNR) and modulation transfer function (MTF) curves between Group A and the 84 mAs, 63 mAs groups (Groups D and E). Group D (120 kV, 84 mAs and L5) provided an optimum balance, producing equivalent image quality to Group A, at the lowest possible radiation dose. In the patient study, there were no significant difference in image noise, signal-to-noise ratio (SNR) and CNR between Group 1 and Group 2 (p = 0.71, 0.31, 0.5, respectively). The effective radiation dose in Group 2 was 1.21±0.14 mSv compared to 3.20±0.58 mSv (Group 1), reflecting dose savings of 62.5% (p<0.05).Conclusioniterative reconstruction technique used in prospectively ECG-triggered 256-slice coronary CTA can provide radiation dose reductions of up to 62.5% with acceptable image quality.
Highlights
In the past decade, with the development of multi-detector spiral computed tomography (CT), coronary computed tomography angiography has increasingly become a noninvasive method of choice for the rule-out of coronary artery disease [1,2,3,4,5] owing to its high sensitivity
In the phantom scans, there were no significant differences in image noise, contrast-to-noise ratio (CNR) and modulation transfer function (MTF) curves between Group A and the 84 mAs, 63 mAs groups (Groups D and E)
For a given tube output, the Iterative reconstruction techniques (IRT) reconstruction algorithm yielded lower image noise compared to filtered back projection (FBP), with increasing levels of IRT offering increasing noise reductions in a linear manner (Figure 1)
Summary
With the development of multi-detector spiral computed tomography (CT), coronary computed tomography angiography (coronary CTA) has increasingly become a noninvasive method of choice for the rule-out of coronary artery disease [1,2,3,4,5] owing to its high sensitivity. Iterative reconstruction techniques (IRT) have been recently introduced, offering an innovative solution for reducing CT radiation dose. They can markedly lower image noise, effectively increase signal-to-noise ratio (SNR) and contrast-tonoise ratio (CNR), and achieve equivalent, or in some cases, better image quality (IQ) compared to routine-dose FBP reconstruction. The use of IRT has been investigated in coronary CTA, demonstrating radiation dose reductions in the range of 40–76% compared to FBP while retaining the image quality [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]
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