Dual Source CT에서 High-pitch Cardiac Scan Mode를 이용한 관상동맥 검사의 유용성

The Usefulness of Prospectively ECG Gated High-pitch Cardiac Scan for CT Coronary Angiography Using Dual Source CT

Purpose To evaluate the usefulness of prospectively ECG gated high-pitch cardiac scan for CT coronary angiography(CTCA) using dual source CT by analyzing the dose effect and image quality for CTCA protocols. Materials and methods CTCA was performed by using 5 current clinical protocols to evaluate effective dose and organ dose in prima1y beam area with anthropomorphic female phantom and glass dosimetric system. Also, ACR phantom was used to analyze image quality at 128 channel multi-detector CT (scan parameters: 320 mAs at 120 kVp, collimation: 128 × 0.6 mm, scan range :137 mm, reconstructed slice thickness 0.6 mm, increment 0.4 mm). Heart beat rate of phantom was maintained 60 bpm in ECG gating. In a retrospectively ECG gated helical scan mode was done with 280 msecgantry rotation time, 0.23 pitch. Peak dose was used without cardiac dose modulation (pulsing off mode). Peak dose was adopted in range of 60%~80% of R-R interval and 25% reduction in others with cardiac dose modulation (pulsing manual mode). And peak dose was adopted in range of 60%~80% of R-R interval and 4% reduction in others with cardiac dose modulation (pulsing MinDose-manual mode). In a prospectively ECG gated sequential scan mode data were acquired at 70% R-R interval (middle diastolic phase in cardiac cycle), and 170 msec gantry rotation time was used. In a prospectively ECG gated high-pitch cardiac scan mode data were acquired from 60% R-R interval, and 3.4 pitch was used. Analysis of image quality was clone by evaluating objective noise, uniformity, high contrast resolution, and linearity. Results The mean effective dose for pulsing off mode without cardiac dose modulation in a retrospectively ECG gated helical scan was 20.8 mSv, and die mean organ dose of heart was 116.7 mGy. Pulsing manual mode showed 49% reduction, compared with that of pulsing off mode. And pulsing MinDose-manual mode showed 60% reduction compared with that of pulsing off mode. And at die adaptive sequential scan mode under prospective ECG gating die mean effective dose was 2.7 mSv, and die mean organ dose of heart was 17.5 mGy, d1is represents an 86% reduction compared with that of pulsing off mode. In the high pitch cardiac scan under prospective ECG gating die mean effective dose was 1.8 mSv, and the mean organ dose of heart was 10.3 mGy, this represents an 91% reduction compared with that of pulsing off mode. No differences in quantitative measures of linage quality were found between high pitch cardiac scan mode and others for noise, uniformity, high contrast resolution, linearity. Conclusion In patients with a low and stable heart rate, prospectively ECG gated high-pitch cardiac scan provides excellent image quality equivalent to retrospectively ECG gated helical scan-corelated acquisition but reduced effective dose.