64VCT를 이용한 관상동맥 검사시 z-axis Automatic CT tube current modulation을 통한 방사선량 감소방안에 대한 연구

A Study on the Reduction of Radiation Dose When Examining Coronary Artery through CT Tube Current Modulation Employing 64VCT

Purpose This study is intended to examine the reduction method without the decrease in the quality of image through automatic CT tube current modulation when examining coronary artery employing 64VCT. Materials and Methods The object is 200 coronary artery examination patients using 64VCT reorganized as Auto mA group and Manual mA group, with 100 patients in each group from March 29th, 2007 to 24th October, 2007. 125 men and 75 women were selected for this study, and the patients’ average age was 54.27±10.3, and their BMI was 23.7±2.7. 5 minutes prior to the examination a spray-type NTG was injected onto the patients. β-blocker was injected 1 hour before the examination for the patients with irregular heart beat, and it was adjusted at under 65bpm. Light Speed VCT from GE was used accompanied by the alignment of ECG. Time Bolus was checked first using Smart Prep, and the segment setup was made by Scan Parameter as Scan Type: Cardiac(Helical), Cardiac Mode: BPM 30-75. Manual mA was set at .35 sec rotation time, 40mm detector coverage, .625mm thickness, .2:1~.24:1 pitch, 120kyp, 650mA. Auto mA was fixed between 300-700mA, and the rest conditions are the same as Manual mA. Contrast media and saline solution were injected on ante-cubital vein before scanning using Time Bolus, at 4.0/15cc and 4.0/20cc on Ao. Peak Check, and on Cardiac Scan, contrast media(Ultravist 370) and saline solution were injected at 4.0/80cc and 5.5/50cc following the order. After scanning, image of coronary artery was reconstructed, SD and CTDIvol displaying on the exam monitor using Axial image was measured in groups, and Automatic mA and Manual mA groups were compared and assessed. Results The object was a total of 200 patients divided into 125 men and 75 women. Auto mA group’s values were SD34.29±9.5 and CTDIvol 75.15±19.2, and Manual mA group’s values were SD30.7±6.7 and CTDIvol 91.2±7.6. When compared, Radiation Dose was decreased by 18%. Conclusion When SD and CTDIvol were assessed in separate groups, there was not evident difference in the quality of in1age between Auto mA group and Manual mA group, but the radiation dose was decreased by 18% on Auto mA condition.