Evaluate the Influence of Heart Rate on Image Reconstruction and Dose Modulation undergoing Coronary Artery Computed Tomography Scan

• Main Authors: Ming-Horng Yeh, 葉銘宏
• Other Authors: Yung-Hui Huang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/89428274510385239347

碩士 === 義守大學 === 資訊工程學系碩士班 === 98 === Objective: The goal of this study is to investigate the influence of heart rate, the use of different reconstruction methods and dose modulation modes in coronary artery examination using 64-detector row computed tomography (MDCT) with retrospective ECG-gated technique; meanwhile, to optimize the procedure for better image quality and minimum radiation exposure. Materials and Methods: 60 subjects (male 37, female 23; age range 35 to 86 years; mean age 59.5 ± 11.2 years) with heart rate ranged from 46 bpm to 71 bpm (average 57.5 ± 8 bpm) were enrolled. To compare the effect of different reconstruction methods on subsequent image quality, quantitative analysis was carried out by calculating signal to noise ratio (SNR) and contrast noise ratio (CNR) for selected region of interest (ROI). Effective radiation doses were calculated with volume CT dose index (CTDI). Maximum tube current was modulated by ECG within the 30-80% phase and 50-85% phase for the patients with an average heart rate greater and lesser than 66 bpm, respectively. The relationships between the modulation modes and image quality were also analyzed. Results: Images reconstructed from patient with heart rate ranged from 49-71 (mean 63.7 ± 1.0) bpm and 46-55 (average 50.9 ± 0.5) bpm were obtained by using multi-segment reconstruction and half reconstruction, respectively. The improvement in image quality of right coronary artery (RCA), left anterior descending branch artery (LAD), and the left circumflex artery branches (LCX) is evident while using multi-segment reconstruction (p < 0.05). There was also a significant difference between calculated effective doses for retrospective ECG-gated CT angiography using 50-85% phase (15.6 mSv) and 30-80% phase (19.5 mSv) of ECG tube current control (ECG-M) (p <0.05). Conclusion: Through this quantitative study, we have demonstrated that different heart rate, image reconstruction methods, and dose modulation modes would affect image quality and radiation dose while performing retrospective ECG-gated 64-slice coronary CT angiography. In conclusion, if the heart rate could be controlled in 56-66 bpm, multi-segment reconstruction along with 50-85% dose modulation is preferred for achieving higher image quality and minimum radiation dose.