Nazli Shojaei Barjouei, Aghamiri Seyed Mahmoud Reza, Gholizadeh Sendani Neda, Shams Akhtari Amin
International Branch, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Department of Medical Technology, Faculty of Nuclear Engineering, Shahid Beheshti University, Tehran, Iran.
Radiat Prot Dosimetry. 2018 Feb 1;178(3):304-309. doi: 10.1093/rpd/ncx111.
Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effects over the patients. Therefore, estimating radiation doses absorbed during CCTA is important. In this study, we compared radiation dose and image quality by using three different retrospective electrocardiography (ECG) protocols. A total of 123 patients undergoing CCTA were divided in three different groups. We used full-dose modulation (CareDose4D) technique in group (1); fixed tube current 200 mAs for group (2); and in group (3), chest circumference was used to adapt tube current (180-200 mAs) and tube potential (100-120 kVp). For groups (1) and (2), tube potential adapted depends on body mass index (BMI) in which it was 100 kVp for BMI < 27 kg/m2, and 120 kVp for BMI ≥ 27 kg/m2. Quantitive assessment of image quality was calculated by measuring signal intensity (SI) and image noise (IN) in the proximal segments of aorta root on left and right coronary arteries. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also calculated by using SI and IN. Two experienced radiologists using a 4-point scale assessed the subjective image quality. Our results show that in group (1), the mean effective dose was 4.46 mSv (range: 1.75-8.6 mSv) and for group (2), the mean effective radiation dose was 5.07 mSv (range: 2.57-9.74 mSv) and in group (3), the mean effective dose was 5.85 mSv (range: 3.36-12.17 mSv). Group (1) representing 12% and 23% decrease in radiation dose comparing by groups (2) and (3). In multivariate analysis, adjusting for BMI, radiation dose for patients with BMI < 27 kg/m2 was significantly different; 2.53 mSv for group (1) compared to 3.54 mSv in group (2) and 5.207 in group (3) (p < 0.0001). In addition, lowering tube potential from 120 to 100 kVp in 200 mAs fixed tube current, represents 27% decrease in radiation dose. The quantitative image quality (IN, SI, SNR and CNR) was not statistically significant among the groups. To sum up, Retrospective-ECG gating may reduce radiation dose by using automatic tube current modulation and 100kVp tube potential with preservation of image quality in patient's whose BMI < 27 kg/m2.
心脏计算机断层扫描血管造影（CCTA）研究引发了对患者放射生物学效应的关注。因此，估算CCTA期间吸收的辐射剂量很重要。在本研究中，我们使用三种不同的回顾性心电图（ECG）方案比较了辐射剂量和图像质量。共有123例接受CCTA的患者被分为三组。我们在第（1）组中使用全剂量调制（CareDose4D）技术；第（2）组固定管电流为200 mAs；在第（3）组中，根据胸围调整管电流（180 - 200 mAs）和管电压（100 - 120 kVp）。对于第（1）组和第（2）组，管电压根据体重指数（BMI）进行调整，其中BMI < 27 kg/m²时为100 kVp，BMI≥27 kg/m²时为120 kVp。通过测量左右冠状动脉主动脉根部近端节段的信号强度（SI）和图像噪声（IN）来计算图像质量的定量评估。还使用SI和IN计算信噪比（SNR）和对比噪声比（CNR）。两位经验丰富的放射科医生使用4分制评估主观图像质量。我们的结果表明，第（1）组的平均有效剂量为4.46 mSv（范围：1.75 - 8.6 mSv），第（2）组的平均有效辐射剂量为5.07 mSv（范围：2.57 - 9.74 mSv），第（3）组的平均有效剂量为5.85 mSv（范围：3.36 - 12.17 mSv）。与第（2）组和第（3）组相比，第（1）组的辐射剂量分别降低了12%和23%。在多变量分析中，调整BMI后，BMI < 27 kg/m²患者的辐射剂量有显著差异；第（1）组为2.53 mSv，第（2）组为3.54 mSv，第（3）组为5.207 mSv（p < 0.0001）。此外，在固定管电流200 mAs的情况下，将管电压从120 kVp降低到100 kVp，辐射剂量降低了27%。各组之间的定量图像质量（IN、SI、SNR和CNR）无统计学意义。综上所述，回顾性心电图门控可通过使用自动管电流调制和100 kVp管电压来降低辐射剂量，同时保持BMI < 27 kg/m²患者的图像质量。
