Goo Hyun Woo, Suh Dong Soo
Department of Radiology and Research Institute of Radiology, Asan Medical Centre, University of Ulsan College of Medicine, 388-1 Poongnap-2dong, Songpa-gu, Seoul 138-736, South Korea.
Pediatr Radiol. 2006 Apr;36(4):344-51. doi: 10.1007/s00247-005-0105-y. Epub 2006 Feb 25.
Dose reduction by combined tube current modulation has not been evaluated in pediatric low-dose CT.
This study was performed to evaluate tube current reduction in non-ECG-gated heart CT angiography in children by combined tube current modulation, and to assess the effects of body weight, age, sex, and scan direction on tube current reduction.
From September 2004 to January 2005, non-ECG-gated heart CT examinations were performed with combined tube current modulation in 50 children (median age 1 year, range 1 month to 16 years; M/F 29/21) with congenital heart disease. Sixteen-slice spiral CT studies were obtained using a weight-based low-dose protocol (80 kVp, 50-160 effective mA). CT scans were obtained in the craniocaudal direction when leg veins (n=36) were used for IV injection of contrast agent and in the caudocranial direction when arm veins (n=13) were used. In one child who underwent a Fontan operation, both arm and leg veins were used. We calculated tube current reduction by combined tube current modulation and evaluated the effects of body weight, age, sex, and scan technique on tube current reduction. The quality of CT angiography images was visually evaluated by an experienced pediatric radiologist.
Overall tube current reduction by combined tube current modulation was 15.8+/-11.1%. The reduction was variable among five body weight groups (9.3+/-7.9% for <4.9 kg, 14.3+/-9.3% for 5.0-9.9 kg, 16.4+/-12.5% for 10.0-19.9 kg, 25.8+/-9.8% for 20.0-39.9 kg, 15.9+/-12.7% for 40.0-59.9 kg) and was significantly different among the five groups (P=0.017). When eight children in the 40.0-59.9-kg group were excluded, age showed a significant positive correlation with tube current reduction (gamma=0.4, P=0.003). There was no significant difference in tube current reduction between boys and girls. Tube current reduction was significantly greater for the caudocranial scan (21.2+/-9.2%) than for the craniocaudal scan (14.2+/-11.3%) (P=0.049). All CT angiography images were of diagnostic quality.
Combined tube current modulation reduced tube current in pediatric non-ECG-gated heart CT by 15.8% without degradation of image quality. With our CT protocol, for body weights up to 39.9 kg, age showed a significant positive correlation with tube current reduction, but there was a lower dose-saving effect in children heavier than 40 kg. Tube current reduction was not affected by sex, but was affected by scan direction.
联合管电流调制的剂量降低在儿科低剂量CT中尚未得到评估。
本研究旨在评估联合管电流调制在儿童非心电图门控心脏CT血管造影中降低管电流的情况，并评估体重、年龄、性别和扫描方向对管电流降低的影响。
2004年9月至2005年1月，对50例先天性心脏病儿童（年龄中位数1岁，范围1个月至16岁；男/女29/21）进行了联合管电流调制的非心电图门控心脏CT检查。使用基于体重的低剂量方案（80 kVp，50 - 160有效毫安）进行16层螺旋CT扫描。当使用腿部静脉（n = 36）进行静脉注射造影剂时，扫描方向为头足方向；当使用手臂静脉（n = 13）时，扫描方向为足头方向。在1例接受Fontan手术的儿童中，同时使用了手臂和腿部静脉。我们计算了联合管电流调制降低的管电流，并评估了体重、年龄、性别和扫描技术对管电流降低的影响。由经验丰富的儿科放射科医生对CT血管造影图像质量进行视觉评估。
联合管电流调制使管电流总体降低了15.8±11.1%。在五个体重组中降低幅度有所不同（体重<4.9 kg组为9.3±7.9%，5.0 - 9.9 kg组为14.3±9.3%，10.0 - 19.9 kg组为16.4±12.5%，20.0 - 39.9 kg组为25.8±9.8%，40.0 - 59.9 kg组为15.9±12.7%），五组之间差异有统计学意义（P = 0.017）。当排除40.0 - 59.9 kg组的8名儿童后，年龄与管电流降低呈显著正相关（γ = 0.4，P = 0.003）。男孩和女孩之间管电流降低无显著差异。足头方向扫描的管电流降低（21.2±9.2%）显著大于头足方向扫描（14.2±11.3%）（P = 0.049）。所有CT血管造影图像均具有诊断质量。
联合管电流调制使儿科非心电图门控心脏CT的管电流降低了15.8%，且图像质量未下降。根据我们的CT方案，对于体重达39.9 kg的儿童，年龄与管电流降低呈显著正相关，但对于体重超过40 kg儿童的剂量节省效果较低。管电流降低不受性别的影响，但受扫描方向的影响。
