Theocharopoulos Nicholas, Perisinakis Kostas, Damilakis John, Karampekios Spyros, Gourtsoyiannis Nicholas
Department of Medical Physics, Faculty of Medicine, University of Crete, P.O. Box 2208, Iraklion, 71003, Crete, Greece.
Eur Radiol. 2006 Nov;16(11):2575-85. doi: 10.1007/s00330-006-0251-0. Epub 2006 Apr 22.
Standard CT dose measurements were performed on a Siemens Sensation 16 scanner. CT dose indices, free-in-air (CTDI(F)) and weighted (CTDI(W)), were measured in all available axial and helical beam collimations of the head and body scanning modes. The effect of tube current, high voltage, rotation time, beam collimation and pitch on the CT doses was investigated. CT doses increased as a power function of high voltage. The kVp exponent n varied with beam collimation from 2.7 to 3.1 for CTDI(W), and from 2.4 to 2.6 for CTDI(F). Automatic change of the focal spot size increased radiation doses up to a factor of 1.18. Measured small-focus CTDI(W) values differed from those displayed at the console from -24 to 14%. Peripheral doses in the head phantom were higher compared to the body phantom by a factor of 1.5 to 2. Central doses are 2.7 to 4.1 times higher. Differences in beam collimation resulted in 50% variation in the CTDI(W) in the body phantom and 60% in the head phantom. In conclusion, our study has confirmed the great impact of technique factors and acquisition parameters on CT doses. The provided comprehensive dosimetric data will facilitate the dose-effective use of the scanner studied.
在西门子Sensation 16扫描仪上进行了标准CT剂量测量。在头部和身体扫描模式的所有可用轴向和螺旋束准直中测量了CT剂量指数，即空气比释动能（CTDI(F)）和加权剂量（CTDI(W)）。研究了管电流、高压、旋转时间、束准直和螺距对CT剂量的影响。CT剂量随高压呈幂函数增加。对于CTDI(W)，kVp指数n随束准直从2.7变化到3.1，对于CTDI(F)，从2.4变化到2.6。焦点尺寸的自动变化使辐射剂量增加高达1.18倍。测量的小焦点CTDI(W)值与控制台显示的值相差-24%至14%。头部模型中的周边剂量比身体模型高1.5至2倍。中心剂量高2.7至4.1倍。束准直的差异导致身体模型中CTDI(W)变化50%，头部模型中变化60%。总之，我们的研究证实了技术因素和采集参数对CT剂量有很大影响。所提供的综合剂量学数据将有助于对所研究的扫描仪进行剂量有效的使用。
