Huda W, Gkanatsios N A
Department of Radiology, University of Florida, Gainesville 32610-0374, USA.
Med Phys. 1997 Aug;24(8):1311-6. doi: 10.1118/1.598153.
The patient effective dose, E, is an indicator of the stochastic radiation risk associated with radiographic or fluoroscopic x-ray examinations. Determining effective doses for radiologic examinations by measurement or calculation is generally very difficult. By contrast, the energy imparted, epsilon, to the patient may be obtained from the x-ray exposure-area product incident on the patient. As energy imparted is approximately proportional to the effective dose for any given x-ray radiographic view, the availability of E/epsilon ratios for common radiographic projections provides a convenient way for estimating effective doses. Ratios of E/epsilon were obtained for 68 projections using E and epsilon values obtained from published dosimetry data computed using Monte Carlo techniques on an adult anthropomorphic phantom. The average E/epsilon ratio for the 68 projections in adults was 17.8+/-1.4 mSv/J, whereas uniform whole body irradiation corresponds to 14.1 mSv/J. The major determinant of E/epsilon ratios was the projection employed (the body region irradiated and x-ray beam orientation), whereas the tube potential and beam filtration were of secondary importance. Adult E/epsilon ratios may also be used to obtain effective doses to pediatric patients undergoing x-ray examinations by application of a correction factor based on the patient mass.
患者有效剂量E是与X射线摄影或透视检查相关的随机辐射风险指标。通过测量或计算来确定放射检查的有效剂量通常非常困难。相比之下，传递给患者的能量ε可从入射到患者身上的X射线照射面积乘积中获得。由于对于任何给定的X射线摄影视图，传递的能量与有效剂量大致成正比，因此常见摄影投影的E/ε比值为估算有效剂量提供了一种便捷方法。利用从已发表的剂量学数据中获得的E和ε值，这些数据是使用蒙特卡罗技术在成人人体模型上计算得出的，从而得到了68种投影的E/ε比值。成人68种投影的平均E/ε比值为17.8±1.4 mSv/J，而全身均匀照射对应的比值为14.1 mSv/J。E/ε比值的主要决定因素是所采用的投影（照射的身体部位和X射线束方向），而管电压和束流过滤的重要性次之。通过应用基于患者体重的校正因子，成人的E/ε比值也可用于获得接受X射线检查的儿科患者的有效剂量。
