Theocharopoulos Nicholas, Damilakis John, Perisinakis Kostas, Tzedakis Antonis, Karantanas Apostolos, Gourtsoyiannis Nicholas
Department of Medical Physics and Radiology Faculty of Medicine, University of Crete, PO. Box 2208, Iraklion 71003, Crete, Greece.
Med Phys. 2006 Oct;33(10):3846-56. doi: 10.1118/1.2349694.
The purpose of this study is to provide a method and required data for the estimation of effective dose (E) values to adult and pediatric patients from computed tomography (CT) scans of the head, chest abdomen, and pelvis, performed on multi-slice scanners. Mean section radiation dose (dm) to cylindrical water phantoms of varying radius normalized over CT dose index free-in-air (CTDIF) were calculated for the head and body scanning modes of a multislice scanner with use of Monte Carlo techniques. Patients were modeled as equivalent water phantoms and the energy imparted (epsilon) to simulated pediatric and adult patients was calculated on the basis of measured CTDI(F) values. Body region specific energy imparted to effective dose conversion coefficients (E/epsilon) for adult male and female patients were generated from previous data. Effective doses to patients aged newborn to adult were derived for all available helical and axial beam collimations, taking into account age specific patient mass and scanning length. Depending on high voltage, body region, and patient sex, E/epsilon values ranged from 0.008 mSv/mJ for head scans to 0.024 mSv/mJ for chest scans. When scanned with the same technique factors as the adults, pediatric patients absorb as little as 5% of the energy imparted to adults, but corresponding effective dose values are up to a factor of 1.6 higher. On average, pediatric patients absorb 44% less energy per examination but have a 24% higher effective dose, compared with adults. In clinical practice, effective dose values to pediatric patients are 2.5 to 10 times lower than in adults due to the adaptation of tube current. A method is provided for the calculation of effective dose to adult and pediatric patients on the basis of individual patient characteristics such as sex, mass, dimensions, and density of imaged anatomy, and the technical features of modern multislice scanners. It allows the optimum selection of scanning parameters regarding patient doses at CT.
本研究的目的是提供一种方法和所需数据，用于估算多层扫描仪对头、胸、腹和骨盆进行计算机断层扫描（CT）时，成年和儿科患者的有效剂量（E）值。利用蒙特卡罗技术，针对多层扫描仪的头部和身体扫描模式，计算了不同半径的圆柱形水模体相对于空气比释动能（CTDIF）归一化后的平均层辐射剂量（dm）。将患者建模为等效水模体，并根据测量的CTDI(F)值计算给予模拟儿科和成年患者的能量（ε）。根据先前数据生成成年男性和女性患者身体区域特定的能量给予有效剂量转换系数（E/ε）。考虑到特定年龄患者的体重和扫描长度，针对所有可用的螺旋和轴向束准直，得出了从新生儿到成年人的患者有效剂量。根据高压、身体区域和患者性别，E/ε值范围从头部扫描的0.008 mSv/mJ到胸部扫描的0.024 mSv/mJ。当采用与成年人相同的技术参数进行扫描时，儿科患者吸收的能量仅为成年人的5%，但相应的有效剂量值却高出1.6倍。平均而言，与成年人相比，儿科患者每次检查吸收的能量少44%，但有效剂量高24%。在临床实践中，由于管电流的调整，儿科患者的有效剂量值比成年人低2.5至10倍。提供了一种基于个体患者特征（如性别、体重、尺寸以及成像解剖结构的密度）和现代多层扫描仪的技术特征来计算成年和儿科患者有效剂量的方法。它允许在CT检查时根据患者剂量优化选择扫描参数。
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