Department of Radiology and Radiological Science, Medical University of South Carolina, 96 Jonathan Lucas Street, MSC 323, Charleston, South Carolina 29425-3230, USA.
Med Phys. 2010 Feb;37(2):842-7. doi: 10.1118/1.3298015.
The goal of this study was to estimate organ doses for chest CT examinations using volume computed tomography dose index (CTDIvol) data as well as accounting for patient weight.
A CT dosimetry spreadsheet (ImPACT CT patient dosimetry calculator) was used to compute organ doses for a 70 kg patient undergoing chest CT examinations, as well as volume computed tomography dose index (CTDIvol) in a body CT dosimetry phantom at the same CT technique factors. Ratios of organ dose to CTDIvoI (f(organ)) were generated as a function of anatomical location in the chest for the breasts, lungs, stomach, red bone marrow, liver, thyroid, liver, and thymus. Values of f(organ) were obtained for x-ray tube voltages ranging from 80 to 140 kV for 1, 4, 16, and 64 slice CT scanners from two vendors. For constant CT techniques, we computed ratios of dose in water phantoms of differing diameter. By modeling patients of different weights as equivalent water cylinders of different diameters, we generated factors that permit the estimation of the organ doses in patients weighing between 50 and 100 kg who undergo chest CT examinations relative to the corresponding organ doses received by a 70 kg adult.
For a 32 cm long CT scan encompassing the complete lungs, values of f(organ) ranged from 1.7 (thymus) to 0.3 (stomach). Organs that are directly in the x-ray beam, and are completely irradiated, generally had f(organ), values well above 1 (i.e., breast, lung, heart, and thymus). Organs that are not completely irradiated in a total chest CT scan generally had f(organ) values that are less than 1 (e.g., red bone marrow, liver, and stomach). Increasing the x-ray tube voltage from 80 to 140 kV resulted in modest increases in f(organ) for the heart (9%) and thymus (8%), but resulted in larger increases for the breast (19%) and red bone marrow (21%). Adult patient chests have been modeled by water cylinders with diameters between approximately 20 cm for a 50 kg patient and approximately 28 cm for a 100 kg patient. At constant x-ray techniques, a 50 kg patient is expected to have doses that are approximately 18% higher than those in a 70 kg adult, whereas a 100 kg patient will have doses that are apparoximately 18% lower.
We describe a practical method to use CTDI data provided by commercial CT scanners to obtain patient and examination specific estimates of organ dose for chest CT examinations.
本研究旨在使用容积 CT 剂量指数（CTDIvol）数据估算胸部 CT 检查的器官剂量，并考虑患者体重。
使用 CT 剂量学电子表格（ImPACT CT 患者剂量计算器）计算 70 公斤患者进行胸部 CT 检查的器官剂量，以及在相同 CT 技术因素下在体 CT 剂量学体模中的容积 CT 剂量指数（CTDIvol）。生成了器官剂量与 CTDIvol（f（器官））的比值，作为胸部解剖位置的函数，用于乳房、肺、胃、红骨髓、肝、甲状腺、肝和胸腺。对于来自两个供应商的 1、4、16 和 64 层 CT 扫描仪，从 80 到 140 kV 的 X 射线管电压获得了 f（器官）的值。对于恒定的 CT 技术，我们计算了不同直径水模体中的剂量比值。通过将不同重量的患者建模为不同直径的等效水圆柱体，我们生成了因子，可用于估算体重在 50 至 100 公斤之间接受胸部 CT 检查的患者的器官剂量，与 70 公斤成人接受的相应器官剂量相对应。
对于涵盖整个肺部的 32 厘米长 CT 扫描，f（器官）值范围从 1.7（胸腺）到 0.3（胃）。直接位于 X 射线束中的器官，并且完全被照射，通常具有远高于 1 的 f（器官）值（即乳房、肺、心脏和胸腺）。在全胸部 CT 扫描中未完全照射的器官，f（器官）值通常小于 1（例如红骨髓、肝脏和胃）。将 X 射线管电压从 80 增加到 140 kV，导致心脏（9%）和胸腺（8%）的 f（器官）适度增加，但导致乳房（19%）和红骨髓（21%）的增加更大。使用直径在 20 厘米左右的水圆柱体对 50 公斤患者和直径在 28 厘米左右的水圆柱体对 100 公斤患者对成人患者胸部进行了建模。在恒定的 X 射线技术下，预计 50 公斤患者的剂量比 70 公斤成人高约 18%，而 100 公斤患者的剂量低约 18%。
我们描述了一种实用的方法，可使用商业 CT 扫描仪提供的 CTDI 数据来获得胸部 CT 检查的患者和检查特定的器官剂量估计值。
