Nuclear Engineering and Engineering Physics Program, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Phys Med Biol. 2010 Mar 7;55(5):1441-51. doi: 10.1088/0031-9155/55/5/012. Epub 2010 Feb 11.
The rapidly increasing number of diagnostic computed tomography (CT) procedures in the recent decades has spurred heightened concern over the potential risk to patients. Although an accurate organ dose assessment tool has now become highly desirable, existing software packages depend on stylized computational phantoms that were originally developed more than 40 years ago, exhibiting very large discrepancies when compared with phantoms that are anatomically realistic. However, past comparative studies did not focus on CT protocols for adult patients. This study was designed to quantitatively compare two types of phantoms, the stylized phantoms and a pair of recently developed RPI-adult male and adult female (RPI-AM and RPI-AF) phantoms, for various CT scanning protocols involving the chest, abdomen-pelvis and chest-abdomen-pelvis. Organ doses were based on Monte Carlo simulations using the MCNPX code and a detailed CT scanner model for the GE LightSpeed 16. Results are presented as ratios of organ doses from the stylized phantoms to those from the RPI phantoms. It is found that, for most organs contained in the scan volume, the ratios were within the range of 0.75-1.16. However, the stomach doses are significantly different and the ratio is found to be up to 1.86 in male phantoms and 2.29 in the female phantoms due to the anatomical differences between the two types of phantoms. Organs that lie near a scan boundary also exhibit a significant relative difference in organ doses between the two types of phantoms. This study concludes that, due to relatively low x-ray energies, CT doses are very sensitive to organ shape, size and position, and thus anatomically realistic phantoms should be used to avoid the dose uncertainties caused by the lack of anatomical realism. The new phantoms, such as the RPI-AM and AF phantoms that are designed using advanced surface meshes, are deformable and will make it possible to match the anatomy of a specific patient leading to further improvement in dose and risk assessments for patients undergoing CT examinations.
近几十年来，诊断用计算机断层扫描（CT）数量迅速增加，这引发了人们对患者潜在风险的高度关注。尽管现在非常需要一种精确的器官剂量评估工具，但现有的软件包依赖于最初在 40 多年前开发的规范化计算体模，与解剖学真实的体模相比，这些体模存在很大差异。然而，过去的比较研究并未关注成人患者的 CT 方案。本研究旨在定量比较两种类型的体模，即规范化体模和最近开发的 RPI 成人男性和女性（RPI-AM 和 RPI-AF）体模，用于涉及胸部、腹部-骨盆和胸部-腹部-骨盆的各种 CT 扫描方案。器官剂量基于使用 MCNPX 代码和详细 CT 扫描仪模型的蒙特卡罗模拟，该模型适用于 GE LightSpeed 16。结果以从规范化体模到 RPI 体模的器官剂量比表示。结果发现，对于扫描体积中包含的大多数器官，该比值在 0.75-1.16 范围内。然而，由于两种体模之间的解剖差异，胃剂量差异显著，男性体模中的比值高达 1.86，女性体模中的比值高达 2.29。靠近扫描边界的器官也表现出两种体模之间器官剂量的显著相对差异。本研究得出结论，由于相对较低的 X 射线能量，CT 剂量对器官形状、大小和位置非常敏感，因此应使用解剖学真实的体模来避免由于缺乏解剖学真实而导致的剂量不确定性。新的体模，如使用先进表面网格设计的 RPI-AM 和 AF 体模，是可变形的，这将有可能匹配特定患者的解剖结构，从而进一步改善接受 CT 检查的患者的剂量和风险评估。
