Taschereau Richard, Chow Patrick L, Chatziioannou Arion F
The Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, University of California School of Medicine, 700 Westwood Boulevard, Los Angeles, California 90095, USA.
Med Phys. 2006 Jan;33(1):216-24. doi: 10.1118/1.2148333.
The purpose of this work was to calculate radiation dose and its organ distribution in a realistic mouse phantom from micro-computed tomography (microCT) imaging protocols. CT dose was calculated using GATE and a voxelized, realistic phantom. The x-ray photon energy spectra used in simulations were precalculated with GATE and validated against previously published data. The number of photons required per simulated experiments was determined by direct exposure measurements. Simulated experiments were performed for three types of beams and two types of mouse beds. Dose-volume histograms and dose percentiles were calculated for each organ. For a typical microCT screening examination with a reconstruction voxel size of 200 microm, the average whole body dose varied from 80 mGy (at 80 kVp) to 160 mGy (at 50 kVp), showing a strong dependence on beam hardness. The average dose to the bone marrow is close to the soft tissue average. However, due to dose nonuniformity and higher radiation sensitivity, 5% of the marrow would receive an effective dose about four times higher than the average. If CT is performed longitudinally, a significant radiation dose can be given. The total absorbed radiation dose is a function of milliamperes-second, beam hardness, and desired image quality (resolution, noise and contrast). To reduce dose, it would be advisable to use the hardest beam possible while maintaining an acceptable contrast in the image.
这项工作的目的是根据微型计算机断层扫描(microCT)成像协议,计算逼真的小鼠模型中的辐射剂量及其器官分布。使用GATE和体素化的逼真模型计算CT剂量。模拟中使用的X射线光子能谱由GATE预先计算,并与先前发表的数据进行了验证。通过直接曝光测量确定每个模拟实验所需的光子数量。针对三种类型的光束和两种类型的小鼠床进行了模拟实验。计算每个器官的剂量体积直方图和剂量百分位数。对于重建体素大小为200微米的典型microCT筛查检查,全身平均剂量从80毫戈瑞(在80千伏峰值)到160毫戈瑞(在50千伏峰值)不等,显示出对光束硬度的强烈依赖性。骨髓的平均剂量接近软组织平均剂量。然而,由于剂量不均匀性和较高的辐射敏感性,5%的骨髓所接受的有效剂量比平均值高约四倍。如果纵向进行CT检查,会给予显著的辐射剂量。总吸收辐射剂量是毫安秒、光束硬度和所需图像质量(分辨率、噪声和对比度)的函数。为了降低剂量,建议在保持图像可接受对比度的同时,尽可能使用最硬的光束。