Patient dose simulations for scanning-beam digital x-ray tomosynthesis of the lungs.
Patient dose simulations for scanning-beam digital x-ray tomosynthesis of the lungs.
复制标题
肺部扫描束数字 X 射线断层合成的患者剂量模拟。
DOI：
10.1118/1.4826159
复制
发表时间：
2013
期刊：
影响因子：
3.8
通讯作者：
Fahrig,Rebecca
中科院分区：
文献类型：
--
作者：
Nelson,Geoff;Yoon,Sungwon;Krishna,Ganesh;Wilfley,Brian;Fahrig,Rebecca
目的：一种改进的图像引导肺肿瘤活检方法可以帮助降低高假阴性率。这项工作的目的是优化扫描束数字断层扫描系统（SBDX）的几何结构，为目标验证提供真实的实时3D断层重建。系统独特的几何结构要求在患者剂量、成像视野（FOV）和断层摄影角度之间进行权衡。方法：计算断层摄影角度作为肿瘤到探测器距离的函数。使用Monte Carlo软件（PCXMC）计算源-探测器距离（SDD）为90 - 150 cm、肿瘤位于距源20 cm至距探测器20 cm处的患者位置以及以左肺和右肺以及肺的内侧和远端外周为中心的FOV的器官剂量和有效剂量。这些计算是针对两个系统完成的，SBDX系统和GE OEC-9800 C形臂透视装置。为了评价系统几何结构的剂量效应，使用SBDX和荧光透视的300 mAs扫描计算PCXMC的结果。使用Rose标准来确定肿瘤SNR为5所需的通量，考虑了PCXMC生成的所有模型的散射、气隙、系统几何形状和患者位置。使用恒定的肿瘤SNR计算的通量，从PCXMC的结果被用来比较SBDX和fluorescence.Results之间的给定SNR的患者剂量：断层摄影角度的变化与SDD仅在探测器附近的区域。由于它们的几何形状，源阵列和检测器在源到肿瘤的距离处对于任何给定的SDD具有峰值断层摄影角度，该距离是SDD的69.7%，假设源和检测器尺寸恒定。由于几何考虑，改变患者位置以增加断层摄影角度对器官剂量分布具有显著影响。对于SBDX和荧光透视几何结构，器官的剂量通常随着患者位置的变化而以相反的方式变化。当肿瘤SNR保持恒定时（即，X射线通量适当缩放），在患者位置的典型范围内，对于相同条件，SBDX的剂量比荧光透视低2-10倍。患者的相对位置（作为SDD的百分比）对剂量的影响比SDD或患者位置更显著。对于给定的肿瘤SNR和SDD，提供最小剂量的患者位置与最大断层摄影角度的位置大致相同。结论：SBDX提供了比目前使用的C形臂透视显着的剂量优势。最低剂量的患者位置与最大断层摄影角度的位置一致。为了给患者和肺科医生的设备提供足够的空间，建议SDD为100 cm。
Purpose:An improved method of image guidance for lung tumor biopsies could help reduce the high rate of false negatives. The aim of this work is to optimize the geometry of the scanning‐beam digital tomography system (SBDX) for providing real‐time 3D tomographic reconstructions for target verification. The unique geometry of the system requires trade‐offs between patient dose, imaging field of view (FOV), and tomographic angle.Methods:Tomosynthetic angle as a function of tumor‐to‐detector distance was calculated. Monte Carlo Software (PCXMC) was used to calculate organ doses and effective dose for source‐to‐detector distances (SDDs) from 90 to 150 cm, patient locations with the tumor at 20 cm from the source to 20 cm from the detector, and FOVs centered on left lung and right lung as well as medial and distal peripheries of the lungs. These calculations were done for two systems, a SBDX system and a GE OEC‐9800 C‐arm fluoroscopic unit. To evaluate the dose effect of the system geometry, results from PCXMC were calculated using a scan of 300 mAs for both SBDX and fluoroscopy. The Rose Criterion was used to find the fluence required for a tumor SNR of 5, factoring in scatter, air‐gap, system geometry, and patient position for all models generated with PCXMC. Using the calculated fluence for constant tumor SNR, the results from PCXMC were used to compare the patient dose for a given SNR between SBDX and fluoroscopy.Results:Tomographic angle changes with SDD only in the region near the detector. Due to their geometry, the source array and detector have a peak tomographic angle for any given SDD at a source to tumor distance that is 69.7% of the SDD assuming constant source and detector size. Changing the patient location in order to increase tomographic angle has a significant effect on organ dose distribution due to geometrical considerations. With SBDX and fluoroscopy geometries, the dose to organs typically changes in an opposing manner with changing patient location. When tumor SNR is held constant (i.e., x‐ray fluence is scaled appropriately), SBDX gives 2–10 times less dose than fluoroscopy for the same conditions within the typical range of patient locations. The relative position of the patient (as a percent of SDD) has a much more significant impact on dose than either SDD or patient position. The patient position providing the minimum dose for a given tumor SNR and SDD is approximately the same as the position of maximum tomographic angle.Conclusions:SBDX offers a significant dose advantage over currently used C‐arm fluoroscopy. The patient location with lowest dose coincides with the location of maximum tomographic angle. In order to provide adequate space for the patient and for the pulmonologists’ equipment, a SDD of 100 cm is recommended.