Monte Carlo-calculated patient organ doses from kV-cone beam CT in image-guided radiation therapy
Monte Carlo-calculated patient organ doses from kV-cone beam CT in image-guided radiation therapy
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DOI：
10.1088/2057-1976/1/2/025203
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发表时间：
2015-08-01
影响因子：
1.4
通讯作者：
Nakaguchi, Yuji
中科院分区：
文献类型：
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作者：
Hioki, Kazunari;Araki, Fujio;Nakaguchi, Yuji
本研究使用Monte Carlo（MC）模拟评价了图像引导放射治疗中使用的Varian机载成像仪（OBI）和Elekta x射线容积成像仪（XVI）的kV锥形束计算机断层扫描（kVCBCT）的患者特定器官剂量。使用EGSnrc/BEAMnrc用户代码对两种kV-CBCT系统进行射束建模。通过使用头部、“头颈部”、胸部、腹部和骨盆五个解剖区域的计划CT数据集，从建模的kV-CBCT射束计算患者剂量分布。两个kV-CBCT系统均使用两种默认采集模式，即胸部、腹部和骨盆的全扫描模式，以及头部和“头部和颈部”的半扫描模式。MC计算的剂量分布被转换成吸收剂量的法默室测量身体和头部型体模。分别采用全扫描模式和半扫描模式照射体型体模（直径30 cm，长51 cm）和头型体模（直径16 cm，长33 cm）。最后，根据剂量体积直方图定量评估患者特定器官剂量。OBI的胸部、腹部和骨盆软组织的平均器官剂量分别为1.52-4.13 cGy、1.30-2.56 cGy和2.32 - 3.81 cGy，XVI的平均器官剂量分别为0.82-1.60 cGy、0.66-1.04 cGy和0.97-1.41 cGy。在全扫描模式下，XVI的器官剂量为OBI的一半至三分之一。心脏、睾丸等位于前表面的器官受照剂量高于中心区域。同时，OBI的头部和“头颈部”软组织的平均剂量分别为0.09-0.43 cGy和0.09-0.45 cGy，XVI的平均剂量分别为0.13-0.39 cGy和0.09-0.31 cGy。在半扫描模式下，根据扫描方向，在OBI的后表面和XVI的前表面观察到较高的剂量。
This study evaluated patient specific organ doses from kV-cone beam computed tomography (kVCBCT) for the Varian on-board imager (OBI) and the Elekta x-ray volumetric imager (XVI) used in image-guided radiation therapy using Monte Carlo (MC) simulations. The beam modeling for both kV-CBCT systems was performed with the EGSnrc/BEAMnrc user-code. The patient dose distributions were calculated from the modeled kV-CBCT beams by using planning CT data sets for five anatomical regions of head, 'head and neck', chest, abdomen, and pelvis. Two default acquisition modes, full scan mode for chest, abdomen, and pelvis, and half scan mode for head and 'head and neck', were used for both kV-CBCT systems. The MC-calculated dose distributions were converted into absorbed doses by Farmer chamber measurements in body-and head-type phantoms. A bodytype phantom (30 cm diameter and 51 cm length) and a head-type phantom (16 cm diameter and 33 cm length) were irradiated with the full scan mode and the half scan mode, respectively. Finally, the patient specific organ doses were quantitatively evaluated from dose-volume histograms. The mean organ doses for soft tissue in chest, abdomen, and pelvis were 1.52-4.13 cGy, 1.30-2.56 cGy, and 2.323.81 cGy for OBI, and 0.82-1.60 cGy, 0.66-1.04 cGy, and 0.97-1.41 cGy for XVI, respectively. In the full scan mode, organ doses for XVI were one-half to one-third of those for OBI. The organs located at the anterior surfaces like heart and testes were higher doses than central regions. Meanwhile, the mean doses for soft tissue in the head and 'head and neck' were 0.09-0.43 cGy and 0.09-0.45 cGy for OBI, and 0.13-0.39 cGy and 0.09-0.31 cGy for XVI, respectively. In the half scan mode, the higher doses were observed at the posterior surface for OBI and at the anterior surface for XVI, depending on the scan direction.