Monte Carlo calculation of imaging doses from diagnostic multidetector CT and kilovoltage cone-beam CT as part of prostate cancer treatment plans
Monte Carlo calculation of imaging doses from diagnostic multidetector CT and kilovoltage cone-beam CT as part of prostate cancer treatment plans
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DOI：
10.1118/1.3512791
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发表时间：
2010-12-01
期刊：
影响因子：
3.8
通讯作者：
Xu, X. George
中科院分区：
文献类型：
--
作者：
Ding, Aiping;Gu, Jianwei;Xu, X. George
Purpose: To calculate imaging doses to the rectum, bladder, and femoral heads as part of a prostate cancer treatment plans, assuming an image guided radiation therapy (IGRT) procedure involving either the multidetector CT (MDCT) or kilovoltage cone-beam CT (kV CBCT).Methods: This study considered an IGRT treatment plan for a prostate carcinoma patient involving 50.4 Gy from 28 initial fractions and a boost of 28.8 Gy from 16 fractions. A total of 45 CT imaging procedures, each involving a MDCT or a kV CBCT scan procedure, were carefully modeled using the MCNPX code version 2.5.0. The MDCT scanner model is based on the GE LightSpeed 16-MDCT scanner and the kV CBCT scanner model is based on the Varian On-Board Imager using parameters reported by the CT manufacturers and literatures. A patient-specific treatment planning CT data set was used to construct the phantom for the dose calculation. The target, organs-at-risk (OARs), and background voxels in the CT data set were categorized into six tissue types according to CT numbers for Monte Carlo calculations.Results: For a total of 45 imaging procedures, it was found that the rectum received 78.4 and 76.7 cGy from MDCT and kV CBCT, respectively. The bladder received slightly greater doses of 82.4 and 77.9 cGy, while the femoral heads received much higher doses of 182.3 and 141.3 cGy from MDCT and kV CBCT, respectively. To investigate the impact of these imaging doses on treatment planning, OAR doses from MDCT or kV CBCT imaging procedures were added to the corresponding dose matrix reported by the original treatment plans to construct dose volume histograms. It was found that after the imaging dose is added, the rectum volumes irradiated to 75 and 70 Gy increased from 13.9% and 21.2%, respectively, in the original plan to 14.8% and 21.8%. The bladder volumes receiving 80 Gy increased to 4.6% from 4.1% in the original plan and the volume receiving 75 Gy increased to 7.9% from 7.5%. All values remained within the tolerance levels: V-70
