Evaluating organ delineation, dose calculation and daily localization in an open-MRI simulation workflow for prostate cancer patients
Evaluating organ delineation, dose calculation and daily localization in an open-MRI simulation workflow for prostate cancer patients
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DOI：
10.1186/s13014-014-0309-0
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发表时间：
2015-02-11
影响因子：
3.6
通讯作者：
Movsas, Benjamin
中科院分区：
文献类型：
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作者：
Doemer, Anthony;Chetty, Indrin J.;Movsas, Benjamin
背景：本研究描述了用于模拟前列腺癌放射治疗的垂直场开放式磁共振成像(MRI)扫描仪的初步测试和评估。我们已经评估了使用开放式MRI作为模拟和规划的唯一方式的临床工作流程。给出了使用锥束CT(CBCT)进行日常定位的MRI对齐(与CT参考数据集)相关的相关结果。方法：10名患者参加了一项IRB批准的研究，该研究利用MRI和CT模拟来评估MRI模拟过程。用MRI评估前列腺体积、精囊和阴茎球部的差异，并与CT进行比较。为了评估剂量计算的准确性，将体积密度分配映射到各自的MRI数据集，并重新计算治疗后的IMRT计划。为了图像定位的目的，400个CBCT被重新评估，以MRI作为参考数据集，并与CBCT到CT的配准进行比较。使用van Herk公式计算基于MRI/CBCT移位的计划边缘。结果：MRI和CT之间存在显著的器官轮廓差异。CT检查的前列腺体积平均比核磁共振检查大39.7%(p=0.002)。精囊体积差异无统计学意义(p=0.454)。阴茎球体积在CT上增加了61.1%，但无统计学意义(p=0.074)。指定体积密度的基于MRI的剂量计算与异质性校正的CT计算的一致性在1%以内。在CBCT-CT和CBCT-MRI之间，队列的移位位置相差-0.15+/-0.25 cm(前后)、0.05+/-0.19 cm(上下)和-0.01+/-0.14 cm(左右)。结论：本研究证实了开放式MRI扫描仪作为前列腺癌治疗计划模拟、剂量计算和日常图像定位的主要成像手段的潜力。
Background: This study describes initial testing and evaluation of a vertical-field open Magnetic Resonance Imaging (MRI) scanner for the purpose of simulation in radiation therapy for prostate cancer. We have evaluated the clinical workflow of using open MRI as a sole modality for simulation and planning. Relevant results related to MRI alignment (vs. CT) reference dataset with Cone-Beam CT (CBCT) for daily localization are presented.Methods: Ten patients participated in an IRB approved study utilizing MRI along with CT simulation with the intent of evaluating the MRI-simulation process. Differences in prostate gland volume, seminal vesicles, and penile bulb were assessed with MRI and compared to CT. To evaluate dose calculation accuracy, bulk-density-assignments were mapped onto respective MRI datasets and treated IMRT plans were re-calculated. For image localization purposes, 400 CBCTs were re-evaluated with MRI as the reference dataset and daily shifts compared against CBCT-to-CT registration. Planning margins based on MRI/CBCT shifts were computed using the van Herk formalism.Results: Significant organ contour differences were noted between MRI and CT. Prostate volumes were on average 39.7% (p = 0.002) larger on CT than MRI. No significant difference was found in seminal vesicle volumes (p = 0.454). Penile bulb volumes were 61.1% higher on CT, without statistical significance (p = 0.074). MRI-based dose calculations with assigned bulk densities produced agreement within 1% with heterogeneity corrected CT calculations. The differences in shift positions for the cohort between CBCT-to-CT registration and CBCT-to-MRI registration are -0.15 +/- 0.25 cm (anterior-posterior), 0.05 +/- 0.19 cm (superior-inferior), and -0.01 +/- 0.14 cm (left-right).Conclusions: This study confirms the potential of using an open-field MRI scanner as primary imaging modality for prostate cancer treatment planning simulation, dose calculations and daily image localization.