Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning.
Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning.
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DOI：
10.1016/j.ejmp.2017.02.017
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
Knopf AC
中科院分区：
文献类型：
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作者：
Guerreiro F;Burgos N;Dunlop A;Wong K;Petkar I;Nutting C;Harrington K;Bhide S;Newbold K;Dearnaley D;deSouza NM;Morgan VA;McClelland J;Nill S;Cardoso MJ;Ourselin S;Oelfke U;Knopf AC
建立仅限MRI的RTP工作流程需要合成CT进行剂量计算。本研究评估了使用多图谱CT合成方法的可行性。所提出的方法在头颈部和前列腺癌患者身上进行了验证。结果表明，为将来的患者定位提供了准确的骨估计。结果表明，合成CT适用于进行临床剂量计算。计算机断层扫描（CT）成像是目前放射治疗计划（RTP）的金标准。仅建立磁共振成像（MRI）RTP工作流程需要生成合成CT（sCT）用于剂量计算。本研究评价了头颈部和前列腺患者使用多图谱sCT合成方法（sCTa）的可行性。多图谱方法基于非刚性对齐的MR和CT图像对。通过将MRI图谱与患者的MRI配准并根据与患者的形态相似性融合映射的图谱来获得sCTa。为了进行比较，还评价了堆密度分配方法（sCTbda）。通过将密度值分配给MRI组织类别（空气、骨和软组织）获得sCTbda。在评价sCT的合成准确度（平均绝对误差）后，将基于sCT的描绘与基于CT的描绘进行几何比较。根据sCT和剂量-体积直方图重新计算临床计划，并使用CT剂量作为基础事实进行伽马分析。结果表明，两种sCT均适用于进行临床剂量计算，计划靶体积和风险器官的平均剂量差异均小于1%。然而，只有sCTa提供了准确和自动的骨骼描绘。将MR描绘与我们的多图谱CT合成方法相结合，可以实现仅MRI治疗计划，从而提高治疗的剂量和几何准确性，并减少成像程序的数量。
Establishing MRI-only RTP workflows requires synthetic CTs for dose calculation. This study evaluates the feasibility of using a multi-atlas CT synthesis approach. The proposed method was validated on head and neck and prostate cancer patients. Results showed an accurate bone estimation for future patient positioning. Results showed that synthetic CTs are suitable to perform clinical dose calculations. Computed tomography (CT) imaging is the current gold standard for radiotherapy treatment planning (RTP). The establishment of a magnetic resonance imaging (MRI) only RTP workflow requires the generation of a synthetic CT (sCT) for dose calculation. This study evaluates the feasibility of using a multi-atlas sCT synthesis approach (sCTa) for head and neck and prostate patients. The multi-atlas method was based on pairs of non-rigidly aligned MR and CT images. The sCTa was obtained by registering the MRI atlases to the patient’s MRI and by fusing the mapped atlases according to morphological similarity to the patient. For comparison, a bulk density assignment approach (sCTbda) was also evaluated. The sCTbda was obtained by assigning density values to MRI tissue classes (air, bone and soft-tissue). After evaluating the synthesis accuracy of the sCTs (mean absolute error), sCT-based delineations were geometrically compared to the CT-based delineations. Clinical plans were re-calculated on both sCTs and a dose-volume histogram and a gamma analysis was performed using the CT dose as ground truth. Results showed that both sCTs were suitable to perform clinical dose calculations with mean dose differences less than 1% for both the planning target volume and the organs at risk. However, only the sCTa provided an accurate and automatic delineation of bone. Combining MR delineations with our multi-atlas CT synthesis method could enable MRI-only treatment planning and thus improve the dosimetric and geometric accuracy of the treatment, and reduce the number of imaging procedures.