Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
J Appl Clin Med Phys. 2022 Mar;23(3):e13517. doi: 10.1002/acm2.13517. Epub 2022 Feb 2.
We investigated the dose deviation related to geometric distortion and dose gradient on magnetic resonance-only treatment planning for intensity-modulated radiation therapy and proton therapy. The residual geometric distortion of two different magnetic resonance imaging (MRI) sequences (A) and (B) was applied in the computed tomography image and the structure set of each patient through a polynomial MRI geometric distortion model to simulate MRI-based treatment planning. A 3D histogram was generated to specify the relationship of dose deviation to geometric distortion and dose gradient. When the dose gradient (G ) approached zero, the maximum dose deviation reached 1.64% and 2.71% for photon plans of sequences A and B, respectively. For proton plans, the maximum dose deviation reached 3.15% and 4.89% for sequences A and B, respectively. When the geometric distortion (d) was close to zero, the maximum dose deviation was less than 0.8% for photon and proton plans of both sequences. Under extreme conditions (d = 2 mm and G = 4.5%/mm), the median value of dose deviation reached 3% and 3.49% for photon and proton plans, respectively for sequence A, and 2.93% and 4.55% for photon and proton plans, respectively, for sequence B. We demonstrate that the dose deviation is specific to MRI hardware parameters. Compared to the photon plan, the proton plan is more sensitive to the changes in geometric distortion. For typical clinical MRI geometric distortion (d ≤2 mm), the median dose deviation is expected to be within 3% and 5% for photon and proton plans, respectively.
我们研究了与磁共振仅适形调强放疗和质子治疗计划相关的几何变形和剂量梯度的剂量偏差。通过多项式磁共振几何变形模型，将两种不同磁共振成像（MRI）序列（A）和（B）的残余几何变形应用于计算机断层扫描图像和每个患者的结构集，以模拟基于 MRI 的治疗计划。生成了一个 3D 直方图来指定剂量偏差与几何变形和剂量梯度的关系。当剂量梯度（G）接近零时，序列 A 和 B 的光子计划的最大剂量偏差分别达到 1.64%和 2.71%。对于质子计划，序列 A 和 B 的最大剂量偏差分别达到 3.15%和 4.89%。当几何变形（d）接近零时，光子和质子计划的最大剂量偏差均小于序列 A 和 B 的 0.8%。在极端条件下（d=2mm 和 G=4.5%/mm），序列 A 的光子和质子计划的剂量偏差中位数分别达到 3%和 3.49%，序列 B 的光子和质子计划的剂量偏差中位数分别达到 2.93%和 4.55%。我们证明了剂量偏差是特定于 MRI 硬件参数的。与光子计划相比，质子计划对几何变形的变化更敏感。对于典型的临床 MRI 几何变形（d≤2mm），光子和质子计划的中位剂量偏差预计分别在 3%和 5%以内。
