Yan P, Horowiz D, Schweizer M, Chao C
Columbia University Medical Center, New York, NY.
New York Presbyterian Hospital, New York, NY.
Med Phys. 2012 Jun;39(6Part19):3835. doi: 10.1118/1.4735653.
A treatment planning study was performed to compare fixed field IMRT, coplanar and noncoplanar VMAT.
Treatment planning CT scans of three lung cancer patients with small (2244cc), medium (2845cc) and large (3531cc) lungs were used to create simulated patient cases. For each simulated patient, three spherical tumors (GTV) of varying diameters: 1, 3, 5 cm were contoured onto lung CT scans. The ITV was set as GTV+2 cm and the PTV was set as ITV+1 cm. The location of the tumor was set in the right middle lobe of lung. For each patient scenario, the IMRT (nine static fields), single coplanar arc VMAT and 5 noncoplanar arcs VMAT treatment plans were generated using Pinnacle treatment planning system. The arcs of noncoplanar VMAT were set at -30° (clockwise and counterclockwise), 0° and 30° (clockwise and counterclockwise). Thetreatment plans were evaluated by calculation of V100%, V80%, V50% and V20%, DVH of dose constrain rings (DCR) at PTV+1cm, +2cm, +3cm, +4cm and Paddick Conformity Index (CI: 0-1 best) and Gradient Index (GI:the smaller the better).
The V100% and V80% were similar for all the plans but the V50% and V20% were the largest for IMRT, and the smallest for noncoplanar VMAT. The noncoplanar VMAT had larger V<20but smaller V>20 for all the DCRs comparing to the other two plans. The CI of noncoplanar VMAT was slightly larger than the other two plans. The GI was the smallest for noncoplanar VMAT and the largest for IMRT for all the simulation scenarios.
The noncoplanar VMAT consistently provides high dose conformity to the target and low dose to healthy tissue. The noncoplanar VMAT has larger low dose volume while smaller high dose volume comparing to IMRT and coplanar VMAT.
进行一项治疗计划研究，以比较固定野调强放疗（IMRT）、共面和非共面容积调强弧形放疗（VMAT）。
利用三位肺癌患者的治疗计划CT扫描数据，其肺容积分别为小（2244立方厘米）、中（2845立方厘米）和大（3531立方厘米），创建模拟患者病例。对于每个模拟患者，在肺部CT扫描上勾勒出三个不同直径（1厘米、3厘米、5厘米）的球形肿瘤（大体肿瘤体积，GTV）。内部靶区（ITV）设定为GTV加2厘米，计划靶区（PTV）设定为ITV加1厘米。肿瘤位置设定在右肺中叶。对于每个患者情况，使用Pinnacle治疗计划系统生成IMRT（九个静态野）、单弧共面VMAT和五弧非共面VMAT治疗计划。非共面VMAT的弧设置为-30°（顺时针和逆时针）、0°以及30°（顺时针和逆时针）。通过计算V100%、V80%、V50%和V20%、PTV加1厘米、加2厘米、加3厘米、加4厘米处剂量约束环（DCR）的剂量体积直方图（DVH）以及帕迪克适形指数（CI：0至1最佳）和梯度指数（GI：越小越好）来评估治疗计划。
所有计划的V100%和V80%相似，但IMRT的V50%和V20%最大，非共面VMAT的最小。与其他两个计划相比，非共面VMAT在所有DCR处的V<20更大，但V>20更小。非共面VMAT的CI略大于其他两个计划。在所有模拟情况下，非共面VMAT的GI最小，IMRT的最大。
非共面VMAT始终能为靶区提供高剂量适形性，并减少对健康组织的剂量。与IMRT和共面VMAT相比，非共面VMAT的低剂量体积更大，高剂量体积更小。
