Spatially fractionated (GRID) radiation therapy using proton pencil beam scanning (PBS): Feasibility study and clinical implementation
Spatially fractionated (GRID) radiation therapy using proton pencil beam scanning (PBS): Feasibility study and clinical implementation
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DOI：
10.1002/mp.12807
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发表时间：
2018-04-01
期刊：
影响因子：
3.8
通讯作者：
Pankuch, M.
中科院分区：
文献类型：
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作者：
Gao, M.;Mohiuddin, M. M.;Pankuch, M.
目的：grid疗法是治疗体积较大肿瘤的有效方法。直线加速器（Linac）产生的光子光束通过块或多叶准直器（MLCs）准直是最常用的方法来提供这种治疗。利用最新的质子输送方法铅笔束扫描（PBS）可以进一步提高GRID治疗的疗效。在这项研究中，我们开发了一种使用质子PBS进行GRID治疗的方法，评估了这种新技术的剂量学，并在两个临床病例中应用了这种方法。材料/方法在可行性研究阶段，优化了单个PBS质子束在水模体中以6cm深度为中心的20x20x12cm(3)浅层靶体的非均质照射。光束被限制在所有层中具有相同的斑点模式，在每个斑点位置产生一个光束。另一种使用PBS的GRID治疗也在水模体中以14cm深度为中心的15x15x8cm(3)深的靶体积上进行。将两种PBS剂量分布的剂量学参数与典型光子栅格剂量分布进行了比较。下一阶段，我们中心将有四名患者接受质子GRID技术的治疗。报告了两例代表性患者的计划、剂量学和测量结果。结果对于浅影靶，PBS计划的深度-剂量曲线在靶内均匀（变化95%，γ指数标准为3%/3mm）。患者对治疗耐受良好，无明显皮肤毒性（放射性皮炎1级）。结论采用PBS给药方式的质子GRID治疗已被成功开发并在临床上实施。与光子网格技术相比，质子网格治疗具有许多优点。质子的使用在肿瘤内提供了更均匀的束剂量，并保留了肿瘤外的正常组织。这种新的PBS方法在治疗深部肿瘤时也将减少近端器官的剂量。
PurposeGRID therapy is an effective treatment for bulky tumors. Linear accelerator (Linac)-produced photon beams collimated through blocks or multileaf collimators (MLCs) are the most common methods used to deliver this therapy. Utilizing the newest proton delivery method of pencil beam scanning (PBS) can further improve the efficacy of GRID therapy. In this study, we developed a method of delivering GRID therapy using proton PBS, evaluated the dosimetry of this novel technique and applied this method in two clinical cases.Materials/MethodsIn the feasibility study phase, a single PBS proton beam was optimized to heterogeneously irradiate a shallow 20x20x12cm(3) target volume centered at a 6cm depth in a water phantom. The beam was constrained to have an identical spot pattern in all layers, creating a beamlet at each spot position. Another GRID treatment using PBS was also performed on a deep 15x15x8cm(3) target volume centered at a 14cm depth in a water phantom. Dosimetric parameters of both PBS dose distributions were compared with typical photon GRID dose distributions. In the next phase, four patients have been treated at our center with this proton GRID technique. The planning, dosimetry, and measurements for two representative patients are reported.ResultsFor the shallow phantom target, the depth-dose curve of the PBS plan was uniform within the target (variation 95% with a gamma index criterion of 3%/3mm). Patients tolerated the treatment well without significant skin toxicity (radiation dermatitis grade 1).ConclusionsProton GRID therapy using a PBS delivery method was successfully developed and implemented clinically. Proton GRID therapy offers many advantages over photon GRID techniques. The use of protons provides a more uniform beamlet dose within the tumor and spares normal tissues located beyond the tumor. This new PBS method will also reduce the dose to proximal organs when treating a deep-seated tumor.