Abstract：
OBJECTIVE: In radiotherapy, the dose and volumes of the irradiated normal tissues is correlated to the complication rate. We assessed the performances of low-energy proton therapy (ocular PT) with eye-dedicated equipment, high energy PT with pencil-beam scanning (PBS) or CyberKnifeR -based stereotactic irradiation (SBRT).
METHODS: CT-based comparative dose distribution between external beam radiotherapy techniques was assessed using an anthropomorphic head phantom. The prescribed dose was 60Gy_RBE in 4 fractions to a typical posterior pole uveal melanoma. Clinically relevant structures were delineated, and doses were calculated using radiotherapy treatment planning softwares and measured using Gafchromic dosimetry films inserted at the ocular level.
RESULTS: Precision was significantly better with ocular PT than both PBS or SBRT in terms of beam penumbra (80%-20%: laterally 1.4 vs. ≥10mm, distally 0.8 vs. ≥2.5mm). Ocular PT duration was shorter, allowing eye gating and lid sparing more easily. Tumor was excellent with all modalities, but ocular PT resulted in more homogenous and conformal dose compared to PBS or SBRT. The maximal dose to ocular/orbital structures at risk was smaller and often null with ocular PT compared to other modalities. Mean dose to ocular/orbital structures was also lower with ocular PT. Structures like the lids and lacrimal punctum could be preserved with ocular PT using gaze orientation and lid retractors, which is easier to implement clinically than with the other modalities. The dose to distant organs was null with ocular PT and PBS, in contrast to SBRT.
CONCLUSIONS: ocular PT showed significantly improved beam penumbra, shorter treatment delivery time, better dose homogeneity, and reduced maximal/mean doses to critical ocular structures compared with other current external beam radiation modalities. Similar comparisons may be warranted for other tumor presentations.
METHODS: CT-based comparative dose distribution between external beam radiotherapy techniques was assessed using an anthropomorphic head phantom. The prescribed dose was 60Gy_RBE in 4 fractions to a typical posterior pole uveal melanoma. Clinically relevant structures were delineated, and doses were calculated using radiotherapy treatment planning softwares and measured using Gafchromic dosimetry films inserted at the ocular level.
RESULTS: Precision was significantly better with ocular PT than both PBS or SBRT in terms of beam penumbra (80%-20%: laterally 1.4 vs. ≥10mm, distally 0.8 vs. ≥2.5mm). Ocular PT duration was shorter, allowing eye gating and lid sparing more easily. Tumor was excellent with all modalities, but ocular PT resulted in more homogenous and conformal dose compared to PBS or SBRT. The maximal dose to ocular/orbital structures at risk was smaller and often null with ocular PT compared to other modalities. Mean dose to ocular/orbital structures was also lower with ocular PT. Structures like the lids and lacrimal punctum could be preserved with ocular PT using gaze orientation and lid retractors, which is easier to implement clinically than with the other modalities. The dose to distant organs was null with ocular PT and PBS, in contrast to SBRT.
CONCLUSIONS: ocular PT showed significantly improved beam penumbra, shorter treatment delivery time, better dose homogeneity, and reduced maximal/mean doses to critical ocular structures compared with other current external beam radiation modalities. Similar comparisons may be warranted for other tumor presentations.
摘要：
目的：在放射治疗中，受照射的正常组织的剂量和体积与并发症发生率相关。我们使用眼睛专用设备评估了低能量质子治疗（眼部PT）的性能，具有铅笔束扫描（PBS）或基于CyberKnifeR的立体定向辐照（SBRT）的高能PT。
方法：使用拟人化头部体模评估了基于CT的外照射放射治疗技术之间的比较剂量分布。对于典型的后极葡萄膜黑色素瘤，规定剂量为4分60Gy_RBE。划定了临床相关结构，使用放射治疗计划软件计算剂量，并使用插入眼水平的Gafchromr剂量测定胶片进行测量。
结果：在光束半影方面，眼PT的精度明显优于PBS或SBRT（80％-20％：横向1.4vs.≥10mm,远端0.8vs.≥2.5mm)。眼部PT持续时间较短，允许眼睛门控和眼睑更容易保留。所有模式的肿瘤都很好，但与PBS或SBRT相比，眼部PT导致更均匀和适形的剂量。与其他方式相比，眼PT对有风险的眼/眼眶结构的最大剂量较小，通常为零。眼PT对眼睛/眼眶结构的平均剂量也较低。使用注视定向和眼睑牵开器，可以通过眼部PT保留眼睑和泪点等结构，这比其他方式更容易在临床上实施。眼PT和PBS对远处器官的剂量无效，与SBRT相反。
结论：眼PT显示光束半暗带显著改善，更短的治疗交付时间，更好的剂量均匀性，与其他当前的外部束辐射方式相比，减少了对关键眼部结构的最大/平均剂量。对于其他肿瘤表现，可能需要进行类似的比较。
方法：使用拟人化头部体模评估了基于CT的外照射放射治疗技术之间的比较剂量分布。对于典型的后极葡萄膜黑色素瘤，规定剂量为4分60Gy_RBE。划定了临床相关结构，使用放射治疗计划软件计算剂量，并使用插入眼水平的Gafchromr剂量测定胶片进行测量。
结果：在光束半影方面，眼PT的精度明显优于PBS或SBRT（80％-20％：横向1.4vs.≥10mm,远端0.8vs.≥2.5mm)。眼部PT持续时间较短，允许眼睛门控和眼睑更容易保留。所有模式的肿瘤都很好，但与PBS或SBRT相比，眼部PT导致更均匀和适形的剂量。与其他方式相比，眼PT对有风险的眼/眼眶结构的最大剂量较小，通常为零。眼PT对眼睛/眼眶结构的平均剂量也较低。使用注视定向和眼睑牵开器，可以通过眼部PT保留眼睑和泪点等结构，这比其他方式更容易在临床上实施。眼PT和PBS对远处器官的剂量无效，与SBRT相反。
结论：眼PT显示光束半暗带显著改善，更短的治疗交付时间，更好的剂量均匀性，与其他当前的外部束辐射方式相比，减少了对关键眼部结构的最大/平均剂量。对于其他肿瘤表现，可能需要进行类似的比较。
