Abstract：
(1) Background: Radiotherapeutic treatments of ocular tumors are often challenging because of nearby radiosensitive structures and the high doses required to treat radioresistant cancers such as uveal melanomas. Although increased local control rates can be obtained with advanced techniques such as proton therapy and stereotactic radiosurgery, these modalities are not always accessible to patients (due to high costs or low availability) and side effects in structures such as the lens, eyelids or anterior chamber remain an issue. Minibeam radiation therapy (MBRT) could represent a promising alternative in this regard. MBRT is an innovative new treatment approach where the irradiation field is composed of multiple sub-millimetric beamlets, spaced apart by a few millimetres. This creates a so-called spatial fractionation of the dose which, in small animal experiments, has been shown to increase normal tissue sparing while simultaneously providing high tumour control rates. Moreover, MBRT with orthovoltage X-rays could be easily implemented in widely available and comparably inexpensive irradiation platforms. (2) Methods: Monte Carlo simulations were performed using the TOPAS toolkit to evaluate orthovoltage X-ray MBRT as a potential alternative for treating ocular tumours. Dose distributions were simulated in CT images of a human head, considering six different irradiation configurations. (3) Results: The mean, peak and valley doses were assessed in a generic target region and in different organs at risk. The obtained doses were comparable to those reported in previous X-ray MBRT animal studies where good normal tissue sparing and tumour control (rat glioma models) were found. (4) Conclusions: A proof-of-concept study for the application of orthovoltage X-ray MBRT to ocular tumours was performed. The simulation results encourage the realisation of dedicated animal studies considering minibeam irradiations of the eye to specifically assess ocular and orbital toxicities as well as tumour response. If proven successful, orthovoltage X-ray minibeams could become a cost-effective treatment alternative, in particular for developing countries.
摘要：
（1）背景：眼部肿瘤的放射治疗通常具有挑战性，因为附近的放射敏感结构和治疗放射性抵抗癌症如葡萄膜黑色素瘤所需的高剂量。尽管可以通过质子治疗和立体定向放射外科等先进技术获得更高的局部控制率，这些模式并不总是为患者（由于高成本或低可用性）和副作用的结构，如晶状体，眼睑或前房仍然是一个问题。在这方面，微型束放射治疗（MBRT）可以代表一种有希望的替代方案。MBRT是一种创新的新治疗方法，其中辐照场由多个亚毫米波子束组成，间隔几毫米。这产生了所谓的剂量空间分割，在小动物实验中，已被证明可以增加正常组织的保留，同时提供高肿瘤控制率。此外，具有正电压X射线的MBRT可以在广泛可用且相对便宜的辐照平台中容易地实现。（2）方法：使用TOPAS工具包进行蒙特卡罗模拟，以评估正电压X射线MBRT作为治疗眼部肿瘤的潜在替代方法。在人体头部的CT图像中模拟了剂量分布，考虑六种不同的辐照配置。(3)结果：平均值，在一般目标区域和不同的危险器官中评估峰值和谷值剂量.获得的剂量与先前的X射线MBRT动物研究中报道的剂量相当，其中发现了良好的正常组织保留和肿瘤控制（大鼠神经胶质瘤模型）。（4）结论：对正电压X射线MBRT在眼部肿瘤中的应用进行了概念验证研究。模拟结果鼓励考虑眼睛的小光束照射的专用动物研究的实现,以具体地评估眼睛和眼眶毒性以及肿瘤反应。如果证明成功,正电压X射线小束可以成为一种具有成本效益的治疗替代方案，特别是对于发展中国家。
