Kampfer Severin, Dobiasch Sophie, Combs Stephanie E, Wilkens Jan J
Department of Radiation Oncology, School of Medicine and Klinikum rechts der Isar, Technical University of Munich (TUM), Munich, Germany; Physics Department, Technical University of Munich (TUM), Garching, Germany.
Department of Radiation Oncology, School of Medicine and Klinikum rechts der Isar, Technical University of Munich (TUM), Munich, Germany; Institute of Radiation Medicine (IRM), Department of Radiation Sciences (DRS), Helmholtz Zentrum München, Neuherberg, Germany.
Z Med Phys. 2024 Nov;34(4):533-541. doi: 10.1016/j.zemedi.2023.03.005. Epub 2023 May 22.
In human radiotherapy a safety margin (PTV margin) is essential for successful irradiation and is usually part of clinical treatment planning. In preclinical radiotherapy research with small animals, most uncertainties and inaccuracies are present as well, but according to the literature a margin is used only scarcely. In addition, there is only little experience about the appropriate size of the margin, which should carefully be investigated and considered, since sparing of organs at risk or normal tissue is affected. Here we estimate the needed margin for preclinical irradiation by adapting a well-known human margin recipe from van Herck et al. to the dimensions and requirements of the specimen on a small animal radiation research platform (SARRP). We adjusted the factors of the described formula to the specific challenges in an orthotopic pancreatic tumor mouse model to establish an appropriate margin concept. The SARRP was used with its image-guidance irradiation possibility for arc irradiation with a field size of 10 × 10 mm for 5 fractions. Our goal was to irradiate the clinical target volume (CTV) of at least 90% of our mice with at least 95% of the prescribed dose. By carefully analyzing all relevant factors we gain a CTV to planning target volume (PTV) margin of 1.5 mm for our preclinical setup. The stated safety margin is strongly dependent on the exact setting of the experiment and has to be adjusted for other experimental settings. The few stated values in literature correspond well to our result. Even if using margins in the preclinical setting might be an additional challenge, we think it is crucial to use them to produce reliable results and improve the efficacy of radiotherapy.
在人类放射治疗中，安全边界（计划靶体积边界）对于成功照射至关重要，通常是临床治疗计划的一部分。在小动物的临床前放射治疗研究中，也存在大多数不确定性和不准确性，但根据文献，边界很少被使用。此外，关于边界的合适大小只有很少的经验，由于危及器官或正常组织的 sparing 会受到影响，因此应该仔细研究和考虑。在这里，我们通过将 van Herck 等人的一个著名的人类边界配方应用于小动物放射研究平台（SARRP）上的标本尺寸和要求，来估计临床前照射所需的边界。我们将所述公式的因素调整为原位胰腺肿瘤小鼠模型中的特定挑战，以建立合适的边界概念。使用 SARRP 及其图像引导照射功能进行弧照射，野大小为 10×10mm，分 5 次照射。我们的目标是用至少 95%的规定剂量照射至少 90%的小鼠的临床靶体积（CTV）。通过仔细分析所有相关因素，我们在临床前设置中获得了 CTV 到计划靶体积（PTV）的 1.5mm 边界。所述的安全边界强烈依赖于实验的确切设置，并且必须针对其他实验设置进行调整。文献中少数所述值与我们的结果非常吻合。即使在临床前设置中使用边界可能是一个额外的挑战，但我们认为使用它们来产生可靠的结果并提高放射治疗的疗效至关重要。
