Dieudonné Arnaud, Sanchez-Garcia Manuel, Bando-Delaunay Aurélie, Lebtahi Rachida
Department of Nuclear Medicine, Beaujon Hospital, APHP, Nord, University of Paris Cité, Clichy, France.
Department of Nuclear Medicine, Henri Becquerel Center, Rouen, France.
Front Nucl Med. 2022 Sep 15;2:998793. doi: 10.3389/fnume.2022.998793. eCollection 2022.
This article aims at presenting in a didactic way, dosimetry concepts and methods that are relevant for radio-embolization of the liver with Y-microspheres. The application of the medical internal radiation dose formalism to radio-embolization is introduced. This formalism enables a simplified dosimetry, where the absorbed dose in a given tissue depends on only its mass and initial activity. This is applied in the single-compartment method, partition model, for the liver, tumour and lung dosimetry, and multi-compartment method, allowing identification of multiple tumours. Voxel-based dosimetry approaches are also discussed. This allows taking into account the non-uniform uptake within a compartment, which translates into a non-uniform dose distribution, represented as a dose-volume histogram. For this purpose, dose-kernel convolution allows propagating the energy deposition around voxel-sources in a computationally efficient manner. Alternatively, local-energy deposition is preferable when the spatial resolution is comparable or larger than the beta-particle path. Statistical tools may be relevant in establishing dose-effect relationships in a given population. These include tools such as the logistic regression or receiver operator characteristic analysis. Examples are given for illustration purpose. Moreover, tumour control probability modelling can be assessed through the linear-quadratic model of Lea and Catcheside and its counterpart, the normal-tissue complication probability model of Lyman, which is suitable to the parallel structure of the liver. The selectivity of microsphere administration allows tissue sparing, which can be considered with the concept of equivalent uniform dose, for which examples are also given. The implication of microscopic deposition of microspheres is also illustrated through a liver toxicity model, even though it is not clinically validated. Finally, we propose a reflection around the concept of therapeutic index (TI), which could help tailor treatment planning by determining the treatment safety through the evaluation of TI based on treatment-specific parameters.
本文旨在以一种便于教学的方式，介绍与使用钇微球进行肝脏放射性栓塞相关的剂量学概念和方法。文中介绍了医学内照射剂量形式体系在放射性栓塞中的应用。这种形式体系实现了简化的剂量学，即给定组织中的吸收剂量仅取决于其质量和初始活度。这应用于单室法（分区模型），用于肝脏、肿瘤和肺部的剂量学，以及多室法，可用于识别多个肿瘤。还讨论了基于体素的剂量学方法。这使得能够考虑一个区域内的非均匀摄取情况，这转化为非均匀的剂量分布，以剂量体积直方图表示。为此，剂量核卷积能够以计算高效的方式在体素源周围传播能量沉积。另外，当空间分辨率与β粒子路径相当或更大时，局部能量沉积更可取。统计工具可能与在特定人群中建立剂量效应关系相关。这些工具包括逻辑回归或接受者操作特征分析等。文中给出了示例用于说明。此外，肿瘤控制概率建模可通过Lea和Catcheside的线性二次模型及其对应模型（适用于肝脏平行结构的Lyman正常组织并发症概率模型）进行评估。微球给药的选择性能够实现组织保护，这可以用等效均匀剂量的概念来考虑，文中也给出了相关示例。尽管尚未经过临床验证，但通过肝脏毒性模型也说明了微球微观沉积的影响。最后，我们围绕治疗指数（TI）的概念提出思考，这有助于通过基于特定治疗参数评估TI来确定治疗安全性，从而定制治疗计划。
