Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain; Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain.
Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain.
Phys Med. 2017 Oct;42:345-352. doi: 10.1016/j.ejmp.2017.03.018. Epub 2017 Mar 31.
Neutron peripheral contamination in high-energy radiotherapy implies an increase of secondary radiation-induced cancer risk. Although peripheral neutron dose (PND) has been evaluated in organs, few studies have been performed regarding patient size. This work aims to improve an existing methodology for adult patient PND estimations to generalize it to young and children, for its implementation in treatment planning systems (TPS).
As a first step, we aimed to generalize the previous model to be usable with any thermal neutron detector. Then, taking into account total neutron spectra and dose-to-point thermal neutron fluence measurements for three phantom sizes (adult, teen and child) and two common treatment locations (H&N and abdomen), the new model was proposed. It represents an upgraded parameterization and extension of the existing one, including patient anatomy. Finally, comparison between estimations and measurements, as well as validation against the original model, was carried out for 510 measured patients.
Concordance found between experimental and theoretical estimations makes us confident about later implementation in treatment planning systems. Comparison among the previous and upgraded models shows no significant differences for the adult case. However, an important underestimation (34.1% on average) can be observed regarding child case for the original one.
An improved generalization of an existing PND model, considering patient anatomy has been validated and used in real patients. The final methodology is easily implementable in clinical routine and TPS thanks to the ready availability of input parameters (patient height and weight, high-energy MU and facility characterization).
高能放射治疗中的中子边缘污染意味着二次辐射诱发癌症风险的增加。尽管已经评估了器官中的边缘中子剂量（PND），但针对患者体型的研究较少。本研究旨在改进现有的成人患者 PND 估算方法，将其推广到年轻人和儿童，以便在治疗计划系统（TPS）中实施。
作为第一步，我们旨在将先前的模型推广到任何热中子探测器都可以使用。然后，考虑到三种体模尺寸（成人、青少年和儿童）和两种常见治疗部位（头颈部和腹部）的总中子能谱和点剂量热中子注量测量值，提出了新模型。它代表了对现有模型的升级和扩展，包括患者解剖结构。最后，对 510 名实测患者进行了估计值与测量值的比较，并与原始模型进行了验证。
实验和理论估计之间的一致性使我们对以后在治疗计划系统中的实施充满信心。原始模型和升级模型的比较表明，成人病例没有显著差异。然而，对于儿童病例，原始模型观察到明显的低估（平均 34.1%）。
已经验证并在实际患者中使用了一种改进的现有 PND 模型的推广，考虑到患者解剖结构。最终的方法由于输入参数（患者身高和体重、高能 MU 和设施特性）的现成可用性，易于在临床常规和 TPS 中实施。
