Ferrer C, Huertas C, Plaza R, de la Monja P, Ocanto A, Escribano A, Pérez A, Sáez M
Department of Medical Physics and Radiation Protection, Hospital Universitario La Paz, Madrid, Spain.
Department of Medical Physics and Radiation Protection, Hospital Universitario La Paz, Madrid, Spain.
Med Dosim. 2021;46(2):201-207. doi: 10.1016/j.meddos.2020.11.003. Epub 2020 Dec 11.
Total lymphoid irradiation (TLI) is used in the management of pediatric allogeneic hematopoietic stem cell transplantation (HSCT. This work aims to simplify the treatment planning process for TLI via a proposed template using the volumetric modulated arc therapy (VMAT) technique. Fifteen pediatric patients were planned, prescribed to 8 Gy in 4 fractions. Cost functions included in the template were the ones for the planning target volume (PTV), and conformality cost function (CCF) for the rest of the patient's volume. Conformity index (CI), homogeneity index (HI), conformation number (CN), gradient index (GI), integral dose, and doses to the organs at risk achieved with the template were reported. Cost function influence over various indexes was studied by Wilcoxon signed ranks test. Same 15 patients were planned with 3-dimensional conventional radiotherapy (3D-CRT) technique for comparison. Mean CI and HI were 1.33 and 0.13, respectively, which indicates good dose conformation and homogeneity. Mean CN and GI values were 0.69 and 4.51, respectively. Mean PTV coverage was reached (V > 95%). No correlation between the CCF and indexes values was found (p > 0.05). Doses to organs at risk (OARs) were as low as possible without losing PTV coverage. VMAT plan showed higher levels of conformation and similar homogeneity as 3D-CRT plans. Doses to OARs were inferior with VMAT except for the right kidney. The proposed template simplifies the planning of TLI treatments, and it is able to create acceptable plans with little modification in order to reduce doses to certain organs like the kidneys or the heart. VMAT technique showed higher conformation and lower doses to OAR compared to 3D-CRT.
全身淋巴照射（TLI）用于小儿异基因造血干细胞移植（HSCT）的治疗。本研究旨在通过使用容积调强弧形治疗（VMAT）技术的拟议模板简化TLI的治疗计划过程。对15例儿科患者进行计划，分4次给予8 Gy的剂量。模板中包含的成本函数是计划靶体积（PTV）的成本函数，以及患者其余体积的适形成本函数（CCF）。报告了使用该模板实现的适形指数（CI）、均匀性指数（HI）、适形数（CN）、梯度指数（GI）、积分剂量以及对危及器官的剂量。通过Wilcoxon符号秩检验研究成本函数对各种指标的影响。对相同的15例患者采用三维常规放疗（3D-CRT）技术进行计划以作比较。平均CI和HI分别为1.33和0.13，这表明剂量适形性和均匀性良好。平均CN和GI值分别为0.69和4.51。达到了平均PTV覆盖率（V>95%）。未发现CCF与指标值之间存在相关性（p>0.05）。在不损失PTV覆盖率的情况下，对危及器官（OARs）的剂量尽可能低。VMAT计划显示出比3D-CRT计划更高的适形水平和相似的均匀性。除右肾外，VMAT对OARs的剂量较低。拟议的模板简化了TLI治疗的计划，并且能够在几乎不做修改的情况下创建可接受的计划，以减少对某些器官如肾脏或心脏的剂量。与3D-CRT相比，VMAT技术显示出更高的适形性和更低的OARs剂量。
