使用可选的锂-6过滤技术改善临床超热中子俘获束的剂量靶向。

Improved dose targeting for a clinical epithermal neutron capture beam using optional (6)Li filtration.

作者信息

Binns Peter J, Riley Kent J, Ostrovsky Yakov, Gao Wei, Albritton J Raymond, Kiger W S, Harling Otto K

机构信息

Nuclear Reactor Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

出版信息

Int J Radiat Oncol Biol Phys. 2007 Apr 1;67(5):1484-91. doi: 10.1016/j.ijrobp.2006.11.022.

DOI:10.1016/j.ijrobp.2006.11.022

PMID:17394946

Abstract

PURPOSE

The aim of this study was to construct a (6)Li filter and to improve penetration of thermal neutrons produced by the fission converter-based epithermal neutron beam (FCB) for brain irradiation during boron neutron capture therapy (BNCT).

METHODS AND MATERIALS

Design of the (6)Li filter was evaluated using Monte Carlo simulations of the existing beam line and radiation transport through an ellipsoidal water phantom. Changes in beam performance were determined using three figures of merit: (1) advantage depth (AD), the depth at which the total biologically weighted dose to tumor equals the maximum weighted dose to normal tissue; (2) advantage ratio (AR), the ratio of the integral tumor dose to that of normal tissue averaged from the surface to the AD; and (3) advantage depth dose rate (ADDR), the therapeutic dose rate at the AD. Dosimetry performed with the new filter installed provided calibration data for treatment planning. Past treatment plans were recalculated to illustrate the clinical potential of the filter.

RESULTS

The 8-mm-thick Li filter is more effective for smaller field sizes, increasing the AD from 9.3 to 9.9 cm, leaving the AR unchanged at 5.7 but decreasing the ADDR from 114 to 55 cGy min(-1) for the 12 cm diameter aperture. Using the filter increases the minimum deliverable dose to deep seated tumors by up to 9% for the same maximum dose to normal tissue.

CONCLUSIONS

Optional (6)Li filtration provides an incremental improvement in clinical beam performance of the FCB that could help to establish a therapeutic window in the future treatment of deep-seated tumors.

摘要

目的

本研究的目的是构建一个⁶Li滤过器，并提高基于裂变转换器的超热中子束（FCB）产生的热中子在硼中子俘获治疗（BNCT）期间用于脑部照射时的穿透能力。

方法和材料

使用现有束流线路的蒙特卡罗模拟以及通过椭圆形水体模的辐射输运来评估⁶Li滤过器的设计。使用三个品质因数来确定束流性能的变化：（1）优势深度（AD），即肿瘤的总生物加权剂量等于正常组织的最大加权剂量时的深度；（2）优势比（AR），即从表面到AD的肿瘤积分剂量与正常组织积分剂量的比值；（3）优势深度剂量率（ADDR），即AD处的治疗剂量率。安装新滤过器后进行的剂量测定为治疗计划提供了校准数据。重新计算过去的治疗计划以说明滤过器的临床潜力。