Impact of using linear optimization models in dose planning for HDR brachytherapy

作     者：Holm, Asa Larsson, Torbjorn Tedgren, Asa Carlsson 

作者机构：Linkoping Univ Dept Math SE-58183 Linkoping Sweden Linkoping Univ Dept Med & Hlth Sci IMH SE-58185 Linkoping Sweden Swedish Radiat Safety Author SE-17116 Stockholm Sweden 

出 版 物：《MEDICAL PHYSICS》 (医疗物理学)

年 卷 期：2012年第39卷第2期

页      面：1021-1028页

核心收录：

学科分类：1001[医学-基础医学(可授医学、理学学位)] 1009[医学-特种医学] 10[医学] 

主　　题：brachytherapy optimization treatment planning linear programming piecewise linear functions 

摘      要：Purpose: Dose plans generated with optimization models hitherto used in high-dose-rate (HDR) brachytherapy have shown a tendency to yield longer dwell times than manually optimized plans. Concern has been raised for the corresponding undesired hot spots, and various methods to mitigate these have been developed. The hypotheses upon this work is based are (a) that one cause for the long dwell times is the use of objective functions comprising simple linear penalties and (b) that alternative penalties, as these are piecewise linear, would lead to reduced length of individual dwell times. Methods: The characteristics of the linear penalties and the piecewise linear penalties are analyzed mathematically. Experimental comparisons between the two types of penalties are carried out retrospectively for a set of prostate cancer patients. Results: When the two types of penalties are compared, significant changes can be seen in the dwell times, while most dose-volume parameters do not differ significantly. On average, total dwell times were reduced by 4.2%, with a reduction of maximum dwell times by 25%, when the alternative penalties were used. Conclusions: The use of linear penalties in optimization models for HDR brachytherapy is one cause for the undesired long dwell times that arise in mathematically optimized plans. By introducing alternative penalties, a significant reduction in dwell times can be achieved for HDR brachytherapy dose plans. Although various measures for mitigating the long dwell times are already available, the observation that linear penalties contribute to their appearance is of fundamental interest. (C) 2012 American Association of Physicists in Medicine. [DOI: 10.1118/1.3676179]