Forward treatment planning techniques to reduce the normalization effect in Gamma Knife radiosurgery

Hao Wen Cheng, Wei Lun Lo, Chun Yuan Kuo, Yu-Kai Su, Jo Ting Tsai, Jia Wei Lin, Yu Jen Wang, David Hung Chi Pan

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


In Gamma Knife forward treatment planning, normalization effect may be observed when multiple shots are used for treating large lesions. This effect can reduce the proportion of coverage of high-value isodose lines within targets. The aim of this study was to evaluate the performance of forward treatment planning techniques using the Leksell Gamma Knife for the normalization effect reduction. We adjusted the shot positions and weightings to optimize the dose distribution and reduce the overlap of high-value isodose lines from each shot, thereby mitigating the normalization effect during treatment planning. The new collimation system, Leksell Gamma Knife Perfexion, which contains eight movable sectors, provides an additional means to reduce the normalization effect by using composite shots. We propose different techniques in forward treatment planning that can reduce the normalization effect. Reducing the normalization effect increases the coverage proportion of higher isodose lines within targets, making the high-dose region within targets more uniform and increasing the mean dose to targets. Because of the increase in the mean dose to the target after reducing the normalization effect, we can set the prescribed marginal dose at a higher isodose level and reduce the maximum dose, thereby lowering the risk of complications.

Original languageEnglish
Pages (from-to)114-122
Number of pages9
JournalJournal of Applied Clinical Medical Physics
Issue number6
Publication statusPublished - Nov 2017


  • Gamma Knife
  • Normalization effect
  • Stereotactic radiosurgery
  • Treatment planning

ASJC Scopus subject areas

  • Radiation
  • Instrumentation
  • Radiology Nuclear Medicine and imaging


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