Relaxing leaf-motion restrictions in dynamic multileaf collimator leaf sequencing.

Abstract:

PURPOSE:Traditionally, unidirectional leaf-sweeping schemes have been employed to deliver IMRT plans using the dynamic multileaf collimator (DMLC) technique. The goal of this research is to investigate the potential impact of relaxing the leaf-motion restrictions in DMLC IMRT on the beam-modulation quality and the delivery efficiency. METHODS:This research relaxes the initial and final leaf-position constraints as well as the unidirectional leaf-motion restriction that have been traditionally imposed on DMLC leaf sequencing and develops exact and heuristic solution approaches to allow for an unconstrained and bidirectional leaf motion. The exact approach employs mixed-integer programming (MIP) techniques and the proposed heuristic method uses stochastic search algorithms while utilizing the special structure of the problem. The trade-off between beam-modulation quality and delivery efficiency is quantified and compared to that of unidirectional leaf-sweeping schemes. RESULTS:The performance of the developed approaches is tested on liver and head-and-neck cancer cases. Results validate that unconstrained leaf trajectories can significantly improve the beam-modulation quality at small beam-on time values. However, this gain reduces as the available beam-on time increases. Additionally, the proposed heuristic approach can achieve near-optimal solutions with significantly smaller computational effort compared to the MIP solution approach. CONCLUSIONS:Unconstrained leaf trajectories have the potential to enhance the fluence-modulation quality for cases in which the available beam-on time is limited. This gain is primarily attributed to the relaxation of the initial and final leaf positions. The unidirectionality restriction alone does not appear to be a limiting factor.

journal_name

Med Phys

journal_title

Medical physics

authors

Mirzapour SA,Salari E

doi

10.1002/mp.13158

subject

Has Abstract

pub_date

2018-11-01 00:00:00

pages

5263-5276

issue

11

eissn

0094-2405

issn

2473-4209

journal_volume

45

pub_type

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