Premium
TH‐A‐137‐04: Continuous Path Radiation Therapy Treatment Planning for Gamma Knife Perfexion
Author(s) -
Ghobadi K,
Aleman D,
Jaffray D,
Ruschin M
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4815686
Subject(s) - mathematics , range (aeronautics) , mathematical optimization , path length , inverse , path (computing) , algorithm , computer science , geometry , computer network , materials science , composite material , programming language
Purpose: The purpose of this work is to develop an inverse planning approach for Gamma Knife Perfexion that continuously delivers the dose over a path in the target. Methods: Our approach consists of two steps: finding a path in the target, and optimizing shot shapes for that path. To obtain the path, a set of well‐positioned isocentres are selected in the target, and then a Hamiltonian path that visits all the isocentres exactly once is found by graph‐theory and spiral‐based approaches. Then, a linear optimization model is solved to obtain the optimal shot shapes and intensities by minimizing dose spillage from the target. The dose restrictions for the target and the organs‐at‐risk are constraints in the optimization. We additionally consider several criteria specific to continuous path, including machine speed constraints, delivery accuracy, preference for single/multiple paths, and smoothness of movement. Results: We tested our approach on seven clinical cases and compared against inverse step‐and‐shoot and manually‐generated forward plans. The mean difference in Paddick CI compared to forward and inverse step‐and‐shoot was 0.04 and −0.04, respectively, while the Classic CI mean difference was −0.05 and 0.05, respectively. The mean dose difference to 1mm ^ 3 brainstem was −0.5Gy (range: −1.6Gy to 0.1 Gy) and −0.24Gy (range: −1.9Gy to 0.9Gy) compared to forward and inverse step‐and‐shoot plans. However, the average beam‐on time improved by 30min (range: −82.9min to −0.62min) and 103min (range: −304min to −9min) over forward and inverse step‐and‐shoot plans, respectively. The mean computational time for continuous path was 19.5min, a 198min improvement over inverse step‐and‐shoot plans. Conclusion: The continuous path treatment plans showed comparable plan quality with forward and inverse step‐and‐shoot plans, while achieving better beam‐on times. The computational time was also improved compared to the inverse step‐and‐shoot approach. This work was by part funded by Elekta, Stockholm, Sweden.