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Title: SU-E-T-14: A Comparative Study Between Forward and Inverse Planning in Gamma Knife Radiosurgery for Acoustic Neuroma Tumours

Abstract

Purpose: To evaluate forward and inverse planning methods for acoustic neuroma cases treated in Gamma Knife Perfexion. Methods: Five patients with acoustic neuroma tumour abutting brainstem were planned twice in LGP TPS (Version 10.1) using TMR10 algorithm. First plan was entirely based on forward planning (FP) in which each shot was chosen manually. Second plan was generated using inverse planning (IP) for which planning parameters like coverage, selectivity, gradient index (GI) and beam-on time threshold were set. Number of shots in IP was automatically selected by objective function using iterative process. In both planning methods MRI MPRAGE sequence images were used for tumour localization and planning. A planning dose of 12Gy at 50% isodose level was chosen. Results and Discussion: Number of shots used in FP was greater than IP and beam-on time in FP was in average 1.4 times more than IP. One advantage of FP was that the brainstem volume subjected to 6Gy dose (25% isodose) was less in FP than IP. Our results showed use of more number of shots as in FP results in GI less than or equal to 2.55 which is close to its lower limit. Dose homogeneity index (DHI) analysis of FP andmore » IP showed average values of 0.59 and 0.67 respectively. General trend in GK for planning in acoustic neuroma cases is to use small collimator shots to avoid dose to adjacent critical structures. More number of shots and prolonged treatment time causes inconvenience to the patients. Similarly overuse of automatic shot shaping as in IP results in increased scatter dose. A compromise is required in shot selection for these cases. Conclusion: IP method could be used in acoustic neuroma cases to decrease treatment time provided the source sector openings near brainstem are shielded or adjusted appropriately to reduce brainstem dose.« less

Authors:
; ; ; ; ; ;  [1]
  1. All India Institute of Medical Sciences, New Delhi (India)
Publication Date:
OSTI Identifier:
22545149
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ALGORITHMS; COLLIMATORS; ITERATIVE METHODS; NEOPLASMS; NMR IMAGING; PATIENTS; PLANNING; RADIATION DOSES; RADIOTHERAPY; SURGERY

Citation Formats

Gopishankar, N, Agarwal, Priyanka, Bisht, Raj Kishor, Kale, S S, Rath, G K, Chander, S, and Sharma, B S. SU-E-T-14: A Comparative Study Between Forward and Inverse Planning in Gamma Knife Radiosurgery for Acoustic Neuroma Tumours. United States: N. p., 2015. Web. doi:10.1118/1.4924375.
Gopishankar, N, Agarwal, Priyanka, Bisht, Raj Kishor, Kale, S S, Rath, G K, Chander, S, & Sharma, B S. SU-E-T-14: A Comparative Study Between Forward and Inverse Planning in Gamma Knife Radiosurgery for Acoustic Neuroma Tumours. United States. doi:10.1118/1.4924375.
Gopishankar, N, Agarwal, Priyanka, Bisht, Raj Kishor, Kale, S S, Rath, G K, Chander, S, and Sharma, B S. Mon . "SU-E-T-14: A Comparative Study Between Forward and Inverse Planning in Gamma Knife Radiosurgery for Acoustic Neuroma Tumours". United States. doi:10.1118/1.4924375.
@article{osti_22545149,
title = {SU-E-T-14: A Comparative Study Between Forward and Inverse Planning in Gamma Knife Radiosurgery for Acoustic Neuroma Tumours},
author = {Gopishankar, N and Agarwal, Priyanka and Bisht, Raj Kishor and Kale, S S and Rath, G K and Chander, S and Sharma, B S},
abstractNote = {Purpose: To evaluate forward and inverse planning methods for acoustic neuroma cases treated in Gamma Knife Perfexion. Methods: Five patients with acoustic neuroma tumour abutting brainstem were planned twice in LGP TPS (Version 10.1) using TMR10 algorithm. First plan was entirely based on forward planning (FP) in which each shot was chosen manually. Second plan was generated using inverse planning (IP) for which planning parameters like coverage, selectivity, gradient index (GI) and beam-on time threshold were set. Number of shots in IP was automatically selected by objective function using iterative process. In both planning methods MRI MPRAGE sequence images were used for tumour localization and planning. A planning dose of 12Gy at 50% isodose level was chosen. Results and Discussion: Number of shots used in FP was greater than IP and beam-on time in FP was in average 1.4 times more than IP. One advantage of FP was that the brainstem volume subjected to 6Gy dose (25% isodose) was less in FP than IP. Our results showed use of more number of shots as in FP results in GI less than or equal to 2.55 which is close to its lower limit. Dose homogeneity index (DHI) analysis of FP and IP showed average values of 0.59 and 0.67 respectively. General trend in GK for planning in acoustic neuroma cases is to use small collimator shots to avoid dose to adjacent critical structures. More number of shots and prolonged treatment time causes inconvenience to the patients. Similarly overuse of automatic shot shaping as in IP results in increased scatter dose. A compromise is required in shot selection for these cases. Conclusion: IP method could be used in acoustic neuroma cases to decrease treatment time provided the source sector openings near brainstem are shielded or adjusted appropriately to reduce brainstem dose.},
doi = {10.1118/1.4924375},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}