Abstract
OBJECTIVES: Image-guided radiotherapy maximizes therapeutic index of brain irradiation by reducing setup errors during treatment. The aim of study was to analyze setup errors in the radiation treatment of glioblastoma multiforme and if decrease in planning target volume (PTV), margin is feasible using daily cone beam CT (CBCT) and 6D couch correction. MATERIALS AND METHODS: Twenty-one patients (630 fractions of radiotherapy) were studied in which corrections were made in 6 degrees of freedom. We determined setup errors, impact of setup errors of initial three fractions CBCT versus rest of the treatment with daily CBCT, and mean difference in setup errors with or without application of 6D couch and volumetric benefit of reduction of PTV margin from 0.5 cm to 0.3 cm. RESULTS: The mean shift in the conventional directions, namely, vertical, longitudinal, and lateral was 0.17 cm, 0.19 cm, and 0.11 cm. There was significant change in vertical shift when first three fractions were compared with rest of the treatment with daily CBCT. When the effect of 6D couch was nullified, all directions showed increased error with longitudinal shift being significant. The number of setup errors of magnitude >0.3 cm was more significant when only conventional shifts were applied as compared with 6D couch. There was significant decrease in volume of brain parenchyma irradiated when margin of PTV was reduced from 0.5 cm to 0.3 cm. CONCLUSION: Daily CBCT along with 6D couch correction can reduce setup error which allows reduction in PTV margin during radiotherapy planning in turn improving the therapeutic index.
Copyright
Association for Helping Neurosurgical Sick People. This is an open
access article published by Thieme under the terms of the Creative
Commons Attribution-Non Derivative-Non Commercial License, permitting
copying and reproduction so long as the original work is given
appropriate credit.
Contents may not be used for commercial purposes, or
adapted, remixed, transformed or built upon. ( https://creativecommons.org/licenses/by-nc-nd/4.0/
)
This is an open-access article distributed under the terms of the
Creative Commons Attribution-Non Commercial-No Derivatives License, which
permits unrestricted reproduction and distribution, for non-commercial
purposes only; and use and reproduction, but not distribution, of
adapted material for non-commercial purposes only, provided the original
work is properly cited.
