Volume staging for arteriovenous malformation SRS treatment using VMAT.
J Appl Clin Med Phys
; 23(12): e13815, 2022 Dec.
Article
in En
| MEDLINE
| ID: mdl-36354977
ABSTRACT
Volume staging involves dividing the target volume into smaller parts and treating each part separately. In this study, the feasibility of volume-staged stereotactic radiosurgery (VS-SRS) on a linear accelerator using volumetric modulated arc therapy (VMAT) and a frameless patient positioning system is investigated. Ten patients, previously treated with hypofractionated stereotactic radiotherapy with arteriovenous malformation (AVM) sized from 1.6 to 4.0 cm in diameter, were selected. VS-SRS plans were created with the VMAT technique on the Varian Eclipse treatment planning system (TPS) using the TrueBeam STx linear accelerator. For each patient, an AVM-VMAT set was planned with the AVM as the target and a PTV-VMAT set using the (PTV = AVM+1 mm) as the target. All targets were divided into two sub-volumes. The TPS data from the AVM-VMAT plans was compared to Gamma Knife (GK) VS-SRS plan data available in the literature. The AVM-VMAT and PTV-VMAT plans were compared to investigate the effect of a 1 mm PTV margin on normal brain (NB) dose. End-to-end testing was performed using a GaFchromic EBT3 film and point-dose measurements. Dosimetric effects of multiple setups were investigated through film-to-film comparisons. Median target dose coverage, NB V12Gy , and conformity index for the AVM-VMAT plans were 97.5%, 17 cm3 , and 0.8, respectively. PTV-VMAT plans attained comparable target dose coverage, but the average NB V12Gy increased by 48.9% when compared to the AVM-VMAT plans. Agreement of point-dose measurements with TPS calculations was -0.6% when averaged over all patients. Gamma analysis passing rates were above 90% for all film-to-film comparisons (2%/1 mm criteria), and for the film to TPS comparison (5%/1 mm). This work suggests that VMAT is capable of producing VS-SRS plans with similar dose falloff characteristics as GK plans. NB dose depends on PTV margin size, and two-stage treatment setups do not appear to contribute additional uncertainty to treatment delivery.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Arteriovenous Malformations
/
Radiosurgery
/
Radiotherapy, Intensity-Modulated
Limits:
Humans
Language:
En
Journal:
J Appl Clin Med Phys
Journal subject:
BIOFISICA
Year:
2022
Document type:
Article
Affiliation country:
Canada