Comparative Dosimetric, Setup Margin and Treatment Time Analysis Between Ring Gantry and C-Arm Linear Accelerators for VMAT Based Craniospinal Irradiation Plans
S Biswal1*, B Sarkar2, M Goyal3, (1) Apollo Multispeciality Hospital &GLA University, Kolkata, west bengal, IN, (2) AMRI Cancer Centre, Kolkata, WB, IN, (3) Gla University,mathura, ,,IN
Presentations
PO-GePV-T-274 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
ePoster Forums
Purpose: The purpose of this study is to evaluate the dosimetric and treatment delivery characteristic of VMAT based CSI between ring gantry Halcyon (HAL) and C-arm based Novalis Tx (NTx) linear accelerator. Set up margin and treatment delivery time for both the machines also taken in account.
Methods: 15 patients,4 female and 11 male treated between March-2019 and Feb-2022 within the age group 4-56 yrs. simulated in the supine position and are planned with multiple isocentre VMAT technique in ring gantry Halcyon and C-Arm Novalis linear accelerator for 6FFF and 6MV flatten beam energy. Total on-couch time and patient positional shift was captured for each isocentre during each session of treatment. Margins are calculated using Herk’s formula of margin= 2.5Σ + 0.7σ. Dosimetry, On-couch time, and setup margin was compared between two competing arms
Results: 95%PTV coverage(p=0.333), volume receiving 107%(p=0.676),total MU (p=0.818). in both the arms are comparable and statically insignificant. Low dose spillage like D20% (p=0.212) and D50%(p=0.008) is lesser in Halcyon comparable to NovalisTx. CI, HI are statically insignificant. Out of 26 OAR, only 3 organs show a statically significant dose difference. Mean and maximum setup margin In any linear direction is 0.45 and 0.53 cm for HAL and 0.37 and 0.56 cm for NTx and, variation is statistically insignificant ( 0.23
Conclusion: Ring gantry Halcyon and C-arm Novalis Tx, with most of the delivery parameters different, have a very minimal difference in the treatment plan (dosimetry) or in the setup margin. Halcyon gives a faster treatment time delivery, which could be crucial for some selective cases like patients receiving treatment under general anthesis.
Keywords
Setup Errors, Dosimetry, Rotational Therapy
Taxonomy
TH- External Beam- Photons: treatment planning/virtual clinical studies
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