Kirubakaran P¹*, C Sureka², B Sarkar³, S Biswal⁴, S Chattopadhyay⁵, S Mondal⁶, S Roy Chowdhury⁷, K George⁸, J Bhattacharya⁹, P Soren¹⁰, T Shahid¹¹, (1) Bharathiar University, Dharmapuri, TN, IN, (2) Bharathiar University, Coimbatore, ,IN, (3) Apollo Gleneagles Cancer Hospital Kolkata, Kolkata, WB, IN, (4) Apollo Multispeciality Hospital &GLA University, Kolkata, west bengal, IN, (5) Apollo Multispeciality Hospitals, ,,IN, (6) Apollo Multispeciality Hospitals, ,,IN, (7) Apollo Multispeciality Hospitals, ,,IN, (8) Apollo Multispeciality Hospitals, ,,IN, (9) Apollo Multispeciality Hospitals, ,,IN, (10) Apollo Multispeciality Hospitals, ,,IN, (11) Apollo Multispeciality Hospitals, ,,IN

PO-GePV-T-232 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: This study is designed as the comparative analysis of the calculated Vs. measured dose verification (dose to MU verification) for Stereotactic body radiotherapy (SBRT) patients between NovalisTx C-arm and Halcyon-E ring gantry linear accelerator.

Methods: 29 SBRT patients (lung 15, Liver 11, and Spine 3) were immobilized with thermoplastic and (or) vacuum bags and 3D/4D CT scan was acquired with 2mm slice thickness. Target volume and OARs were defined, using PET CT /MRI as appropriate. VMAT plans were created in Eclipse V 15.6 using coplanar + non-coplanar 6MV arcs in Novalis whereas for Halcyon (6FFF) the arcs were limited to coplanar only. The patient receives treatment in the dosimetrically superior plan (13 Novalis, 16 Halcyon) based on the departmental scoring criteria. Both of the plans were verified for TPS calculated and phantom measured dose using pinpoint (0.015cc PTW) and (or) farmer (0.6cc) chamber in 30x30x10 cm3 solid phantom in actual couch position.

Results: The choice of the chamber (pin point/farmer) based on the craniocaudal length and volume of the target. Pin Point and farmer chamber was used for 11 and 18 cases. Mean target volume was 188.9±346.7cc, Average and median prescription dose were 39.3±18.5Gy and 50Gy. Average and median dose per fraction were 10±5 Gy and 10 Gy. Average and median numbers of fractions were 4.5±1.4 and 5.Average percentage point and volumetric dose variation between TPS calculated and Novalis measured dose were 1±2.4% and 1.1±2.4%; for Halcyon its 1.28±3% and 1.45±3% respectively, with no statistical significant (p=0.6) difference using students t-test at a significance level of p<0.05.

Conclusion: C-arm linear accelerator with co-planer and non-coplanar beams and ring gantry linear accelerator with only co-planar beams does not show any variation in TPS calculated and measured dose variation using dose to MU verification for SBRT patients.

Keywords

Not Applicable / None Entered.

Taxonomy

TH- Radiation Dose Measurement Devices: ion chamber: air cavity

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