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Session: Therapy General ePoster Viewing [Return to Session]

Role of MR-Scanning Water Tank in Commissioning of MR-Linac Unit

P Yadav1*, I Das2, (1) Northwestern University Feinberg School of Medicine, Chicago, IL, (2) Northwestern University Feinberg School of Medicine, Chicago, IL


PO-GePV-T-332 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: To study characteristics of a 3D MR-scanning water tank and its utility in MR-linac commissioning and data collection.

Methods: An MR-compatible water tank (PTW-Freiburg) was used for commissioning data on MRIdian linac system with 0.35 T magnetic field and 6MV flattening filter free photon beam. Beam characteristics, depth-dose, profile and output factor were collected using MR-safe detectors for entire field sizes ranging from 1.66x1.66 to 24.1X24.1 cm2. Profiles were collected at dmax , 5 cm, 10 cm and 15 cm. Measured data were compared to the treatment planning (TPS) data. Gamma indices using 1%/1mm were calculated to compared the calculated and measured data.

Results: Using PTW MR-water tank in-line and cross line profiles for all field size collected and were compared with the TPS data that showed a good agreement. The PDD data for all fields showed ±0.2% accuracy with gamma pass rates on more than 98%. The profiles also show good agreement with the TPS data with gamma greater than 95% except in penumbra where it deviated by ±5%. Based on the number of data collected for entire commissioning summing to +100000 data at an internal of 0.5 mm were collected within 3days compared to manual 1D tank limited data in 4-6 weeks indicating significant time saving with high degree of real time confidence in data. Also, the instantaneous accuracy provides comfort with the scanning system.

Conclusion: An MR-Scanning water tank, provides accuracy, comfort and significant time saving for commissioning a MR-linac system. It is highly recommended that a scanning system should be used for commissioning and periodic verification or after repair of the system. The Beamscan not only facilitates the data collection in a shorter time but also helps to analyze the data inline and cross


Dosimetry, MRI, Multiple Scattering


Not Applicable / None Entered.

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