An Investigation of Novel Treatment Approaches Using GRID Therapy On the Xstrahl Small Animal Radiation Research Platform
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PO-GePV-T-97 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To validate commissioning results associated with the Xstrahl Small Animal Radiation Research Platform (SARRP) installed at Duke University in October 2021, verify the accuracy of the Xstrahl Point Dose Calculator (PDC) and MuriPlan dose calculation in simple geometries, and design and characterize a novel in-house kV mini-GRID capability on the SARRP.
Methods: Xstrahl SARRP TG-61 output and half-value layer were measured for independent verification using a Farmer ion chamber. The accuracy of the PDC was investigated in simple water and bolus stack phantoms using EBT3 film. A range of field sizes (10x10, 20x20, 30x30, 40x40, 10x20, 20x10, 15x40, 10x40, 30x70 mm2) and depths (1 cm, 2 cm) were spot-checked. MuriPlan simulations of the same geometries were performed. Metal Oxide Semiconductor Field Effect Transistor (MOSFET) detectors were also used for verification of the PDC, with detectors being embedded within a tissue-equivalent mouse phantom. Pencil and bar GRID with beamlet spacings of 1 mm and 1.25 mm, respectively, were characterized using the SARRP, including output factors, peak-to-valley ratios, and dose volume histograms for each GRID.
Results: TG-61 output and half-value layer showed excellent agreement with Xstrahl commissioning results (<1% error). The PDC and MuriPlan dose calculation predicted results for field sizes and depths demonstrated acceptable agreement with actual results measured by EBT3 film and MOSFET detectors (.2% - 25% error, depending on verification modality). Output factors, peak:valley ratios, and dose maps for the pencil and bar GRIDs using the SARRP largely corroborated the results of Johnson et al.
Conclusion: The PDC and MuriPlan computations provide an effective estimate of the exposure time necessary to deliver dose for corresponding MVC field sizes and depths. Xstrahl’s SARRP was able to replicate the kV mini-GRID capabilities of the XRAD 225Cx used in Johnson et al. and can be used for mini-GRID therapy preclinical trials.
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