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Session: Therapy General ePoster Viewing [Return to Session]

Towards Real-Time Patient Dosimetry During MR-Guided Radiotherapy

R Toquero1*, H Nusrat2, H Nusrat3, (1) Ryerson University, (2) Sunnybrook Health Sciences Center, Toronto, ON, (3) Sunnybrook Health Sciences Center, Toronto, ON


PO-GePV-T-238 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: MR-guided radiotherapy (MRgRT) includes cutting-edge technology that incorporates MRI with a linear accelerator (MR-Linac). Through MRgRT, real time anatomical and functional information about the patient can be used for treatment plan adaptation. Given that the patient remains in the same position during imaging, treatment planning, and delivery, pre-treatment patient-specific QA (PSQA) is not feasible. Instead, in most cases PSQA is completed after the treatment fraction has been delivered. This presents potential safety concerns because issues normally found prior to treatment delivery (via PSQA) will be only detected after the patient has been treated. The goal of this work is to develop a real-time dosimetry system to indirectly measure the dose distribution delivered to the patient during treatment delivery.

Methods: The detector system was optimized using the GEANT4 Monte Carlo software package. In the simulation, plastic scintillator detectors (PSDs) were created and their composition, position, and dimensions were optimized. Initially, a single ring of scintillator detectors surrounding a water phantom was created and validated. Following this, a cylindrical scintillator lattice was constructed. GEANT4 was used to evaluate the visible light emitted by all scintillators; this light signal was correlated with photon fluence before and after entering the water phantom, which was then used to determine the dose distribution. The dose at a point calculated using the light deconvolution algorithm was compared to the dose calculated by GEANT4.

Results: For a monoenergetic 6 MeV photon beam, the dose at a point in the water phantom determined using scintillator light output was found to be 19.1% (+ 4.6%) less than the dose calculated by GEANT4.

Conclusion: Preliminary results demonstrate this to be a potentially viable option to measure dose in real-time using PSDs. Future steps include further validation with complex shapes and beam arrangements, followed by the construction of a prototype.


Dosimetry, Scintillators, Operations Research


TH- External Beam- Photons: portal dosimetry, in-vivo dosimetry and dose reconstruction

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