Development and first implementation of a novel multi-modality cardiac motion and dosimetry phantom for radiotherapy applications

MR-LINAC, Treatment Plan QA, MV Photon, Adaptive RT, Multi-point, Phantom QA, Quality Assurance, Real-time Dosimetry Show more

Magnetic resonance guided radiation therapy (MRgRT) for real-time gating around the heart for treating ventricular tachycardia (VT) are rapidly advancing. A novel, multi-modality modular heart phantom was developed and utilized in gated radiotherapy experiments on a 0.35 T MR-linac. This phantom can simulate cardiac, cardio-respiratory, and respiratory motions, and perform dosimetric evaluations using ionization chamber and plastic scintillation detectors (PSD from MEDSCINT) configurations.

Due to their small sensitive volumes, time-resolved PSDs are effective for low-amplitude/high-frequency movements and multi-point data acquisition, enhancing dosimetric capabilities. This advancement in VT planning and delivery illustrates the phantom’s potential to meet the growing demands of cardiac applications in radiotherapy.

MEDICAL PHYSICS
Kenneth W. Gregg (1,2), Chase Ruff (1,2), Grant Koenig (3), Kalin I. Penev (3), Andrew Shepard (1), Grace Kreissler (4), Margo Amatuzio (4), Cameron Owens (4), Prashant Nagpal (5), Carri K. Glide-Hurst (1,2) | 1. Department of Human Oncology, University of Wisconsin–Madison, Madison, Wisconsin, USA, 2. Department of Medical Physics, University of Wisconsin–Madison, Madison, Wisconsin, USA, 3. Modus Medical Devices, Inc. (IBA QUASAR),London, Ontario, Canada, 4. Department of Biomedical Engineering, University of Wisconsin–Madison, Madison, Wisconsin, USA, 5. Department of Radiology, University of Wisconsin–Madison, Madison, Wisconsin, USA

Characterization of a multi-point scintillation dosimetry research platform for a low-field MR-Linac

Commissioning, In Vivo Dosimetry, MR-LINAC, MV Photon, Adaptive RT, Angular dependancy, Beam characterization, Commissioning, Quality Assurance, Real-time Dosimetry Show more

Plastic scintillation detectors (PSDs) are attractive for enhancing MRI-guided radiation therapy (MRgRT). A study evaluating the HYPERSCINT RP-200, a multi-probe PSD system, demonstrated excellent repeatability and minimal deviation in performance metrics such as detector response and percent depth dose (PDD). PSDs maintained consistent linearity across a broad range of monitor units and showcased high accuracy in gating experiments (ex. gating experiments where 400 cGy were delivered to isocenter : < 0.8 cGy variation for central axis measures and < 0.7 cGy for the gradient sampled region). These results highlight PSDs' huge potential in improving the precision and reliability of MRgRT, especially in complex real-time applications.

MEDICAL PHYSICS
Jennie Crosby (1), Chase Ruff (1), Ken Gregg (1), Jonathan Turcotte (2), Carri Glide-Hurst (1) | 1. Department of Human Oncology, University of Wisconsin-Madison, Madison, Wisconsin, USA, 2. Medscint, Québec, Quebec, Canada

MLC tracking and dose accumulation validation on the MR-linac using a real-time deformable dosimeter

MR-LINAC, Treatment Plan QA, MV Photon, Adaptive RT, Commissioning, Multi-point, Phantom QA, Quality Assurance, Real-time Dosimetry Show more

Online MRI on the MR-linac captures detailed anatomical movements, improving real-time radiotherapy adaptations. However, the lack of a suitable MRI-compatible phantom hinders workflow validation. This study introduces a deformable phantom with integrated real-time scintillation dosimeters, validating accuracy in MLC tracking and dose accumulation using the ELEKTA Unity MR-linac.

This study demonstrates the vast potential of this novel prototype deformable phantom with integrated PSDs for real-time dosimetry measurements on an MR-linac.

2024 ESTRO Annual Congress
Madelon van den Dobbelsteen (1), Pim T.S. Borman (1), Laurie J.M. de Vries (1), Sara L. Hackett (1), Kalin Penev (1), Rocco Flores (2), Stephanie Smith (2), Yoan LeChasseur (3), Simon Lambert-Girard (3), Benjamin Côté (3) , Peter L. Woodhead (1)(4), Lando S. Bosma (1), Cornel Zachiu (1), Bas W. Raaymakers (1), Martin F. Fast (1) | 1 University Medical Center Utrecht, Radiotherapy, Utrecht, Netherlands., 2 IBA QUASAR, Modus Medical Devices Inc. London ON, Canada. , 3 Medscint, -, Quebec City, Canada. , 4 Elekta AB, -, Stockholm, Sweden.

Experimental dosimetric verification of the intra-fraction drift correction on the 1.5 T MR-linac

Commissioning, MR-LINAC, MV Photon, Adaptive RT, Commissioning, Multi-point, Quality Assurance, Real-time Dosimetry Show more

MRI-guided online adaptive treatments can improve tumor targeting by adjusting treatment plans in real-time based on cine MR-scans. And to correct the intra-fraction motion, Elekta AB introduced the intra-fraction drift correction (IDC) functionality for the 1.5 T Unity MR-linac.

The IDC is a valuable functionality for fast intra-fraction adaptations and this research experimentally verifies the geometric and dosimetric accuracy of the IDC process using film, scintillation, and diode dosimetry.

ESTRO 2024 Annual Congress
Madelon van den Dobbelsteen, Sara L. Hackett, Stijn Oolbekkink, Bram van Asselen, Prescilla Uijtewaal, Martin F. Fast, Bas W. Raaymakers | University Medical Center Utrecht, Radiotherapy, Utrecht, Netherlands

Evaluation of the HYPERSCINT scintillation dosimetry platform for small-field characterization of a Leksell Gamma Knife

Commissioning, SMALL-FIELD, MV Photon, Beam characterization, Commissioning, Phantom QA, Quality Assurance Show more

The performance of the HYPERSCINT RP-200 with the 0.5mm x 0.5mm detector was evaluated for the characterization of small radiation fields administered using a Leksell Gamma Knife Perfexion radiosurgery device. Overall, our results show that the detector response was in close agreement with Gamma Knife Monte Carlo reference data and film measurements. Based on the obtained results, the plastic scintillation detector shows the potential for rapid validation of output factors and validation of film measurements as well its use in challenging small-field situations encountered with the Gamma Knife.

ISRS 2024 – New York
Mathieu GUILLOT (1), Patrick DELAGE (1), Vincent HUBERT-TREMBLAY (1), Francois THERRIAULT-PROULX (2), Danahé LEBLANC (2) | CHUS – Sherbrooke, Canada, Medscint – Québec, Canada

Performance characterization of a novel hybrid dosimetry insert for simultaneous spatial, temporal, and motion-included dosimetry for MR-linac

Commissioning, MR-LINAC, Treatment Plan QA, MeV Electron, MV Photon, Adaptive RT, Commissioning, Multi-point, Phantom QA, Real-time Dosimetry Show more

The increased treatment complexity and the motion-delivery interplay during stereotactic body radiotherapy (SBRT) on an MR-linac treatments require MR-compatible motion phantoms with time-resolved dosimeters to validate end-to-end workflows. This study demonstrates the excellent suitability of a the Medscint novel hybrid film-scintillators cassette for simultaneous multi-spatial, temporal, and motion-included dosimetry.

MEDICAL PHYSICS
Prescilla Uijtewaal (1), Pim Borman (1), Benjamin Côté (2), Yoan LeChasseur (2), François Therriault-Proulx (2), Rocco Flores (3), Stephanie Smith (3), Grant Koenig (3), Bas Raaymakers (1), Martin Fast (1) | 1. Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands, 2. Medscint, Québec, Quebec, Canada, 3. Modus QA, London, Ontario, Canada

Performance of the HYPERSCINT scintillation dosimetry research platform for the 1.5 T MR-linac

MR-LINAC, Treatment Plan QA, MV Photon, Adaptive RT, Angular dependancy, Detector comparaison, Energy Dependency, Quality Assurance, Real-time Dosimetry Show more

This study demonstrates the suitability of the HYPERSCINT PSD for accurate time- resolved dosimetry measurements in the 1.5 T MR-linac. The excellent performance during continuous MR scanning and during dynamic movement indicates the great potential of the detector to validate end-to-end workflows of online adaptive radiotherapy

PHYSICS IN MEDICINE & BIOLOGY
Prescilla Uijtewaal (1), Benjamin Côté (2), Thomas Foppen (1), J H Wilfred de Vries (1), Simon J Woodings (1), Pim T S Borman (1), Simon Lambert-Girard (2), François Therriault-Proulx (2), Bas W Raaymakers (1), Martin F Fast (1) | 1 – UMC Utrecht, Netherland, 2 – Medscint, Canada

Investigation of temperature dependence of inorganic scintillators using the HYPERSCINT research platform

Advanced Optical Dosimetry, Brachytherapy, Fundamental research, In Vivo Dosimetry, MV Photon, Advanced Optical Dosimetry, Detector comparaison, Fundamental Research, Real-time Dosimetry Show more

The temperature dependence of four inorganic scintillation detectors was examined spectrally using the HYPERSCINT Research Platform 200 under 6 MV photon irradiations from a LINAC. After varying only the temperature of the detectors, all scintillators demonstrated linearity when the change in photon counts with temperature in the full-width at half maximum of their spectrum are integrated. Establishing the magnitude of the temperature dependence of the materials is critical to decide whether correction factors are required. This is especially true in applications such as brachytherapy, where detectors equilibrise to body temperature.

Radiation Measurements
Owen McLaughlin (1), Michael Martyn (1,2), Christoph Kleefeld (1), Mark Foley (1) | 1. Physics Unit, School of Natural Sciences, University of Galway, Galway, Ireland, 2. Galway Clinic, Doughiska, Galway, Ireland

Use of a Commercial Plastic Scintillation Detector for Determination of Detector-Specific Small Field Output Correction Factors of Other Detectors

SMALL-FIELD, MV Photon, Commissioning, Detector comparaison, Monte Carlo, Quality Assurance Show more

The goal of this work is to determine small field output correction factors of various detectors using the HYPERSCINT plastic scintillation detector as a reference and to compare values with current available data. The simple and well understood composition and geometry of the scintillation detector make it ideal to be used as a reference detector for the evaluation of field output correction factors. Field size dependent correction factors have been extracted for different detectors and show limited discrepancies with current available data. This may potentially be attributed to inter detector variability or other methodological uncertainties in published data.

2022 AAPM ANNUAL MEETING
M.Besnier (1), F.Beaulieu (1), F.Berthiaume (1,2), Y.Cervantes Espinosa (1), B.Côté (2), S.Lambert-girard (1,2), D.Leblanc (1,2), Y.Lechasseur (2), F.Therriault-Proulx (2), L.Archambault (1), L.Beaulieu (1), L.Gingras (1) | 1- CHU de Quebec – Universite Laval, QC, Canada, 2- MEDSCINT, QC, Canada