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

Development of End-to-End Preclinical Treatment Verification Procedures, Traceable to NPL Air Kerma Primary Standard

In Vivo Dosimetry, SMALL-FIELD, Treatment Plan QA, kV Photon, Adaptive RT, Fundamental Research, Phantom QA, Quality Assurance, Rabiobiology, Real-time Dosimetry Show more

Dosimetry audits are an important tool to improve quality of reported results and to support standardization of preclinical radiation research. This work presents how the combination of passive and active detectors, such as the real-time HYPERSCINT scintillation dosimetry solution, with anatomically correct mouse phantoms are adequate for the development of End-to-End dosimetry audits for the independent verification of preclinical radiation treatments.

The traceability of the detectors’ calibration to primary standards strengthens the dosimetry chain in the validation of preclinical plans, and it is consistent with the current practice for dose traceability of clinical radiotherapy treatments. Their implementation at national and regional levels could lead to databases of anonymised records, which will positively impact the dissemination of best practices and sharing of validated results.

6th Conference on small animal precision image-guided radiotherapy
Ileana Silvestre Patallo (1), Rebecca Carter (2)(3), Andrew Nisbet (2), Anna Subiel (1), Giuseppe Schettino (1) | 1. National Physical Laboratory, UK, 2. University College London, UK, 3. Cancer Institut, UK

Plastic scintillator dosimetry of ultrahigh dose-rate 200 MeV electrons at CLEAR

FLASH-RT, Fundamental research, MeV Electron, Custom Probe Development, Fundamental Research, Real-time Dosimetry Show more

Very high energy electron (VHEE) beams with energies greater than 100 MeV may be promising candidates for FLASH radiotherapy due to their favourable dose distributions and accessibility of ultrahigh dose-rates (UHDR). The standard dosimeters used for conventional radiotherapy, including ionization chambers and film, have limited application to UHDR radiotherapy due to deficits in dose rate independence and temporal resolution. The performance of PSDs in this work suggest they may be useful real-time dosimeters for applications in UHDR VHEE radiotherapy.

IEEE Xplore
Alexander Hart (1), Cloé Giguère (2,6), Joseph Bateman (3,4), Pierre Korysko (3,4), Wilfrid Farabolini (3), Vilde Rieker (3,5), Nolan Esplen (1), Roberto Corsini (3), Manjit Dosanjh (3,4), Luc Beaulieu(2,6), Magdalena Bazalova-Carter (1) | 1. Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada, 2. Département de Physique, de génie Physique et d’optique et Centre de Recherche sur le Cancer, Université Laval, Quebec, QC, Canada, 3. CERN, Geneva, Switzerland, 4. Department of Physics, University of Oxford, Oxford, United Kingdom, 5. Department of Physics, University of Oslo, Oslo, Norway, 6. Département de radio-oncologie et Axe Oncologie duCRCHUde Québec, CHUde Québec – Universit é Laval, Quebec, QC, 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