Dosimetry for new radiation therapy approaches using high energy electron accelerators

We have performed dosimetry studies using electron beams with energies up to 50 MeV, which exceed current clinical energy ranges and approaches the bottom end of the very high energy electron range. 50 MeV electron beams can reach deep-seated tumors. In contrast to photon beams, electron beams can be generated with ultra-high dose rates by linear accelerators, which could enable FLASH radiotherapy of deep-seated tumors. The response of radiochromic film and alanine is compared with dose measurements using an ionisation chamber. Energy dependence is not observed within the measurement uncertainty in the investigated energy range from 15 to 50 MeV

A physics-based analytical model of absorbed dose from primary, leakage, and scattered photons from megavoltage radiotherapy with MLCs

A burgeoning population of cancer survivors is at risk of late health effects following radiation therapy including second cancers, with the majority of these cancers occurring outside of the treatment volume of the primary cancer. Commercial radiotherapy treatment planning systems underestimate the out-of-field dose. Previous analytical models of out-of-field dose have assumed radial symmetry and/or approximated the dimensions of collimators as semi-infinite planes. The purpose of this work was to develop a physics-based analytical model of total absorbed dose from primary, scattered, and leakage radiation for square fields from a 6 MV beam at any arbitrary point in a phantom, including in-plane, cross-plane, and out-of-plane locations. The model includes the essential physics of radiation transport through beam-limiting-devices including rounded edges of MLC leaves. The model agreed well with measurements and Monte Carlo simulations of absorbed dose in a water-box phantom and was validated for field-sizes ranging from 2 2 to 20 20 cm2. The signed and unsigned average percent differences were and 15.9%, respectively, for all points and field-sizes considered. An extended gamma index analysis reveals a 92% pass rate with criteria of 3 mm distance-to-agreement, 3% relative dose difference in-field, and 3 mGy Gy-1 absolute dose difference out-of-field. The average wall-clock time to calculate dose to one million points was 3.3 min. These results suggest that it is feasible to calculate absorbed dose from both therapeutic and stray radiation using physics-based analytical models with good accuracy, thus overcoming a major obstacle to routinely assessing exposures. Additionally, this work demonstrates the importance of relaxing certain simplifications such as assuming a radially symmetric stray-dose distribution. Because the model is physics-based and may be reconfigured according to the dimensions of beam-limiting-devices, adapting it to other treatment units should be straight forward. Uses for such a model include clinical and research applications, such as clinical trials and epidemiological studies

Method to quickly and accurately calculate absorbed dose from therapeutic and stray photon exposures throughout the entire body in individual patients

Purpose: Photon radiotherapy techniques typically devote considerable attention to limiting the exposure of healthy tissues outside of the target volume. Numerous studies have shown, however, that commercial treatment planning systems (TPSs) significantly underestimate the absorbed dose outside of the treatment field. The purpose of this study was to test the feasibility of quickly and accurately calculating the total absorbed dose to the whole body from photon radiotherapy in individual patients. Methods: We created an extended TPS by implementing a physics-based analytical model for the absorbed dose from stray photons during photon therapy into a research TPS. We configured and validated the extended TPS using measurements of 6- and 15-MV photon beams in water-box and anthropomorphic phantoms. We characterized the additional computation time required for therapeutic and stray dose calculations in a 44 × 30 × 180 cm3 water-box phantom. Results: The extended TPS achieved superior dosimetric accuracy compared to the research TPS in both water and anthropomorphic phantoms, especially outside of the primary treatment field. In the anthropomorphic phantom, the extended TPS increased the generalized gamma index passing rate by a factor of 10 and decreased the median dosimetric discrepancy in the out-of-field region by a factor of 26. The extended TPS achieved an average discrepancy \u3c1% in and near the treatment field and \u3c1 mGy/Gy far from the treatment field in the anthropomorphic phantom. Characterization of computation time revealed that on average, the extended TPS only required 7% longer than the research TPS to calculate the total absorbed dose. Conclusions: The results of this work suggest that it is feasible to quickly and accurately calculate whole-body doses inside and outside of the therapeutic treatment field in individual patients on a routine basis using physics-based analytical dose models. This additional capability enables a more personalized approach to minimizing the risk of radiogenic late effects, such as second cancer and cardiac toxicity, as part of the treatment planning process

EMRP Project HLT 09 – Metrology for radiotherapy using complex radiation fields

This paper is intended to give information about the on-going work of the MetrExtRT research project concerned with the dosimetric metrology of modern external beam radiotherapy. It started on the 1st of June 2012 for duration of 36 months and covers the study medium- and high-energy X-rays, high-energy electrons, electronic brachytherapy and scanned proton and carbon ion beams. The project concerns all the steps of traceability from the primary standards through to verification of the dose in and around the tumour, namely: developing new primary standards of absorbed dose to water; studying new detectors and improving the knowledge of the characteristics of existing detectors, useable for quality control and in vivo dosimetry, and publishing guide lines of good practice on their use. MetrExtRT gathers 10 partners that are all National Metrology Institutes (NMI) or Designated Institutes (DI) as represented by the list of authors, two Researcher Excellence Grants (REG) for the development of passive gel dosimetry (Université d'Auverge – France) and diamond detectors (Tor Vergata University - Italy) and up to now 12 collaborators from industry, oncology centres and universities

Metrology for radiotherapy using complex radiation fields – HLT09 EMRP Project

International audienceCette publication traite des avancées effectuées pendant le cours du projet HLT09 subventionné par EMRP (European Metrology Research Program). Ce projet avait pour objectif global d'améliorer la traçabilité, à des références nationales, de la dose absorbée délivrée à la tumeur dans la cadre d'un traitement par radiothérapie. Les recherches couvrent l'établissement de références absolues en termes de dose absorbée dans l'eau pour les photons d'énergie moyenne, la mise en oeuvre du concept de produit dose surface dans la cadre de l'utilisation des faisceaux de photons de haute énergie, la caractérisation des faisceaux produit par de nouveaux générateurs de rayons X pour la thérapie de contact incluant les étalon primaire et de transfert, l'étude des caractéristiques des détecteurs ponctuels, 2D et 3D en tant qu'étalon de transfert et moyen de contrôle des plans de traitement

Metrology for radiotherapy using complex radiation fields – EMRP Project

International audienceCette publication traite des avancées effectuées pendant le cours du projet HLT09 subventionné par EMRP (European Metrology Research Program). Ce projet avait pour objectif global d'améliorer la traçabilité, à des références nationales, de la dose absorbée délivrée à la tumeur dans la cadre d'un traitement par radiothérapie. Les recherches couvrent l'établissement de références absolues en termes de dose absorbée dans l'eau pour les photons d'énergie moyenne, la mise en oeuvre du concept de produit dose surface dans la cadre de l'utilisation des faisceaux de photons de haute énergie, la caractérisation des faisceaux produit par de nouveaux générateurs de rayons X pour la thérapie de contact incluant les étalon primaire et de transfert, l'étude des caractéristiques des détecteurs ponctuels, 2D et 3D en tant qu'étalon de transfert et moyen de contrôle des plans de traitement

Ionisierende Strahlung in der Medizin (Auszug aus: PTB-Mitteilungen 2013, Band 123, Heft 2. ISSN 0030-834X)

PTB-Mitteilungen. Band 123 (2013), Heft 2, Seite 1 - 81. ISSN 0030-834X1.: Janßen, Herbert: Vorwort 2.: Ankerhold, Ulrike: Ionisierende Strahlung in Diagnostik und Therapie 3.: Büermann, Ludwig: Metrologische Aspekte der Dosimetrie in der Röntgendiagnostik 4.: Kossert, Karsten: Aktivitätsbestimmung von Radionukliden für Diagnostik und Therapie 5.: Ankerhold, Ulrike und Thorsten Schneider: Dosimetrie für die Brachytherapie 6.: Krauss, Achim: Kalorimetrische Bestimmung der Wasser-Energiedosis 7.: Kapsch, Ralf-Peter: Dosimetrie mit Ionisationskammern in der externen Strahlentherapie 8.: Anton, Mathias: Dosimetrie für die externe Strahlentherapie: Dosimetrie mit Alanin 9.: Ambrosi, Peter: Strahlenschutz in der Medizin 10.: Hupe, Oliver: Messgeräte und Herausforderungen in der Strahlenschutzmesstechnik 11.: Ambrosi,Peter, Oliver Hupe und H.-M. Kramer: Messgrößen im Strahlenschutz 12.: Hupe, Oliver: Amtliche Personendosimetrie für Medizin-Personal 13.: Hupe, Oliver: Dosis für helfende Personen in der Human-, Zahn- und Tiermedizin 14: Behrens, Rolf: Teilkörperdosimetrie für Photonen und Betastrahlung 15.: Hupe, Oliver, Hayo Zutz und Peter Ambrosi: Elektronische Dosimeter für gepulste Strahlung 16.: Zutz, Hayo: Messung der Strahlung im Beschleuniger-Therapieraum 17.: Hans Rabus: Strahlenwirkung 18.: Arndt, Alexander und Woon Yong Baek: Strahlenwirkung auf Biomoleküle 19.: Bug, Marion und Heidi Nettelbeck: Simulation der Strahlenwirkung auf biologische Objekte 20.: Hilgers, Gerhard: Messung der Spurstruktur ionisierender Strahlung 21.: Giesen, Ulrich: Strahlenwirkung auf zellulärer Eben