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Mastella E, Szilagyi KE, De Guglielmo E, Fabbri S, Calderoni F, Stefanelli A, Di Domenico G, Turra A. Dosimetric characterization of a mobile accelerator dedicated for intraoperative radiation therapy: Monte Carlo simulations and experimental validation. Phys Med 2022; 104:167-173. [PMID: 36463581 DOI: 10.1016/j.ejmp.2022.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/12/2022] [Accepted: 11/25/2022] [Indexed: 12/03/2022] Open
Abstract
PURPOSE This Technical Note validates previously published data about the dosimetry of the electron beams produced by a mobile accelerator dedicated for intraoperative radiation therapy (IORT). The evaluation of the directional response of a PTW microDiamond detector is presented together with a detailed analysis of the output factors (OFs) for bevelled applicators. METHODS The OFs of the 6, 8, 10 and 12 MeV electron beams produced by a light intraoperative accelerator (LIAC, SIT, Italy) were measured in a commercial water phantom using the microDiamond. A set of flat and bevelled applicators with sizes ranging from 4 to 10 cm was characterized. For bevelled applicators, a correction for the angular dependence of the microDiamond was calculated using a home-made spherical phantom. Correction factors were obtained through measurements performed rotating the accelerator treatment head at 0°, 15°, 30° and 45°. RESULTS For flat applicators, the average deviation between measured and simulated OFs was (-1.1 ± 0.7)%. The microDiamond showed a higher angular dependence for the 6 MeV beam (∼8% for angles up to 45°, range 92 % ÷ 100 %), while the variations for 8, 10 and 12 MeV beams were ∼ 4 % (range 97 % ÷ 101 %). Correcting for this dependence, the average deviation of the OFs for bevelled applicators was (-0.9 ± 1.6)%. CONCLUSIONS The presented results were in very good agreement with those reported in literature. Very similar deviations were found between flat and bevelled applicators confirming the suitability of our method to determine the angular dependence correction factors of the microDiamond detector.
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Affiliation(s)
- Edoardo Mastella
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy.
| | - Klarisa E Szilagyi
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, via Saragat 1, I-44122 Ferrara, Italy
| | - Eleonora De Guglielmo
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Sara Fabbri
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Francesca Calderoni
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Antonio Stefanelli
- Struttura Complessa di Radioterapia Oncologica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
| | - Giovanni Di Domenico
- Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, via Saragat 1, I-44122 Ferrara, Italy
| | - Alessandro Turra
- Struttura Complessa di Fisica Medica, Azienda Ospedaliero-Universitaria di Ferrara, via A. Moro 8, I-44124 Cona (Ferrara), Italy
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Kranzer R, Schüller A, Bourgouin A, Hackel T, Poppinga D, Lapp M, Looe HK, Poppe B. Response of diamond detectors in ultra-high dose-per-pulse electron beams for dosimetry at FLASH radiotherapy. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac594e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 02/28/2022] [Indexed: 11/12/2022]
Abstract
Abstract
Objective. With increasing investigation of the so-called FLASH effect, the need for accurate real time dosimetry for ultra-high dose rates is also growing. Considering the ultra-high dose-per-pulse (DPP) necessary to produce the ultra-high dose rates for investigations of the FLASH effect, real time dosimetry is a major challenge. In particular, vented ionization chambers, as used for dosimetry in conventional radiotherapy, show significant deviations from linearity with increasing DPP. This is due to recombination losses in the sensitive air volume. Solid state detectors could be an alternative. Due to their good stability of the response with regard to the accumulated dose, diamond detectors such as the microDiamond could be suitable here. The aims of this work are to investigate the response of microDiamond and adapted microDiamond prototypes in ultra-high DPP electron beams, to understand the underlying effects and to draw conclusions for further detector developments. Approach. For the study, an electron beam with a DPP up to 6.5 Gy and a pulse duration of 2.5 μs was used to fulfill the conditions under which the FLASH effect was observed. As a dose rate-independent reference, alanine dosimeters were used. Main Results. It has been shown that the commercially available microDiamond detectors have limitations in terms of linearity at ultra-high DPP. But this is not an intrinsic limitation of the detector principle. The deviations from linearity were correlated with the series resistance and the sensitivity. It could be shown that the linear range can be extended towards ultra-high DPP range by reducing the sensitivity in combination with a low series resistance of the detectors. Significance. The work shows that synthetic single crystal diamond detectors working as Schottky photodiodes are in principle suitable for FLASH-RT dosimetry at electron linear accelerators.
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Independent validation of a dedicated commissioning software and investigation of the direction dependence of the field symmetry for the LIAC intraoperative electron radiotherapy accelerator. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2021.109529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Winkler P, Odreitz-Stark S, Haas E, Thalhammer M, Partl R. Commissioning, dosimetric characterization and machine performance assessment of the LIAC HWL mobile accelerator for Intraoperative Radiotherapy. Z Med Phys 2020; 30:279-288. [PMID: 32682654 DOI: 10.1016/j.zemedi.2020.06.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 05/15/2020] [Accepted: 06/03/2020] [Indexed: 01/25/2023]
Abstract
BACKGROUND The LIAC HWL (Sordina IORT Technologies, Vicenza, Italy) is a recently designed mobile linear accelerator for intraoperative electron radiotherapy (IOeRT), producing high dose rate electron beams at four different energy levels. It features a software tool for the visualization of 2D dose distributions, which is based on Monte Carlo simulations. The aims of this work were to (i) assess the dosimetric characteristics of the accelerator, (ii) experimentally verify calculated data exported from the software and (iii) report on commissioning as well as performance of the system during the first year of operation. METHODS The electron energies of the LIAC HWL used in this study are 6, 8, 10 and 12 MeV. Diameters of the cylindrically shaped applicators range from 3 to 10cm. We studied two applicator sets with different length ratios of proximal and terminal applicator sections. Reference dosimetry, linearity as well as short- and long-term stability were measured with a PTW Advanced Markus chamber, relative depth dose and profiles were measured using an unshielded diode. Percentage-depth-dose (PDD) and transversal dose profile (TDP) data were exported from the simulation software LIACSim and compared with our measurements. RESULTS The device reaches dose rates up to 40Gy/min (for 12 MeV). Surface doses for the 10cm applicators are higher than 90%, X-ray background is below 0.6% for all energies. Simulations and measurements of PDD agreed well, with a maximum difference in the depth of the 50% isodose of 0.7mm for the flat-ended applicators and 1mm for the beveled applicators. The simulations slightly underestimate the dose in the lateral parts of the field (difference < 1.8% for flat-ended applicators). The two different applicator sets were dosimetrically equivalent. Long-term stability measurements for the first year of operation ranged from -2.1% to 1.6% (mean: -0.1%). CONCLUSIONS The system is dosimetrically well suited for IOeRT and performed stably and reliably. The software tool for visualization of dose distributions can be used to support treatment planning, following thorough validation.
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Affiliation(s)
- Peter Winkler
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Auenbrugger Platz 32, A-8036 Graz, Austria.
| | - Stefan Odreitz-Stark
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Auenbrugger Platz 32, A-8036 Graz, Austria
| | - Eva Haas
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Auenbrugger Platz 32, A-8036 Graz, Austria
| | - Martin Thalhammer
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Auenbrugger Platz 32, A-8036 Graz, Austria
| | - Richard Partl
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Auenbrugger Platz 32, A-8036 Graz, Austria
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Pérez-Calatayud J, Sanchis-Sánchez E, Collado J, González V, Pérez-Calatayud I, Pérez-Calatayud MJ, Chimeno J, Carmona V, Luis Bonet-Sancho J, García-Sánchez AJ, Sanchis E. Phantom development for daily checks in electron intraoperative radiotherapy with a mobile linac. Phys Med 2020; 76:109-116. [PMID: 32673822 DOI: 10.1016/j.ejmp.2020.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 07/03/2020] [Accepted: 07/05/2020] [Indexed: 11/29/2022] Open
Abstract
PURPOSE IORT with mobile linear accelerators is a well-established modality where the dose rate and, therefore, the dose per pulse are very high. The constancy of the dosimetric parameters of the accelerator has to be checked daily. The aim of this work is to develop a phantom with embedded detectors to improve both accuracy and efficiency in the daily test of an IORT linac at the surgery room. METHODS The developed phantom is manufactured with transparent polymethyl methacrylate (PMMA), allocating 6 parallel-plate chambers: a central one to evaluate the on-axis beam output, another on-axis one placed at a fixed depth under the previous one to evaluate the energy constancy and four off-axis chambers to evaluate the flatness and symmetry. To analyse the readings a specific application has been developed. RESULTS For all chambers and energies, the mean saturation and polarization corrections were smaller than 0.7%. The beam is monitored at different levels of the clinical beam. Output, energy constancy and flatness correlate very well with the correspondent values with the complete applicator. During the first six months of clinical use the beam dosimetric parameters showed excellent stability. CONCLUSIONS A phantom has been developed with embedded parallel plate chambers attached to the upper applicator part of an IORT linac. The phantom allows a very efficient setup reducing the time to check the parameters. It provides complete dosimetric information (output, energy and flatness) with just one shot and using ionization chambers with minimum saturation effect, as this highly pulsed beam requires.
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Affiliation(s)
- José Pérez-Calatayud
- Department of Radiation Oncology, La Fe Polytechnic and University Hospital, Valencia, Spain
| | | | - Javier Collado
- Department of Electronic Engineering, University of Valencia, Spain
| | - Vicente González
- Department of Electronic Engineering, University of Valencia, Spain
| | - I Pérez-Calatayud
- Department of Electronic Engineering, University of Valencia, Spain.
| | - M J Pérez-Calatayud
- Department of Radiation Oncology, Fundación Instituto Valenciano de Oncología, Valencia, Spain
| | - José Chimeno
- Department of Radiation Oncology, La Fe Polytechnic and University Hospital, Valencia, Spain
| | - Vicente Carmona
- Department of Radiation Oncology, La Fe Polytechnic and University Hospital, Valencia, Spain
| | | | | | - Enrique Sanchis
- Department of Electronic Engineering, University of Valencia, Spain
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Avanzo M, Dassie A, Chandra Acharya P, Chiovati P, Pirrone G, Avigo C, Barresi L, Dang Quoc S, Fiagbedzi E, Navarria F, Palazzari E, Bertola G, De Paoli A, Stancanello J, Sartor G. Electron radiotherapy (IOERT) for applications outside of the breast: Dosimetry and influence of tissue inhomogeneities. Phys Med 2020; 69:82-89. [PMID: 31841774 DOI: 10.1016/j.ejmp.2019.12.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 11/17/2019] [Accepted: 12/04/2019] [Indexed: 12/12/2022] Open
Abstract
PURPOSE The purpose of study is to investigate the dosimetry of electron intraoperative radiotherapy (IOERT) of the Intraop Mobetron 2000 mobile LINAC in treatments outside of the breast. After commissioning and external validation of dosimetry, we report in vivo results of measurements for treatments outside the breast in a large patient cohort, and investigate if the presence of inhomogeneities can affect in vivo measurements. METHODS AND MATERIALS Applicator factors and profile curves were measured with a stereotactic diode. The applicators factors of the 6 cm flat and beveled applicators were also confirmed with radiochromic films, parallel-plate ion chamber and by an external audit performed with ThermoLuminescent Dosimeters (TLDs). The influence of bone on dose was investigated by using radiochromic films attached to an insert equivalent to cortical bone, immersed in the water phantom. In vivo dosimetry was performed on 126 patients treated with IOERT using metal oxide-silicon semiconductor field effect transistors (MOSFETs) placed on the tumor bed. RESULTS Relatively small differences were found among different detectors for measurements of applicator factors. In the external audit, the agreement with the TLD was mostly within ±0.2%. The largest increase of dose due to the presence of cortical bone insert was +6.0% with energy 12 MeV and 3 cm applicator. On average, in vivo dose was significantly (+3.1%) larger than prescribed dose. CONCLUSION IOERT in applications outside the breast results in low discrepancies between in vivo and prescribed doses, which can be also explained with the presence of tissue inhomogeneity.
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Affiliation(s)
- Michele Avanzo
- Department of Medical Physics, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy.
| | - Andrea Dassie
- Department of Medical Physics, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | | | - Paola Chiovati
- Department of Medical Physics, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | - Giovanni Pirrone
- Department of Medical Physics, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | - Cinzia Avigo
- Medical Physics, ULSS 1 Dolomiti- S. Martino Hospital, Medical Physics Department, Belluno, Italy
| | - Loredana Barresi
- Department of Medical Physics, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | - Soai Dang Quoc
- Medicinal Supplies, Medical Physics Division, Hanoi Oncology Hospital, Hanoi, Vietnam
| | | | - Federico Navarria
- Radiation Oncology, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | - Elisa Palazzari
- Radiation Oncology, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | - Giulio Bertola
- Surgical Oncology, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | - Antonino De Paoli
- Radiation Oncology, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
| | | | - Giovanna Sartor
- Department of Medical Physics, Centro di Riferimento Oncologico di Aviano (CRO) IRCCS, 33081 Aviano, Italy
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