1
|
Vilches-Freixas G, Bosmans G, Douralis A, Martens J, Meijers A, Rinaldi I, Salvo K, Thomas R, Palmans H, Lourenço A. Experimental comparison of cylindrical and plane parallel ionization chambers for reference dosimetry in continuous and pulsed scanned proton beams. Phys Med Biol 2024; 69:105021. [PMID: 38640918 DOI: 10.1088/1361-6560/ad40f9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 04/19/2024] [Indexed: 04/21/2024]
Abstract
Objective. In this experimental work we compared the determination of absorbed dose to water using four ionization chambers (ICs), a PTW-34045 Advanced Markus, a PTW-34001 Roos, an IBA-PPC05 and a PTW-30012 Farmer, irradiated under the same conditions in one continuous- and in two pulsed-scanned proton beams.Approach. The ICs were positioned at 2 cm depth in a water phantom in four square-field single-energy scanned-proton beams with nominal energies between 80 and 220 MeV and in the middle of 10 × 10 × 10 cm3dose cubes centered at 10 cm or 12.5 cm depth in water. The water-equivalent thickness (WET) of the entrance window and the effective point of measurement was considered when positioning the plane parallel (PP) ICs and the cylindrical ICs, respectively. To reduce uncertainties, all ICs were calibrated at the same primary standards laboratory. We used the beam quality (kQ) correction factors for the ICs under investigation from IAEA TRS-398, the newly calculated Monte Carlo (MC) values and the anticipated IAEA TRS-398 updated recommendations.Main results. Dose differences among the four ICs ranged between 1.5% and 3.7% using both the TRS-398 and the newly recommendedkQvalues. The spread among the chambers is reduced with the newlykQvalues. The largest differences were observed between the rest of the ICs and the IBA-PPC05 IC, obtaining lower dose with the IBA-PPC05.Significance. We provide experimental data comparing different types of chambers in different proton beam qualities. The observed dose differences between the ICs appear to be related to inconsistencies in the determination of thekQvalues. For PP ICs, MC studies account for the physical thickness of the entrance window rather than the WET. The additional energy loss that the wall material invokes is not negligible for the IBA-PPC05 and might partially explain the lowkQvalues determined for this IC. To resolve this inconsistency and to benchmark MC values,kQvalues measured using calorimetry are needed.
Collapse
Affiliation(s)
- Gloria Vilches-Freixas
- Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Geert Bosmans
- Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | | | - Jonathan Martens
- Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Arturs Meijers
- Paul Scherrer Institut, Villigen, Switzerland (current address), University Medical Centre Groningen, Groningen, The Netherlands
| | - Ilaria Rinaldi
- Department of Radiation Oncology (Maastro), GROW Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, The Netherlands
| | - Koen Salvo
- UZ Leuven, Particle Therapy Interuniversity Center Leuven - PARTICLE, Leuven, Belgium
| | - Russell Thomas
- National Physical Laboratory, Teddington, United Kingdom
- University College London, London, United Kingdom
| | - Hugo Palmans
- National Physical Laboratory, Teddington, United Kingdom
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria
| | - Ana Lourenço
- National Physical Laboratory, Teddington, United Kingdom
- University College London, London, United Kingdom
| |
Collapse
|
2
|
Blum I, Wong JS, Godino Padre K, Stolzenberg J, Fuchs H, Baumann KS, Poppe B, Looe HK. Fano cavity test and investigation of the response of the Roos chamber irradiated by proton beams in perpendicular magnetic fields up to 1 T. Phys Med Biol 2024; 69:085021. [PMID: 38452383 DOI: 10.1088/1361-6560/ad311a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 03/07/2024] [Indexed: 03/09/2024]
Abstract
Objective. The aim of this work is to investigate the response of the Roos chamber (type 34001) irradiated by clinical proton beams in magnetic fields.Approach. At first, a Fano test was implemented in Monte Carlo software package GATE version 9.2 (based on Geant4 version 11.0.2) using a cylindrical slab geometry in a magnetic field up to 1 T. In accordance to an experimental setup (Fuchset al2021), the magnetic field correction factorskQB⃗of the Roos chamber were determined at different energies up to 252 MeV and magnetic field strengths up to 1 T, by separately simulating the ratios of chamber signalsMQ/MQB⃗,without and with magnetic field, and the dose-conversion factorsDw,QB⃗/Dw,Qin a small cylinder of water, with and without magnetic field. Additionally, detailed simulations were carried out to understand the observed magnetic field dependence.Main results. The Fano test was passed with deviations smaller than 0.25% between 0 and 1 T. The ratios of the chamber signals show both energy and magnetic field dependence. The maximum deviation of the dose-conversion factors from unity of 0.22% was observed at the lowest investigated proton energy of 97.4 MeV andB⃗= 1 T. The resultingkQB⃗factors increase initially with the applied magnetic field and decrease again after reaching a maximum at around 0.5 T; except for the lowest 97.4 MeV beam that show no observable magnetic field dependence. The deviation from unity of the factors is also larger for higher proton energies, where the maximum lies at 1.0035(5), 1.0054(7) and 1.0069(7) for initial energies ofE0= 152, 223.4 and 252 MeV, respectively.Significance. Detailed Monte Carlo studies showed that the observed effect can be mainly attributed to the differences in the transport of electrons produced both outside and inside of the air cavity in the presence of a magnetic field.
Collapse
Affiliation(s)
- Isabel Blum
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | - Jing Syuen Wong
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | - Krishna Godino Padre
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | - Jessica Stolzenberg
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | - Hermann Fuchs
- Division of Medical Physics, Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
| | - Kilian-Simon Baumann
- University Hospital Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
- Marburg Ion-Beam Therapy Center, Marburg, Germany
| | - Björn Poppe
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | - Hui Khee Looe
- University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| |
Collapse
|
3
|
Nagake Y, Yasui K, Ooe H, Ichihara M, Iwase K, Toshito T, Hayashi N. Investigation of ionization chamber perturbation factors using proton beam and Fano cavity test for the Monte Carlo simulation code PHITS. Radiol Phys Technol 2024; 17:280-287. [PMID: 38261133 DOI: 10.1007/s12194-024-00777-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/29/2023] [Accepted: 01/02/2024] [Indexed: 01/24/2024]
Abstract
The reference dose for clinical proton beam therapy is based on ionization chamber dosimetry. However, data on uncertainties in proton dosimetry are lacking, and multifaceted studies are required. Monte Carlo simulations are useful tools for calculating ionization chamber dosimetry in radiation fields and are sensitive to the transport algorithm parameters when particles are transported in a heterogeneous region. We aimed to evaluate the proton transport algorithm of the Particle and Heavy Ion Transport Code System (PHITS) using the Fano test. The response of the ionization chamber f Q and beam quality correction factors k Q were calculated using the same parameters as those in the Fano test and compared with those of other Monte Carlo codes for verification. The geometry of the Fano test consisted of a cylindrical gas-filled cavity sandwiched between two cylindrical walls. f Q was calculated as the ratio of the absorbed dose in water to the dose in the cavity in the chamber. We compared the f Q calculated using PHITS with that of a previous study, which was calculated using other Monte Carlo codes (Geant4, FULKA, and PENH) under similar conditions. The flight mesh, a parameter for charged particle transport, passed the Fano test within 0.15%. This was shown to be sufficiently accurate compared with that observed in previous studies. The f Q calculated using PHITS were 1.116 ± 0.002 and 1.124 ± 0.003 for NACP-02 and PTW-30013, respectively, and the k Q were 0.981 ± 0.008 and 1.027 ± 0.008, respectively, at 150 MeV. Our results indicate that PHITS can calculate the f Q and k Q with high precision.
Collapse
Affiliation(s)
- Yuya Nagake
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Keisuke Yasui
- School of Medical Sciences, Fujita Health University, Toyoake, Japan.
| | - Hiromu Ooe
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | | | - Kaito Iwase
- Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - Toshiyuki Toshito
- Nagoya Proton Therapy Center, Nagoya City University West Medical Center, Nagoya, Japan
| | - Naoki Hayashi
- School of Medical Sciences, Fujita Health University, Toyoake, Japan
| |
Collapse
|
4
|
Baumann KS, Derksen L, Witt M, Adeberg S, Zink K. The influence of different versions of FLUKA and GEANT4 on the calculation of response functions of ionization chambers in clinical proton beams. Phys Med Biol 2023; 68:24NT01. [PMID: 37939402 DOI: 10.1088/1361-6560/ad0ad4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Accepted: 11/08/2023] [Indexed: 11/10/2023]
Abstract
Objective.To investigate the influence of different versions of the Monte Carlo codesgeant4 andflukaon the calculation of overall response functionsfQof air-filled ionization chambers in clinical proton beams.Approach. fQfactors were calculated for six plane-parallel and four cylindrical ionization chambers withgeant4 andfluka. These factors were compared to already published values that were derived using older versions of these codes.Main results.Differences infQfactors calculated with different versions of the same Monte Carlo code can be up to ∼1%. Especially forgeant4, the updated version leads to a more pronounced dependence offQon proton energy and to smallerfQfactors for high energies.Significance.Different versions of the same Monte Carlo code can lead to differences in the calculation offQfactors of up to ∼1% without changing the simulation setup, transport parameters, ionization chamber geometry modeling, or employed physics lists. These findings support the statement that the dominant contributor to the overall uncertainty of Monte Carlo calculatedfQfactors are type-B uncertainties.
Collapse
Affiliation(s)
- Kilian-Simon Baumann
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
- Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
| | - Larissa Derksen
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Matthias Witt
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
- Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
| | - Sebastian Adeberg
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany
- Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
- Universitäres Centrum für Tumorerkrankungen (UCT) Frankfurt - Marburg, Germany
| | - Klemens Zink
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
- Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
| |
Collapse
|
5
|
Urago Y, Sakama M, Sakata D, Fukuda S, Katayose T, Chang W. Monte Carlo-calculated beam quality and perturbation correction factors validated against experiments for Farmer and Markus type ionization chambers in therapeutic carbon-ion beams. Phys Med Biol 2023; 68:185013. [PMID: 37579752 DOI: 10.1088/1361-6560/acf024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 08/14/2023] [Indexed: 08/16/2023]
Abstract
Objective. In current dosimetry protocols, the estimated uncertainty of the measured absorbed dose to waterDwin carbon-ion beams is approximately 3%. This large uncertainty is mainly contributed by the standard uncertainty of the beam quality correction factorkQ. In this study, thekQvalues in four cylindrical chambers and two plane-parallel chambers were calculated using Monte Carlo (MC) simulations in the plateau region. The chamber-specific perturbation correction factorPof each chamber was also determined through MC simulations.Approach.kQfor each chamber was calculated using MC code Geant4. The simulatedkQratios in subjected chambers and reference chambers were validated through comparisons against our measured values. In the measurements in Heavy-Ion Medical Accelerator in Chiba,kQratios were obtained fromDwvalues of60Co, 290- and 400 MeV u-1carbon-ion beams that were measured with the subjected ionization chamber and the reference chamber. In the simulations,fQ(the product of the water-to-air stopping power ratio andP) was acquired fromDwand the absorbed dose to air calculated in the sensitive volume of each chamber.kQvalues were then calculated from the simulatedfQand the literature-extractedWairand compared with previous publications.Main results. The calculatedkQratios in the subjected chambers to the reference chamber agreed well with the measuredkQratios. ThekQuncertainty was reduced from the current recommendation of approximately 3% to 1.7%. ThePvalues were close to unity in the cylindrical chambers and nearly 1% above unity in the plane-parallel chambers.Significance. ThekQvalues of carbon-ion beams were accurately calculated in MC simulations and thekQratios were validated through ionization chamber measurements. The results indicate a need for updating the current recommendations, which assume a constantPof unity in carbon-ion beams, to recommendations that consider chamber-induced differences.
Collapse
Affiliation(s)
- Yuka Urago
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Tokyo, Japan
- QST Hospital, National Institutes for Quantum Science and Technology, Chiba, Japan
| | - Makoto Sakama
- QST Hospital, National Institutes for Quantum Science and Technology, Chiba, Japan
| | | | - Shigekazu Fukuda
- QST Hospital, National Institutes for Quantum Science and Technology, Chiba, Japan
| | | | - Weishan Chang
- Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Tokyo, Japan
| |
Collapse
|
6
|
Baumann KS, Gomà C, Wulff J, Kretschmer J, Zink K. Monte Carlo calculated ionization chamber correction factors in clinical proton beams - deriving uncertainties from published data. Phys Med 2023; 113:102655. [PMID: 37603909 DOI: 10.1016/j.ejmp.2023.102655] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 06/16/2023] [Accepted: 08/05/2023] [Indexed: 08/23/2023] Open
Abstract
For the update of the IAEA TRS-398 Code of Practice (CoP), global ionization chamber factors (fQ) and beam quality correction factors (kQ) for air-filled ionization chambers in clinical proton beams have been calculated with different Monte Carlo codes. In this study, average Monte Carlo calculated fQ and kQ factors are provided and the uncertainty of these factors is estimated. Average fQ factors in monoenergetic proton beams with energies between 60 MeV and 250 MeV were derived from Monte Carlo calculated fQ factors published in the literature. Altogether, 195 fQ factors for six plane-parallel and three cylindrical ionization chambers calculated with penh, fluka and geant4 were incorporated. Additionally, a weighted standard deviation of fQ factors was calculated, where the same weight was assigned to each Monte Carlo code. From average fQ factors, kQ factors were derived and compared to the values from the IAEA TRS-398 CoP published in 2000 as well as to the values of the upcoming version. Average Monte Carlo calculated fQ factors are constant within 0.6% over the energy range investigated. In general, the different Monte Carlo codes agree within 1% for low energies and show larger differences up to 2% for high energies. As a result, the standard deviation of fQ factors increases with energy and is ∼0.3% for low energies and ∼0.8% for high energies. kQ factors derived from average Monte Carlo calculated fQ factors differ from the values presented in the IAEA TRS-398 CoP by up to 2.4%. The overall estimated uncertainty of Monte Carlo calculated kQ factors is ∼0.5%-1% smaller than the uncertainties estimated in IAEA TRS-398 CoP since the individual ionization chamber characteristics (e.g. fluence perturbations) are considered in detail in Monte Carlo calculations. The agreement between Monte Carlo calculated kQ factors and the values of the upcoming version of IAEA TRS-398 CoP is better with deviations smaller than 1%.
Collapse
Affiliation(s)
- Kilian-Simon Baumann
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center, Marburg, Germany.
| | - Carles Gomà
- Hospital Clínic de Barcelona, Department of Radiation Oncology, Barcelona, Spain
| | - Jörg Wulff
- West German Proton Therapy Center (WPE), Essen, Germany
| | - Jana Kretschmer
- Carl-von-Ossietzky University, University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Oldenburg, Germany; Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Klemens Zink
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center, Marburg, Germany
| |
Collapse
|
7
|
Palmans H, Lourenço A, Medin J, Vatnitsky S, Andreo P. Current best estimates of beam quality correction factors for reference dosimetry of clinical proton beams. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac9172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 09/12/2022] [Indexed: 11/12/2022]
Abstract
Abstract
Objective. To review the currently available data on beam quality correction factors,
k
Q
,
for ionization chambers in clinical proton beams and derive their current best estimates for the updated recommendations of the IAEA TRS-398 Code of Practice. Approach. The reviewed data come from 20 publications from which
k
Q
values can be derived either directly from calorimeter measurements, indirectly from comparison with other chambers or from Monte Carlo calculated overall chamber factors,
f
Q
.
For cylindrical ionization chambers, a distinction is made between data obtained in the centre of a spread-out Bragg peak and those obtained in the plateau region of single-energy fields. For the latter, the effect of depth dose gradients has to be considered. To this end an empirical model for previously published displacement correction factors for single-layer scanned beams was established, while for unmodulated scattered beams experimental data were used. From all the data, chamber factors,
f
Q
,
and chamber perturbation correction factors,
p
Q
,
were then derived and analysed. Main results. The analysis showed that except for the beam quality dependence of the water-to-air mass stopping power ratio and, for cylindrical ionization chambers in unmodulated beams, of the displacement correction factor, there is no remaining beam quality dependence of the chamber perturbation correction factors
p
Q
.
Based on this approach, average values of the beam quality independent part of the perturbation factors were derived to calculate
k
Q
values consistent with the data in the literature. Significance. The resulting data from this analysis are current best estimates of
k
Q
values for modulated scattered beams and single-layer scanned beams used in proton therapy. Based on this, a single set of harmonized values is derived to be recommended in the update of IAEA TRS-398.
Collapse
|
8
|
Vedelago J, Karger CP, Jäkel O. A review on reference dosimetry in radiation therapy with proton and light ion beams: status and impact of new developments. RADIAT MEAS 2022. [DOI: 10.1016/j.radmeas.2022.106844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
|
9
|
Medin J, Andreo P, Palmans H. Experimental determination of kQfactors for two types of ionization chambers in scanned proton beams. Phys Med Biol 2022; 67. [PMID: 35081517 DOI: 10.1088/1361-6560/ac4efa] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 01/26/2022] [Indexed: 11/12/2022]
Abstract
Objective.Experimental determination of beam qualitykQfactors for two types of Farmer ionization chambers, NE2571 and IBA FC65-G, in a scanned proton beam for three nominal energies (140 MeV, 180 MeV and 220 MeV) based on water calorimetry.Approach.Beam quality correction factors were determined comparing the results obtained with water calorimetry and ionometry. Water calorimetry was performed to determine the absorbed dose at a depth of measurement in water of 5 g cm-2, limited by the extension of the calorimeter glass vessel used. For the ionometry, two chambers of each type were included in the study. The ionization chambers were calibrated in terms of absorbed dose to water in60Co at the Swedish Secondary Standard Dosimetry Laboratory, directly traceable to the BIPM, and were used according to the IAEA TRS-398 Code of Practice.Main results. ThekQvalues determined in the present work have been compared with the values tabulated in TRS-398 and its forthcoming update and also with those obtained in previous water calorimetric measurements and Monte Carlo calculations. All results were found to agree within the combined uncertainties of the different data.Significance. It is expected that the present work will serve as an experimental contribution tokQ-factors for the two chamber types and three scanned proton beam qualities used.
Collapse
Affiliation(s)
- Joakim Medin
- Department of Hematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden.,Department of Medical Radiation Physics, Clinical Sciences, Lund, Lund University, Lund, Sweden
| | - Pedro Andreo
- Department of Medical Radiation Physics and Nuclear Medicine, Karolinska University Hospital, Stockholm, Sweden.,Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Hugo Palmans
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria.,National Physical Laboratory, Teddington, United Kingdom
| |
Collapse
|
10
|
Khan AU, Simiele EA, DeWerd LA. Monte Carlo-derived ionization chamber correction factors in therapeutic carbon ion beams. Phys Med Biol 2021; 66. [PMID: 34464949 DOI: 10.1088/1361-6560/ac226c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 08/31/2021] [Indexed: 11/12/2022]
Abstract
The accuracy of electromagnetic transport in the GEANT4 Monte Carlo (MC) code was investigated for carbon ion beams and ionization chamber (IC)-specific beam quality correction factors were calculated. This work implemented a Fano cavity test for carbon ion beams in the 100-450 MeV/u energy range to assess the accuracy of the default electromagnetic physics parameters. TheUrbanand theWentzel-VImultiple Coulomb scattering models were evaluated and the impact ofmaxStep,dRover,andfinal rangeparameters on the accuracy of the transport algorithm was investigated. The optimal production thresholds for an accurate calculation offQvalues, which is the product of the water-to-air stopping power ratio and the IC-specific perturbation correction factor, were also studied. ThefQcorrection factors were calculated for a cylindrical and a parallel-plate IC using carbon ions in the 150-450 MeV/u energy range. Modifying the default electromagnetic physics parameters resulted in a maximum deviation from theory of 0.3%. Therefore, the default EM parameters were used for the remainder of this work. ThefQfactors were found to converge for both ICs with decreasing production threshold distance below 5μm. ThefQvalues obtained in this work agreed with the TRS-398 stopping power ratios and other previously reported results within uncertainty. This study highlights an accurate MC-based technique to calculate the combined stopping power ratio and the perturbation correction factor for any IC in carbon ion beams.
Collapse
Affiliation(s)
- Ahtesham Ullah Khan
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, United States of America
| | - Eric A Simiele
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305, United States of America
| | - Larry A DeWerd
- Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, United States of America
| |
Collapse
|
11
|
Baumann KS, Derksen L, Witt M, Michael Burg J, Engenhart-Cabillic R, Zink K. Monte Carlo calculation of beam quality correction factors in proton beams using FLUKA. Phys Med Biol 2021; 66. [PMID: 34378546 DOI: 10.1088/1361-6560/ac1c4b] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 08/10/2021] [Indexed: 11/12/2022]
Abstract
Purpose.To provide Monte Carlo calculated beam quality correction factors (kQ) for monoenergetic proton beams using the Monte Carlo codefluka.Materials and methods.The Monte Carlo codeflukawas used to calculate the dose absorbed in a water-filled reference volume and the air-filled cavities of six plane-parallel and four cylindrical ionization chambers. The chambers were positioned at the entrance region of monoenergetic proton beams with energies between 60 and 250 MeV. Based on these dose values,fQas well askQfactors were calculated whilefQ0factors were taken from Andreoet al(2020Phys. Med. Biol.65095011).Results. kQfactors calculated in this work were found to agree with experimentally determinedkQfactors on the 1%-level, with only two exceptions with deviations of 1.4% and 1.9%. The comparison offQfactors calculated usingflukawithfQfactors calculated using the Monte Carlo codesgeant4 andpenhshowed a general good agreement for low energies, while differences for higher energies were pronounced. For high energies, in most cases the Monte Carlo codesflukaandgeant4 lead to comparable results while thefQfactors calculated withpenhare larger.Conclusion.flukacan be used to calculatekQfactors in clinical proton beams. The divergence of Monte Carlo calculatedkQfactors for high energies suggests that the role of nuclear interaction models implemented in the different Monte Carlo codes needs to be investigated in more detail.
Collapse
Affiliation(s)
- Kilian-Simon Baumann
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany.,University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany.,Marburg Ion-Beam Therapy Center, Marburg, Germany
| | - Larissa Derksen
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Matthias Witt
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany.,Marburg Ion-Beam Therapy Center, Marburg, Germany
| | - Jan Michael Burg
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany.,University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Rita Engenhart-Cabillic
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany.,Marburg Ion-Beam Therapy Center, Marburg, Germany
| | - Klemens Zink
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany.,University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany.,Marburg Ion-Beam Therapy Center, Marburg, Germany
| |
Collapse
|
12
|
Gomà C. Comment on 'Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry'. Phys Med Biol 2021; 66. [PMID: 34341186 DOI: 10.1088/1361-6560/ac16bb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 07/21/2021] [Indexed: 11/12/2022]
Abstract
Kuesset al(2017Phys. Med. Biol.62206-27) irradiated several PTW 34070 ionization chambers with a narrow x-ray beam impinging at different positions of the detector entrance window and they observed that the reading of the ionization chambers decreased as the impact point of the beam approached the edge of the sensitive volume. They concluded that the radial response of the detector decreased with increasing radius and they proposed a correction factor to correct for that effect. This work shows, by means of a simple Monte Carlo simulation, that the conclusions of Kuess and co-workers do not seem to be supported by their experimental findings-quite the opposite, their experimental results seem to be compatible with a rather homogeneous radial response of the PTW 34070. It is shown that the radial decrease in the ionization chamber reading (as the impact point of the beam approaches the edge of the sensitive volume) is not due to a radial decrease of the response, but to the fact that part of the energy transferred to the secondary electrons is carried away and deposited outside the sensitive volume of the ionization chamber. As a consequence, it is believed that the method and correction factors proposed by Kuess and colleagues are not suitable to assess the response uniformity of large-area ionization chambers. Furthermore, the results of the publications that have used them thus far should be thoroughly revised.
Collapse
Affiliation(s)
- Carles Gomà
- Department of Radiation Oncology, Hospital Clínic de Barcelona, Barcelona, Spain
| |
Collapse
|
13
|
Zou W, Diffenderfer ES, Ota K, Boisseau P, Kim MM, Cai Y, Avery SM, Carlson DJ, Wiersma RD, Lin A, Koumenis C, Cengel KA, Metz JM, Dong L, Teo BK. Characterization of a high-resolution 2D transmission ion chamber for independent validation of proton pencil beam scanning of conventional and FLASH dose delivery. Med Phys 2021; 48:3948-3957. [PMID: 33843065 DOI: 10.1002/mp.14882] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 02/17/2021] [Accepted: 03/25/2021] [Indexed: 12/16/2022] Open
Abstract
INTRODUCTION Ultra-high dose rate (FLASH) radiotherapy has become a popular research topic with the potential to reduce normal tissue toxicities without losing the benefit of tumor control. The development of FLASH proton pencil beam scanning (PBS) delivery requires accurate dosimetry despite high beam currents with correspondingly high ionization densities in the monitoring chamber. In this study, we characterized a newly designed high-resolution position sensing transmission ionization chamber with a purpose-built multichannel electrometer for both conventional and FLASH dose rate proton radiotherapy. METHODS The dosimetry and positioning accuracies of the ion chamber were fully characterized with a clinical scanning beam. On the FLASH proton beamline, the cyclotron output current reached up to 350 nA with a maximum energy of 226.2 MeV, with 210 ± 3 nA nozzle pencil beam current. The ion recombination effect was characterized under various bias voltages up to 1000 V and different beam intensities. The charge collected by the transmission ion chamber was compared with the measurements from a Faraday cup. RESULTS Cross-calibrated with an Advanced Markus chamber (PTW, Freiburg, Germany) in a uniform PBS proton beam field at clinical beam setting, the ion chamber calibration was 38.0 and 36.7 GyE·mm2 /nC at 100 and 226.2 MeV, respectively. The ion recombination effect increased with larger cyclotron current at lower bias voltage while remaining ≤0.5 ± 0.5% with ≥200 V of bias voltage. Above 200 V, the normalized ion chamber readings demonstrated good linearity with the mass stopping power in air for both clinical and FLASH beam intensities. The spot positioning accuracy was measured to be 0.10 ± 0.08 mm in two orthogonal directions. CONCLUSION We characterized a transmission ion chamber system under both conventional and FLASH beam current densities and demonstrated its suitability for use as a proton pencil beam dose and spot position delivery monitor under FLASH dose rate conditions.
Collapse
Affiliation(s)
- Wei Zou
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Eric S Diffenderfer
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Kan Ota
- Pyramid Technical Consultants, Inc, Boston, MA, 02421, USA
| | - Paul Boisseau
- Pyramid Technical Consultants, Inc, Boston, MA, 02421, USA
| | - Michele M Kim
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | | | - Stephen M Avery
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - David J Carlson
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Rodney D Wiersma
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Alexander Lin
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Constantinos Koumenis
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Keith A Cengel
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - James M Metz
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Lei Dong
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Boonkeng K Teo
- Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, 19104, USA
| |
Collapse
|
14
|
Sempau J, Kazantsev P, Izewska J, Brualla L. Monte Carlo verification of the holder correction factors for the radiophotoluminescent glass dosimeter used by the IAEA in international dosimetry audits. Phys Med 2021; 86:1-5. [PMID: 34044284 DOI: 10.1016/j.ejmp.2021.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 04/08/2021] [Accepted: 04/14/2021] [Indexed: 11/29/2022] Open
Abstract
The International Atomic Energy Agency (IAEA), jointly with the World Health Organization (WHO), has operated a postal dosimetry audit program for radiotherapy centers worldwide since 1969. In 2017 the IAEA introduced a new methodology based on radiophotoluminescent dosimetry (RPLD) for these audits. The detection system consists of a phosphate glass dosimeter inserted in a plastic capsule that is kept in measuring position with a PMMA holder during irradiation. Correction factors for this holder were obtained using experimental methods. In this work these methods are described and the resulting factors are verified by means of Monte Carlo simulation with the general-purpose code PENELOPE for a range of photon beam qualities relevant in radiotherapy. The study relies on a detailed geometrical representation of the experimental setup. Various photon beams were obtained from faithful modeling of the corresponding linacs. Monte Carlo simulation transport parameters are selected to ensure subpercent accuracy. The simulated correction factors fall in the interval 1.005-1.008 (±0.2%), with deviations with respect to experimental values not larger than 0.2(2)%. This study corroborates the validity of the holder correction factors currently used for the IAEA audits.
Collapse
Affiliation(s)
- J Sempau
- Universitat Politècnica de Catalunya, E-08028 Barcelona, Spain; Centros de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), E-28029 Madrid, Spain
| | - P Kazantsev
- International Atomic Energy Agency, A-1400 Vienna, Austria
| | - J Izewska
- International Atomic Energy Agency, A-1400 Vienna, Austria
| | - L Brualla
- West German Proton Therapy Centre WPE, D-45147 Essen, Germany; University of Duisburg-Essen, Faculty of Medicine, D-45147 Essen, Germany; University Hospital Essen, West German Cancer Center WTZ, D-45147 Essen, Germany.
| |
Collapse
|
15
|
Baumann KS, Kaupa S, Bach C, Engenhart-Cabillic R, Zink K. Monte Carlo calculation of perturbation correction factors for air-filled ionization chambers in clinical proton beams using TOPAS/GEANT. Z Med Phys 2021; 31:175-191. [PMID: 33775521 DOI: 10.1016/j.zemedi.2020.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 08/20/2020] [Accepted: 08/31/2020] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Current dosimetry protocols for clinical protons using air-filled ionization chambers assume that the perturbation correction factor is equal to unity for all ionization chambers and proton energies. Since previous Monte Carlo based studies suggest that perturbation correction factors might be significantly different from unity this study aims to determine perturbation correction factors for six plane-parallel and four cylindrical ionization chambers in proton beams at clinical energies. MATERIALS AND METHODS The dose deposited in the air cavity of the ionization chambers was calculated with the help of the Monte Carlo code TOPAS/Geant4 while specific constructive details of the chambers were removed step by step. By comparing these dose values the individual perturbation correction factors pcel, pstem, psleeve, pwall, pcav⋅pdis as well as the total perturbation correction factor pQ were derived for typical clinical proton energies between 80 and 250MeV. RESULTS The total perturbation correction factor pQ was smaller than unity for almost every ionization chamber and proton energy and in some cases significantly different from unity (deviation larger than 1%). The maximum deviation from unity was 2.0% for cylindrical and 1.5% for plane-parallel ionization chambers. Especially the factor pwall was found to differ significantly from unity. It was shown that this is due to the fact that secondary particles, especially alpha particles and fragments, are scattered from the chamber wall into the air cavity resulting in an overresponse of the chamber. CONCLUSION Perturbation correction factors for ionization chambers in proton beams were calculated using Monte Carlo simulations. In contrast to the assumption of current dosimetry protocols the total perturbation correction factor pQ can be significantly different from unity. Hence, beam quality correction factors [Formula: see text] that are calculated with the help of perturbation correction factors that are assumed to be unity come with a corresponding additional uncertainty.
Collapse
Affiliation(s)
- Kilian-Simon Baumann
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany.
| | - Sina Kaupa
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Constantin Bach
- University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany
| | - Rita Engenhart-Cabillic
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany
| | - Klemens Zink
- University Medical Center Giessen-Marburg, Department of Radiotherapy and Radiooncology, Marburg, Germany; University of Applied Sciences, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Marburg Ion-Beam Therapy Center (MIT), Marburg, Germany; Frankfurt Institute of Advanced Studies - FIAS, Frankfurt, Germany
| |
Collapse
|
16
|
Carlino A, Palmans H, Gouldstone C, Trnkova P, Noerrevang O, Vestergaard A, Freixas GV, Bosmans G, Lorentini S, Schwarz M, Koska B, Wulff J, Vatnitsky S, Stock M. Results of an independent dosimetry audit for scanned proton beam therapy facilities. Z Med Phys 2021; 31:145-153. [PMID: 33712295 DOI: 10.1016/j.zemedi.2021.01.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 12/13/2020] [Accepted: 01/25/2021] [Indexed: 10/22/2022]
Abstract
PURPOSE An independent dosimetry audit based on end-to-end testing of the entire chain of radiation therapy delivery is highly recommended to ensure consistent treatments among proton therapy centers. This study presents an auditing methodology developed by the MedAustron Ion Beam Therapy Center (Austria) in collaboration with the National Physical Laboratory (UK) and audit results for five scanned proton beam therapy facilities in Europe. METHODS The audit procedure used a homogeneous and an anthropomorphic head phantom. The phantoms were loaded either with an ionization chamber or with alanine pellets and radiochromic films. Homogeneously planned doses of 10Gy were delivered to a box-like target volume in the homogeneous phantom and to two clinical scenarios with increasing complexity in the head phantom. RESULTS For all tests the mean of the local differences of the absolute dose to water determined with the alanine pellets compared to the predicted dose from the treatment planning system installed at the audited institution was determined. The mean value taken over all tests performed was -0.1±1.0%. The measurements carried out with the ionization chamber were consistent with the dose determined by the alanine pellets with a mean deviation of -0.5±0.6%. CONCLUSION The developed dosimetry audit method was successfully applied at five proton centers including various "turn-key" Cyclotron solutions by IBA, Varian and Mevion. This independent audit with extension to other tumour sites and use of the correspondent anthropomorphic phantoms may be proposed as part of a credentialing procedure for future clinical trials in proton beam therapy.
Collapse
Affiliation(s)
- Antonio Carlino
- MedAustron Ion Therapy Center, Medical Physics, Wiener Neustadt, Austria.
| | - Hugo Palmans
- MedAustron Ion Therapy Center, Medical Physics, Wiener Neustadt, Austria; National Physical Laboratory, Teddington, United Kingdom
| | | | - Petra Trnkova
- HollandPTC, Huismansingel 4, Delft, The Netherlands; Erasmus MC, Department of Radiation Oncology, Rotterdam, The Netherlands
| | - Ole Noerrevang
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Anne Vestergaard
- Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Gloria Vilches Freixas
- Maastro Proton Therapy, Department of Radiation Oncology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Geert Bosmans
- Maastro Proton Therapy, Department of Radiation Oncology, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Stefano Lorentini
- Centro di Protonterapia, APSS, Via al Desert 14, 38122 Trento, Italy
| | - Marco Schwarz
- Centro di Protonterapia, APSS, Via al Desert 14, 38122 Trento, Italy; TIFPA-INFN, Trento, Italy
| | - Benjamin Koska
- West German Proton Therapy Centre Essen, Hufelandstr. 55, Essen, Germany; University Hospital Essen, Hufelandstr. 55, Essen, Germany
| | - Jörg Wulff
- West German Proton Therapy Centre Essen, Hufelandstr. 55, Essen, Germany; University Hospital Essen, Hufelandstr. 55, Essen, Germany
| | | | - Markus Stock
- MedAustron Ion Therapy Center, Medical Physics, Wiener Neustadt, Austria
| |
Collapse
|
17
|
Verbeek N, Wulff J, Bäumer C, Smyczek S, Timmermann B, Brualla L. Single pencil beam benchmark of a module for Monte Carlo simulation of proton transport in the PENELOPE code. Med Phys 2020; 48:456-476. [PMID: 33217026 DOI: 10.1002/mp.14598] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND AND PURPOSE PENH is a recently coded module for simulation of proton transport in conjunction with the Monte Carlo code PENELOPE. PENELOPE applies class II simulation to all type of interactions, in particular, to elastic collisions. PENH uses calculated differential cross sections for proton elastic collisions that include electron screening effects as well as nuclear structure effects. Proton-induced nuclear reactions are simulated from information in the ENDF-6 database or from alternative nuclear databases in ENDF format. The purpose of this work is to benchmark this module by simulating absorbed dose distributions from a single finite spot size proton pencil beam in water. MATERIALS AND METHODS Monte Carlo simulations with PENH are compared with simulation results from TOPAS Monte Carlo (v3.1p2) and RayStation Monte Carlo (v6). Different beam models are examined in terms of mean energy and energy spread to match the measured profiles. The phase-space file is derived from experimental measurements. Simulated absorbed dose distributions are compared to experimental data obtained with the ionization chamber array MatriXX 2D detector (IBA Dosimetry) in a water tank. The experiments were conducted with a clinical IBA pencil beam scanning dedicated nozzle. In all simulations a Fermi-Eyges phase-space representation of a single finite spot size proton pencil beam is used. RESULTS In general, there is a good agreement between simulated results and experimental data up to a distance of 3 cm from the central axis. In the core region (region where the dose is more than 10% of the maximum dose) PENH shows, overall, the smallest deviations from experimental data, with the largest radial rms (root mean square) smaller than 0.2. The results achieved by TOPAS and RayStation in that region are very close to those of PENH. For the halo region, that is the area of the dose distribution outside the core region reaching down to 0.01% of the maximum intensity, the largest rms achieved by TOPAS is always smaller than 0.5, yielding better results than the rest of the codes. CONCLUSION The physics modeling of the PENELOPE/PENH code yields results consistent with measurements in the dose range relevant for proton therapy. The discrepancies between PENH appearing at distances larger than 3 cm from the central-beam axis are accountable to the lack of neutron simulation in this code. In contradistinction, TOPAS has a better agreement with experimental data at large distances from the central-beam axis because of the simulation of neutrons.
Collapse
Affiliation(s)
- Nico Verbeek
- West German Proton Therapy Centre Essen WPE, Essen, Germany.,Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.,University Hospital Essen, West German Cancer Center WTZ, Essen, Germany
| | - Jörg Wulff
- West German Proton Therapy Centre Essen WPE, Essen, Germany.,University Hospital Essen, West German Cancer Center WTZ, Essen, Germany
| | - Christian Bäumer
- West German Proton Therapy Centre Essen WPE, Essen, Germany.,University Hospital Essen, West German Cancer Center WTZ, Essen, Germany.,Radiation Oncology and Imaging, German Cancer Consortium DKTK, Heidelberg, Germany.,Technische Universität Dortmund, Otto-Hahn-Str. 4a, Dortmund, 44227, Germany
| | - Sabrina Smyczek
- West German Proton Therapy Centre Essen WPE, Essen, Germany.,University Hospital Essen, West German Cancer Center WTZ, Essen, Germany.,Faculty of Physics, Heinrich Heine University Düsseldorf HHU, Düsseldorf, Germany
| | - Beate Timmermann
- West German Proton Therapy Centre Essen WPE, Essen, Germany.,Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.,University Hospital Essen, West German Cancer Center WTZ, Essen, Germany.,Radiation Oncology and Imaging, German Cancer Consortium DKTK, Heidelberg, Germany.,Department of Particle Therapy, University Hospital Essen, Essen, Germany
| | - Lorenzo Brualla
- West German Proton Therapy Centre Essen WPE, Essen, Germany.,Faculty of Medicine, University of Duisburg-Essen, Essen, Germany.,University Hospital Essen, West German Cancer Center WTZ, Essen, Germany
| |
Collapse
|
18
|
Palmans H, Medin J, Trnková P, Vatnitsky S. Gradient corrections for reference dosimetry using Farmer-type ionization chambers in single-layer scanned proton fields. Med Phys 2020; 47:6531-6539. [PMID: 33111370 DOI: 10.1002/mp.14554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/17/2020] [Accepted: 10/16/2020] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The local depth dose gradient and the displacement correction factor for Farmer-type ionization chambers are quantified for reference dosimetry at shallow depth in single-layer scanned proton fields. METHOD Integrated radial profiles as a function of depth (IRPDs) measured at three proton therapy centers were smoothed by polynomial fits. The local relative depth dose gradient at measurement depths from 1 to 5 cm were derived from the derivatives of those fits. To calculate displacement correction factors, the best estimate of the effective point of measurement was derived from reviewing experimental and theoretical determinations reported in the literature. Displacement correction factors for the use of Farmer-type ionization chambers with their reference point (at the center of the cavity volume) positioned at the measurement depth were derived as a ratio of IRPD values at the measurement depth and at the effective point of measurement. RESULTS Depth dose gradients are as low as 0.1-0.4% per mm at measurement depths from 1 to 5 cm in the highest clinical proton energies (with residual ranges higher than 15 cm) and increase to 1% per mm at a residual range of 4 cm and become larger than 3% per mm for residual ranges lower than 2 cm. The literature review shows that the effective point of measurement of Farmer-type ionization chambers is, similarly as for carbon ion beams, located 0.75 times the cavity radius closer to the beam origin as the center of the cavity. If a maximum displacement correction of 2% is deemed acceptable to be included in calculated beam quality correction factors, Farmer-type ICs can be used at measurements depths from 1 to 5 cm for which the residual range is 4 cm or larger. If one wants to use the same beam quality correction factors as applicable to the conventional measurement point for scattered beams, located at the center of the SOBP, the relative standard uncertainty on the assumption that the displacement correction factor is unity can be kept below 0.5% for measurement depths of at least 2 cm and for residual ranges of 15 cm or higher. CONCLUSION The literature review confirmed that for proton beams the effective point of measurement of Farmer-type ionization chambers is located 0.75 times the cavity radius closer to the beam origin as the center of the cavity. Based on the findings in this work, three options can be recommended for reference dosimetry of scanned proton beams using Farmer-type ionization chambers: (a) positioning the effective point of measurement at the measurement depth, (b) positioning the reference point at the measurement depth and applying a displacement correction factor, and (c) positioning the reference point at the measurement depth without applying a displacement correction factor. Based on limiting the acceptable uncertainty on the gradient correction factor to 0.5% and the maximum deviation of the displacement perturbation correction factor from unity to 2%, the first two options can be allowed for residual ranges of at least 4 cm while the third option only for residual ranges of at least 15 cm.
Collapse
Affiliation(s)
- Hugo Palmans
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria.,National Physical Laboratory, Teddington, United Kingdom of Great Britain and Northern Ireland
| | | | - Petra Trnková
- HollandPTC, Delft, The Netherlands.,Erasmus Medical Centre, Rotterdam, The Netherlands
| | | |
Collapse
|
19
|
Kretschmer J, Dulkys A, Brodbek L, Stelljes TS, Looe HK, Poppe B. Monte Carlo simulated beam quality and perturbation correction factors for ionization chambers in monoenergetic proton beams. Med Phys 2020; 47:5890-5905. [DOI: 10.1002/mp.14499] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 08/19/2020] [Accepted: 09/08/2020] [Indexed: 11/11/2022] Open
Affiliation(s)
- Jana Kretschmer
- University Clinic for Medical Radiation Physics Medical Campus Pius HospitalCarl‐von‐Ossietzky University Oldenburg Germany
| | - Anna Dulkys
- University Clinic for Medical Radiation Physics Medical Campus Pius HospitalCarl‐von‐Ossietzky University Oldenburg Germany
- Department of Radiation Therapy Helios Clinics Schwerin Schwerin Germany
| | - Leonie Brodbek
- University Clinic for Medical Radiation Physics Medical Campus Pius HospitalCarl‐von‐Ossietzky University Oldenburg Germany
- Department of Radiation Oncology University Medical Center GroningenUniversity of Groningen Groningen The Netherlands
| | - Tenzin Sonam Stelljes
- University Clinic for Medical Radiation Physics Medical Campus Pius HospitalCarl‐von‐Ossietzky University Oldenburg Germany
| | - Hui Khee Looe
- University Clinic for Medical Radiation Physics Medical Campus Pius HospitalCarl‐von‐Ossietzky University Oldenburg Germany
| | - Björn Poppe
- University Clinic for Medical Radiation Physics Medical Campus Pius HospitalCarl‐von‐Ossietzky University Oldenburg Germany
| |
Collapse
|
20
|
Shang C, Evans G, Rahman M, Lin L. Beam characteristics of the first clinical 360° rotational single gantry room scanning pencil beam proton treatment system and comparisons against a multi‐room system. J Appl Clin Med Phys 2020; 21:266-271. [PMID: 32790244 PMCID: PMC7497910 DOI: 10.1002/acm2.12984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 06/21/2020] [Accepted: 06/23/2020] [Indexed: 11/07/2022] Open
Affiliation(s)
- Charles Shang
- South Florida Proton Therapy Institute Delray Beach FL USA
| | - Grant Evans
- South Florida Proton Therapy Institute Delray Beach FL USA
| | | | - Liyong Lin
- Emory Proton Therapy Center Atlanta GA USA
| |
Collapse
|
21
|
Baumann KS, Kaupa S, Bach C, Engenhart-Cabillic R, Zink K. Corrigendum: Monte Carlo calculation of beam quality correction factors in proton beams using TOPAS/GEANT4 (2020 Phys. Med. Biol. 65 055015). Phys Med Biol 2020. [DOI: 10.1088/1361-6560/ab8fc2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
22
|
Tikkanen J, Zink K, Pimpinella M, Teles P, Borbinha J, Ojala J, Siiskonen T, Gomà C, Pinto M. Calculated beam quality correction factors for ionization chambers in MV photon beams. Phys Med Biol 2020; 65:075003. [PMID: 31995531 DOI: 10.1088/1361-6560/ab7107] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The beam quality correction factor, [Formula: see text], which corrects for the difference in the ionization chamber response between the reference and clinical beam quality, is an integral part of radiation therapy dosimetry. The uncertainty of [Formula: see text] is one of the most significant sources of uncertainty in the dose determination. To improve the accuracy of available [Formula: see text] data, four partners calculated [Formula: see text] factors for 10 ionization chamber models in linear accelerator beams with accelerator voltages ranging from 6 MV to 25 MV, including flattening-filter-free (FFF) beams. The software used in the calculations were EGSnrc and PENELOPE, and the ICRU report 90 cross section data for water and graphite were included in the simulations. Volume averaging correction factors were calculated to correct for the dose averaging in the chamber cavities. A comparison calculation between partners showed a good agreement, as did comparison with literature. The [Formula: see text] values from TRS-398 were higher than our values for each chamber where data was available. The [Formula: see text] values for the FFF beams did not follow the same [Formula: see text], [Formula: see text] relation as beams with flattening filter (values for 10 MV FFF beams were below fits made to other data on average by 0.3%), although our FFF sources were only for Varian linacs.
Collapse
Affiliation(s)
- J Tikkanen
- Radiation and Nuclear Safety Authority (STUK), Helsinki, Finland. Helsinki Institute of Physics, University of Helsinki, Helsinki, Finland
| | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Baumann KS, Kaupa S, Bach C, Engenhart-Cabillic R, Zink K. Monte Carlo calculation of beam quality correction factors in proton beams using TOPAS/GEANT4. ACTA ACUST UNITED AC 2020; 65:055015. [DOI: 10.1088/1361-6560/ab6e53] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
24
|
Elia A, Resch AF, Carlino A, Böhlen TT, Fuchs H, Palmans H, Letellier V, Dreindl R, Osorio J, Stock M, Sarrut D, Grevillot L. A GATE/Geant4 beam model for the MedAustron non-isocentric proton treatment plans quality assurance. Phys Med 2020; 71:115-123. [DOI: 10.1016/j.ejmp.2020.02.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 12/23/2019] [Accepted: 02/07/2020] [Indexed: 10/24/2022] Open
|
25
|
Patera V, Sarti A. Recent Advances in Detector Technologies for Particle Therapy Beam Monitoring and Dosimetry. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020. [DOI: 10.1109/trpms.2019.2951848] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
26
|
Burigo LN, Greilich S. Impact of new ICRU 90 key data on stopping-power ratios and beam quality correction factors for carbon ion beams. ACTA ACUST UNITED AC 2019; 64:195005. [DOI: 10.1088/1361-6560/ab376e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
27
|
Gomà C, Sterpin E. Monte Carlo calculation of beam quality correction factors in proton beams using PENH. ACTA ACUST UNITED AC 2019; 64:185009. [DOI: 10.1088/1361-6560/ab3b94] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
28
|
Baumann KS, Horst F, Zink K, Gomà C. Comparison of penh, fluka, and Geant4/topas for absorbed dose calculations in air cavities representing ionization chambers in high-energy photon and proton beams. Med Phys 2019; 46:4639-4653. [PMID: 31350915 PMCID: PMC6851981 DOI: 10.1002/mp.13737] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 07/01/2019] [Accepted: 07/16/2019] [Indexed: 12/16/2022] Open
Abstract
Purpose The purpose of this work is to analyze whether the Monte Carlo codes penh, fluka, and geant4/topas are suitable to calculate absorbed doses and fQ/fQ0 ratios in therapeutic high‐energy photon and proton beams. Methods We used penh, fluka, geant4/topas, and egsnrc to calculate the absorbed dose to water in a reference water cavity and the absorbed dose to air in two air cavities representative of a plane‐parallel and a cylindrical ionization chamber in a 1.25 MeV photon beam and a 150 MeV proton beam — egsnrc was only used for the photon beam calculations. The physics and transport settings in each code were adjusted to simulate the particle transport as detailed as reasonably possible. From these absorbed doses, fQ0 factors, fQ factors, and fQ/fQ0 ratios (which are the basis of Monte Carlo calculated beam quality correction factors kQ,Q0) were calculated and compared between the codes. Additionally, we calculated the spectra of primary particles and secondary electrons in the reference water cavity, as well as the integrated depth–dose curve of 150 MeV protons in water. Results The absorbed doses agreed within 1.4% or better between the individual codes for both the photon and proton simulations. The fQ0 and fQ factors agreed within 0.5% or better for the individual codes for both beam qualities. The resulting fQ/fQ0 ratios for 150 MeV protons agreed within 0.7% or better. For the 1.25 MeV photon beam, the spectra of photons and secondary electrons agreed almost perfectly. For the 150 MeV proton simulation, we observed differences in the spectra of secondary protons whereas the spectra of primary protons and low‐energy delta electrons also agreed almost perfectly. The first 2 mm of the entrance channel of the 150 MeV proton Bragg curve agreed almost perfectly while for greater depths, the differences in the integrated dose were up to 1.5%. Conclusion penh, fluka, and geant4/topas are capable of calculating beam quality correction factors in proton beams. The differences in the fQ0 and fQ factors between the codes are 0.5% at maximum. The differences in the fQ/fQ0 ratios are 0.7% at maximum.
Collapse
Affiliation(s)
- Kilian-Simon Baumann
- Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg, Germany.,Institute of Medical Physics and Radiation Protection, University of Applied Sciences, Giessen, Germany
| | - Felix Horst
- Institute of Medical Physics and Radiation Protection, University of Applied Sciences, Giessen, Germany.,GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
| | - Klemens Zink
- Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg, Germany.,Institute of Medical Physics and Radiation Protection, University of Applied Sciences, Giessen, Germany.,Frankfurt Institute for Advanced Studies (FIAS), Frankfurt, Germany
| | - Carles Gomà
- Department of Oncology, Laboratory of Experimental Radiotherapy, KU Leuven, Leuven, Belgium
| |
Collapse
|
29
|
Wulff J, Baumann KS, Verbeek N, Bäumer C, Timmermann B, Zink K. Corrigendum: TOPAS/Geant4 configuration for ionization chamber calculations in proton beams (2018 Phys. Med. Biol. 63 115013). Phys Med Biol 2019. [DOI: 10.1088/1361-6560/ab0292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
30
|
Lourenço A, Bouchard H, Galer S, Royle G, Palmans H. The influence of nuclear interactions on ionization chamber perturbation factors in proton beams: FLUKA simulations supported by a Fano test. Med Phys 2018; 46:885-891. [DOI: 10.1002/mp.13281] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 10/16/2018] [Accepted: 10/21/2018] [Indexed: 11/05/2022] Open
Affiliation(s)
- Ana Lourenço
- Medical Radiation Science National Physical Laboratory Teddington TW11 0LW UK
- Department of Medical Physics and Biomedical Engineering University College London London WC1E 6BT UK
| | - Hugo Bouchard
- Département de Physique Université de Montréal, Québec 2900 Boulevard Edouard‐Montpetit Montréal QC H3T 1J4 Canada
| | - Sebastian Galer
- Medical Radiation Science National Physical Laboratory Teddington TW11 0LW UK
| | - Gary Royle
- Department of Medical Physics and Biomedical Engineering University College London London WC1E 6BT UK
| | - Hugo Palmans
- Medical Radiation Science National Physical Laboratory Teddington TW11 0LW UK
- Medical Physics Group EBG MedAustron GmbH A‐2700 Wiener Neustadt Austria
| |
Collapse
|
31
|
43 Reference dosimetry for high dose rate pulsed scanned proton beams. Phys Med 2018. [DOI: 10.1016/j.ejmp.2018.09.056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
32
|
Carlino A, Stock M, Zagler N, Marrale M, Osorio J, Vatnitsky S, Palmans H. Characterization of PTW-31015 PinPoint ionization chambers in photon and proton beams. ACTA ACUST UNITED AC 2018; 63:185020. [DOI: 10.1088/1361-6560/aadd39] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
33
|
Winterhalter C, Fura E, Tian Y, Aitkenhead A, Bolsi A, Dieterle M, Fredh A, Meier G, Oxley D, Siewert D, Weber DC, Lomax A, Safai S. Validating a Monte Carlo approach to absolute dose quality assurance for proton pencil beam scanning. ACTA ACUST UNITED AC 2018; 63:175001. [DOI: 10.1088/1361-6560/aad3ae] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
34
|
Czarnecki D, Poppe B, Zink K. Impact of new ICRU Report 90 recommendations on calculated correction factors for reference dosimetry. Phys Med Biol 2018; 63:155015. [PMID: 29974869 DOI: 10.1088/1361-6560/aad148] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In 2016 the ICRU published a new report dealing with key data for ionizing radiation dosimetry (ICRU Report 90). New recommendations have been made for the mean excitation energies I for air, graphite and liquid water as well as for the graphite density to use when evaluating the density effect. In addition, the ICRU Report 90 discusses renormalized photoelectric cross sections, but refuses to give a recommendation on the use of renormalization factors. However, the Consultative Committee for Ionizing Radiation recommends to use renormalized photoeffect cross sections. Goal of the present work is to evaluate the impact of these new recommendations on clinical reference dosimetry for high energy photon and electron beams. The beam quality correction factor k Q was calculated by Monte Carlo simulations for compact and parallel plate ionization chambers. In case of photons seven phase space files from clinical accelerators and twelve spectra taken from literature from 4 MV to 24 MV and additionally a 60Co source were applied. As electron source thirteen electron spectra available in literature were used in the range of 4 MeV-21 MeV. The new ICRU recommendations have a small impact on Monte Carlo calculated k Q values for the chosen ionization chambers in the range of 0.1%-0.35% only-the difference increases for higher photon energies. The impact of the ICRU Report 90 recommendations on Monte Carlo calculated stopping power ratios s w,a , perturbation factors p and beam quality correction factors k Q was investigated and confirmed a decrese of s w,a by a fraction of a percent for photon and electron beams. This study indicates that the impact of the new ICRU recommendation is within 0.35%. The determined deviations should be taken into account, when widely published Monte Carlo calculated values are examined.
Collapse
Affiliation(s)
- Damian Czarnecki
- Institute of Medical Physics and Radiation Protection, University of Applied Sciences Giessen, Giessen, Germany. University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany
| | | | | |
Collapse
|
35
|
Wulff J, Baumann KS, Verbeek N, Bäumer C, Timmermann B, Zink K. TOPAS/Geant4 configuration for ionization chamber calculations in proton beams. ACTA ACUST UNITED AC 2018; 63:115013. [DOI: 10.1088/1361-6560/aac30e] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
36
|
Carlino A, Gouldstone C, Kragl G, Traneus E, Marrale M, Vatnitsky S, Stock M, Palmans H. End-to-end tests using alanine dosimetry in scanned proton beams. ACTA ACUST UNITED AC 2018; 63:055001. [DOI: 10.1088/1361-6560/aaac23] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
37
|
Gerard A, Vidal M, Floquet V, Rossomme S, Vynckier S, Forthomme J, Heymans V, Herault J. 47. Commissioning of new prototype ProteusOne© PBS proton therapy system. Phys Med 2017. [DOI: 10.1016/j.ejmp.2017.10.072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
|
38
|
Gomà C, Safai S, Vörös S. Reference dosimetry of proton pencil beams based on dose-area product: a proof of concept. Phys Med Biol 2017; 62:4991-5005. [DOI: 10.1088/1361-6560/aa7008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
39
|
Osinga-Blättermann JM, Brons S, Greilich S, Jäkel O, Krauss A. Direct determination of k Q for Farmer-type ionization chambers in a clinical scanned carbon ion beam using water calorimetry. Phys Med Biol 2017; 62:2033-2054. [DOI: 10.1088/1361-6560/aa5bac] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
40
|
Gomà C, Lorentini S, Meer D, Safai S. Reply to comment on 'Proton beam monitor chamber calibration'. Phys Med Biol 2016; 61:6594-601. [PMID: 27535895 DOI: 10.1088/0031-9155/61/17/6594] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This reply shows that the discrepancy of about 3% between Faraday cup dosimetry and reference dosimetry using a cylindrical ionization chamber found in Gomà (2014 Phys. Med. Biol. 59 4961-71) seems to be due to an overestimation of the beam quality correction factors tabulated in IAEA TRS-398 for the cylindrical chamber used, rather than to 'unresolved problems with Faraday cup dosimetry', as suggested by Palmans and Vatnitsky (2016 Phys. Med. Biol. 61 6585-93). Furthermore, this work shows that a good agreement between reference dosimetry and Faraday cup dosimetry is possible, provided accurate beam quality correction factors for proton beams are used. The review on W air values presented by Palmans and Vatnitsky is believed to be inaccurate, as it is based on the imprecise assumption of ionization chamber perturbation correction factors in proton beams being equal to unity.
Collapse
Affiliation(s)
- Carles Gomà
- Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium
| | | | | | | |
Collapse
|