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Neppl S, Kurz C, Köpl D, Yohannes I, Schneider M, Bondesson D, Rabe M, Belka C, Dietrich O, Landry G, Parodi K, Kamp F. Measurement-based range evaluation for quality assurance of CBCT-based dose calculations in adaptive proton therapy. Med Phys 2021; 48:4148-4159. [PMID: 34032301 DOI: 10.1002/mp.14995] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 04/08/2021] [Accepted: 05/10/2021] [Indexed: 12/30/2022] Open
Abstract
PURPOSE The implementation of volumetric in-room imaging for online adaptive radiotherapy makes extensive testing of this image data for treatment planning necessary. Especially for proton beams the higher sensitivity to stopping power properties of the tissue results in more stringent requirements. Current approaches mainly focus on recalculation of the plans on the new image data, lacking experimental verification, and ignoring the impact on the plan re-optimization process. The aim of this study was to use gel and film dosimetry coupled with a three-dimensional (3D) printed head phantom (based on the planning CT of the patient) for 3D range verification of intensity-corrected cone beam computed tomography (CBCT) image data for adaptive proton therapy. METHODS Single field uniform dose pencil beam scanning proton plans were optimized for three different patients on the patients' planning CT (planCT) and the patients' intensity-corrected CBCT (scCBCT) for the same target volume using the same optimization constraints. The CBCTs were corrected on projection level using the planCT as a prior. The dose optimized on planCT and recalculated on scCBCT was compared in terms of proton range differences (80% distal fall-off, recalculation). Moreover, the dose distribution resulting from recalculation of the scCBCT-optimized plan on the planCT and the original planCT dose distribution were compared (simulation). Finally, the two plans of each patient were irradiated on the corresponding patient-specific 3D printed head phantom using gel dosimetry inserts for one patient and film dosimetry for all three patients. Range differences were extracted from the measured dose distributions. The measured and the simulated range differences were corrected for range differences originating from the initial plans and evaluated. RESULTS The simulation approach showed high agreement with the standard recalculation approach. The median values of the range differences of these two methods agreed within 0.1 mm and the interquartile ranges (IQRs) within 0.3 mm for all three patients. The range differences of the film measurement were accurately matching with the simulation approach in the film plane. The median values of these range differences deviated less than 0.1 mm and the IQRs less than 0.4 mm. For the full 3D evaluation of the gel range differences, the median value and IQR matched those of the simulation approach within 0.7 and 0.5 mm, respectively. scCBCT- and planCT-based dose distributions were found to have a range agreement better than 3 mm (median and IQR) for all considered scenarios (recalculation, simulation, and measurement). CONCLUSIONS The results of this initial study indicate that an online adaptive proton workflow based on scatter-corrected CBCT image data for head irradiations is feasible. The novel presented measurement- and simulation-based method was shown to be equivalent to the standard literature recalculation approach. Additionally, it has the capability to catch effects of image differences on the treatment plan optimization. This makes the measurement-based approach particularly interesting for quality assurance of CBCT-based online adaptive proton therapy. The observed uncertainties could be kept within those of the registration and positioning. The proposed validation could also be applied for other alternative in-room images, e.g. for MR-based pseudoCTs.
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Affiliation(s)
- Sebastian Neppl
- Department of Radiation Oncology, University Hospital, LMU Munich, 81377, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), 85748, Garching bei München, Germany
| | - Christopher Kurz
- Department of Radiation Oncology, University Hospital, LMU Munich, 81377, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), 85748, Garching bei München, Germany
| | - Daniel Köpl
- Rinecker Proton Therapy Center, 81371, Munich, Germany
| | | | - Moritz Schneider
- Department of Radiology, University Hospital, LMU Munich, 81377, Munich, Germany.,Comprehensive Pneumology Center Munich (CPC-M), German Center for Lung Research (DZL), 81377, Munich, Germany
| | - David Bondesson
- Department of Radiology, University Hospital, LMU Munich, 81377, Munich, Germany.,Comprehensive Pneumology Center Munich (CPC-M), German Center for Lung Research (DZL), 81377, Munich, Germany
| | - Moritz Rabe
- Department of Radiation Oncology, University Hospital, LMU Munich, 81377, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), 85748, Garching bei München, Germany
| | - Claus Belka
- Department of Radiation Oncology, University Hospital, LMU Munich, 81377, Munich, Germany.,German Cancer Consortium (DKTK), Partner site Munich, 81377, Munich, Germany
| | - Olaf Dietrich
- Department of Radiology, University Hospital, LMU Munich, 81377, Munich, Germany
| | - Guillaume Landry
- Department of Radiation Oncology, University Hospital, LMU Munich, 81377, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), 85748, Garching bei München, Germany
| | - Katia Parodi
- Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), 85748, Garching bei München, Germany
| | - Florian Kamp
- Department of Radiation Oncology, University Hospital, LMU Munich, 81377, Munich, Germany
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Gerlach S, Pinto M, Kurichiyanil N, Grau C, Hérault J, Hillbrand M, Poulsen PR, Safai S, Schippers JM, Schwarz M, Søndergaard CS, Tommasino F, Verroi E, Vidal M, Yohannes I, Schreiber J, Parodi K. Corrigendum: Beam characterization and feasibility study for a small animal irradiation platform at clinical proton therapy facilities (2020 Phys. Med. Biol.65 245045). Phys Med Biol 2021; 66. [PMID: 34037545 DOI: 10.1088/1361-6560/abf00e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 03/18/2021] [Indexed: 11/11/2022]
Affiliation(s)
- S Gerlach
- Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, D-85748 Garching, Germany
| | - M Pinto
- Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, D-85748 Garching, Germany
| | - N Kurichiyanil
- Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, D-85748 Garching, Germany
| | - C Grau
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.,Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - J Hérault
- Centre Antoine Lacassagne, Nice, France.,Fédération Claude Lalanne-Université Côte d'Azur, Nice, France
| | - M Hillbrand
- Rinecker Proton Therapy Center, München, Germany
| | - P R Poulsen
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.,Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - S Safai
- Paul Scherrer Institute, Villigen, Switzerland
| | | | - M Schwarz
- Trento Institute for Fundamental Physics and Applications, National Institute for Nuclear Physics, Povo, Italy.,Protontherapy Department, Azienda Provinciale per i Servizi Sanitari, Trento, Italy
| | - C S Søndergaard
- Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - F Tommasino
- Trento Institute for Fundamental Physics and Applications, National Institute for Nuclear Physics, Povo, Italy.,Department of Physics, University of Trento, Povo, Italy
| | - E Verroi
- Trento Institute for Fundamental Physics and Applications, National Institute for Nuclear Physics, Povo, Italy
| | - M Vidal
- Centre Antoine Lacassagne, Nice, France.,Fédération Claude Lalanne-Université Côte d'Azur, Nice, France
| | - I Yohannes
- Rinecker Proton Therapy Center, München, Germany
| | - J Schreiber
- Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, D-85748 Garching, Germany
| | - K Parodi
- Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, D-85748 Garching, Germany
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Niepel KB, Stanislawski M, Wuerl M, Doerringer F, Pinto M, Dietrich O, Ertl-Wagner B, Lalonde A, Bouchard H, Pappas E, Yohannes I, Hillbrand M, Landry G, Parodi K. Animal tissue-based quantitative comparison of dual-energy CT to SPR conversion methods using high-resolution gel dosimetry. Phys Med Biol 2021; 66. [DOI: 10.1088/1361-6560/abbd14] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 09/30/2020] [Indexed: 12/16/2022]
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Gerlach S, Pinto M, Kurichiyanil N, Grau C, Hérault J, Hillbrand M, Poulsen PR, Safai S, Schippers JM, Schwarz M, Søndergaard CS, Tommasino F, Verroi E, Vidal M, Yohannes I, Schreiber J, Parodi K. Beam characterization and feasibility study for a small animal irradiation platform at clinical proton therapy facilities. Phys Med Biol 2020; 65:245045. [DOI: 10.1088/1361-6560/abc832] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Prasetio H, Yohannes I, Bert C. Effect of VERO pan-tilt motion on the dose distribution. J Appl Clin Med Phys 2017; 18:144-154. [PMID: 28585287 PMCID: PMC5874935 DOI: 10.1002/acm2.12112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 03/31/2017] [Accepted: 04/14/2017] [Indexed: 11/11/2022] Open
Abstract
Tumor tracking is an option for intra-fractional motion management in radiotherapy. The VERO gimbal tracking system creates a unique beam geometry and understanding the effect of the gimbal motion in terms of dose distribution is important to assess the dose deviation from the reference conditions. Beam profiles, output factors (OF) and percentage depth doses (PDD) were measured and evaluated to investigate this effect. In order to find regions affected by the pan-tilt motion, synthesized 2D dose distributions were generated. An evaluation of the 2D dose distribution with the reference position was done using dose difference criteria 1%-4%. The OF and point dose at central axis were measured and compared with the reference position. Furthermore, the PDDs were measured using a special monitoring approach to filtering inaccurate points during the acquisition. Beam profiles evaluation showed that the effect of pan-tilt at inline direction was stronger than at the crossline direction. The maximum average deviation of the full width half maximum (FWHM), flatness, symmetry, penumbra left and right were 0.39 ± 0.25 mm, 0.62 ± 0.50%, 0.76 ± 0.59%, 0.22 ± 0.16 mm, and 0.19 ± 0.15 mm respectively. The ÔF and the measured dose average deviation were <0.5%. The mechanical accuracies during the PDD measurements were 0.28 ± 0.09 mm and 0.21 ± 0.09 mm for pan and tilt and pan or tilt position. The PDD average deviations were 0.58 ± 0.26 % and 0.54 ± 0.25 % for pan-or-tilt and pan-and-tilt position respectively. All the results showed that the deviation at pan and tilt position are higher than pan or tilt. The most influences were observed for the penumbra region and the shift of radiation beam path.
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Affiliation(s)
- Heru Prasetio
- Department of Radiation OncologyUniversitätsklinikum ErlangenFriedrich‐Alexander‐Universität Erlangen‐NürnbergErlangenGermany
| | - Indra Yohannes
- Department of Radiation OncologyUniversitätsklinikum ErlangenFriedrich‐Alexander‐Universität Erlangen‐NürnbergErlangenGermany
| | - Christoph Bert
- Department of Radiation OncologyUniversitätsklinikum ErlangenFriedrich‐Alexander‐Universität Erlangen‐NürnbergErlangenGermany
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Speer S, Klein A, Kober L, Weiss A, Yohannes I, Bert C. Automation of radiation treatment planning : Evaluation of head and neck cancer patient plans created by the Pinnacle 3 scripting and Auto-Planning functions. Strahlenther Onkol 2017; 193:656-665. [PMID: 28653120 DOI: 10.1007/s00066-017-1150-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 05/10/2017] [Indexed: 12/25/2022]
Abstract
BACKGROUND Intensity-modulated radiotherapy (IMRT) techniques are now standard practice. IMRT or volumetric-modulated arc therapy (VMAT) allow treatment of the tumor while simultaneously sparing organs at risk. Nevertheless, treatment plan quality still depends on the physicist's individual skills, experiences, and personal preferences. It would therefore be advantageous to automate the planning process. This possibility is offered by the Pinnacle3 treatment planning system (Philips Healthcare, Hamburg, Germany) via its scripting language or Auto-Planning (AP) module. MATERIALS AND METHODS AP module results were compared to in-house scripts and manually optimized treatment plans for standard head and neck cancer plans. Multiple treatment parameters were scored to judge plan quality (100 points = optimum plan). Patients were initially planned manually by different physicists and re-planned using scripts or AP. RESULTS AND DISCUSSION Script-based head and neck plans achieved a mean of 67.0 points and were, on average, superior to manually created (59.1 points) and AP plans (62.3 points). Moreover, they are characterized by reproducibility and lower standard deviation of treatment parameters. Even less experienced staff are able to create at least a good starting point for further optimization in a short time. However, for particular plans, experienced planners perform even better than scripts or AP. Experienced-user input is needed when setting up scripts or AP templates for the first time. Moreover, some minor drawbacks exist, such as the increase of monitor units (+35.5% for scripted plans). CONCLUSION On average, automatically created plans are superior to manually created treatment plans. For particular plans, experienced physicists were able to perform better than scripts or AP; thus, the benefit is greatest when time is short or staff inexperienced.
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Affiliation(s)
- Stefan Speer
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Universitätsstraße 27, 91054, Erlangen, Germany.
| | - Andreas Klein
- EKS Engineering GmbH, Dr.-Mack-Straße 88, 90762, Fürth, Germany
| | - Lukas Kober
- Strahlentherapie Tauber-Franken, Uhlandstraße 7, 97980, Bad Mergentheim, Germany
| | - Alexander Weiss
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Universitätsstraße 27, 91054, Erlangen, Germany
| | - Indra Yohannes
- Rinecker Proton Therapy Center, Schäftlarnstraße 133, 81371, Munich, Germany
| | - Christoph Bert
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Universitätsstraße 27, 91054, Erlangen, Germany
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Yohannes I, Prasetio H, Kallis K, Bert C. Dosimetric accuracy of the cone-beam CT-based treatment planning of the Vero system: a phantom study. J Appl Clin Med Phys 2016; 17:106-113. [PMID: 27455496 PMCID: PMC5690058 DOI: 10.1120/jacmp.v17i4.6194] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/25/2016] [Accepted: 02/23/2016] [Indexed: 11/23/2022] Open
Abstract
We report an investigation on the accuracy of dose calculation based on the cone‐beam computed tomography (CBCT) images of the nonbowtie filter kV imaging system of the Vero linear accelerator. Different sets of materials and tube voltages were employed to generate the Hounsfield unit lookup tables (HLUTs) for both CBCT and fan‐beam CT (FBCT) systems. The HLUTs were then implemented for the dose calculation in a treatment planning system (TPS). Dosimetric evaluation was carried out on an in‐house‐developed cube phantom that consists of water‐equivalent slabs and inhomogeneity inserts. Two independent dosimeters positioned in the cube phantom were used in this study for point‐dose and two‐dimensional (2D) dose distribution measurements. The differences of HLUTs from various materials and tube voltages in both CT systems resulted in differences in dose calculation accuracy. We found that the higher the tube voltage used to obtain CT images, the better the point‐dose calculation and the gamma passing rate of the 2D dose distribution agree to the values determined in the TPS. Moreover, the insert materials that are not tissue‐equivalent led to higher dose‐calculation inaccuracy. There were negligible differences in dosimetric evaluation between the CBCT‐ and FBCT‐based treatment planning if the HLUTs were generated using the tissue‐equivalent materials. In this study, the CBCT images of the Vero system from a complex inhomogeneity phantom can be applied for the TPS dose calculation if the system is calibrated using tissue‐equivalent materials scanned at high tube voltage (i.e., 120 kV). PACS number(s): 87.55.de, 87.56.Fc, 87.57.qp
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Yohannes I, Hild S, Vasiliniuc S, Langner O, Graeff C, Bert C. Technical Note: Radiation properties of tissue- and water-equivalent materials formulated using the stoichiometric analysis method in charged particle therapy. Med Phys 2015; 43:308. [DOI: 10.1118/1.4938587] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Yohannes I, Prasetio H, Bert C. Noncoplanar verification: a feasibility study using Philips' Pinnacle3 treatment planning system. J Appl Clin Med Phys 2015; 16:84–90. [PMID: 26699558 PMCID: PMC5691022 DOI: 10.1120/jacmp.v16i6.5492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 08/17/2015] [Accepted: 07/07/2015] [Indexed: 01/09/2023] Open
Abstract
Noncoplanar fields are normally used to improve the dose conformity of the target while sparing organs at risk. One of the methods to verify the dose distribution from the noncoplanar fields is by comparing their planar dose distributions from the treatment planning system (TPS) and the measured ones; for example, using film or electronic portal imaging devices (EPID). The planar dose distributions of the measurement tools, that are normally perpendicular to the central axis of the beam, can be calculated by creating special structures to mimic them in the TPS. With TPS commercially available today, however, it is not easy to create these special structures, especially in the noncoplanar configuration. For this work, we have written in‐house scripts in the Pinnacle3 TPS that can create the structures and define them as virtual planes. These virtual planes can be generated for any arbitrary gantry and couch angles, as well as source to planar distance, so that the planar dose maps at these planes can be computed. Two independent quality assurance (QA) tools were used to validate the planar dose distributions computed using the scripts for three open fields and one IMRT field at several different couch angles. The absolute planar dose patterns measured by the QA tools for all fields at all couch angles were found to be in good agreement, more than 95% (gamma criteria 3% delta dose and 3 mm distance to agreement), with the calculated ones by TPS. The results of this feasibility study can be valuable either for pretreatment dose verification or for in vivo dosimetry that directly implements the planar dose distributions from the TPS, particularly for the noncoplanar fields. PACS numbers: 87.55.de, 87.55.Qr, 87.56.Fc
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Yohannes I, Hild S, Vasiliniuc S, Langner O, Graeff C, Bert C. SU-E-T-663: Radiation Properties of a Water-Equivalent Material Formulated Using the Stoichiometric Analysis Method in Heavy Charged Particle Therapy. Med Phys 2015. [DOI: 10.1118/1.4925026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Knopf A, Nill S, Yohannes I, Graeff C, Dowdell S, Kurz C, Sonke JJ, Biegun AK, Lang S, McClelland J, Champion B, Fast M, Wölfelschneider J, Gianoli C, Rucinski A, Baroni G, Richter C, van de Water S, Grassberger C, Weber D, Poulsen P, Shimizu S, Bert C. Challenges of radiotherapy: report on the 4D treatment planning workshop 2013. Phys Med 2014; 30:809-15. [PMID: 25172392 DOI: 10.1016/j.ejmp.2014.07.341] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 07/23/2014] [Accepted: 07/28/2014] [Indexed: 01/27/2023] Open
Abstract
This report, compiled by experts on the treatment of mobile targets with advanced radiotherapy, summarizes the main conclusions and innovations achieved during the 4D treatment planning workshop 2013. This annual workshop focuses on research aiming to advance 4D radiotherapy treatments, including all critical aspects of time resolved delivery, such as in-room imaging, motion detection, motion managing, beam application, and quality assurance techniques. The report aims to revise achievements in the field and to discuss remaining challenges and potential solutions. As main achievements advances in the development of a standardized 4D phantom and in the area of 4D-treatment plan optimization were identified. Furthermore, it was noticed that MR imaging gains importance and high interest for sequential 4DCT/MR data sets was expressed, which represents a general trend of the field towards data covering a longer time period of motion. A new point of attention was work related to dose reconstructions, which may play a major role in verification of 4D treatment deliveries. The experimental validation of results achieved by 4D treatment planning and the systematic evaluation of different deformable image registration methods especially for inter-modality fusions were identified as major remaining challenges. A challenge that was also suggested as focus for future 4D workshops was the adaptation of image guidance approaches from conventional radiotherapy into particle therapy. Besides summarizing the last workshop, the authors also want to point out new evolving demands and give an outlook on the focus of the next workshop.
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Affiliation(s)
| | | | | | | | | | | | | | - Aleksandra K Biegun
- KVI-Center for Advanced Radiation Technology, University of Groningen, Netherlands
| | | | | | | | | | | | - Chiara Gianoli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Italy; Department of Radiation Oncology, Heidelberg University Hospital, Germany
| | - Antoni Rucinski
- Radiation Oncology Department, SLK-Klinik Heilbronn, Germany
| | - Guido Baroni
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano and Bioengineering Unit, CNAO Foundation, Pavia, Italy
| | - Christian Richter
- Oncoray - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital C.G. Carus, TU Dresden, Helmholtz-Zentrum Dresden-Rossendorf, DKTK, Dresden, Germany
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Yohannes I, Kolditz D, Langner O, Kalender WA. A formulation of tissue- and water-equivalent materials using the stoichiometric analysis method for CT-number calibration in radiotherapy treatment planning. Phys Med Biol 2012; 57:1173-90. [PMID: 22330195 DOI: 10.1088/0031-9155/57/5/1173] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Yohannes I, Kolditz D, Kalender WA. Semiempirical analysis of materials' elemental composition to formulate tissue-equivalent materials: a preliminary study. Phys Med Biol 2011; 56:2963-77. [DOI: 10.1088/0031-9155/56/10/005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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