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Berchtold J, Winkler C, Karner J, Groher M, Gaisberger C, Sedlmayer F, Wolf F. Noninvasive inter- and intrafractional motion control in ultrahypofractionated radiation therapy of prostate cancer using RayPilot HypoCath™-a substitute for gold fiducial-based IGRT? Strahlenther Onkol 2024; 200:195-201. [PMID: 37626226 PMCID: PMC10876743 DOI: 10.1007/s00066-023-02125-2] [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: 04/18/2023] [Accepted: 07/11/2023] [Indexed: 08/27/2023]
Abstract
PURPOSE In ultrahypofractionated radiation concepts, managing of intrafractional motion is mandatory because tighter margins are used and random errors resulting from prostate movement are not averaged out over a large number of fractions. Noninvasive live monitoring of prostate movement is a desirable asset for LINAC-based prostate stereotactic body radiation therapy (SBRT). METHODS We prospectively analyzed a novel live tracking device (RayPilot HypoCath™; Micropos Medical AB, Gothenburg, Sweden) where a transmitter is noninvasively positioned in the prostatic urethra using a Foley catheter in 12 patients undergoing ultrahypofractionated intensity-modulated radiation therapy (IMRT) of the prostate. Gold fiducials (Innovative Technology Völp, Innsbruck, Austria) were implanted to allow comparison of accuracy and positional stability of the HypoCath system and its ability to be used as a standalone IGRT method. Spatial stability of the transponder was assessed by analyzing transmitter movement in relation to gold markers (GM) in superimposed kV image pairs. Inter- and intrafractional prostate movement and the impact of its correction were analyzed. RESULTS A total of 64 fractions were analyzed. The average resulting deviation vector compared to the GM-based position was 1.2 mm and 0.7 mm for inter- and intrafractional motion, respectively. The mean intrafractional displacement vector of the prostate was 1.9 mm. Table readjustment due to exceeding the threshold of 3 mm was required in 18.8% of fractions. Repositioning reduced the time spent outside the 3‑mm margin from 7.9% to 3.8% of beam-on time. However, for individual patients, the time spent outside the 3‑mm margin was reduced from to 49% to 19%. CONCLUSION the HypoCath system allows highly accurate and robust intrafractional motion monitoring. In conjunction with cone beam CT (CBCT) for initial patient setup, it could be used as a standalone image-guided radiation therapy (IGRT) system.
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Affiliation(s)
- Johannes Berchtold
- Dpt. of Radiation Oncology, Paracelsus Medical University of Salzburg, Müllner Hauptstraße 48, 5020, Salzburg, Austria
| | - Carmen Winkler
- Paracelsus Medical University of Salzburg, Stubergasse 21, 5020, Salzburg, Austria
| | - Josef Karner
- Dpt. of Radiation Oncology, Paracelsus Medical University of Salzburg, Müllner Hauptstraße 48, 5020, Salzburg, Austria
| | - Michael Groher
- Dpt. of Radiation Oncology, Paracelsus Medical University of Salzburg, Müllner Hauptstraße 48, 5020, Salzburg, Austria
| | - Christoph Gaisberger
- Dpt. of Radiation Oncology, Paracelsus Medical University of Salzburg, Müllner Hauptstraße 48, 5020, Salzburg, Austria
| | - Felix Sedlmayer
- Dpt. of Radiation Oncology, Paracelsus Medical University of Salzburg, Müllner Hauptstraße 48, 5020, Salzburg, Austria
| | - Frank Wolf
- Dpt. of Radiation Oncology, Paracelsus Medical University of Salzburg, Müllner Hauptstraße 48, 5020, Salzburg, Austria.
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De Bari B, Guibert G, Slimani S, Bashar Y, Risse T, Guisolan N, Trouillot J, Abel J, Weber P. Electromagnetic Transmitter-Based Prostate Gating for Dose-Escalated Linac-Based Stereotactic Body Radiation Therapy: An Evaluation of Intrafraction Motion. Curr Oncol 2024; 31:962-974. [PMID: 38392066 PMCID: PMC10887766 DOI: 10.3390/curroncol31020072] [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: 12/06/2023] [Revised: 01/18/2024] [Accepted: 01/22/2024] [Indexed: 02/24/2024] Open
Abstract
BACKGROUND Stereotactic Body Radiotherapy (SBRT) is as a standard treatment for prostate cancer (PCa). Tight margins and high dose gradients are needed, and the precise localization of the target is mandatory. Our retrospective study reports our experience regarding the evaluation of intrafraction prostate motion during LINAC-based SBRT evaluated with a novel electromagnetic (EM) tracking device. This device consists of an integrated Foley catheter with a transmitter connected to a receiver placed on the treatment table. METHODS We analyzed 31 patients who received LINAC-based SBRT using flattening filter-free (FFF) volumetric modulated arc therapy (VMAT). The patients were scheduled to be treated for primary (n = 27) or an intraprostatic recurrent PCa (n = 4). A simulation CT scan was conducted while the patients had a filled bladder (100-150 cc) and an empty rectum, and an EM tracking device was used. The same rectal and bladder conditions were employed during the treatment. The patients received 36.25 Gy delivered over five consecutive fractions on the whole prostate and 40 Gy on the nodule(s) visible via MRI, both delivered with a Simultaneous Integrated Boost approach. The CTV-to-PTV margin was 2 mm for both the identified treatment volumes. Patient positioning was verified with XVI ConeBeam-CT (CBCT) matching before each fraction. When the signals exceeded a 2 mm threshold in any of the three spatial directions, the treatment was manually interrupted. A new XVI CBCT was performed if this offset lasted >20 s. RESULTS We analyzed data about 155 fractions. The median and mean treatment times, calculated per fraction, were 10 m31 s and 12 m44 s (range: 6 m36 s-65 m28 s), and 95% of the fractions were delivered with a maximum time of 27 m48 s. During treatment delivery, the mean and median number of XVI CBCT operations realized during the treatment were 2 and 1 (range: 0-11). During the treatment, the prostate was outside the CTV-to-PTV margin (2 mm), thus necessitating the stoppage of the delivery +/- a reacquisition of the XVI CBCT for 11.2%, 8.9%, and 3.9% of the delivery time in the vertical, longitudinal, and lateral direction, respectively. CONCLUSIONS We easily integrated an EM-transmitter-based gating for prostate LINAC-based SBRT into our normal daily workflow. Using this system, a 2 mm CTV-to-PTV margin could be safely applied. A small number of fractions showed a motion exceeding the predefined 2 mm threshold, which would have otherwise gone undetected without intrafraction motion management.
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Affiliation(s)
- Berardino De Bari
- Radiation Oncology Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland (N.G.)
| | - Geoffroy Guibert
- Medical Physics Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland
| | - Sabrine Slimani
- Radiation Oncology Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland (N.G.)
| | - Yanes Bashar
- Radiation Oncology Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland (N.G.)
| | - Terence Risse
- Medical Physics Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland
| | - Nicole Guisolan
- Radiation Oncology Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland (N.G.)
| | - Juliane Trouillot
- Radiation Oncology Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland (N.G.)
| | - Jonathan Abel
- Radiation Oncology Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland (N.G.)
| | - Patrick Weber
- Medical Physics Department, Réseau Hospitalier Neuchâtelois, CH-2300 La Chaux-de-Fond, Switzerland
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Panizza D, Faccenda V, Lucchini R, Daniotti MC, Trivellato S, Caricato P, Pisoni V, De Ponti E, Arcangeli S. Intrafraction Prostate Motion Management During Dose-Escalated Linac-Based Stereotactic Body Radiation Therapy. Front Oncol 2022; 12:883725. [PMID: 35463373 PMCID: PMC9021501 DOI: 10.3389/fonc.2022.883725] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 03/15/2022] [Indexed: 11/13/2022] Open
Abstract
Background Extreme hypofractionation requires tight planning margins, high dose gradients, and strict adherence to planning criteria in terms of patient positioning and organ motion mitigation. This study reports the first clinical experience worldwide using a novel electromagnetic (EM) tracking device for intrafraction prostate motion management during dose-escalated linac-based stereotactic body radiation therapy (SBRT). Methods Thirteen patients with organ-confined prostate cancer underwent dose-escalated SBRT using flattening filter-free (FFF) volumetric modulated arc therapy (VMAT). The EM tracking device consisted of an integrated Foley catheter with a transmitter. Patients were simulated and treated with a filled bladder and an empty rectum. Setup accuracy was achieved by ConeBeam-CT (CBCT) matching, and motion was tracked during all the procedure. Treatment was interrupted when the signals exceeded a 2 mm threshold in any of the three spatial directions and, unless the offset was transient, target position was re-defined by repeating CBCT. Moreover, the displacements that would have occurred without any intrafraction organ motion management (i.e. no interruptions and repositionings) were simulated. Results In 31 out of 56 monitored fractions (55%), no intervention was required to correct the target position. In 25 (45%) a correction was mandated, but only in 10 (18%), the beam delivery was interrupted. Total treatment time lasted on average 10.2 minutes, 6.7 minutes for setup, and 3.5 minutes for beam delivery. Without any intrafraction motion management, the overall mean treatment time and the mean delivery time would have been 6.9 minutes and 3.2 minutes, respectively. The prostate would have been found outside the tolerance in 8% of the total session time, in 4% of the time during the setup, and in 14% during the beam-on phase. Predominant motion pattern was posterior and its probability increased with time, with a mean motion ≤ 2 mm occurring within 10 minutes. Conclusions EM real-time tracking was successfully implemented for intrafraction motion management during dose-escalated prostate SBRT. Results showed that most of the observed displacements were < 2 mm in any direction; however, there were a non-insignificant number of fractions with motion exceeding the predefined threshold, which would have otherwise gone undetected without intrafraction motion management.
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Affiliation(s)
- Denis Panizza
- Medical Physics Department, ASST Monza, Monza, Italy.,School of Medicine and Surgery, University of Milan Bicocca, Milan, Italy
| | - Valeria Faccenda
- Medical Physics Department, ASST Monza, Monza, Italy.,Department of Physics, University of Milan, Milan, Italy
| | - Raffaella Lucchini
- School of Medicine and Surgery, University of Milan Bicocca, Milan, Italy.,Radiation Oncology Department, ASST Monza, Monza, Italy
| | - Martina Camilla Daniotti
- Medical Physics Department, ASST Monza, Monza, Italy.,Department of Physics, University of Milan, Milan, Italy
| | | | - Paolo Caricato
- Medical Physics Department, ASST Monza, Monza, Italy.,Department of Physics, University of Milan, Milan, Italy
| | | | - Elena De Ponti
- Medical Physics Department, ASST Monza, Monza, Italy.,School of Medicine and Surgery, University of Milan Bicocca, Milan, Italy
| | - Stefano Arcangeli
- School of Medicine and Surgery, University of Milan Bicocca, Milan, Italy.,Radiation Oncology Department, ASST Monza, Monza, Italy
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Target motion management in breast cancer radiation therapy. Radiol Oncol 2021; 55:393-408. [PMID: 34626533 PMCID: PMC8647788 DOI: 10.2478/raon-2021-0040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 08/04/2021] [Indexed: 12/25/2022] Open
Abstract
Background Over the last two decades, breast cancer remains the main cause of cancer deaths in women. To treat this type of cancer, radiation therapy (RT) has proved to be efficient. RT for breast cancer is, however, challenged by intrafractional motion caused by respiration. The problem is more severe for the left-sided breast cancer due to the proximity to the heart as an organ-at-risk. While particle therapy results in superior dose characteristics than conventional RT, due to the physics of particle interactions in the body, particle therapy is more sensitive to target motion. Conclusions This review highlights current and emerging strategies for the management of intrafractional target motion in breast cancer treatment with an emphasis on particle therapy, as a modern RT technique. There are major challenges associated with transferring real-time motion monitoring technologies from photon to particles beams. Surface imaging would be the dominant imaging modality for real-time intrafractional motion monitoring for breast cancer. The magnetic resonance imaging (MRI) guidance and ultra high dose rate (FLASH)-RT seem to be state-of-the-art approaches to deal with 4D RT for breast cancer.
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Eppenga R, Kuhlmann K, Ruers T, Nijkamp J. Accuracy assessment of target tracking using two 5-degrees-of-freedom wireless transponders. Int J Comput Assist Radiol Surg 2019; 15:369-377. [PMID: 31724113 PMCID: PMC6989619 DOI: 10.1007/s11548-019-02088-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 11/04/2019] [Indexed: 12/22/2022]
Abstract
Purpose Surgical navigation systems are generally only applied for targets in rigid areas. For non-rigid areas, real-time tumor tracking can be included to compensate for anatomical changes. The only clinically cleared system using a wireless electromagnetic tracking technique is the Calypso® System (Varian Medical Systems Inc., USA), designed for radiotherapy. It is limited to tracking maximally three wireless 5-degrees-of-freedom (DOF) transponders, all used for tumor tracking. For surgical navigation, a surgical tool has to be tracked as well. In this study, we evaluated whether accurate 6DOF tumor tracking is possible using only two 5DOF transponders, leaving one transponder to track a tool. Methods Two methods were defined to derive 6DOF information out of two 5DOF transponders. The first method uses the vector information of both transponders (TTV), and the second method combines the vector information of one transponder with the distance vector between the transponders (OTV). The accuracy of tracking a rotating object was assessed for each method mimicking clinically relevant and worst-case configurations. Accuracy was compared to using all three transponders to derive 6DOF (Default method). An optical tracking system was used as a reference for accuracy. Results The TTV method performed best and was as accurate as the Default method for almost all transponder configurations (median errors < 0.5°, 95% confidence interval < 3°). Only when the angle between the transponders was less than 2°, the TTV method was inaccurate and the OTV method may be preferred. The accuracy of both methods was independent of the angle of rotation, and only the OTV method was sensitive to the plane of rotation. Conclusion These results indicate that accurate 6DOF tumor tracking is possible using only two 5DOF transponders. This encourages further development of a wireless EM surgical navigation approach using a readily available clinical system.
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Affiliation(s)
- Roeland Eppenga
- Department of Surgical Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands
| | - Koert Kuhlmann
- Department of Surgical Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands
| | - Theo Ruers
- Department of Surgical Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.
- Nanobiophysics Group, Faculty TNW, University of Twente, Enschede, The Netherlands.
| | - Jasper Nijkamp
- Department of Surgical Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands
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Bertholet J, Knopf A, Eiben B, McClelland J, Grimwood A, Harris E, Menten M, Poulsen P, Nguyen DT, Keall P, Oelfke U. Real-time intrafraction motion monitoring in external beam radiotherapy. Phys Med Biol 2019; 64:15TR01. [PMID: 31226704 PMCID: PMC7655120 DOI: 10.1088/1361-6560/ab2ba8] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/10/2019] [Accepted: 06/21/2019] [Indexed: 12/25/2022]
Abstract
Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to 'see what we treat, as we treat' and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-time treatment adaptation. Additional equipment, such as stereoscopic kilovoltage (kV) imaging, ultrasound transducers and electromagnetic transponders, has been developed for intrafraction motion monitoring on conventional linacs. Magnetic resonance imaging (MRI) has been integrated with cobalt treatment units and more recently with linacs. In addition to hardware innovation, software development has played a substantial role in the development of motion monitoring methods based on respiratory motion surrogates and planar kV or Megavoltage (MV) imaging that is available on standard equipped linacs. In this paper, we review and compare the different intrafraction motion monitoring methods proposed in the literature and demonstrated in real-time on clinical data as well as their possible future developments. We then discuss general considerations on validation and quality assurance for clinical implementation. Besides photon RT, particle therapy is increasingly used to treat moving targets. However, transferring motion monitoring technologies from linacs to particle beam lines presents substantial challenges. Lessons learned from the implementation of real-time intrafraction monitoring for photon RT will be used as a basis to discuss the implementation of these methods for particle RT.
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Affiliation(s)
- Jenny Bertholet
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
- Author to whom any correspondence should be
addressed
| | - Antje Knopf
- Department of Radiation Oncology,
University Medical Center
Groningen, University of Groningen, The
Netherlands
| | - Björn Eiben
- Department of Medical Physics and Biomedical
Engineering, Centre for Medical Image Computing, University College London, London,
United Kingdom
| | - Jamie McClelland
- Department of Medical Physics and Biomedical
Engineering, Centre for Medical Image Computing, University College London, London,
United Kingdom
| | - Alexander Grimwood
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
| | - Emma Harris
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
| | - Martin Menten
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
| | - Per Poulsen
- Department of Oncology, Aarhus University Hospital, Aarhus,
Denmark
| | - Doan Trang Nguyen
- ACRF Image X Institute, University of Sydney, Sydney,
Australia
- School of Biomedical Engineering,
University of Technology
Sydney, Sydney, Australia
| | - Paul Keall
- ACRF Image X Institute, University of Sydney, Sydney,
Australia
| | - Uwe Oelfke
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS
Foundation Trust, London, United
Kingdom
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Biston MC, Zaragori T, Delcoudert L, Fargier-Voiron M, Munoz A, Gorsse C, Sarrut D, Pommier P. Comparison of electromagnetic transmitter and ultrasound imaging for intrafraction monitoring of prostate radiotherapy. Radiother Oncol 2019; 136:1-8. [DOI: 10.1016/j.radonc.2019.03.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/18/2019] [Accepted: 03/20/2019] [Indexed: 01/04/2023]
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Abstract
The world is embracing the information age, with real-time data at hand to assist with many decisions. Similarly, in cancer radiotherapy we are inexorably moving toward using information in a smarter and faster fashion, to usher in the age of real-time adaptive radiotherapy. The three critical steps of real-time adaptive radiotherapy, aligned with driverless vehicle technology are a continuous see, think, and act loop. See: use imaging systems to probe the patient anatomy or physiology as it evolves with time. Think: use current and prior information to optimize the treatment using the available adaptive degrees of freedom. Act: deliver the real-time adapted treatment. This paper expands upon these three critical steps for real-time adaptive radiotherapy, provides a historical context, reviews the clinical rationale, and gives a future outlook for real-time adaptive radiotherapy.
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Affiliation(s)
- Paul Keall
- ACRF Image X Institute, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.
| | - Per Poulsen
- Department of Oncology and Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Jeremy T Booth
- Northern Sydney Cancer Centre, Royal North Shore Hospital and Institute of Medical Physics, School of Physics, University of Sydney, Sydney Australia
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Vanhanen A, Syrén H, Kapanen M. Localization accuracy of two electromagnetic tracking systems in prostate cancer radiotherapy: A comparison with fiducial marker based kilovoltage imaging. Phys Med 2018; 56:10-18. [PMID: 30527084 DOI: 10.1016/j.ejmp.2018.11.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 10/02/2018] [Accepted: 11/10/2018] [Indexed: 10/27/2022] Open
Abstract
The aim of this study was to evaluate the localization accuracy of electromagnetic (EM) tracking systems RayPilot (Micropos Medical AB) and Calypso (Varian Medical Systems) in prostate cancer radiotherapy. The accuracy was assessed by comparing couch shifts obtained with the EM methods to the couch shifts determined by simultaneous fiducial marker (FM) based orthogonal kilovoltage (kV) imaging. Agreement between the methods was compared using Bland-Altman analysis. Interfractional positional stability of the FMs, RayPilot transmitters and Calypso transponders was investigated. 582 fractions from 22 RayPilot patients and 335 fractions from 26 Calypso patients were analyzed. Mean (± standard deviation (SD)) differences between RayPilot and kV imaging were 0.3 ± 2.2, -2.2 ± 2.4 and -0.0 ± 1.0 mm in anterior-posterior (AP), superior-inferior (SI) and left-right (LR) directions, respectively. Corresponding 95% limits of agreement (LOA) were ±4.3, ±4.7 and ±2.1 mm around the mean. Mean (±SD) differences between Calypso and kV imaging were -0.2 ± 0.6, 0.1 ± 0.5 and -0.1 ± 0.4 mm in AP, SI and LR directions, respectively, and corresponding LOAs were ±1.3, ±1.0 and ±0.8 mm around the mean. FMs and transponders were stable: SD of intermarker and intertransponder distances was 0.5 mm. Transmitters were unstable: mean caudal transmitter shift of 1.8 ± 2.0 mm was observed. Results indicate that the localization accuracy of the Calypso is comparable to kV imaging of fiducials and the methods could be used interchangeably. The localization accuracy of the RayPilot is affected by transmitter instability and the positioning of the patient should be verified by other setup techniques. The study is part of clinical trial NCT02319239.
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Affiliation(s)
- A Vanhanen
- Department of Oncology, Unit of Radiotherapy, Tampere University Hospital, POB-2000, 33521 Tampere, Finland; Department of Medical Physics, Medical Imaging Center, Tampere University Hospital, POB-2000, 33521 Tampere, Finland.
| | - H Syrén
- Micropos Medical AB, Gothenburg, Sweden
| | - M Kapanen
- Department of Oncology, Unit of Radiotherapy, Tampere University Hospital, POB-2000, 33521 Tampere, Finland; Department of Medical Physics, Medical Imaging Center, Tampere University Hospital, POB-2000, 33521 Tampere, Finland
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