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Kaliyaperumal V, Abraham S, Veni M, Banerjee S, Tamilselvan S, Gupta D, Dayanithi K, Manigandan D, Mishra S, Bisht SS, Kataria T. Dosimetric Comparison of Robotic and Linear Accelerator Multi-Leaf Collimator-Based Stereotactic Radiosurgery for Arteriovenous Malformation. J Med Phys 2021; 46:16-25. [PMID: 34267485 PMCID: PMC8240906 DOI: 10.4103/jmp.jmp_79_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 03/29/2021] [Accepted: 03/29/2021] [Indexed: 11/17/2022] Open
Abstract
Purpose: To investigate the dosimetric comparison of different collimators which are used in robotic radiosurgery (cyberknife-CK) and linear accelerator (LINAC) for stereotactic radiosurgery (SRS) in arteriovenous malformation (AVM). Materials and Methods: Twenty-five AVM patients were planned in CK using FIXED cone, IRIS collimator, and multi-leaf collimator (MLC) based in LINAC. Dosimetric comparison was performed using Paddick conformity index (CIPaddick) and International Commission on Radiation Units and measurements (ICRU) homogeneity index (HIICRU), gradient score (GS), normal brain dose received by 10cc (D10cc) and critical structure (brain stem, optic chiasma, optic nerves) doses. Paired sample t-test was used for statistical analysis. Results: Mean treatment volume was 3.16cc (standard deviation ± 4.91cc). No significant deviation (P =0.45, 0.237 for FIXED vs. IRIS and FIXED vs. MLC, respectively) was found in target coverage. For CIPaddick, the mean difference (MD) between FIXED- and MLC-based plans was 0.16(P = 0.001); For HIICRU, difference between FIXED and IRIS was insignificant (0.5, P = 0.823); but, when FIXED versus MLC, the deviation was 7.99% (P = 0.002). In FIXED- and MLC-based plans, significant difference was found in GS70 and GS40 (P < 0.041 and 0.005, respectively). MD between FIXED- and MLC-based plans for normal brain for 5Gy, 10Gy, 12Gy, and 20Gy were 36.08cc (P = 0.009), 7.12cc (P = 0.000), 5.84cc (P = 0.000) and 1.56cc (P = 0.000), respectively. AVM volume <0.7cc should be treated with CK FIXED and >0.7cc were treated by using FIXED or IRIS collimators. AVM volume > 1.4cc can be treated by either LINAC MLC-based SRS or CK. Conclusion: Our study shows CK collimator (IRIS and FIXED) could be able to treat brain AVMs in any size. Linac MLC-based SRS has some limitations in terms of conformity and low-dose spillage, and advantages like reduced treatment time and MU.
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Affiliation(s)
- Venkatesan Kaliyaperumal
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Susan Abraham
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Maragatha Veni
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Susovan Banerjee
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - S Tamilselvan
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Deepak Gupta
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - K Dayanithi
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - D Manigandan
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Saumyaranjan Mishra
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Shyam Singh Bisht
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
| | - Tejinder Kataria
- Division of Radiation Oncology, Medanta Cancer Institute, Medanta The Medicity, Gurgaon, Haryana, India
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Bry V, Licon AL, McCulloch J, Kirby N, Myers P, Saenz D, Stathakis S, Papanikolaou N, Rasmussen K. Quantifying false positional corrections due to facial motion using SGRT with open-face Masks. J Appl Clin Med Phys 2021; 22:172-183. [PMID: 33739569 PMCID: PMC8035563 DOI: 10.1002/acm2.13170] [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: 08/10/2020] [Revised: 12/09/2020] [Accepted: 12/25/2020] [Indexed: 11/17/2022] Open
Abstract
Purpose Studies have evaluated the viability of using open‐face masks as an immobilization technique to treat intracranial and head and neck cancers. This method offers less stress to the patient with comparable accuracy to closed‐face masks. Open‐face masks permit implementation of surface guided radiation therapy (SGRT) to assist in positioning and motion management. Research suggests that changes in patient facial expressions may influence the SGRT system to generate false positional corrections. This study aims to quantify these errors produced by the SGRT system due to face motion. Methods Ten human subjects were immobilized using open‐face masks. Four discrete SGRT regions of interest (ROIs) were analyzed based on anatomical features to simulate different mask openings. The largest ROI was lateral to the cheeks, superior to the eyebrows, and inferior to the mouth. The smallest ROI included only the eyes and bridge of the nose. Subjects were asked to open and close their eyes and simulate fear and annoyance and peak isocenter shifts were recorded. This was performed in both standard and SRS specific resolutions with the C‐RAD Catalyst HD system. Results All four ROIs analyzed in SRS and Standard resolutions demonstrated an average deviation of 0.3 ± 0.3 mm for eyes closed and 0.4 ± 0.4 mm shift for eyes open, and 0.3 ± 0.3 mm for eyes closed and 0.8 ± 0.9 mm shift for eyes open. The average deviation observed due to changing facial expressions was 1.4 ± 0.9 mm for SRS specific and 1.6 ± 1.6 mm for standard resolution. Conclusion The SGRT system can generate false positional corrections for face motion and this is amplified at lower resolutions and smaller ROIs. These errors should be considered in the overall tolerances and treatment plan when using open‐face masks with SGRT and may warrant additional radiographic imaging.
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Affiliation(s)
- Victoria Bry
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Anna Laura Licon
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - James McCulloch
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Neil Kirby
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Pamela Myers
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Daniel Saenz
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Sotirios Stathakis
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Niko Papanikolaou
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Karl Rasmussen
- Department of Radiation Oncology, School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
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Mangesius J, Seppi T, Weigel R, Arnold CR, Vasiljevic D, Goebel G, Lukas P, Ganswindt U, Nevinny-Stickel M. Intrafractional 6D head movement increases with time of mask fixation during stereotactic intracranial RT-sessions. Radiat Oncol 2019; 14:231. [PMID: 31852497 PMCID: PMC6921566 DOI: 10.1186/s13014-019-1425-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 11/22/2019] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND The present study investigates the intrafractional accuracy of a frameless thermoplastic mask used for head immobilization during stereotactic radiotherapy. Non-invasive masks cannot completely prohibit head movements. Previous studies attempted to estimate the magnitude of intrafractional inaccuracy by means of pre- and postfractional measurements only. However, this might not be sufficient to accurately map also intrafractional head movements. MATERIALS AND METHODS Intrafractional deviation of mask-fixed head positions was measured in five patients during a total of 94 fractions by means of close-meshed repeated ExacTrac measurements (every 1.4 min) conducted during the entire treatment session. A median of six (range: 4 to 11) measurements were recorded per fraction, delivering a dataset of 453 measurements. RESULTS Random errors (SD) for the x, y and z axes were 0.27 mm, 0.29 mm and 0.29 mm, respectively. Median 3D deviation was 0.29 mm. Of all 3D intrafractional motions, 5.5 and 0.4% exceeded 1 mm and 2 mm, respectively. A moderate correlation between treatment duration and mean 3D displacement was determined (rs = 0.45). Mean 3D deviation increased from 0.21 mm (SD = 0.26 mm) in the first 2 min to a maximum of 0.53 mm (SD = 0.31 mm) after 10 min of treatment time. CONCLUSION Pre- and post-treatment measurement is not sufficient to adequately determine the range of intrafractional head motion. Thermoplastic masks provide both reliable interfractional and intrafractional immobilization for image-guided stereotactic hypofractionated radiotherapy. Greater positioning accuracy may be obtained by reducing treatment duration (< 6 min) and applying intrafractional correction. TRIAL REGISTRATION Clinicaltrials.gov, NCT03896555, Registered 01 April 2019 - retrospectively registered.
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Affiliation(s)
- Julian Mangesius
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Thomas Seppi
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Rocco Weigel
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Christoph Reinhold Arnold
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Danijela Vasiljevic
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Georg Goebel
- Department of Medical Statistics, Informatics and Health Economics, Medical University of Innsbruck, Innsbruck, Austria
| | - Peter Lukas
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Ute Ganswindt
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
| | - Meinhard Nevinny-Stickel
- Department of Therapeutic Radiology and Oncology, Medical University of Innsbruck, Anichstraße 35, A-6020 Innsbruck, Austria
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Carminucci A, Nie K, Weiner J, Hargreaves E, Danish SF. Assessment of motion error for frame-based and noninvasive mask-based fixation using the Leksell Gamma Knife Icon radiosurgery system. J Neurosurg 2018; 129:133-139. [DOI: 10.3171/2018.7.gks181516] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 07/24/2018] [Indexed: 11/06/2022]
Abstract
OBJECTIVEThe Leksell Gamma Knife Icon (GK Icon) radiosurgery system can utilize cone-beam computed tomography (CBCT) to evaluate motion error. This study compares the accuracy of frame-based and frameless mask-based fixation using the Icon system.METHODSA retrospective cohort study was conducted to evaluate patients who had undergone radiosurgery with the GK Icon system between June and December 2017. Patients were immobilized in either a stereotactic head frame or a noninvasive thermoplastic mask with stereotactic infrared (IR) camera monitoring. Setup error was defined as displacement of the skull in the stereotactic space upon setup as noted on pretreatment CBCT compared to its position in the stereotactic space defined by planning MRI for frame patients and defined as skull displacement on planning CBCT compared to its position on pretreatment CBCT for mask patients. For frame patients, the intrafractionation motion was measured by comparing pretreatment and posttreatment CBCT. For mask patients, the intrafractionation motion was evaluated by comparing pretreatment CBCT and additional CBCT obtained during the treatment. The translational and rotational errors were recorded.RESULTSData were collected from 77 patients undergoing SRS with the GK Icon. Sixty-four patients underwent frame fixation, with pre- and posttreatment CBCT studies obtained. Thirteen patients were treated using mask fixation to deliver a total of 33 treatment fractions. Mean setup and intrafraction translational and rotation errors were small for both fixation systems, within 1 mm and 1° in all axes. Yet mask fixation demonstrated significantly larger intrafraction errors than frame fixation. Also, there was greater variability in both setup and intrafraction errors for mask fixation than for frame fixation in all translational and rotational directions. Whether the GK treatment was for metastasis or nonmetastasis did not influence motion uncertainties between the two fixation types. Additionally, monitoring IR-based intrafraction motion for mask fixation—i.e., the number of treatment stoppages due to reaching the IR displacement threshold—correlated with increasing treatment time.CONCLUSIONSCompared to frame-based fixation, mask-based fixation demonstrated larger motion variations. The variability in motion error associated with mask fixation must be taken into account when planning for small lesions or lesions near critical structures.
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Affiliation(s)
| | - Ke Nie
- 2Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey
| | - Joseph Weiner
- 2Department of Radiation Oncology, Rutgers Cancer Institute of New Jersey, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey
| | - Eric Hargreaves
- 1Department of Neurological Surgery, Rutgers University; and
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Li W, Cho YB, Ansell S, Laperriere N, Ménard C, Millar BA, Zadeh G, Kongkham P, Bernstein M, Jaffray DA, Chung C. The Use of Cone Beam Computed Tomography for Image Guided Gamma Knife Stereotactic Radiosurgery: Initial Clinical Evaluation. Int J Radiat Oncol Biol Phys 2016; 96:214-20. [PMID: 27511857 DOI: 10.1016/j.ijrobp.2016.04.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 03/26/2016] [Accepted: 04/11/2016] [Indexed: 11/28/2022]
Abstract
PURPOSE The present study used cone beam computed tomography (CBCT) to measure the inter- and intrafraction uncertainties for intracranial stereotactic radiosurgery (SRS) using the Leksell Gamma Knife (GK). METHODS AND MATERIALS Using a novel CBCT system adapted to the GK radiosurgery treatment unit, CBCT images were acquired immediately before and after treatment for each treatment session within the context of a research ethics board-approved prospective clinical trial. Patients were immobilized in the Leksell coordinate frame (LCF) for both volumetric CBCT imaging and GK-SRS delivery. The relative displacement of the patient's skull to the stereotactic reference (interfraction motion) was measured for each CBCT scan. Differences between the pre- and post-treatment CBCT scans were used to determine the intrafraction motion. RESULTS We analyzed 20 pre- and 17 post-treatment CBCT scans in 20 LCF patients treated with SRS. The mean translational pretreatment setup error ± standard deviation in the left-right, anteroposterior, and craniocaudal directions was -0.19 ± 0.32, 0.06 ± 0.27, and -0.23 ± 0.2 mm, with a maximum of -0.74, -0.53, and -0.68 mm, respectively. After an average time between the pre- and post-treatment CBCT scans of 82 minutes (range 27-170), the mean intrafraction error ± standard deviation for the LCF was -0.03 ± 0.05, -0.03 ± 0.18, and -0.03 ± 0.12 mm in the left-right, anteroposterior, and craniocaudual direction, respectively. CONCLUSIONS Using CBCT on a prototype image guided GK Perfexion unit, we were able to measure the inter- and intrafraction positional changes for GK-SRS using the invasive frame. In the era of image guided radiation therapy, the use of CBCT image guidance for both frame- and non-frame-based immobilization systems could serve as a useful quality assurance tool. Our preliminary measurements can guide the application of achievable thresholds for inter- and intrafraction discrepancy when moving to a frameless approach.
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Affiliation(s)
- Winnie Li
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Young-Bin Cho
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Steve Ansell
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada
| | - Normand Laperriere
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Cynthia Ménard
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Barbara-Ann Millar
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Gelareh Zadeh
- Division of Neurosurgery, University of Toronto University Health Network, Toronto Western Hospital, Toronto, Ontario, Canada; Macfeeters-Hamilton Centre for Neuro-oncology, Ontario Cancer Institute, Toronto, Ontario, Canada
| | - Paul Kongkham
- Division of Neurosurgery, University of Toronto University Health Network, Toronto Western Hospital, Toronto, Ontario, Canada
| | - Mark Bernstein
- Division of Neurosurgery, University of Toronto University Health Network, Toronto Western Hospital, Toronto, Ontario, Canada
| | - David A Jaffray
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Caroline Chung
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
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Image guidance in radiation therapy: techniques and applications. Radiol Res Pract 2014; 2014:705604. [PMID: 25587445 PMCID: PMC4281403 DOI: 10.1155/2014/705604] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 10/28/2014] [Indexed: 12/14/2022] Open
Abstract
In modern day radiotherapy, the emphasis on reduction on volume exposed to high radiotherapy doses, improving treatment precision as well as reducing radiation-related normal tissue toxicity has increased, and thus there is greater importance given to accurate position verification and correction before delivering radiotherapy. At present, several techniques that accomplish these goals impeccably have been developed, though all of them have their limitations. There is no single method available that eliminates treatment-related uncertainties without considerably adding to the cost. However, delivering “high precision radiotherapy” without periodic image guidance would do more harm than treating large volumes to compensate for setup errors. In the present review, we discuss the concept of image guidance in radiotherapy, the current techniques available, and their expected benefits and pitfalls.
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Torrens M, Chung C, Chung HT, Hanssens P, Jaffray D, Kemeny A, Larson D, Levivier M, Lindquist C, Lippitz B, Novotny J, Paddick I, Prasad D, Yu CP. Standardization of terminology in stereotactic radiosurgery: Report from the Standardization Committee of the International Leksell Gamma Knife Society. J Neurosurg 2014; 121 Suppl:2-15. [DOI: 10.3171/2014.7.gks141199] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
ObjectThis report has been prepared to ensure more uniform reporting of Gamma Knife radiosurgery treatment parameters by identifying areas of controversy, confusion, or imprecision in terminology and recommending standards.MethodsSeveral working group discussions supplemented by clarification via email allowed the elaboration of a series of provisional recommendations. These were also discussed in open session at the 16th International Leksell Gamma Knife Society Meeting in Sydney, Australia, in March 2012 and approved subject to certain revisions and the performance of an Internet vote for approval from the whole Society. This ballot was undertaken in September 2012.ResultsThe recommendations in relation to volumes are that Gross Target Volume (GTV) should replace Target Volume (TV); Prescription Isodose Volume (PIV) should generally be used; the term Treated Target Volume (TTV) should replace TVPIV, GTV in PIV, and so forth; and the Volume of Accepted Tolerance Dose (VATD) should be used in place of irradiated volume. For dose prescription and measurement, the prescription dose should be supplemented by the Absorbed Dose, or DV% (for example, D95%), the maximum and minimum dose should be related to a specific tissue volume (for example, D2% or preferably D1 mm3), and the median dose (D50%) should be recorded routinely. The Integral Dose becomes the Total Absorbed Energy (TAE). In the assessment of planning quality, the use of the Target Coverage Ratio (TTV/ GTV), Paddick Conformity Index (PCI = TTV2/[GTV · PIV]), New Conformity Index (NCI = [GTV · PIV]/TTV2), Selectivity Index (TTV/PIV), Homogeneity Index (HI = [D2% –D98%]/D50%), and Gradient Index (GI = PIV0.5/PIV) are reemphasized. In relation to the dose to Organs at Risk (OARs), the emphasis is on dose volume recording of the VATD or the dose/volume limit (for example, V10) in most cases, with the additional use of a Maximum Dose to a small volume (such as 1 mm3) and/or a Point Dose and Mean Point Dose in certain circumstances, particularly when referring to serial organs. The recommendations were accepted by the International Leksell Gamma Knife Society by a vote of 92% to 8%.ConclusionsAn agreed-upon and uniform terminology and subsequent standardization of certain methods and procedures will advance the clinical science of stereotactic radiosurgery.
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Affiliation(s)
- Michael Torrens
- 1Department of Neurosurgery, Hygeia Hospital, Athens, Greece
| | - Caroline Chung
- 2Department of Radiation Oncology, University of Toronto, Ontario, Canada
| | - Hyun-Tai Chung
- 3Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Patrick Hanssens
- 4Gamma Knife Centre, St. Elizabeth Hospital, Tilburg, The Netherlands
| | - David Jaffray
- 2Department of Radiation Oncology, University of Toronto, Ontario, Canada
| | - Andras Kemeny
- 5National Centre for Stereotactic Radiosurgery, Royal Hallamshire Hospital, Sheffield, United Kingdom
| | - David Larson
- 6Department of Radiation Oncology, University of California, San Francisco, California
| | - Marc Levivier
- 7Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | | | - Bodo Lippitz
- 8Gamma Knife Department, Cromwell Hospital, London, United Kingdom
| | - Josef Novotny
- 9Department of Medical Physics, Na Homolce Hospital, Prague, Czech Republic
| | - Ian Paddick
- 8Gamma Knife Department, Cromwell Hospital, London, United Kingdom
| | - Dheerendra Prasad
- 10Departments of Radiation Medicine and Neurosurgery, Roswell Park Cancer Institute, Buffalo, New York; and
| | - Chung Ping Yu
- 11Gamma Knife, Canossa Hospital, Hong Kong, People's Republic of China
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