1
|
Li H, Mayr NA, Griffin RJ, Zhang H, Pokhrel D, Grams M, Penagaricano J, Chang S, Spraker MB, Kavanaugh J, Lin L, Sheikh K, Mossahebi S, Simone CB, Roberge D, Snider JW, Sabouri P, Molineu A, Xiao Y, Benedict SH. Overview and Recommendations for Prospective Multi-institutional Spatially Fractionated Radiation Therapy Clinical Trials. Int J Radiat Oncol Biol Phys 2024; 119:737-749. [PMID: 38110104 PMCID: PMC11162930 DOI: 10.1016/j.ijrobp.2023.12.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 10/30/2023] [Accepted: 12/09/2023] [Indexed: 12/20/2023]
Abstract
PURPOSE The highly heterogeneous dose delivery of spatially fractionated radiation therapy (SFRT) is a profound departure from standard radiation planning and reporting approaches. Early SFRT studies have shown excellent clinical outcomes. However, prospective multi-institutional clinical trials of SFRT are still lacking. This NRG Oncology/American Association of Physicists in Medicine working group consensus aimed to develop recommendations on dosimetric planning, delivery, and SFRT dose reporting to address this current obstacle toward the design of SFRT clinical trials. METHODS AND MATERIALS Working groups consisting of radiation oncologists, radiobiologists, and medical physicists with expertise in SFRT were formed in NRG Oncology and the American Association of Physicists in Medicine to investigate the needs and barriers in SFRT clinical trials. RESULTS Upon reviewing the SFRT technologies and methods, this group identified challenges in several areas, including the availability of SFRT, the lack of treatment planning system support for SFRT, the lack of guidance in the physics and dosimetry of SFRT, the approximated radiobiological modeling of SFRT, and the prescription and combination of SFRT with conventional radiation therapy. CONCLUSIONS Recognizing these challenges, the group further recommended several areas of improvement for the application of SFRT in cancer treatment, including the creation of clinical practice guidance documents, the improvement of treatment planning system support, the generation of treatment planning and dosimetric index reporting templates, and the development of better radiobiological models through preclinical studies and through conducting multi-institution clinical trials.
Collapse
Affiliation(s)
- Heng Li
- Department of Radiation Oncology, John Hopkins University, Baltimore, Maryland.
| | - Nina A Mayr
- College of Human Medicine, Michigan State University, East Lansing, Michigan
| | - Robert J Griffin
- Department of Radiation Oncology, University of Arkansas for Medical Science, Little Rock, Arkansas
| | - Hualin Zhang
- Department of Radiation Oncology, University of Southern California, Los Angeles, California
| | - Damodar Pokhrel
- Department of Radiation Medicine, University of Kentucky, Lexington, Kentucky
| | - Michael Grams
- Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota
| | - Jose Penagaricano
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida
| | - Sha Chang
- Department of Radiation Oncology, University of North Carolina, Chapel Hill, North Carolina
| | | | - James Kavanaugh
- Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota
| | - Liyong Lin
- Department of Radiation Oncology, Emory University, Atlanta, Georgia
| | - Khadija Sheikh
- Department of Radiation Oncology, John Hopkins University, Baltimore, Maryland
| | - Sina Mossahebi
- Department of Radiation Oncology, University of Maryland, Baltimore, Maryland
| | - Charles B Simone
- Department of Radiation Oncology, New York Proton Center, New York, New York
| | - David Roberge
- Department of Radiation Oncology, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, Québec, Canada
| | - James W Snider
- South Florida Proton Therapy Institute, 5280 Linton Blvd, Delray Beach, Florida
| | - Pouya Sabouri
- Department of Radiation Oncology, University of Arkansas for Medical Science, Little Rock, Arkansas
| | - Andrea Molineu
- Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Ying Xiao
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Stanley H Benedict
- Department of Radiation Oncology, University of California, Davis, Sacramento, California
| |
Collapse
|
2
|
At B, Velayudham R. Assessing dosimetric advancements in spatially fractionated radiotherapy: From grids to lattices. Med Dosim 2024:S0958-3947(23)00116-4. [PMID: 38290896 DOI: 10.1016/j.meddos.2023.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 12/05/2023] [Accepted: 12/21/2023] [Indexed: 02/01/2024]
Abstract
Spatially fractionated radiotherapy (SFRT) techniques have undergone transformative evolution, encompassing physical GRID therapy, MLC-based grids, virtual TOMO GRIDs, and 3-dimensional high-dose lattices. Historical roots trace back to Alban Köhler's pioneering Spatially fractionated grid therapy (SFGRT), utilizing physical grids for dose modulation. Technological innovations introduced multi-leaf collimators (MLCs), enabling adaptable spatial fractionation and a shift to the broader term "SFRT." Physics and dosimetry-based studies have demonstrated the feasibility of computerized treatment planning and identified the potential to minimize the peripheral dose while using such high-dose therapy. Meanwhile, 3-dimensional high-dose lattices showed enhanced precision. The meticulous placement of high-dose volumetric spheres enables a reduction in the volume of high-dose spills. Advancements in 3-dimensional lattices through intensity-modulated radiotherapy and volumetric modulated arc therapy (VMAT) techniques offer enhanced therapeutic options. A database of SFRT studies identified 723 articles. This review shows the trajectory of SFRT from traditional grids to MLC-based approaches, virtual TOMO GRIDs, and innovative 3-dimensional lattices. Technological innovations, dosimetric advancements, and clinical feasibility have underscored the continual progress in refining spatially fractionated radiotherapy. The integration of MLCs and lattice techniques has demonstrated improved therapeutic outcomes, solidifying their relevance in modern radiation therapy protocols. Research has yet to reveal a clear correlation between treatment outcomes and dosimetric parameters. Additional investigations are necessary to assess the impact of various dosimetric parameters, such as EUD, peak-to-valley ratio (PVDR), D5%, D10%, D20%, D90%, etc., on the effectiveness of treatments.
Collapse
Affiliation(s)
- Bhagyalakshmi At
- Vellore Institute of Technology, Vellore Campus, Katpadi, Tamil Nadu 500036, India; American Oncology Institute at Baby Memorial Hospital, Kozhikode, Kerala 673004, India
| | | |
Collapse
|
3
|
Ertan F, Yeginer M, Zorlu F. Dosimetric Performance Evaluation of MLC-based and Cone-based 3D Spatially Fractionated LATTICE Radiotherapy. Radiat Res 2023; 199:161-169. [PMID: 36580642 DOI: 10.1667/rade-22-00020.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 11/11/2022] [Indexed: 12/31/2022]
Abstract
This study aims to dosimetrically compare multi-leaf collimator (MLC)-based and cone-based 3D LATTICE radiotherapy (LRT) plans. Valley-peak ratios were evaluated using seven different 3D LATTICE designs. Target volumes of 8 cm and 12 cm were defined on the RANDO phantom. Valley-peak dose patterns were obtained by creating high-dose vertices in the target volumes. By changing the vertex diameter, vertices separation, and volume ratio, seven different LATTICE designs were generated. Treatment plans were implemented using CyberKnife and Varian RapidArc. Thermoluminescent dosimeter (TLD), EBT3 films, and electronic portal-imaging device (EPID) were employed for dosimetric treatment verification, and measured doses were compared to calculated doses. By changing the vertex diameter and vertices separation, the valley-peak ratio was exhibited little difference between the two systems. By changing the vertex diameter and volume ratio, the valley-peak ratio was observed nearly the same for the two systems. The film, TLD, and EPID dosimetry showed good agreement between the calculated and measured doses. Based on the results, we concluded that although smaller valley-peak ratios were obtained with cone-based plans, the dose-volume histograms were comparable in both systems. Also, when we evaluated the treatment duration, the MLC-based plans were more appropriate to apply the treatment in a single fraction.
Collapse
Affiliation(s)
- Ferihan Ertan
- Department of Radiation Oncology, Faculty of Medicine, Hacettepe University, 06100, Ankara, Turkey.,Dr. Abdurrahman Yurtaslan Ankara Oncology Teaching and Research Hospital, 06200, Ankara, Turkey
| | - Mete Yeginer
- Department of Radiation Oncology, Faculty of Medicine, Hacettepe University, 06100, Ankara, Turkey
| | - Faruk Zorlu
- Department of Radiation Oncology, Faculty of Medicine, Hacettepe University, 06100, Ankara, Turkey
| |
Collapse
|
4
|
Moghaddasi L, Reid P, Bezak E, Marcu LG. Radiobiological and Treatment-Related Aspects of Spatially Fractionated Radiotherapy. Int J Mol Sci 2022; 23:3366. [PMID: 35328787 PMCID: PMC8954016 DOI: 10.3390/ijms23063366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 03/13/2022] [Accepted: 03/17/2022] [Indexed: 11/17/2022] Open
Abstract
The continuously evolving field of radiotherapy aims to devise and implement techniques that allow for greater tumour control and better sparing of critical organs. Investigations into the complexity of tumour radiobiology confirmed the high heterogeneity of tumours as being responsible for the often poor treatment outcome. Hypoxic subvolumes, a subpopulation of cancer stem cells, as well as the inherent or acquired radioresistance define tumour aggressiveness and metastatic potential, which remain a therapeutic challenge. Non-conventional irradiation techniques, such as spatially fractionated radiotherapy, have been developed to tackle some of these challenges and to offer a high therapeutic index when treating radioresistant tumours. The goal of this article was to highlight the current knowledge on the molecular and radiobiological mechanisms behind spatially fractionated radiotherapy and to present the up-to-date preclinical and clinical evidence towards the therapeutic potential of this technique involving both photon and proton beams.
Collapse
Affiliation(s)
- Leyla Moghaddasi
- Department of Medical Physics, Austin Health, Ballarat, VIC 3350, Australia;
- School of Physical Sciences, University of Adelaide, Adelaide, SA 5001, Australia;
| | - Paul Reid
- Radiation Health, Environment Protection Authority, Adelaide, SA 5000, Australia;
| | - Eva Bezak
- School of Physical Sciences, University of Adelaide, Adelaide, SA 5001, Australia;
- Cancer Research Institute, University of South Australia, Adelaide, SA 5001, Australia
| | - Loredana G. Marcu
- Cancer Research Institute, University of South Australia, Adelaide, SA 5001, Australia
- Faculty of Informatics and Science, University of Oradea, 1 Universitatii Str., 410087 Oradea, Romania
| |
Collapse
|
5
|
Zhang H, Wu X, Zhang X, Chang SX, Megooni A, Donnelly ED, Ahmed MM, Griffin RJ, Welsh JS, Simone CB, Mayr NA. Photon GRID Radiation Therapy: A Physics and Dosimetry White Paper from the Radiosurgery Society (RSS) GRID/LATTICE, Microbeam and FLASH Radiotherapy Working Group. Radiat Res 2021; 194:665-677. [PMID: 33348375 DOI: 10.1667/rade-20-00047.1] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 09/18/2020] [Indexed: 11/03/2022]
Abstract
The limits of radiation tolerance, which often deter the use of large doses, have been a major challenge to the treatment of bulky primary and metastatic cancers. A novel technique using spatial modulation of megavoltage therapy beams, commonly referred to as spatially fractionated radiation therapy (SFRT) (e.g., GRID radiation therapy), which purposefully maintains a high degree of dose heterogeneity across the treated tumor volume, has shown promise in clinical studies as a method to improve treatment response of advanced, bulky tumors. Compared to conventional uniform-dose radiotherapy, the complexities of megavoltage GRID therapy include its highly heterogeneous dose distribution, very high prescription doses, and the overall lack of experience among physicists and clinicians. Since only a few centers have used GRID radiation therapy in the clinic, wide and effective use of this technique has been hindered. To date, the mechanisms underlying the observed high tumor response and low toxicity are still not well understood. To advance SFRT technology and planning, the Physics Working Group of the Radiosurgery Society (RSS) GRID/Lattice, Microbeam and Flash Radiotherapy Working Groups, was established after an RSS-NCI Workshop. One of the goals of the Physics Working Group was to develop consensus recommendations to standardize dose prescription, treatment planning approach, response modeling and dose reporting in GRID therapy. The objective of this report is to present the results of the Physics Working Group's consensus that includes recommendations on GRID therapy as an SFRT technology, field dosimetric properties, techniques for generating GRID fields, the GRID therapy planning methods, documentation metrics and clinical practice recommendations. Such understanding is essential for clinical patient care, effective comparisons of outcome results, and for the design of rigorous clinical trials in the area of SFRT. The results of well-conducted GRID radiation therapy studies have the potential to advance the clinical management of bulky and advanced tumors by providing improved treatment response, and to further develop our current radiobiology models and parameters of radiation therapy design.
Collapse
Affiliation(s)
- Hualin Zhang
- Department of Radiation Oncology, Northwestern Memorial Hospital, Chicago, Illinois 60611
| | - Xiaodong Wu
- Excecutive Medical Physics Associates and Biophysics Research Institute of America, Miami, Florida 33179
| | - Xin Zhang
- Department of Radiation Oncology, Boston Medical Center, Boston, Massachusetts 02118
| | - Sha X Chang
- Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27516
| | - Ali Megooni
- Department of Radiation Therapy, Comprehensive Cancer Center of Nevada, Las Vegas, Nevada 86169
| | - Eric D Donnelly
- Department of Radiation Oncology, Northwestern Memorial Hospital, Chicago, Illinois 60611
| | - Mansoor M Ahmed
- Division of Cancer Treatment and Diagnosis, Rockville, Maryland 20892
| | - Robert J Griffin
- University of Arkansas for Medical Sciences, Department of Radiation Oncology, Little Rock, Arkansas
| | - James S Welsh
- Loyola University Chicago, Edward Hines Jr. VA Hospital, Stritch School of Medicine, Department of Radiation Oncology, Maywood, Illinois 60153
| | - Charles B Simone
- New York Proton Center, Department of Radiation Oncology, New York, New York 10035
| | - Nina A Mayr
- Department of Radiation Oncology, University of Washington Medical Center, Seattle, Washington 98195
| |
Collapse
|
6
|
Choi JI, Daniels J, Cohen D, Li Y, Ha CS, Eng TY. Clinical Outcomes of Spatially Fractionated GRID Radiotherapy in the Treatment of Bulky Tumors of the Head and Neck. Cureus 2019; 11:e4637. [PMID: 31312563 PMCID: PMC6623998 DOI: 10.7759/cureus.4637] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Objectives The clinical outcomes of patients treated with spatially fractionated GRID radiotherapy (SFGRT) for bulky tumors of the head and neck at a single institution were evaluated retrospectively. Endpoints of interest included tumor response, symptom improvement, treatment tolerance, and adverse events. Methods Institutional review board approval was obtained prior to study initiation. The institutional database was queried for patients with tumors of the head and neck treated with SFGRT between August 2007 and April 2015. Medical records of identified patients were reviewed for treatment details and clinical endpoints of interest. SFGRT was delivered in one fraction of 15 gray (Gy) or 20 Gy; 6 megavolt (MV) or 18 MV photon beams were passed through a multileaf collimator (MLC)-based or brass GRID template. All patients had a planned course of conventionally-fractionated external beam radiotherapy (EBRT) to begin on the day following SFGRT delivery. Results Twenty-one consecutive patients meeting study criteria were identified. The most common tumor histology was squamous cell carcinoma. Median patient age was 59 years (range 13 - 83 years); median maximum tumor dimension was 9.5 centimeters (cm) (range 5.0 - 25.0 cm). Fifteen patients (71.4%) completed their full course of EBRT. Twelve patients were treated with palliative intent for local tumor symptoms, of which 54.5% experienced some degree of symptom improvement. Of nine patients treated with curative intent, 44.4% achieved a clinical complete response (CR). Concurrent chemotherapy was administered in 12 patients, with all patients being treated having definitively received chemotherapy. Radiation Therapy Oncology Group (RTOG) grade three or higher skin toxicity occurred in five patients; no grade five events were reported. Conclusions Our institutional experience suggests that SFGRT is a feasible treatment option for the palliative or definitive management of large tumors of the head and neck. In combination with EBRT, SFGRT can provide timely symptom management and improve patient quality of life in the palliative setting. In the definitive setting, the addition of chemotherapy to SFGRT and EBRT can result in an excellent clinical response. Treatment toxicity was found to be within an acceptable range. When considering SFGRT for patients with these challenging presentations, careful patient selection is needed to identify those who will likely tolerate a full course of EBRT following SFGRT, as these patients are most likely to receive maximal benefit from SFGRT treatment. More data on the feasibility and efficacy of this radiation modality will be helpful for continued optimization of SFGRT delivery and patient selection.
Collapse
Affiliation(s)
| | - Janeen Daniels
- Radiation Oncology, Eastern Maine Medical Center, Brewer, USA
| | - Dane Cohen
- Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, USA
| | - Ying Li
- Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, USA
| | - Chul S Ha
- Radiation Oncology, University of Texas Health Science Center at San Antonio, San Antonio, USA
| | - Tony Y Eng
- Radiation Oncology, Emory University School of Medicine, Atlanta, USA
| |
Collapse
|
7
|
Gao M, Mohiuddin MM, Hartsell WF, Pankuch M. Spatially fractionated (GRID) radiation therapy using proton pencil beam scanning (PBS): Feasibility study and clinical implementation. Med Phys 2018; 45:1645-1653. [PMID: 29431867 DOI: 10.1002/mp.12807] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 01/10/2018] [Accepted: 01/25/2018] [Indexed: 11/09/2022] Open
Abstract
PURPOSE GRID therapy is an effective treatment for bulky tumors. Linear accelerator (Linac)-produced photon beams collimated through blocks or multileaf collimators (MLCs) are the most common methods used to deliver this therapy. Utilizing the newest proton delivery method of pencil beam scanning (PBS) can further improve the efficacy of GRID therapy. In this study, we developed a method of delivering GRID therapy using proton PBS, evaluated the dosimetry of this novel technique and applied this method in two clinical cases. MATERIALS/METHODS In the feasibility study phase, a single PBS proton beam was optimized to heterogeneously irradiate a shallow 20 × 20 × 12 cm3 target volume centered at a 6 cm depth in a water phantom. The beam was constrained to have an identical spot pattern in all layers, creating a "beamlet" at each spot position. Another GRID treatment using PBS was also performed on a deep 15 × 15 × 8 cm3 target volume centered at a 14 cm depth in a water phantom. Dosimetric parameters of both PBS dose distributions were compared with typical photon GRID dose distributions. In the next phase, four patients have been treated at our center with this proton GRID technique. The planning, dosimetry, and measurements for two representative patients are reported. RESULTS For the shallow phantom target, the depth-dose curve of the PBS plan was uniform within the target (variation < 5%) and dropped quickly beyond the target (50% at 12.9 cm and 0.5% at 14 cm). The lateral profiles of the PBS plan were comparable to those of photon GRID in terms of valley-to-peak ratios. For the deep phantom target, the PBS plan provided smaller valley-to-peak ratios than the photon GRID technique. Pretreatment dose verification QA showed close agreement between the measurements and the plan (pass rate > 95% with a gamma index criterion of 3%/3 mm). Patients tolerated the treatment well without significant skin toxicity (radiation dermatitis grade ≤ 1). CONCLUSIONS Proton GRID therapy using a PBS delivery method was successfully developed and implemented clinically. Proton GRID therapy offers many advantages over photon GRID techniques. The use of protons provides a more uniform beamlet dose within the tumor and spares normal tissues located beyond the tumor. This new PBS method will also reduce the dose to proximal organs when treating a deep-seated tumor.
Collapse
Affiliation(s)
- M Gao
- Northwestern Medicine Chicago Proton Center, Warrenville, IL, 60555, USA
| | - M M Mohiuddin
- Advocate Lutheran General Hospital, Park Ridge, IL, 60068, USA.,Radiation Oncology Consultants, Ltd., Oak Brook, IL, 60523, USA
| | - W F Hartsell
- Northwestern Medicine Chicago Proton Center, Warrenville, IL, 60555, USA.,Radiation Oncology Consultants, Ltd., Oak Brook, IL, 60523, USA
| | - M Pankuch
- Northwestern Medicine Chicago Proton Center, Warrenville, IL, 60555, USA
| |
Collapse
|
8
|
Nobah A, Mohiuddin M, Devic S, Moftah B. Effective spatially fractionated GRID radiation treatment planning for a passive grid block. Br J Radiol 2015; 88:20140363. [PMID: 25382164 PMCID: PMC4277376 DOI: 10.1259/bjr.20140363] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 10/29/2014] [Accepted: 11/06/2014] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE To commission a grid block for spatially fractionated grid radiation therapy (SFGRT) treatments and describe its clinical implementation and verification through the record and verify (R&V) system. METHODS SFGRT was developed as a treatment modality for bulky tumours that cannot be easily controlled with conventionally fractionated radiation. Treatment is delivered in the form of open-closed areas. Currently, SFGRT is performed by either using a commercially available grid block or a multileaf collimator (MLC) of a linear accelerator. In this work, 6-MV photon beam was used to study dosimetric characteristics of the grid block. We inserted the grid block into a commercially available treatment planning system (TPS), and the feasibility of delivering such treatment plans on a linear accelerator using a R&V system was verified. Dose measurements were performed using a miniature PinPoint(TM) ion chamber (PTW, Freiburg, Germany) in a water phantom and radiochromic film within solid water slabs. PinPoint ion chamber was used to measure the output factors, percentage depth dose (PDD) curves and beam profiles at two depths, depth of maximum dose (zmax) and 10 cm. Film sheets were used to measure dose profiles at zmax and 10-cm depth. RESULTS The largest observed percentage difference between output factors for the grid block technique calculated by the TPS and measured with the PinPoint ion chamber was 3.6% for the 5 × 5-cm(2) field size. Relatively significant discrepancies between measured and calculated PDD values appear only in the build-up region, which was found to amount to <4%, while a good agreement (differences <2%) at depths beyond zmax was observed. Dose verification comparisons performed between calculated and measured dose distributions were in clinically acceptable agreements. When comparing the MLC-based with the grid block technique, the advantage of treating large tumours with a single field reduces treatment time by at least 3-5 times, having significant impact on patient throughput. CONCLUSION The proposed method supports and helps to standardize the clinical implementation of the grid block in a safer and more accurate way. ADVANCES IN KNOWLEDGE This work describes the method to implement treatment planning for the grid block technique in radiotherapy departments.
Collapse
Affiliation(s)
- A Nobah
- 1 Biomedical Physics Department, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | | | | | | |
Collapse
|
9
|
Nonato de Oliveira L, de Almeida A, Caldas LV. Measuring output factors and beam profiles formed by multileaf collimators using Fricke gel dosimeter. Phys Med 2014; 30:854-7. [DOI: 10.1016/j.ejmp.2014.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 03/12/2014] [Accepted: 04/01/2014] [Indexed: 11/15/2022] Open
|
10
|
Almendral P, Mancha PJ, Roberto D. Feasibility of a simple method of hybrid collimation for megavoltage grid therapy. Med Phys 2013; 40:051712. [PMID: 23635260 DOI: 10.1118/1.4801902] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and are not practical with some multileaf collimators. This work studies the feasibility of a hybrid collimation system for grid therapy that does not require multiple segments and can be easily implemented with widely available technical means. METHODS The authors have developed a system to generate a grid of beamlets by the simultaneous use of two perpendicular sets of equally spaced leaves that project stripe patterns in orthogonal directions. One of them is generated with the multileaf collimator integrated in the accelerator and the other with an in-house made collimator constructed with a low melting point alloy commonly available at radiation oncology departments. The characteristics of the grid fields for 6 and 18 MV have been studied with a shielded diode, an unshielded diode, and radiochromic film. RESULTS The grid obtained with the hybrid collimation is similar to some of the grids used clinically with respect to the beamlet size (about 1 cm) and the percentage of open beam (1/4 of the total field). The grid fields are less penetrating than the open fields of the same energy. Depending on the depth and the direction of the profiles (diagonal or along the principal axes), the measured valley-to-peak dose ratios range from 5% to 16% for 6 MV and from 9% to 20% for 18 MV. All the detectors yield similar results in the measurement of profiles and percent depth dose, but the shielded diode seems to overestimate the output factors. CONCLUSIONS The combination of two stripe pattern collimators in orthogonal directions is a feasible method to obtain two-dimensional arrays of beamlets and has potential usefulness as an efficient way to deliver grid therapy. The implementation of this method is technically simpler than the construction of a conventional grid block.
Collapse
Affiliation(s)
- Pedro Almendral
- Servicio de Protección Radiológica y Radiofísica Hospitalaria, Hospital Infanta Cristina, 06080 Badajoz, Spain.
| | | | | |
Collapse
|
11
|
Buckey C, Stathakis S, Cashon K, Gutierrez A, Esquivel C, Shi C, Papanikolaou N. Evaluation of a commercially-available block for spatially fractionated radiation therapy. J Appl Clin Med Phys 2010; 11:3163. [PMID: 20717082 PMCID: PMC5720442 DOI: 10.1120/jacmp.v11i3.3163] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 01/14/2010] [Accepted: 02/16/2010] [Indexed: 11/23/2022] Open
Abstract
In this paper, we present the dosimetric characteristics of a commercially‐produced universal GRID block for spatially fractioned radiation therapy. The dosimetric properties of the GRID block were evaluated. Ionization chamber and film measurements using both Kodak EDR2 and Gafchromic EBT film were performed in a solid water phantom to determine the relative output of the GRID block as well as its spatial dosimetric characteristics. The surface dose under the block and at the openings was measured using ultra thin TLDs. After introducing the GRID block into the treatment planning system, a treatment plan was created using the GRID block and also by creating a GRID pattern using the multi‐leaf collimator. The percent depth doses measured with film showed that there is a shift of the dmax towards shallower depths for both energies (6 MV and 18 MV) under investigation. It was observed that the skin dose at the GRID openings was higher than the corresponding open field by a factor as high as 50% for both photon energies. The profiles showed the transmission under the block was in the order of 15–20% for 6 MV and 30% for 18 MV. The MUs calculated for a real patient using the block were about 80% less than the corresponding MUs for the same plan using the multileaf collimator to define the GRID. Based on this investigation, this brass GRID compensator is a viable alternative to other solid compensators or MLC‐based fields currently in use. Its ease of creation and use give it decided advantages. Its ability to be created once and used for multiple patients (by varying the collimation of the linear accelerator jaws) makes it attractive from a cost perspective. We believe this compensator can be put to clinical use, and will allow more centers to offer GRID therapy to their patients. PACS number: 87.53.Mr
Collapse
Affiliation(s)
- Courtney Buckey
- Departments of Radiology and Radiation Oncology, Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | | | | | | | | | | | | |
Collapse
|