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Abtahi SMM, Habibi F. Investigation of the beam quality and dose rate dependence of PAKAG polymer gel dosimeter in optical readout technique. Biomed Phys Eng Express 2024; 10:055041. [PMID: 39151446 DOI: 10.1088/2057-1976/ad7032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Accepted: 08/16/2024] [Indexed: 08/19/2024]
Abstract
This study aims to evaluate the optical response dependence of the PAKAG polymer gel dosimeter on photon energy and dose rate. The produced gel dosimeters were irradiated using a Varian CL 21EX medical linear accelerator with delivered doses of 0, 2, 4, 6, 8, and 10 Gy. To examine the response dependence on the delivered dose rate, dose rates of 50, 100, 200, and 350 cGy min-1were investigated. Additionally, two incident beam qualities of 6 and 18 MV were examined to study the response dependence on the incident beam energy. The irradiated polymer gel dosimeters were readout using a UV-vis spectrophotometer in the 300 to 800 nm scan range. The results reveal that a wide variation in dose rate (50-350 cGy.min-1) influences the absorbance-dose response and the sensitivity of PAKAG gel. However, smaller variations did not show a significant effect on the response. Furthermore, the response changed insignificantly with beam quality for investigated energies. It was concluded that the optical reading response of the PAKAG polymer gel dosimeter is satisfactorily independent of external parameters, including dose rate and incident beam quality.
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Affiliation(s)
| | - Fatemeh Habibi
- Department of Physics, Imam Khomeini International University, Qazvin, 3414896818, Iran
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Kudrevicius L, Jaselskė E, Stankus G, Arslonova S, Adliene D. Post-Irradiation Behavior of Colored PVA-Based Films Containing Ag Nanoparticles as Radiation Detectors/Exposure Indicators. Gels 2024; 10:290. [PMID: 38786207 PMCID: PMC11121668 DOI: 10.3390/gels10050290] [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: 03/27/2024] [Revised: 04/18/2024] [Accepted: 04/22/2024] [Indexed: 05/25/2024] Open
Abstract
Ionizing radiation covers a broad spectrum of applications. Since radioactive/radiation pollution is directly related to radiation risk, radiation levels should be strictly controlled. Different detection methods can be applied for radiation registration and monitoring. In this paper, radiation-induced variations in the optical properties of silver-enriched PVA-based hydrogel films with and without azo dye (Toluidine blue O, TBO, and Methyl red, MR) additives were investigated, and the feasibility of these free-standing films to serve as radiation detectors/exposure indicators was assessed. AgNO3 admixed with PVA gel was used as a source for the radiation-induced synthesis of silver nanoparticles (AgNPs) in irradiated gel films. Three types of sensors were prepared: silver-enriched PVA films containing a small amount of glycerol (AgPVAGly); silver-enriched PVA films with toluidine blue adducts (AgPVAGlyTBO); and silver-enriched PVA films with methyl red additives (AgPVAGlyMR). The selection of TBO and MR was based on their sensitivity to irradiation. The irradiation of the samples was performed in TrueBeam2.1 (VARIAN) using 6 MeV photons. Different doses up to 10 Gy were delivered to the films. The sensitivity of the films was assessed by analyzing the characteristic UV-Vis absorbance peaks on the same day as irradiation and 7, 30, 45, 90, and 180 days after irradiation. It was found that the addition of azo dyes led to an enhanced radiation sensitivity of the AgNPs containing films (0.6 Gy-1 for AgPVAGlyTBO and 0.4 Gy-1 for AgPVAGlyMR) irradiated with <2 Gy doses, indicating their applicability as low-dose exposure indicators. The irradiated films were less sensitive to higher doses. Almost no dose fading was detected between the 7th and 45th day after irradiation. Based on the obtained results, competing AgNP formation and color-bleaching effects in the AgPVAGly films with dye additives are discussed.
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Affiliation(s)
- Linas Kudrevicius
- Physics Department, Kaunas University of Technology, 51368 Kaunas, Lithuania;
| | - Evelina Jaselskė
- Neurosurgery Department, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania
| | - Gabrielius Stankus
- Physics Department, Kaunas University of Technology, 51368 Kaunas, Lithuania;
| | - Shirin Arslonova
- Tashkent City Branch of Republican Specialized Scientific-Practical Medical Centre of Oncology and Radiology, Boguston Str. 1, Tashkent P.O. Box 100070, Uzbekistan
| | - Diana Adliene
- Physics Department, Kaunas University of Technology, 51368 Kaunas, Lithuania;
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Průšová H, Dudáš D, Spěváček V, Průša P. Dose-response dependencies of Turnbull blue, modified Fricke, VIPET, and Presage® gel dosimeters in high-dose-rate radiation fields. RADIAT MEAS 2023. [DOI: 10.1016/j.radmeas.2023.106910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Chemical Overview of Gel Dosimetry Systems: A Comprehensive Review. Gels 2022; 8:gels8100663. [PMID: 36286165 PMCID: PMC9601373 DOI: 10.3390/gels8100663] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/10/2022] [Accepted: 10/12/2022] [Indexed: 11/17/2022] Open
Abstract
Advances in radiotherapy technology during the last 25 years have significantly improved both dose conformation to tumors and the preservation of healthy tissues, achieving almost real-time feedback by means of high-precision treatments and theranostics. Owing to this, developing high-performance systems capable of coping with the challenging requirements of modern ionizing radiation is a key issue to overcome the limitations of traditional dosimeters. In this regard, a deep understanding of the physicochemical basis of gel dosimetry, as one of the most promising tools for the evaluation of 3D high-spatial-resolution dose distributions, represents the starting point for developing new and innovative systems. This review aims to contribute thorough descriptions of the chemical processes and interactions that condition gel dosimetry outputs, often phenomenologically addressed, and particularly formulations reported since 2017.
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Krauleidis A, Adliene D, Rutkuniene Z. The Impact of Temporal Changes in Irradiated nMAG Polymer Gels on Their Applicability in Small Field Dosimetry in Radiotherapy. Gels 2022; 8:629. [PMID: 36286130 PMCID: PMC9601347 DOI: 10.3390/gels8100629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/26/2022] [Accepted: 09/27/2022] [Indexed: 11/16/2022] Open
Abstract
As advanced radiotherapy techniques progress to deliver a high absorbed dose to the target volume while minimizing the dose to normal tissues using intensity-modulated beams, arcs or stereotactic radiosurgery, new challenges occur to assure that the high treatment dose is delivered homogeneously to the tumor. Small irradiation field sizes (≤1 cm2) that tightly conform to precise target regions and allow for the deliverance of doses with a high therapeutic ratio, are of particular interest. However, the small field dosimetry using conventional dosimeters is limited by the relative large size of the detector. Radiation-sensitive polymer gels have the potential to meet this dosimetry challenge due to their almost unlimited ability in resolving three-dimensional dose distributions of any shape and makes them unique and suitable for the evaluation of dose profiles and the verification of complex doses. In this work, dose distributions in nMAG gels that have been irradiated to different doses by applying a 6 MV FFF photon beam collimated to 1 cm2, were analyzed and the dose profiles were evaluated by applying a gamma passing rate criteria of 3%/3 mm and considering different post-irradiation time intervals between the irradiation and the gels read out process. X-ray CT and NMR imaging procedures were used for the dose evaluation. It was found that the shape and uniformity of the dose profiles were changing due to post-irradiation polymerization and gelation processes, indicating time dependent growing uniformity which was better expressed for the higher delivered doses. It was estimated that in order to obtain acceptably symmetric small field dose profiles, a longer post-irradiation time is needed for getting the full scope of the polymerization as compared with the recently recommended 24 h period between irradiation and the read out processes of the dose gels. An estimated overall uncertainty (double standard deviation, 95% confidence level) of 3.66% was achieved by applying R2 measurements (NMR read out), and a 3.81-applying X-ray CT read out for 12 Gy irradiated gels 56 h post-irradiation. An increasing tendency for the uncertainty was observed with a decreasing post-irradiation time. A gamma passing rate of 90.3% was estimated for the 12 Gy irradiated gels and, 56 h post-irradiation, the X-ray CT evaluated gels as well as a gamma passing rate of 92.7% was obtained for the NMR evaluated gels applying a 3%/3 mm passing criteria.
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Affiliation(s)
| | - Diana Adliene
- Physics Department, Kaunas University of Technology, Studentu Str. 50, 51368 Kaunas, Lithuania
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Mariotti V, Gayol A, Pianoschi T, Mattea F, Vedelago J, Pérez P, Valente M, Alva-Sánchez M. Radiotherapy dosimetry parameters intercomparison among eight gel dosimeters by Monte Carlo simulation. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2021.109782] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Sunbul NB, Oraiqat I, Rosen B, Miller C, Meert C, Matuszak MM, Clarke S, Pozzi S, Moran JM, Naqa IE. Application of radiochromic gel dosimetry to commissioning of a megavoltage research linear accelerator for small-field animal irradiation studies. Med Phys 2021; 48:1404-1416. [PMID: 33378092 PMCID: PMC8917956 DOI: 10.1002/mp.14685] [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: 05/01/2020] [Revised: 11/25/2020] [Accepted: 12/17/2020] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To develop and implement an efficient and accurate commissioning procedure for small-field static beam animal irradiation studies on an MV research linear accelerator (Linatron-M9) using radiochromic gel dosimetry. MATERIALS The research linear accelerator (Linatron-M9) is a 9 MV linac with a static fixed collimator opening of 5.08 cm diameter. Lead collimators were manually placed to create smaller fields of 2 × 2 cm2 , 1 × 1 cm2 , and 0.5 × 0.5 cm2 . Relative dosimetry measurements were performed, including profiles, percent depth dose (PDD) curves, beam divergence, and relative output factors using various dosimetry tools, including a small volume ionization chamber (A14), GAFCHROMIC™ EBT3 film, and Clearview gel dosimeters. The gel dosimeter was used to provide a 3D volumetric reference of the irradiated fields. The Linatron profiles and relative output factors were extracted at a reference depth of 2 cm with the output factor measured relative to the 2 × 2 cm2 reference field. Absolute dosimetry was performed using A14 ionization chamber measurements, which were verified using a national standards laboratory remote dosimetry service. RESULTS Absolute dosimetry measurements were confirmed within 1.4% (k = 2, 95% confidence = 5%). The relative output factor of the small fields measured with films and gels agreed with a maximum relative percent error difference between the two methods of 1.1 % for the 1 × 1 cm2 field and 4.3 % for the 0.5 × 0.5 cm2 field. These relative errors were primarily due to the variability in the collimator positioning. The measured beam profiles demonstrated excellent agreement for beam size (measured as FWHM), within approximately 0.8 mm (or less). Film measurements were more accurate in the penumbra region due to the film's finer resolution compared with the gel dosimeter. Following the van Dyk criteria, the PDD values of the film and gel measurements agree within 11% in the buildup region starting from 0.5 cm depth and within 2.6 % beyond maximum dose and into the fall-off region for depths up to 5 cm. The 2D beam profile isodose lines agree within 0.5 mm in all regions for the 0.5 × 0.5 cm2 and the 1 × 1 cm2 fields and within 1 mm for the larger field of 2 × 2 cm2 . The 2D PDD curves agree within approximately 2% of the maximum in the typical therapy region (1-4 cm) for the 1 × 1 cm2 and 2 × 2 cm2 and within 5% for the 0.5 × 0.5 cm2 field. CONCLUSION This work provides a commissioning process to measure the beam characteristics of a fixed beam MV accelerator with detailed dosimetric evaluation for its implementation in megavoltage small animal irradiation studies. Radiochromic gel dosimeters are efficient small-field relative dosimetry tools providing 3D dose measurements allowing for full representation of dose, dosimeter misalignment corrections and high reproducibility with low inter-dosimeter variability. Overall, radiochromic gels are valuable for fast, full relative dosimetry commissioning in comparison to films for application in high-energy small-field animal irradiation studies.
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Affiliation(s)
- Noora Ba Sunbul
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA; Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA
| | - Ibrahim Oraiqat
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA; H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Benjamin Rosen
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA
| | - Cameron Miller
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Christopher Meert
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Martha M. Matuszak
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA; Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA
| | - Shaun Clarke
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Sara Pozzi
- Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Jean M. Moran
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA
| | - Issam El Naqa
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA; H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
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Lazzaroni S, Liosi G, Mariani M, Dondi D. An innovative Fe3+ selective ligand for Fricke-gel dosimeter. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2020.108733] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Awad SI, Moftah B, Basfer A, Almousa AA, Al Kafi M, Eyadeh MM, Rabaeh KA. 3-D Quality Assurance in CyberKnife Radiotherapy Using a Novel N-(3-methoxypropyl) Acrylamide Polymer Gel Dosimeter and Optical CT. Radiat Phys Chem Oxf Engl 1993 2019. [DOI: 10.1016/j.radphyschem.2019.03.045] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Eyadeh MM, Rabaeh KA, Hailat TF, Al-Shorman MY, Aldweri FM, Kanan HM, Awad SI. Investigation of a novel chemically cross-linked fricke-Methylthymol blue-synthetic polymer gel dosimeter with glutaraldehyde cross-linker. RADIAT MEAS 2018. [DOI: 10.1016/j.radmeas.2018.09.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Influence of magnesium chloride on the dose-response of polyacrylamide-type gel dosimeters. Radiol Phys Technol 2018; 11:375-381. [PMID: 30182145 DOI: 10.1007/s12194-018-0473-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 08/25/2018] [Accepted: 08/30/2018] [Indexed: 10/28/2022]
Abstract
We investigated the effect of magnesium chloride (MgCl2) on the nuclear magnetic resonance dose-response of polyacrylamide-type (PAGAT, NIPAM, and VIPET) gel dosimeters containing acrylamide, N-isopropylacrylamide, and N-vinylpyrrolidone as a monomer, respectively. The dose-transverse relaxation rates (1/T2 = R2) obtained from magnetic resonance imaging data revealed that a substantial increase in the dose-R2 response occurred as the concentration of MgCl2 in the gel dosimeters increased. The sensitivity of the PAGAT gel with 1.0 M MgCl2 was found to be approximately one order higher than that of the same gel without MgCl2. In addition, the water equivalences of the gels with MgCl2 were evaluated over a wide range of photon energies. The results indicated that MgCl2 acts as a powerful sensitizer to radiation-induced free-radical polymerization in polyacrylamide-type gel dosimeters, but does not interfere with the desirable properties of basic polyacrylamide-type gel dosimeters (i.e., the dose rate and dose integration).
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Rabaeh KA, Eyadeh MM, Hailat TF, Aldweri FM, Alheet SM, Eid RM. Characterization of ferrous-methylthymol blue-polyvinyl alcohol gel dosimeters using nuclear magnetic resonance and optical techniques. Radiat Phys Chem Oxf Engl 1993 2018. [DOI: 10.1016/j.radphyschem.2018.02.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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Eyadeh MM, Rabaeh KA, Hailat TF, Aldweri FM. Evaluation of ferrous Methylthymol blue gelatin gel dosimeters using nuclear magnetic resonance and optical techniques. RADIAT MEAS 2018. [DOI: 10.1016/j.radmeas.2017.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Eyadeh MM, Wierzbicki M, Diamond KR. Measurement of skin surface dose distributions in radiation therapy using poly(vinyl alcohol) cryogel dosimeters. J Appl Clin Med Phys 2017; 18:153-162. [PMID: 28436134 PMCID: PMC5689842 DOI: 10.1002/acm2.12087] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/19/2017] [Accepted: 03/13/2017] [Indexed: 11/10/2022] Open
Abstract
In external beam radiation therapy (EBRT), skin dose measurement is important to evaluate dose coverage of superficial target volumes. Treatment planning systems (TPSs) are often inaccurate in this region of the patient, so in vivo measurements are necessary for skin surface dose estimation. In this work, superficial dose distributions were measured using radiochromic translucent poly(vinyl alcohol) cryogels. The cryogels simultaneously served as bolus material, providing the necessary buildup to achieve the desired superficial dose. The relationship between dose to the skin surface and dose measured with the bolus was established using a series of oblique irradiations with gantry angles ranging from 0° to 90°. EBT-2 Gafchromic film was placed under the bolus, and the ratio of bolus-film dose was determined ranging from 0.749 ± 0.005 to 0.930 ± 0.002 for 0° and 90° gantry angles, respectively. The average ratio over 0-67.5° (0.800 ± 0.064) was used as the single correction factor to convert dose in bolus to dose to the skin surface. The correction factor was applied to bolus measurements of skin dose from head and neck intensity-modulated radiation therapy (IMRT) treatments delivered to a RANDO phantom. The resulting dose distributions were compared to film measurements using gamma analysis with a 3%/3 mm tolerance and a 10% threshold. The minimum gamma pass rate was 95.2% suggesting that the radiochromic bolus may provide an accurate estimation of skin surface dose using a simple correction factor. This study demonstrates the suitability of radiochromic cryogels for superficial dose measurements in megavoltage photon beams.
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Affiliation(s)
- Molham M Eyadeh
- Physics Department, Faculty of Science, Yarmouk University, Irbid, Jordan
| | - Marcin Wierzbicki
- Department of Medical Physics and Applied Radiation Sciences, Juravinski Cancer Centre, McMaster University, Hamilton, ON, Canada
| | - Kevin R Diamond
- Department of Medical Physics and Applied Radiation Sciences, Juravinski Cancer Centre, McMaster University, Hamilton, ON, Canada
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Effect of light source instability on uniformity of 3D reconstructions from a cone beam optical CT scanner. AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE 2014; 37:791-8. [PMID: 25262165 DOI: 10.1007/s13246-014-0302-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 09/19/2014] [Indexed: 01/01/2023]
Abstract
Temporally varying light intensity during acquisition of projection images in an optical CT scanner can potentially be misinterpreted as physical properties of the sample. This work investigated the impact of LED light source intensity instability on measured attenuation coefficients. Different scenarios were investigated by conducting one or both of the reference and data scans in a 'cold' scanner, where the light source intensity had not yet stabilised. Uniform samples were scanned to assess the impact on measured uniformity. The orange (590 nm) light source decreased in intensity by 29 % over the first 2 h, while the red (633 nm) decreased by 9 %. The rates of change of intensity at 2 h were 0.1 and 0.03 % respectively over a 5 min period-corresponding to the scan duration. The normalisation function of the reconstruction software does not fully account for the intensity differences and discrepancies remain. Attenuation coefficient inaccuracies of up to 8 % were observed for data reconstructed from projection images acquired with a cold scanner. Increased noise was observed for most cases where one or both of the scans was acquired without sufficient warm-up. The decrease in accuracy and increase in noise were most apparent for data reconstructed from reference and data scans acquired with a cold scanner on different days.
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Gorjiara T, Hill R, Bosi S, Kuncic Z, Baldock C. Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT. Radiat Phys Chem Oxf Engl 1993 2013. [DOI: 10.1016/j.radphyschem.2013.05.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Gopishankar N, Vivekanandhan S, Rath GK, Laviraj MA, Senthilkumaran S, Kale SS, Thulkar S, Bisht RK, Subramani V. Indigenously developed multipurpose acrylic head phantom for verification of IMRT using film and gel dosimetry. J Appl Clin Med Phys 2013; 14:4041. [PMID: 23470932 PMCID: PMC5714371 DOI: 10.1120/jacmp.v14i2.4041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 09/19/2012] [Accepted: 10/16/2012] [Indexed: 11/23/2022] Open
Abstract
The purpose of this study was to validate the newly designed acrylic phantom for routine dosimetric purpose in radiotherapy. The phantom can be used to evaluate and compare the calculated dose and measured dose using film and gel dosimetric methods. In this study, a doughnut-shaped planning target volume (8.54 cm3) and inner organ at risk (0.353 cm3) were delineated for an IMRT test plan using the X-ray CT image of the phantom. The phantom consists of acrylic slabs which are integrated to form a human head with a hole in the middle where several dosimetric inserts can be positioned for measurement. An inverse planning with nine coplanar intensity-modulated fields was created using Pinnacle TPS. For the film analysis, EBT2 film, flatbed scanner, in-house developed MATLAB codes and ImageJ software were used. The 3D dose distribution recorded in the MAGAT gel dosimeter was read using a 1.5 T MRI scanner. Scanning parameters were CPMG pulse sequence with 8 equidistant echoes, TR = 5600, echo step = 22 ms, pixel size = 0.5 × 0.5, slice thickness = 2 mm. Using a calibration relationship between absorbed dose and spin-spin relaxation rate (R2), R2 images were converted to dose images. The dose comparison was accomplished using in-house MATLAB-based graphical user interface named "IMRT3DCMP". For gel measurement dose grid from the TPS was extracted and compared with the measured dose grid of the gel. Gamma index analysis of film measurement for the tolerance criteria of 2%/2mm, 1%/1 mm showed more than 90% voxels pass rate. Gamma index analysis of 3D gel measurement data showed more than 90% voxels pass rate for different tolerance criteria of 2%/2 mm and 1%/1 mm. Overall both 2D and 3D measurement were in close agreement with the Pinnacle TPS calculated dose. The phantom designed is cost-effective and the results are promising, but further investigation is required to validate the phantom with other 3D conformal techniques for dosimetric purpose.
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Affiliation(s)
- N Gopishankar
- All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
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Zhu X, Reese TG, Crowley EM, El Fakhri G. Improved MAGIC gel for higher sensitivity and elemental tissue equivalent 3D dosimetry. Med Phys 2010; 37:183-8. [PMID: 20175480 DOI: 10.1118/1.3260844] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Polymer-based gel dosimeter (MAGIC type) is a preferable phantom material for PET range verification of proton beam therapy. However, improvement in elemental tissue equivalency (specifically O/C ratio) is very desirable to ensure realistic time-activity measurements. METHODS Glucose and urea was added to the original MAGIC formulation to adjust the O/C ratio. The dose responses of the new formulations were tested with MRI transverse relaxation rate (R2) measurements. RESULTS The new ingredients improved not only the elemental composition but also the sensitivity of the MAGIC gel. The O/C ratios of our new gels agree with that of soft tissue within 1%. The slopes of dose response curves were 1.6-2.7 times larger with glucose. The melting point also increased by 5 degrees C. Further addition of urea resulted in a similar slope but with an increased intercept and a decreased melting point. CONCLUSIONS Our improved MAGIC gel formulations have higher sensitivity and better elemental tissue equivalency for 3D dosimetry applications involving nuclear reactions.
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Affiliation(s)
- Xuping Zhu
- Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, USA.
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Warman JM, de Haas MP, Luthjens LH. High-energy radiation monitoring based on radio-fluorogenic co-polymerization. I: Small volume in situ probe. Phys Med Biol 2009; 54:3185-200. [PMID: 19420430 DOI: 10.1088/0031-9155/54/10/015] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A method of radiation dosimetry is described which is based on the radiation-induced initiation of polymerization of a bulk monomer (e.g. methyl methacrylate) containing a small concentration (about 100 ppm) of a compound which is non-fluorescent but which becomes highly fluorescent when it is incorporated into a growing polymer chain of the bulk monomer. We call the overall process 'radio-fluorogenic co-polymerization' or RFCP for short. The method is illustrated by results on the in situ monitoring of the accumulated dose within the irradiation chamber of a cobalt-60 gamma-ray source using a small plastic capsule containing about 0.2 ml of an RFCP solution. Remote monitoring of the fluorescence is carried out on a timescale of seconds using optical fibres connecting the probe to a 360 nm LED excitation source and a miniature spectrophotometer. The fluorescence is permanent and the intensity is linearly proportional to the accumulated dose from a few tenths of a gray up to hundreds of gray. The sensitivity to dose depends on the polymerizable monomer used and obeys a square root dependence on dose rate over the range studied, 0.27-3.76 Gy min(-1). The polymeric nature of the fluorescent product suggests that the RFCP effect could be used to provide fixed two- or three-dimensional fluorescent images of dose deposition in gel films or phantoms.
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Affiliation(s)
- J M Warman
- Reactor Institute R3/RIH, Technical University of Delft, Mekelweg 15, 2629 JB Delft, The Netherlands.
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