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Abtahi SMM, Bahrami F, Sardari D. An investigation into the dose rate and photon energy dependence of the GENA gel dosimeter in the MeV range. Phys Med 2023; 106:102522. [PMID: 36603480 DOI: 10.1016/j.ejmp.2022.102522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 12/22/2022] [Accepted: 12/27/2022] [Indexed: 01/05/2023] Open
Abstract
PURPOSE In the current study, the energy and dose rate dependence of a new genipin-based gel dosimeter, named GENA gel dosimeter, were investigated. METHODS Prepared gel dosimeters exposed using a Varian clinical linac. Beam qualities of 6 and 18 MV were applied to investigate the GENA gel dosimeter's energy dependence. Furthermore, the gel dosimeters were exposed to 50, 100, 200, and 350 cGy/min dose rates, ranging from 0 to 8 Gy. The irradiated gel dosimeters were read out using a double beam UV-Visible spectrophotometer. The absorbance peak (AP) and area under spectrum (AUS) were evaluated. RESULTS Absorbance-dose sensitivities of (8.0 ± 0.18) × 10-3 cm-1Gy-1 and (7.8 ± 0.15) × 10-3 cm-1Gy-1 were obtained for GENA gel dosimeter for 6 and 18 MV beam qualities, respectively. Results specified no significant difference (p > 0.05) between the GENA gel dosimeter's sensitivities irradiated using the two energies mentioned above. For the mentioned dose rates, AP-dose sensitivities of (8.2 ± 0.22) × 10-3, (8.1 ± 0.21) × 10-3, (8.1 ± 0.2) × 10-3 and (8.0 ± 0.18) × 10-3 cm-1Gy-1 were obtained, respectively. Results showed no significant difference (p > 0.05) between the GENA gel dosimeter's sensitivities for the investigated dose rates and energies. In addition, results revealed that when the incident photon energy and dose rate changed, there were no significant differences (p > 0.05) between the GENA gel dosimeter's dose resolution values. CONCLUSIONS It is concluded that the response of the GENA gel dosimeter is not dependent on the energy and dose rate (p > 0.05) within the studied energy and dose rate ranges.
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Affiliation(s)
| | - Farbod Bahrami
- Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
| | - Dariush Sardari
- Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
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Cumur C, Fujibuchi T, Hamada K. Dose estimation for cone-beam computed tomography in image-guided radiation therapy using mesh-type reference computational phantoms and assuming head and neck cancer. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2022; 42:021533. [PMID: 35705020 DOI: 10.1088/1361-6498/ac7914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
This study aimed to estimate the additional dose the cone-beam computed tomography (CBCT) system integrated into the Varian TrueBeam linear accelerator delivers to a patient with head and neck cancer using mesh-type International Commission on Radiological Protection reference computational phantoms. In the first part, for use as a benchmark for the accuracy of the Monte Carlo geometry of CBCT, Particle and Heavy Ion Transport code System (PHITS) calculations were confirmed against measured lateral and depth dose profiles using a computed tomography dose profiler. After obtaining good agreement, organ dose calculations were performed by PHITS using mesh-type reference computational phantom (MRCP) and irradiating the neck region; the effective dose was calculated utilising absorbed organ doses and tissue weighting factors for male and female MRCP. Substantially, it has been found that the effective doses for male and female MRCP are 0.81 and 1.06 mSv, respectively. As this study aimed to assess the imaging dose from the CBCT system used in image-guided radiation therapy, it is required to take into account this dose in terms of both the target organ and surrounding tissues. Although the absorbed organ dose values and effective dose values obtained for both MRCP males and females were small, attention should be paid to the additional dose resulting from CBCT. This study can create awareness on the importance of doses arising from imaging techniques, especially CBCT.
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Affiliation(s)
- Ceyda Cumur
- Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka City 812-8582, Japan
| | - Toshioh Fujibuchi
- Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka City 812-8582, Japan
| | - Keisuke Hamada
- Department of Radiological Technology, National Hospital Organisation Kyushu Cancer Center, 3-1-1, Notame Minami-ku, Fukuoka City 811-1395, Japan
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Ota J, Yokota H, Kobayashi T, Ogata Y, Kubo T, Chida K, Masuda Y, Uno T. Head CT dose reduction with organ-based tube current modulation. Med Phys 2022; 49:1964-1971. [PMID: 35060639 DOI: 10.1002/mp.15467] [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: 02/16/2021] [Revised: 12/16/2021] [Accepted: 12/17/2021] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND A helical head CT examination uses a pitch factor (PF) of < 1.0, resulting in a part of the slice being directly irradiated twice. This raises the possibility of double irradiation, which may increase the amount of radiation to the lens. Organ-based tube current modulation (OBTCM) is an effective method for reducing lens exposure because it reduces the dose to the anterior aspect of the patient. However, it is challenging to visualize the complex dose distribution when factoring in double irradiation. PURPOSE To visualize twice-irradiated areas in helical head CT in three dimensions and to clarify the exposure reduction effect of OBTCM. MATERIAL AND METHODS A leuco crystal violet (LCV) dosimeter was placed into an empty polyethylene terephthalate bottle 16.5 cm in diameter. Helical scans were performed without and with OBTCM using the following parameters: tube voltage 120 kV, tube current 600 mA, pitch factor 0.637, rotation time 0.5 s, 80 (detector rows) × 0.5 mm (detector collimation), and ten scans. Exposed areas were visualized using an optical computed tomography (OCT) system designed by our group. The dose reduction rate of OBTCM was defined as the ratio of the average values of the histogram with the dose value on the x-axis and the frequency on the y-axis without and with OBTCM at 90° to the anterior midline. RESULTS The LCV dosimeter visualized the spiral-shaped twice-irradiated areas. Double irradiation resulted in a dose of 2.19/1.90 Gy and 1.38/1.19 Gy (15.0% and 15.9% increase) without and with OBTCM, respectively. The dose reduction using OBTCM was 29.6% at 90° anterolateral. CONCLUSION The LCV dosimeter visualized the complex three-dimensional irradiated areas and enabled dose measurement in twice-irradiated areas. Increased exposure from double irradiation was attenuated by OBTCM. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Joji Ota
- Department of Radiology, Chiba University Hospital, 1-8-1, Inohana, Chuo-ku, Chiba City, Chiba, 260-8677, Japan.,School of Radiological Technology, Health Sciences, Graduate School of Medicine, Tohoku University, 2-1 Seiryo, Aoba, Sendai, Miyagi, Japan
| | - Hajime Yokota
- Diagnostic Radiology and Radiation Oncology, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba City, Chiba, 260-8670, Japan
| | - Takenori Kobayashi
- Division of Clinical Radiology, Graduate School of Medical Care and Technology, Teikyo University, 2-11-1 Kaga Itabashi-ku, Tokyo, Japan
| | - Yuki Ogata
- Division of Clinical Radiology, Graduate School of Medical Care and Technology, Teikyo University, 2-11-1 Kaga Itabashi-ku, Tokyo, Japan
| | - Takumi Kubo
- Division of Clinical Radiology, Graduate School of Medical Care and Technology, Teikyo University, 2-11-1 Kaga Itabashi-ku, Tokyo, Japan
| | - Koichi Chida
- School of Radiological Technology, Health Sciences, Graduate School of Medicine, Tohoku University, 2-1 Seiryo, Aoba, Sendai, Miyagi, Japan
| | - Yoshitada Masuda
- Department of Radiology, Chiba University Hospital, 1-8-1, Inohana, Chuo-ku, Chiba City, Chiba, 260-8677, Japan
| | - Takashi Uno
- Diagnostic Radiology and Radiation Oncology, Graduate School of Medicine, Chiba University, 1-8-1, Inohana, Chuo-ku, Chiba City, Chiba, 260-8670, Japan
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Treb K, Li K. Accuracy of weighted CTDI in estimating average dose delivered to CTDI phantoms: An experimental study. Med Phys 2020; 47:6484-6499. [PMID: 33034041 DOI: 10.1002/mp.14528] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 09/25/2020] [Accepted: 09/25/2020] [Indexed: 11/08/2022] Open
Abstract
PURPOSE The concept of the weighted computed tomography dose index ( CTDI w ) was proposed in 1995 to represent the average CTDI across an axial section of a cylindrical phantom. The purpose of this work was to experimentally re-examine the validity of the underlying assumptions behind CTDI w for modern MDCT systems. METHODS To enable experimental mapping of CTDI 100 in the axial plane, in-house 16 and 32 cm cylindrical phantoms were fabricated to allow the pencil chamber to reach any arbitrary axial location within the phantoms. The phantoms were scanned on a clinical MDCT with five beam collimation widths, three bowtie filters, and four kV levels. To evaluate the linearity and rotational invariance assumptions implicitly made when the weighting factors of 1/3 and 2/3 in the CTDI w formula were originally derived, CTDI 100 was measured at different radial and angular locations within the phantom for different collimation, bowtie, and kV combinations. The average CTDI ( CTDI avg ) across the axial plane was calculated from the experimental two-dimensional (2D) dose distribution and was compared with the traditional CTDI w . RESULTS For both phantoms under all scan conditions, the axial dose distributions were found to have significant angular dependence, potentially due to the x-ray attenuation by the patient couch or the head holder. The radial dose profiles were also found to significantly deviate from linearity in many cases due to the presence of the bowtie filter. When only the 12 o'clock peripheral CTDI 100 and the traditional weighting factors were used to calculate CTDI w , the average dose was overestimated in the 16 cm phantom by up to 8.4% at isocenter and up to 35.3% when the phantom was off-centered by 6 cm; in the 32 cm phantom at isocenter, the average dose was overestimated by up to 12.8%. Using an average of the four peripheral CTDI 100 measurements at the 12, 3, 6, and 9 o'clock locations reduced the error of CTDI w to within 1.2% in the 16 cm phantom. For the 32 cm phantom, even by using the average of the peripheral measurements, the traditional CTDI w underestimated the average dose by up to 4.3% due to aggressive drop-off of the CTDI 100 at the phantom periphery. CONCLUSIONS The linearity and rotational-invariance assumptions behind the traditional CTDI w formalism may not be valid for modern CT systems and thus CTDI w may not accurately represent the average dose or radiation output within a CTDI phantom. Utilizing data from all four peripheral locations always improves accuracy of CTDI w in representing the true average dose. For the large (32 cm) phantom, nonlinear models and more measurement points are needed if a more precise estimation of the average axial dose is required.
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Affiliation(s)
- Kevin Treb
- Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Ke Li
- Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, WI, 53705, USA.,Department of Radiology, University of Wisconsin-Madison, 600 Highland Avenue, Madison, WI, 53792, USA
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Abtahi SMM, Pourghanbari M. A new less toxic polymer gel dosimeter: Radiological characteristics and dosimetry properties. Phys Med 2018; 53:137-144. [PMID: 30241748 DOI: 10.1016/j.ejmp.2018.08.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/20/2018] [Accepted: 08/25/2018] [Indexed: 12/27/2022] Open
Abstract
PURPOSE A new polymer gel dosimeter recipe was investigated that may be more suitable for widespread applications than polyacrylamide gel dosimeters, since the extremely toxic acrylamide has been replaced with the less harmful monomer 2-Acrylamido 2-Methyl Propane Sulfonic acid (AMPS). METHODS The new formulation was named PAMPSGAT. The MRI response (R2) of the dosimeters was analyzed for conditions of varying dose, dose rate, and temperature during scanning. Radiological properties of the PAMPSGAT polymer gel dosimeter were investigated. RESULTS The dose-response (R2) of AMPS/Bis appears to be linear over a dose range 10-40 Gy. The percentage of difference between the R2 values for imaging at 15 °C and MRI room temperature is about 4.6% for vial with 40 Gy absorbed dose which decreased to less than 1% for imaging at 20 °C. The percentage difference of Zeff of PAMPSGAT gel and soft tissue was less than 1% in the practical energy range (100 KeV-100 MeV). The electron density of the PAMPSGAT polymer gel was 2.9% higher than that of muscle. Results showed that the sensitivity of PAMPSGAT polymer gel dosimeter irradiated by 60Co (energy = 1.25 MeV) is about 27.7% higher than that of irradiated using a 6 MeV Linac system. CONCLUSIONS Temperature during MRI scanning has a small effect on the R2 response of the PAMPSGAT polymer gel dosimeter. Results confirmed tissue equivalency of the PAMPSGAT polymer gel dosimeter in most practical energy range. The PAMPSGAT polymer gel dosimeter response depends on energy and dose rate.
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Affiliation(s)
| | - Mohammad Pourghanbari
- Medical Imaging Center, Imam Reza Hospital, Kermanshah University of Medical Sciences, Kermanshah, Iran
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Chuang CC, Wu J. Dose and slice thickness evaluation with nMAG gel dosimeters in computed tomography. Sci Rep 2018; 8:2632. [PMID: 29422538 PMCID: PMC5805745 DOI: 10.1038/s41598-018-21022-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/26/2018] [Indexed: 01/06/2023] Open
Abstract
Computed tomography (CT) has been widely used in clinical diagnosis. It is important to estimate radiation dose and perform image quality assurance procedures for CT scans. In this study, nMAG gel dosimeters were used to simultaneously measure the 300-mm weighted CT dose index (CTDI) and slice sensitivity profile (SSP) for multiple detector CT (MDCT). Magnetic resonance imaging (MRI) was performed on the irradiated gel to create R2‒dose response curves for the tube voltages of 120 and 140 kVp. The gel dosimeters were loaded in three home-made cylindrical phantoms to obtain CTDI100 and CTDI300. The full width at half maximum (FWHM) for 2, 5, 10, 14.4, and 38.4-mm slice thicknesses was measured and compared with the result obtained by radiochromic films. The difference in weighted CTDI100 obtained by the gel dosimeter and ionization chamber was less than 1%. The CTDI efficiency at 120 and 140 kVp was in the range of 80.1%-82.5%. The FWHM of SSP measured by the gel dosimeter matched very well with the nominal slice thickness. The use of nMAG gel dosimeters combined with the home-made cylindrical phantoms can provide 300-mm weighted CTDI and slice thickness information, showing potential for quality assurance and clinical applications in MDCT.
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Affiliation(s)
- Chun-Chao Chuang
- Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan.,Department of Medical Image, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Jay Wu
- Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.
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Guberina N, Dietrich U, Arweiler-Harbeck D, Forsting M, Ringelstein A. Comparison of radiation doses imparted during 128-, 256-, 384-multislice CT-scanners and cone beam computed tomography for intra- and perioperative cochlear implant assessment. Am J Otolaryngol 2017; 38:649-653. [PMID: 28942233 DOI: 10.1016/j.amjoto.2017.09.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 09/12/2017] [Accepted: 09/18/2017] [Indexed: 11/26/2022]
Abstract
PURPOSE To examine radiation-doses imparted during multislice (MSCT) and cone-beam computed-tomography (CBCT) for perioperative examination of cochlear-implant insertion. METHODS Radiation-doses were assessed during standardized petrous-bone CT-protocols at different MSCT ((I) single-source CT-scanner Somatom-Definition-AS+, (II) 2nd generation of dual-source CT-scanner Somatom-Definition-Flash, (III) 3rd generation of dual-source CT-scanner Somatom-Force and at the CBCT Ziehm-Vision-RFD3D ((IV) (a) RFD-3D (Standard-modifier), (b) RFD-3D (Low-dose-modifier)). Image quality was examined by two radiologists appraising electrode-array placement, quality-control of cochlear-implant surgery and complications based on real patients' examinations (n=78). RESULTS In MSCT-setting following radiation-doses were assessed (CTDIw; DLP): (I) 21.5mGy; 216mGycm; (II) 19.7mGy; 195mGycm; (III) 12.7mGy; 127mGycm; in the CBCT setting radiation doses were distributed as follows: (IV) (a) 1.9mGy; 19.4mGycm; (b) 1.2mGy; 12.9mGycm. Overall, image quality was evaluated as good for both, MSCT- and CBCT-examinations, with a good interrater reliability (r=0.81). CONCLUSION CBCT bears considerable dose-saving potential for the perioperative examination of cochlear-implant insertion while maintaining adequate image quality.
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Paschoal C, Ferreira F, Souza D, Santos L. Comparison of dose measurements in CT using a photodiode and a small ion chamber. RADIAT MEAS 2016. [DOI: 10.1016/j.radmeas.2016.05.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Johnston H, Hilts M, Jirasek A. Incorporating multislice imaging into x-ray CT polymer gel dosimetry. Med Phys 2015; 42:1666-77. [PMID: 25832056 DOI: 10.1118/1.4914419] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To evaluate multislice computed tomography (CT) scanning for fast and reliable readout of radiation therapy (RT) dose distributions using CT polymer gel dosimetry (PGD) and to establish a baseline assessment of image noise and uniformity in an unirradiated gel dosimeter. METHODS A 16-slice CT scanner was used to acquire images through a 1 L cylinder filled with water. Additional images were collected using a single slice machine. The variability in CT number (NCT) associated with the anode heel effect was evaluated and used to define a new slice-by-slice background subtraction artifact removal technique for CT PGD. Image quality was assessed for the multislice system by evaluating image noise and uniformity. The agreement in NCT for slices acquired simultaneously using the multislice detector array was also examined. Further study was performed to assess the effects of increasing x-ray tube load on the constancy of measured NCT and overall scan time. In all cases, results were compared to the single slice machine. Finally, images were collected throughout the volume of an unirradiated gel dosimeter to quantify image noise and uniformity before radiation is delivered. RESULTS Slice-by-slice background subtraction effectively removes the variability in NCT observed across images acquired simultaneously using the multislice scanner and is the recommended background subtraction method when using a multislice CT system. Image noise was higher for the multislice system compared to the single slice scanner, but overall image quality was comparable between the two systems. Further study showed NCT was consistent across image slices acquired simultaneously using the multislice detector array for each detector configuration of the slice thicknesses examined. In addition, the multislice system was found to eliminate variations in NCT due to increasing x-ray tube load and reduce scanning time by a factor of 4 when compared to imaging a large volume using a single slice scanner. Images acquired through an unirradiated, active gel revealed NCT varies between the top and bottom of the 1 L cylinder as well as across the diameter of the cylinder by up to 7 HU. CONCLUSIONS Multislice CT imaging has been evaluated for CT PGD and found to be the superior technique compared to single slice imaging in terms of the time required to complete a scan and the tube load characteristics associated with each scanning method. The implementation of multislice scanning is straightforward and expected to facilitate routine gel dosimetry measurements for complex dose distributions in modern RT centers.
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Affiliation(s)
- H Johnston
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
| | - M Hilts
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada and Medical Physics, BC Cancer Agency, Vancouver Island Centre, Victoria, British Columbia V8R 6V5, Canada
| | - A Jirasek
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada and Department of Physics, University of British Columbia-Okanagan Campus, Kelowna, British Columbia V1V 1V7, Canada
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Chang YJ, Hsieh LL, Liu MH, Liu JS, Hsieh BT. The study of N-isopropylacrylamide gel dosimeter doped iodinated contrast agents. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/444/1/012109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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12
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Sykes JR, Lindsay R, Iball G, Thwaites DI. Dosimetry of CBCT: methods, doses and clinical consequences. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/444/1/012017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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13
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Vandecasteele J, De Deene Y. On the validity of 3D polymer gel dosimetry: I. Reproducibility study. Phys Med Biol 2012; 58:19-42. [DOI: 10.1088/0031-9155/58/1/19] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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14
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Sedaghat M, Bujold R, Lepage M. Severe dose inaccuracies caused by an oxygen-antioxidant imbalance in normoxic polymer gel dosimeters. Phys Med Biol 2011; 56:601-25. [DOI: 10.1088/0031-9155/56/3/006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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15
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Ghavami SM, Mesbahi A, Pesianian I, Shafaee A, Aliparasti MR. Normoxic polymer gel dosimetry using less toxic monomer of N-isopropyl acrylamide and X-ray computed tomography for radiation therapy applications. Rep Pract Oncol Radiother 2010; 15:172-5. [PMID: 24376945 DOI: 10.1016/j.rpor.2010.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 08/11/2010] [Accepted: 10/01/2010] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Polymer gel dosimetry has been used extensively in radiation therapy for its capability in depicting a three dimensional view of absorbed dose distribution. However, more studies are required to find less toxic and more efficient polymers for application in radiotherapy dosimetry. AIM The purpose of this work was to evaluate the N-isopropyl acrylamide (NIPAM) gel dosimetric characteristics and optimize the protocol for X-ray computed tomography (CT) imaging of gel dosimeters for radiation therapy application. MATERIAL AND METHODS A polymer gel dosimeter based on NIPAM monomer was prepared and irradiated with (60)Co photons. The CT number changes following irradiation were extracted from CT images obtained with different sets of imaging parameters. RESULTS The results showed the dose sensitivity of ΔN CT (H) = 0.282 ± 0.018 (H Gy(-1)) for NIPAM gel dosimeter. The optimized set of imaging exposure parameters was 120 kVp and 200 mA with the 10 mm slice thickness. Results of the depth dose measurement with gel dosimeter showed a great discrepancy with the actual depth dose data. CONCLUSION According to the current study, NIPAM-based gel dosimetry with X-ray CT imaging needs more technical development and formulation refinement to be used for radiation therapy application.
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Affiliation(s)
- Seyed-Mostafa Ghavami
- Radiology department, Paramedical school, Tabriz University of medical sciences, Tabriz, Iran
| | - Asghar Mesbahi
- Medical physics department, Medical school, Tabriz University of medical sciences, Tabriz, Iran
| | - Ismaeel Pesianian
- Radiology department, Paramedical school, Tabriz University of medical sciences, Tabriz, Iran
| | - Abbas Shafaee
- Radiology department, Paramedical school, Tabriz University of medical sciences, Tabriz, Iran
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Baldock C, De Deene Y, Doran S, Ibbott G, Jirasek A, Lepage M, McAuley KB, Oldham M, Schreiner LJ. Polymer gel dosimetry. Phys Med Biol 2010. [PMID: 20150687 DOI: 10.1088/0031‐9155/55/5/r01] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.
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Affiliation(s)
- C Baldock
- Institute of Medical Physics, School of Physics, University of Sydney, Australia.
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Baldock C, De Deene Y, Doran S, Ibbott G, Jirasek A, Lepage M, McAuley KB, Oldham M, Schreiner LJ. Polymer gel dosimetry. Phys Med Biol 2010; 55:R1-63. [PMID: 20150687 DOI: 10.1088/0031-9155/55/5/r01] [Citation(s) in RCA: 450] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.
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Affiliation(s)
- C Baldock
- Institute of Medical Physics, School of Physics, University of Sydney, Australia.
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Baldock C. Historical overview of the development of gel dosimetry: Another personal perspective. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/164/1/012002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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