Performance evaluation of a diode array for enhanced dynamic wedge dosimetry

Zhu, Timothy C.; Ding, Lining; Liu, C. R.; Palta, Jatinder; Simon, William E.; Shi, Jinjing

doi:10.1118/1.598019

Cited by 42 publications

(27 citation statements)

References 12 publications

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“…5 The dead time measurements were carried out using 4 MV x rays over the range of the dose rates ͑250, 200, 150, and 100 MU/min͒ available with the commercial medical linear accelerator. The measured dead times were 0.7Ϯ1.1 ms at the dose rate of 250 MU/min, 0.8Ϯ1.7 ms at 200 MU/min, 1.9 Ϯ2.2 ms at 150 MU/min, and 0.4Ϯ2.3 ms at 100 MU/min.…”

Section: Methodsmentioning

confidence: 99%

“…It is essential to verify the dose distribution before an IMRT treatment procedure is applied to a patient. Some methods to verify the delivered dose have been investigated by Zhu et al 5 using a diode array, Ibbott et al 6 using magnetic resonance imaging of BANG polymer gel dosimeters, Curtin-Savard and Podgorsak using a commercial electronic portal imaging device to evaluate the segmented beam delivery, 7 and Ma et al using an accurate and independent Monte Carlo dose calculation algorithm. 8 However, except for the independent dose calculation method, the experimental techniques require a lengthy and sometimes costly analysis process before the data is available.…”

Section: Introductionmentioning

confidence: 99%

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Verification of IMRT dose distributions using a water beam imaging system

Boyer

2001

Medical Physics

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A water beam imaging system (WBIS) has been developed and used to verify dose distributions for intensity modulated radiotherapy using dynamic multileaf collimator. This system consisted of a water container, a scintillator screen, a charge-coupled device camera, and a portable personal computer. The scintillation image was captured by the camera. The pixel value in this image indicated the dose value in the scintillation screen. Images of radiation fields of known spatial distributions were used to calibrate the device. The verification was performed by comparing the image acquired from the measurement with a dose distribution from the IMRT plan. Because of light scattering in the scintillator screen, the image was blurred. A correction for this was developed by recognizing that the blur function could be fitted to a multiple Gaussian. The blur function was computed using the measured image of a 10 cm x 10 cm x-ray beam and the result of the dose distribution calculated using the Monte Carlo method. Based on the blur function derived using this method, an iterative reconstruction algorithm was applied to recover the dose distribution for an IMRT plan from the measured WBIS image. The reconstructed dose distribution was compared with Monte Carlo simulation result. Reasonable agreement was obtained from the comparison. The proposed approach makes it possible to carry out a real-time comparison of the dose distribution in a transverse plane between the measurement and the reference when we do an IMRT dose verification.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Verification of IMRT dose distributions using a water beam imaging system

Boyer

2001

Medical Physics

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“…These have been verified by many researchers, and these dose evaluation methods are still in use today. 11,[27][28][29][30][31][32][33][34] In addition, the evaluation of an absolute isocenter dose and 2D dose distribution are considered to be adequate for delivery QA of arc therapy, such as IMAT or VMAT. 35,36 Wagner and Vorwerk 35 reported that the use of a 2D ionization chamber (MatriXX™; IBA Dosimetry GmbH, Schwarzenbruck, Germany) for VMAT plan verification is reasonable in clinical routine use.…”

Section: Discussionmentioning

confidence: 99%

Advantage of 3D volumetric dosemeter in delivery quality assurance of dynamic arc therapy: comparison of pencil beam and Monte Carlo calculations

Shin

Jh²,

Jung³

et al. 2013

BJR

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Objective: To evaluate the accuracy of pencil beam calculation (PBC) and Monte Carlo calculation (MCC) for dynamic arc therapy (DAT) in a cylindrically shaped homogenous phantom, by comparing the two plans with an ion chamber, a film and a three-dimensional (3D) volumetric dosemeter. Methods: For this study, an in-house phantom was constructed, and the PBC and MCC plans for DAT were performed using iPlan® RT (BrainLAB®, Heimstetten, Germany). The A16 micro ion chamber (Standard Imaging, Middleton, WI), Gafchromic® EBT2 film (International Specialty Products, Wayne, NJ) and ArcCHECK™ (Sun Nuclear, Melbourne, FL) were used for measurements. For comparison with each plan, two-dimensional (2D) and 3D gamma analyses were performed using 3%/3 mm and 2%/2 mm criteria. Results: The difference between the PBC and MCC plans using 2D and 3D gamma analyses was found to be 7.85%and 28.8%, respectively. The ion chamber and 2D dose distribution measurements did not exhibit this difference revealed by the comparison between the PBC and MCC plans. However, the 3D assessment showed a significant difference between the PBC and MCC (62.7% for PBC vs 93.4% for MCC, p 5 0.034).Conclusion: Evaluation using a 3D volumetric dosemeter can be clinically useful for delivery quality assurance (QA), and the MCC should be used to achieve the most reliable dose calculation for DAT. Advances in knowledge:(1) The DAT plan calculated using the PBC has a limitation in the calculation methods, and a 3D volumetric dosemeter was found to be an adequate tool for delivery QA of DAT. (2) The MCC was superior to PBC in terms of the accuracy in dose calculation for DAT even in the homogenous condition.Over the past few years, there has been a considerable growth in interest concerning arc therapy. This includes a range of techniques, such as dynamic arc therapy (DAT), intensity-modulated arc therapy (IMAT), helical tomotherapy and volumetric modulated arc therapy (VMAT). 1-3These developments have been accompanied by the improvement of dose calculation algorithms and a significant increase in treatment efficiency, thus resulting in shorter treatment times and a smaller number of monitor units (MUs) than with intensity-modulated radiotherapy (IMRT) and other conventional methods.Existing arc therapy planning methods, such as pencil beam calculation (PBC), are based on dividing the full rotation angle by a uniform control point and then optimizing the results. 4,5 Only the dose calculation based on a control point below a certain angle has been previously reported to be an accurate dose delivery to the target area.4,6-8 However, the errors from approximating the arc with individual beams could occur in the area where adjacent beams do not overlap. 9 This area could be wide when the phantom size is large or when the field or target size is small. Compared with PBC, Monte Carlo calculation (MCC) has made accurate dose calculations possible because the accuracy of the dose calculation using MCC depends on the number of simulation histories rather than the numb...

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“…Several investigators have used different dosimetric methods to measure dose distribution for the dynamic wedge. For example diode detector arrays, radiation sensitive film, Fricke gel dosimeters and ion chamber arrays (Bengtsson et al 1996and Zhu et al 1997.…”

Section: Simple Ldr Brachytherapymentioning

confidence: 99%

An investigation into the applications of polymer gel dosimetry in radiotherapy

Farajollahi

1999

Medical Physics

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The verification of complex dose distributions produced using novel techniques in radiotherapy requires measurements in three dimensions with high spatial resolution. Recent developments in polymer gel dosimetry employing MRI suggest this may be the best available method. In this work the properties of BANG (bis, acrylamide, nitrogen, and gelatin) polymer gel were investigated. The gel was found to be tissue equivalent and its response to absorbed dose reproducible to within ±4% and linear up to 10–12 Gy. The response of the gel was also found to be independent of energy and dose rate, but dependent on oxygen contamination and gel temperature during MR imaging. The application of BANG gel in different areas of radiotherapy was investigated. In brachytherapy a comparison of the relative dose rate distributions between gel, calculation, and TLDs agreed to within ±5%. The measured dose distributions from complex brachytherapy and multifield external beam irradiations agreed well with the distribution produced by the Helax‐TMS planning system. For external beam irradiation the depth doses measured in the gel showed good agreement with ion chamber measurements to within ±3%. The gel was also used to verify the absorbed dose distribution produced by intensity modulated beam techniques using compensators. The results agreed well with film dosimetry. BANG gel was also found to be an excellent candidate for dynamic measurements and measurements in areas with restricted access. A novel technique for measurements in boron neutron capture therapy using boron‐loaded gel is also described. It was concluded that gel can be used to verify complex dose distributions. [Copies of the thesis are available from Main Library, University of Leicester, University Road, Leicester, LE1 7RH, England.]

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Performance evaluation of a diode array for enhanced dynamic wedge dosimetry

Cited by 42 publications

References 12 publications

Verification of IMRT dose distributions using a water beam imaging system

Verification of IMRT dose distributions using a water beam imaging system

Advantage of 3D volumetric dosemeter in delivery quality assurance of dynamic arc therapy: comparison of pencil beam and Monte Carlo calculations

An investigation into the applications of polymer gel dosimetry in radiotherapy

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