Intensity modulated radiation therapy: Film verification of planar dose maps

Tangboonduangjit, P; Wu, I-Hsien; Butson, Martin J; Rosenfeld, Anatoly B.; Metcalfe, Peter E

doi:10.1007/bf03179181

Cited by 4 publications

(4 citation statements)

References 22 publications

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“…The challenge of this study is that unlike the EBT (Fontanarosa et al 2009, Kairn et al 2011, Ong et al 2011, Palmer et al 2013 and EDR (Chetty and Charland 2002, Dogan et al 2002, Charland et al 2003, Tangboonduangjit et al 2003, Zeidan et al 2004, Suriyapee et al 2008 films that had been already widely used in dose measurements with good reputations for dose-response stability, the RTQA film has never been used in patient dose verification works before due to the inherent dose variability (Thomas and Warrington 2006). This study provides an extra option for the use of 2D relative dose measurement devices in patient QA.…”

Section: Discussionmentioning

confidence: 99%

Developing new extension of GafChromic RTQA2 film to patient quality assurance field using a plan-based calibration method

et al. 2015

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GafChromic RTQA2 film is a type of radiochromic film designed for light field and radiation field alignment. The aim of this study is to extend the application of RTQA2 film to the measurement of patient specific quality assurance (QA) fields as a 2D relative dosimeter.Pre-irradiated and post-irradiated RTQA2 films were scanned in reflection mode using a flatbed scanner. A plan-based calibration (PBC) method utilized the mapping information of the calculated dose image and film grayscale image to create a dose versus pixel value calibration model. This model was used to calibrate the film grayscale image to the film relative dose image. The dose agreement between calculated and film dose images were analyzed by gamma analysis. To evaluate the feasibility of this method, eight clinically approved RapidArc cases (one abdomen cancer and seven head-and-neck cancer patients) were tested using this method. Moreover, three MLC gap errors and two MLC transmission errors were introduced to eight Rapidarc cases respectively to test the robustness of this method.The PBC method could overcome the film lot and post-exposure time variations of RTQA2 film to get a good 2D relative dose calibration result. The mean gamma passing rate of eight patients was 97.90% ± 1.7%, which showed good dose consistency between calculated and film dose images. In the error test, the PBC method could over-calibrate the film, which means some dose error in the film would be falsely corrected to keep the dose in film consistent with the dose in the calculated dose image. This would then lead to a false negative result in the gamma analysis. In these cases, the derivative curve of the dose calibration curve would be non-monotonic which would expose the dose abnormality.By using the PBC method, we extended the application of more economical RTQA2 film to patient specific QA. The robustness of the PBC method has been improved by analyzing the monotonicity of the derivative of the calibration curve.

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Section: Discussionmentioning

confidence: 99%

Developing new extension of GafChromic RTQA2 film to patient quality assurance field using a plan-based calibration method

et al. 2015

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“…An optical density to dose conversion is applied using a polynomial fit to a set of standard dose films. The dose delivered to the planar check film is then compared against the dose predicted using the RTPS (Tangboonduangjit et al 2003).…”

Section: Methodsmentioning

confidence: 99%

Intensity-modulated radiation therapy: overlapping co-axial modulated fields

Metcalfe¹,

Tangboonduangjit²,

White³

2004

Phys. Med. Biol.

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The Varian multi-leaf collimator has a 14.5 cm leaf extension limit from each carriage. This means the target volumes in the head and neck region are sometimes too wide for standard width-modulated fields to provide adequate dose coverage. A solution is to set up asymmetric co-axial overlapping fields. This protects the MLC carriage while in return the MLC provides modulated dose blending in the field overlap region. Planar dose maps for coincident fields from the Pinnacle radiotherapy treatment planning system are compared with planar dose maps reconstructed from radiographic film and electronic portal images. The film and portal images show small leaf-jaw matchlines at each field overlap border. Linear profiles taken across each image show that the observed leaf-jaw matchlines from the accelerator images are not accounted for by the treatment planning system. Dose difference between film reconstructed electronic portal images and planning system are about 2.5 cGy in a modulated field at d(max). While the magnitude of the dose differences are small improved round end leaf modelling combined with a finer dose calculation grid may minimize the discrepancy between calculated and delivered dose.

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“…Dose distribution comparison is performed routinely in radiotherapy-related activities, e.g., patient-specific quality assurance (QA) using 2D/3D dosimeters for intensity-modulated radiation therapy (IMRT) (Low et al 1998b, 1999, Childress et al 2002, Dogan et al 2002, Ju et al 2002, Kapulsky et al 2002, Low 2002, Olch 2002, Partridge et al 2002, Zhu et al 2002, Chang and Ling 2003, Greer and Popescu 2003, Jursinic and Nelms 2003, Leal et al 2003, Richardson et al 2003, Tangboonduangjit et al 2003, Warkentin et al 2003, Bucciolini et al 2004, Letourneau et al 2004, Van Esch et al 2004, Yeo et al 2004. This is not a trivial task due to the fact that, to be clinically relevant, we need to compare dose distributions in both dose and spatial domains (Van Dyk et al 1993, Childress et al 2002.…”

Section: Introductionmentioning

confidence: 99%

On dose distribution comparison

et al. 2006

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In radiotherapy practice, one often needs to compare two dose distributions. Especially with the wide clinical implementation of intensity-modulated radiation therapy, software tools for quantitative dose (or fluence) distribution comparison are required for patient-specific quality assurance. Dose distribution comparison is not a trivial task since it has to be performed in both dose and spatial domains in order to be clinically relevant. Each of the existing comparison methods has its own strengths and weaknesses and there is room for improvement. In this work, we developed a general framework for comparing dose distributions. Using a new concept called maximum allowed dose difference (MADD), the comparison in both dose and spatial domains can be performed entirely in the dose domain. Formulae for calculating MADD values for various comparison methods, such as composite analysis and gamma index, have been derived. For convenience in clinical practice, a new measure called normalized dose difference (NDD) has also been proposed, which is the dose difference at a point scaled by the ratio of MADD to the predetermined dose acceptance tolerance. Unlike the simple dose difference test, NDD works in both low and high dose gradient regions because it considers both dose and spatial acceptance tolerances through MADD. The new method has been applied to a test case and a clinical example. It was found that the new method combines the merits of the existing methods (accurate, simple, clinically intuitive and insensitive to dose grid size) and can easily be implemented into any dose/intensity comparison tool.

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Intensity modulated radiation therapy: Film verification of planar dose maps

Cited by 4 publications

References 22 publications

Developing new extension of GafChromic RTQA2 film to patient quality assurance field using a plan-based calibration method

Developing new extension of GafChromic RTQA2 film to patient quality assurance field using a plan-based calibration method

Intensity-modulated radiation therapy: overlapping co-axial modulated fields

On dose distribution comparison

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