An investigation of the pre-irradiation temporal stability of PAGAT gel dosimeter

Khoei, Shadi; Moorrees, Joshua; Langton, Christian; Trapp, Jamie

doi:10.1088/1742-6596/250/1/012019

Cited by 12 publications

(11 citation statements)

References 2 publications

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“…A PAGAT gel dosimeter was prepared as described by Venning et al 29 with 8 mM of Tetrakis (hydroxymethyl) phosphonium chloride (THPC) for improved stability. 30 The gel dosimeter was prepared under normal atmospheric conditions and poured into a cylindrical Polyethylene terephthalate (PET) container of 10 cm height and 5 cm radius. It was then stored at 4 C for 24 h before irradiation.…”

Section: Iia Gel Preparation and Irradiationmentioning

confidence: 99%

Improved image quality for x‐ray CT imaging of gel dosimeters

et al. 2011

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Section: Iia Gel Preparation and Irradiationmentioning

confidence: 99%

Improved image quality for x‐ray CT imaging of gel dosimeters

et al. 2011

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“…1 (c). A PAGAT polymer gel dosimeter was also prepared as per the recipe recommended by Venning et al and Khoei et al [20,21]. When the preparation of the final polymer gel solution was completed, it was transferred into two 7cm diameter, cylindrical containers one of which contained a 1.5cm diameter circular obstruction.…”

Section: Methodsmentioning

confidence: 99%

Reduction of artefacts caused by missing ray-sum data in optical-CT imaging of implants in gel dosimeters

Asena

Smith

Kairn

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. This study demonstrates the degradation in image quality, and subsequent dose evaluation inaccuracies, that are encountered when an optical-CT system reconstructs an image slice of a gel dosimeter containing an opaque implant, and evaluates the feasibility of a simple correction method to improve the accuracy of radiotherapy dose distribution measurements under these circumstances. MATLAB was used to create a number of different virtual phantoms and treatment plans along with their synthetic projections and reconstructed data sets. The results have illustrated that accurately evaluating 3D gel dose distributions in the vicinity of high-Z interfaces is not possible using the filtered back projection method, without correction, as there are serious artefacts throughout the dose volume that are induced by the missing ray-sum data. Equivalent artefacts were present in physical measurements of irradiated PAGAT gel containers when read by an optical-CT system. An interpolation correction performed prior to reconstruction via the filtered back projection algorithm has been shown to significantly improve dose evaluation accuracy to within approximately 15 mm of the opacity. With careful placement of the implant within the gel sample, and use of the linear interpolation method described in this study, there is the potential for more accurate optical CT imaging of gels containing opaque objects. IntroductionGel dosimeters show potential for measuring complex radiation dose distributions, particularly in radiotherapy [1][2][3][4][5][6][7][8][9][10]. Among the potential applications of gel dosimeters in radiotherapy are those in which the irradiated portion of the gel dosimeter surrounds an imbedded object, such as a metallic implant [11][12][13], head and neck phantoms [14], inserts for brachytherapy measurements [15], or implanted scintillators [16]. In these cases, options for readout of gel dosimeters are limited; there is significant potential for artefacts in MRI and x-ray CT, and missing data in optical computed tomography (optical-CT) due to opacity of the object.In this work we investigate a methodology for reconstruction of optical-CT images of gel dosimeters which contain obstructions, thereby removing ray-sum data from projections acquired during imaging. The filtered back projection (FBP) method, which is currently employed in both x-ray CT and optical-CT systems, does not provide a mechanism to deal with incomplete sets of projection data or missing ray-sum data caused by metallic or opaque implants [17]. A number of different reconstruction methods to reduce metal artefacts in x-ray CT have been proposed [18,19] showing mixed results.

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“…A PAGAT gel dosimeter according to the recipe of Venning et al (who studied PAGAT gel dosimeters using magnetic resonance imaging) (3) was prepared with increased concentration (8 mM) of Tetrakis (hydroxymethyl) phosphonium chloride (THPC) for improved stability, as suggested by Khoei et al in their investigation of the pre‐irradiation temporal stability of PAGAT gel dosimeter (11) . The gel was poured into a cylindrical polyethylene terephthalate (PET) container and stored at 4°C for 15 hours prior to irradiation.…”

Section: Methodsmentioning

confidence: 99%

A feasibility study of multislice X‐ray CT imaging of gel dosimeters using the “zero scan” method

Kakakhel

Kairn²,

Charles³

et al. 2014

J Applied Clin Med Phys

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This study extends the ‘zero scan’ method for CT imaging of polymer gel dosimeters to include multislice acquisitions. Multislice CT images consisting of 24 slices of 1.2 mm thickness were acquired of an irradiated polymer gel dosimeter and processed with the zero scan technique. The results demonstrate that zero scan‐based gel readout can be successfully applied to generate a three‐dimensional image of the irradiated gel field. Compared to the raw CT images, the processed figures and cross‐gel profiles demonstrated reduced noise and clear visibility of the penumbral region. Moreover, these improved results further highlight the suitability of this method in volumetric reconstruction with reduced CT data acquisition per slice. This work shows that 3D volumes of irradiated polymer gel dosimeters can be acquired and processed with X‐ray CT.PACS number: 87.57.Q‐, 87.57.nf, 87.55.‐x

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An investigation of the pre-irradiation temporal stability of PAGAT gel dosimeter

Cited by 12 publications

References 2 publications

Improved image quality for x‐ray CT imaging of gel dosimeters

Improved image quality for x‐ray CT imaging of gel dosimeters

Reduction of artefacts caused by missing ray-sum data in optical-CT imaging of implants in gel dosimeters

A feasibility study of multislice X‐ray CT imaging of gel dosimeters using the “zero scan” method

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