Investigation of scattered dose in a mouse phantom model for pre-clinical dosimetry studies

Entezam, Amir; Fielding, Andrew; Moi, Davide; Bradley, D.A.; Ratnayake, Gishan; Sim, Lucy; Kralik, Chelsea; Fontanarosa, Davide

doi:10.1016/j.radphyschem.2021.109691

Cited by 3 publications

(13 citation statements)

References 65 publications

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“…The other method to deliver the prescribed dose to the whole tumour volume is by delivering a significantly higher dose to the tumour centre to achieve clinically acceptable prescribed tumour dose coverage (e.g., 95% of the prescription dose) everywhere. It must be highlighted that our specific study ultimately aims at investigating abscopal effects of RT [ 50 ], for which we do not need to deliver a homogeneous dose to the whole target [ 49 ], but only deliver enough dose to a certain fraction of the target [ 74 , 75 ]. So, at this stage, it was not essential to employ a bolus for tumour irradiations in our experiments.…”

Section: Discussionmentioning

confidence: 99%

“…Fig 3B demonstrates the placement of the PMMA phantom in the main chamber of the collimator on the polystyrene, with the tumour positioned within the collimated beam ready for irradiation. Film dosimetry was performed based on the Gafchromic film dosimetry procedure given in previous studies [ 50 , 55 ], and a dose profile measurement was obtained. The irradiated film along with the profile line and the region where the film was exposed is demonstrated in Fig 3C .…”

Section: Methodsmentioning

confidence: 99%

“…We have previously constructed an add-on lead collimator to allow for targeted irradiation of mice [49]. In previous studies, we showed that our collimator combined with a 137Cs source irradiator is an effective method for irradiating small animal xenograft tumours [49][50][51]. The simulation of MC mouse phantom irradiation was performed using a 1-cm diameter beam produced by the collimator [49] mounted onto a Gammacell 40 Exactor irradiator unit (Best Theratronics, ON K2K OE4, Canada) located at Transitional Research Institute (TRI), Brisbane, Australia.…”

Section: Simulation Of the Irradiation Systemmentioning

confidence: 99%

“…A PMMA phantom, manufactured by our research group [50], was used for dose measurement. The phantom was made of a PMMA slab with dimensions of (6.75 × 2.25 × 1.50) cm 3 and an extrusion with diameter of (0.50 × 0.50 × 0.75) cm 3 was implanted on the side to represent the radiological characteristics and approximate shape of a mouse soft tissue with a xenograft tumour model in the flank as demonstrated in Fig 3A . The phantom was sliced into two equivalent slabs to allow for the secure placement of radiochromic film.…”

Section: Pmma Phantom Dose Measurementmentioning

confidence: 99%

“…Good agreement between the measured and calculated doses guarantees the accuracy of MC modelling. Several studies have used dosimeters within slabs of PMMA phantom or simple water phantoms to measure the doses, comparing them with the MC simulation results [45][46][47][48][49][50]. In this study, we use the same method for the verification of our MC simulations.…”

Section: Introductionmentioning

confidence: 99%

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Absorbed dose calculation for a realistic CT-derived mouse phantom irradiated with a standard Cs-137 cell irradiator using a Monte Carlo method

et al. 2023

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Computed tomography (CT) derived Monte Carlo (MC) phantoms allow dose determination within small animal models that is not feasible with in-vivo dosimetry. The aim of this study was to develop a CT-derived MC phantom generated from a mouse with a xenograft tumour that could then be used to calculate both the dose heterogeneity in the tumour volume and out of field scattered dose for pre-clinical small animal irradiation experiments. A BEAMnrc Monte-Carlo model has been built of our irradiation system that comprises a lead collimator with a 1 cm diameter aperture fitted to a Cs-137 gamma irradiator. The MC model of the irradiation system was validated by comparing the calculated dose results with dosimetric film measurement in a polymethyl methacrylate (PMMA) phantom using a 1D gamma-index analysis. Dose distributions in the MC mouse phantom were calculated and visualized on the CT-image data. Dose volume histograms (DVHs) were generated for the tumour and organs at risk (OARs). The effect of the xenographic tumour volume on the scattered out of field dose was also investigated. The defined gamma index analysis criteria were met, indicating that our MC simulation is a valid model for MC mouse phantom dose calculations. MC dose calculations showed a maximum out of field dose to the mouse of 7% of Dmax. Absorbed dose to the tumour varies in the range 60%-100% of Dmax. DVH analysis demonstrated that tumour received an inhomogeneous dose of 12 Gy-20 Gy (for 20 Gy prescribed dose) while out of field doses to all OARs were minimized (1.29 Gy-1.38 Gy). Variation of the xenographic tumour volume exhibited no significant effect on the out of field scattered dose to OARs. The CT derived MC mouse model presented here is a useful tool for tumour dose verifications as well as investigating the doses to normal tissue (in out of field) for preclinical radiobiological research.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Simulation Of the Irradiation Systemmentioning

confidence: 99%

Section: Pmma Phantom Dose Measurementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Absorbed dose calculation for a realistic CT-derived mouse phantom irradiated with a standard Cs-137 cell irradiator using a Monte Carlo method

et al. 2023

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In-silico evaluation of the effect of set-up errors on dose delivery during mouse irradiations with a cell irradiator-based collimator system

Entezam

Fielding

Ratnayake

et al. 2023

Preprint

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Set-up errors are a problem for pre-clinical irradiators that lack imaging capabilities. The aim of this study was to investigate the impact of the potential set-up errors on the dose distribution for a mouse with a xenographic tumour irradiated with a Gammacell irradiator equipped with an in-house lead collimator with 10 mm diameter apertures. The EGSnrc Monte-Carlo (MC) code was used to simulate the potential errors caused by displacements of the mouse in the irradiation setup. The impact of the simulated set-up displacements on the dose delivered to the xenographic tumour and surrounding organs was assessed. MC dose calculations were performed in a Computed Tomography (CT) derived model of the mouse for the reference position of the tumour in the irradiation setup. The errors were added into the CT data and then the mouse doses for the corresponding shifts were recalculated and dose volume histograms (DVHs) were generated. The investigation was performed for 1 cm and 0.5 cm diameter tumours. The DVH resulting from introducing the maximum setup errors for 1 cm diameter tumours showed up to 35% reduced dose to a significant fraction of the tumour volume. The setup errors demonstrated an insignificant effect on doses for 0.5 cm diameter tumour irradiations. Setup errors were observed to have negligible impact on out of field doses to organs at risk. The dosimetric results presented herein verify the robustness of our collimator system for irradiations of xenograft tumours up to 0.5 cm diameter in the presence of the maximum setup errors.

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Testing and Treating Cancer with Radation Pharmaceutical Therapy (RPT)

Padmapriya¹,

Babu²,

K³

et al. 2023

Intern. J. Zool. Invest.

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Radation Pharmaceutical Therapy (RPT) is a safe and effective targeted approach to many cancers. In RPT, radiation is administered either systemically or locally utilising drugs that preferably attach to cancer cells or accumulate through physiological systems. Nearly all radionuclides in RPT generate imageable photons that allow the biodistribution of the therapeutic agent to be displayed without invasion. RPT has showed low toxicity in comparison to nearly all other systemic therapy alternatives for cancer. The extraordinary potential of this process is now acknowledged with the recent FDA approval of numerous RPT medicines. This review deals with the basic characteristics, clinical development and associated difficulties of RPT.

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Investigation of scattered dose in a mouse phantom model for pre-clinical dosimetry studies

Cited by 3 publications

References 65 publications

Absorbed dose calculation for a realistic CT-derived mouse phantom irradiated with a standard Cs-137 cell irradiator using a Monte Carlo method

Absorbed dose calculation for a realistic CT-derived mouse phantom irradiated with a standard Cs-137 cell irradiator using a Monte Carlo method

In-silico evaluation of the effect of set-up errors on dose delivery during mouse irradiations with a cell irradiator-based collimator system

Testing and Treating Cancer with Radation Pharmaceutical Therapy (RPT)

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