A5028474874- Advanced Radiotherapy Techniques
- Medical Imaging Techniques and Applications
- Radiation Therapy and Dosimetry
- Radiation Dose and Imaging
- Advanced X-ray and CT Imaging
- Radiomics and Machine Learning in Medical Imaging
- Lung Cancer Diagnosis and Treatment
- Radiation Effects and Dosimetry
- Digital Radiography and Breast Imaging
- Advances in Oncology and Radiotherapy
- Radiation Detection and Scintillator Technologies
- Prostate Cancer Diagnosis and Treatment
- Effects of Radiation Exposure
- Advanced MRI Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Nuclear Physics and Applications
- Electron and X-Ray Spectroscopy Techniques
- Visual perception and processing mechanisms
- Radiation Shielding Materials Analysis
- Lung Cancer Treatments and Mutations
- Atomic and Subatomic Physics Research
- Radiopharmaceutical Chemistry and Applications
- MRI in cancer diagnosis
- Advanced biosensing and bioanalysis techniques
- Ultrasound and Hyperthermia Applications
Western University
2013-2023
London Health Sciences Centre
2009-2020
Cancer Care Ontario
1998-2018
Institute Mutualiste Montsouris
2017
London Cancer
2012-2016
Philips (United States)
2016
The University of Melbourne
2011-2013
Australian College of Optometry
2011-2012
Lawson Health Research Institute
2012
Regional Cancer Center
2005-2011
Arrays were generated using the Monte Carlo method representing energy absorbed throughout waterlike phantoms from charged particles and scatter radiation set in motion by primary interactions at one location. The resulting "dose spread arrays" normalized to collision fraction of kinetic released photons. These arrays are convolved with relative fluence interacting a phantom obtain three-dimensional dose distributions. gives good agreement for 15-MV x-ray electronic disequilibrium...
The EGS Monte Carlo code was used to generate photon energy deposition kernels which describe the deposited by charged particles set in motion primary, first scattered, second multiple scattered and bremsstrahlung plus annihilation photons. These were calculated for a water medium irradiated with monoenergetic photons energies range 0.1-50 MeV. In addition primary kernels, particle transport further characterised computing effective centre of voxels, penetration depth, radius lateral...
In recent years, magnetic‐resonance imaging of gelatin doped with the Fricke solution has been applied to direct measurement three‐dimensional (3D) radiation dose distributions. However, 3D distribution can also be imaged more economically and efficiently using method optical absorption computed tomography. This is accomplished by first preparing a matrix containing radiochromic dye mapping radiation‐induced local change in coefficient. Ferrous–Benzoic–Xylenol (FBX) was choice for this...
A computerized tomography (CT) reconstruction technique has been used to make quantitative measurements of the size and shape focal spot in medical linear accelerators. Using this technique, we have measured spots a total nine accelerators, including (i) two Varian Clinac 2100c's, (ii) Atomic Energy Canada Ltd. (AECL) Therac‐25's, (iii) AECL Therac 6's, (iv) Siemens KD‐2, (v) 600c (4 MV), (vi) an Therac‐20. Some these were monitored for changes over 2‐yr period. It found that source varies...
The goal of this research is to calculate the daily and cumulative dose distribution received by radiotherapy patient while accounting for variable anatomy, tracking delivered tissue elements (voxels) that move within patient. Non-linear image registration techniques (i.e., thin-plate splines) are used along with a conventional treatment planning system combine distributions computed each 3D tomography (CT) study taken during treatment. For clinical prostate case, we demonstrate there...
We have measured the radiation dose in simple heterogeneous phantoms and compared our results with those obtained by various methods of computation. Dose data were both within distal to simulated regions lung order test ratio tissue–air ratios (TAR), Batho, equivalent TAR methods. These procedures are used routinely manual computer‐aided planning therapy, but been validated primarily for cobalt‐60 radiation. Tests performed 6‐ 15‐MV x rays reveal that incorrect doses can be computed or near...
Radiation-sensitive hydrogels offer the capability of verifying intricate dose distributions in three-dimensional (3D) space conveniently a single measurement with sub-millimetre spatial resolution. In this study, new radiochromic hydrogel called leuco crystal violet (LCV) micelle gel is introduced. Upon irradiation, LCV converts to (CV(+)). Triton X-100 micelles are used provide required hybrid-interfacing environment dissolve LCV. The diffusion coefficient has been measured be 0.036 +/-...
Two new Fricke dosimeter gel systems with low diffusion rates have been developed for 3D radiation dosimetry purposes. Both consist of a solution 20% (by weight) polyvinyl alcohol (PVA) in 50 mM H2 SO4solution 0.4 ferrous ammonium sulphate and xylenol orange (FX). The difference the two gels is way that gelation process was initiated: either by bringing temperature to (a) +5 °C or (b) -20 before returning them room temperature. These are termed `hydrogel' `cryogel', respectively. hydrogel...
The physical characteristics of x rays scattered by the patient and reaching imaging detector, as well their effect on verification (portal) image quality, were investigated for megavoltage (0.1–20 MeV) x‐ray beams. Monte Carlo calculations experimental measurements used to characterize how scatter primary fluences at detector plane influenced scattering geometry energy spectrum incident beam. calculated differentiated according photon process. Scatter fractions measured a medical linear...
An extrafocal source model has been developed to explain the dependence of head scatter and beam penumbra on field size. In this model, x‐ray a medical linear accelerator is described by two components: small but intense focal component; broadly distributed component low intensity. The so large that it can be “eclipsed” field‐defining collimators. Extrafocal radiation was found account for 12% energy fluence central axis 6 MV from Varian Clinac 2100c accelerator. Head factors were calculated...
A Compton scatter scanner has been developed to image electron density distributions of transverse body sections. The imaging performance this device measured and compared with calculated limits the present capabilities X-ray computer tomographic (CT) scanners. use images in radiotherapy dose calculations investigated a calibration curve also from patient convert CT number data densities for tissues vivo. Images have produced spatial resolution 0.5 cm an accuracy 4.3% radiation 0.11 Gy (11...
Convolution methods have been used to model the effect of geometric uncertainties on dose delivery in radiation therapy. assumes shift invariance distribution. Internal inhomogeneities and surface curvature lead violations this assumption. The magnitude error resulting from violation is not well documented. This issue addressed by comparing distributions calculated using method with obtained Direct Simulation. A comparison conventional Static was also made analysis performed for phantom...
The subject contrast of bony anatomy in megavoltage medical radiographs is very low, making detection landmarks difficult if additional noise sources are introduced into the images. One source noise, which inherent to x‐ray process, x ‐ ray energy absorption . X‐ray results from variations amount deposited imaging detector per interacting ray. These increase content image. In this study, EGS4 Monte Carlo simulations interactions metal plate phosphor screen detectors have been performed...
Dose distributions were measured and computed within inhomogeneous phantoms irradiated with beams of electrons having initial energies 10 18 MeV. The measurements made a small p-type silicon diode the calculations performed using pencil beam algorithm developed originally at M D Anderson Hospital (MDAH). This algorithm, which is available commercially on many radiotherapy planning computers, based Fermi-Eyges theory electron transport. used in this work composed water into two-...
The dosimetry of small fields as used in stereotactic radiotherapy, radiosurgery and intensity-modulated radiation therapy can be challenging inaccurate due to partial volume averaging effects possible disruption charged particle equilibrium. Consequently, there exists a need for an integrating, tissue equivalent dosimeter with high spatial resolution avoid perturbing the beam artificially broadening measured penumbra. In this work, radiochromic ferrous xylenol-orange (FX) leuco crystal...
The electron density (e cm-3) of a tissue sample can be determined by measuring the fluence photons which it Compton scatters from narrow incident beam X- or gamma -radiation. physics scatter tomography is examined with emphasis on transverse section scanning. two major limitations technique, attenuation single photon (of interest), and contamination this multiply-scattered photons, are studied corrective procedures proposed. methods described applied to simple test phantom; concluded that...
The practice of diagnostic x-ray imaging has been transformed with the emergence digital detector technology. Although systems offer many practical advantages over conventional film-based systems, their spatial resolution performance can be a limitation. authors present Monte Carlo study to determine fundamental limits caused by interactions in four converter materials: Amorphous silicon , amorphous selenium, cesium iodide, and lead iodide. "x-ray interaction" modulation transfer function...
Freshly prepared radiochromic ferrous xylenol-orange (FX) gels optically scanned with a light source exhibit threshold dose response that is thermally and wavelength dependent. Correction for this leads to accurate calibration better reproducibility in multiple fraction radiation exposures. The objective of study was determine the cause effect control it through improved procedures. results systematic investigation into chemical revealed impurities within various FX gel constituents (i.e....