About
81
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Introduction
My research focuses on Stereotactic Radiotherapy and Radiosurgery, with recent interests in Radiomics and 3D Gel Dosimetry.
Current institution
Additional affiliations
September 2010 - present
BC Cancer - Kelowna
Position
- Senior Medical Physicist
Description
- Radiation Safety Officer & SABR Physics Lead
July 2014 - present
June 2014 - present
Education
September 1999 - April 2004
September 1997 - August 1999
September 1993 - April 1997
Publications
Publications (81)
The development of radiation-induced fibrosis after SABR can obscure follow-up images and delay detection of a local recurrence in early-stage lung cancer patients. The objective of this study was to develop a radiomics model for computer-assisted detection of local recurrence and fibrosis for an earlier timepoint (<1 year) after the SABR treatment...
Purpose
Deep learning‐based auto‐segmentation algorithms can improve clinical workflow by defining accurate regions of interest while reducing manual labor. Over the past decade, convolutional neural networks (CNNs) have become prominent in medical image segmentation applications. However, CNNs have limitations in learning long‐range spatial depend...
Objective. To develop and benchmark a novel 3D dose verification technique consisting of polymer gel dosimetry (PGD) with cone-beam-CT (CBCT) readout through a two-institution study. The technique has potential for wide and robust applicability through reliance on CBCT readout. Approach. Three treatment plans (3-field, TG119-C-shape spine, 4-target...
Purpose
To evaluate the feasibility of an open‐source, semi‐automated, and reproducible vertex placement tool to improve the efficiency of lattice radiotherapy (LRT) planning. We used polymer gel dosimetry with a Cone Beam CT (CBCT) readout to commission this LRT technique.
Material and methods
We generated a volumetric modulated arc therapy (VMAT...
A 74-year-old woman with pathologic T4a N1 M0 adenocarcinoma of the cecum, initially treated with right hemicolectomy, developed rising serum carcinoembryonic antigen levels while receiving adjuvant chemotherapy. Re-staging investigations demonstrated two soft tissue metastases in the right abdomen comprised of a retrocolic lesion immediately poste...
Purpose
This study evaluates the dosimetric and geometric precision of a virtual cone technique using CBCT‐based polymer gel dosimetry, enabling radiation delivery, and imaging readout within an identical spatial coordinate system.
Methods
We created a C# script for a virtual cone technique that generates a treatment plan with 10 gantry arcs at 0°...
Linac-based stereotactic radiosurgery (SRS) with planning target volume (PTV) margins <1 mm has become increasingly common in recent years. Optical surface imaging for surface-guided radiation therapy (SGRT) is often used for intra-fraction motion monitoring during these treatments to facilitate the use of a smaller PTV margin by providing real-tim...
3D polymer gel dosimetry is a promising means to verify complex radiation treatments such as stereotactic radiosurgery (SRS), as it provides both 3D dosimetric and spatial information. The purpose of the study is to use a polymer gel read-out with cone-beam computed tomography (CBCT) to commission Varian’s HyperArc ® -treatment planning and deliver...
Background
The recent trend toward 10 MV for volumetric radiotherapy treatment such as volumetric modulated arc therapy (VMAT), stereotactic radiosurgery (SRS), and stereotactic ablative body radiotherapy (SABR) introduces photoneutron production, with implications for non‐therapeutic patient dose and additional shielding requirements for treatment...
Background and purpose:
Stereotactic ablative radiotherapy (SABR) for oligometastases may improve survival, however concerns about safety remain. To mitigate risk of toxicity, target coverage was sacrificed to prioritize organs-at-risk (OARs) during SABR planning in the population-based SABR-5 trial. This study evaluated the effect of this practic...
Stereotactic body radiotherapy (SBRT) planning target volume (PTV) margins are influenced by multiple factors. Data is limited on intrafraction motion in bone SBRT, particularly non-spine lesions. We analyzed intrafraction motion in bone SBRT patients treated on a standard treatment couch without 6 degrees-of-freedom (6-DOF) correction. Extracrania...
Purpose: Stereotactic ablative radiotherapy (SABR) allows the
precise delivery of large radiation doses with smaller planning
target volume (PTV) margins than conventional radiotherapy.
PTV margins are influenced by uncertainties with immobilization,
image-guidance, and intrafraction motion among other factors.
There is limited data on the assessme...
Importance
After the publication of the landmark SABR-COMET trial, concerns arose regarding high-grade toxic effects of treatment with stereotactic ablative body radiotherapy (SABR) for oligometastases.
Objective
To document toxic effects of treatment with SABR in a large cohort from a population-based, provincial cancer program.
Design, Setting,...
Radiomics is an advanced image-processing framework, which extracts image features and considers them as biomarkers towards personalized medicine. Applications include disease detection, diagnosis, prognosis, and therapy response assessment/prediction. As radiation therapy aims for further individualized treatments, radiomics could play a critical...
Purpose/Objective(s)
After the publication of the landmark SABR-COMET trial, concerns were raised over toxicity of SABR for oligometastases. This population-based study was designed as a bridge from phase II to phase III trials, while assessing the toxicity profile of SABR in a larger cohort from a provincial cancer program.
Materials/Methods
From...
Survival from partial-body irradiation (PBI) may be limited by the development of the late lung injury response of pneumonitis. Herein we investigated the hypothesis that acute hematopoietic depletion alters the onset and severity of lung disease in a mouse model. To establish depletion, C3H/HeJ mice received 8 Gy PBI with shielding of only the tib...
Background
During the novel coronavirus disease 2019 (COVID-19) pandemic, cancer centers considered shortened courses of radiotherapy to minimize the risk of infectious exposure of patients and staff members. Amidst a pandemic, the process of implementing new treatment approaches can be particularly challenging in larger institutions with multiple...
Institutions use a range of different detector systems for patient-specific quality assurance (QA) measurements conducted to assure that the dose delivered by a patient's radiotherapy treatment plan matches the calculated dose distribution. However, the ability of different detectors to detect errors from different sources is often unreported. This...
Background:
Oligometastases refer to a state of disease where cancer has spread beyond the primary site, but is not yet widely metastatic, often defined as 1-3 or 1-5 metastases in number. Stereotactic ablative radiotherapy (SABR) is an emerging radiotherapy technique to treat oligometastases that require further prospective population-based toxic...
The aim of this study is to determine whether stereotactic body radiotherapy for multiple vertebral metastases treated with a single isocenter results in greater intrafraction errors than stereotactic body radiotherapy for single vertebral metastases and to determine whether the currently used spinal cord planning organ at risk volume and planning...
Purpose:Lung SABR patients are treated using Volumetrically Modulated Arc Therapy (VMAT), utilizing 2 arcs with Conebeam CT (CBCT) image-guidance prior to each arc. Intra-fraction imaging can prolong treatment time (up to 20%), and the aim of this study is to determine if it is necessary.
Methods:We utilize an in-house abdominal compression device...
Purpose: Stereotactic Ablative Radiotherapy (SABR) requires the delivery of a high biologically effective dose in only a few fractions. The Varian Truebeam has optional Flattening Filter Free (FFF) modes which greatly increase the dose rate and reduce treatment times. We previously commissioned the 6MV FFF beam (1400 MU/min) in Eclipse using Varian...
Purpose: Stereotactic Ablative Radiotherapy (SABR) requires the delivery of a high biologically effective dose in only a few fractions. The Varian Truebeam has optional Flattening Filter Free (FFF) modes which greatly increase the dose rate and reduce treatment times. We previously commissioned the 6MV FFF beam (1400 MU/min) in Eclipse using Varian...
Purpose: To evaluate intra-fraction motion during spine stereotactic body radiation therapy (SBRT) for patients immobilized in a thermoplastic mask or a dual vacuum body cushion system (BodyFIX). All patients were treated using the Elekta Axesse which is equipped with a 4 mm multi-leaf collimator, a kilovoltage cone-beam computed tomography (CBCT)...
Purpose:
To commission and benchmark a vendor-supplied (Varian Medical Systems) Monte Carlo phase-space data for the 6 MV flattening filter free (FFF) energy mode on a TrueBeam linear accelerator for the purpose of quality assurance of clinical volumetric modulated arc therapy (VMAT) treatment plans. A method for rendering the phase-space data com...
Purpose: Stereotactic Body Radiation Therapy (SBRT) requires the delivery of a high biologically effective dose in only a few fractions. These large doses per fraction can necessitate long treatment times. The Varian Truebeam is capable of RapidArc delivery and also has the optional Flattening Filter Free (FFF) modes which greatly increase the dose...
Purpose: The intent of spinal SBRT is to maximize the biological effective dose and improve local control, while sparing the adjacent spinal cord. We report on the spinal SBRT positional accuracy for multiple, consecutive vertebrae in a single course, using the Elekta Synergy-S and BodyFIX immobilization systems. Methods: After initial patient adju...
Purpose: To establish feasibility of performing quality assurance for Flattening Filter Free (FFF) RapidArc stereotactic body radiotherapy treatments (SBRT) on a TrueBeam LINAC using Monte Carlo simulations. Methods: Phase-space files for TrueBeam FFF photon beams were made available by Varian in IAEA-compliant format. Monte Carlo simulations were...
To evaluate the residual setup error and intrafraction motion following kilovoltage cone-beam CT (CBCT) image guidance, for immobilized spine stereotactic body radiotherapy (SBRT) patients, with positioning corrected for in all six degrees of freedom.
Analysis is based on 42 consecutive patients (48 thoracic and/or lumbar metastases) treated with a...
Spinal metastases are a relatively common manifestation in advanced cancer patients. Low-dose conventional radiotherapy has long been the mainstay of treatment under the assumption that patients have a limited life expectancy in the order of 3-6 months. However, with new developments in systemic therapies, patients are surviving longer than expecte...
Purpose: Spinal SBRT was originally developed for the retreatment of patients with disease progression. However, the indication has evolved to the up‐front treatment of spinal metasteses with the intent to maximize the biological effective dose and improve local control, while sparing the adjacent spinal cord. We report on the stability of our tech...
Stereotactic body radiotherapy (SBRT) is an emerging technique for spinal tumours that is a natural succession to brain radiosurgery. The spine is an ideal site for SBRT due to its relative immobility and the potential clinical benefits of high dose delivery, particularly to optimise local control and avoid disease progression that can result in sp...
The purpose of this investigation was to study apparatus-dependent dose distribution differences specific to spine stereotactic body radiotherapy (SBRT) treatment planning. This multi-institutional study was performed evaluating an image-guided robotic radiosurgery system (CK), intensity modulated protons (IMP), multileaf collimator (MLC) fixed-fie...
Purpose/Objective Stereotactic body radiation therapy (SBRT) of the spine requires the delivery of a high biologic effective dose to the target while sparing the adjacent spinal cord. Precise patient setup and immobilization are critical due to the steep dose gradient between the target and the cord. This study evaluates the setup precision and imm...
Purpose
Stereotactic body radiation therapy (SBRT) of the spine requires the delivery of a high biologic effective dose to the target while sparing the adjacent spinal cord. Precise patient setup and immobilization are critical due to the steep dose gradient between the target and the cord. This study evaluates the setup precision and immobilizatio...
A viable treatment option for inoperable early stage non‐small cell lung cancer is stereotactic body radiation therapy (SBRT) using 4DCT to incorporate tumour motion in the planning stage, hypofractionation, and cone beam CT for image guidance on the treatment unit. At our cancer centre, lung SBRT treatments were originally planned with no heteroge...
Our clinic routinely treats brain metastases with stereotactic radiosurgery using a 6 megavoltage (MV) linear accelerator, cones, and a surgically attached head frame. Four patients declined repeat radiosurgery for new lesions due to their previous discomfort and a fifth patient could not complete radiosurgery because of uncontrolled nausea. Instea...
Spine stereotactic body radiotherapy (SBRT) involves delivering 4-6 times the biologic effective dose than conventional external beam radiation in a precise and conformal fashion. Technically it is very demanding, requiring sophisticated treatment planning, body immobilization, intensity modulated radiotherapy, and image guidance. The aim is to imp...
Stereotactic body radiation therapy(SBRT) of the spine involves a high biologic effective dose to the target, while sparing the adjacent spinal cord. With a prescription of 24 Gy in 2–3 fractions (25 Gy in 5 fractions for re‐treatments) and the maximum point dose to the spinal cord limited to 1000–1400 cGy, the target coverage may be compromised to...
Radiation oncology has recently undergone a techno-
logic revolution in treatment delivery. The aim is to
improve cure rates while reducing toxicity in normal
tissue, and this entails significantly more complex
treatment. The progression from 2-dimensional to
3-dimensional treatment planning in external beam
radiation therapy (EBRT) was the fi...
Digital subtraction angiography is being supplanted by three‐dimensional imaging techniques in many clinical applications, leading to extensive use of maximum intensity projection (MIP) images to depict volumetric vascular data. The MIP algorithm produces intensity profiles that are different than conventional angiograms, and can also increase the...
Purpose: Three-dimensional Computed Rotational Angiography (CRA) provides high quality images of the complex anatomical structure of cerebral arteriovenous malformations (AVMs). The objective of this research is to combine CRA, as an alternative to bi-plane angiography for target definition, with innovative radiotherapy techniques for stereotactic...
Our goal was to determine the impact of the maximum intensity projection (MIP) algorithm on quantitative analysis used for diagnosis and treatment planning of extracranial arterial disease. We performed 3?D computed rotational angiography (CRA) on 26 consecutive symptomatic patients to verify an internal carotid artery (ICA) stenosis originally fou...
Clinical trials have shown that carotid endarterectomy reduces stroke risk in symptomatic individuals with severe internal carotid artery (ICA) stenosis. As a result of these trials, digital subtraction angiography (DSA) became a standard of reference for ICA stenosis diagnosis. Newer 3D techniques provide a larger number of views than DSA, which m...
Use of Mutual Information to register non-contrasted & contrasted 3D images of the cerebrovasculature
The gold standard for NASCET-type stenosis measurements is currently 2D digital subtraction angiography (DSA). In this paper, we evaluate the efficacy of 3D cone-beam, Volumetric Subtraction Angiography (VSA) for assessing internal carotid artery stenosis, by comparison with conventional DSA. VSA perspective maximum intensity projections (MIPs) and...
This study describes the development and evaluation of an appropriate methodology to study observer performance when comparing 2D and 3D angiographic techniques. 3D-CT angiograms were obtained from patients with cerebral aneurysms or occlusive carotid artery disease and perspective rendering of this 3D data was performed to produce maximum intensit...
Our goal is to improve the visualization of the intracranial vasculature during interventional procedures where radiographically dense objects would normally hinder clinical assessment. We describe our technique of Volumetric Subtraction Angiography (VSA), which removes bone, metal objects, and associated artifacts from the 3-D contrast-enhanced im...
A photon diffusion model has been developed to calculate the steady-state spatially resolved fluorescence from pencil beam excitation in layered tissue. The model allows the calculation of both the excitation reflectance and the fluorescence escape for an arbitrary continuous depth distribution of tissue optical properties and fluorophore concentra...
High-spin states of the nucleus 48Cr have been studied via particle-γ-γ spectroscopy, following the 28Si(28Si,2α) reaction. A 44-element particle-detector array was used to isolate 48Cr residues and to reduce γ-ray Doppler broadening. The collective band built upon the ground state has now been firmly established to spin 16+, the highest possible i...
