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David jaffray

Mohammad Rezaee, Richard P Hill, David A Jaffray
Given the distinct characteristics of low-energy electrons (LEEs), particularly at energies less than 30 eV, they can be applied to a wide range of therapeutic modalities to improve cancer treatment. LEEs have been shown to efficiently produce complex molecular damage resulting in substantial cellular toxicities. Since LEEs are produced in copious amounts from high-energy radiation beam, including photons, protons and ions; the control of LEE distribution can potentially enhance the therapeutic radio of such beams...
August 2017: Radiation Research
Chris McIntosh, Mattea Welch, Andrea McNiven, David A Jaffray, Thomas G Purdie
Recent works in automated radiotherapy treatment planning have used machine learning based on historical treatment plans to infer the spatial dose distribution for a novel patient directly from the planning image. We present a probabilistic, atlas-based approach which predicts the dose for novel patients using a set of automatically selected most similar patients (atlases). The output is a spatial dose objective, which specifies the desired dose-per-voxel, and therefore replaces the need to specify and tune dose-volume objectives...
July 6, 2017: Physics in Medicine and Biology
Michael Velec, Joanne L Moseley, Stina Svensson, Björn Hårdemark, David A Jaffray, Kristy K Brock
PURPOSE: The accuracy of deformable image registration tools can vary widely between imaging modalities and specific implementations of the same algorithms. A biomechanical model-based algorithm initially developed in-house at an academic institution was translated into a commercial radiotherapy treatment planning system and validated for multiple imaging modalities and anatomic sites. METHODS: Biomechanical deformable registration (Morfeus) is a geometry-driven algorithm based on the finite element method...
April 28, 2017: Medical Physics
Hamid Raziee, Fabio Y Moraes, Jure Murgic, Melvin L K Chua, Melania Pintilie, Peter Chung, Cynthia Ménard, Andrew Bayley, Mary Gospodarowicz, Padraig Warde, Tim Craig, Charles Catton, Robert G Bristow, David A Jaffray, Alejandro Berlin
BACKGROUND AND PURPOSE: Dose-escalated radiotherapy (DE) improves outcomes in localized prostate cancer (PCa). The impact of DE in the context of image-guided radiotherapy (IGRT) remains unknown. Herein, we determined outcomes of three sequential cohorts treated with progressive DE-IGRT. MATERIALS AND METHODS: We analyzed data from 1998 to 2012. Patients treated with radical radiotherapy were included, with three sequential institutional schedules: (A) 75.6Gy, (B) 79...
June 2017: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology
Yunhan Li, Yonghai Sun, David A Jaffray, John T W Yeow
Field emission (FE) uniformity and the mechanism of emitter failure of freestanding carbon nanotube (CNT) arrays have not been well studied due to the difficulty of observing and quantifying FE performance of each emitter in CNT arrays. Herein a field emission microscopy (FEM) method based on poly(methyl methacrylate) (PMMA) thin film is proposed to study the FE uniformity and CNT emitter failure of freestanding CNT arrays. FE uniformity of freestanding CNT arrays and different levels of FE current contributions from each emitter in the arrays are recorded and visualized...
April 18, 2017: Nanotechnology
Mattea L Welch, David A Jaffray
Previously developed MR-based three-dimensional (3D) Fricke-xylenol orange (FXG) dosimeters can provide end-to-end quality assurance and validation protocols for pre-clinical radiation platforms. FXG dosimeters quantify ionizing irradiation induced oxidation of Fe(2+) ions using pre- and post-irradiation MR imaging methods that detect changes in spin-lattice relaxation rates (R 1  =  [Formula: see text]) caused by irradiation induced oxidation of Fe(2+). Chemical changes in MR-based FXG dosimeters that occur over time and with changes in temperature can decrease dosimetric accuracy if they are not properly characterized and corrected...
April 21, 2017: Physics in Medicine and Biology
S Budithi, Rohit Dhawan, Andrew Cattell, Birender Balain, David Jaffray
PURPOSE: Multiple outcome measures exist to evaluate the outcomes of spinal decompression surgery; however, these tend to be complex and are difficult to express to the patient pre-operatively to accurately guide their expectations. We present outcomes, in terms of walking distance measurement, of a prospective single surgeon series of 76 consecutive patients with spinal stenosis. METHODS: 76 patients (mean age 68.8 years; 48-91 years) had decompression surgery using spinous process osteotomy...
February 2017: European Spine Journal
Helena Sandström, Caroline Chung, Hidefumi Jokura, Michael Torrens, David Jaffray, Iuliana Toma-Dasu
BACKGROUND AND PURPOSE: This study was an initiative of the Organs-at-Risk Standardization Working Group for evaluating the current degree of variability in the clinical practice of contouring organs-at-risk (OAR) for radiosurgery planning. MATERIALS AND METHODS: Imaging datasets for typical lesions (cavernous sinus meningioma, vestibular schwannoma, pituitary adenoma) treated with Leksell Gamma Knife Perfexion were circulated to 12 centers. Observers were asked to contour the target and OARs as per their standard clinical practice...
November 2016: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology
Edward Taylor, Ivan Yeung, Harald Keller, Bradley G Wouters, Michael Milosevic, David W Hedley, David A Jaffray
Compared to FDG, the signal of (18)F-labelled hypoxia-sensitive tracers in tumours is low. This means that in addition to the presence of hypoxic cells, transport properties contribute significantly to the uptake signal in static PET images. This sensitivity to transport must be minimized in order for static PET to provide a reliable standard for hypoxia quantification. A dynamic compartmental model based on a reaction-diffusion formalism was developed to interpret tracer pharmacokinetics and applied to static images of FAZA in twenty patients with pancreatic cancer...
November 21, 2016: Physics in Medicine and Biology
Caitlin Gillan, Meredith Giuliani, Nicole Harnett, Winnie Li, Laura A Dawson, Mary Gospodarowicz, David Jaffray
No abstract text is available yet for this article.
October 1, 2016: International Journal of Radiation Oncology, Biology, Physics
Shawn Stapleton, Daniel Mirmilshteyn, Jinzi Zheng, Christine Allen, David A Jaffray
The heterogeneous intra-tumoral accumulation of liposomes is a critical determinant of their efficacy. Both the chaotic tumor microcirculation and elevated IFP are linked to the heterogeneous intra-tumoral distribution of nanotechnology-based drug delivery systems such as liposomes. In the present study, the relationship between tumor microcirculation, elevated IFP, and accumulation of nanoparticles was investigated through in vivo experimentation. This was accomplished by evaluation of the tumor microcirculation using dynamic contrast enhanced computed tomography (DCE-CT) and measurement of tumor IFP using a novel image-guided robotic needle placement system connected to the micro-CT scanner...
2016: Journal of Visualized Experiments: JoVE
Winnie Li, Young-Bin Cho, Steve Ansell, Normand Laperriere, Cynthia Ménard, Barbara-Ann Millar, Gelareh Zadeh, Paul Kongkham, Mark Bernstein, David A Jaffray, Caroline Chung
PURPOSE: The present study used cone beam computed tomography (CBCT) to measure the inter- and intrafraction uncertainties for intracranial stereotactic radiosurgery (SRS) using the Leksell Gamma Knife (GK). METHODS AND MATERIALS: Using a novel CBCT system adapted to the GK radiosurgery treatment unit, CBCT images were acquired immediately before and after treatment for each treatment session within the context of a research ethics board-approved prospective clinical trial...
September 1, 2016: International Journal of Radiation Oncology, Biology, Physics
Marlee M Vandewouw, Dionne M Aleman, David A Jaffray
PURPOSE: Continuous dose delivery in radiation therapy treatments has been shown to decrease total treatment time while improving the dose conformity and distribution homogeneity over the conventional step-and-shoot approach. The authors develop an inverse treatment planning method for Gamma Knife® Perfexion™ that continuously delivers dose along a path in the target. METHODS: The authors' method is comprised of two steps: find a path within the target, then solve a mixed integer optimization model to find the optimal collimator configurations and durations along the selected path...
August 2016: Medical Physics
Yannan Nancy Dou, Michael Dunne, Huang Huang, Trevor Mckee, Martin C Chang, David A Jaffray, Christine Allen
Treatment efficacy of a heat-activated thermosensitive liposome formulation of cisplatin (CDDP), known as HTLC, was determined in xenograft models of non-small-cell lung carcinoma. The short-term impact of local hyperthermia (HT) on tumor morphology, microvessel density and local inflammatory response was also evaluated. The HTLC formulation in combination with local HT resulted in a significant advantage in therapeutic effect in comparison with free drug and a non-thermosensitive liposome formulation of CDDP (i...
November 2016: Journal of Drug Targeting
Marco Carlone, Tony Tadic, Harald Keller, Mohammad Rezaee, David Jaffray
PURPOSE: The surface dose in radiotherapy is subject to the physical properties of the radiation beam and collimator. The purpose of this work is to investigate the manipulation of surface dose using magnetic fields produced with a resistive magnet. Better understanding of the feasibility and mechanisms of altered surface dose could have important clinical applications where the surface dose must be increased for therapeutic goals, or reduced to enhance the therapeutic benefit. METHODS: A resistive magnet capable of generating a peak magnetic field up to 0...
June 2016: Medical Physics
Sarfraz Ahmad, Abdulkader Hamad, Amit Bhalla, Sarah Turner, Birender Balain, David Jaffray
PURPOSE: Lumbar spinal stenosis in the presence of degenerative spondylolisthesis is generally treated by means of surgery. The role of lumbar decompression without fusion is not clear. Therefore, the aim of this study was to assess whether patients who undergo decompression alone have a favourable outcome without the need for a subsequent fusion. METHODS: This is a prospective cohort study with single blinding of 83 consecutive patients with lumbar stenosis and degenerative spondylolisthesis treated by decompression, without fusion, using a spinous process osteotomy...
February 2017: European Spine Journal
Shawn Stapleton, David Jaffray, Michael Milosevic
The tumor microenvironment has an important influence on cancer biological and clinical behavior and radiation treatment (RT) response. However, RT also influences the tumor microenvironment in a complex and dynamic manner that can either reinforce or inhibit this response and the likelihood of long-term disease control in patients. It is increasingly evident that the interplay between RT and the tumor microenvironment can be exploited to enhance the accumulation and intra-tumoral distribution of nanoparticles, mediated by changes to the vasculature and stroma with secondary effects on hypoxia, interstitial fluid pressure (IFP), solid tissue pressure (STP), and the recruitment and activation of bone marrow-derived myeloid cells (BMDCs)...
January 15, 2017: Advanced Drug Delivery Reviews
Winnie Li, Gregory Bootsma, Oscar Von Schultz, Per Carlsson, Normand Laperriere, Barbara-Ann Millar, David Jaffray, Caroline Chung
UNLABELLED: OBJECTIVES : A non-invasive immobilization system consisting of a thermoplastic mask with image-guidance using cone-beam CT (CBCT) and infrared (IR) tracking has been developed to ensure minimal inter- and intra-fractional movement during Gamma Knife radiosurgery. Prior to clinical use for patients on a Gamma Knife, this study clinically evaluates the accuracy and stability of this novel immobilization system with image-guidance in patients treated with standard fractionated radiation therapy on a linear accelerator...
2016: Curēus
Karl Magtibay, Mohammadali Beheshti, Farbod Hosseyndoust Foomany, Stéphane Massé, Patrick F H Lai, Nima Zamiri, John Asta, Kumaraswamy Nanthakumar, David Jaffray, Sridhar Krishnan, Karthikeyan Umapathy
Current practices in studying cardiac arrhythmias primarily use electrical or optical surface recordings of a heart, spatially limited transmural recordings, and mathematical models. However, given that such arrhythmias occur on a 3D myocardial tissue, information obtained from such practices lack in dimension, completeness, and are sometimes prone to oversimplification. The combination of complementary Magnetic-Resonance Imaging (MRI)-based techniques such as Current Density Imaging (CDI) and Diffusion Tensor Imaging (DTI) could provide more depth to current practices in assessing the cardiac arrhythmia dynamics in entire cross sections of myocardium...
May 1, 2016: Computers in Biology and Medicine
Chun-Rong Wang, Javed Mahmood, Qin-Rong Zhang, Ali Vedadi, Jenny Warrington, Ning Ou, Robert G Bristow, David A Jaffray, Qing-Bin Lu
There is a compelling need to develop anticancer therapies that target cancer cells and tissues. Arising from innovative femtomedicine studies, a new class of non-platinum-based halogenated molecules (called FMD molecules) that selectively kill cancer cells and protect normal cells in treatments of multiple cancers has been discovered. This article reports the first observation of the radiosensitizing effects of such compounds in combination with ionizing radiation for targeted radiotherapy of a variety of cancers...
April 2016: Molecular Cancer Therapeutics
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