Medical Biophysics Commons^™

Hyperpolarized 3he Functional Magnetic Resonance Imaging Of Bronchoscopic Airway Bypass In Chronic Obstructive Pulmonary Disease., Lindsay Mathew, Miranda Kirby, Donald Farquhar, Christopher Licskai, Giles Santyr, Roya Etemad-Rezai, Grace Parraga, David G Mccormack

Medical Biophysics Publications

A 73-year-old exsmoker with Global initiative for chronic Obstructive Lung Disease stage III chronic obstructive pulmonary disease underwent airway bypass (AB) as part of the Exhale Airway Stents for Emphysema (EASE) trial, and was the only EASE subject to undergo hyperpolarized 3He magnetic resonance imaging for evaluation of lung function pre- and post-AB. 3He magnetic resonance imaging was acquired twice previously (32 and eight months pre-AB) and twice post-AB (six and 12 months post-AB). Six months post-AB, his increase in forced vital capacity was

Modeling Stochastic And Spatial Heterogeneity In A Human Airway Tree To Determine Variation In Respiratory System Resistance, Del Leary, Swati A Bhatawadekar, Grace Parraga, Geoffrey N Maksym

Medical Biophysics Publications

Asthma is a variable disease with changes in symptoms and airway function over many time scales. Airway resistance (Raw) is variable and thought to reflect changes in airway smooth muscle activity, but just how variation throughout the airway tree and the influence of gas distribution abnormalities affect Raw is unclear. We used a multibranch airway lung model to evaluate variation in airway diameter size, the role of coherent regional variation, and the role of gas distribution abnormalities on mean Raw (Raw) and variation in Raw as described by the SD (SDRaw). We modified an anatomically correct airway tree, provided by …

Chest Mri In Children: Why Bother?, Amir M Owrangi, Grace Parraga

Medical Biophysics Publications

In this issue of Respirology, Montella and colleagues ask this question: How does high‐field chest MRI compare with CT of children with non‐cystic fibrosis (CF) lung disease? In an important extension of the first description of this study where they compared MRI and CT with pulmonary function measurements, the authors evaluated how widely‐used chest CT and almost never‐utilized lung MRI compare for diagnostic imaging of chronic lung disease. Here they show that high‐field (3Tesla as compared with the 1.5Tesla clinical standard) thoracic MRI has high reliability and good‐to‐excellent agreement with CT, definitively answering the important question at hand; their results …

Chronic Obstructive Pulmonary Disease: Quantification Of Bronchodilator Effects By Using Hyperpolarized ³He Mr Imaging, Miranda Kirby, Lindsay Mathew, Mohammadreza Heydarian, Roya Etemad-Rezai, David G Mccormack, Grace Parraga

Medical Biophysics Publications

PURPOSE: To evaluate short-acting bronchodilator effects in chronic obstructive pulmonary disease (COPD) by using hyperpolarized helium 3 (³He) magnetic resonance (MR) imaging, spirometry, and plethysmography.

MATERIALS AND METHODS: Fourteen ex-smokers with COPD provided written informed consent to a local ethics board-approved and Health Insurance and Portability Accountability Act-compliant protocol and underwent hyperpolarized ³He and hydrogen 1 MR imaging, spirometry, and plethysmography before and a mean of 25 minutes ± 2 (standard deviation) after administration of 400 μg salbutamol. Distribution of ³He gas was evaluated by using semiautomated segmentation of ³He voxel intensities, where cluster 1 represented regions of signal void …

Three-Dimensional Ultrasound Scanning, Aaron Fenster, Grace Parraga, Jeff Bax

Medical Biophysics Publications

The past two decades have witnessed developments of new imaging techniques that provide three-dimensional images about the interior of the human body in a manner never before available. Ultrasound (US) imaging is an important cost-effective technique used routinely in the management of a number of diseases. However, two-dimensional viewing of three-dimensional anatomy, using conventional two-dimensional US, limits our ability to quantify and visualize the anatomy and guide therapy, because multiple two-dimensional images must be integrated mentally. This practice is inefficient, and may lead to variability and incorrect diagnoses. Investigators and companies have addressed these limitations by developing three-dimensional US techniques. …

Imaging Of Lung Function Using Hyperpolarized Helium-3 Magnetic Resonance Imaging: Review Of Current And Emerging Translational Methods And Applications, Sean Fain, Mark L Schiebler, David G Mccormack, Grace Parraga

Medical Biophysics Publications

During the past several years there has been extensive development and application of hyperpolarized helium-3 (HP (3)He) magnetic resonance imaging (MRI) in clinical respiratory indications such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, radiation-induced lung injury, and transplantation. This review focuses on the state-of-the-art of HP (3)He MRI and its application to clinical pulmonary research. This is not an overview of the physics of the method, as this topic has been covered previously. We focus here on the potential of this imaging method and its challenges in demonstrating new types of information that has the potential to influence clinical …

Hyperpolarized (3)He Magnetic Resonance Imaging-Derived Pulmonary Pressure-Volume Curves, Stephen Choy, Andrew Wheatley, David G Mccormack, Grace Parraga

Medical Biophysics Publications

We aimed to evaluate the potential for the use of hyperpolarized helium-3 magnetic resonance imaging (MRI) apparent diffusion coefficient (ADC) surrogates of alveolar size, together with literature-based morphological parameters in a theoretical model of lung mechanics to simulate noninvasive transpulmonary pressure-volume curves. Fourteen ex-smokers with chronic obstructive pulmonary disease (COPD) (n = 8 stage II, n = 6 stage III/IV COPD) and five age-matched never-smokers, provided written, informed consent and were evaluated at baseline and 26 + or - 2 mo later (n = 15 subjects) using plethysmography, spirometry, and (3)He MRI at 3.0 T. Total lung capacity, residual volume, …

Chronic Obstructive Pulmonary Disease: Longitudinal Hyperpolarized (3)He Mr Imaging, Miranda Kirby, Lindsay Mathew, Andrew Wheatley, Giles E Santyr, David G Mccormack, Grace Parraga

Medical Biophysics Publications

PURPOSE: To quantitatively evaluate a small pilot group of ex-smokers with chronic obstructive pulmonary disease (COPD) and healthy volunteers during approximately 2 years by using hyperpolarized helium 3 ((3)He) magnetic resonance (MR) imaging.

MATERIALS AND METHODS: All subjects provided written informed consent to the study protocol, which was approved by the local research ethics board and Health Canada and was compliant with the Personal Information Protection and Electronic Documents Act and HIPAA. Hyperpolarized (3)He MR imaging, hydrogen 1 MR imaging, spirometry, and plethysmography were performed in 15 ex-smokers with COPD and five healthy volunteers (with the same mean age and …

Analysis Of Carotid Lumen Surface Morphology Using Three-Dimensional Ultrasound Imaging, Bernard Chiu, Vadim Beletsky, J David Spence, Grace Parraga, Aaron Fenster

Medical Biophysics Publications

Carotid plaque surface irregularity and ulcerations play an important role in the risk of ischemic stroke. Ulcerated or fissured plaque, characterized by irregular surface morphology, exposes thrombogenic materials to the bloodstream, possibly leading to life- or brain-threatening thrombosis and embolization. Therefore, the quantification of plaque surface irregularity is important to identify high-risk plaques that would likely lead to vascular events. Although a number of studies have characterized plaque surface irregularity using subjective classification schemes with two or more categories, only a few have quantified surface irregularity using an objective and continuous quantity, such as Gaussian or mean curvature. In this …

Nonrigid Registration Of Three-Dimensional Ultrasound And Magnetic Resonance Images Of The Carotid Arteries, Nuwan D Nanayakkara, Bernard Chiu, Abbas Samani, J David Spence, Jagath Samarabandu, Grace Parraga, Aaron Fenster

Medical Biophysics Publications

Atherosclerosis at the carotid bifurcation can result in cerebral emboli, which in turn can block the blood supply to the brain causing ischemic strokes. Noninvasive imaging tools that better characterize arterial wall, and atherosclerotic plaque structure and composition may help to determine the factors which lead to the development of unstable lesions, and identify patients at risk of plaque disruption and stroke. Carotid magnetic resonance (MR) imaging allows for the characterization of carotid vessel wall and plaque composition, the characterization of normal and pathological arterial wall, the quantification of plaque size, and the detection of plaque integrity. On the other …

Scan-Rescan And Intra-Observer Variability Of Magnetic Resonance Imaging Of Carotid Atherosclerosis At 1.5 T And 3.0 T, Arvin Vidal, Yves Bureau, Trevor Wade, J David Spence, Brian K Rutt, Aaron Fenster, Grace Parraga

Medical Biophysics Publications

Carotid atherosclerosis measurements for eight subjects at baseline and 14 +/- 2 days later were examined using 1.5 T and 3.0 T magnetic resonance imaging (MRI). A single observer blinded to field strength, subject and timepoint manually segmented carotid artery wall and lumen boundaries in randomized images in five measurement trials. Mean increases in the signal-to-noise ratios (SNR) for T1-weighted images acquired at 3.0 T compared to 1.5 T were 90% (scan) and 80% (rescan). Despite significantly improved SNR and contrast-to-noise ratios (CNR) for images acquired at 3.0 T, vessel wall volume (VWV) intra-observer variability was not significantly different using …

Mapping And Quantifying Hyperpolarized 3he Magnetic Resonance Imaging Apparent Diffusion Coefficient Gradients, Andrea Evans, David G Mccormack, Giles Santyr, Grace Parraga

Medical Biophysics Publications

We measured hyperpolarized 3He magnetic resonance imaging (MRI) apparent diffusion coefficients (ADC) and quantified ADC gradients in each three-by-three voxel region of interest (ROI). Such local ADC gradients can be represented in vector maps showing the magnitude (|G3x3|) and direction of ADC gradients, providing a qualitative visualization tool and quantitative measurement of airway and air space heterogeneity. Twenty-four subjects (15 male, mean age=67+/-7 yr) with global initiative for chronic obstructive lung disease (GOLD) stage II (n=9, mean age 68+/-6 yr), GOLD stage III chronic obstructive pulmonary disease (COPD; n=7, mean age 67+/-8 yr), and age-matched healthy volunteers (n=8, mean age …

Quantification Of Carotid Vessel Wall And Plaque Thickness Change Using 3d Ultrasound Images, Bernard Chiu, Micaela Egger, J David Spence, Grace Parraga, Aaron Fenster

Medical Biophysics Publications

Quantitative measurements of carotid plaque burden progression or regression are important in monitoring patients and in evaluation of new treatment options. 3D ultrasound (US) has been used to monitor the progression or regression of carotid artery plaques. This paper reports on the development and application of a method used to analyze changes in carotid plaque morphology from 3D US. The technique used is evaluated using manual segmentations of the arterial wall and lumen from 3D US images acquired in two imaging sessions. To reduce the effect of segmentation variability, segmentation was performed five times each for the wall and lumen. …