Medical Biophysics Commons^™

One, Two And Three-Dimensional Ultrasound Measurements Of Carotid Atherosclerosis Before And After Cardiac Rehabilitation: Preliminary Results Of A Randomized Controlled Trial., Tamas J Lindenmaier, Daniel N Buchanan, Damien Pike, Tim Hartley, Robert D Reid, J David Spence, Richard Chan, Michael Sharma, Peter L Prior, Neville Suskin, Grace Parraga

Medical Biophysics Publications

BACKGROUND: It is still not known how patients who are post-transient ischemic attack (TIA) or post-stroke might benefit from prospectively planned comprehensive cardiac rehabilitation (CCR). In this pilot evaluation of a larger ongoing randomized-controlled-trial, we evaluated ultrasound (US) measurements of carotid atherosclerosis in subjects following TIA or mild non-disabling stroke and their relationship with risk factors before and after 6-months of CCR.

METHODS: Carotid ultrasound (US) measurements of one-dimensional intima-media-thickness (IMT), two-dimensional total-plaque-area (TPA), three-dimensional total-plaque-volume (TPV) and vessel-wall-volume (VWV) were acquired before and after 6-months CCR for 39 subjects who had previously experienced a TIA and provided written informed …

Progression Of Carotid Plaque Volume Predicts Cardiovascular Events, Thapat Wannarong, Grace Parraga, Daniel Buchanan, Aaron Fenster, Andrew A House, Daniel G Hackam, J David Spence

Medical Biophysics Publications

BACKGROUND AND PURPOSE: Carotid ultrasound evaluation of intima-media thickness (IMT) and plaque burden has been used for risk stratification and for evaluation of antiatherosclerotic therapies. Increasing evidence indicates that measuring plaque burden is superior to measuring IMT for both purposes. We compared progression/regression of IMT, total plaque area (TPA), and total plaque volume (TPV) as predictors of cardiovascular outcomes.

METHODS: IMT, TPA, and TPV were measured at baseline in 349 patients attending vascular prevention clinics; they had TPA of 40 to 600 mm(2) at baseline to qualify for enrollment. Participants were followed up for ≤5 years (median, 3.17 years) to …

Three-Dimensional Segmentation Of Three-Dimensional Ultrasound Carotid Atherosclerosis Using Sparse Field Level Sets., E Ukwatta, J Yuan, D Buchanan, B Chiu, J Awad, W Qiu, G Parraga, A Fenster

Medical Biophysics Publications

PURPOSE: Three-dimensional ultrasound (3DUS) vessel wall volume (VWV) provides a 3D measurement of carotid artery wall remodeling and atherosclerotic plaque and is sensitive to temporal changes of carotid plaque burden. Unfortunately, although 3DUS VWV provides many advantages compared to measurements of arterial wall thickening or plaque alone, it is still not widely used in research or clinical practice because of the inordinate amount of time required to train observers and to generate 3DUS VWV measurements. In this regard, semiautomated methods for segmentation of the carotid media-adventitia boundary (MAB) and the lumen-intima boundary (LIB) would greatly improve the time to train …

On The Role Of Abnormal Dl(Co) In Ex-Smokers Without Airflow Limitation: Symptoms, Exercise Capacity And Hyperpolarised Helium-3 Mri, Miranda Kirby, Amir Owrangi, Sarah Svenningsen, Andrew Wheatley, Harvey O Coxson, Nigel A M Paterson, David G Mccormack, Grace Parraga

Medical Biophysics Publications

BACKGROUND: The functional effects of abnormal diffusing capacity for carbon monoxide (DLCO) in ex-smokers without chronic obstructive pulmonary disease (COPD) are not well understood.

OBJECTIVE: We aimed to evaluate and compare well established clinical, physiological and emerging imaging measurements in ex-smokers with normal spirometry and abnormal DLCO with a group of ex-smokers with normal spirometry and DLCO and ex-smokers with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I COPD.

METHODS: We enrolled 38 ex-smokers and 15 subjects with stage I COPD who underwent spirometry, plethysmography, St George's Respiratory Questionnaire (SGRQ), 6 min Walk Test (6MWT), x-ray CT and …

A Magnetic-Resonance-Imaging-Compatible Remote Catheter Navigation System., Mohammad Ali Tavallaei, Yogesh Thakur, Syed Haider, Maria Drangova

Medical Biophysics Publications

A remote catheter navigation system compatible with magnetic resonance imaging (MRI) has been developed to facilitate MRI-guided catheterization procedures. The interventionalist's conventional motions (axial motion and rotation) on an input catheter - acting as the master - are measured by a pair of optical encoders, and a custom embedded system relays the motions to a pair of ultrasonic motors. The ultrasonic motors drive the patient catheter (slave) within the MRI scanner, replicating the motion of the input catheter. The performance of the remote catheter navigation system was evaluated in terms of accuracy and delay of motion replication outside and within …

Chronic Obstructive Pulmonary Disease: More Imaging, More Phenotyping...Better Care?, Damien Pike, Grace Parraga

Medical Biophysics Publications

No abstract provided.

Evidence Of Adult Lung Growth In Humans., Miranda Kirby, David G Mccormack, Grace Parraga

Medical Biophysics Publications

A 33-year-old woman underwent a right-sided pneumonectomy in 1995 for treatment of a lung adenocarcinoma. As expected, there was an abrupt decrease in her vital capacity, but unexpectedly, it increased during the subsequent 15 years. Serial computed tomographic (CT) scans showed progressive enlargement of the remaining left lung and an increase in tissue density. Magnetic resonance imaging (MRI) with the use of hyperpolarized helium-3 gas showed overall acinar-airway dimensions that were consistent with an increase in the alveolar number rather than the enlargement of existing alveoli, but the alveoli in the growing lung were shallower than in normal lungs. This …

Hyperpolarized 3he And 129xe Mr Imaging In Healthy Volunteers And Patients With Chronic Obstructive Pulmonary Disease, Miranda Kirby, Sarah Svenningsen, Amir Owrangi, Andrew Wheatley, Adam Farag, Alexei Ouriadov, Giles E Santyr, Roya Etemad-Rezai, Harvey O Coxson, David G Mccormack, Grace Parraga

Medical Biophysics Publications

PURPOSE: To quantitatively compare hyperpolarized helium 3 (3He) and xenon 129 (129Xe) magnetic resonance (MR) images obtained within 5 minutes in healthy volunteers and patients with chronic obstructive pulmonary disease (COPD) and to evaluate the correlations between 3He and 129Xe MR imaging measurements and those from spirometry and plethysmography.

MATERIALS AND METHODS: This study was approved by an ethics board and compliant with HIPAA. Written informed consent was obtained from all subjects. Eight healthy volunteers and 10 patients with COPD underwent MR imaging, spirometry, and plethysmography. Ventilation defect percentages (VDPs) at 3He and 129Xe imaging were obtained by using semiautomated …

What Can Computed Tomography And Magnetic Resonance Imaging Tell Us About Ventilation?, Brett A Simon, David W Kaczka, Alexander A Bankier, Grace Parraga

Medical Biophysics Publications

This review provides a summary of pulmonary functional imaging approaches for determining pulmonary ventilation, with a specific focus on multi-detector x-ray computed tomography and magnetic resonance imaging (MRI). We provide the important functional definitions of pulmonary ventilation typically used in medicine and physiology and discuss the fact that some of the imaging literature describes gas distribution abnormalities in pulmonary disease that may or may not be related to the physiological definition or clinical interpretation of ventilation. We also review the current state-of-the-field in terms of the key physiological questions yet unanswered related to ventilation and gas distribution in lung disease. …

Shift Work And Vascular Events: Systematic Review And Meta-Analysis., Manav V Vyas, Amit X Garg, Arthur V Iansavichus, John Costella, Allan Donner, Lars E Laugsand, Imre Janszky, Marko Mrkobrada, Grace Parraga, Daniel G Hackam

Medical Biophysics Publications

OBJECTIVE: To synthesise the association of shift work with major vascular events as reported in the literature.

DATA SOURCES: Systematic searches of major bibliographic databases, contact with experts in the field, and review of reference lists of primary articles, review papers, and guidelines.

STUDY SELECTION: Observational studies that reported risk ratios for vascular morbidity, vascular mortality, or all cause mortality in relation to shift work were included; control groups could be non-shift ("day") workers or the general population.

DATA EXTRACTION: Study quality was assessed with the Downs and Black scale for observational studies. The three primary outcomes were myocardial infarction, …

Quantitative Pulmonary Imaging Using Computed Tomography And Magnetic Resonance Imaging, George R Washko, Grace Parraga, Harvey O Coxson

Medical Biophysics Publications

Measurements of lung function, including spirometry and body plethesmography, are easy to perform and are the current clinical standard for assessing disease severity. However, these lung functional techniques do not adequately explain the observed variability in clinical manifestations of disease and offer little insight into the relationship of lung structure and function. Lung imaging and the image-based assessment of lung disease has matured to the extent that it is common for clinical, epidemiologic and genetic investigation to have a component dedicated to image analysis. There are several exciting imaging modalities currently being used for the non-invasive study of lung anatomy …

Evaluating Bronchodilator Effects In Chronic Obstructive Pulmonary Disease Using Diffusion-Weighted Hyperpolarized Helium-3 Magnetic Resonance Imaging, Miranda Kirby, Mohammadreza Heydarian, Andrew Wheatley, David G Mccormack, Grace Parraga

Medical Biophysics Publications

The objective of this study was to evaluate the regional effects of bronchodilator administration in chronic obstructive pulmonary disease (COPD) using hyperpolarized helium-3 ((3)He) MRI apparent diffusion coefficient (ADC). Ten COPD ex-smokers provided written, informed consent and underwent diffusion-weighted, hyperpolarized (3)He MRI, spirometry, and plethysmography before and 25 ± 2 min after bronchodilator administration. Pre- and postsalbutamol whole-lung (WL) ADC maps were generated and registered together to identify the lung regions containing the (3)He signal at both time points, and mean ADC within those regions of interest (ROI) was determined for a measurement of previously ventilated ROI ADC (ADC(P)). Lung …

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 …

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 …

Schedule For Ct Image Guidance In Treating Prostate Cancer With Helical Tomotherapy., G Beldjoudi, S Yartsev, G Bauman, Jerry J. Battista Dr., Jacob Van Dyk

Oncology Publications

The aim of this study was to determine the effect of reducing the number of image guidance sessions and patient-specific target margins on the dose distribution in the treatment of prostate cancer with helical tomotherapy. 20 patients with prostate cancer who were treated with helical tomotherapy using daily megavoltage CT (MVCT) imaging before treatment served as the study population. The average geometric shifts applied for set-up corrections, as a result of co-registration of MVCT and planning kilovoltage CT studies over an increasing number of image guidance sessions, were determined. Simulation of the consequences of various imaging scenarios on the dose …

The Effects Of Field-Of-View And Patient Size On Ct Numbers From Cone-Beam Computed Tomography., Katrina Y T Seet, Arvand Barghi, Slav Yartsev, Jacob Van Dyk

Oncology Publications

Cone-beam computed tomography (CBCT) is used for patient alignment before treatment and is ideal for use in adaptive radiotherapy to account for tumor shrinkage, organ deformation and weight loss. However, CBCT images are prone to artifacts such as streaking and cupping effects, reducing image quality and CT number accuracy. Our goal was to determine the optimum combination of cone-beam imaging options to increase the accuracy of image CT numbers. Several phantoms with and without inserts of known relative electron densities were imaged using the Varian on-board imaging system. It was found that CT numbers are most influenced by the selection …

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 …

Adaptive Radiation Therapy For Localized Mesothelioma With Mediastinal Metastasis Using Helical Tomotherapy., James Renaud, Slav Yartsev, A Rashid Dar, Jacob Van Dyk

Oncology Publications

The purpose of this study was to compare 2 adaptive radiotherapy strategies with helical tomotherapy. A patient having mesothelioma with mediastinal nodes was treated using helical tomotherapy with pretreatment megavoltage CT (MVCT) imaging. Gross tumor volumes (GTVs) were outlined on every MVCT study. Two alternatives for adapting the treatment were investigated: (1) keeping the prescribed dose to the targets while reducing the dose to the OARs and (2) escalating the target dose while maintaining the original level of healthy tissue sparing. Intensity modulated radiotherapy (step-and-shoot IMRT) and 3D conformal radiotherapy (3DCRT) plans for the patient were generated and compared. The …

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 …

Consistency Check Of Planned Adaptive Option On Helical Tomotherapy., M Schirm, S Yartsev, G Bauman, Jerry J. Battista Dr., Jacob Van Dyk

Oncology Publications

This study aims to evaluate a new Planned Adaptive software (TomoTherapy Inc., Madison, WI) of the helical tomotherapy system by retrospective verification and adaptive re-planning of radiation treatment. Four patients with different disease sites (brain, nasal cavity, lungs, prostate) were planned in duplicate using the diagnostic planning kVCT data set and MVCT studies of the first treatment fraction with the same optimization parameters for both plan types. The dosimetric characteristics of minimum, maximum, and mean dose to the targets as well as to organs at risk were compared. Both sets of plans were used for calculation of dose distributions in …

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. …

Adaptive Radiotherapy Planning On Decreasing Gross Tumor Volumes As Seen On Megavoltage Computed Tomography Images., Curtis Woodford, Slav Yartsev, R. Dar, Glenn Bauman, Jacob Van Dyk

Oncology Publications

PURPOSE: To evaluate gross tumor volume (GTV) changes for patients with non-small-cell lung cancer by using daily megavoltage (MV) computed tomography (CT) studies acquired before each treatment fraction on helical tomotherapy and to relate the potential benefit of adaptive image-guided radiotherapy to changes in GTV.

METHODS AND MATERIALS: Seventeen patients were prescribed 30 fractions of radiotherapy on helical tomotherapy for non-small-cell lung cancer at London Regional Cancer Program from Dec 2005 to March 2007. The GTV was contoured on the daily MVCT studies of each patient. Adapted plans were created using merged MVCT-kilovoltage CT image sets to investigate the advantages …