Medical Biophysics Commons^™

Evaluation Of Artifacts In Experimental Cine 4d Ct Acquisition Methods, Sarah Joy

Dissertations and Theses (Open Access)

Four-dimensional computed tomography (4D CT) has increased the accuracy of radiation treatment planning for patients in whom the extent of target motion is large. 4D CT has become a standard of care for radiation treatment simulation, allowing decreased motion artifacts and increased spatiotemporal localization of anatomical structures that move. However, motion artifacts may still remain. These artifacts, or artificial anatomic spatial distributions, add a systematic uncertainty to the treatment process and limit the accuracy of lung function images derived from CT. We proposed to reduce the motion artifacts in cine 4D CT by using three novel investigational 4D CT acquisition …

Characterization Of A Far-Red Analog Of Ghrelin For Imaging Ghs-R In P19-Derived Cardiomyocytes., Gregory A F Douglas, Rebecca Mcgirr, Carlie L Charlton, Dov B Kagan, Lisa M Hoffman, Leonard G Luyt, Savita Dhanvantari

Medical Biophysics Publications

Ghrelin and its receptor, the growth hormone secretagogue receptor (GHS-R), are expressed in the heart, and may function to promote cardiomyocyte survival, differentiation and contractility. Previously, we had generated a truncated analog of ghrelin conjugated to fluorescein isothiocyanate for the purposes of determining GHS-R expression in situ. We now report the generation and characterization of a far-red ghrelin analog, [Dpr(3)(octanoyl), Lys(19)(Cy5)]ghrelin (1-19), and show that it can be used to image changes in GHS-R in developing cardiomyocytes. We also generated the des-acyl analog, des-acyl [Lys(19)(Cy5)]ghrelin (1-19) and characterized its binding to mouse heart sections. Receptor binding affinity of Cy5-ghrelin as …

Brain Metastases From Breast Cancer: Lessons From Experimental Magnetic Resonance Imaging Studies And Clinical Implications., Donna Murrell, Paula J Foster, Ann F Chambers

Medical Biophysics Publications

Breast cancer that has metastasized to the brain presents difficult clinical challenges. This diagnosis comes with high mortality rates, largely due to complexities in early detection and ineffective therapies associated with both dormancy and impermeability of the blood-brain barrier (BBB). Magnetic resonance imaging (MRI) is the current gold standard for diagnosis and assessment of brain tumors. It has been used clinically to investigate metastatic development as well as monitor response to therapy. Here, we describe preclinical imaging strategies that we have used to study the development of brain metastases due to breast cancer. Using this approach, we have identified three …

The Next Move In Neuromodulation Therapy: A Question Of Timing., Julien Modolo, Alexandre Legros, Anne Beuter

Medical Biophysics Publications

No abstract provided.

What Are Ventilation Defects In Asthma?, Sarah Svenningsen, Miranda Kirby, Danielle Starr, Harvey O Coxson, Nigel A M Paterson, David G Mccormack, Grace Parraga

Medical Biophysics Publications

BACKGROUND: Hyperpolarised (3)He MRI provides a way to visualise regional pulmonary functional abnormalities that in asthma are thought to be related to airway morphological abnormalities. However, the exact aetiology of ventilation defects in asthma is not well understood.

OBJECTIVE: To better understand the determinants of ventilation defects in asthma, we evaluated well-established clinical as well as (3)He MRI and X-ray CT airway measurements in healthy subjects and subjects with asthma.

METHODS: Thirty-four subjects (n=26 subjects with asthma, n=8 healthy volunteers) underwent MRI, spirometry, plethysmography, fraction of exhaled nitric oxide analysis, methacholine challenge and CT for a region-of-interest proximal to ventilation …

Measuring Pain Withdrawal Threshold Using A Novel Device In "Pseudo-Continuous" Mode, A. H. Walker, S. Thurman, N. Martinez, S. Burns, M. Dobretsov

Journal of the Arkansas Academy of Science

The study of pain and analgesia is an important area of biomedical research that has led to a significant number of advances in the treatment of acute and chronic pain. This study introduces a novel approach to mechanical testing of pain withdrawal of a rat hind paw to a stimulus. This systematic method involves a modified electronic esthesiometer controlled by an IDEA drive that allows for consistency in experiments. The device gives the experimenter computer control of the step size and velocity of approach of the probe stimulus. We discuss here some of the limitations in the current techniques used …

Statistical Modeling Of Interfractional Tissue Deformation And Its Application In Radiation Therapy Planning, Douglas J. Vile

Theses and Dissertations

In radiation therapy, interfraction organ motion introduces a level of geometric uncertainty into the planning process. Plans, which are typically based upon a single instance of anatomy, must be robust against daily anatomical variations. For this problem, a model of the magnitude, direction, and likelihood of deformation is useful. In this thesis, principal component analysis (PCA) is used to statistically model the 3D organ motion for 19 prostate cancer patients, each with 8-13 fractional computed tomography (CT) images. Deformable image registration and the resultant displacement vector fields (DVFs) are used to quantify the interfraction systematic and random motion. By applying …

Fluid Flow Shear Stress Over Podocytes Is Increased In The Solitary Kidney., Tarak Srivastava, Gianni E. Celsi, Mukut Sharma, Hongying Dai, Ellen T. Mccarthy, Melanie Ruiz, Patricia A. Cudmore, Uri S. Alon, Ram Sharma, Virginia A. Savin

Manuscripts, Articles, Book Chapters and Other Papers

BACKGROUND: Glomerular hyperfiltration is emerging as the key risk factor for progression of chronic kidney disease (CKD). Podocytes are exposed to fluid flow shear stress (FFSS) caused by the flow of ultrafiltrate within Bowman's space. The mechanism of hyperfiltration-induced podocyte injury is not clear. We postulated that glomerular hyperfiltration in solitary kidney increases FFSS over podocytes.

METHODS: Infant Sprague-Dawley rats at 5 days of age and C57BL/6J 14-week-old adult mice underwent unilateral nephrectomy. Micropuncture and morphological studies were then performed on 20- and 60-day-old rats. FFSS over podocytes in uninephrectomized rats and mice was calculated using the recently published equation …

A Nonrigid Registration Method For Correcting Brain Deformation Induced By Tumor Resection, Yixun Liu, Chengjun Yao, Fotis Drakopoulos, Jinsong Wu, Liangfu Zhou, Nikos Chrisochoides

Computer Science Faculty Publications

Purpose: This paper presents a nonrigid registration method to align preoperative MRI with intraoperative MRI to compensate for brain deformation during tumor resection. This method extends traditional point-based nonrigid registration in two aspects: (1) allow the input data to be incomplete and (2) simulate the underlying deformation with a heterogeneous biomechanical model.

Methods: The method formulates the registration as a three-variable (point correspondence, deformation field, and resection region) functional minimization problem, in which point correspondence is represented by a fuzzy assign matrix; Deformation field is represented by a piecewise linear function regularized by the strain energy of a heterogeneous biomechanical …

Scanned Ion Beam Therapy For Thoracic Tumors, John Gordon Eley

Dissertations and Theses (Open Access)

Although frequently cured of Hodgkin lymphoma, adolescents and young adults can develop radiation induced second cancers. These patients could potentially benefit from scanned ion radiotherapy yet likely would require motion mitigation strategies. In theory, four-dimensional (4D) optimization of ion beam fields for individual motion states of respiration can enable superior sparing of healthy tissue near moving targets, compared to other motion mitigation strategies. Furthermore, carbon-ion therapy can sometimes provide greater relative biological effectiveness (RBE) for cell sterilization in a target but nearly equivalent RBE in tissue upstream of the target, compared to proton therapy. Thus, we expected that for some …

Investigation Of Respiratory Motion Management Techniques For Proton And Photon Radiotherapy Of Lung Cancer, Jason E. Matney

Dissertations and Theses (Open Access)

Protons as a source of therapeutic radiation can provide a substantial improvement over dose distributions that can be achieved with conventional sources of radiation such as high-energy photons. However, respiratory motion can significantly impact the delivered proton and photon dose distributions during lung cancer radiotherapy. The goals of this dissertation research were to evaluate the impact of respiratory motion and to estimate the benefit of respiratory gating for passively scattered proton therapy (PSPT) and intensity modulated photon therapy (IMRT).

The first aim of this project was to determine the impact of respiratory motion in PSPT and IMRT. Four dimensional dose …

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 …

A Miniaturised Spectrometer Device For The Detection Of Nitrogen Dioxide In An Urban Environment, Brian Devine

Doctoral

Monitoring of air pollutants, such as Nitrogen Dioxide (NO2), that are toxic or environmentally damaging is a key metric for environmental protection agencies worldwide. There is a constant need to develop new technologies and methodologies that provide real-time, low cost pollution measurements over a broad range of sampling sites, particularly in urban and industrial areas. Typically, detection of pollutants in urban environments is performed using a variety of techniques, many of which are expensive, require complex setups and are in fixed locations. The novel system presented in this thesis is designed for portable, low cost and in-situ detection of pollutants …

Evaluation Of Presage® Dosimeters For Brachytherapy Sources And The 3d Dosimetry And Characterization Of The New Agx100 125i Seed Model, Olivia Huang

Dissertations and Theses (Open Access)

With continuous new improvements in brachytherapy source designs and techniques, method of 3D dosimetry for treatment dose verifications would better ensure accurate patient radiotherapy treatment. This study was aimed to first evaluate the 3D dose distributions of the low-dose rate (LDR) Amersham 6711 Oncoseed^TM using PRESAGE^® dosimeters to establish PRESAGE^® as a suitable brachytherapy dosimeter. The new AgX100 ¹²⁵I seed model (Theragenics Corporation) was then characterized using PRESAGE^® following the TG-43 protocol.

PRESAGE^® dosimeters are solid, polyurethane-based, 3D dosimeters doped with radiochromic leuco dyes that produce a linear optical density response to radiation dose. …

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 …

Improving Cervical Cancer Nodal Boost Radiation Therapy By Quantifying Uncertainties And Exploring Advanced Radiation Therapy Modalities, Zhiqian Yu

Dissertations and Theses (Open Access)

Radiation therapy for patients with intact cervical cancer is frequently delivered using primary external beam radiation therapy (EBRT) followed by two fractions of intracavitary brachytherapy (ICBT). Although the tumor is the primary radiation target, controlling microscopic disease in the lymph nodes is just as critical to patient treatment outcome. In patients where gross lymphadenopathy is discovered, an extra EBRT boost course is delivered between the two ICBT fractions. Since the nodal boost is an addendum to primary EBRT and ICBT, the prescription and delivery must be performed considering previously delivered dose. This project aims to address the major issues of …

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.