Author : Nicholas J. Hangiandreou
Publisher :
Page : 344 pages
File Size : 26,43 MB
Release : 1990
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Author : Andrew Harry Jennings
Publisher :
Page : 64 pages
File Size : 49,45 MB
Release : 2007
Category :
ISBN :
Computational fluid dynamic (CFD) simulations are emerging as a promising tool for diagnosis and treatment planning of vascular diseases such as intracranial aneurysms. In addition to the three-dimensional luminal geometry, prior knowledge of the blood velocity in the feeding artery is required before running a CFD simulation. This thesis describes a new method to extract the blood velocity in arteries using Digital Subtraction Angiography, a procedure routinely used in endovascular intervention. This method, referred to as the "radius-ratio" method, is based on the measurement of the contrast-intensity versus time at two locations along a vessel. The measured time-density curves are fitted to idealized curves that would result if contrast were convected in a fully developed steady pipe flow with an average velocity equal to the average velocity of the pulsatile flow. Centerline blood velocity is calculated by dividing the distance between the two vessel locations by the difference between the projected bolus arrival times at each location. Average velocity is then taken to be half this value. Compared to the existing time-density methods that extract velocity from angiography, the radius-ratio method is potentially more accurate because it incorporates a physics-based flow field model. To test the feasibility of the radius-ratio method in practical settings, the RR method was used to determine the velocity of blood in-vitro for vessel phantoms and in-vivo for canine and rabbit common carotid arteries. The RR computed velocity was then compared with the velocity computed using a standard time-density algorithm, and the velocity measured using an ultrasonic flowprobe. It was found that the accuracy v of both RR and TD methods were similar when compared when a gold standard flowprobe. To obtain a pulsatile canine waveform of velocity from the measured time-averaged velocity, an archetypal waveform in a canine common carotid artery can be scaled by heart rate and average velocity to yielding a approximation to the "true" velocity waveform. In human vasculature, it is postulated that the RR method is appropriate in internal carotid arteries and vertebral arteries.
Author : Josef F. Bille
Publisher : Springer
Page : 407 pages
File Size : 17,30 MB
Release : 2019-08-13
Category : Medical
ISBN : 3030166384
This open access book provides a comprehensive overview of the application of the newest laser and microscope/ophthalmoscope technology in the field of high resolution imaging in microscopy and ophthalmology. Starting by describing High-Resolution 3D Light Microscopy with STED and RESOLFT, the book goes on to cover retinal and anterior segment imaging and image-guided treatment and also discusses the development of adaptive optics in vision science and ophthalmology. Using an interdisciplinary approach, the reader will learn about the latest developments and most up to date technology in the field and how these translate to a medical setting. High Resolution Imaging in Microscopy and Ophthalmology – New Frontiers in Biomedical Optics has been written by leading experts in the field and offers insights on engineering, biology, and medicine, thus being a valuable addition for scientists, engineers, and clinicians with technical and medical interest who would like to understand the equipment, the applications and the medical/biological background. Lastly, this book is dedicated to the memory of Dr. Gerhard Zinser, co-founder of Heidelberg Engineering GmbH, a scientist, a husband, a brother, a colleague, and a friend.
Author : Atila Ersahin
Publisher :
Page : 274 pages
File Size : 14,39 MB
Release : 1993
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Author : George Joseph Stephen Hunter
Publisher :
Page : pages
File Size : 40,37 MB
Release : 2000
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Author : Nicholas Ayache
Publisher :
Page : pages
File Size : 23,10 MB
Release :
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Author : Nischal Koirala
Publisher :
Page : pages
File Size : 30,57 MB
Release : 2018
Category :
ISBN :
The global burden of renal disease has continued to rise and has severely impacted the health, cost, and quality of life among such patients. End-stage renal disease (ESRD) patients require dialysis or kidney transplant to continue life. Dialysis requires the creation of vascular access that can provide long term complication-free access to systemic circulation to carry out external blood purification by a dialyzer. To create an access, arteriovenous (AV) fistula or AV graft is predominantly used. Major problems associated with such access types include stenosis and thrombosis that affect access patency and the rate of blood flow, which ultimately impedes the efficiency of dialysis. Therefore, quantification of blood flow is an important parameter for dialysis access surveillance and to adjudicate access patency (restoration) during endovascular interventions. The overall goal of this project is to quantify blood flow in the dialysis access based on angiographic images. This study has been built under the aegis of three specific aims that provide the understanding of blood flow dynamics, and solutions to the problems associated with flow quantification. The first aim is to identify and develop the computational methods necessary for flow quantification, and to construct an angiographic flow phantom for in vitro data collection and model validation. The second aim involves the assessment of the computational model (from aim 1) in fistulagrams (clinical images) to examine the feasibility of flow computation, which are available from the secured medical record database. Finally as a third aim, we conduct a clinical study to validate the utility of our computational model and imaging protocol. The third aim is built upon the lessons learned from the preceding aims that provide the feedback on the various physical and simulation (modeling) parameters as well as other limiting factors that need to be accounted for while targeting the product for clinical use. The information from these three aims will provide a thorough perspective into the problems associated with blood flow quantification, solutions, and the availability of flow software for access flow calculation in interventional radiology suites.
Author : Leopold Schmetterer
Publisher : Springer Science & Business Media
Page : 451 pages
File Size : 35,7 MB
Release : 2012-06-14
Category : Medical
ISBN : 3540694692
Adequate blood supply to the eye is an important prerequisite for normal visual function. Over the past 40 years our knowledge of ocular blood flow regulation has improved significantly. This reader-friendly textbook provides a comprehensive overview of the current knowledge of ocular blood flow. Lavishly illustrated, it evaluates the wide array of methods that have been used to measure ocular blood flow. Furthermore, it not only offers the reader an evidence-based summary of the physiological and pharmacological properties of ocular blood flow regulation, but also demonstrates the ocular blood flow abnormalities in different vascular diseases. This book will enhance the understanding of all who are interested in learning more about ocular blood flow in health and disease.
Author : Carlo Cavedon
Publisher : CRC Press
Page : 492 pages
File Size : 29,66 MB
Release : 2015-08-22
Category : Medical
ISBN : 1439890579
Cardiovascular and Neurovascular Imaging: Physics and Technology explains the underlying physical and technical principles behind a range of cardiovascular and neurovascular imaging modalities, including radiography, nuclear medicine, ultrasound, and magnetic resonance imaging (MRI). Examining this interdisciplinary branch of medical imaging from a
Author : Friedrich H.W. Heuck
Publisher : Springer Science & Business Media
Page : 331 pages
File Size : 13,49 MB
Release : 2012-12-06
Category : Mathematics
ISBN : 3642689574
Scientists and engineers have been involved in medical radiology from the very beginning. At times advances in this field occur at a tremen dously fast pace. Developments in radiological diagnostics have - technologically and medically speaking - focused on morphology. At present, computer-aided tomography (CAT) is at a high point in deve1opment, medical application, and validation. The preconditions for this success were rapid advances in electronics and computer technology - in hardware and in software - and an unexpected cost reduction in these fields; the co operation of various scientific disci plines was also essential. Functional radiological diagnosis has been neglected in part, owing to the emphasis on morphology, but alone the synthesis of morphology and function prornises further advances. Apart from the limited capabilities ofuItrasonic techniques there is no way other than using X-rays to carry out functional studies of organs and their systems through an intact body surface. It is frequently necessary to do further processing and evaluation of image series which have been recorded from the morphological viewpoint. This further picture processing may be of selected points (pixels) in the image, of certain regions of interest (ROI), or of the overall picture. For the measure ment of rapid phenomena, such as the blood flow in the main arteries, high image-frame rates are required, and at the moment these can only be achieved with cinemascopic techniques. For slower processes, other techniques such as videography have some advan tages.
