Multimodality Imaging of the Peripheral Venous System

The purpose of this article is to review the spectrum of image-based diagnostic tools used in the investigation of suspected deep vein thrombosis (DVT). Summary of the experience gained by the author as well as relevant publications, regarding vein imaging modalities taken from a computerized database, was reviewed. The imaging modalities reviewed include phlebography, color Doppler duplex ultrasonography (CDDUS), computerized tomography angiography (CTA) and venography (CTV), magnetic resonance venography (MRV), and radionuclide venography (RNV). CDDUS is recommended as the modality of choice for the diagnosis of DVT. A strategy combining clinical score and D-dimer test refines the selection of patients. Phlebography is reserved for discrepant noninvasive studies

Development of a deep vein valve replacement

Background Chronic venous disease is a common, distressing and significant cause of health care expense. There have been few developments in the treatment of deep venous disease as the understanding of the clinical and pathophysiological significance of deep vein reflux and valve failure remains poor. Previous attempts to develop a prosthetic vein valve implant have been disappointing. Difficulties with early thrombosis led researchers to abandon their efforts many years ago. Attempts to create a valve implant should be revisited. Aims The aims of this project are to: evaluate variables around normal deep vein valves, to develop validated computational and laboratory flow models for deep venous function, and to develop and investigate a novel material to engineer a prototype bioprosthetic deep vein valve replacement. Methods Functional Anatomy: This is a prospective observational study evaluating subjects with normal deep veins. B and M Mode ultrasound, contrast (microbubble) enhanced ultrasound and dynamic magnetic resonance imaging of normal subjects was carried out. This has given the flow, velocity data and anatomical images required for the project. Modelling: A preliminary computational flow model has been developed using the data obtained from the imaging stage of the project. This is a 2-dimensional model incorprating flexible valve leaflets. A laboratory model of venous function, in the form of a flow rig has been created. Materials: Presently, polymers and polymer coated metal stents, used in the vascular system have several problems: they are very thrombogenic and they lack haemocompatibilty and biocompatibility, in addition they lack the required mechanical properties. A novel material that is biocompatible, a copolymer of methacrylolyoxyethyl phosphorylcholine (MPC), trimethylsilyl-2-propyl methacrylate (TMSPMA) and Hydroxypropyl methacrylate (HPMA), has been synthesised. Its properties have been modified by electrospinning and crosslinking to change its solubility and mechanical properties, without altering its biocompatibility. Impact This project aims to guide the development of a treatment for patients, for whom few options are available. Chronic venous disease and venous ulceration are painful and debilitating, potentially requiring years of treatment. Effective, minimally invasive treatment options could result in accelerated ulcer healing and improvements in symptoms and quality of life as well as reduced costs.Open Acces

MR Sequence Development for Imaging Venous Blood Flow in the Leg

Deep Vein Thrombosis is a common complication in bed-ridden patients, described as the main cause of preventable hospital deaths in the UK (NICE 2010). Mechanical prophylaxis aims to promote venous flow, either statically with compression stockings, or dynamically with intermittent pneumatic compression or electrical muscle stimulation. Previous studies used ultrasound for venous flow measurements, limited to a single deep vein at a time, and some anatomical MRI for investigating the mechanisms behind these prophylaxes. MRI velocity mapping is used clinically in the arterial system where gating enables data accumulation over multiple cardiac cycles. This thesis describes the development of two real-time MRI spiral velocity mapping sequences for imaging venous blood flow in the leg, where venous flow variability is largely unrelated to the cardiac cycle. Real-time imaging with spiral gradient readouts minimised image duration. A phase-image fitting technique requiring only a velocity-encoded phase image was implemented for acceleration. For in vivo comparison, conventional flow imaging required metronome-guided breathing for a regular venous flow waveform. The long spiral readouts were sensitive to off-resonance and flow artefacts, where some unpublished effects were investigated. The off-resonance associated with deoxygenation of venous blood did not cause notable spiral artefacts, but disrupted the phase-image fitting technique and required correction with a pre-scan. The spiral flow methods demonstrated increased venous blood velocity and flow during application of mechanical compression. Metronome-guided breathing was also applied to vein wall imaging, where it detected wall thickening in patients with Behçet’s disease compared with normal subjects. For the first time, this thesis evaluated real-time MRI spiral velocity mapping of venous blood velocity and flow. The high resolution (1mm) and short image time required caused challenging off-resonance and flow artefacts. With some limitations, real-time spiral flow MRI during operation of compression devices may assist in their optimisation