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Biomedical subjects

W Vennart

Publications and source records attributed to W Vennart.

17 recordsLinked to original sources
PubMed1995

Modified birdcage coils for targeted imaging.

The design of a radiofrequency coil of U-shaped geometry, specifically intended to image individual knuckle joints of the hand, has been investigated. The coil geometry is that of a "split and opened" birdcage coil. The optimum leg positions for such a U-shaped coil have been theoretically predicted using a novel technique that considers both the signal-to-noise ratio and the homogeneity of the field-of-view. Two particular coils of this type have been constructed, each optimum for a different size of image space and assuming a different source of image noise (sample-dominated or coil-dominated). The experimentally determined radiofrequency fields produced by the coils correspond well to theory. Either coil can be used to obtain good-quality, high-resolution (130 microns x 130 microns in-plane) images in vivo of the first, second, or fifth metacarpophalangeal joints of the hand, sites of particular interest in the study of arthritis.

Arthritis↗
PubMed1995

Osteoarthritis and magnetic resonance imaging: potential and problems.

To date, MRI has primarily been used to study anatomical changes, and at a resolution that makes detailed analysis of focal change difficult. This is primarily because cost limits the development and use of tailor made research systems. The detailed analysis of soft tissue, cartilage, and bone marrow images should provide a fruitful non-invasive method to study OA. However, the development of MRI methods to study movement, diffusion and perfusion, and the spatial localisation of spectroscopic information, promises a revolution in the study of the living joint in man.

Bone and Bones↗
PubMed1994

Water diffusion coefficient measurements in the finger by magnetic resonance imaging.

Diffusion coefficients of water have been measured in the fingers of humans by magnetic resonance imaging. It was found that the measured diffusion coefficients increased with subject age in certain regions of the finger but that these regions differed between males and females. The observation of an increased diffusion coefficient with age appears to be inconsistent with a direct-hydration model and possible explanations are given using other models. It is conjectured that the measured diffusion coefficient of water increases with age as a result of structural changes to proteins.

Adult↗
PubMed1993

Magnetic resonance imaging manifestations of idiopathic haemochromatosis in the wrist.

The magnetic resonance imaging features of the wrist of a patient suffering from the arthropathy of haemochromatosis are presented. It is apparent that the deposition of iron within the bone marrow is focal in origin and may be associated with cyst formation. In addition, changes in serum ferritin levels with treatment suggest that the deposition is irreversible. Studies of two other patients with haemochromatosis without cyst formation in the wrists did not yield similar artefacts, in spite of having high ferritin levels and arthritis.

Aged↗
PubMed1991

High-resolution magnetic resonance imaging of the interphalangeal joints of the hand.

High-resolution magnetic resonance imaging (MRI) of the interphalangeal joints of the fingers is being employed to study arthritis. To facilitate this research, a clear understanding of the structures visualisable by MRI is necessary. A gradient echo (GE) sequence was developed that produced good contrast between cartilage and other joint structures. These detailed images, with an in-plane resolution of 200 x 100 microns, enable resolution of three cartilage zones which can be interpreted as a superficial layer at the cartilage/cartilage interface, an intermediate layer and calcified cartilage in contact with bone; these correlate well with known anatomy. Further analysis of the images indicates that although a chemical shift artifact causes changes in the images at the field strength used (0.5 T), it does not cause enough distortion to necessitate suppression of the effect. Furthermore, the only detectable susceptibility artifact at these low field strengths was a loss of signal in bone trabeculae at the bone/cartilage interface. There is clearly potential in the study of the articular structures, in particular cartilage, in detail, using high-resolution MRI.

Adult↗
PubMed1990

Demonstration of a geode by magnetic resonance imaging: a new light on the cause of juxta-articular bone cysts in rheumatoid arthritis.

The magnetic resonance imaging (MRI) features of a rheumatoid arthritic geode are presented. Development of such a cyst from before x ray diagnosis to its coalescence with the wrist joint is described. The evidence suggests that these juxta-articular cysts are not merely an intrusion of the synovial cavity into the bone marrow but start as isolated structures beneath the subchondral bone.

Adult↗
PubMed1989

Development of an equine nuclear medicine facility for gamma camera imaging.

A nuclear medicine facility constructed specifically for the application of a gamma camera system to the radioisotope imaging of bone, pulmonary circulation and ventilation in the horse is described. The gamma camera was previously used for human nuclear medicine, and a support for the gamma camera head was specifically designed for this work. Imaging protocols are suggested and the necessary materials for bone and lung studies are described. Images of bone and lung are shown and computer analysis of the data indicated. Imaging times are approximately 1 to 2 mins and typical bone and lung studies can be completed in 20 to 30 mins.

Animals↗
PubMed1984

Radioisotope bone scanning in horses.

The detection of radionuclide activity in the living equine skeleton, using bone seeking radiopharmaceuticals and a hand-held radiation detector, is reported. Pathological changes in bone can be detected and subsequent development monitored. The availability and use of this diagnostic technique in equine practice is discussed.

Animals↗
PubMed1984

A peroperative test of the function of the sphincter of Oddi.

A simple peroperative flow test has been developed to help detect organic stenosis of the Ampulla of Vater. The influence of glucagon and propantheline bromide on the flow of saline through the Ampulla during operation in 79 patients was measured. By measuring the flow rate of saline before and after the administration of glucagon to patients the effective diameter of the sphincter of Oddi and its ability to relax could be deduced. Glucagon was found to be most effective in relaxing the Ampulla. For the test to be successful impacted stones must be excluded by cholangiography, but free lying stones do not affect the test. In 7 of the 62 patients receiving glucagon flow was slow and the sphincter failed to relax. Two of these patients had impacted stones and were treated by ampullary dilatation and the other 5 (who had no stones showing on X-rays) were treated by trans-duodenal sphincterotomy; 2 of these patients were found to have small non-obstructing stones impacted at the Ampulla.

Adult↗
PubMed1981

Management of fissure fractures in Paget's disease.

Forty-five patients with Paget's disease were studied, of whom 25 had fissure fractures affecting the bones of the lower limb. Ten patients treated with salmon calcitonin showed no improvement in their fissure fractures despite reduction in bone turnover. Treatment was effective where bone deformity was improved by traction or intra-medullary nail fixation combined with osteotomy. Surgical treatment should be undertaken in those patients who complain of acute pain at the site of a fissure fracture and who risk completing the fracture. Fissure fractures involving the femoral neck should be fixed even when asymptomatic because of the risk of non-union if they become complete.

Aged↗
PubMed1981

Bone turnover in Paget's disease: biochemical and kinetic measurements during salmon calcitonin therapy.

A comparison of calcium-47 kinetics and biochemical measurements has been made in 25 previously untreated patients with Paget's disease. The rate of disappearance of 47Ca into bone with a turnover time of more than 5 days was measured as A5, and the pool size with a turnover time of less than 5 days as E5. In moderately active disease the reductions in A5 and E5 to be anticipated from treatment seem to be offset by an increase in exchangeability due to remineralization of osteoid. In more active disease the effect of calcitonin may be to shift bone formation from a woven to a lamellar pattern as well as to reduce turnover. Under these circumstances both A5 and E5 are reduced by treatment more in keeping with biochemical changes.

Animals↗