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T A Carpenter

Publications and source records attributed to T A Carpenter.

At least 73 records · Page 4Linked to original sources
PubMed1995

Visualisation of subchondral erosion in rat monoarticular arthritis by magnetic resonance imaging.

High-resolution magnetic resonance imaging (MRI) was used to investigate antigen-induced monoarticular arthritis (AIMA) in the rat. In sagittal, spin-echo images of the knee, characteristic parallel bands, in the order dark-light-dark, were consistently observed 5-8 days after arthritis induction; the bands ran concentric with, and just beneath, the femoral and tibial articular surfaces. Concurrent radiology, histology and MRI (chemical shift-selective imaging and contrast enhancement with magnetisation transfer and gadolinium) established that the phenomenon reflected subchondral erosion, not artefact. The outer hypointense band corresponded to calcified cartilage underlying the articular surface. The central hyperintense band reflected inflammatory matrix displacing normal haematopoietic tissue immediately subchondrally; here, trabecular bone had mostly disappeared, but adjacent articular cartilage, although under attack and lacking proteoglycan, appeared structurally normal. The inner hypointense band reflected deeper, truncated trabeculae within inflammatory matrix, layered with pallisading osteoblast-like cells. This study exemplifies the power of MRI for revealing localised joint pathology non-invasively, and shows that rat AIMA shares many pathological features with arthritis in human beings.

Animals↗
PubMed1995

High resolution MR imaging of joint degeneration in the knee of the STR/ORT mouse.

MR imaging of the knee joints of the mouse at 2.35 T produces an in-plane resolution of 35 x 70 microns and a slice thickness of 600 microns from the sagittal and coronal planes, in less than 60 min. In normal, live DBA mice, which have no known pathology, the images clearly resolve many joint structures, such as the cruciate ligaments, menisci, and articulating surfaces of the femur and tibia. Gross pathological changes were identified first in excised knees from cadaver mice of the STR/ORT strain. Males of this strain spontaneously exhibit rapid joint degeneration with increasing age compared to females, in which much milder symptoms develop more slowly. Thickening of the patellar tendon, displacement of the patella, deformity, and sclerosis were clearly distinguishable in males compared with females older than 7 mo of age. The same degenerative features were evident in MR images of the knees of the live male but not female STR/ORT mice of this age, indicating that it would be possible to monitor longitudinally by MR imaging progressive development of joint changes in this osteoarthritic model.

Animals↗
PubMed1995

Visualisation of changes in regional cerebral blood flow (rCBF) produced by ketamine using long TE gradient-echo sequences: preliminary results.

Autoradiographic studies have shown that low dose ketamine produces increases in regional glucose utilisation and blood flow in the hippocampus, cerebral cortex, and olfactory lobe in the rat brain, probably due to antagonism at the NMDA receptor. Functional MRI using deoxyhaemoglobin contrast can be used to study changes in regional cerebral blood flow (rCBF). Long TE gradient-echo sequences were used to study changes in rCBF produced by low dose ketamine in rats anaesthetised with nitrous oxide, supplemented with either halothane (HAL) or fentanyl/fluanisone/midazolam (FFM) combination. Images from rats in the FFM group showed a 10-14% increase in signal intensity in the hippocampus, cerebral cortex, and olfactory lobe following either a single bolus or a low dose infusion of ketamine (p < .05). These changes were significantly reduced in the HAL group (p < .005). Halothane is known to attenuate the changes in regional glucose utilisation produced by the noncompetitive NMDA antagonist dizocilpine (MK-801), and its effects on ketamine-induced changes in rCBF seen in this study may be due to a similar effect. The potential use of functional MRI in studying the effect of pharmacological interventions on rCBF is discussed.

Anesthetics, Dissociative↗
PubMed1995

Visualisation of mass transport of small organic molecules and metal ions through articular cartilage by magnetic resonance imaging.

Magnetic resonance imaging of water has been used to visualise the migration of three paramagnetic species, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-hydroxy-TEMPO, 1), Cu2+ ions, and copper ethylenediamine-tetraacetate (CuEDTA, 2) through cartilage on the femoral condyle of the chicken knee. The migration of copper ions is dominated by strong binding with the cartilage. In contrast, both 1 and 2 bind weakly, and their diffusion can be followed as a progressive wave through the cartilage and subsequently into the trabecular bone structure.

Animals↗
PubMed1995

A comparison of the early development of ischaemic damage following permanent middle cerebral artery occlusion in rats as assessed using magnetic resonance imaging and histology.

Recent developments in diffusion-weighted imaging (DWI) have enabled the pathological changes that occur during cerebral ischaemia to be studied. The present studies utilised DWI to investigate the development of early ischaemic changes following permanent middle cerebral artery (MCA) occlusion in the rat, which represents a model of stroke. An increased DWI signal was seen in the region of the occluded MCA and this was detectable as early as 1 h postocclusion. DWI images were obtained at nine stereotactic levels throughout the brain, providing a quantifiable measure of the volume of increased signal intensity in each animal. At 1 h post-MCA occlusion the hyperintense areas were seen in the frontoparietal cortex and lateral caudate nucleus; these areas represent the core of the infarct and no protection is seen with any compounds in these areas. There was a progressive increase in the area of hyperintensity up to 4 h post-MCA occlusion, and at this time point the hyper-intensity was seen in the dorsolateral cortex and caudate nucleus. At 4 h post-MCA occlusion there was a significant correlation between the volume of hemispheric and cortical ischaemic damage measured using DWI and histology. Thus, it appears that the increased DWI signal seen during the early time points after MCA occlusion was demarcating tissue that was destined for infarction. The area beyond the hyperintense region at 1 h represents the so-called "penumbral" region, because with increasing time (post-MCA occlusion) this area became incorporated into the infarct. There was also a slight increase in infarct size between 4 and 24 h, when assessed using DWI or histology, although two groups of animals were being compared, as opposed to the time-course study, in which just one group of animals was used. At 24 h post-MCA occlusion there was a good correlation between DWI, histology, and conventional T2 weighted imaging. There was no further increase in size of the infarct between 24 h and 7 days as assessed using histology and T2-weighted imaging. DWI could not be used to quantify infarct volume at 7 days because there was no uniform signal in the damaged area. At 7 days the area of infarction actually appeared to be darker in the diffusion-weighted images. The hyperintensity seen in diffusion-weighted images appears to decrease some time between 24 h and 7 days.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Magnetic resonance imaging protocol optimization for evaluation of hyaline cartilage in the distal interphalangeal joint of fingers.

RATIONALE AND OBJECTIVES: To identify a single magnetic resonance imaging (MRI) protocol that will provide optimal signal-to-noise ratio, resolution, and image contrast with minimal susceptibility artifacts and that will allow clear delineation and visualization of cartilage, fluid, bone, tendons, and ligaments within the distal interphalangeal (DIP) joint of the human hand. METHODS: A highly optimized 2.4 T MRI system was constructed from a 31-cm horizontal bore magnet, using a solenoid radiofrequency coil. This was used to study the DIP joints of 16 healthy, asymptomatic volunteers. RESULTS: A range of image contrast protocols were explored, including spin-echo T1 and T2, field echo, chemical shift suppression to give water only images, and magnetization transfer. Susceptibility variations were explored by changing the field strength from 0.6 to 2.4 T. A spin-echo protocol with TR = 1500 msec and TE = 30 msec can routinely produce images with resolution 0.075 x 0.150 for a slice thickness of 1 mm in 13 minutes. That protocol can visualize simultaneously compact and trabecular bone, two layers of cartilage, synovial fluid, and synovium within the joint, tendons and ligaments, and the volar plate. CONCLUSIONS: Although the contrast is not fully optimized for any one tissue, the spin echo protocol (TR = 1500, TE = 30) provides sagittal MR images, which clearly delineate the major structures of interest within the DIP joint, and which will be used in future studies to compare changes in the DIP joint because of aging or osteoarthritis. Experience gained by applying the above methods to a total of 16 healthy, asymptomatic volunteers has enabled a single sequence to be identified, which although not optimized for any one tissue, nevertheless visualized simultaneously and clearly delineated compact and trabecular bone, two layers of cartilage, synovial fluid, and synovium within the joint.

Adult↗
PubMed1995

Magnetic resonance imaging of the normal mouse brain: comparison with histologic sections.

Details in the living animal can be compared with respective histologic section taken after death. In less than 35 min, 12 to 16 coronal and transverse images through the brain can be obtained, each with an in-plane resolution of 100 x 200 microns and a slice thickness of 900 microns. The experimental parameters can be manipulated not only to achieve different tissue contrast but also to access any desired plane.

Animals↗
PubMed1994

High-resolution magnetic resonance imaging of arthritic pathology in the rat knee.

High-resolution magnetic resonance imaging (MRI) has been used to visualise the changes that occur in both soft tissue and bone during antigen-induced, monoarticular arthritis (AIMA) of the rat knee. Extensive optimisation studies were performed in order to minimise the time of the experiments and to maximise both the signal-to-noise ratio and the contrast in the MR images. The study was cross-sectional rather than longitudinal and at each of the 13 time points studied during the progression of the disease, corresponding X-radiographs and histological sections were obtained. Interpretation of the spin echo MR images was aided by the use of chemical shift-selective imaging, magnetisation transfer contrast and relaxation time experiments, as well as by correlation with the histology and X-radiography data. The MR images clearly show invasion of the synovium by an inflammatory pannus which spreads over the articular cartilage and invades the bone, leading to erosion and later remodelling. Two distinct types of bony erosion were observed: focal erosions, especially at the margins of the joint, and subchondral erosions. It is concluded that MRI provides a sensitive, non-invasive method for investigating both early-stage inflammatory changes and late-stage bony changes in the knee joints of the arthritic rat.

Animals↗
PubMed1994

An MRI study of drying in granular beds of nonporous particles.

MRI is used to study the role of capillary and gravitational forces in controlling mass transport of water during isothermal drying of granular beds of nonporous particles. A new model is presented that shows how capillary and gravitational forces relate to Fickian diffusion driven by a chemical potential gradient. In granular beds, where capillary and gravitational forces dominate, the image profiles give direct information on the dependence of the degree of saturation on capillary suction pressure. The effects of changing particle size and surface tension on the profiles is investigated quantitatively, and it is shown that high capillary pressures create anomalies in the drying profiles.

Algorithms↗
PubMed1994

Magnetic resonance imaging (MRI) of calcium alginate gels.

The spatial heterogeneity of calcium alginate gels has been visualised by the variation of image intensity across the gel by one-, two-, and three-dimensional MRI. From the linear dependence of (T2)-1 on alginate concentration it is now possible to use MRI to map alginate concentration gradients within calcium alginate gels noninvasively. Since the concentration of alginate determines the pore size of the gel matrix, those alginate concentration maps will be useful in determining the pore size distribution within the gel, which is important in controlled release applications.

Alginates↗
PubMed1994

Magnetic resonance imaging of soil-water phenomena.

2D and 3D images of static and dynamic water phenomena in packed clay soil columns were obtained by MRI. A spin-echo spin-warp Fourier imaging sequence, together with prefocused 90 degrees selective pulse for 2D imaging, was selected. The images demonstrate the potential of using MRI for studies of static and dynamic water phenomena in soil with modest iron content and adequate water content.

Fourier Analysis↗
PubMed1994

Quantitative longitudinal fluid saturation profiles with a slice-selected CPMG sequence.

A technique for obtaining quantitative longitudinal saturation/porosity profiles of rock cores which are longer than the NMR coil has been developed. The slice-selected experiment uses a prefocused pulse in conjunction with a magnetic field gradient for the localization and a CPMG sequence to sample the data. A variety of rock core samples has been studied ranging from limestones to shaly sandstones. Comparison of the relaxation decay curves obtained from these experiments and the bulk experiments show that reliable localized relaxation data are obtained.

Calcium Carbonate↗
PubMed1994

Magnetic resonance imaging planes for the 3-dimensional characterisation of human coronary arteries.

We report a magnetic resonance imaging study which developed a consistent hierarchy of imaging planes for examination of the origins, courses and principal branches of the main coronary arteries of prepared human cadaveric hearts. The reference longitudinal axis was chosen between the aortic valve and the apex of the left ventricle. A series of transverse planes then successfully visualised the ostia of the left and right coronary arteries; the left main coronary, its bifurcation, and the left anterior descending artery for a distance 24 mm distal to its origin were clearly distinct in successively posterior sections as was the emergence and course of the right coronary artery. Further sections were derived from an axis that joined the posterior aspects of the left and right coronary artery ostia seen in cross-section, which demonstrated the origins of these arteries. They also traced the circumflex artery 30 mm beyond its point of emergence and demonstrated the course of the right coronary artery between the right ventricle and right atrium. The anatomical identifications were confirmed in selective 3-dimensional reconstructions of the cardiac anatomy around the aortic root and pulmonary artery origin. The orthogonal anatomical arrangements of the left and right coronary artery arterial trees thus permit a consistent set of imaging planes useful for the visualisation of all the major branches in a static heart in vitro. This may offer an approach useful for clinical imaging of human coronary vessels in vivo in the moving heart.

Aged↗
PubMed1993

A simple device for respiratory gating for the MRI of laboratory animals.

Respiratory motion must be overcome if MRI of the abdomen, even at the lowest resolution, is to be performed satisfactorily. A simple and reliable respiratory gating device, based on the interruption of an infrared (IR) optical beam is described. This device has the advantage that gating is based on the position of the chest as opposed to its velocity, and that it can be used without degrading the radiofrequency isolation of a Faraday cage. Its use in animal MRI is illustrated by high resolution (200 microns) images of in vivo rat liver and kidney.

Abdomen↗
PubMed1992

Magnetic resonance imaging: a new window into industrial processing.

Although the most important use of nuclear magnetic resonance imaging (MRI) continues to be for diagnostic medicine, recognition is being gained for many nonmedical applications. Examples include the following areas: petrogeology, food, agriculture, polymers and polymer-composites, and pharmaceuticals. These areas all involve studies of species that have short spin-spin relaxation times, and consequently need far fast gradient switching. These technical details are discussed and typical applications given.

Industry↗
PubMed1992

An investigation of the origins of contrast in NMR spin echo images of plant tissue.

The effects that the spatial distribution of water protons and their transverse relaxation times have on the image contrast of spin echo images of courgette was investigated. The T2-weighted image of courgette contains the most anatomical information. The image contrast was explained using a phenomenological theory based on the Bloch equations, which gave an insight into the morphology and microdynamics of water in the plant tissue. The perceived contrast in the spin echo images of courgette, glucose and Sephadex bead solutions can be dramatically altered by keeping all the imaging acquisition parameters constant, such as the recycle and echo time, but reducing the interpulse spacing by introducing a CPMG train of 180 degrees pulses into the middle of the sequence. These changes were interpreted by considering the microenvironment of the water. This work demonstrates that the origin of image contrast in T2-weighted images of plant tissue can be understood using the water proton transverse relaxation theory developed by Hills et al.

Dextrans↗