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Biomedical subjects

Richard Watts

Publications and source records attributed to Richard Watts.

At least 19 recordsLinked to original sources
PubMed2006

Development and validation of a consensus methodology for the classification of the ANCA-associated vasculitides and polyarteritis nodosa for epidemiological studies.

BACKGROUND: The classification of antineutrophil cytoplasmic antibody-associated vasculitis (AAV) and polyarteritis nodosa (PAN) for epidemiology studies is confusing. The existing schemes such as American College of Rheumatology (ACR) criteria, Chapel Hill Consensus Conference (CHCC) definitions and Lanham criteria produce overlapping and conflicting classifications, making it difficult to compare incidence figures. AIM: To develop a consensus method of using these criteria and definitions for epidemiological studies to permit comparison without confounding by classification. METHODS: A stepwise algorithm was developed by consensus between a group of doctors interested in the epidemiology of vasculitis. The aim was to categorise patients with Wegener's granulomatosis, microscopic polyangiitis (MPA), Churg-Strauss syndrome (CSS) and PAN into single clinically relevant categories. The ACR and Lanham criteria for CSS, and ACR criteria for Wegener's granulomatosis were applied first, as these were considered to be the most specific. Surrogate markers for Wegener's granulomatosis were included to distinguish Wegener's granulomatosis from MPA. MPA was classified using the CHCC definition and surrogate markers for renal vasculitis. Finally, PAN was classified using the CHCC definition. The algorithm was validated by application to 20 cases from each centre and 99 from a single centre, followed by a paper case exercise. RESULTS: A four-step algorithm was devised. It successfully categorises patients into a single classification. There was good correlation between observers in the paper case exercise (91.5%; unweighted kappa = 0.886). CONCLUSION: The algorithm achieves its aim of reliably classifying patients into a single category. The use of the algorithm in epidemiology studies should permit comparison between geographical areas.

Algorithms↗
PubMed2006

Fiber tracking in the cervical spine and inferior brain regions with reversed gradient diffusion tensor imaging.

Diffusion tensor echo planar magnetic resonance imaging of the inferior brain regions and the spinal cord suffers from tissue-air and tissue-bone interfaces, which cause severe susceptibility-induced artifacts. These artifacts consist of image distortions in the phase encode direction and also affect signal intensity. To correct for these distortions, we used the reversed gradient method. We find that most in-plane voxel displacements in the inferior brain regions and the cervical spine can be corrected, yielding a good match of white matter fiber tracts with anatomical reference images. Furthermore, uninterrupted white matter fiber tracts going from the cervical spine up to cortical areas, derived from data acquired in a single acquisition, are presented.

Artifacts↗
PubMed2006

Distribution of microstructural damage in the brains of professional boxers: a diffusion MRI study.

PURPOSE: To investigate and localize cerebral abnormalities in professional boxers with no history of moderate or severe head trauma. MATERIALS AND METHODS: Diffusion tensor imaging (DTI) was used to determine the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) in the brains of 81 professional male boxers and 12 male control subjects. Voxel-based analysis (VBA) of both the diffusion and anisotropy values was performed using statistical parametric mapping (SPM). From this objective analysis, regions of microstructural abnormalities in the brains of the boxers were located. RESULTS: Increases in the ADC, and decreases in FA were identified in deep white matter (WM), while decreases in ADC were identified in cortical gray matter (GM). Regions of positive correlation between ADC and age were also found in both the boxer and control groups, although the regions and strength of the correlation were not the same in each group. CONCLUSION: Using VBA, we localized previously unreported abnormalities in the brains of professional boxers. These abnormalities are assumed to reflect cumulative (chronic) brain injury resulting from nonsevere head trauma.

Adult↗
PubMed2006

Possible axonal regrowth in late recovery from the minimally conscious state.

We used diffusion tensor imaging (DTI) to study 2 patients with traumatic brain injury. The first patient recovered reliable expressive language after 19 years in a minimally conscious state (MCS); the second had remained in MCS for 6 years. Comparison of white matter integrity in the patients and 20 normal subjects using histograms of apparent diffusion constants and diffusion anisotropy identified widespread altered diffusivity and decreased anisotropy in the damaged white matter. These findings remained unchanged over an 18-month interval between 2 studies in the first patient. In addition, in this patient, we identified large, bilateral regions of posterior white matter with significantly increased anisotropy that reduced over 18 months. In contrast, notable increases in anisotropy within the midline cerebellar white matter in the second study correlated with marked clinical improvements in motor functions. This finding was further correlated with an increase in resting metabolism measured by PET in this subregion. Aberrant white matter structures were evident in the second patient's DTI images but were not clinically correlated. We propose that axonal regrowth may underlie these findings and provide a biological mechanism for late recovery. Our results are discussed in the context of recent experimental studies that support this inference.

Adolescent↗
PubMed2005

Frontostriatal microstructure modulates efficient recruitment of cognitive control.

Many studies have linked activity in a frontostriatal network with the capacity to suppress inappropriate thoughts and actions, but relatively few have examined the role of connectivity between these structures. Here, we use diffusion tensor imaging to assess frontostriatal connectivity in 21 subjects (ages 7-31 years). Fifteen subjects were tested on a go/no-go task, where they responded with a button press to a visual stimulus and inhibited a response to a second infrequent stimulus. An automated fiber tracking algorithm was used to delineate white matter fibers adjacent to ventral prefrontal cortex and the striatum, and the corticospinal tract, which was not expected to contribute to control per se. Diffusion in frontostriatal and corticospinal tracts became more restricted with age. This shift was paralleled by an increase in efficiency of task performance. Frontostriatal radial diffusivities predicted faster reaction times, independent of age and accuracy, and this correlation grew stronger for trials expected to require greater control. This was not observed in the corticospinal tract. On trials matched for speed of task performance, adults were significantly more accurate, and accuracies were correlated with frontostriatal, but not corticospinal, diffusivities. These findings suggest that frontostriatal connectivity may contribute to developmental and individual differences in the efficient recruitment of cognitive control.

Adolescent↗
PubMed2005

The human nephron filter: toward a continuously functioning, implantable artificial nephron system.

BACKGROUND: Nearly 900,000 patients worldwide have end-stage renal disease and require dialysis or kidney transplantation, and this number is expected to more than double by 2010, placing considerable stress on healthcare systems throughout the world. Despite the availability of these forms of renal replacement therapy for nearly four decades, mortality and morbidity is high and patients often have a poor quality of life. METHODS: We have developed a human nephron filter (HNF) utilizing nanotechnology that would eventually make feasible a continuously functioning, implantable artificial kidney. The device consists of two membranes operating in series within one device cartridge. The first membrane mimics the function of the glomerulus, while the second membrane mimics the function of the renal tubules. FINDINGS: The device has been computer-modeled and operating 12 h/day, 7 days/week, the HNF provides the equivalent of 30 ml/min glomerular filtration rate (compared to half that amount for conventional thrice weekly hemodialysis). CONCLUSIONS: The HNF system, by eliminating dialysate and utilizing a novel membrane system created through applied nanotechnology may represent a breakthrough in renal replacement therapy based on the functioning of native kidneys. The enhanced solute removal and wearable design should substantially improve patient outcomes and quality of life.

Computer Simulation↗
PubMed2005

Diffusion-tensor MR tractography of somatotopic organization of corticospinal tracts in the internal capsule: initial anatomic results in contradistinction to prior reports.

The goal of this study was to use diffusion-tensor magnetic resonance (MR) imaging to define the location and organization of corticospinal tracts (CSTs) in the posterior limb of the internal capsule (PLIC). The Institutional Review Board approved the study, and informed consent was obtained from all subjects. Eight volunteers and two patients with brain tumor were imaged at 3 T. All CSTs were found to lie in a compact area in one part of the PLIC: If the PLIC is divided into four equal quarters from anterior to posterior, the CST was shown to be in the third quarter. Seventeen of 20 CSTs were organized somatotopically, with hand fibers anterolateral to foot fibers, not anteromedial as is currently believed. In three of 20, hand and foot fibers were intermixed. Classically, it was thought that the CST was located in the anterior third of the PLIC. The present data confirm recent results that the CST is located more posteriorly. In the majority of cases, however, the CST is organized somatotopically.

Adult↗
PubMed2005

Epidemiology of systemic vasculitis.

The systemic vasculitides are heterogeneous conditions of unknown etiology characterized by inflammation and necrosis of different sized blood vessels. Wegener's Granulomatosis, microscopic polyangiitis, and Churg Strauss syndrome are associated with anti-neutrophil cytoplasmic antibodies and affect small and medium blood vessels. They are very rare in childhood and peak in the 65 to 70 year old age group. Wegener's Granulomatosis appears to be more common in the North of Europe compared with the South. All are more common in whites compared with other populations. Genetic and environmental factors, including infection, drugs, and silica, are important in etiology. Giant cell arteritis is predominantly a disease of whites over the age of 50. It appears more common in individuals with Nordic descent. Incidence may be increasing over time and cyclical variation in disease may reflect an infectious etiology. Takayasu arteritis is a disease of the aorta and its branches, however pulmonary and cardiac arteries may be involved. Patients are usually under 40-years of age at presentation and there are no apparent differences in incidence or clinical characteristics/aortic involvement across the globe. Kawasaki disease (KD) and Henoch-Schonlein purpura are diseases of children and rarely affect adults. Both have been reported to be more common in Asians than whites. The incidence of KD is higher in Japan and China compared with other regions. No definite trigger factors have been found, but KD has been linked to infection, house dust mite and chemicals, and Henoch-Schonlein purpura to a pesticide and drugs.

Asia↗
PubMed2005

Continuously functioning artificial nephron system: the promise of nanotechnology.

Nearly 900,000 patients worldwide have end-stage renal disease and require dialysis or kidney transplantation. Despite the availability of these forms of renal replacement therapy for nearly four decades, mortality and morbidity are high and patients often have a poor quality of life. We have developed a human nephron filter (HNF) utilizing nanotechnology that would eventually make feasible a continuously functioning, wearable or implantable artificial kidney. The device consists of two membranes operating in series within one device cartridge. The first membrane mimics the function of the glomerulus, using convective transport to generate a plasma ultrafiltrate containing all solutes approaching the molecular weight of albumin. The second membrane mimics the function of the renal tubules, selectively reclaiming designated solutes to maintain body homeostasis. No dialysis solution is used in this device. The HNF has been computer-modeled, and operating 12 hr per day, 7 days per week the HNF provides the equivalent of 30 mL/min glomerular filtration rate (compared to half that amount for conventional thrice-weekly hemodialysis). Animal studies should begin in the next 1 to 2 years, and clinical trials would then follow 1 to 2 years subsequent. The HNF system, by eliminating dialysate and utilizing a novel membrane system created through applied nanotechnology, represents a breakthrough in renal replacement therapy based on the functioning of native kidneys. The enhanced solute removal and wearable design should substantially improve patient outcomes and quality of life.

Filtration↗
PubMed2005

Diffusion tensor tractography of the motor white matter tracts in man: Current controversies and future directions.

The anatomy of the brain is extremely complex, and certain, even large structures, such as the corticospinal tract (CST), remain poorly understood. Diffusion tractography provides an opportunity to explore the white matter tracts in a fundamentally new way. In the current paper, we show how this technique has already added to our understanding of the anatomy of the CST. We also explore the future projects involving diffusion tractography of the motor white matter tracts that will advance this method and further our understanding of brain anatomy.

Brain Mapping↗
PubMed2005

Diagnostic accuracy of time-resolved 2D projection MR angiography for symptomatic infrapopliteal arterial occlusive disease.

OBJECTIVE: Our objective was to evaluate the diagnostic accuracy of time-resolved 2D projection MR angiography in detecting calf and pedal artery occlusive disease. MATERIALS AND METHODS: Time-resolved MR angiography of calf and pedal arteries was performed on 59 symptomatic legs of 52 patients using the head coil and bolus injections of 6 mL of gadolinium contrast medium. Selective X-ray digital subtraction angiography was performed within 30 days after MR angiography. Calf and pedal arteries were divided into 10 segments. X-ray digital subtraction angiography and MR angiography images were retrospectively interpreted by three expert observers, who graded segments as having no significant stenosis, significant stenosis (> 50%), or occlusion. The accuracy of MR angiography interpretations was compared with the accuracy of consensus X-ray digital subtraction angiography interpretations as the standard of reference. Arterial segments with discrepant grading on X-ray digital subtraction angiography and MR angiography were reviewed again to determine the reasons for disagreement. RESULTS: Arterial phase MR angiography images free of venous contamination were obtained in every case. The agreement between MR angiography and X-ray digital subtraction angiography in depicting infrapopliteal arterial disease was fair to good (kappa = 0.44-0.92). Overall sensitivity and specificity were 83% and 87%, respectively, for detecting significant stenosis of calf and pedal arteries and 86% and 93%, respectively, for detecting occlusions. Accuracy was higher in the larger vessels-for example, calf (84%) compared with foot (71%). In 21% (22/105) of the segments graded differently on MR angiography than on X-ray digital subtraction angiography, it was believed that MR angiography was more likely to be correct than X-ray digital subtraction angiography because of visualization of late-filling arteries on MR angiography that did not opacify on X-ray digital subtraction angiography. CONCLUSION: Time-resolved 2D projection MR angiography accurately evaluates calf and pedal arteries without degradation from venous contamination.

Adult↗
PubMed2004

Soft tissue enhancement on time-resolved peripheral magnetic resonance angiography.

PURPOSE: To evaluate the incidence and locations of soft tissue enhancement on time-resolved two-dimensional projection magnetic resonance angiography (MRA) of the calf and foot. MATERIALS AND METHODS: Time-resolved two-dimensional projection MRA of the knee, calf, and foot, performed at 1.5 Tesla using the head coil, was retrospectively reviewed in 326 patients. Soft tissue enhancement of the foot was identified and graded by blinded review. Subsequently, patient medical records were reviewed to determine the presence or absence of diabetes, cellulitis, gangrene, and ulceration of the foot and presence of neuropathic joints. RESULTS: Enhancing spots were identified in 228 patients. For those feet without clinical abnormalities, diabetic patients had an average of 1.2 enhancing spots per foot, while nondiabetics had only 0.6 (P < 0.001). Higher-grade lesions were more prevalent in diabetics and in heavier patients. Of 64 patients with follow-up, 8 (13%) developed cellulitis (N = 4) or ulceration (N = 4) at the location of an enhancing spot, including 5 diabetic and 3 nondiabetic patients. CONCLUSION: Pedal soft tissue enhancement frequently occurs on time-resolved gadolinium (Gd):MRA of the feet. The etiology is uncertain, but the high frequency in diabetic patients and observation of progression to cellulitis/ulceration suggest this soft tissue enhancement may identify sites of subclinical pedal soft tissue injury.

Adult↗
PubMed2004

Three-dimensional MR angiography in imaging platinum alloy stents.

PURPOSE: To evaluate visualization inside platinum stents with three-dimensional contrast-enhanced magnetic resonance angiography (CE-MRA). MATERIALS AND METHODS: Breath-hold three-dimensional gadolinium (Gd) MRA was performed on 18 patients with 22 platinum stents in the renal (n = 18), celiac (n = 1), superior mesenteric (n = 1), and iliac (n = 2) arteries. Electronic calibers were used to measure the lumen diameter within the stent and just distal to the stent to calculate percent stenosis. MRA accuracy was determined from the difference between percent stenosis measured on MRA and digital subtracted angiography (DSA). The patients were imaged at flip angles of 45 degrees , 60 degrees , 75 degrees , 90 degrees , and 150 degrees . RESULTS: MRA demonstrated the stent lumen in all of the patients, with a mean difference between MRA and DSA of 21%. For stents oriented parallel to B0 (iliac arteries) the difference was only 10%, as compared to 22% for stents perpendicular to B0. The flip angle with the best agreement between MRA and DSA was 75 degrees (16%). CONCLUSION: The lumen of a platinum stent can be imaged with three-dimensional CE-MRA, although grading of restenosis has limited accuracy. The best results were obtained with a flip angle of 75 degrees and for stents in the iliac arteries parallel to B0.

Aged↗
PubMed2004

Imaging therapeutic response in human bone marrow using rapid whole-body MRI.

Whole-body imaging of therapeutic response in human bone marrow was achieved without introduced contrast agents using diffusion-weighted echo-planar magnetic resonance imaging of physiologic water. Bone marrow disease was identified relative to the strong overlying signals from water and lipids in other anatomy through selective excitation of the water resonance and generation of image contrast that was dependent upon differential nuclear relaxation times and self-diffusion coefficients. Three-dimensional displays were generated to aid image interpretation. The geometric distortion inherent in echo-planar imaging techniques was minimized through the acquisition of multiple axial slices at up to 12 anatomic stations over the entire body. Examples presented include the evaluation of therapeutic response in bone marrow during cytotoxic therapy for leukemia and metastatic prostate cancer and during cytokine administration for marrow mobilization prior to stem cell harvest.

Bone Marrow↗
PubMed2003

Diffusion-tensor MR imaging in children with developmental delay: preliminary findings.

PURPOSE: To determine whether diffusion-tensor magnetic resonance (MR) imaging can depict abnormalities in patients with a diagnosis of developmental delay but structurally normal brain MR imaging results. MATERIALS AND METHODS: Twenty pediatric patients who received a diagnosis of developmental delay underwent brain MR examinations, including diffusion-tensor MR imaging. The MR findings in these patients were compared with those in 10 age-matched neurodevelopmentally healthy children. Diffusion constant (Dav) and anisotropy were measured bilaterally in regions of interest in the centrum semiovale, corona radiata, internal capsule, corpus callosum, and subcortical white matter of the frontal and parieto-occipital lobes. By using a one-tailed Student t test in the positive direction for Dav and in the negative direction for anisotropy and P <.05 to indicate a significant difference, the Dav and anisotropy values for children with developmental delay were compared with those for children who were neurodevelopmentally healthy. RESULTS: The children with developmental delay had significant increases in Dav in all measured structures (P, <.001 to <.03). Significant decreases in anisotropy were detected in all white matter fiber tracts studied (P, <.001 to <.03) except the posterior limb of the internal capsule. CONCLUSION: In the children with developmental delay, diffusion-tensor MR imaging depicted decreases in anisotropy and increases in Dav in the white matter fiber tracts, which appeared to be normal at conventional MR imaging.

Anisotropy↗
PubMed2003

Atherosclerotic disease distribution in carotid and vertebrobasilar arteries: clinical experience in 100 patients undergoing fluoro-triggered 3D Gd-MRA.

PURPOSE: To determine how often three-dimensional gadolinium-enhanced magnetic resonance angiography (3D Gd-MRA) shows disease outside of the standard two-dimensional time-of-flight magnetic resonance angiography (2D TOF-MRA) imaging volume. MATERIALS AND METHODS: One hundred consecutive patients with known or suspected cerebrovascular disease were examined using fluoro-triggered 3D Gd-MRA with a 1.5 Tesla scanner. All vessel segments from the aortic arch to the circle of Willis were independently evaluated for the presence of occlusive disease, ulceration, aneurysm, and anatomic variations by two radiologists blinded to clinical information. Branch vessel and circle of Willis visibility were also assessed. Kappa statistics were calculated to determine interobserver agreement. RESULTS: Interobserver agreement for the degree of stenosis was good to excellent (kappa = 0.83-1.0). Disagreement was more frequent in the cases of mild stenoses and was less frequent for stenoses > or = 50%. In 38% of the patients, 3D Gd-MRA demonstrated either ulcerated plaques in carotid arteries (N = 14) or stenosis > or = 50% in great vessel (N = 20) and/or vertebral artery (N = 38) origins, none of which can be readily evaluated on standard TOF-MRA. CONCLUSION: Fluoro-triggered 3D Gd-MRA provides a comprehensive evaluation of the carotid arteries including all vessel segments from the aortic arch to the circle of Willis.

Adult↗