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S J Nelson

Publications and source records attributed to S J Nelson.

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

Phased array detectors and an automated intensity-correction algorithm for high-resolution MR imaging of the human brain.

Two- and four-coil phased array detectors were developed to increase the sensitivity and resolution of MR imaging of the human brain cortex, especially for detecting cortical dysplasias in pediatric epilepsy patients. An automated intensity correction algorithm based on an edge-completed, low-pass filtered image was used to correct the image intensity for the inhomogenous reception profile of the coils. Seven phased array coils were constructed and tested. The sensitivity of these coils was up to 600% higher at the surface of the cortex than that achieved with a conventional head coil and up to 30% greater at the center of the head. The sensitivity obtained was comparable with that of a conventional small surface coil, but extended over the larger dimensions of the array and previously inaccessible areas such as the top of the head. The advantages of the improved sensitivity are demonstrated with high resolution images of the brain.

Adult↗
PubMed1995

Proton spectroscopic imaging of the human brain using phased array detectors.

Two and four-coil phased array detectors have been developed to increase the sensitivity of proton spectroscopic imaging of the human brain. These include a quadrature figure-8 coil for the study of the vertex, several arrays of 2-4 small overlapping (6-8 cm diameter) circular coils and a combination figure-8 coil plus circular coil. These were constructed in our laboratory and tested to assess their utility for brain spectroscopy. Methods for optimally combining the data from the independent receivers based on the analytical coil maps or measured signal to noise ratios (SNRs) of the data were investigated. High spatial resolution (0.2-0.4 cm3 voxel size) two- or three-dimensional chemical shift images of normal brain were obtained in 17-minute acquisitions. These spatial resolutions are comparable to those previously obtained with conventional small surface coils, but the specialized detectors allow this sensitivity to be achieved for a larger region or for previously inaccessible areas such as the top of the head. The coverage and SNR increases demonstrated are similar to those obtained in magnetic resonance phased array imaging.

Brain↗
PubMed1995

Citrate as an in vivo marker to discriminate prostate cancer from benign prostatic hyperplasia and normal prostate peripheral zone: detection via localized proton spectroscopy.

OBJECTIVES: This study was designed to determine whether citrate levels detected by localized 1H spectroscopy could reliably discriminate regions of prostate adenocarcinoma from surrounding regions of normal peripheral zone and benign prostatic hyperplasia (BPH). METHODS: In 28 patients and 5 volunteers stimulated echo proton spectroscopy was used in conjunction with endorectal surface coils to obtain water-suppressed 1H spectra from regions of normal prostate peripheral zone, BPH, and prostate cancer. 1H spectra from prostate cancer patients were correlated with pathologic areas identified on T2-weighted endorectal coil magnetic resonance (MR) images and histologic study of the step-sectioned gland after surgery. RESULTS: The major finding of in vivo studies was consistently lower citrate levels in prostate cancer compared with BPH and normal prostate peripheral zone. This was reflected by significantly (P < 0.05) lower mean citrate/(creatine plus choline) peak area ratio observed for regions of cancer (0.67 +/- 0.17) compared with BPH (1.21 +/- 0.29) and normal peripheral zone (1.46 +/- 0.28). Moreover, there was no overlap of individual cancer and normal peripheral zone citrate ratios and no significant difference between citrate ratios in regions of normal peripheral zone in young volunteers (1.28 +/- 0.14) and age-matched patients (1.46 +/- 0.28). The observed alterations in vivo citrate levels were supported by citrate concentration data obtained from extracts of histologically proven samples of normal, benign, and malignant prostatic tissues removed at surgery. In vitro citrate levels in the normal peripheral zone (30.9 +/- 8.5 mumol/g wet weight) and BPH (46.3 +/- 5.4 mumol/g wet weight) were significantly higher than those for prostate cancer (3.74 +/- 0.54 mumol/g wet weight). CONCLUSIONS: These studies further demonstrate the potential of citrate as an in vivo marker for discriminating prostate cancer from surrounding regions of normal peripheral zone and BPH.

Adenocarcinoma↗
PubMed1995

Anthelmintic profile of the cyclodepsipeptide PF1022A in in vitro and in vivo models.

A novel cyclodepsipeptide of fungal origin, PF1022A, recently was reported to have anthelmintic activity. To supplement published reports and determine potential utility of PF1022A as a ruminant anthelmintic, the compound was examined in in vitro and in vivo models. Assays used measured motility of Haemonchus contortus (intrinsic drug potency), ATP levels (parasite death), and activity against H. contortus, Ostertagia ostertagi, and Trichostrongylus colubriformis in the jird (spectrum, potency, and efficacy by various routes). The potency of PF1022A in reducing motility is greater than commercial anthelmintics. Examination of ATP levels in PF1022A-paralyzed H. contortus indicates that worms are not killed, suggesting the compound acts as a neurotoxin in nematodes. In the jird, PF1022A has activity orally against each of the parasites studied and at doses comparable to all commercial anthelmintics, except the macrocyclic lactones which are more potent. Unfortunately, for some nematode species, parenteral delivery is ineffective at realistic doses.

Adenosine Triphosphate↗
PubMed1995

In vitro analysis of laser meniscectomy.

Partial meniscectomies were performed on 32 fresh human meniscal autopsy specimens. The following laser systems were tested: carbon dioxide (CO2), neodymium:yttrium aluminum garnet (Nd:YAG), potassium titanyl phosphate (KTP), holmium:YAG (Ho:YAG), and excimer. Meniscectomies with these lasers were compared with scalpel, mechanical, and electrocautery meniscectomies. Lasers were applied to specimens in and out of normal saline. Routine hematoxylin and eosin and sirius red sections were prepared for each specimen, and the depths of thermal changes were analyzed. Scanning electron microscopy was used to visualize the meniscectomy interface. Among these specimens, the scalpel and mechanical meniscectomies showed the least extension of cellular changes (range, 10-15 nm). The excimer laser caused the least tissue changes of the lasers tested. Tissue changes were less extensive with the pulsed CO2 laser than with the holmium:YAG, neodymium:YAG, and KTP lasers. Scanning electron microscopy showed that use of the scalpel meniscectomy resulted in the smoothest meniscectomy edge, followed by use of the excimer, CO2, holmium:YAG, neodymium:YAG, and KTP lasers. The most surface disruption occurred with electrocautery. Meniscectomies under saline required more energy and took longer in each case, with the holmium:YAG, neodymium:YAG, and CO2 laser cutting the best. Saline meniscectomies showed less thermal change. The CO2 and KTP lasers cut best in air.

Adult↗
PubMed1995

Principles of stabilization bite splint therapy.

The stabilization bite splint is discussed with regard to design, delivery, and clinical procedures that contribute to conservative appliance therapy. Indications for stabilization bite splint therapy and a clinical case report are presented.

Adult↗
PubMed1995

Multicystic encephalopathy: review of eight cases with etiologic considerations.

Multicystic encephalomalacia (MCE) is a rare lesion that arises during the perinatal period. Although hypoxic-ischemic insults may be responsible for this lesion, recent evidence suggests that herpesviruses may represent another etiologic agent. To elucidate the pathogenesis of MCE, eight cases collected over a 34-year period were evaluated for destructive lesions in gray and white matter. Immunocytochemical methods, in situ hybridization and polymerase chain reaction (PCR) methodology were employed to search for herpes simplex viruses types 1 and 2 (HSV1 and HSV2), cytomegalovirus (CMV), varicella zoster virus (VZV), Epstein-Barr virus (EBV) and JC variant of papovavirus (JCV). Review of the clinical histories revealed that there had been a complicated labor and delivery in 6/7 cases. Neuropathological lesions consisted of extensive tissue destruction, neuronal loss and gliosis in hemispheric white matter, cerebral cortex, basal ganglia, thalamus, cerebellum and brainstem tegmentum. Only one case showed evidence of latent HSV infection by PCR. CMV, VZV, JCV and EBV were not detected. Arteriopathy was noted in one case. The widespread nature of the lesions and their association with perinatal ischemia suggest that severe hypoxia may be the more common etiology of MCE. Term infants appear especially susceptible to this type of cerebral damage.

Autopsy↗
PubMed1995

Merging terminologies.

A terminology is a systematic, authoritative collection of concept names, or terms, in some domain. No single terminology names all the important concepts in biomedicine. One approach to creating a more comprehensive biomedical terminology is to merge existing biomedical terminologies, as the UMLS( Metathesaurus( has done for the last six years. Because existing terminologies may overlap--for example, one terminology may name a concept also named by another terminologyQthe terminologies in the Metathesaurus must be merged. Some terminologies suggest merges through their structure or content e.g., they suggest synonyms or connections to other terminologies; other merges can be suggested by algorithm. Regardless, all merges in the Metathesaurus must be approved by a human editor with appropriate domain knowledge. By the time Meta-U96 is released early in 1996, one prototype and seven released versions of the Metathesaurus will have been produced by a sequence of four qualitatively different methods, named for the way in which they merge terms: #1 "Term Rewrite Rules, #2 "Transitive Closure on Facts," #3 "Fact-at-a-Time Concept Merging," and #4 "Action-at-a-Time Object Processing." The development of each method has been constrained by the annual Metathesaurus release schedule. The first two methods made the best use of limited computational resources, and the last two make better use of human editing resources.

National Library of Medicine (U.S.)↗
PubMed1995

Identifying concepts in medical knowledge.

The barrier word method of identifying nominal phrases in text, using a very long barrier word list, was evaluated in two different sets of text. In a sample of 10 paragraphs from the Medical Knowledge Self-Assessment Program of the American College of Physicians, the yield of nominal phrases as a percent of total chunks isolated was 66%. Some 500,000 chunks were isolated from Principles and Practice of Oncology (PPO). 38% of these chunk-occurrences were of chunks which matched to 10,000 concept names in Meta-1.4, the most recent version of the UMLS Metathesaurus. 50 paragraphs from PPO were chosen at random. Co-occurrences of concepts in those paragraphs were reviewed. 42 of the paragraphs had unique or infrequently occurring co-occurrences which described closely the major thrust of the paragraph.

Medical Oncology↗
PubMed1995

Accessing oncology information at the point of care: experience using speech, pen, and 3-D interfaces with a knowledge server.

Oncologists' information needs arise at diverse times and settings. For example: "Is superior vena cava syndrome a medical emergency?" Our collaborative group is developing a system that supports an interface with combinations of spoken, gestural, and simulated three-dimensional manipulation to help an oncologist focus on the information need, not the system. The system requires a small amount of input from the oncologist, and then anticipates what information is pertinent to the patient at hand, based on the sources it has available. The system makes use of a "Knowledge Server" to find relevant information. The Knowledge Server uses selected data for the particular patient from a Computer-based Patient Record (CPR) to provide context for the information needs. The Knowledge Server leverages the Unified Medical Language System (UMLS) resources as well as relevant communications standards. A layered, interaction protocol is used to help manage the fulfillment of information needs. Each of the oncology knowledge sources is transformed into a uniform representation that utilizes both its formal schema (e.g., its table of contents) and its concepts and words indexed through the UMLS Metathesaurus. Our focus on the appropriate use of information from a CPR, and on anticipating oncologists' information needs, resulted from our study of several longitudinal patient scenarios. We believe that our use of scenario-based design techniques will help to ensure the system's success.

California↗
PubMed1995

The representation of meaning in the UMLS.

The UMLS knowledge sources provide detailed information about biomedical naming systems and databases. The Metathesaurus contains biomedical terminology from an increasing number of biomedical thesauri, and the Semantic Network provides a structure that encompasses and unifies the thesauri that are included in the Metathesaurus. This paper addresses some fundamental principles underlying the design and development of the Metathesaurus and Semantic Network. It begins with a description of the formal properties of thesauri, including the Metathesaurus, and the formal properties of the Semantic Network. It continues with consideration of the principle of semantic locality and how this is reflected in the UMLS knowledge sources. The paper concludes with a discussion of the issues involved in attempting to re-use knowledge and the potential for re-use of the UMLS knowledge sources.

Artificial Intelligence↗
PubMed1995

Navigating to knowledge.

One way to fulfill point-of-care knowledge needs is to present caregivers with a visual representation of the available "answers". Using such a representation, caregivers can recognize what they want, rather than have to recall what they need, and then navigate to an appropriate answer. Given selected pieces of information from a computer-based patient record, an interface can anticipate certain knowledge needs by initializing caregiver navigation in a semantic neighborhood of answers likely to be relevant to the patient at hand. These notions draw heavily on two collaborative projects--the U.S. National Library of Medicine Unified Medical Language System and the U.S. National Cancer Institute Knowledge Server. Both of these projects support navigation because they make the structure of medical knowledge explicit in a way that can be exploited by human interfaces.

Artificial Intelligence↗
PubMed1994

The role of the UMLS in 'storing' and 'sharing' across systems.

We will argue that 'sharing', 're-use', 're-purposing', and 'addition' of health care information is difficult, intrinsically; that the best way to overcome the difficulty is to start doing it, as soon as possible, and that the UMLS Knowledge Sources provide the best place to start. We recommend that the UMLS be used as a default source of biomedical concept names and relationships, as a comprehensive, data-based, 'reference model', and as an example of a large, ecumenical, evolving, continuously updated source of re-usable health care information.

Computer User Training↗
PubMed1994

Glial cytokines as neuropathogenic factors in HIV infection: pathogenic similarities to Alzheimer's disease.

The mechanisms by which human immunodeficiency virus (HIV) infection provokes progressive neurodegeneration and dementia in acquired immunodeficiency syndrome (AIDS) remain obscure. In HIV-infected (HIV+) individuals, we found that the brain cells preferentially infected by HIV, viz. the microglia, were abundant, activated, and intensely immunopositive for interleukin-1 alpha (IL-1 alpha), an immune response-generated cytokine that increases the synthesis and processing of beta-amyloid precursor proteins (beta-APP) and promotes proliferation and activation of astroglia. We also found an increase in the number of activated astroglia expressing elevated levels of S100 beta, a cytokine that increases intraneuronal calcium levels and promotes excessive growth of neuronal processes (neurites). These glial changes were accompanied by increased expression of beta-APP immunoreaction product in neurons and overgrown (dystrophic) neurites. In addition, some neurons contained monoclonal antibody Tau-2 immunopositive, neurofibrillary tangle-like structures. Our findings provide evidence that glial activation with increased expression of IL-1 alpha and S100 beta may be important in the neuropathogenesis of AIDS dementia. We propose that HIV infection promotes excessive microglial IL-1 alpha expression with consequent astrogliosis and increased expression of S100 beta. Overexpression of these two cytokines may then be involved in AIDS neuropathogenesis by inducing gliosis, growth of dystrophic neurites, and calcium-mediated neuronal cell loss in AIDS.

Adult↗
PubMed1994

Expression of HIV-1 and interleukin-6 in lumbosacral dorsal root ganglia of patients with AIDS.

We examined the immunopathology and the expression of human immunodeficiency virus type 1 (HIV-1) in lumbosacral dorsal root ganglia (DRGs) from 16 patients with acquired immunodeficiency syndrome (AIDS) and 10 HIV-1-seronegative controls. Using in situ hybridization, we detected HIV-1 RNA in a few perivascular cells in DRGs from five of 16 AIDS patients (31%). In addition, using polymerase chain reaction, we detected HIV-1 DNA more frequently in DRGs from four of five AIDS patients (80%) examined. We detected interleukin-6 (IL-6) immunoreactivity in endothelial cells in DRGs from seven of 16 AIDS patients (44%) but from none of 10 HIV-1-seronegative controls (0%). We found more nodules of Nageotte, CD8+ T lymphocytes, and intercellular adhesion molecule-1 (ICAM-1)-positive endothelial cells and mononuclear cells in DRGs from AIDS patients than in DRGs from controls. Increased numbers of nodules of Nageotte in DRGs of AIDS patients were associated with detection of HIV-1 RNA by in situ hybridization and detection of IL-6 by immunohistochemistry. We conclude that low levels of replication of HIV-1, through cytotoxic T lymphocytes or expression of cytokines, may play a role in the subclinical degeneration of sensory neurons frequently observed in DRGs of AIDS patients.

Acquired Immunodeficiency Syndrome↗