Biomedical subjects

W E Snyder

Publications and source records attributed to W E Snyder.

At least 19 recordsLinked to original sources

PubMed1999

Content-based image retrieval in picture archiving and communications systems.

We propose the concept of content-based image retrieval (CBIR) and demonstrate its potential use in picture archival and communication system (PACS). We address the importance of image retrieval in PACS and highlight the drawbacks existing in traditional textual-based retrieval. We use a digital mammogram database as our testing data to illustrate the idea of CBIR, where retrieval is carried out based on object shape, size, and brightness histogram. With a user-supplied query image, the system can find images with similar characteristics from the archive, and return them along with the corresponding ancillary data, which may provide a valuable reference for radiologists in a new case study. Furthermore, CBIR can perform like a consultant in emergencies when radiologists are not available. We also show that content-based retrieval is a more natural approach to man-machine communication.

Consultants↗

PubMed1999

Suboccipital resection of a medial acoustic neuroma with hearing preservation.

BACKGROUND: Many reports indicate that acoustic neuromas greater than 2.0 cm should be removed without hearing preservation attempted, even if hearing is present preoperatively. These studies advocate a translabyrinthine approach because the likelihood of hearing preservation is low. Medial acoustic neuromas, unlike the more common lateral tumors that involve the internal auditory canal, originate medial to that portion of the eighth nerve complex where the cochlear and vestibular nerves are fused. This anatomical feature suggests that these tumors may be amenable to resection with hearing preservation. METHODS: A patient with a 3.5 cm medial acoustic neuroma and useful preoperative hearing is presented. RESULTS: Gross total tumor removal with functional hearing was achieved after a two-stage procedure using a suboccipital approach. CONCLUSION: Based on the anatomico-pathologic features in this case, we believe that, if a patient has reasonable preoperative hearing (speech discrimination score > 70%) and a medial acoustic neuroma, an approach to preserve hearing should be considered regardless of tumor size.

Female↗

PubMed1998

Left-ventricle boundary detection from nuclear medicine images.

We present here a new algorithm for segmentation of nuclear medicine images to detect the left-ventricle (LV) boundary. In this article, other image segmentation techniques, such as edge detection and region growing, are also compared and evaluated. In the edge detection approach, we explored the relationship between the LV boundary characteristics in nuclear medicine images and their radial orientations: we observed that no single brightness function (eg, maximum of first or second derivative) is sufficient to identify the boundary in every direction. In the region growing approach, several criteria, including intensity change, gradient magnitude change, gradient direction change, and running mean differences, were tested. We found that none of these criteria alone was sufficient to successfully detect the LV boundary. Then we proposed a simple but successful region growing method--Contour-Modified Region Growing (CMRG). CMRG is an easy-to-use, robust, and rapid image segmentation procedure. Based on our experiments, this method seems to perform quite well in comparison to other automated methods that we have tested because of its ability to handle the problems of both low signal-to-noise ratios (SNR) as well as low image contrast without any assumptions about the shape of the left ventricle.

Heart Ventricles↗

PubMed1998

Performance evaluation of filtered backprojection reconstruction and iterative reconstruction methods for PET images.

The filtered backprojection (FBP) algorithm and statistical model based iterative algorithms such as the maximum likelihood (ML) reconstruction or the maximum a posteriori (MAP) reconstruction are the two major classes of tomographic reconstruction methods. The FBP method is widely used in clinical setting while iterative methods have attracted research interests in the past decade. In this paper we studied the performance of the FBP, the ML and the MAP methods using simulated projection data. The experiment showed that the MAP algorithm generated superior image quality in terms of the bias, the variance, and the average mean squared error (MSE) measures.

Algorithms↗

PubMed1998

Chiari III malformation treated with CSF diversion and delayed surgical closure.

Chiari III malformations are extremely rare hindbrain malformations that are associated with a high early mortality rate, or severe neurologic deficits in the survivors. The preferred treatment is early operative closure and CSF shunting. We report a case of a newborn infant with a Chiari III malformation with displacement of the brainstem and cerebellum into the cervical encephalocele which precluded immediate operative closure of the defect. Instead, a ventriculoperitoneal shunt was placed and the patient was followed with serial imaging studies. The child survived. The shunt allowed the brainstem and cerebellum to regress into the cervical spinal canal as the dilated cerebral aqueduct and fourth ventricle decompressed. A delayed closure of the cervical encephalocele was performed at 30 months of age. Cerebrospinal fluid diversion with delayed closure may be an option for large lesions.

Arnold-Chiari Malformation↗

PubMed1994

Noise removal from multiple MRI images.

We introduce a novel technique for magnetic resonance image (MRI) restoration, using a physical model (spin equation). We determine a set of three basis images (proton density and nuclear relaxation times) from the MRI data using a nonlinear optimization method, and use those images to obtain restorations of the original image. MRIs depend nonlinearly on proton density, two nuclear relaxation times, T1 and T2, and two control parameters, echo time (TE) and relaxation time (TR). We model images as Markov random fields and introduce a maximum a posteriori restoration method, based on nonlinear optimization, which reduces noise while preserving resolution.

Algorithms↗

PubMed1987

A case report and review of band keratopathy.

A five-year-old male presented with band keratopathy as the first sign of proximal renal tubular acidosis. The band keratopathy was progressive with decreasing visual acuity. Treatment with EDTA was repeated in each eye with only minimal improvement. The pediatric renal service found the serum calcium to be no higher than 10.5 mg% and phosphorus no higher than 6.8 mg%. The calcium-phosphorus product was in the range of 60-65. Band keratopathy can be visually incapacitating and has multiple etiologies. Factors other than elevated calcium concentrations must predispose to development of this disorder. Certain of these factors and a review of band keratopathy are presented in the following article.

Acidosis, Renal Tubular↗

PubMed1980

So you're going to give a talk! I know you hear me, but are you listening?

Explore the source record for details and available documents.

Veterinary Medicine↗

PubMed1977

Pharmacokinetics of sulphadimethoxine in cattle.

Four healthy Angus steers received a single rapid intravenous injection of sulphadimethoxine at a dose of approximately 55 mg/kg. The elimination half-life determined from plasma concentration-time data was approximately 12-5 h, and the volume of distribution was 31-0 per cent of body weight. Animals also received sulphadimethoxine intravenously or orally at a loading dose of approximately 55 mg/kg, followed by sustaining oral doses of approximately 27-5 mg/kg at 24, 48 and 72 h. It was demonstrated that oral maintenance doses served to sustain sulphonamide plasma concentrations achieved with the loading dose.

Administration, Oral↗

PubMed1976