Biomedical subjects

Leo Grady

Publications and source records attributed to Leo Grady.

4 recordsLinked to original sources

PubMed2006

Random walks for image segmentation.

A novel method is proposed for performing multilabel, interactive image segmentation. Given a small number of pixels with user-defined (or predefined) labels, one can analytically and quickly determine the probability that a random walker starting at each unlabeled pixel will first reach one of the prelabeled pixels. By assigning each pixel to the label for which the greatest probability is calculated, a high-quality image segmentation may be obtained. Theoretical properties of this algorithm are developed along with the corresponding connections to discrete potential theory and electrical circuits. This algorithm is formulated in discrete space (i.e., on a graph) using combinatorial analogues of standard operators and principles from continuous potential theory, allowing it to be applied in arbitrary dimension on arbitrary graphs.

Algorithms↗

PubMed2006

Isoperimetric graph partitioning for image segmentation.

Spectral graph partitioning provides a powerful approach to image segmentation. We introduce an alternate idea that finds partitions with a small isoperimetric constant, requiring solution to a linear system rather than an eigenvector problem. This approach produces the high quality segmentations of spectral methods, but with improved speed and stability.

Algorithms↗

PubMed2005

Random walks for interactive organ segmentation in two and three dimensions: implementation and validation.

A new approach to interactive segmentation based on random walks was recently introduced that shows promise for allowing physicians more flexibility to segment arbitrary objects in an image. This report has two goals: To introduce a novel computational method for applying the random walker algorithm in 2D/3D using the Graphics Processing Unit (GPU) and to provide quantitative validation studies of this algorithm relative to different targets, imaging modalities and interaction strategies.

Algorithms↗

PubMed2004

Multiple-year experience in the diagnosis of viral central nervous system infections with a panel of polymerase chain reaction assays for detection of 11 viruses.

BACKGROUND: Polymerase chain reaction (PCR) is becoming more common in diagnostic laboratories. In some instances, its value has been established. In other cases, assays exist, but their beneficial use has not been determined. This article summarizes findings from 3485 patients who underwent testing over a 6-year period in our laboratory. METHODS: A panel of PCR assays was used for the detection of a range of viruses associated with central nervous system (CNS) infections. PCR results were analyzed in conjunction with information about patient age and sex, the time between onset and specimen collection, and other variables. Medical chart review was conducted for 280 patients to gain diagnostic and epidemiologic insight with regard to cases of unresolved encephalitis. RESULTS: A total of 498 PCR-positive samples (14.3%) were detected. Enteroviruses accounted for the largest number (360 [72.3%]) of positive PCR results, followed by herpes simplex virus (76 [15.3%]), varicella-zoster virus (29 [5.82%]), and West Nile virus (WNV) (18 [3.61%]). Of 360 patients who tested positive for enterovirus, only 46 met the Centers for Disease Control and Prevention's encephalitis definition. It resulted in the greatest decrease (87.2%) in positive PCR results. Overall, the PCR positivity rate for specimens collected within 5 days after illness onset was 17.2%, compared with 8.6% for specimens collected > or =6 days after onset. CONCLUSIONS: The value of PCR in the diagnosis of viral infections has been established. PCR is of lower value in the detection of WNV in CNS, compared with serological testing, but is of greater value in the detection of other arboviruses, particularly viruses in the California serogroup. Medical chart reviews indicated that apparent CNS infection resolves in approximately 50% of cases.

Adolescent↗