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Biomedical subjects

K Preston

Publications and source records attributed to K Preston.

At least 19 recordsLinked to original sources
PubMed1992

New techniques for three-dimensional data analysis in histopathology.

This paper describes two three-dimensional (3D) analytical techniques based on 3D mathematical morphology that have been found useful in quantifying the 3D spatial distribution of S-phase cells in a tubular tumor of the human breast. One technique is based on determining the normalized radial distribution of the S-phase cells with respect to the central axis of the tumor. The other technique is a novel extension of the polyhedra of Voronoi to quantify the distribution. The Voronoi polyhedron of a given S-phase cell nucleus is that polyhedron of minimal volume defined by planes all of which are perpendicular bisectors of the vectors extending from the given cell to all other S-phase cells in the tumor. Methods are demonstrated for generating these polyhedra and for histogramming their volumes. An illustration is given of using the histogram to sort the S-phase cells according to their 3D positional relationships. Displays showing the sorted cells in 3D and their associated Voronoi polyhedra are provided.

Adult↗
PubMed1991

Comparison of autofocus methods for automated microscopy.

Traditional autofocus methods were designed for microscopes driven by single processor computers. As computers are developed that exploit massive parallelism when acquiring and analyzing images, parallel cellular logic techniques became available to focus automatically. This paper introduces the reader to both cellular logic techniques for autofocus and a new spectral moment autofocus measure. It then compares these methods with more traditional autofocus methods. It is shown that traditional methods based on measurements of image power-give the best results when tested on one set of real images and two sets of synthetic images. The next best methods are the cellular logic and spectral moment techniques, while the worst are those based on the image probability density function or histogram.

Automation↗
PubMed1990

Heptavax-B in pediatric dialysis patients: effect of systemic lupus erythematosus. Chesapeake Pediatric Nephrology Study Group.

Twenty-three pediatric dialysis patients [6 hemodialysis (HD) and 17 peritoneal dialysis (PD)], with a mean age of 13.9 years, were vaccinated against hepatitis B virus and their seroconversion rates were analyzed. There was no significant difference in the mean duration of dialysis between the HD and PD groups, or between responders and nonresponders to the vaccine. In the HD group, there was a response rate of 83.3% while the PD patients had a response rate of 88.2%. The only patients failing to seroconvert after the three vaccine series all had systemic lupus erythematosus and were taking oral corticosteroids.

Adolescent↗
PubMed1990

Use of three-dimensional mathematical morphology in analyzing histologic images, with application to the subtyping of follicular lymphomas.

Ongoing research on the differentiation between small-cell and large-cell follicular lymphomas ascertained that image analysis by three-dimensional morphologic transforms permits subtyping of follicular lymphomas with greater accuracy and reproducibility than can be accomplished visually by expert pathologists. The present studies improved the use and interpretation of the minimum tracking algorithm and identical to-filters (binary ranking filters). These filters operate on the voxels that constitute the three-dimensional space encodings of gray-level images and are implemented by the Triakis software system.

Algorithms↗
PubMed1989

Evaluation of algorithms for ratio imaging in fluorescence microscopy.

Ratio imaging in fluorescence microscopy is used in measuring parameters such as pH, pCa, cytoplasmic porosity, and the relative concentration of fluorescent analogs within single cells. The fastest method for ratio imaging is to use lookup tables on special-purpose image processors. Since lookup tables store integers in integer addresses, using a lookup table will generate rounding errors. The magnitude of the error will depend on the transformation performed and on the number of levels used in the lookup table. We examined ratio imaging by lookup table and computed the errors generated by both inversion and log subtraction methods. Both uniformly fluorescing fields and fluorescing cell images were employed to provide data for use in confirming our calculations and illustrating both the magnitude and spatial incidence of errors. It is shown that, through proper design of lookup tables, a significant reduction can be made in the errors generated in comparison with common methods available in most image processors.

Algorithms↗
PubMed1989

Effects of chronic alcoholism on perception of hierarchical visual stimuli.

Visuospatial processing in chronic alcoholism was investigated by asking subjects to make similarity judgements of hierarchically constructed visual stimuli. Comparison figures were similar to a standard figure at the global or local level. Alcoholics were less influenced by the global patterns in their similarity judgements than were controls. On the WAIS-R Block Design subtest, alcoholics were also more likely than controls to distort the outer configuration of the design. Results indicate that alcoholism affects global processing on both experimental visuoperception tasks and on clinical measures of visuospatial ability. Implications for models of alcoholic dysfunction are discussed.

Adult↗
PubMed1989

Subclassification of follicular lymphomas by computerized image processing.

Non-Hodgkin's lymphomas with a follicular pattern are subdivided on the basis of morphologic criteria into four subtypes. Each subtype has a distinctive natural history, response to therapy and survival, and precise histologic diagnosis is essential for optimal treatment. However, recent studies by a panel of seven expert hematopathologists showed that there was a 20% to 40% likelihood of disagreement in subtyping non-Hodgkin's follicular lymphomas; thus, the likelihood of a patient receiving inappropriate treatment is high. To resolve some of the problems relating to subjective morphologic diagnosis, we have continued to investigate the possibility of using computerized image analysis to perform automated subtyping of follicular lymphomas. In the portion of the study reported herein, a total of 37 cases were selected from the set subtyped by the panel of expert hematopathologists, and digitized images of slides from each case were processed by computer. The computer-generated subtypes were compared with those arrived at by the panel. For the cases analyzed, the computer subtyping was at least as good as, and in some instances superior to, that of most of the expert panelists.

Adult↗
PubMed1987

Subclassification of follicular lymphomas by computerized microscopy.

The pilot feasibility study reported was carried out to determine whether computerized morphometry could be used to discriminate between different subtypes of follicular lymphomas. Thirteen cases of follicular lymphomas of the small cell and large cell types were examined by map-guided computerized microscopy. Initially, each specimen was digitized over a 5,120- X -5,120-microns area. Follicle maps depicting well-defined follicles were generated from these digitized images and used to guide a robot microscope to examine follicular center cells using from 20 to 100 fields, each 160 X 160 microns. Mathematical morphology was used to estimate the number of connected regions within each field examined. Based on the assumption that each connected region corresponded to a cell nucleus, it was expected that the number of connected regions found per unit area would correlate with the number of cells per unit area. Three prototypical small cell lymphomas and three prototypical large cell lymphomas were used as a training set to calibrate the methodology. Data obtained on these prototypical cases were used to establish statistical decision boundaries. Seven test cases, judged to be less typical but classifiable by experts, were then examined. Five of the seven were classified correctly, and the remaining two were identified as outliers. These results suggest that subclassification of follicular lymphomas may be aided by computerized microscopy. This pilot feasibility study is currently being expanded using a much larger sample of case material.

Diagnosis, Differential↗
PubMed1986

Monocular and binocular acuity estimation in 18- to 36-month-olds: acuity card results.

The acuity card procedure is a useful method for measuring visual acuity in infants 1 to 12 months of age. The results of the present study indicate that the procedure is also a viable method for estimating acuity in children 18 to 36 months of age. Monocular and binocular estimates of acuity were obtained with the acuity card procedure on 36 normal children, 9 each at ages 18, 24, 30, and 36 months. At each of the ages, means and SD's of acuity estimates agreed well with acuity norms from established operant procedures. Mean durations for monocular and binocular estimates averaged 2 to 4 min, and nearly 100% of children were tested successfully both monocularly and binocularly. The flexibility of the required response and the short test times make the acuity cards a promising test of visual acuity in this typically difficult-to-test age range.

Child Development↗
PubMed1986

Assessment of visual acuity in infants and children: the acuity card procedure.

The 'acuity card' procedure described here is a simplified method of testing visual acuity of infants and young children, and has been developed to allow preferential looking to be assessed in a laboratory or clinic. A higher proportion of children can be tested successfully than has been reported for more traditional procedures. Initial studies indicate that the acuity card procedure is a fast, accurate method for assessing the acuity of normal infants and children, and those with visual or neurological impairments, across a wide age-range and in both clinical and laboratory settings.

Child Development↗
PubMed1986

High-resolution image analysis.

In many departments of cytology, cytogenetics, hematology, and pathology, research projects using high-resolution computerized microscopy are now being mounted for computation of morphometric measurements on various structural components, as well as for determination of cellular DNA content. The majority of these measurements are made in a partially automated, computer-assisted mode, wherein there is strong interaction between the user and the computerized microscope. At the same time, full automation has been accomplished for both sample preparation and sample examination for clinical determination of the white blood cell differential count. At the time of writing, approximately 1,000 robot differential counting microscopes are in the field, analyzing images of human white blood cells, red blood cells, and platelets at the overall rate of about 100,000 slides per day. This mammoth through-put represents a major accomplishment in the application of machine vision to automated microscopy for hematology. In other areas of automated high-resolution microscopy, such as cytology and cytogenetics, no commercial instruments are available (although a few metaphase-finding machines are available and other new machines have been announced during the past year). This is a disappointing product, considering the nearly half century of research effort in these areas. This paper provides examples of the state of the art in automation of cell analysis for blood smears, cervical smears, and chromosome preparations. Also treated are new developments in multi-resolution automated microscopy, where images are now being generated and analyzed by a single machine over a range of 64:1 magnification and from 10,000 X 20,000 to 500 X 500 in total picture elements (pixels). Examples of images of human lymph node and liver tissue are presented. Semi-automated systems are not treated, although there is mention of recent research in the automation of tissue analysis.

Blood Cell Count↗
PubMed1986

Visual acuity screening of infants and young children with the acuity card procedure.

A new acuity test for infants and young children between 1 and 36 months of age is described. The test was used to evaluate the acuities of 66 infants and young children during a one-day vision screening. At least one estimate of visual acuity was obtained from 63 of the 66 children. Fifty-two of the children completed two monocular acuity tests (or two monocular tests plus a binocular test). The average total test time for these 52 children was less than 15 minutes. Results indicate that the acuity card procedure can be used as a complement to standard optometric tests for large-scale screening of infants and young children.

Child, Preschool↗