Biomedical subjects

M A Vivino

Publications and source records attributed to M A Vivino.

5 recordsLinked to original sources

PubMed1996

Constructing retinal fundus photomontages. A new computer-based method.

PURPOSE: To develop computer algorithms for reconstructing 24-bit color, wide-angle composite retinal fundus images from a set of adjacent 45 degrees fundus slides. The authors present the description, technical details, and results of the image reconstruction technique. METHODS: Patients with retinal degeneration underwent fundus photography with a 45 degrees field-of-view fundus camera. Individual photographic slides were digitized for creating fundus montages. Background variations in individual 45 degrees images were modeled to first- or second-order two-dimensional polynomial functions to generate a background image. The background image was subtracted from the original image to obtain background corrected image. Background corrected images were registered and spatially transformed using a first- or second-order two-dimensional polynomial warp model to reconstruct a composite retinal fundus montage. RESULTS: The authors successfully reconstructed 24-bit color, 100 degrees field-of-view, composite retinal fundus images. The computer-reconstructed montages are an improvement over manually generated montages because computer analysis can be performed on the computer-based montages. In addition, background variations and discontinuities between individual photographs observed in manually generated montages are reduced greatly in computer-generated montages. Most important, the computer-generated montages are better aligned than the manually generated photomontages. CONCLUSIONS: This method of reconstructing a wide-angle composite retinal fundus image from a set of adjacent small- and wide-angle fundus slides is a new tool for creating montages as large as 100 degrees field of view. The computer-generated montages may be used for documenting and quantifying retinal findings. This can greatly assist studies of retinal manifestations of diseases, such as gyrate atrophy, retinitis pigmentosa, sickle cell disease, and acquired immune deficiency syndrome.

Algorithms↗

PubMed1995

Quantitative analysis of retroillumination images.

We have developed a semi-automated image processing system for analysis and evaluation of retroillumination images. This paper describes methods used to compensate for illumination variations in the images, separation of data into cataractous and non-cataractous portions, how quantitative measurements are made and how they assess the pathological condition. In addition to the traditional area measurement, this system computes the net integral of density and several measurements involving the location of the opacity in relation to the pupillary margin. The computer measures of area, integral of density, area centrality, weighted area, density centrality and weighted density provide more data than previously described systems. Data produced by this interactive and automated system can be used in studies of posterior subcapsular and cortical cataracts, and to study the effect of these opacities on vision.

Cataract↗

PubMed1994

Reproducibility study of posterior subcapsular opacities on the NEI retroillumination image analysis system.

We developed a semi-automated retroillumination image analysis system which combines speed, ease of operation and interactive analysis. The system measures cataract area and integral of cataract density (ID). For system reproducibility evaluation, 20 eyes with posterior subcapsular opacities were captured twice by two photographers. Variability was estimated under a random effects analysis of variance model. Measurement errors for area and for ID were each small contributors to total variability (the sum of variability between study eyes plus measurement error), being 0.4% and 0.1% respectively. The largest contributor to area measurement error was image analysis variability (97%). For ID measurement error, the variability in images (44%) and in image analysis (46%) were major contributors. The reproducibility is comparable to previously described retroillumination analysis systems. This easy to use system may therefore be useful in clinical research studies including possible clinical trials of anti-cataract drugs.

Adolescent↗

PubMed1993

Cardiovascular flow velocity measurements by 2D Doppler imaging for assessment of vascular function.

Clinical two-dimensional (2D) Doppler ultrasound flow velocity measurement is important for determination of arterial wall shear stress, blood-tissue exchange, myocardial and valvular function. Such 2D Doppler flow velocity images are usually displayed in color, superimposed on the gray-scale, cross-section structural images of the tissue. There are several limitations to this technique of flow measurement, some due to the instrumentation and some to the way the measurement is made. In this report we concentrate on the latter, identifying the main causes of errors and distortion, and outlining the methodology for minimizing them. The suggested method takes into account the spatial location and orientation of both the ultrasound transducer and the blood vessel. It allows quantification of vascular flow patterns, thus enhancing the usefulness of this important non-invasive diagnostic tool.

Arteries↗

PubMed1993

Development of a Scheimpflug slit lamp camera system for quantitative densitometric analysis.

We have developed a computerised video system for accurate quantification of lens opacities from Scheimpflug images. Using a modified Zeiss Scheimpflug camera and Macintosh computer, the system software can warn of improper exposure and can provide immediate results of cataract progression on individual patients. These results are obtained from a novel technique which automatically divides the lens into anatomical regions and computes regional densities in the standard optical density unit. Because of the system's speed, the operator can properly capture and analyse a cataract in seconds, compare results with past patient records and give feedback to the patient on the results of the analysis. The system provides the appropriate data integrity and formats for documenting and monitoring lens opacities. Such a system will be useful in longitudinal studies of cataracts (i.e. for natural history and anti-cataract drug trials).

Cataract↗