Biomedical subjects

Russell Chipman

Publications and source records attributed to Russell Chipman.

3 recordsLinked to original sources

PubMed2005

Wavelength dependence of the apparent diameter of retinal blood vessels.

Imaging of retinal blood vessels may assist in the diagnosis and monitoring of diseases such as glaucoma, diabetic retinopathy, and hypertension. However, close examination reveals that the contrast and apparent diameter of vessels are dependent on the wavelength of the illuminating light. In this study multispectral images of large arteries and veins within enucleated swine eyes are obtained with a modified fundus camera by use of intravitreal illumination. The diameters of selected vessels are measured as a function of wavelength by cross-sectional analysis. A fixed scale with spectrally independent dimension is placed above the retina to isolate the chromatic effects of the imaging system and eye. Significant apparent differences between arterial and venous diameters are found, with larger diameters observed at shorter wavelengths. These differences are due primarily to spectral absorption in the cylindrical blood column.

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PubMed2005

In vitro multispectral diffuse reflectance measurements of the porcine fundus.

PURPOSE: To quantify the reflectance of the swine fundus as a function of illumination angle and wavelength using a novel technique of intravitreal illumination. METHODS: Enucleated swine eyes were illuminated with a scanning monochromator coupled to a fiber-optic probe placed in the vitreous at several locations. Intravitreal illumination was used to reduce the effects of extraneous reflections and scatter from the anterior structures of the eye, including glints from the internal limiting membrane and blood vessels. Intravitreal illumination provided different light paths and additional information to apply to retinal reflectance modeling. A 25-mm(2) region of the illuminated fundus was imaged while the angle of illumination was varied over a maximum range of 22 degrees . Multispectral images from areas free of large blood vessels were acquired. The diffusely reflected intensity was integrated over the pupil with a solid angle of 0.028 steradians. The spectral reflectance function was calculated for multiple illumination angles. RESULTS: Multispectral fundus image sets were obtained for two enucleated swine eyes by using intravitreal illumination. The fundus spectral reflectance function showed decreasing reflectance with increasing illumination angle, rapid changes in the 430- to 480-nm range, and a fairly consistent reflectance decrease for 480 to 700 nm. CONCLUSIONS: Variations in fundus spectral reflectance with change in the illumination angle were found to deviate from Lambertian behavior, varying from Lambertian by 5% across the spectrum in one sample and 20% in a second sample. Intravitreal illumination resulted in markedly decreased extraneous reflections.

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PubMedDate not supplied

Evanescent-imaging-ellipsometry-based microarray reader.

We describe the development of a label-less ellipsometric imaging microarray reader. The ability of the ellipsometric microarray reader to measure binding of sample to microarray surface is verified using oligonucleotide complementary DNA (cDNA) microarrays. Polarized light illuminates the microarray surface through a glass substrate at an angle beyond the critical angle and changes in the polarization of totally internally reflected light resulting from binding events on the microarray surface are measured. This polarization change is used to measure the thickness of biomolecules bound to the microarray. A prototype ellipsometric imaging microarray reader is constructed and calibrated, and the performance is evaluated with cDNA microarrays. The microarray reader measures changes in refractive index changes as small as 0.0024 and thickness changes as small as 0.28 nm. The optimization of angle of incidence and substrate refractive index necessary to achieve high sensitivity is also described. This ellipsometric technique offers an attractive alternative to fluorescence-microarray readers in some genomic, proteomic, diagnostic, and sensing applications.

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