X‐ray imaging in advanced studies of ophthalmic diseases

Abstract

Microscopic characterization of pathological tissues has one major intrinsic limitation, the small sampling areas with respect to the extension of the tissues. Mapping possible changes on vast tissues and correlating them with large ensembles of clinical cases is not a feasible procedure for studying most diseases, as for instance vision loss related diseases and, in particular, the cataract. Although intraocular lens implants are successful treatments, cataract still is a leading public-health issue that grows in importance as the population increases and life expectancy is extended worldwide. In this work we have exploited the radiation-tissue interaction properties of hard x-rays--very low absorption and scattering--to map distinct lesions on entire eye lenses. At the used synchrotron x-ray photon energy of 20 keV (wavelength lambda=0.062 nm), scattering and refraction are angular resolved effects. It allows the employed x-ray image technique to efficiently characterize two types of lesions in eye lenses under cataractogenesis: distributions of tiny scattering centers and extended areas of fiber cell compaction. The data collection procedure is relatively fast; allowing dozens of samples to be totally imaged (scattering, refraction, and mass absorption images) in a single day of synchrotron beam time. More than 60 cases of canine cataract, not correlated to specific causes, were investigated in this first application of x-rays to image entire lenses. Cortical opacity cases, or partial opacity, could be related to the presence of calcificated tissues at the cortical areas, clearly visible in the images, whose elemental contents were verified by micro x-ray fluorescence as very rich in calcium. Calcificated tissues were also observed at nuclear areas in some cases of hypermature cataract. Total opacity cases without distinguishable amount of scattering centers consist in 70% of the analyzed cases, where remarkable fissure marks owing to extended areas of fiber cell compaction are diagnosed.

Computer Simulation Tools for X-ray Analysis

“…On the other hand, X-ray imaging of soft tissues exploit either the tiny deflection or phase shift of the X-ray wave when crossing the interface of two medium with difference in electron density. In quantitative values, this deflection is about 1 rad for X-rays of 20 keV and density variations of 10 % with respect to the water density (Antunes et al 2006). Exercise 6.4.…”

Multiple imaging radiography at LNLS

“…The ABI proved to be useful to identify different structures in healthy and diseased (with cataract) crystalline lenses [30,31]. Also, microcalcifications were found in experiments developed with higher energies [32].…”

“…Ophthalmologic diseases have been studied by using, among other techniques, the ABI [30][31][32]. The ABI proved to be useful to identify different structures in healthy and diseased (with cataract) crystalline lenses [30,31].…”

Caracterização morfológica de tecidos oculares por microscopia de força atômica (MFA)

“…Presença de cálcio (setas brancas) na região cortical são presentes na maioria dos casos de catarata parcial, enquanto que fissuras radiais (setas pretas) devido à compactação de fibras celulares são observadas nos casos de catarata total independentemente da ocorrência da presença de cálcio. Veja referência [34] para maiores detalhes.…”