Broadband (550–1350 nm) diffuse optical characterization of thyroid chromophores

Abstract

Thyroid plays an important role in the endocrine system of the human body. Its characterization by diffuse optics can open new path ways in the non-invasive diagnosis of thyroid pathologies. Yet, the absorption spectra of tyrosine and thyroglobulin–key tissue constituents specific to the thyroid organ–in the visible to near infrared range are not fully available. Here, we present the optical characterization of tyrosine (powder), thyroglobulin (granular form) and iodine (aqueous solution) using a time domain broadband diffuse optical spectrometer in the 550–1350 nm range. Various systematic errors caused by physics of photo migration and sample inherent properties were effectively suppressed by means of advanced time domain diffuse optical methods. A brief comparison with various other known tissue constituents is presented, which reveals key spectral regions for the quantification of the thyroid absorbers in an in vivo scenario.

Solid phantom recipe for diffuse optics in biophotonics applications: a step towards anatomically correct 3D tissue phantoms

“…Subsequent measurements were performed in transmittance geometry. Therefore, the phantoms were made with large diameter (10 cm) to avoid boundary effects and granting use of a slab model [22]. The thickness of the phantoms was 18 mm.…”

Broadband Time Domain Diffuse Optical Reflectance Spectroscopy: A Review of Systems, Methods, and Applications

“…Absorption spectra of various absorbers are essential for the quantitative analysis of highly scattering media. In tissue optics, the characterization of highly scattering tissue constituents like collagen, elastin, lipid, thyroglobulin using traditional spectrophotometers pose several challenges [119]. An integration sphere could uncouple the effects of scattering, but falls short to address uncoupling from other effects like fluorescence, finite boundary effects, physical structure of tissue constituents, and so on.…”

“…TD-DOS can be used to characterize highly scattering absorbers [120,121]. By careful design of the measurement protocol, TD-DOS can effectively address the above-mentioned challenges to extract the absolute absorption spectra of various absorbers [119]. Collagen is a structural protein and an abundant tissue constituent present in various soft and hard tissues.…”

“…This led to the hypothesis of missing constituents that are unique to thyroid tissue. Figure 12 shows the characterization of thyroid-specific tissue constituents: thyroglobulin, tyrosine, and iodine [119]. Thyroglobulin, the most abundant protein in thyroid tissue, has a monotonous decreasing absorption spectrum with a shoulder and a peak, respectively, at 1000 and 1190 nm.…”

“…Absorption (black line) and reduced scattering (red line) spectra of thyroid tissue chromophores: (a) thyroglobulin, (b) tyrosine, (c) iodine, with inset depicting the anatomy of thyroid[119].…”