Optical biopsy of bone tissue: a step toward the diagnosis of bone pathologies

Abstract

In vivo absorption and reduced scattering spectra of the human calcaneous from 650 to 1000 nm were assessed using a laboratory system for time-resolved transmittance spectroscopy. Measurements were performed on the calcaneous of seven female volunteers ranging from 26 to 82 years of age. The analysis of the absorption spectra, using a linear combination of the key tissue absorbers (bone mineral, water, lipids, oxy- and deoxyhemoglobin), revealed a general decrease in bone mineral content and an increase in lipids with age, which is in agreement with the aging transformations that occur in bone tissues. The scattering spectra were less effective in detecting such changes in older subjects, showing only a minor decrease in the coefficient for these subjects. The capability to noninvasively quantify bone tissue composition suggests a possible use of optical biopsy for the diagnosis of bone pathologies such as osteoporosis, which are characterized by a progressive reduction and transformation of the mineral in the bone matrix.

Time-resolved diffused optical characterization of key tissue constituents of human bony prominence locations

“…In reference to the problem of osteoporosis, interesting results were reported by light scattering techniques showing correlation between osteoporosis and bone scattering coefficient 8 . Preliminary in vivo optical measurements on 5 volunteers done on calcaneous bone 9 showed interesting correlation between age, various tissue constituents (lipid, collagen, hemoglobin) and the scattering coefficient using a time-resolved broadband laboratory-based system 10 Bone fibrous tissue structure consists of connective tissue, proteins (mostly collagen) and blood cells as major components. The concentration of collagen and other tissue constituents could be related to bone physiological condition and to alterations induced by pathologic conditions.…”

Techniques used for Bone Density Measurement

“…The range around 750nm is absorbed mostly because of water, lipids and deoxyhemoglobin. [4] It was observed that with the increase in calcium density the output voltage increases.…”

“…In clinical practice, bone mineral density is usually expressed as a T score (number of standard deviations from the young normal mean) or Z score. [4] Negative value means the person suffers from the dieses while the positive values indicates no risk of fracture. Generally the value is between -3 to 3.…”

Optical Clearing of Cranial Bone

“…The inorganic matrix contains calcium hydroxyapatite, which is responsible for the compressive strength of bone, and osteocalcium phosphate. The main components of the organic matrix are collagen, proteins, blood cells, and lipids [23]. The amount of bone mineral matrix is 16%, the lipid content is 54%, the proteins content is 16%, and water contributes 16% [23].…”