In Vivo, Non-Invasive Characterization of Human Bone by Hybrid Broadband (600-1200 nm) Diffuse Optical and Correlation Spectroscopies

Abstract

Non-invasive in vivo diffuse optical characterization of human bone opens a new possibility of diagnosing bone related pathologies. We present an in vivo characterization performed on seventeen healthy subjects at six different superficial bone locations: radius distal, radius proximal, ulna distal, ulna proximal, trochanter and calcaneus. A tailored diffuse optical protocol for high penetration depth combined with the rather superficial nature of considered tissues ensured the effective probing of the bone tissue. Measurements were performed using a broadband system for Time-Resolved Diffuse Optical Spectroscopy (TRS) to assess mean absorption and reduced scattering spectra in the 600–1200 nm range and Diffuse Correlation Spectroscopy (DCS) to monitor microvascular blood flow. Significant variations among tissue constituents were found between different locations; with radius distal rich of collagen, suggesting it as a prominent location for bone related measurements, and calcaneus bone having highest blood flow among the body locations being considered. By using TRS and DCS together, we are able to probe the perfusion and oxygen consumption of the tissue without any contrast agents. Therefore, we predict that these methods will be able to evaluate the impairment of the oxygen metabolism of the bone at the point-of-care.

Near infrared spectroscopy for measuring changes in bone hemoglobin content after exercise in individuals with spinal cord injury

“…This study extends previous work that demonstrated the potential of NIRS measurements of blood in tibial cortical bone using cuff inflation in a single subject 22 and in different superficial bones using a single-layer system 25 . In this work we demonstrate that NIRS is able to measure significant physiological changes in blood perfusion during exercise in a cohort of able-bodied individuals.…”

“…Aziz et al 22 presented hemoglobin content in tibia cortical bone in a single individual during cuff inflation using a NIRS instruments developed specifically for bone. Sekar et al 25 used time-resolved diffuse optical spectroscopy to probe bone oxygen consumption and blood flow in different superficial bones in able-bodied individuals. These promising results indicate the potential of optical techniques in investigating blood content in bone.…”

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

“…Automatic wavelength selection of the supercontinuum source (SC450, Fianium, UK) was achieved by dispersing the light using a rotating prism and selecting a narrow band with a slit. The system was mounted on a cart and permitted non-invasive clinical studies on the application of broadband diffuse optics to bone tissues [29] and thyroid [68]. The introduction of compact commercial supercontinuum sources based on fiber amplified lasers coupled to photonic crystal fibers [62][63][64] and of rugged silicon photomultipliers [65] usable in diffuse optics [43,66] made it possible to realize movable rack-based systems suitable for use in clinical settings, as shown in Figure 6 [23,67].…”

“…In vivo applications of diffuse optics are mostly explored in the therapeutic window (600-1100 nm), where light attenuation in human tissues is comparatively low [25][26][27][28]. Furthermore, quantification of tissue constituents (chromophores) can be performed through the Beer-Lambert law, by a linear fit of typical tissue constituent absorption spectra with the broadband absorption spectrum of in vivo tissue [29,30]. Information on the microscopic structure, useful for tissue characterization, can also be derived from the scattering properties.…”

“…On the in vivo side, broadband TD-DOS is aptly placed to explore non-invasively new tissue locations and provide new insights on human physiological and pathological pathways. In this direction, various explorations have been conducted to characterize organs like breast, bone, thyroid, manubrium, forehead, brain, and others [13,23,26,29,52,53].…”