Experimental investigation of NIRS spatial sensitivity

Abstract

Near infrared spectroscopy (NIRS) is regarded as a potential medical diagnostic technique for investigation of hemodynamic changes. However, uncertainties pertaining to the origin of NIRS signals have hampered its clinical interpretation. The uncertainities in NIRS measurements especially in case of living tissues are due to lack of rigorous combined theoretical-experimental studies resulting in clear understanding of the origin of NIRS signals. For their reliable interpretation it is important to understand the relationship between spatial changes in optical properties and corresponding changes in the NIRS signal. We investigated spatial sensitivity of near infrared optical measurements using an experimental approach. It uses a liquid optical phantom as tissue equivalent, which is explored under robot-control by a small, approximately point like perturbation of desired optical properties, and a NIRS instrument for trans-illumination/reflection measurements. The experimentally obtained sensitivity has been analyzed and compared with numerical simulations. In preliminary experiments we investigated the influence of various optical properties of the medium and of source/detector distances on the spatial sensitivity distribution. The acquired sensitivity maps can be used to define characteristic parameters. As an example, we used a 25% threshold to define a penetration depth measure which provides values in good accordance with published ones. To the best of our knowledge this is the first experimental study of NIRS spatial sensitivity. The presented method will allow in depth experimental investigation of the influence of various conditions pertaining to medium such as optical properties of tissue (scattering and absorption) and of the source/detector configuration. 1977-1981 (1996). Zakynthinos, and I. Vogiatzis, "Near-infrared spectroscopy and indocyanine green derived blood flow index for non-invasive measurement of muscle perfusion during exercise," J. Appl. Physiol. 108(4), 962-967 (2010). 19. M. Xia, V. Kodibagkar, H. Liu, and R. P. Mason, "Tumour oxygen dynamics measured simultaneously by nearinfrared spectroscopy and 19f magnetic resonance imaging in rats," Phys. Med. Biol. 51, 45-60 (2006). 20. S. Nioka and B. Chance, "Nir spectroscopic detection of breast cancer," Technol. Cancer Res. Treat. 4, 497-512 (2005). 21. M. Firbank, M. Oda, and D. T. Delpy, "An improved design for a stable and reproducible phantom material for use in near-infrared spectroscopy and imaging," Phys. Med. Biol. 40, 955-961 (1995). 22. M. Firbank, E. Okada, and D. T. Delpy, "Investigation of the effect of discrete absorbers upon the measurement of blood volume with near-infrared spectroscopy," Phys.

Cerebral Hemodynamics and Metabolism During Cardiac Arrest and Cardiopulmonary Resuscitation Using Hyperspectral Near Infrared Spectroscopy

“…Subsequently, various hNIRS algorithms have been proposed to deconvolve Cytox redox changes based either on MBLL 28 or on DA. 11, 29 The results of the deconvolution of the Cyt-ox signal has been found to be strongly affected by the employed algorithm. 30 Therefore, although hNIRS has shown to be a promising tool for the measurement of tissue oxygenation, the possibility of crosstalk between Cyt-ox and hemoglobin changes has questioned the reliability of the Cyt-ox measurements.…”

False positives and false negatives in functional near-infrared spectroscopy: issues, challenges, and the way forward

“…16 Extracerebral confounders are an issue because the diffusely reflected light in fNIRS is attenuated by a significant degree in the extracerebral tissue layer of the head and not only in the cerebral compartment. [18][19][20][21] The penetration depth (D) of light emitted in the head tissue layers is substantially less than half the source-detector separation (SDS) as predicted by the diffusion approximation 22 (i.e., D < 0.5 SDS). Changes in hemodynamics and oxygenation in the extracerebral layer will have a strong impact on the fNIRS signals.…”

Wireless Distributed Acquisition System for Near Infrared Spectroscopy – Wda-Nirs

“…The scheme of our recently introduced experimental setup for sensitivity scanning 14 is shown in Fig. 4(a).…”

“…The concentration of Medialipide and india-ink is chosen to achieve various optical parameter values as needed for the experiments mimicking physiological conditions ( a ¼ 0:001 mm À1 and 0 s ¼ 0:8 mm À1 ). 14 To avoid any sedimentation e®ects, a magnetic stirrer is turning continuously throughout the whole experiment. The optical perturbation is realized by a liquid-¯lled glass bulb.…”

“…Validation with a sensitivity mapping phantom using a home-made liquid phantom was previously presented in Ref. 14 …”