Non-Invasive Measurement Of Tissue Chromophore Concentrations And Cerebral Blood Flow Using Broad-Band Continuous Wave Near Infrared Spectroscopy

We present a broad-band, continuous wave spectral approach to quantify the baseline optical properties of tissue, in particular the absolute absorption and scattering properties and changes in the concentrations of chromophores, which can assist to quantify the regional blood flow from dynamic contrast-enhanced near-infrared spectroscopy data. Experiments were conducted on phantoms and piglets. The baseline optical properties of tissue were determined by performing a multi-parameter wavelength-dependent differential data fit of the near infrared reflectance spectrum between 680 nm and 970 nm of a photon diffusion equation solution for a semi-infinite homogeneous medium. These baseline optical properties of the piglet head tissue were used to quantify the temporal dynamics of the concentration of the intravenously administered contrast agent Indocyanine Green in the piglet brain. The temporal traces of the Indocyanine Green concentration measured by our method were used to estimate the cerebral blood flow using a bolus tracking technique.

Non-Invasive Measurement Of Tissue Chromophore Concentrations And Cerebral Blood Flow Using Broad-Band Continuous Wave Near Infrared Spectroscopy

We present a broad-band, continuous wave spectral approach to quantify the baseline optical properties of tissue, in particular the absolute absorption and scattering properties and changes in the concentrations of chromophores, which can assist to quantify the regional blood flow from dynamic contrast-enhanced near-infrared spectroscopy data. Experiments were conducted on phantoms and piglets. The baseline optical properties of tissue were determined by performing a multi-parameter wavelength-dependent differential data fit of the near infrared reflectance spectrum between 680 nm and 970 nm of a photon diffusion equation solution for a semi-infinite homogeneous medium. These baseline optical properties of the piglet head tissue were used to quantify the temporal dynamics of the concentration of the intravenously administered contrast agent Indocyanine Green in the piglet brain. The temporal traces of the Indocyanine Green concentration measured by our method were used to estimate the cerebral blood flow using a bolus tracking technique.

Optical tomography of turbid media containing diffusive and non-diffusive inclusions: An error modeling approach

Diffuse optical techniques have been extensively employed during the last years to retrieve the optical properties of tissue with and without inclusions. The usual approach is to use the diffusion approximation to the radiative transfer equation. However, if low- or non-diffusive regions are inside the studied volume, the diffusion approximation does not hold and the radiative transfer equation needs to be solved, which is computationally much more demanding. In this contribution, the problem of determining the optical properties of the whole volume of a turbid host medium containing both diffusive and non-diffusive inhomegeneities is examined. The situation reproduces clinical cases in which tumors and cysts can be present inside a studied tissue. To achieve this, an extended Kalman filter with compensation by Bayesian error modeling approach was adopted. Applying this technique, the diffusion approximation is used for calculations, reducing computation time, and discrepancies in the non-diffusive regions are compensated by the radiative transfer equation, thus keeping accuracy over the whole volume. The proposal is validated by phantom experiments showing very good results.

Multi Simulation Platform for Time Domain Diffuse Optical Tomography: An Application to a Compact Hand-Held Reflectance Probe

Time Domain Diffuse Optical Tomography (TD-DOT) enables a full 3D reconstruction of the optical properties of tissue, and could be used for non-invasive and cost-effective in-depth body exploration (e.g., thyroid and breast imaging). Performance quantification is crucial for comparing results coming from different implementations of this technique. A general-purpose simulation platform for TD-DOT clinical systems was developed with a focus on performance assessment through meaningful figures of merit. The platform was employed for assessing the feasibility and characterizing a compact hand-held probe for breast imaging and characterization in reflectance geometry. Important parameters such as hardware gating of the detector, photon count rate and inclusion position were investigated. Results indicate a reduced error (<10%) on the absorption coefficient quantification of a simulated inclusion up to 2-cm depth if a photon count rate ≥ 106 counts per second is used along with a good localization (error < 1 mm down to 25 mm-depth).

Use of Hyperspectral/Multispectral Imaging in Gastroenterology. Shedding Some–Different–Light into the Dark

Hyperspectral/Multispectral imaging (HSI/MSI) technologies are able to sample from tens to hundreds of spectral channels within the electromagnetic spectrum, exceeding the capabilities of human vision. These spectral techniques are based on the principle that every material has a different response (reflection and absorption) to different wavelengths. Thereby, this technology facilitates the discrimination between different materials. HSI has demonstrated good discrimination capabilities for materials in fields, for instance, remote sensing, pollution monitoring, field surveillance, food quality, agriculture, astronomy, geological mapping, and currently, also in medicine. HSI technology allows tissue observation beyond the limitations of the human eye. Moreover, many researchers are using HSI as a new diagnosis tool to analyze optical properties of tissue. Recently, HSI has shown good performance in identifying human diseases in a non-invasive manner. In this paper, we show the potential use of these technologies in the medical domain, with emphasis in the current advances in gastroenterology. The main aim of this review is to provide an overview of contemporary concepts regarding HSI technology together with state-of-art systems and applications in gastroenterology. Finally, we discuss the current limitations and upcoming trends of HSI in gastroenterology.

tISM - a transportable integrating sphere setup for standardized measurements of blood and tissue phantoms

The development of an optical sensor for non-invasive measurements in humans requires a test setup, where the optical properties of tissue and blood can be adjusted and measured standardized. The goal of this work is to develop a simplified device based on an integrating sphere setup to evaluate the optical properties of tissue and blood phantoms with respect to static as well as flow conditions. Furthermore, the measurement system is intended to be used at different locations such as laboratories and operating theaters. We evaluate the absorption μa and reduced scattering μs' coefficients of specimens, with the developed integrating sphere setup. The measurement is regulated by a microcontroller for averaging and processing the data. The system is housed in a lightproof box and powered by a battery and therefore transportable. Due to this construction, no calibration is necessary between transports of the system. Calculations are executed with the inverse adding doubling algorithm. In order to basically calibrate and evaluate the setup before first transportation, a dilution series with Intralipid and India ink serve for the test. The results were consistent with precedent studies (mean absolute deviation for μs' of 0.75 mm-1) and demonstrate that this method might be able to produce liquids with adjustable optical properties, as required for further research. Furthermore, a first dilution series of heparinized heamoglobin (5 to 15 g/dl) with oxygen saturation of 98 % was measured with this system under flow conditions.We observed a linear increase of μa and μs' with the increment of the haemoglobin concentration. As light sources, laser diodes in the range from 780 to 980 nm were introduced. Static and flow measurements indicated that the system is capable for evaluating optical properties under the selected conditions.