scholarly journals G110 In Vivo Measurement of Thermal Conductivity and Thermal Diffusivity of Biological Tissues

2001 ◽  
Vol 2001 (0) ◽  
pp. 281-282
Author(s):  
Xing ZHANG ◽  
Ryousuke TOBETA ◽  
Motoo FUJII ◽  
Horoshi TAKAMATSU
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Biological Tissues ◽  
In Vivo Measurement

scholarly journals Machine learning estimation of tissue optical properties

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brett H. Hokr ◽  
Joel N. Bixler
Keyword(s):  
Neural Network ◽  
Optical Properties ◽  
Biological Tissues ◽  
Homogeneous Layer ◽  
In Vivo Measurement ◽  
Tissue Optical Properties ◽  
The Neural Network ◽  
Spatio Temporal ◽  
Fully Connected

AbstractDynamic, in vivo measurement of the optical properties of biological tissues is still an elusive and critically important problem. Here we develop a technique for inverting a Monte Carlo simulation to extract tissue optical properties from the statistical moments of the spatio-temporal response of the tissue by training a 5-layer fully connected neural network. We demonstrate the accuracy of the method across a very wide parameter space on a single homogeneous layer tissue model and demonstrate that the method is insensitive to parameter selection of the neural network model itself. Finally, we propose an experimental setup capable of measuring the required information in real time in an in vivo environment and demonstrate proof-of-concept level experimental results.

scholarly journals A THREE-PHASE INDUCTIVE SENSOR FOR IN VIVO MEASUREMENT OF ELECTRICAL ANISOTROPY OF BIOLOGICAL TISSUES

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Yukio Kosugi ◽  
Tadashi Takemae ◽  
Hiroki Takeshima ◽  
Atsushi Kudo ◽  
Kazuyuki Kojima ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
High Frequency ◽  
Reference Signal ◽  
Biological Tissues ◽  
Electrical Anisotropy ◽  
Conductivity Anisotropy ◽  
In Vivo Measurement ◽  
Surgical Operations

Biological tissue will have anisotropy in electrical conductivity, due to the orientation of muscular fibers or neural axons as well as the distribution of large size blood vessels. Thus, the in vivo measurement of electrical conductivity anisotropy can be used to detect deep-seated vessels in large organs such as the liver during surgeries. For diagnostic applications, decrease of anisotropy may indicate the existence of cancer in anisotropic tissues such as the white matter of the brain or the mammary gland in the breast. In this paper, we will introduce a new tri-phase induction method to drive rotating high-frequency electrical current in the tissue for the measurement of electrical conductivity anisotropy. In the measurement, three electromagnets are symmetrically placed on the tissue surface and driven by high-frequency alternative currents of 0 kHz, modulated with 1 kHz 3-phase signals. In the center area of three magnets, magnetic fields are superimposed to produce a rotating induction current. This current produces electrical potentials among circularly arranged electrodes to be used to find the conductivity in each direction determined by the electrode pairs. To find the horizontal and vertical signal components, the measured potentials are amplified by a 2ch lock-in amplifier phase-locked with the 1 kHz reference signal. The superimposed current in the tissue was typically 45 micro Amperes when we applied 150 micro Tesla of magnetic field. We showed the validity of our method by conducting in vitro measurements with respect to artificially formed anisotropic materials and preliminary in vivo measurements on the pig’s liver. Compared to diffusion tensor MRI method, our anisotropy sensor is compact and advantageous for use during surgical operations because our method does not require strong magnetic field that may disturb ongoing surgical operations.

Measurement of the Optical Properties of Muscle Tissue In Vivo

2000 ◽  
Author(s):  
P. L. Kopsombut ◽  
D. Willis ◽  
A. E. Schen ◽  
L. X. Xu ◽  
X. Xu
Keyword(s):  
Optical Properties ◽  
Transport Theory ◽  
Rapid Development ◽  
Ccd Camera ◽  
High Sensitivity ◽  
Biological Tissues ◽  
In Vivo Measurement ◽  
Living Tissues

Abstract Along with rapid development of diagnostic and therapeutic applications of lasers in medicine, optical properties of various biological tissues have been extensively studied [1]. Most of the studies were performed in vitro owing to the complexity involved in in vivo measurement. To date, it is well understood that living tissue is an absorbing and scattering heterogeneous medium because of its complex structures including blood network. The transport theory cannot be readily used due to the heterogeneity and the absence of the optical properties of living tissues [2]. In this research, we have developed a procedure for measuring the total attenuation coefficient (μ1) of the exteriorized rat 2-D spinotrapezius muscle in the wavelength ranged from 480–560 nm using the collimated light from a Nitrogen-pumped dye laser and a high-sensitivity CCD camera.

The Simultaneous Measurement of Thermal Conductivity, Thermal Diffusivity, and Perfusion in Small Volumes of Tissue

1984 ◽  
Vol 106 (3) ◽  
pp. 192-197 ◽  
Author(s):  
J. W. Valvano ◽  
J. T. Allen ◽  
H. F. Bowman
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Tissue Perfusion ◽  
Effective Thermal Diffusivity ◽  
Liver Preparation ◽  
Improved Technique ◽  
Power Response

An improved technique is presented for the “in-vivo” determination of thermal conductivity, thermal diffusivity, and perfusion using a self-heated spherical thermistor probe. In the presence of flow, solution of the time-dependent, probe-tissue coupled thermal model allows the measurement of “effective” thermal conductivity and “effective” thermal diffusivity, which represent the thermal properties of the perfused tissue. Perfusion can be quantified from both “effective” thermal properties. In the presence of flow, it has been shown that the transient power response does not follow t−1/2 as has been previously assumed. An isolated rat liver preparation has been developed to validate the measurement technique. Radioactive microspheres are used to determine the true perfusion from the total collected hepatic vein flow. Experimental data demonstrates the ability to quantify perfusion in small volumes of tissue.

scholarly journals Comparative analysis of indentation and magnetic resonance elastography for measuring viscoelastic properties

2021 ◽  
Author(s):  
Yu Chen ◽  
Suhao Qiu ◽  
Zhao He ◽  
Fuhua Yan ◽  
Ruokun Li ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Viscoelastic Properties ◽  
Soft Tissues ◽  
Biological Tissues ◽  
Magnetic Resonance Elastography ◽  
Small Samples ◽  
Model Parameters ◽  
In Vivo Measurement ◽  
Pathological Behavior

Abstract Measurement the viscoelastic properties is important for studying the developmental and pathological behavior of soft biological tissues. Magnetic resonance elastography (MRE) is a non-invasive method for in vivo measurement of tissue viscoelasticity. As a flexible method capable of testing small samples, indentation has been widely used for characterizing soft tissues. Using 2nd-order Prony series and dimensional analysis, we analyzed and compared the model parameters estimated from both indentation and MRE. Conversions of the model parameters estimated from the two methods were established. We found that the indention test is better at capturing the dynamic response of tissues at a frequency less than 10 Hz, while MRE is better for describing the frequency responses at a relatively higher range. The results provided helpful information for testing soft tissues using indentation and MRE. The models analyzed are also helpful for quantifying the frequency response of viscoelastic tissues. Graphic Abstract

Thermal Conductivity and Thermal Diffusivity of Biomaterials: A Simultaneous Measurement Technique

1977 ◽  
Vol 99 (3) ◽  
pp. 148-154 ◽  
Author(s):  
T. A. Balasubramaniam ◽  
H. F. Bowman
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Measurement Technique ◽  
Thermal Model ◽  
In Vitro Measurements ◽  
Made In

A technique is presented for the simultaneous determination of thermal conductivity and thermal diffusivity of biomaterials. Measurements are derived from the transient power supplied to a thermistor probe operated in a self-heated mode. The thermal properties are extracted through the use of an appropriate thermal model. Thermal conductivity is determined through a simple algebraic equation. Thermal diffusivity is determined from a convenient set of nondimensionalized curves. The technique can be used in vivo and in vitro. Measurements can be made in sample volumes of less than 1 cc in less than 30 s.

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