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In this study, we investigate the role of sinoatrial node (SAN) cellular heterogeneity in normal cardiac pacemaker function. Using detailed ionic models of electrical activity in SAN and atrial myocytes, we have formulated a number of models of SAN heterogeneity based on discrete-region (in which central and peripheral SAN type cell are separated into discrete regions), gradient and mosaic models...
Because of the overwhelming scattering of light in biological tissues, the spatial resolution and imaging depth of conventional fluorescent imaging is unsatisfactory. Therefore, we present a dual modality imaging technique by combining fluorescence imaging with high-resolution noninvasive photoacoustic tomography (PAT) for the study of an animal tumor model. PAT provides high-resolution structural...
Optical methods from the near infrared range, in particular the time resolved near infrared spectroscopy offer a new non-invasive, real-time technique for monitoring of the blood perfusion and oxygenation in living tissue. The principle and instrumentation of the time resolved optical spectroscopy system for cerebral oxygenation imaging have been described. The system consists of two semiconductor...
We developed a method for testing guide wires and catheters that realistically evaluates the forces applied to anatomical structures by these instruments during urological procedures. The placement of guide wires and catheters to gain access to the upper urinary tract can induce undesirable stresses on the tissues. Previous studies have characterized wire/catheter performances base on their physical...
High-dimensional deformable registration of MRI brain images is presented here. The deformation is driven by local forces estimated from point similarities based on joint histogram and with the use of prior information obtained from tissue probability maps available in selected commonly used brain atlases. Three point similarity measures are tested in an experiment with data obtained from standard...
This paper describes an approach to fine scale non-rigid registration for mapping patterns of tissue volume loss in serial MRI studies of the brain. Specifically it addresses the important confound of diffuse tissue contrast changes which can influence local sub-voxel estimates of volume change. Such changes can be induced by neurodegenerative or neurodevelopmental processes, which not only modify...
Micro/nano-particle drug delivery systems are being developed for improving therapeutic effects. However, most studies can only evaluate the delivery properties by indirectly measuring the pharmacokinetic changes of the drugs. It had been difficult to directly assay the drug carrier status and distribution in vivo. We described here a method using intravital microscopy to visualize individual drug...
Cerebral oxygenation especially regional cerebral oxygen saturation (rSO2) needs to be monitored to avoid irreversible damages induced by hypoxia. Based on steady-state spatially resolved spectroscopy (SRS), rSO2 was obtained by the NIRS oximeter developed by our group. The oximeter was calibrated by blood gas analyzer using the liquid tissue model made up by our group. The results indicate that the...
The effectiveness of reperfusion therapies during acute brain ischemia depends on the viability of the underperfused tissue. Specifically, when the ischemia tissue is viable reperfusion leads to improved clinical outcome. However, when the ischemic tissue is non-viable, reperfusion therapy can lead to intra-cerebral hemorrhage and/or an accelerated rate of ischemia formation. Perfusion and diffusion...
We investigate a new model for the cardiac system. It embodies the main features of cardiac activity with great flexibility. It can be tuned to suit different cell types, and scaled up or down to represent either a single cell, an aggregate, or whole tissue. We demonstrate its use in the generation of a clinically realistic electrocardiogram (ECG) and other dynamical behaviours such as spiral waves...
Most technologies for tissue elasticity imaging are now based on measurement of stain distribution, since they are more suited to real-time processing than reconstruction of elastic modulus images. However, to obtain more quantitative information about tissue elastic properties, it is necessary to reconstruct tissue elastic modulus images. There, we developed a new method for reconstructing tissue...
As a differential diagnosis technique of living soft tissues, we are developing ultrasonic strain measurement-based shear modulus reconstruction methods. Previously, we reported a method utilizing the typical value of Poisson's ratio. However, as reconstruction errors were confirmed due to the difference between the original value and the set value, we proposed a method to reconstruct Poisson's ratio...
Tissue stiffness is generally known to be associated with pathologic changes. Ultrasound indentation is able to assess the mechanical properties of soft tissues. Conventional ultrasound indentation devices use rigid flat-ended transducers to directly contact with the tissues and typically operate in the frequency ranging between 2 M Hz and 10 MHz. This paper introduced a novel ultrasound indentation...
We have proposed a highly responsive system for the on-line in vitro assessment of tissue growth within microporous polymer scaffolds that obviates any compromise of sample integrity. The system's function is based on the sample's loss factor: the imaginary part of the complex permittivity. Reflection measurements were performed using an open-ended coaxial probe and impedance analyzer; they were then...
We constructed an impedance spectroscopy measurement system based on frequency response analyzer. Using four-terminal method, we measured impedance spectroscopy of rabbit different tissues in vitro within 5 to 360 minutes after excision at the frequency range from 1Hz to 1MHz. According to the measurement results, we analyzed the changes of characteristic parameters (Ro, Rinfin, fc and alpha) of different...
The terahertz pulse (THz pulse) propagation in biological tissue is simulated by Monte Carlo method (MCM). The migratory route of THz pulse in the tissue is presented. The computation model is based on the assumption that the refraction indexes of tissue and air are mismatch and both surfaces of the tissue have the reflection effect for THz pulse
This study assessed the feasibility of neonatal cerebral oxygen monitoring by near-infrared light spectroscopy (NIRS) using a light emitting diode (LED) based system. We aimed to measure the changes in cerebral oxygen saturation, as regional oxygen saturation and tissue oxygenation index, in response to auditory stimuli. Documenting changes in oxygenation in response to such stimuli will help validate...
The surface backscattered radiations of curved tissue-equivalent phantom are measured using miniature multi-probe laser reflectometer imaging system. Phantom models are prepared using paraffin wax mixed with wax colors and their optical parameters are determined by comparing measured backscattered profile with that of Monte Carlo simulation procedure. Abnormalities with optical parameters 5% less...
To establish a high precision data acquisition system for multi-frequency electrical impedance tomography (EIT), a series of methods were introduced. Those methods include building a driving signal with up to four frequency components to diminish the effect of the dynamic change of tissues resistivity, extracting the impedance information by a digital demodulator that can improve the SNR by 8 times...
A study of microwave-induced thermoacoustic tomography is presented in this paper. Microwaves illuminate biological tissues to generate acoustic waves by thermoelastic expansion when electromagnetic energy was absorbed by human tissues. The generated acoustic waves carry information about different electromagnetic properties of different tissues which will be collected and processed to reconstruct...
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