Ding Haishu

Influence of overlying tissue and probe geometry on the sensitivity of a near-infrared tissue oximeter

In this paper, the influences of overlying tissue and detecting distance between the source and the detector on the measurement of a tissue oximeter were discussed. The signal-noise-ratio of the detector was also examined. A semi-infinite multi-layer Monte Carlo model was induced to simulate the migration of the photons in the skin, adipose and muscle. The thickness of the adipose layer and the separation between the source and the detector in the muscle were changed to simulate the clinical application. Partial pathlength was introduced as a characteristic parameter to evaluate the sensitivity of the oximeter. A two-wavelength (700 and 830 nm) tissue oximeter was developed to verify the results of the simulation. The Monte Carlo simulation results showed that the sensitivity of the near infrared spectroscopy (NIRS) oximeter declined greatly with increasing overlying tissue thickness. Increasing the distance between the light source and the detector improved the sensitivity. However, in order to achieve a sufficiently high signal-to-noise ratio, it was necessary to limit this distance. The results of a bicycle ergometer exercise verified the above results and showed that, for a special adipose thickness (AT), there may be a reasonable range of the emitter-detector separation.

Relationship between surface temperature distribution and internal heat source size of the in-vitro tissue

ln this paper, the relationship between surface temperature distribution and internal heat source size of the in-vitro tissue was discussed. The method of obtaining internal heat source information from surface temperature distribution will promote the application of thermography. Through approximation, the relationship between surface temperature distribution and internal beat source size of the in-vitro tissue was induced. The reasonability of the approximation was validated by the high match degree between the template generated by the approximation solution and the practical surface temperature distribution.

CCD-based system for three-dimensional real-time positioning

Based upon the direct position detection approach and pixel analysis technique, a CCD-based system has been developed for three-dimensional real-time positioning. A data sampling interface card has been designed to gather the 2D coordinates of the LED markers. The spatial positions of moving multiple spots can be obtained instantly. A calibration frame has been constructed to acquire the system parameters before detection. A modified DLT (Direct Linear Transformation) algorithm is presented to correct the nonlinear lens distortion using a planar spot-grid. The precision of the system is less than /spl plusmn/1 mm in a 500 mm/spl times/500 mm/spl times/500 mm space. This corresponds to a spatial resolution of about one part in 500 or 0.2% overall accuracy. This system has been applied in evaluating the therapeutic effect of Lumbar Spine Function in manipulative orthopedics. Some discussions about how to acquire more accurate results by modifying the system and the algorithm are also presented.

Monitoring Cerebral Oxygen Saturation Using Near Infrared Spectroscopy during Cardiopulmonary Bypass: Comparing with Monitoring Mixed Venous Oxygen Saturation

Cerebral oxygenation can be monitored non-invasively by near infrared spectroscopy (NIRS), which is significantly important for clinical cerebral protection against hypoxia. Our group developed an NIRS oximeter, by which regional cerebral oxygen saturation (rSO2) can be monitored non-invasively, continuously and in real time. Using it, we monitored cerebral rSO2 of three children during cardiac surgery all with cardiopulmonary bypass (CPB). The mixed venous oxygen saturation of the vena cava (SvO2) at the entrance of the artificial CPB pump was also measured at the same time by another monitor. The results indicated that there was statistical correlation between cerebral rSO2 and mixed SvO2 (R=0.547, 0.465 and 0.695 respectively, and p all less than 0.01). But all the above R was not high, because cerebral rSO2 was mainly reflected by cerebral venous oxygen saturation, which was generally not consistent with the SvO2. During CPB, when the perfusion rate or the body temperature was changed, the changes of the mixed SvO2 were delayed for several minutes compared with the corresponding changes of cerebral rSO2. This was because cerebral venous blood flew relatively low, and it might take a period that the venous blood flew from the brain into the vena cava. Therefore, the mixed SvO2 cannot trace the changes of cerebral oxygenation in real time during CPB, and monitoring cerebral rSO2 using NIRS is of greatly advantages than the mixed SvO2.

Charge couple device-based system for 3-dimensional real time positioning on the assessment of segmental range of motion of lumbar spine.

Objective: To observe the tested results of the segmental range of motion (ROM) of lumbar spine by charge couple device (CCD)-based system for 3-dimensional real-time positioning (CCD system), and to analyze its clinical significance.Methods: Seven patients with lumbar joint dysfunction and 8 healthy subjects were tested twice by the CCD-based system with an interval of 10 min.Results: The ROM of the patients was obviously lesser than that of the healthy subjects. The measuring data of segmental ROM of lumbar spine by CCD system is correlated significantly to the same data checked later on the same subjects in every direction of the movements. The differences between two checks are usually less than 1 degree.Conclusion: Specially designed CCD based system for 3-dimensional real-time positioning could objectively reflect the segmental ROM of lumbar spine. The system would be of great clinical significance in the assessment of the biomechanical dysfunction of lumbar spine and the effect of the treatment applied.

Simulation and experiment on biological tissue for near infra-red (NIR) photon migration in a multi-layered model

To study the phenomenon of infrared photon migration in a multi-layered tissue is very useful in biomedical applications such as noninvasive optical monitoring of physiological parameters and the optimal dosimetry of photodynamic therapy. Multi-layered models for the research of NIR light propagation in biological tissue are established using Monte-Carlo simulation. Photon tracking and parameter correcting methods across the boundary of tissue layers with mismatched optical properties are provided. Experimental results on animal tissue are presented, and a close relationship has been found between the actual measurement and the simulation.

A method for improving the measurement data resolution of time-resolved spectroscopy (TRS) using adaptive pulse compression filter

Temporal and image resolution are the key problems in retrieving optical properties and in imaging of structural or functional changes within tissue from a set of received signals using a time-resolved spectroscopy (TRS) system. An adaptive light pulse compression filter applied to the signal processing of a TRS system is introduced, which was based on the analysis of temporal characteristics of near infrared spectroscopy (NIRS) signal. Moreover, an improved LMS algorithm having fast tracking ability and permitting large dynamic range input is also presented in this paper. The results of computer simulation, show that the filter has good tracing compression performance for diffusely reflected or transmitted signal received from the surface of the tissue and the temporal or image resolution of TRS system can be improved significantly.