To study the risk of retinal thermal injury from 532 nm laser during photodynamic therapy (PDT) for choroidal
neovascularization (CNV) by measuring the retinal temperature increase of rabbit eyes. A microthermocouple technique
was developed to measure retinal temperature increase during PDT in pigmented and non-pigmented rabbit eyes. The
532 nm laser exposures were performed with 100-s duration, 2-mm spot size, and retinal irradiance ranging from 400 to
1600 mW/cm2. A K-type microthermocouple was inserted through the sclerotomy and advanced until the tip reached the
retina at the posterior pole. The thermocouple was connected a computer that recorded and analyzed retinal temperature
data. The results showed that the retinal temperature increase during laser exposure was proportional to retinal irradiance
with a particular spot diameter, exposure duration, wavelength, and fundus pigmentation. And the measured retinal
temperature increases in pigmented rabbits were a little higher than those in albino rabbits under the same radiant
condition. Retinal threshold irradiance required for visible lesions at laser wavelength of 532 nm with 2.0-mm spot size
and 100-s duration was 1657 mW/cm2 in albino and 1003 mW/cm2 in pigmented rabbits, respectively, corresponding to
retinal temperature increase of about 8 °C and 6 °C. The measured temperatures in albino and pigmented rabbit eyes
were both lower than the model predictions, especially in pigmented rabbits. Therefore, further parameter modifying
should be performed to obtain accuracy prediction of retinal temperature.
In the research of non-invasive concentration blood measurement, the scattering behavior of the tissue may leads to
significant differences in the ideal Lambert Beer's law. In this paper, Monte Carlo method is used to analyses the blood
tissue's influence to the Dynamic Spectrum proposed by Professor LI Gang. The Dynamic Spectrum evaluating only the
pulsatile part of the entire optical signal, this approach is rather independent of individual or time changes in scattering
or absorption characteristics of the tissue. In this paper, Monte Carlo method is used to analyses the scattering
behavior of the blood, the influence of the scattering behavior of the skin tissue to the scattering behavior of the blood.
and their influence to the Dynamic Spectrum. The pulsatile part ofthe spectrum was modeled by performing simulations
of photon migration through the tissue for the diastolic and systolic states. With the simulation of the Monte Carlo
method. the diffuse reflectance and transmittance of the model was calculated, analyzed and compared. The scattering
behavior must be considered in the measurement of Dynamic Spectrum to get the high precision measurement. The error
caused by the transmittance is greater than the error caused by the diffuse reflectance. The thickness of the Epidermis
can influence the nonlinearity of the transmittance, and influence the value of the diffuse reflectance. The thickness of
the tissue can influence the scattering behavior of the tissue.
During numerical simulation of laser and tissue thermal interaction, the light fluence rate distribution should be
formularized and constituted to the source term in the heat transfer equation. Usually the solution of light irradiative
transport equation is given in extreme conditions such as full absorption (Lambert-Beer Law), full scattering
(Lubelka-Munk theory), most scattering (Diffusion Approximation) et al. But in specific conditions, these solutions will
induce different errors. The usually used Monte Carlo simulation (MCS) is more universal and exact but has difficulty to
deal with dynamic parameter and fast simulation. Its area partition pattern has limits when applying FEM (finite element
method) to solve the bio-heat transfer partial differential coefficient equation. Laser heat source plots of above methods
showed much difference with MCS. In order to solve this problem, through analyzing different optical actions such as
reflection, scattering and absorption on the laser induced heat generation in bio-tissue, a new attempt was made out which
combined the modified beam broaden model and the diffusion approximation model. First the scattering coefficient was
replaced by reduced scattering coefficient in the beam broaden model, which is more reasonable when scattering was
treated as anisotropic scattering. Secondly the attenuation coefficient was replaced by effective attenuation coefficient in
scattering dominating turbid bio-tissue. The computation results of the modified method were compared with Monte Carlo
simulation and showed the model provided reasonable predictions of heat source term distribution than past methods.
Such a research is useful for explaining the physical characteristics of heat source in the heat transfer equation,
establishing effective photo-thermal model, and providing theory contrast for related laser medicine experiments.
In this paper, some key techniques on development of on-line MR urine analyzing system based on AOTF (Acousto -
Optics Tunable Filter) are introduced. Problems about designing the optical system including collimation of incident light
and working distance (the shortest distance for separating incident light and diffracted light) are analyzed and researched.
DDS (Direct Digital Synthesizer) controlled by microprocessor is used to realize the wavelength scan. The experiment
results show that this MR urine analyzing system based on. AOTF has 10000 - 4000cm-1 wavelength range and O.3ms
wavelength transfer rate. Compare with the conventional Fourier Transform NIP. spectrophotometer for analyzing
multi-components in urine, this system features low cost, small volume and on-line measurement function. Unscrambler
software (multivariate statistical software by CAMO Inc. Norway) is selected as the software for processing the data.
This system can realize on line quantitative analysis of protein, urea and creatinine in urine.
In order to reduce the interference of the individual discrepancy in the noninvasive measurement of blood composition, a
new MR spectroscopy- dynamic spectroscopy is put forward and a new near infrared spectrometer is developed for the
dynamic spectroscopy. Experiments indicated that the dynamic spectroscopy can reduce the interference of individual
Temperature is an intuitionistic indicator of laser and tissue thermal interaction. It can be used as verification of theory prediction as well as online clinic indicator. Temperature measuring is an indispensable tool in laser and tissue photo-thermal theory research. A computer-assistant noninvasive or minimally invasive temperature measuring system, which can be used in laser medicine, was introduced. Combined infrared radiation thermometer and miniature thermocouple, the surface irradiating point and inner temperature can be monitored synchronously. This system has some necessary advantages for in vivo tissue temperature measuring. The infrared radiation thermometer temperature range is 0~200°C and 1mV/°C analog voltage output signal can be tntered to computer. Inside LED red light and aiming sound can assure the distance between thermometer and measuring point to be the focus distance of 25mm and measuring circle has the least diameter of 2.5mm. The mini K-thermocouples were made by ourselves, their temperature range is 25~500°C, the diameter of 0.4mm, and the response time is rapid up to 0.1s. They are convenient for precision orientation in the organisms. Multichannel temperature measuring can reduce the measurement error and be able for distribution measuring. Integrated temperature sensor LM35 and numerical computation is used to compensate the cold port temperature of the thermocouples. The numerical computation can also revise the nonlinearity error with the least squares method quintic polynomial fitting, which excels to the circuit method. Calibration results with glycerin and mercury thermometer showed the absolute error value is less than 0.45°C within 26-98°C. The real time temperatures of murine skin tissue irradiated by CO2 and Nd:YAG laser were measured. Such a system is suitable to high precision, large range, minute point, rapid response and real time tissue temperature measuring in laser applications. The saved data can be used for later analysis and compared with the thermal transferring theory model and calculation.
Near-IR spectroscopy holds great promise for non-invasive concentration measurements of blood on the basis of its potential for reagent-less, nondestructive, and noninvasive measurements. The main difficulty for determining absolute or even exact relative concentrations is the scattering behavior of the tissue. This leads to significant differences in the ideal Lambert Beer's law. In this paper, the approach of the Dynamic Spectrum in the frequency domain was proposed by Professor LI Gang etc. is shown, it is based on Photo-plethysmography (PPG) with fast Fourier transforms. The magnitude of fundamental wave of the pulse wave at each wavelength divided by the peak value of the pulse wave, get the natural logarithm of quotient at each wavelength and then the Dynamic Spectrum in the frequency domain is got. Evaluating only the pulsatile part of the entire optical signal, this approach is rather independent of individual or time changes in scattering or absorption characteristics of the tissue. Because of the noise and the resolution of the spectrometer, the Dynamic Spectrum is very difficult to get. In this paper, a series of measures is taken, and high-precision Dynamic Spectrum in the frequency domain is got with the experiment. The approach is verified. The advantage of getting Dynamic Spectrum in the frequency domain is analyzed, and compared with the Dynamic Spectrum in the time domain. The paper shows that the technique enables high precision measurement of changes in tissue absorbance caused by blood pulsation. It is very important in the non-invasive in vivo concentration measurement of blood.