Measurement of blood perfusion has been playing an important role in the field of bioheat transfer and clinical
thermotherapy. However, it is not easy to gain thermal induced dynamics of blood perfusion of local tissue. Laser
speckle techniques we developed were valid. In this paper, we reviewed our progress on studying thermal induced
dynamics of blood perfusion of mice's mesentery with laser speckle techniques which included laser speckle microscopy
with CCD camera for isolate vessel and laser speckle imaging for local vessels of mesentery of mice. The principles of
the two kinds of laser speckle techniques were introduced briefly. The blood perfusion of normal and tumor mice's
mesentery were showed during different constant temperatures (41-45°C) by laser speckle imaging technique. Further
more, the dynamics of velocity, diameter and blood perfusion for normal and tumor were compared. The results showed
that tumor was more sensitive to heat than normal tissue, which accorded with pathological investigation. Finally, the
quantitative relationship among the blood perfusion, the temperature-dependent and the damage-dependent was
established. The model could describe successfully thermal induced dynamics of blood perfusion of mesentery for both
normal and tumor mice.
Thermotherapy could be selective to cure tumor because tumor is sensitive to temperature rise. The tumor blood flow rate, the average blood perfusion of tissue or temperature during heating was investigated respectively. However, thermal induced change in the vessel diameter of tumor was neglected. Especially, all of the above parameters were seldom measured at simultaneity. In this work, thermal induced effects on normal and tumor of mouse mesentery were investigated based on measuring microcirculation parameters and temperature. The dynamic blood flow rate was measured by the laser speckle microscopy, and the corresponding blood vessel diameter was recorded by the video camera, then the blood perfusion was deduced. Meanwhile, the temperature was recorded by high sensitively thermocouple. The results showed that the maximum change in diameter was larger than flow rate and blood perfusion for the both kinds of tissue under the same heating. Moreover, the maximum changes in vessel diameter, blood flow and perfusion in tumor are lower than those in normal during. The temperature rise in tumor changed more quickly than in normal tissue, and the critical temperature of thermal damage in the normal tissue was higher than the tumor. These measurements further proved that the tumor microcirculation was more sensitivity to heat than the normal tissue. This study is very important to know thermal induced affection from blood perfusion of micro vessel net both in tumor and normal tissue. It will help to explore thermotherapy mechanism and evaluate the thermotherapy effect, ascertain thermal dose, and select appropriate Rx.
Based on the theory of the thermotherapy and recent development, the optical methods are introduced to investigate thermally induced changes in tissue. The typical results show that the scattering coefficient changes with damage integral of tissue, which provides a new method for measurement of damage parameters. By establishing the relationship between the absorption coefficient and dehydration of tissue, it is possible to deduce the dynamics of thermal properties. Optical imaging on thermally induced blood perfusion will help to know the dependence relation of blood and damage integral. It is very important for study dosimetry of thermotherapy based on monitoring of thermotherapy with optical techniques.
In hyperthermia, blood flow plays a major role in determining the effectiveness of hyperthermia used alone or combined with radiation therapy or chemotherapy. The acidity, the nutritional supply, partial pressure of oxygen and distribution of drugs are closely related to blood flow. To facilitate these issues we put forward a simple optical method to measure dynamical change of blood volume combining laser speckle measurement and CCD microscopic imaging technique. In this study, we selected seven different temperatures (40°C, 42°C, 43°C, 44°C, 45°C, 47°C, 49°C), and monitored variations of blood velocity and diameter of microvessels (15~50μm) on BALB/c mouse’s mesentery and through tumor during 30 minutes at each temperature. The results showed that the critical temperatures of normal and tumor microvessel were 43°C and 42°C. Tumor is more thermal sensitive than normal tissue. And the capacity of tumor blood flow to increase upon heating appears to be rather limited. The increase of blood volume was not more than 2.0-fold.
In hyperthermia, the accurate measurement of blood flow is regarded as a key footstep to describe physiological status of subjects since blood flow serves both to deliver oxygen and the metabolic substrates, and to carry away heat and the waste products of metabolism. To facilitate these issues we put forward a simple optical method to measure dynamical change of blood volume combining laser speckle measurement and CCD microscopic imaging technique. In this study, at first we selected six different temperatures (31°C, 33°C, 35°C, 37°C, 38°C, 39°C), followed variations of blood velocity and diameter in microvessels (15~50μm) on rat’s mesentery after 30 minutes at each temperature. Furthermore, during heated at seven higher different temperatures (41°C, 43°C, 45°C, 46°C, 49°C, 51°C, 54°C) for 30 minutes respectively, diameter and velocity were measured in vivo and real time. The results showed that changes of blood volume ranged from 68~110% when temperature altered, and the relationship between the constant value and the temperature approximated linear (k=0.05±0.005). While heated at 41°C~46°C for 30 min, velocity increased slightly but diameter and blood volume increased markedly and finally got to constants. The value of velocity increased to maximum when microvessels were heated with 49°C for 12 min. At this temperature, diameter and blood volume increased during the first 14 min, but began to decrease when heated longer. When temperature is higher than 49°C, 51°C, 54°C, velocity ,diameter and blood volume all increased at first and then decreased during 30 min and at the end of heating they were all far lower than control value. We draw our conclusion that the critical temperature is 49°C for intestine microcirculation with heating for 30 min. And the rates of thermal damage are proportion to temperature for the same heating time.