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Estimation of internal distribution of temperature inside biological tissues by means of multifrequency microwave thermograph
Abstract
The paper presents problems connected with thermal radiation of
human bodies in the microwave range in respect of diagnosis of breast
carcinoma. A mathematical model of transmission of thermal radiation
through tissues is introduced and methods of measurement of temperature,
depth and size of heat source, by means of multifrequency microwave
thermography, are described. Theoretical considerations are supplemented
with presentation of the results of experiments
... Estimation of spatial temperature distribution inside the investigated object is particularly interesting from the practical point of view. The solution presented below uses the power thermography at different frequencies [18, 19]. This method is based on increase of intensity of thermal radiation and decrease of penetration depth into biological tissues with frequency. ...
This paper presents problems related to thermal radiation of human bodies in microwave range with respect to diagnosis of breast carcinoma. A mathematical model of thermal radiation transfer through tissues is introduced and methods of measurement of temperature, depth and size of a heat source, by means of multifrequency microwave thermograph are described. Theoretical considerations are supplemented by presentation of experimental results.
This paper presents problems related to thermal radiation of human
bodies in the microwave range in relation to diagnosis of breast
carcinoma. A mathematical model of thermal radiation transmission
through tissues is introduced and methods of measurement of temperature
and the depth and size of a heat source, by means of multifrequency
microwave thermography, are described. Theoretical considerations are
supplemented by results of experiments
In order to understand the photothermal effect mechanism of laser interaction with skin, we employed a two-layer model to describe the heat generation, transportation, and dispersion in the procedure of laser interaction with skin. A skin temperature distribution corresponding to the laser interaction direction is calculated to describe the time of skin gasification and the possible thermal injury. The magnitude of time is ms. This basic process provides a possible quantitative recognition of the applications of laser in clinical skin care.
Multifrequency microwave radiometry has been investigated for non-invasive measurement of temperatures in a human body. In this paper, we propose a new temperature profile model function, which is based on thermo-physiological considerations, for use in a model fitting method of retrieving a temperature profile from a set of multifrequency radiometric data. The microwave radiometric technique using the new model function was tested by numerical simulations against animal experiment and clinical data reported elsewhere. The results show that the microwave radiometric technique can be used effectively to measure temperature profiles in tissues over a depth range from 0 to about 4.5 cm.
A method of retrieving a temperature-depth profile in biological object from a set of multi-frequency microwave radiometric data has been developed. The method is a combination of model-fitting and Monte Carlo techniques and is capable of estimating a profile and its confidence interval as a function of the depth. We use 2σ -intervals as a measure of the precision of tissue temperature measurements. The method was tested and supported by an experiment in which temperature distributions in a muscle equivalent agar phantom were measured using a 5-band, 1-3.8 GHz radiometer with the brightness temperature resolution of 0.05-0.07 K. A typical result of the experiment showed that 2σ -intervals were 1 K or less for 0 < z < 3 cm, 1.4 K at z = 4 cm, and 3 K at z = 5 cm. A numerical simulation study was made using this technique to assess effects of the selection of measurement frequencies, number of frequency bands, brightness temperature resolution of radiometer and thickness of fat layer on the precision. Results indicated that 2σ -intervals of about 1.0 K or less over a 0-5 cm depth range could be achieved by a 6-band, 0.55-3.8 GHz radiometer with the brightness temperature resolution of 0.05 K.
Microwave radiometry, used routinely since 1984 for non-invasive temperature measurements during hyperthermia sessions for superficial tumours treatment has proven its efficiency for temperature control. From radiometric temperature measurements in two frequency ranges (around 1 and 3 GHz) and superficial (or cutaneous) temperature measurements achieved during hyperthermia sessions, a numerical method to obtain the two-dimensional thermal profile has been developed and implemented. This method is based on hyperthermia simulation from the bioheat equation, the absorbed microwave power calculation in the medium taking into account the radiative diagram of the applicator, and the calculation of radiometric temperatures. From these experimental measurements (radiometric and superficial temperatures, heating power, dielectric and thermal characteristics), a program to determine the bidimensional distribution of temperature during the hyperthermia session has been developed, tested and used during and after clinical treatments.
Compensated microwave thermometer for medical applications
- B Stec
- M Zurawski