A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues
<p>Measuring the parameters of biological tissues (include in vivo) is of great importance for medical diagnostics. For example, the value of the blood perfusion parameter is associated with the state of the blood microcirculation system and its functioning affects the state of the tissues of...
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| Format: | Article |
| Language: | Russian |
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MGTU im. N.È. Baumana
2014-01-01
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| Series: | Nauka i Obrazovanie |
| Subjects: | |
| Online Access: | http://technomag.edu.ru/jour/article/view/529 |
| _version_ | 1811322233639927808 |
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| author | S. Yu. Makarov |
| author_facet | S. Yu. Makarov |
| author_sort | S. Yu. Makarov |
| collection | DOAJ |
| description | <p>Measuring the parameters of biological tissues (include in vivo) is of great importance for medical diagnostics. For example, the value of the blood perfusion parameter is associated with the state of the blood microcirculation system and its functioning affects the state of the tissues of almost all organs. This work describes a previously proposed principle [1] in generalized terms. The principle is intended for noninvasive measuring the parameters of stationary heat transfer in biological tissues. The results of some experiments (natural and numeric) are also presented in the research.</p><p>For noninvasive measurement of thermophysical parameters a number of techniques have been developed using non-stationary thermal process in biological tissue [2][3]. But these techniques require the collecting a lot of data to represent the time-dependent thermal signal. In addition, subsequent processing with specialized algorithms is required for optimal selecting the parameters. The goal of this research is to develop an alternative approach using stationary thermal process for non-invasive measuring the parameters of stationary heat transfer in living tissues.</p><p>A general principle can be formulated for the measurement methods based on this approach. Namely, the variations (changes) of two physical values are measured in the experiment at the transition from one thermal stationary state to another. One of these two physical values unambiguously determines the stationary thermal field into the biological tissue under specified experimental conditions while the other one is unambiguously determined through the thermal field. Then, the parameters can be found from the numerical (or analytical) functional dependencies linking the measured variations because the dependencies contain unknown parameters.</p><p>The dependencies are expressed in terms of the formula:</p><p>dqi = fi({pj},Ui) dUi,</p><p>Here dqi is a variation of a physical value q which is unambiguously determined from the thermal field in biotissue (measuring procedure with the number i), dUiis a variation of a physical value U which unambiguously determines the steady-state thermal field, {pj} is a set of parameters to be measured.</p><p>Theoretical analysis has shown that the implementation of the above principle leads to the equations that do not contain unknown values of blood temperature and power density of biological heat sources, unlike the starting Pennes equation [4]. This is the main advantage of the developed approach in comparison with non-stationary methods. In addition, there is no dynamic measurement error which is inevitably associated with the measurement procedure for the transient processes.</p><p>Numerical and physical experiments have been carried out to validate the functionality of the above principle for noninvasive measuring the parameters of stationary heat transfer. For example, with use a thermophysical model of biological tissue [5] the procedure of measuring was simulated to obtain the values of two thermophysical parameters of model biological tissue, namely the blood perfusion (in absolute units) and the thermal conductivity. Also, with use a specially designed probe the measurements were carried out for the natural biological tissue of human skin epithelium. The blood perfusion parameter estimation value is in good agreement with the literature data [6], despite the illustrative purpose of conducted measurements. These experiments have also demonstrated the possibility of simultaneous measuring the several thermophysical properties of biological tissue in a noninvasive manner, using a rather simple equipment.</p><p>Formula (1) can contain not only thermophysical parameters of the living tissue, but any other parameters provided that each one unambiguously affects the heat transfer in a particular experiment. For example, it was shown that it is possible to recover the thicknesses of subcutaneous tissue layers of model of skin on the results of thermal measurements on the basis of the described principle. With function of external sources entering into the Pennes equation, the principle will permit to obtain the parameters of interaction of different physical fields (optical, acoustic, etc.) with biological tissue when this interaction leads to the thermal effect provided that the thermal field is a steady state.</p><p>Thus, the presented principle can be regarded as a basis for development of new non-invasive techniques of measuring the various parameters affecting the stationary process of heat transfer in the living tissues. Also, the principle eliminates the influence of unknown parameters of blood temperature and biological sources of heat. The appropriate methods based on this principle do not require collecting and processing a lot of data, and do not generate the dynamic measurement error. Besides, the original values of the measured parameters are not significantly disturbed during the measuring procedure.</p><p>Further development of this work will include:</p><p>1) development of new measuring techniques based on the described principle for measuring the thermophysical parameters of living tissue with better accuracy</p><p>2) expansion of the list of measured parameters including some constants of interaction with different physical fields</p><p>3) improvement of data processing algorithms.</p> |
| first_indexed | 2024-04-13T13:31:32Z |
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| id | doaj.art-803a9e6c27f74082886ce613ce2ee4f1 |
| institution | Directory Open Access Journal |
| issn | 1994-0408 |
| language | Russian |
| last_indexed | 2024-04-13T13:31:32Z |
| publishDate | 2014-01-01 |
| publisher | MGTU im. N.È. Baumana |
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| series | Nauka i Obrazovanie |
| spelling | doaj.art-803a9e6c27f74082886ce613ce2ee4f12022-12-22T02:44:57ZrusMGTU im. N.È. BaumanaNauka i Obrazovanie1994-04082014-01-010223324610.7463/0214.0695233529A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissuesS. Yu. Makarov0VolGU<p>Measuring the parameters of biological tissues (include in vivo) is of great importance for medical diagnostics. For example, the value of the blood perfusion parameter is associated with the state of the blood microcirculation system and its functioning affects the state of the tissues of almost all organs. This work describes a previously proposed principle [1] in generalized terms. The principle is intended for noninvasive measuring the parameters of stationary heat transfer in biological tissues. The results of some experiments (natural and numeric) are also presented in the research.</p><p>For noninvasive measurement of thermophysical parameters a number of techniques have been developed using non-stationary thermal process in biological tissue [2][3]. But these techniques require the collecting a lot of data to represent the time-dependent thermal signal. In addition, subsequent processing with specialized algorithms is required for optimal selecting the parameters. The goal of this research is to develop an alternative approach using stationary thermal process for non-invasive measuring the parameters of stationary heat transfer in living tissues.</p><p>A general principle can be formulated for the measurement methods based on this approach. Namely, the variations (changes) of two physical values are measured in the experiment at the transition from one thermal stationary state to another. One of these two physical values unambiguously determines the stationary thermal field into the biological tissue under specified experimental conditions while the other one is unambiguously determined through the thermal field. Then, the parameters can be found from the numerical (or analytical) functional dependencies linking the measured variations because the dependencies contain unknown parameters.</p><p>The dependencies are expressed in terms of the formula:</p><p>dqi = fi({pj},Ui) dUi,</p><p>Here dqi is a variation of a physical value q which is unambiguously determined from the thermal field in biotissue (measuring procedure with the number i), dUiis a variation of a physical value U which unambiguously determines the steady-state thermal field, {pj} is a set of parameters to be measured.</p><p>Theoretical analysis has shown that the implementation of the above principle leads to the equations that do not contain unknown values of blood temperature and power density of biological heat sources, unlike the starting Pennes equation [4]. This is the main advantage of the developed approach in comparison with non-stationary methods. In addition, there is no dynamic measurement error which is inevitably associated with the measurement procedure for the transient processes.</p><p>Numerical and physical experiments have been carried out to validate the functionality of the above principle for noninvasive measuring the parameters of stationary heat transfer. For example, with use a thermophysical model of biological tissue [5] the procedure of measuring was simulated to obtain the values of two thermophysical parameters of model biological tissue, namely the blood perfusion (in absolute units) and the thermal conductivity. Also, with use a specially designed probe the measurements were carried out for the natural biological tissue of human skin epithelium. The blood perfusion parameter estimation value is in good agreement with the literature data [6], despite the illustrative purpose of conducted measurements. These experiments have also demonstrated the possibility of simultaneous measuring the several thermophysical properties of biological tissue in a noninvasive manner, using a rather simple equipment.</p><p>Formula (1) can contain not only thermophysical parameters of the living tissue, but any other parameters provided that each one unambiguously affects the heat transfer in a particular experiment. For example, it was shown that it is possible to recover the thicknesses of subcutaneous tissue layers of model of skin on the results of thermal measurements on the basis of the described principle. With function of external sources entering into the Pennes equation, the principle will permit to obtain the parameters of interaction of different physical fields (optical, acoustic, etc.) with biological tissue when this interaction leads to the thermal effect provided that the thermal field is a steady state.</p><p>Thus, the presented principle can be regarded as a basis for development of new non-invasive techniques of measuring the various parameters affecting the stationary process of heat transfer in the living tissues. Also, the principle eliminates the influence of unknown parameters of blood temperature and biological sources of heat. The appropriate methods based on this principle do not require collecting and processing a lot of data, and do not generate the dynamic measurement error. Besides, the original values of the measured parameters are not significantly disturbed during the measuring procedure.</p><p>Further development of this work will include:</p><p>1) development of new measuring techniques based on the described principle for measuring the thermophysical parameters of living tissue with better accuracy</p><p>2) expansion of the list of measured parameters including some constants of interaction with different physical fields</p><p>3) improvement of data processing algorithms.</p>http://technomag.edu.ru/jour/article/view/529perfusion |
| spellingShingle | S. Yu. Makarov A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues Nauka i Obrazovanie perfusion |
| title | A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues |
| title_full | A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues |
| title_fullStr | A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues |
| title_full_unstemmed | A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues |
| title_short | A principle for the noninvasive measurement of steady-state heat transfer parameters in living tissues |
| title_sort | principle for the noninvasive measurement of steady state heat transfer parameters in living tissues |
| topic | perfusion |
| url | http://technomag.edu.ru/jour/article/view/529 |
| work_keys_str_mv | AT syumakarov aprincipleforthenoninvasivemeasurementofsteadystateheattransferparametersinlivingtissues AT syumakarov principleforthenoninvasivemeasurementofsteadystateheattransferparametersinlivingtissues |