Objective: To investigate the electromagnetic field and specific absorptionrate (SAR) distribution of different structure applicators with different depths for treating bonetumors using microwave hyperthermia. Methods...Objective: To investigate the electromagnetic field and specific absorptionrate (SAR) distribution of different structure applicators with different depths for treating bonetumors using microwave hyperthermia. Methods: The finite element method (FEM) was used to calculate,electromagnetic field and SAR distribution. Two different structure applicators were simulated. Theone is simple coaxial antenna, which has been successfully used in clinic treating bone tumors inTangdu hospital of the Forth Military Medical University several years. It was formed by a coaxialcable peeled off the out copper at end. The other applicator was coaxial- slot antenna, which waswidely used in microwave hyperthermia. The applicator inserted into the cylindrical bone withdifferent depths, and worked at the frequency of 2 450 MHz. Results: The electric field and SARgenerated by the simple coaxial applicator were mainly concentrated out the tissues, and were notuniform in the tissues, while the coaxial- slot applicator well transmits the electric field and SARinto the tissues, and can easily treat different position by adjusting the slat position.Conclusion: The results calculated by EFM, were well accordant with the experimental and clinicalresulls, and will be important for improving the clinical effects of microwave hyperthermia.展开更多
A 3D femoral model was built to obtain the three-dimensional temperature distribution of femur and its surrounding tissues and provide references for clinical applications. According to the relationship between gray-v...A 3D femoral model was built to obtain the three-dimensional temperature distribution of femur and its surrounding tissues and provide references for clinical applications. According to the relationship between gray-value and material properties,the model was assigned with various materials to make sure that it is more similar to the real femur in geometry and physical properties. 3D temperature distribution is obtained by using finite element analysis software ANSYS 11. 0 on the basis of heat conduction theory,Laplace equation,Pennes bio-heat transfer equation,thermo physical parameters of bone tissues,the boundary condition,and initial conditions. Taken the asymmetry of the 3D distribution of temperature into account,it is necessary to adopt the heating method with multiple heat sources. This method can ensure that the temperature fields match well with the tumor tissues and kill the tumor cells efficiently under the condition of protecting the normal tissues from damage. The analysis results supply important guidance for determining the needle position and the needle number and controlling the intensity of heating.展开更多
Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values esti...Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values estimated by this method under various diameters (D) of magnetic nanoparticles (MNPs) and amplitudes (H<sub>0</sub>) and frequencies (f) of an alternating magnetic field (AMF). In our method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically, in which the magnetic field strength at time t (H(t)) was assumed to be given by , with H<sub>s</sub> being the strength of the SMF. We also investigated the SLP values in the case when the SMF with a field-free point (FFP) generated by two solenoid coils was used. The SLP value in the quasi steady state (SLP<sub>qss</sub>) decreased with increasing H<sub>s</sub>. The plot of the SLP<sub>qss</sub> values against the position from the FFP became narrow as the gradient strength of the SMF (G<sub>s</sub>) increased. Conversely, it became broad as G<sub>s</sub> decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the H<sub>s</sub> and G<sub>s</sub> values, respectively. In conclusion, our method will be useful for estimating the SLP in the presence of both the AMF and SMF and for designing an effective local heating system for magnetic hyperthermia in order to reduce the risk of overheating surrounding healthy tissues.展开更多
Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanopa...Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanoparticles, and multifunctional magnetic devices for cancer multimodality treatment are also introduced.展开更多
Hyperthermia is a treatment mechanism by which cancer cells can be damaged. In this mode of treatment, electromagnetic fields are used for increasing the temperature of malignant tissues at sufficiently high level for...Hyperthermia is a treatment mechanism by which cancer cells can be damaged. In this mode of treatment, electromagnetic fields are used for increasing the temperature of malignant tissues at sufficiently high level for destroying them. In this paper, major problems of hyperthermia and some proposed solutions are presented.展开更多
When the technique of invasive microwave hyperthermia is applied to cancer treating, the distribution of microwave thermal field and the effect of the therapy are determined by the type of microwave radiative antenna....When the technique of invasive microwave hyperthermia is applied to cancer treating, the distribution of microwave thermal field and the effect of the therapy are determined by the type of microwave radiative antenna. The thermal field of biological tissue produced by microwave radiative antenna is investigated in this paper. The distribution of thermal field and specific absorption rate (SAR) of invasive coaxial-slot antenna in the frequency of 2450 MHz are obtained by the technique of finite element analysis. According to the experiment of heating the ex vivo pork liver by this kind of antenna, the result concordant with the theory is obtained. Therefore, it is suggested that this research could be a reference for clinical therapy and operation scheme.展开更多
Our purpose in this study was to present three methods for estimating specific loss power (SLP) in magnetic hyperthermia with use of an alternating magnetic field (AMF) and magnetic nanoparticles (MNPs) and to compare...Our purpose in this study was to present three methods for estimating specific loss power (SLP) in magnetic hyperthermia with use of an alternating magnetic field (AMF) and magnetic nanoparticles (MNPs) and to compare the SLP values estimated by the three methods using simulation studies under various diameters of MNPs (D), amplitudes (H<sub>0</sub>) and frequencies of AMF (f). In the first method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically (SLP<sub>1</sub>). In the second method, the SLP was obtained by solving Shliomis’ relaxation equation using the complex susceptibility (SLP<sub>2</sub>). The third method was based on Rosensweig’s model (SLP<sub>3</sub>). The SLP<sub>3</sub> value changed largely depending on the magnetic field strength (H) in the Langevin parameter (§) and it became maximum (SLP<sub>3</sub><sup>max</sup>) and minimum (SLP<sub>3</sub><sup>min</sup>) when H was 0 and ±H<sub>0</sub>, respectively. The relative difference between SLP<sub>1</sub> and SLP<sub>2</sub> was the largest and increased with increasing D and H<sub>0</sub>, whereas that between SLP<sub>1</sub> and was the smallest and was almost constant regardless of D and H<sub>0</sub>, suggesting that H in ξ should be taken as H<sub>0</sub> in estimating the SLP using Rosensweig’s model. In conclusion, this study will be useful for optimizing the parameters of AMF in magnetic hyperthermia and for the optimal design of MNPs for magnetic hyperthermia.展开更多
This paper presents a heat transfer model for the hyperthermia treatment of cervix cancer using a intracavitary microwave applicator and based on which the 3-D finite element simulation of the temperature fields have ...This paper presents a heat transfer model for the hyperthermia treatment of cervix cancer using a intracavitary microwave applicator and based on which the 3-D finite element simulation of the temperature fields have done. Before then the specific absorption rate (SAR) distribution for the transvaginal probe have been measured in a phantom. The variations of the parameters have been investigated, too, for optimization. At last, the results of simulation are compared to that measured in the phantom and some instructive conclusions are presented for critical application.展开更多
Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties a...Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring equipment.The specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field amplitude.In this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/m.The measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain range.In combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and coercivity.Thus when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.展开更多
文摘Objective: To investigate the electromagnetic field and specific absorptionrate (SAR) distribution of different structure applicators with different depths for treating bonetumors using microwave hyperthermia. Methods: The finite element method (FEM) was used to calculate,electromagnetic field and SAR distribution. Two different structure applicators were simulated. Theone is simple coaxial antenna, which has been successfully used in clinic treating bone tumors inTangdu hospital of the Forth Military Medical University several years. It was formed by a coaxialcable peeled off the out copper at end. The other applicator was coaxial- slot antenna, which waswidely used in microwave hyperthermia. The applicator inserted into the cylindrical bone withdifferent depths, and worked at the frequency of 2 450 MHz. Results: The electric field and SARgenerated by the simple coaxial applicator were mainly concentrated out the tissues, and were notuniform in the tissues, while the coaxial- slot applicator well transmits the electric field and SARinto the tissues, and can easily treat different position by adjusting the slat position.Conclusion: The results calculated by EFM, were well accordant with the experimental and clinicalresulls, and will be important for improving the clinical effects of microwave hyperthermia.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61272387)the Program for New Century Excellent Talents in University(Grant No.NCET-13-0756)the Distinguished Young Scientists Funds of Heilongjiang Province(Grant No.JC201302)
文摘A 3D femoral model was built to obtain the three-dimensional temperature distribution of femur and its surrounding tissues and provide references for clinical applications. According to the relationship between gray-value and material properties,the model was assigned with various materials to make sure that it is more similar to the real femur in geometry and physical properties. 3D temperature distribution is obtained by using finite element analysis software ANSYS 11. 0 on the basis of heat conduction theory,Laplace equation,Pennes bio-heat transfer equation,thermo physical parameters of bone tissues,the boundary condition,and initial conditions. Taken the asymmetry of the 3D distribution of temperature into account,it is necessary to adopt the heating method with multiple heat sources. This method can ensure that the temperature fields match well with the tumor tissues and kill the tumor cells efficiently under the condition of protecting the normal tissues from damage. The analysis results supply important guidance for determining the needle position and the needle number and controlling the intensity of heating.
文摘Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values estimated by this method under various diameters (D) of magnetic nanoparticles (MNPs) and amplitudes (H<sub>0</sub>) and frequencies (f) of an alternating magnetic field (AMF). In our method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically, in which the magnetic field strength at time t (H(t)) was assumed to be given by , with H<sub>s</sub> being the strength of the SMF. We also investigated the SLP values in the case when the SMF with a field-free point (FFP) generated by two solenoid coils was used. The SLP value in the quasi steady state (SLP<sub>qss</sub>) decreased with increasing H<sub>s</sub>. The plot of the SLP<sub>qss</sub> values against the position from the FFP became narrow as the gradient strength of the SMF (G<sub>s</sub>) increased. Conversely, it became broad as G<sub>s</sub> decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the H<sub>s</sub> and G<sub>s</sub> values, respectively. In conclusion, our method will be useful for estimating the SLP in the presence of both the AMF and SMF and for designing an effective local heating system for magnetic hyperthermia in order to reduce the risk of overheating surrounding healthy tissues.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.81172182,81172120,and 81041040)the 7th Singapore–China Cooperative Research Project Call between Agency of Science,Technology and Research(A*STAR)+1 种基金Singapore and the Ministry of Science and Technology(MOST),China(Grant No.20113010006)the National Key Technology Support Program(Grant No.2012857818)
文摘Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanoparticles, and multifunctional magnetic devices for cancer multimodality treatment are also introduced.
文摘Hyperthermia is a treatment mechanism by which cancer cells can be damaged. In this mode of treatment, electromagnetic fields are used for increasing the temperature of malignant tissues at sufficiently high level for destroying them. In this paper, major problems of hyperthermia and some proposed solutions are presented.
文摘When the technique of invasive microwave hyperthermia is applied to cancer treating, the distribution of microwave thermal field and the effect of the therapy are determined by the type of microwave radiative antenna. The thermal field of biological tissue produced by microwave radiative antenna is investigated in this paper. The distribution of thermal field and specific absorption rate (SAR) of invasive coaxial-slot antenna in the frequency of 2450 MHz are obtained by the technique of finite element analysis. According to the experiment of heating the ex vivo pork liver by this kind of antenna, the result concordant with the theory is obtained. Therefore, it is suggested that this research could be a reference for clinical therapy and operation scheme.
文摘Our purpose in this study was to present three methods for estimating specific loss power (SLP) in magnetic hyperthermia with use of an alternating magnetic field (AMF) and magnetic nanoparticles (MNPs) and to compare the SLP values estimated by the three methods using simulation studies under various diameters of MNPs (D), amplitudes (H<sub>0</sub>) and frequencies of AMF (f). In the first method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically (SLP<sub>1</sub>). In the second method, the SLP was obtained by solving Shliomis’ relaxation equation using the complex susceptibility (SLP<sub>2</sub>). The third method was based on Rosensweig’s model (SLP<sub>3</sub>). The SLP<sub>3</sub> value changed largely depending on the magnetic field strength (H) in the Langevin parameter (§) and it became maximum (SLP<sub>3</sub><sup>max</sup>) and minimum (SLP<sub>3</sub><sup>min</sup>) when H was 0 and ±H<sub>0</sub>, respectively. The relative difference between SLP<sub>1</sub> and SLP<sub>2</sub> was the largest and increased with increasing D and H<sub>0</sub>, whereas that between SLP<sub>1</sub> and was the smallest and was almost constant regardless of D and H<sub>0</sub>, suggesting that H in ξ should be taken as H<sub>0</sub> in estimating the SLP using Rosensweig’s model. In conclusion, this study will be useful for optimizing the parameters of AMF in magnetic hyperthermia and for the optimal design of MNPs for magnetic hyperthermia.
文摘This paper presents a heat transfer model for the hyperthermia treatment of cervix cancer using a intracavitary microwave applicator and based on which the 3-D finite element simulation of the temperature fields have done. Before then the specific absorption rate (SAR) distribution for the transvaginal probe have been measured in a phantom. The variations of the parameters have been investigated, too, for optimization. At last, the results of simulation are compared to that measured in the phantom and some instructive conclusions are presented for critical application.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB41010403)the National Natural Science Foundation of China(Nos.41804070,41774076,41621004)+2 种基金the Key Program of Chinese Academy of Sciences(No.QYZDJ-SSWDQC024)the Key Research Program of the Institute of Geology and Geophysics,CAS(No.IGGCAS-201903)the PetroChina Innovation Foundation(No.2020D-5007-0105)。
文摘Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring equipment.The specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field amplitude.In this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/m.The measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain range.In combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and coercivity.Thus when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.
