基于电阻抗层析成像的高强度聚焦超声温度监测技术

发布时间：2018-06-06 17:48

本文选题：高强度聚焦超声 + 电阻抗层析成像　；参考：《物理学报》2017年16期

【摘要】：作为一种对正常组织无损伤且不易引起癌细胞转移的非入侵肿瘤治疗手段,高强度聚焦超声(HIFU)治疗过程中焦域的温度监测是实现剂量精准控制的关键.本文基于生物组织的温度-电阻抗的关系,将电阻抗层析成像(EIT)和HIFU治疗相结合,提出了一种利用组织焦平面的表面电压实现电阻抗重构的检测技术.建立了HIFU治疗和EIT综合系统模型,在考虑组织的声吸收条件下,对三维Helmholtz方程在柱坐标下的声场计算进行了二维简化,并引入Pennes生物热传导方程来计算HIFU焦域的声压和温升分布特性;引入生物组织的温度-电阻抗关系,基于麦克斯韦电磁场理论,建立了具有温度分布HIFU焦域的电流和电压计算模型,利用恒流注入的边界条件实现电场计算,获得焦平面的表面电压分布.在数值计算中,利用实验聚焦换能器参数,模拟了在固定声功率下组织焦域的声场和温度场分布,以及中心和偏心聚焦条件下不同治疗时刻的电导率分布;然后通过对称电极的循环电流注入,计算了组织模型焦平面内的电流密度和电势分布,获得了焦平面圆周分布的表面电极电压;进一步采用修正的牛顿-拉夫逊算法,利用32×32的表面电极电压实现了焦平面内电导率分布的重建.结果表明,基于温度-电阻抗关系的EIT电导率重建技术不但能准确定位HIFU焦域中心,还能恢复HIFU治疗中焦域的温度分布,证明了EIT用于HIFU治疗中温度监测的可行性,为其疗效评估和剂量控制提供了一种无创电阻抗测量和成像新方法.
[Abstract]:As a non-invasive tumor treatment method which has no damage to normal tissues and is not easy to cause cancer cell metastasis, high intensity focused ultrasound (HIFU) temperature monitoring is the key to accurate dose control in the process of HIFU (High intensity focused Ultrasound) therapy. Based on the relationship between temperature and electrical impedance of biological tissues, this paper presents a new method for detecting electrical impedance reconstruction by using the surface voltage of tissue focal plane, which combines EITs with HIFU therapy. The model of HIFU therapy and EIT integrated system is established. The three-dimensional Helmholtz equation is simplified in terms of the acoustic field in cylindrical coordinates under the condition of tissue acoustic absorption. Pennes' biothermic conduction equation is introduced to calculate the characteristics of acoustic pressure and temperature rise distribution in HIFU's focal region, and the relationship between temperature and electrical impedance of biological tissue is introduced, which is based on Maxwell's electromagnetic field theory. The current and voltage calculation model with HIFU focal region with temperature distribution is established. The electric field is calculated by using the boundary condition of constant current injection, and the voltage distribution on the surface of focal plane is obtained. In the numerical calculation, the distribution of the sound field and temperature field in the focal region of the tissue under the fixed sound power and the electrical conductivity distribution at different treatment times under the condition of center and eccentric focusing are simulated by using the parameters of the experimental focusing transducer. Then the current density and potential distribution in the focal plane of the tissue model are calculated by the cyclic current injection of the symmetric electrode, and the surface electrode voltage of the focal plane circumference distribution is obtained, and the modified Newton-Raphson algorithm is adopted. The surface electrode voltage of 32 脳 32 is used to reconstruct the conductivity distribution in focal plane. The results show that the EIT conductivity reconstruction technique based on the relationship between temperature and impedance can not only accurately locate the focal region center of HIFU, but also restore the temperature distribution of the focal region in HIFU therapy, which proves the feasibility of EIT in temperature monitoring in HIFU therapy. A new method of noninvasive electrical impedance measurement and imaging is provided for the evaluation of therapeutic effect and dose control.
【作者单位】：南京师范大学物理科学与技术学院;
【基金】：国家自然科学基金(批准号:11474166,11604156) 江苏省自然科学基金(批准号:BK20161013) 国家博士后基金(批准号:2016M591874) 江苏高校优势学科资助的课题~~
【分类号】：TB559

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