本文選題：高強(qiáng)度聚焦超聲 + 電阻抗層析成像��； 參考：《物理學(xué)報》2017年16期

【摘要】：作為一種對正常組織無損傷且不易引起癌細(xì)胞轉(zhuǎn)移的非入侵腫瘤治療手段,高強(qiáng)度聚焦超聲(HIFU)治療過程中焦域的溫度監(jiān)測是實現(xiàn)劑量精準(zhǔn)控制的關(guān)鍵.本文基于生物組織的溫度-電阻抗的關(guān)系,將電阻抗層析成像(EIT)和HIFU治療相結(jié)合,提出了一種利用組織焦平面的表面電壓實現(xiàn)電阻抗重構(gòu)的檢測技術(shù).建立了HIFU治療和EIT綜合系統(tǒng)模型,在考慮組織的聲吸收條件下,對三維Helmholtz方程在柱坐標(biāo)下的聲場計算進(jìn)行了二維簡化,并引入Pennes生物熱傳導(dǎo)方程來計算HIFU焦域的聲壓和溫升分布特性;引入生物組織的溫度-電阻抗關(guān)系,基于麥克斯韋電磁場理論,建立了具有溫度分布HIFU焦域的電流和電壓計算模型,利用恒流注入的邊界條件實現(xiàn)電場計算,獲得焦平面的表面電壓分布.在數(shù)值計算中,利用實驗聚焦換能器參數(shù),模擬了在固定聲功率下組織焦域的聲場和溫度場分布,以及中心和偏心聚焦條件下不同治療時刻的電導(dǎo)率分布;然后通過對稱電極的循環(huán)電流注入,計算了組織模型焦平面內(nèi)的電流密度和電勢分布,獲得了焦平面圓周分布的表面電極電壓;進(jìn)一步采用修正的牛頓-拉夫遜算法,利用32×32的表面電極電壓實現(xiàn)了焦平面內(nèi)電導(dǎo)率分布的重建.結(jié)果表明,基于溫度-電阻抗關(guān)系的EIT電導(dǎo)率重建技術(shù)不但能準(zhǔn)確定位HIFU焦域中心,還能恢復(fù)HIFU治療中焦域的溫度分布,證明了EIT用于HIFU治療中溫度監(jiān)測的可行性,為其療效評估和劑量控制提供了一種無創(chuàng)電阻抗測量和成像新方法.
[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.
【作者單位】： 南京師范大學(xué)物理科學(xué)與技術(shù)學(xué)院;
【基金】：國家自然科學(xué)基金(批準(zhǔn)號:11474166,11604156) 江蘇省自然科學(xué)基金(批準(zhǔn)號:BK20161013) 國家博士后基金(批準(zhǔn)號:2016M591874) 江蘇高校優(yōu)勢學(xué)科資助的課題~~
【分類號】：TB559

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