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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.As a new treatment modality with little thermal damage and few cell metastases to surrounding normal tissues, high intensity focused ultrasound (HIFU) therapy is considered to be one of the most promising technologies for tumor therapy in the 21st century. However, noninvasive temperature monitoring for the focal region exhibits great significance of precise thermal dosage control in HIFU treatment. By combining electrical impedance measurement and HIFU, an electrical impedance tomography (EIT) based temperature monitoring method using surface voltages is proposed to reconstruct the distribution of electrical conductivity inside the focal plane on the basis of the temperature dependent electrical impedance of tissues. In theoretical study, a comprehensive system of EIT measurement during HIFU therapy is established. With the consideration of acoustic absorption in viscous tissues, three-dimensional Helmholtz equation for HIFU is simplified into two-dimensional axisymmetric cylindrical coordinates, and the characteristics of temperature rising in the focal region are derived using Pennes bio-heat transfer equation. Then, by introducing the temperature-conductivity relation into tissues, the processing methods for electrical field and surface voltage in the focal region are constructed with constant current injection from two symmetrical electrodes. In simulation study, by applying the experimental parameters of the focused transducer, the distributions of acoustic pressure and temperature are simulated at a fixed acoustic power, and then the corresponding distributions of conductivity in the focal plane are achieved at different treatment times for centric and eccentric focusing. Furthermore, with the simulations of current density and electrical potential generated by the rotating current injection from 16 pairs of symmetrical electrodes, 32×32 voltages are detected by the 32 surface electrodes placed around the focal plane of the model. In conductivity image reconstruction, the modified Newton-Raphson (MNR) algorithm is employed to conduct iterative calculation. It shows that with the increase of HIFU treatment time, the electrical conductivity in the focal region increases accordingly and reaches a maximum value in the center due to the highest acoustic pressure and the most energy accumulation. It is proved that not only the position of the focal center, but also the conductivity distribution inside the focal region can be restored accurately by the proposed EIT based reconstruction algorithm. The favorable results demonstrate the feasibility of temperature monitoring during HIFU therapy, and also provide a new method of evaluating the noninvasive efficacy and controlling the dose based on electrical impedance measurements.
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Keywords:
- high intensity focused ultrasound /
- electrical impedance tomography /
- temperature monitoring /
- surface electrode voltage
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[32] Li G Y 2011 M. S. Dissertation (Beijing:Beijing Jiaotong University) (in Chinese)[黎光宇2011硕士学位论文(北京:北京交通大学)]
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[34] Lin M F 2014 M. S. Dissertation (Nanjing:Nanjing University of Posts and Telecommunications) (in Chinese)[林明锋2014硕士学位论文(南京:南京邮电大学)]
[35] Zhang L 2014 Electr. Design Eng. 22 184(in Chinese)[张丽2014电子设计工程22 184]
[36] Qin S L 2000 Computat. Phys. 17 314(in Chinese)[秦世伦2000计算物理17 314]
[37] Ma H, Wang G 2009 COMSOL Multiphysics Basic Operation Guide and FAQ (Beijing:China Communications Press) (in Chinese)[马慧, 王刚2009 COMSOL Multiphysics基本操作指南和常见问题解答(北京:人民交通出版社)]
[38] Hu B, Jiang L X, Huang Y 2006 Tech. Acoust. 25 613(in English)[胡兵, 姜立新, 黄瑛2006声学技术25 613]
[39] Li G 2013 M. S. Dissertation (Tianjing:Tianjing University of Science and Technology) (in Chinese)[黎鸽2013硕士学位论文(天津:天津科技大学)]
[40] Bessonova O, Wilkens V 2013 J. Acoust. Soc. Amer. 134 4213
[41] Sun J M, Yu J, Guo X S, Zhang D 2013 Acta Phys. Sin. 62 054301 (in Chinese)[孙健明, 于洁, 郭霞生, 章东2013 62 054301]
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[1] Hutchinson L 2011 Nat. Rev. Clin. Oncol. 8 385
[2] Kennedy J E 2005 Nat. Rev. Canc. 5 321
[3] Qian S Y, Wang H Z 2001 Acta Phys. Sin. 50 501 (in Chinese)[钱盛友, 王鸿樟2001 50 501]
[4] Gavrilov L R 2013 J. Acoust. Soc. Amer. 133 4348
[5] Jiang L X, Hu B 2006 Tech. Acoust. 25 43(in Chinese)[姜立新, 胡兵2006声学技术25 43]
[6] Shen J, Shen J L, Zou J Z 2007 J. Ultrasound Clin. Med. 9 486(in Chinese)[沈洁, 申俊玲, 邹建中2007临床超声医学杂志9 486]
[7] Ye G, Smith P P, Noble J A 2010 Ultrasound Med. Biol. 36 234
[8] Daniels M J, Varghese T, Madsen E L, Zagzebski J A 2007 Phys. Med. Biol. 52 4827
[9] Fan T B, Zhang D, Zhang Z, Ma Y, Gong X F 2008 Chin. Phys. B 17 3372
[10] Anand A, Kaczkowski P J 2004 J. Acoust. Soc. Amer. 115 2490
[11] Ma Y, Zhang D, Gong X F, Liu X Z, Ma Q Y, Qiu Y Y 2007 Chin. Phys. 16 2745
[12] Fan L Z, Luo F, Yu D Y, Liu X T, Zhang J, Xie M X 2005 Clin. J. Med. Instru. 29 115(in Chinese)[范良志, 罗飞, 喻道远, 刘夏天, 张静, 谢明星2005中国医疗器械杂志29 115]
[13] Gabriel C, Peyman A, Grant E H 2009 Phys. Med. Biol. 54 4863
[14] Zurbuchen U, Holmer C, Lehmann K S, Stein T, Roggan A, Seifarth C, Buhr H J, Ritz J P 2010 Int. J. Hyperthermia 26 26
[15] Griffiths H, Ahmed A 1987 Clin. Phys. Physiol. Meas. 8 147
[16] Cai H, You F S, Shi X T, Fu F, Liu R G, Tang C, Dong X Z 2010 Chin. Med. Equip. J. 31 8(in Chinese)[蔡华, 尤富生, 史学涛, 付峰, 刘锐岗, 汤池, 董秀珍2010医疗卫生装备31 8]
[17] Su H D, Guo G P, Ma Q Y, Tu J, Zhang D 2017 Chin. Phys. B 26 054302
[18] Li K Q 2015 M. S. Dissertation (Nanjing:Nanjing University of Posts and Telecommunications) (in Chinese)[李凯强2015硕士学位论文(南京:南京邮电大学)]
[19] Xu G X 2004 Ph. D. Dissertation (Chongqing:Chongqing University) (in Chinese)[徐管鑫2004博士学位论文(重庆:重庆大学)]
[20] Zhang L 2013 Ph. D. Dissertation (Nanjing:Nanjing University of Science and Technology) (in Chinese)[张丽2013博士学位论文(南京:南京理工大学)]
[21] Curra F P, Mourad P D, Khokhlova V A, Crum L A 2000 IEEE Trans. Ultrason. Ferroelect. Freq. Control 47 1077
[22] Soneson J E, Myers M R 2010 IEEE Trans. Ultrason. Ferroelect. Freq. Control 57 2450
[23] Myers M R, Soneson J E 2009 J. Acoust. Soc. Amer. 126 425
[24] Soneson J E, Myers M R 2007 J. Acoust. Soc. Amer. 122 2526
[25] Du G H, Zhu Z M, Gong X F 2012 Fundamentals of Acoustics (Nanjing:Nanjing University Press) pp292-305(in Chinese)[杜功焕, 朱哲民, 龚秀芬2012声学基础(南京:南京大学出版社)第292–305页]
[26] Cheng J C 2013 Principles of Acoustics (Beijing:Science Press) pp571-576(in Chinese)[程建春2013声学原理(北京:科学出版社)第571–576页]
[27] Wan M X, Zong J Y, Wang S P 2010 Biomedical Ultrasound (Beijing:Science Press) pp649-669(in Chinese)[万明习, 宗瑜瑾, 王素品2010生物医学超声学(北京:科学出版社)第649–669页]
[28] Zhang D, Guo X S, Ma Q Y, Tu J 2014 Fundamentals of Medical Ultrasound (Beijing:Science Press) pp415-418(in Chinese)[章东, 郭霞生, 马青玉, 屠娟2014医学超声基础(北京:科学出版社)第415–418页]
[29] Pennes H H 1948 J. Appl. Physiol. 1 93
[30] Chen Z J, Zhou G L 2014 Inform. Commun. 4 36(in Chinese)[陈姝君, 周广丽2014信息通信4 36]
[31] Chen Z J 2008 Ph. D. Dissertation (Nanjing:Nanjing University of Science and Technology) (in Chinese)[陈姝君2008博士学位论文(南京:南京理工大学)]
[32] Li G Y 2011 M. S. Dissertation (Beijing:Beijing Jiaotong University) (in Chinese)[黎光宇2011硕士学位论文(北京:北京交通大学)]
[33] Xu G Z, Li Y, Yang S, Wu H L, Zhang S, Zhang J J 2010 Biomedical Electrical Impedance Tomography (Beijing:Machinery Industry Press) pp33-34(in Chinese)[徐桂芝, 李颖, 杨硕, 吴焕丽, 张帅, 张剑军2010生物医学电阻抗成像技术(北京:机械工业出版社)第33–34页]
[34] Lin M F 2014 M. S. Dissertation (Nanjing:Nanjing University of Posts and Telecommunications) (in Chinese)[林明锋2014硕士学位论文(南京:南京邮电大学)]
[35] Zhang L 2014 Electr. Design Eng. 22 184(in Chinese)[张丽2014电子设计工程22 184]
[36] Qin S L 2000 Computat. Phys. 17 314(in Chinese)[秦世伦2000计算物理17 314]
[37] Ma H, Wang G 2009 COMSOL Multiphysics Basic Operation Guide and FAQ (Beijing:China Communications Press) (in Chinese)[马慧, 王刚2009 COMSOL Multiphysics基本操作指南和常见问题解答(北京:人民交通出版社)]
[38] Hu B, Jiang L X, Huang Y 2006 Tech. Acoust. 25 613(in English)[胡兵, 姜立新, 黄瑛2006声学技术25 613]
[39] Li G 2013 M. S. Dissertation (Tianjing:Tianjing University of Science and Technology) (in Chinese)[黎鸽2013硕士学位论文(天津:天津科技大学)]
[40] Bessonova O, Wilkens V 2013 J. Acoust. Soc. Amer. 134 4213
[41] Sun J M, Yu J, Guo X S, Zhang D 2013 Acta Phys. Sin. 62 054301 (in Chinese)[孙健明, 于洁, 郭霞生, 章东2013 62 054301]
[42] Chen T, Fan T, Zhang W, Qiu Y Y, Tu J, Guo X S, Zhang D 2014 J. Appl. Phys. 115 114902
[43] Chen T 2014 Ph. D. Dissertation (Nanjing:Nanjing University) (in Chinese)[陈涛2014博士学位论文(南京:南京大学)]
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