Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models

Purpose: To assess whether tailoring the Kp and Ki values of a proportional-integral (PI) controller during radiofrequency (RF) cardiac ablation could be advantageous from the point of view of the dynamic behaviour of the controller, in particular, whether control action could be speeded up and larger lesions obtained. Methods: Theoretical models were built and solved by the finite element method. RF cardiac ablations were simulated with temperature controlled at 55 degrees C. Specific PI controllers were implemented with Kp and Ki parameters adapted to cases with different tissue values (specific heat, thermal conductivity and electrical conductivity) electrode-tissue contact characteristics (insertion depth, cooling effect of circulating blood) and electrode characteristics (size, location and arrangement of the temperature sensor in the electrode). Results: The lesion dimensions and T(max) remained almost unchanged when the specific PI controller was used instead of one tuned for the standard case: T(max) varied less than 1.9 degrees C, lesion width less than 0.2 mm, and lesion depth less than 0.3 mm. As expected, we did observe a direct logical relationship between the response time of each controller and the transient value of electrode temperature. Conclusion: The results suggest that a PI controller designed for a standard case (such as that described in this study), could offer benefits under different tissue conditions, electrode-tissue contact, and electrode characteristics.This work received financial support from the Spanish 'Plan Nacional de I+D+I del Ministerio de Ciencia e Innovacion' Grant no. TEC2008-01369/TEC and FEDER Project MTM2010-14909. The translation of this paper was funded by the Universitat Politecnica de Valencia, Spain. The authors alone are responsible for the content and writing of the paperAlba Martínez, J.; Trujillo Guillen, M.; Blasco Giménez, RM.; Berjano Zanón, E. (2011). Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models. International Journal of Hyperthermia. 27(6):539-548. https://doi.org/10.3109/02656736.2011.586665S539548276Gaita, F., Caponi, D., Pianelli, M., Scaglione, M., Toso, E., Cesarani, F., … Leclercq, J. F. (2010). Radiofrequency Catheter Ablation of Atrial Fibrillation: A Cause of Silent Thromboembolism? Circulation, 122(17), 1667-1673. doi:10.1161/circulationaha.110.937953Anfinsen, O.-G., Aass, H., Kongsgaard, E., Foerster, A., Scott, H., & Amlie, J. P. (1999). Journal of Interventional Cardiac Electrophysiology, 3(4), 343-351. doi:10.1023/a:1009840004782PETERSEN, H. H., CHEN, X., PIETERSEN, A., SVENDSEN, J. H., & HAUNSO, S. (2000). Tissue Temperatures and Lesion Size During Irrigated Tip Catheter Radiofrequency Ablation: An In Vitro Comparison of Temperature-Controlled Irrigated Tip Ablation, Power-Controlled Irrigated Tip Ablation, and Standard Temperature-Controlled Ablation. Pacing and Clinical Electrophysiology, 23(1), 8-17. doi:10.1111/j.1540-8159.2000.tb00644.xTungjitkusolmun, S., Woo, E. J., Cao, H., Tsai, J. Z., Vorperian, V. R., & Webster, J. G. (2000). Thermal—electrical finite element modelling for radio frequency cardiac ablation: Effects of changes in myocardial properties. Medical & Biological Engineering & Computing, 38(5), 562-568. doi:10.1007/bf02345754Lai, Y.-C., Choy, Y. B., Haemmerich, D., Vorperian, V. R., & Webster, J. G. (2004). Lesion Size Estimator of Cardiac Radiofrequency Ablation at Different Common Locations With Different Tip Temperatures. IEEE Transactions on Biomedical Engineering, 51(10), 1859-1864. doi:10.1109/tbme.2004.831529Jain, M. K., & Wolf, P. D. (1999). Temperature-controlled and constant-power radio-frequency ablation: what affects lesion growth? IEEE Transactions on Biomedical Engineering, 46(12), 1405-1412. doi:10.1109/10.804568Panescu, D., Whayne, J. G., Fleischman, S. D., Mirotznik, M. S., Swanson, D. K., & Webster, J. G. (1995). Three-dimensional finite element analysis of current density and temperature distributions during radio-frequency ablation. IEEE Transactions on Biomedical Engineering, 42(9), 879-890. doi:10.1109/10.412649Hong Cao, Vorperian, V. R., Tungjitkusolmun, S., Jan-Zern Tsai, Haemmerich, D., Young Bin Choy, & Webster, J. G. (2001). Flow effect on lesion formation in RF cardiac catheter ablation. IEEE Transactions on Biomedical Engineering, 48(4), 425-433. doi:10.1109/10.915708Tungjitkusolmun, S., Vorperian, V. R., Bhavaraju, N., Cao, H., Tsai, J.-Z., & Webster, J. G. (2001). Guidelines for predicting lesion size at common endocardial locations during radio-frequency ablation. IEEE Transactions on Biomedical Engineering, 48(2), 194-201. doi:10.1109/10.909640Schutt, D., Berjano, E. J., & Haemmerich, D. (2009). Effect of electrode thermal conductivity in cardiac radiofrequency catheter ablation: A computational modeling study. International Journal of Hyperthermia, 25(2), 99-107. doi:10.1080/02656730802563051Langberg, J. J., Calkins, H., el-Atassi, R., Borganelli, M., Leon, A., Kalbfleisch, S. J., & Morady, F. (1992). Temperature monitoring during radiofrequency catheter ablation of accessory pathways. Circulation, 86(5), 1469-1474. doi:10.1161/01.cir.86.5.1469Calkins, H., Prystowsky, E., Carlson, M., Klein, L. S., Saul, J. P., & Gillette, P. (1994). Temperature monitoring during radiofrequency catheter ablation procedures using closed loop control. Atakr Multicenter Investigators Group. Circulation, 90(3), 1279-1286. doi:10.1161/01.cir.90.3.1279Lennox CD, Temperature controlled RF coagulation. Patent number: 5.122.137 Hudson NHEdwards SD, Stern RA, Electrode and associated system using thermally insulated temperature sensing elements. Patent number: US Patent 5,456,682Panescu D, Fleischman SD, Whayne JG, Swanson DK, (EP Technology. Effects of temperature sensor placement on performance of temperature-controlled ablation. IEEE 17th Annual Conference, Engineering in Medicine and Biology Society, Montreal, Canada (1995)BLOUIN, L. T., MARCUS, F. I., & LAMPE, L. (1991). Assessment of Effects of a Radiofrequency Energy Field and Thermistor Location in an Electrode Catheter on the Accuracy of Temperature Measurement. Pacing and Clinical Electrophysiology, 14(5), 807-813. doi:10.1111/j.1540-8159.1991.tb04111.xBerjano, E. J. (2006). BioMedical Engineering OnLine, 5(1), 24. doi:10.1186/1475-925x-5-24Bhavaraju, N. C., Cao, H., Yuan, D. Y., Valvano, J. W., & Webster, J. G. (2001). Measurement of directional thermal properties of biomaterials. IEEE Transactions on Biomedical Engineering, 48(2), 261-267. doi:10.1109/10.909647Hong Cao, Tungjitkusolmun, S., Young Bin Choy, Jang-Zern Tsai, Vorperian, V. R., & Webster, J. G. (2002). Using electrical impedance to predict catheter-endocardial contact during RF cardiac ablation. IEEE Transactions on Biomedical Engineering, 49(3), 247-253. doi:10.1109/10.983459PETERSEN, H. H., & SVENDSEN, J. H. (2003). Can Lesion Size During Radiofrequency Ablation Be Predicted By the Temperature Rise to a Low Power Test Pulse in Vitro? Pacing and Clinical Electrophysiology, 26(8), 1653-1659. doi:10.1046/j.1460-9592.2003.t01-1-00248.xLANGBERG, J. J., LEE, M. A., CHIN, M. C., & ROSENQVIST, M. (1990). Radiofrequency Catheter Ablation: The Effect of Electrode Size on Lesion Volume In Vivo. Pacing and Clinical Electrophysiology, 13(10), 1242-1248. doi:10.1111/j.1540-8159.1990.tb02022.

Experimental Assessment of Time Reversal for In-Body to In-Body UWB Communications

[EN] The standard of in-body communications is limited to the use of narrowband systems. These systems are far from the high data rate connections achieved by other wireless telecommunication services today in force. The UWB frequency band has been proposed as a possible candidate for future in-body networks. However, the attenuation of body tissues at gigahertz frequencies could be a serious drawback. Experimental measurements for channel modeling are not easy to carry out, while the use of humans is practically forbidden. Sophisticated simulation tools could provide inaccurate results since they are not able to reproduce all the in-body channel conditions. Chemical solutions known as phantoms could provide a fair approximation of body tissues¿ behavior. In this work, the Time Reversal technique is assessed to increase the channel performance of in-body communications. For this task, a large volume of experimental measurements is performed at the low part of UWB spectrum (3.1-5.1 GHz) by using a highly accurate phantom-based measurement setup. This experimental setup emulates an in-body to in-body scenario, where all the nodes are implanted inside the body. Moreover, the in-body channel characteristics such as the path loss, the correlation in transmission and reception, and the reciprocity of the channel are assessed and discussed.This work was supported by the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-16) from Universitat Politecnica de Valencia and by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R), by the European FEDER funds.Andreu-Estellés, C.; Garcia-Pardo, C.; Castelló-Palacios, S.; Cardona Marcet, N. (2018). Experimental Assessment of Time Reversal for In-Body to In-Body UWB Communications. Wireless Communications and Mobile Computing (Online). (8927107):1-12. https://doi.org/10.1155/2018/8927107S1128927107Fireman, Z. (2003). Diagnosing small bowel Crohn’s disease with wireless capsule endoscopy. Gut, 52(3), 390-392. doi:10.1136/gut.52.3.390Burri, H., & Senouf, D. (2009). Remote monitoring and follow-up of pacemakers and implantable cardioverter defibrillators. Europace, 11(6), 701-709. doi:10.1093/europace/eup110Scanlon, W. G., Burns, B., & Evans, N. E. (2000). Radiowave propagation from a tissue-implanted source at 418 MHz and 916.5 MHz. IEEE Transactions on Biomedical Engineering, 47(4), 527-534. doi:10.1109/10.828152Chavez-Santiago, R., Garcia-Pardo, C., Fornes-Leal, A., Valles-Lluch, A., Vermeeren, G., Joseph, W., … Cardona, N. (2015). Experimental Path Loss Models for In-Body Communications within 2.36-2.5 GHz. IEEE Journal of Biomedical and Health Informatics, 1-1. doi:10.1109/jbhi.2015.2418757Khaleghi, A., Chávez-Santiago, R., & Balasingham, I. (2010). Ultra-wideband pulse-based data communications for medical implants. IET Communications, 4(15), 1889. doi:10.1049/iet-com.2009.0692Khaleghi, A., Chávez-Santiago, R., & Balasingham, I. (2011). Ultra-wideband statistical propagation channel model for implant sensors in the human chest. IET Microwaves, Antennas & Propagation, 5(15), 1805. doi:10.1049/iet-map.2010.0537Kurup, D., Scarpello, M., Vermeeren, G., Joseph, W., Dhaenens, K., Axisa, F., … Vanfleteren, J. (2011). In-body path loss models for implants in heterogeneous human tissues using implantable slot dipole conformal flexible antennas. EURASIP Journal on Wireless Communications and Networking, 2011(1). doi:10.1186/1687-1499-2011-51Floor, P. A., Chavez-Santiago, R., Brovoll, S., Aardal, O., Bergsland, J., Grymyr, O.-J. H. N., … Balasingham, I. (2015). In-Body to On-Body Ultrawideband Propagation Model Derived From Measurements in Living Animals. IEEE Journal of Biomedical and Health Informatics, 19(3), 938-948. doi:10.1109/jbhi.2015.2417805Shimizu, Y., Anzai, D., Chavez-Santiago, R., Floor, P. A., Balasingham, I., & Wang, J. (2017). Performance Evaluation of an Ultra-Wideband Transmit Diversity in a Living Animal Experiment. IEEE Transactions on Microwave Theory and Techniques, 65(7), 2596-2606. doi:10.1109/tmtt.2017.2669039Anzai, D., Katsu, K., Chavez-Santiago, R., Wang, Q., Plettemeier, D., Wang, J., & Balasingham, I. (2014). Experimental Evaluation of Implant UWB-IR Transmission With Living Animal for Body Area Networks. IEEE Transactions on Microwave Theory and Techniques, 62(1), 183-192. doi:10.1109/tmtt.2013.2291542Chou, C.-K., Chen, G.-W., Guy, A. W., & Luk, K. H. (1984). Formulas for preparing phantom muscle tissue at various radiofrequencies. Bioelectromagnetics, 5(4), 435-441. doi:10.1002/bem.2250050408Cheung, A. Y., & Koopman, D. W. (1976). Experimental Development of Simulated Biomaterials for Dosimetry Studies of Hazardous Microwave Radiation (Short Papers). IEEE Transactions on Microwave Theory and Techniques, 24(10), 669-673. doi:10.1109/tmtt.1976.1128936YAMAMOTO, H., ZHOU, J., & KOBAYASHI, T. (2008). Ultra Wideband Electromagnetic Phantoms for Antennas and Propagation Studies. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, E91-A(11), 3173-3182. doi:10.1093/ietfec/e91-a.11.3173Lazebnik, M., Madsen, E. L., Frank, G. R., & Hagness, S. C. (2005). Tissue-mimicking phantom materials for narrowband and ultrawideband microwave applications. Physics in Medicine and Biology, 50(18), 4245-4258. doi:10.1088/0031-9155/50/18/001Yilmaz, T., Foster, R., & Hao, Y. (2014). Broadband Tissue Mimicking Phantoms and a Patch Resonator for Evaluating Noninvasive Monitoring of Blood Glucose Levels. IEEE Transactions on Antennas and Propagation, 62(6), 3064-3075. doi:10.1109/tap.2014.2313139Gezici, S., Zhi Tian, Giannakis, G. B., Kobayashi, H., Molisch, A. F., Poor, H. V., & Sahinoglu, Z. (2005). Localization via ultra-wideband radios: a look at positioning aspects for future sensor networks. IEEE Signal Processing Magazine, 22(4), 70-84. doi:10.1109/msp.2005.1458289Marinova, M., Thielens, A., Tanghe, E., Vallozzi, L., Vermeeren, G., Joseph, W., … Martens, L. (2015). Diversity Performance of Off-Body MB-OFDM UWB-MIMO. IEEE Transactions on Antennas and Propagation, 63(7), 3187-3197. doi:10.1109/tap.2015.2422353SHI, J., ANZAI, D., & WANG, J. (2012). Channel Modeling and Performance Analysis of Diversity Reception for Implant UWB Wireless Link. IEICE Transactions on Communications, E95.B(10), 3197-3205. doi:10.1587/transcom.e95.b.3197Pajusco, P., & Pagani, P. (2009). On the Use of Uniform Circular Arrays for Characterizing UWB Time Reversal. IEEE Transactions on Antennas and Propagation, 57(1), 102-109. doi:10.1109/tap.2008.2009715Chavez-Santiago, R., Sayrafian-Pour, K., Khaleghi, A., Takizawa, K., Wang, J., Balasingham, I., & Li, H.-B. (2013). Propagation models for IEEE 802.15.6 standardization of implant communication in body area networks. IEEE Communications Magazine, 51(8), 80-87. doi:10.1109/mcom.2013.6576343Andreu, C., Castello-Palacios, S., Garcia-Pardo, C., Fornes-Leal, A., Valles-Lluch, A., & Cardona, N. (2016). Spatial In-Body Channel Characterization Using an Accurate UWB Phantom. IEEE Transactions on Microwave Theory and Techniques, 64(11), 3995-4002. doi:10.1109/tmtt.2016.2609409Pahlavan, K., & Levesque, A. H. (2005). Wireless Information Networks. doi:10.1002/0471738646Qiu, R. C., Zhou, C., Guo, N., & Zhang, J. Q. (2006). Time Reversal With MISO for Ultrawideband Communications: Experimental Results. IEEE Antennas and Wireless Propagation Letters, 5, 269-273. doi:10.1109/lawp.2006.875888Ando, H., Takizawa, K., Yoshida, T., Matsushita, K., Hirata, M., & Suzuki, T. (2016). Wireless Multichannel Neural Recording With a 128-Mbps UWB Transmitter for an Implantable Brain-Machine Interfaces. IEEE Transactions on Biomedical Circuits and Systems, 10(6), 1068-1078. doi:10.1109/tbcas.2016.251452

A computational model for real-time calculation of electric field due to transcranial magnetic stimulation in clinics

The aim of this paper is to propose an approach for an accurate and fast (real-time) computation of the electric field induced inside the whole brain volume during a transcranial magnetic stimulation (TMS) procedure. The numerical solution implements the admittance method for a discretized realistic brain model derived from Magnetic Resonance Imaging (MRI). Results are in a good agreement with those obtained using commercial codes and require much less computational time. An integration of the developed codewith neuronavigation toolswill permit real-time evaluation of the stimulated brain regions during the TMSdelivery, thus improving the efficacy of clinical applications

Improved reception of in-body signals by means of a wearable multi-antenna system

High data-rate wireless communication for in-body human implants is mainly performed in the 402-405 MHz Medical Implant Communication System band and the 2.45 GHz Industrial, Scientific and Medical band. The latter band offers larger bandwidth, enabling high-resolution live video transmission. Although in-body signal attenuation is larger, at least 29 dB more power may be transmitted in this band and the antenna efficiency for compact antennas at 2.45 GHz is also up to 10 times higher. Moreover, at the receive side, one can exploit the large surface provided by a garment by deploying multiple compact highly efficient wearable antennas, capturing the signals transmitted by the implant directly at the body surface, yielding stronger signals and reducing interference. In this paper, we implement a reliable 3.5 Mbps wearable textile multi-antenna system suitable for integration into a jacket worn by a patient, and evaluate its potential to improve the In-to-Out Body wireless link reliability by means of spatial receive diversity in a standardized measurement setup. We derive the optimal distribution and the minimum number of on-body antennas required to ensure signal levels that are large enough for real-time wireless endoscopy-capsule applications, at varying positions and orientations of the implant in the human body