Could the heat sink effect of blood flow inside large vessels protect the vessel wall from thermal damage during RF-assisted surgical resection?

Purpose: To assess by means of computer simulations whether the heat sink effect inside a large vessel (portal vein) could protect the vessel wall from thermal damage close to an internally cooled electrode during radiofrequency (RF)-assisted resection. Methods: First, in vivo experiments were conducted to validate the computational model by comparing the experimental and computational thermal lesion shapes created around the vessels. Computer simulations were then carried out to study the effect of different factors such as device-tissue contact, vessel position, and vessel-device distance on temperature distributions and thermal lesion shapes near a large vessel, specifically the portal vein. Results: The geometries of thermal lesions around the vessels in thein vivo experiments were in agreement with the computer results. The thermal lesion shape created around the portal vein was significantly modified by the heat sink effect in all the cases considered. Thermal damage to the portal vein wall was inversely related to the vessel-device distance. It was also more pronounced when the device-tissue contact surface was reduced or when the vessel was parallel to the device or perpendicular to its distal end (blade zone), the vessel wall being damaged at distances less than 4.25 mm. Conclusions: The computational findings suggest that the heat sink effect could protect the portal vein wall for distances equal to or greater than 5 mm, regardless of its position and distance with respect to the RF-based device. © 2014 American Association of Physicists in Medicine.This work received financial support from the Spanish "Plan Nacional de I+D+I del Ministerio de Ciencia e Innovacion" Grant No. TEC2011-27133-C02-01 and -02, also from the Universitat Politecnica de Valencia (INNOVA11-01-5502; and PAID-06-11 Ref. 1988). A. Gonzalez-Suarez is the recipient of a Grant VALi+d (ACIF/2011/194) from the Generalitat Valenciana. E.B and F.B. declare a stock ownership in Apeiron Medical S.L. This company has a license for Patent U.S. 8.303.584, on which the device considered in this study is based. The remaining authors have no conflict of interest or financial ties to disclose.González Suárez, A.; Trujillo Guillen, M.; Burdío, F.; Andaluz, A.; Berjano, E. (2014). Could the heat sink effect of blood flow inside large vessels protect the vessel wall from thermal damage during RF-assisted surgical resection?. Medical Physics. 41(8):083301-1-83301-13. https://doi.org/10.1118/1.4890103S083301-183301-13418Poon, R. T., Fan, S. T., & Wong, J. (2005). Liver resection using a saline-linked radiofrequency dissecting sealer for transection of the liver. Journal of the American College of Surgeons, 200(2), 308-313. doi:10.1016/j.jamcollsurg.2004.10.008Burdío, F., Grande, L., Berjano, E., Martinez-Serrano, M., Poves, I., Burdío, J. M., … Güemes, A. (2010). 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Saline‐enhanced RF ablation on a cholangiocarcinoma: a numerical simulation. COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 31(4), 1055-1066. doi:10.1108/03321641211227302Doss, J. D. (1982). Calculation of electric fields in conductive media. Medical Physics, 9(4), 566-573. doi:10.1118/1.595107Haemmerich, D., Wright, A. W., Mahvi, D. M., Lee, F. T., & Webster, J. G. (2003). Hepatic bipolar radiofrequency ablation creates coagulation zones close to blood vessels: A finite element study. Medical & Biological Engineering & Computing, 41(3), 317-323. doi:10.1007/bf02348437Berjano, E. J., Burdío, F., Navarro, A. C., Burdío, J. M., Güemes, A., Aldana, O., … Gregorio, M. A. de. (2006). Improved perfusion system for bipolar radiofrequency ablation of liver: preliminary findings from a computer modeling study. Physiological Measurement, 27(10), N55-N66. doi:10.1088/0967-3334/27/10/n03Burdío, F., Berjano, E. J., Navarro, A., Burdío, J. M., Grande, L., Gonzalez, A., … Lequerica, J. L. (2009). Research and development of a new RF-assisted device for bloodless rapid transection of the liver: Computational modeling and in vivo experiments. BioMedical Engineering OnLine, 8(1), 6. doi:10.1186/1475-925x-8-6Modelling in Medicine and Biology VI. (2005). doi:10.2495/bio05Haemmerich, D., Chachati, L., Wright, A. S., Mahvi, D. M., Lee, F. T., & Webster, J. G. (2003). Hepatic radiofrequency ablation with internally cooled probes: effect of coolant temperature on lesion size. IEEE Transactions on Biomedical Engineering, 50(4), 493-500. doi:10.1109/tbme.2003.809488Berjano, E., & d’ Avila, A. (2013). Lumped Element Electrical Model based on Three Resistors for Electrical Impedance in Radiofrequency Cardiac Ablation: Estimations from Analytical Calculations and Clinical Data. The Open Biomedical Engineering Journal, 7(1), 62-70. doi:10.2174/1874120720130603001Hannesson, P., Stridbeck, H., Lundstedt, C., Andren-Sandberg, Å., & Ihse, I. (1995). Intravascular Ultrasound of the Portal Vein — Normal Anatomy. Acta Radiologica, 36(4), 388-392. doi:10.3109/02841859509173394Chen, X., & Saidel, G. M. (2008). Mathematical Modeling of Thermal Ablation in Tissue Surrounding a Large Vessel. Journal of Biomechanical Engineering, 131(1). doi:10.1115/1.2965374T. Peng D. O'Neill S. Payne Mathematical study of the effects of different intrahepatic cooling on thermal ablation zones 2011CIONI, G., D’ALIMONTE, P., CRISTANI, A., VENTURA, P., ABBATI, G., TINCANI, E., … VENTURA, E. (1992). Duplex-Doppler assessment of cirrhosis in patients with chronic compensated liver disease. Journal of Gastroenterology and Hepatology, 7(4), 382-384. doi:10.1111/j.1440-1746.1992.tb01003.xRíos, J. S., Zalabardo, J. M. S., Burdio, F., Berjano, E., Moros, M., Gonzalez, A., … Güemes, A. (2011). Single Instrument for Hemostatic Control in Laparoscopic Partial Nephrectomy in a Porcine Model Without Renal Vascular Clamping. Journal of Endourology, 25(6), 1005-1011. doi:10.1089/end.2010.0557Dos Santos, I., Haemmerich, D., Pinheiro, C., & da Rocha, A. (2008). Effect of variable heat transfer coefficient on tissue temperature next to a large vessel during radiofrequency tumor ablation. BioMedical Engineering OnLine, 7(1), 21. doi:10.1186/1475-925x-7-21Consiglieri, L., Santos, I. dos, & Haemmerich, D. (2003). Theoretical analysis of the heat convection coefficient in large vessels and the significance for thermal ablative therapies. Physics in Medicine and Biology, 48(24), 4125-4134. doi:10.1088/0031-9155/48/24/010Consiglieri, L. (2012). Continuum Models for the Cooling Effect of Blood Flow on Thermal Ablation Techniques. International Journal of Thermophysics, 33(5), 864-884. doi:10.1007/s10765-012-1194-0Huang, H.-W. (2013). 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Computational Models and Experimentation for Radiofrequency-based Ablative Techniques

Las técnicas ablativas basadas en energía por radiofrecuencia (RF) se emplean con el fin de lograr un calentamiento seguro y localizado en el tejido biológico. En los últimos años ha habido un rápido crecimiento en el número de nuevos procedimientos médicos que hacen uso de dichas técnicas, lo cual ha ido acompañado de la aparición de nuevos diseños de electrodos y protocolos de aplicación de energía. Sin embargo, existen todavía muchas incógnitas sobre el verdadero comportamiento electro-térmico de los aplicadores de energía, así como de la interacción energía-tejido en aplicaciones concretas. El principal propósito de esta Tesis Doctoral es adquirir un mejor conocimiento de los fenómenos eléctricos y térmicos involucrados en los procesos de calentamiento de tejidos biológicos mediante corrientes de RF. Esto permitirá, por un lado, mejorar la eficacia y seguridad de las técnicas actualmente empleadas en la clínica en campos tan diferentes como la cirugía cardiaca, oncológica o dermatológica; y por otro, sugerir mejoras tecnológicas para el diseño de nuevos aplicadores. La Tesis Doctoral combina dos metodologías ampliamente utilizadas en el campo de la Ingeniería Biomédica, como son el modelado computacional (matemático) y la experimentación (ex vivo e in vivo). En cuanto al área cardiaca, la investigación se ha centrado, por una parte, en mejorar la ablación intraoperatoria de la fibrilación auricular por aproximación epicárdica, es decir, susceptible de ser realizada de forma mínimamente invasiva. Para ello, se ha estudiado mediante modelos matemáticos un sistema de medida de la impedancia epicárdica como método de valoración de la cantidad de grasa previo a la ablación. Por otra parte, se ha estudiado cómo mejorar la ablación de la pared ventricular por aproximación endocárdica-endocárdica (septo interventricular) y endocárdica-epicárdica (pared libre del ventrículo). Con este objetivo, se han comparado mediante modelado por computador la eficacia de los modos de ablación bipolar y unipolar en términos de la transmuralidad de la lesión en la pared ventricular. En lo que respecta al área de cirugía oncológica, la investigación se ha centrado en la resección hepática asistida por RF. Las técnicas de calentamiento por RF deberían ser capaces de minimizar el sangrado intraoperatorio y sellar vasos y ductos mediante la creación de una necrosis coagulativa por calentamiento. Si este calentamiento se produce en las cercanías de grandes vasos, existe un problema potencial de daño a la pared de dicho vaso. En este sentido, se ha evaluado con modelos matemáticos y experimentación in vivo si el efecto del flujo de sangre dentro de un gran vaso es capaz de proteger térmicamente su pared cuando se realiza una resección asistida por RF en sus cercanías. Además, se ha realizado un estudio computacional y experimental ex vivo e in vivo del comportamiento electro-térmico de aplicadores de RF bipolares internamente refrigerados, puesto que representan una opción más segura frente a los monopolares en la medida en que las corrientes de RF fluyen casi exclusivamente por el tejido biológico situado entre ambos electrodos. Respecto al área dermatológica, la investigación se ha centrado en mejorar el tratamiento de enfermedades o desórdenes del tejido subcutáneo (tales como lipomatosis, lipedema, enfermedad de Madelung y celulitis) mediante el estudio teórico de la dosimetría correcta en cada caso. Para ello, se han evaluado los efectos eléctricos, térmicos y termo-elásticos de dos estructuras diferentes de tejido subcutáneo durante el calentamiento por RF, y se ha cuantificado el daño térmico producido en ambas estructuras tras dicho calentamientoGonzález Suárez, A. (2014). Computational Models and Experimentation for Radiofrequency-based Ablative Techniques [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36502TESI

Surgical Cutting and Ablation by Energy Based Devices: Principles and Applications

Advances in ultrasound, radiofrequency, and water jet systems are facilitating their increased use in new medical ablation or cutting applications in fields as diverse as cardiology, orthopaedics, ophthalmology, dermatology, oncology and neurosurgery. These methods involve controlled alteration or destruction of tissues via the application of thermal, electrical or kinetic energy. This market segment is characterised by advanced devices capable of heating or cooling tissue from -200°C to 400°C, or inducing vibrations of up to 60 kHz to cause tissue damage. The medical conditions targeted primarily pertain to chronic and age-related diseases, but elective and cosmetic procedures are also addressed. Medical ablation research has the potential for significant clinical and commercial gains. New capabilities in terms of tissue ablation technologies can enable new medical procedures, affording opportunities for design creativity and entrepreneurship and ultimately delivering a health dividend

An Electrode Array for Limiting Blood Loss During Liver Resection: Optimization via Mathematical Modeling

Liver resection is the current standard treatment for patients with both primary and metastatic liver cancer. The principal causes of morbidity and mortality after liver resection are related to blood loss (typically between 0.5 and 1 L), especially in cases where transfusion is required. Blood transfusions have been correlated with decreased long-term survival, increased risk of perioperative mortality and complications. The goal of this study was to evaluate different designs of a radiofrequency (RF) electrode array for use during liver resection. The purpose of this electrode array is to coagulate a slice of tissue including large vessels before resecting along that plane, thereby significantly reducing blood loss. Finite Element Method models were created to evaluate monopolar and bipolar power application, needle and blade shaped electrodes, as well as different electrode distances. Electric current density, temperature distribution, and coagulation zone sizes were measured. The best performance was achieved with a design of blade shaped electrodes (5 × 0.1 mm cross section) spaced 1.5 cm apart. The electrodes have power applied in bipolar mode to two adjacent electrodes, then switched sequentially in short intervals between electrode pairs to rapidly heat the tissue slice. This device produces a ~1.5 cm wide coagulation zone, with temperatures over 97 ºC throughout the tissue slice within 3 min, and may facilitate coagulation of large vessels

Comparison of two radiofrequency-based hemostatic devices: saline-linked bipolar vs. cooled-electrode monopolar

[EN] Purpose To characterize the coagulation zones created by two radiofrequency (RF)-based hemostatic devices: one comprised an internally cooled monopolar electrode and the other comprised externally irrigated bipolar electrodes (saline-linked). Materials and methods RF-induced coagulation zones were created on ex vivo and in vivo porcine models. Computer modeling was used to determine the RF power distribution in the saline-linked device. Results Both external (irrigation) and internal cooling effectively prevented tissue sticking. Under ex vivo conditions in 'painting' application mode, coagulation depth increased with the applied power: 2.8 - 5.6 mm with the 3-mm monopolar electrode, 1.6 - 6.0 mm with the 5-mm monopolar electrode and 0.6 - 3.2 mm with the saline-linked bipolar electrodes. Under in vivo conditions and using spot applications, the 3-mm monopolar electrode created coagulation zones of similar depth to the saline-linked bipolar electrodes (around 3 mm), while the 5-mm monopolar electrode created deeper coagulations (4.5 - 6 mm) with less incidence of popping. The presence of saline around the saline-linked bipolar electrodes meant that a significant percentage of RF power (50 - 80%) was dissipated by heating in the saline layer. Coagulation zones were histologically similar for all the tested devices. Conclusions Both external (irrigation) and internal cooling in hemostatic RF devices effectively prevent tissue sticking and create similar coagulation zones from a histological point of view. Overall, saline-linked bipolar electrodes tend to create shallower coagulations than those created with an internally cooled monopolar electrode.Spanish Ministerio de Ciencia, Innovacion y Universidades MCIN/AEI/10.13039/501100011033 [Grants RTI2018-094357-B-C21 and RTI2018094357-B-C22], "Agencia Nacional de Promocion Cientifica y Tecnologica de Argentina" [PICT-2020-SERIEA-00457], Dr. Irastorza was the recipient of a scholarship from the Programa de Becas Externas Postdoctorales para Jovenes Investigadores del CONICET (Argentina).Moll, X.; Fondevila, D.; García-Arnás, F.; Burdio, F.; Trujillo Guillen, M.; Irastorza, RM.; Berjano, E.... (2022). Comparison of two radiofrequency-based hemostatic devices: saline-linked bipolar vs. cooled-electrode monopolar. International Journal of Hyperthermia. 39(1):1397-1407. https://doi.org/10.1080/02656736.2022.21408401397140739

The impact of radiofrequency-assisted transection on local hepatic recurrence after resection of colorectal liver metastases

Resection is the gold standard in the treatment of liver metastases from colorectal cancer. An internal cooled radiofrequency electrode was described to achieve tissue coagulation to a greater margin width. The aim of this study is to determinate if a RFassisted transection device (RFAT) has any effect on local hepatic recurrence (LHER) compared to conventional technologies. A study population of 103 patients who had undergone a hepatic surgical resection was retrospectively analysed. Patients were classified into two groups according to the device used: a RF-assisted device (RFAT group; n=45) and standard conventional devices (control group; n=58). LHER was defined as any growing or enhancing tumour in the margin of hepatic resection during follow-up. Cox proportional models were constructed and variables were eliminated only if p>0.20 to protect against residual confounding. To assess the stability of Cox’s regression model and its internal validity, a bootstrap investigation was also performed. Baseline and operative characteristics were similar in both groups. With a mean followup of 28.5 months (range 2-106), in patients with positive margins, we demonstrated 0% of LHER in RFAT vs. 27% in control group (p=0.032). In the multivariate analysis five factors demonstrated significant influence on the final model of LHER: RFAT group, size of the largest metastases, number of resected metastases, positive margin and usage of Pringle-manoeuvre. This study suggests that parenchymal transection using a RFAT able to create deep thermal lesions may reduce LHER especially in case of margin invasion during transectionQuesada-Diez, R.; Moreno, A.; Poves, I.; Berjano, E.; Grande, L.; Burdío Pinilla, F. (2017). The impact of radiofrequency-assisted transection on local hepatic recurrence after resection of colorectal liver metastases. Surgical Oncology. 26(3):229-235. doi:10.1016/j.suronc.2017.04.004S22923526

Feasibility study of an internally cooled bipolar applicator for RF coagulation of hepatic tissue: Experimental and computational study

Purpose: To study the capacity of an internally cooled radiofrequency (RF) bipolar applicator to create sufficiently deep thermal lesions in hepatic tissue. Materials and methods: Three complementary methodologies were employed to check the electrical and thermal behaviour of the applicator under test. The experimental studies were based on excised bovine (ex vivo study) and porcine liver (in vivo study) and the theoretical models were solved by means of the finite element method (FEM). Results: Experimental and computational results showed good agreement in terms of impedance progress and lesion depth (4 and 4.5 mm respectively for ex vivo conditions, and approximately 7 and 9 mm respectively for in vivo conditions), although the lesion widths were overestimated by the computer simulations. This could have been due to the method used to assess the thermal lesions; the experimental lesions were assessed by the white coagulation zone, whereas the tissue damage function was used to assess the computational lesions. Conclusions: The experimental results suggest that this applicator could create in vivo lesions to a depth of around 7mm. It was also observed that the thermal lesion is mainly confined to the area between both electrodes, which would allow lesion width to be controlled by selecting a specific applicator design. The comparison between the experimental and computational results suggests that the theoretical model could be usefully applied in further studies of the performance of this device. © 2012 Informa UK Ltd All rights reserved.This work received financial support from the Spanish Plan Nacional de I+D+I del Ministerio de Ciencia e Innovacion TEC2011-27133-C02-(01 and 02), from Universitat Politecnica de Valencia (INNOVA11-01-5502; and PAID-06-11 Ref. 1988). A. Gonzalez-Suarez is the recipient of grant VaLi+D (ACIF/2011/194) from the Generalitat Valenciana. The proof-reading of this paper was funded by the Universitat Politecnica de Valencia, Spain. The authors alone are responsible for the content and writing of the paper.González Suárez, A.; Trujillo Guillen, M.; Burdío Pinilla, F.; Andaluz Martínez, AM.; Berjano Zanón, E. (2012). Feasibility study of an internally cooled bipolar applicator for RF coagulation of hepatic tissue: Experimental and computational study. International Journal of Hyperthermia. 28(7):663-673. https://doi.org/10.3109/02656736.2012.716900S663673287Topp, S. A., McClurken, M., Lipson, D., Upadhya, G. A., Ritter, J. H., Linehan, D., & Strasberg, S. M. (2004). Saline-Linked Surface Radiofrequency Ablation. Annals of Surgery, 239(4), 518-527. doi:10.1097/01.sla.0000118927.83650.a4Gnerlich, J. L., Ritter, J. H., Linehan, D. C., Hawkins, W. G., & Strasberg, S. M. (2009). Saline-Linked Surface Radiofrequency Ablation. 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Radiofrequency pancreatic ablation and section of the main pancreatic duct does not lead to necrotizing pancreatitis

[EN] Objective: Determine whether Radiofrequency ablation (RFA) of the pancreas and subsequent transection of the main pancreatic duct may avoid the risk of both necrotizing pancreatitis and postoperative pancreatic fistula (POPF) formation. Methods: Thirty-two rats were subjected to RFA and section of the pancreas over their portal vein. Animals were killed at 3, 7, 15 and 21 days (Groups 0-3, respectively). Two additional control groups (sham operation and user manipulation only, respectively) of 15 days of postoperative period were considered. Postoperative complications, histological changes (including morphometric and immunohistochemical analysis) and incidence of POPF were evaluated. Results: A significant increase in serum amylase levels (p<0.05) on the 3rd postoperative day which return to baseline levels in the following weeks was noted in groups 0-3. Those groups showed a rapid atrophy of the distal pancreas by apoptosis with no signs of necrotizing pancreatitis or POPF. The distal pancreas in groups 1-3 compared to group 0 and control groups showed a significant increase of small islets (<1000 μm 2 ). Conclusions: The rapid acinar atrophy of the distal pancreas after RFA and section of the pancreatic ducts in this model does not lead to necrotizing pancreatitis.This research has been supported by grant TEC2011-27133-C02-02 from the Spanish Government and the European Economic Community.Quesada, R.; Burdío, F.; Iglesias, M.; Dorcaratto, D.; Cáceres, M.; Andaluz, A.; Poves, I.... (2014). Radiofrequency pancreatic ablation and section of the main pancreatic duct does not lead to necrotizing pancreatitis. Pancreas. 43(6):931-937. doi:10.1097/MPA.0000000000000156S93193743

Interistitial laser immunotherapy for treatment of metastatic cancer.

Cancer is one of the leading causes of death in the world. Although widely used, currently available cancer treatment modalities such as surgery, chemotherapy and radiation have limited effects in curing the disease and prolonging the life oflate-stage cancer patients. A novel therapy, laser immunotherapy (LIT) has been developed for the treatment of late-stage metastatic cancers. LIT uses laser light to kill cancer cells and a non-toxic immunoadjuvant, glycated chitosan (GC) to stimulate the host immune system. It fights against residual tumor cells, as well as metastases at distant sites. LIT is a combination of photothermal therapy and immunotherapy. The current application of LIT is non-invasive, using light to penetrate surface skin tissue to treat underlying tumor cells. Modifications to the LIT treatment are necessary to effectively treat patients with pigmented skin and deep tumors. Thus, interstitial laser immunotherapy (ILIT), using an invasive laser irradiation approach, is proposed. The present study is designed to investigate the effectiveness of ILIT using an 805-nm laser. DMBA-4 metastatic mammary tumor cells line in Wistar Furth female rats was used. Irradiation of rat tumors was performed using an interstitial fiber with a cylindrical diffuser. The temperature distribution inside the target tumor tissue, an important factor affecting the outcome of ILIT, was monitored with a thermocouple by inserting needle probes into the tissue around the cylindrical diffuser duringlaser irradiation. To measure the three-dimensional temperature distribution in the target tissue, the proton resonance frequency (PRF) method was conducted using a 7.1-Tesla magnetic resonance imager. Our results showed that the temperature distribution in tissue depended on laser power and irradiation duration. The temperature inside the target tumor varied with the distance from the laser diffuser tip. Thermal damage to the tumor was examined using triphenyltetrazoium chloride (TTC) staining as well as hematoxolin and erosion (H&E) staining. Animal survival as well as tumor size over time was monitored. Our results indicate that ILIT had a much greater thermal impact on target tumors with less surface damage than LIT. The survival study also indicates that ILIT has better potential for treating metastases and deep tumors, while having fewer side effects than LIT