Transección pancreática mediante un nuevo dispositivo asistido por radiofrecuencia en un modelo porcino de pancreatectomía distal laparoscópica : estudio de factibilidad

La morbilitat relacionada amb el desenvolupament de la fístula pancreàtica postoperatòria (FP) posteriorment a realitzar una pancreatectomia distal persisteix elevada. Hem realitzat un treball experimental per a avaluar la factibilitat de la realització de la transecció pancreàtica mitjançant un nou dispositiu assistit per radiofreqüència en un model porcí de pancreatectomia distal laparoscòpica (PDL). S'ha realitzat PDL en 10 animals avaluant com a variable principal el desenvolupament de FP i com a variables secundàries paràmetres relacionats amb l'aparició de complicacions intra o postoperatòries. Els resultats obtinguts suggereixen la factibilitat de la realització de la transecció pancreàtica mitjançant el dispositiu assistit per radiofreqüència.La morbilidad relacionada con el desarrollo de fístula pancreática postoperatoria (FP) tras realizar pancreatectomía distal persiste elevada. Hemos realizado un trabajo experimental para evaluar la factibilidad de la realización de la transección pancreática mediante un nuevo dispsitivo asistido por radiofrecuencia en un modelo porcino de pancreatectomía distal laparoscópica (PDL). Se ha realizado PDL en 10 animales evaluando como variable principal el desarrollo de FP y como variables secundarias parámetros relacionados con el desarrollo de complicaciones intra o postoperatorias. Los resultados obtenidos sugieren la factibilidad de la realización de la transección pancreática mediante el dispositivo asistido por radiofrecuencia

Impacto de la ablación por radiofrecuencia en el tratamiento de las metástasis hepáticas de cáncer colorrectal

Els avenços científics i tecnològics dels últims anys han proporcionat coneixements sobre les metàstasis hepàtiques del càncer colorrectal que es tradueix en millores dels tractaments i una disminució dels efectes secundaris derivats d'ells. Hem realitzat un estudi comparatiu a partir de la nostra base de dades confeccionada de manera prospectiva amb pacients intervinguts de metàstasis hepàtiques origen colorectal. Es van analitzar els resultats dels pacients en funció del tractament quirúrgic rebut. Un grup estava conformat per pacients amb resecció hepàtica aïllada i l'altre per pacients tractats mitjançant resecció hepàtica associada amb ablació per radiofreqüència.Los avances científicos y tecnológicos de los últimos años han proporcionado conocimientos sobre las metástasis hepáticas del cáncer colorrectal que se traducen en mejoras de los tratamientos y una disminución de los efectos secundarios derivados de ellos. Hemos realizado un estudio comparativo a partir de nuestra base de datos confeccionada de forma prospectiva con pacientes intervenidos de metástasis hepáticas origen colorrectal. Se analizaron los resultados de los pacientes en función del tratamiento quirúrgico recibido. Un grupo estaba conformado por pacientes con resección hepática aislada y el otro por pacientes tratados mediante resección hepática asociada con ablación por radiofrecuencia

Retroperitoneal Inflammatory Pseudotumor Presenting as a Pancreatic Mass

Context The inflammatory pseudotumor is a rare chronic inflammatory disease not considered as a real tumor but with a similar locally aggressive behavior. Although usually located in the lungs it may be found in other organs. Case report We present the clinical case of a 66-year-old woman diagnosed with inflammatory pseudotumor after undergoing an exploratory laparotomy due to a large non resectable abdominal mass. Preoperative abdominal CT revealed a large solid polylobulated mass involving the pancreas, duodenum, hepatic hilum and superior mesenteric artery. Percutaneous fine needle aspiration and tru-cut biopsies ruled out lymphoma but did not achieve a definitive diagnosis. CD68 antibody positivity of the surgical biopsy specimen confirmed the histiocytary origin. Ki67 antibody expression was 10%. The final diagnosis was inflammatory pseudotumor rather than malignant fibrohistiocytoma based on the features and the severity of the inflammatory component. Chemotherapy was ineffective and the patient died 25 months later because of local progression and infection of the tumoral necrotic tissue. Conclusion Although inflammatory pseudotumor is not considered to be a real tumor, its aggressive local growth is similar to that of malignant soft tissue sarcomas. The only curative option is the complete surgical resection, albeit frequent recurrence

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). A new single-instrument technique for parenchyma division and hemostasis in liver resection: a clinical feasibility study. The American Journal of Surgery, 200(6), e75-e80. doi:10.1016/j.amjsurg.2010.02.020Topp, 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.a4Tepetes, K. (2008). Risks of the radiofrequency-assisted liver resection. Journal of Surgical Oncology, 97(2), 193-193. doi:10.1002/jso.20900Marchal, F., Elias, D., Rauch, P., Zarnegar, R., Leroux, A., Stines, J., … Villemot, J. P. (2006). Prevention of Biliary Lesions That May Occur During Radiofrequency Ablation of the Liver. Annals of Surgery, 243(1), 82-88. doi:10.1097/01.sla.0000193831.39362.07Sutton, P. A., Awad, S., Perkins, A. C., & Lobo, D. N. (2010). Comparison of lateral thermal spread using monopolar and bipolar diathermy, the Harmonic Scalpel™and the Ligasure™. British Journal of Surgery, 97(3), 428-433. doi:10.1002/bjs.6901Lee, J. M., Han, J. K., Chang, J. M., Chung, S. Y., Kim, S. H., Lee, J. Y., … Choi, B. I. (2006). Radiofrequency Ablation of the Porcine Liver In Vivo: Increased Coagulation with an Internally Cooled Perfusion Electrode. Academic Radiology, 13(3), 343-352. doi:10.1016/j.acra.2005.10.020Goldberg, S. N., Grassi, C. J., Cardella, J. F., Charboneau, J. W., Dodd, G. D., Dupuy, D. E., … Silverman, S. G. (2005). Image-guided Tumor Ablation: Standardization of Terminology and Reporting Criteria. Radiology, 235(3), 728-739. doi:10.1148/radiol.2353042205Pennes, H. H. (1948). Analysis of Tissue and Arterial Blood Temperatures in the Resting Human Forearm. Journal of Applied Physiology, 1(2), 93-122. doi:10.1152/jappl.1948.1.2.93Abraham, J. P., & Sparrow, E. M. (2007). A thermal-ablation bioheat model including liquid-to-vapor phase change, pressure- and necrosis-dependent perfusion, and moisture-dependent properties. International Journal of Heat and Mass Transfer, 50(13-14), 2537-2544. doi:10.1016/j.ijheatmasstransfer.2006.11.045Jo, B., & Aksan, A. (2010). Prediction of the extent of thermal damage in the cornea during conductive keratoplasty. Journal of Thermal Biology, 35(4), 167-174. doi:10.1016/j.jtherbio.2010.02.004Berjano, E. J. (2006). BioMedical Engineering OnLine, 5(1), 24. doi:10.1186/1475-925x-5-24Zhao, G., Zhang, H.-F., Guo, X.-J., Luo, D.-W., & Gao, D.-Y. (2007). Effect of blood flow and metabolism on multidimensional heat transfer during cryosurgery. Medical Engineering & Physics, 29(2), 205-215. doi:10.1016/j.medengphy.2006.03.005T. Pätz T. Körger T. Preusser Simulation of radiofrequency ablation including water evaporation 2009Chang, I. A., & Nguyen, U. D. (2004). BioMedical Engineering OnLine, 3(1), 27. doi:10.1186/1475-925x-3-27Chang, I. A. (2010). Considerations for Thermal Injury Analysis for RF Ablation Devices~!2009-09-09~!2009-12-19~!2010-02-04~! The Open Biomedical Engineering Journal, 4(2), 3-12. doi:10.2174/1874120701004020003Tungjitkusolmun, S., Staelin, S. T., Haemmerich, D., Jang-Zern Tsai, Hong Cao, Webster, J. G., … Vorperian, V. R. (2002). Three-dimensional finite-element analyses for radio-frequency hepatic tumor ablation. IEEE Transactions on Biomedical Engineering, 49(1), 3-9. doi:10.1109/10.972834Beop-Min Kim, Jacques, S. L., Rastegar, S., Thomsen, S., & Motamedi, M. (1996). Nonlinear finite-element analysis of the role of dynamic changes in blood perfusion and optical properties in laser coagulation of tissue. IEEE Journal of Selected Topics in Quantum Electronics, 2(4), 922-933. doi:10.1109/2944.577317Antunes, C. L., Almeida, T. R. O., & Raposeiro, N. (2012). 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). Influence of blood vessel on the thermal lesion formation during radiofrequency ablation for liver tumors. Medical Physics, 40(7), 073303. doi:10.1118/1.4811135Welp, C., Siebers, S., Ermert, H., & Werner, J. (2006). Investigation of the influence of blood flow rate on large vessel cooling in hepatic radiofrequency ablation / Untersuchung des Einflusses der Blutflussgeschwindigkeit auf die Gefäßkühlung bei der Radiofrequenzablation von Lebertumoren. Biomedizinische Technik/Biomedical Engineering, 51(5_6), 337-346. doi:10.1515/bmt.2006.067Lehmann, K. S., Ritz, J. P., Valdeig, S., Knappe, V., Schenk, A., Weihusen, A., … Frericks, B. B. (2009). Ex situ quantification of the cooling effect of liver vessels on radiofrequency ablation. Langenbeck’s Archives of Surgery, 394(3), 475-481. doi:10.1007/s00423-009-0480-1Ng, K. K. C., Lam, C. M., Poon, R. T. P., Shek, T. W. H., Fan, S. T., & Wong, J. (2004). Delayed portal vein thrombosis after experimental radiofrequency ablation near the main portal vein. British Journal of Surgery, 91(5), 632-639. doi:10.1002/bjs.4500Metcalfe, M. S., Mullin, E. J., Texler, M., Berry, D. P., Dennison, A. R., & Maddern, G. J. (2007). The safety and efficacy of radiofrequency and electrolytic ablation created adjacent to large hepatic veins in a porcine model. European Journal of Surgical Oncology (EJSO), 33(5), 662-667. doi:10.1016/j.ejso.2007.02.011Bangard, C., Gossmann, A., Kasper, H. U., Hellmich, M., Fischer, J. H., Hölscher, A., … Stippel, D. L. (2006). Experimental Radiofrequency Ablation Near the Portal and the Hepatic Veins in Pigs: Differences in Efficacy of a Monopolar Ablation System. Journal of Surgical Research, 135(1), 113-119. doi:10.1016/j.jss.2006.02.026T. Kröger T. Preusser H. O. Peitgen Blood flow induced cooling effect in radio frequency ablation for hepatic carcinoma 200

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

Computer modeling of an impedance-controlled pulsing protocol for RF tumor ablation with a cooled electrode

[EN] Purpose: To develop computer models to mimic the impedance-controlled pulsing protocol implemented in radiofrequency (RF) generators used for clinical practice of radiofrequency ablation (RFA), and to assess the appropriateness of the models by comparing the computer results with those obtained in previous experimental studies.Methods: A 12-min RFA was modelled using a cooled electrode (17G, 3cm tip) inserted in hepatic tissue. The short (transverse) diameter of the coagulation zone was assessed under in vivo (with blood perfusion (BP) and considering clamping) and ex vivo (at 21 degrees C) conditions. The computer results obtained by programming voltage pulses were compared with current pulses.Results: The differences between voltage and current pulses were noticeable: using current instead of voltage allows larger coagulation zones to be created, due to the higher energy applied by current pulses. If voltage pulses are employed the model can accurately predict the number of roll-offs, although the waveform of the applied power is clearly not realistic. If current voltages are employed, the applied power waveform matches well with those reported experimentally, but there are significantly fewer roll-offs. Our computer results were overall into the ranges of experimental ones.Conclusions: The proposed models reproduce reasonably well the electrical-thermal performance and coagulation zone size obtained during an impedance-controlled pulsing protocol.This work was supported by the Spanish Plan Estatal de Investigacion, Desarrollo e Innovacion Orientada a los Retos de la Sociedad under grant number TEC2014-52383-C3-R (TEC2014-52383-C3-1-R). The authors alone are responsible for the content and writing of the paper.Trujillo Guillen, M.; Bon Corbín, J.; Rivera Ortun, MJ.; Burdio, F.; Berjano, E. (2016). Computer modeling of an impedance-controlled pulsing protocol for RF tumor ablation with a cooled electrode. International Journal of Hyperthermia. 32(8):931-939. doi:10.1080/02656736.2016.1190868S931939328Hocquelet, A., Balageas, P., Laurent, C., Blanc, J.-F., Frulio, N., Salut, C., … Trillaud, H. (2015). Radiofrequency ablation versus surgical resection for hepatocellular carcinoma within the Milan criteria: A study of 281 Western patients. International Journal of Hyperthermia, 31(7), 749-757. doi:10.3109/02656736.2015.1068382Fukushima, T., Ikeda, K., Kawamura, Y., Sorin, Y., Hosaka, T., Kobayashi, M., … Kumada, H. (2015). Randomized Controlled Trial Comparing the Efficacy of Impedance Control and Temperature Control of Radiofrequency Interstitial Thermal Ablation for Treating Small Hepatocellular Carcinoma. Oncology, 89(1), 47-52. doi:10.1159/000375166Goldberg, S. N., Stein, M. C., Gazelle, G. S., Sheiman, R. G., Kruskal, J. B., & Clouse, M. E. (1999). Percutaneous Radiofrequency Tissue Ablation: Optimization of Pulsed-Radiofrequency Technique to Increase Coagulation Necrosis. Journal of Vascular and Interventional Radiology, 10(7), 907-916. doi:10.1016/s1051-0443(99)70136-3Ahmed, M., Liu, Z., Humphries, S., & Nahum Goldberg, S. (2008). Computer modeling of the combined effects of perfusion, electrical conductivity, and thermal conductivity on tissue heating patterns in radiofrequency tumor ablation. International Journal of Hyperthermia, 24(7), 577-588. doi:10.1080/02656730802192661Lobo, S. M., Liu, Z.-J., Yu, N. C., Humphries, S., Ahmed, M., Cosman, E. R., … Goldberg, S. N. (2005). RF tumour ablation: Computer simulation and mathematical modelling of the effects of electrical and thermal conductivity. International Journal of Hyperthermia, 21(3), 199-213. doi:10.1080/02656730400001108Solazzo, S. A., Liu, Z., Lobo, S. M., Ahmed, M., Hines-Peralta, A. U., Lenkinski, R. E., & Goldberg, S. N. (2005). Radiofrequency Ablation: Importance of Background Tissue Electrical Conductivity—An Agar Phantom and Computer Modeling Study. Radiology, 236(2), 495-502. doi:10.1148/radiol.2362040965Barauskas, R., Gulbinas, A., & Barauskas, G. (2007). Investigation of radiofrequency ablation process in liver tissue by finite element modeling and experiment. Medicina, 43(4), 310. doi:10.3390/medicina43040039Haemmerich, D., & Wood, B. J. (2006). Hepatic radiofrequency ablation at low frequencies preferentially heats tumour tissue. International Journal of Hyperthermia, 22(7), 563-574. doi:10.1080/02656730601024727Haemmerich, 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.2003.809488Schutt, D. J., & Haemmerich, D. (2008). Effects of variation in perfusion rates and of perfusion models in computational models of radio frequency tumor ablation. Medical Physics, 35(8), 3462-3470. doi:10.1118/1.2948388Zhang, B., Moser, M. A. J., Zhang, E. M., Luo, Y., & Zhang, W. (2015). Numerical analysis of the relationship between the area of target tissue necrosis and the size of target tissue in liver tumours with pulsed radiofrequency ablation. International Journal of Hyperthermia, 31(7), 715-725. doi:10.3109/02656736.2015.1058429Solazzo, S. A., Ahmed, M., Liu, Z., Hines-Peralta, A. U., & Goldberg, S. N. (2007). High-Power Generator for Radiofrequency Ablation: Larger Electrodes and Pulsing Algorithms in Bovine ex Vivo and Porcine in Vivo Settings. Radiology, 242(3), 743-750. doi:10.1148/radiol.2423052039Abraham, J. P., & Sparrow, E. M. (2007). A thermal-ablation bioheat model including liquid-to-vapor phase change, pressure- and necrosis-dependent perfusion, and moisture-dependent properties. International Journal of Heat and Mass Transfer, 50(13-14), 2537-2544. doi:10.1016/j.ijheatmasstransfer.2006.11.045Pätz, T., Kröger, T., & Preusser, T. (2009). Simulation of Radiofrequency Ablation Including Water Evaporation. World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany, 1287-1290. doi:10.1007/978-3-642-03882-2_341Trujillo, M., Alba, J., & Berjano, E. (2012). Relationship between roll-off occurrence and spatial distribution of dehydrated tissue during RF ablation with cooled electrodes. International Journal of Hyperthermia, 28(1), 62-68. doi:10.3109/02656736.2011.631076Hall, S. K., Ooi, E. H., & Payne, S. J. (2015). Cell death, perfusion and electrical parameters are critical in models of hepatic radiofrequency ablation. International Journal of Hyperthermia, 31(5), 538-550. doi:10.3109/02656736.2015.1032370Chang, S.-J., Yu, W.-J., Chang, C.-C., & Chen, Y.-H. (2010). 7 PROTEOMICS ANALYSIS OF MALE REPRODUCTIVE PHYSIOLOGY BY TOONA SINENSIS ROEM. Reproductive BioMedicine Online, 20, S3-S4. doi:10.1016/s1472-6483(10)62425-xBeop-Min Kim, Jacques, S. L., Rastegar, S., Thomsen, S., & Motamedi, M. (1996). Nonlinear finite-element analysis of the role of dynamic changes in blood perfusion and optical properties in laser coagulation of tissue. IEEE Journal of Selected Topics in Quantum Electronics, 2(4), 922-933. doi:10.1109/2944.577317Doss, J. D. (1982). Calculation of electric fields in conductive media. Medical Physics, 9(4), 566-573. doi:10.1118/1.595107Jo, B., & Aksan, A. (2010). Prediction of the extent of thermal damage in the cornea during conductive keratoplasty. Journal of Thermal Biology, 35(4), 167-174. doi:10.1016/j.jtherbio.2010.02.004Belous, A., & Podhajsky, R. J. (2009). The effect of initial and dynamic liver conditions on RF ablation size: a study in perfused and non-perfused animal models. Energy-based Treatment of Tissue and Assessment V. doi:10.1117/12.809597Song, K. D., Lee, M. W., Park, H. J., Cha, D. I., Kang, T. W., Lee, J., … Rhim, H. (2015). Hepatic radiofrequency ablation:in vivoandex vivocomparisons of 15-gauge (G) and 17-G internally cooled electrodes. The British Journal of Radiology, 88(1050), 20140497. doi:10.1259/bjr.20140497Cha, J., Choi, D., Lee, M. W., Rhim, H., Kim, Y., Lim, H. K., … Park, C. K. (2009). Radiofrequency Ablation Zones in Ex Vivo Bovine and In Vivo Porcine Livers: Comparison of the Use of Internally Cooled Electrodes and Internally Cooled Wet Electrodes. CardioVascular and Interventional Radiology, 32(6), 1235-1240. doi:10.1007/s00270-009-9600-0Lee, J. M., Han, J. K., Chang, J. M., Chung, S. Y., Kim, S. H., Lee, J. Y., … Choi, B. I. (2006). Radiofrequency Ablation of the Porcine Liver In Vivo: Increased Coagulation with an Internally Cooled Perfusion Electrode. 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RF tumor ablation with internally cooled electrodes and saline infusion: what is the optimal location of the saline infusion?

<p>Abstract</p> <p>Background</p> <p>Radiofrequency ablation (RFA) of tumors by means of internally cooled electrodes (ICE) combined with interstitial infusion of saline may improve clinical results. To date, infusion has been conducted through outlets placed on the surface of the cooled electrode. However, the effect of infusion at a distance from the electrode surface is unknown. Our aim was to assess the effect of perfusion distance (PD) on the coagulation geometry and deposited power during RFA using ICE.</p> <p>Methods</p> <p>Experiments were performed on excised bovine livers. Perfusion distance (PD) was defined as the shortest distance between the infusion outlet and the surface of the ICE. We considered three values of PD: 0, 2 and 4 mm. Two sets of experiments were considered: 1) 15 ablations of 10 minutes (n ≥ 4 for each PD), in order to evaluate the effect of PD on volume and diameters of coagulation; and 2) 20 additional ablations of 20 minutes. The effect of PD on deposited power and relative frequency of uncontrolled impedance rises (roll-off) was evaluated using the results from the two sets of experiments (n ≥ 7 for each PD). Comparisons between PD were performed by analysis of variance or Kruskal-Wallis test. Additionally, non-linear regression models were performed to elucidate the best PD in terms of coagulation volume and diameter, and the occurrence of uncontrolled impedance rises.</p> <p>Results</p> <p>The best-fit least square functions were always obtained with quadratic curves where volume and diameters of coagulation were maximum for a PD of 2 mm. A thirty per cent increase in volume coagulation was observed for this PD value compared to other values (<it>P </it>< 0.05). Likewise, the short coagulation diameter was nearly twenty five per cent larger for a 2 mm PD than for 0 mm. Regarding deposited power, the best-fit least square function was obtained by a quadratic curve with a 2 mm PD peak. This matched well with the higher relative frequency of uncontrolled impedance rises for PD of 0 and 4 mm.</p> <p>Conclusion</p> <p>Saline perfusion at around 2 mm from the electrode surface while using an ICE in RFA improves deposition of energy and enlarges coagulation volume.</p

A clinically oriented computer model for radiofrequency ablation of hepatic tissue with internally cooled wet electrode

Purpose: To improve the computer modelling of radiofrequency ablation (RFA) by internally cooled wet (ICW) electrodes with added clinically oriented features. Methods: An improved RFA computer model by ICW electrode included: (1) a realistic spatial distribution of the infused saline, and (2) different domains to distinguish between healthy tissue, saline-infused tumour, and non-infused tumour, under the assumption that infused saline is retained within the tumour boundary. A realistic saline spatial distribution was obtained from an in vivo pig liver study. The computer results were analysed in terms of impedance evolution and coagulation zone (CZ) size, and were compared to the results of clinical trials conducted on 17 patients with the same ICW electrode. Results: The new features added to the model provided computer results that matched well with the clinical results. No roll-offs occurred during the 4-min ablation. CZ transversal diameter (4.10 ± 0.19 cm) was similar to the computed diameter (4.16 cm). Including the tumour and saline infusion in the model involved (1) a reduction of the initial impedance by 10 − 20 Ω, (2) a delay in roll-off of 20 s and 70 − 100 s, respectively, and (3) 18 − 31% and 22 − 36% larger CZ size, respectively. The saline spatial distribution geometry was also seen to affect roll-off delay and CZ size. Conclusions: Using a three-compartment model and a realistic saline spatial distribution notably improves the match with the outcome of the clinical trials

Radiofrequency-induced heating versus mechanical stapler for pancreatic stump closure: in vivo comparative study

Purpose: To assess the capacity of two methods of surgical pancreatic stump closure in terms of reducing the risk of pancreatic fistula formation (POPF): radiofrequencyinduced heating versus mechanical stapler. Materials and Methods: Sixteen pigs underwent a laparoscopic transection of the neck of the pancreas. Pancreatic anastomosis was always avoided in order to work with an experimental model prone to pancreatic fistula formation (POPF). Pancreatic stump closure was conducted either by stapler (ST Group, n=8) or radiofrequency energy (RF Group, n=8). Both groups were compared for incidence of POPF and histopathologic alterations of the pancreatic remnant. Results: Six animals (75%) in the ST Group and one (14%) in the RF Group were diagnosed of POPF (p=0.019). One animal in the RF Group and three animals in the ST Group had a pseudocyst in close contact with both pancreas stumps. On day 30 postoperative, almost complete atrophy of the exocrine distal pancreas was observed when the main pancreatic duct was efficiently sealed. Conclusions: Our findings suggest that RF-induced heating is more effective at closing the pancreatic stump than mechanical stapler and leads to the complete atrophy of the distal remnant pancreas.This work was supported by the Spanish 'Programa Estatal de Investigacion, Desarrollo e Innovacion Orientada a los Retos de la Sociedad' under grant TEC2014-52383-C3-R (TEC2014-52383-C3-3-R). F.B., R.Q. and E.B. declare stock ownership in Apeiron Medical S.L., a company that has a license for the patent US 8.303.584.B2, on which the device tested in this study is based. The other authors report no conflict of interests or financial ties to disclose. The authors alone are responsible for the content and writing of the paper.Burdío Pinilla, F.; Dorcaratto, D.; Hernandez, L.; Andaluz, A.; Moll, X.; Quesada-Diez, R.; Poves, I.... (2016). Radiofrequency-induced heating versus mechanical stapler for pancreatic stump closure: in vivo comparative study. International Journal of Hyperthermia. 32(3):272-280. https://doi.org/10.3109/02656736.2015.113684527228032

Hypersaline Infusion Protocol through the Portal Vein may Focus Electroporation on Tumor Tissue, but is it really Safe? Preliminary Results

Introduction: Irreversible Electroporation (IRE) is highly dependent on the electrical conductivity of the tissue and the high conductivity of tumor tissue, which leads to a lower field than in the surrounding healthy tissue. Hypersaline Infusion (HI) through the portal vein focuses IRE on scattered liver tumors, by creating a differential conductivity between the different types of tissue. The aim of this study is to determine the effects of the HI protocol on the hepatic and histological biochemical results. Methods: Ten male Sprague Dawley rats were used for HI protocol. Blood samples were collected at pre-, immediately post-, 24-hrs, 72-hrs, 1-week and 3-weeks post-HI. All the animals were sacrificed after one-month follow-up in order to collect histological samples. Results: The mortality rate in this procedure reached 30% (3/10). Only the pH and transaminases at 24-hrs were significantly and directly linked to mortality (p=0.036 and p=0.004, respectively). The three non-surviving animals had a four-time higher AST level at 24-hrs. Natremia normalized at 24-hrs post-HI. Statistically significant differences were found in hepatic necrosis between the non-surviving (n=3) and surviving rats (n=7) (30.67 ± 10.97 vs. 2.86 ± 7.56% respectively, p=0.01). Discussion: HI through the portal system involves a significant risk of possibly lethal cytolysis and acidosis. Therefore, compensatory measures and a reduced saline overload are warranted to improve the survival rates