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  • 1
    Language: English
    In: The Journal of Urology, 2006, Vol.175(3), pp.1122-1126
    Description: We investigated a newly developed bipolar and multipolar RF ablation system with an internally cooled electrode and resistance controlled power output in a standardized model of perfused ex vivo kidney tissue. RF energy was applied at different power levels (20, 30 and 60 W) for 1, 3, 5 and 9 minutes. Each treatment parameter was repeated 5 times. For the 20/30 W levels a bipolar electrode with an active conducting part of 20/30 mm was selected. At 60 W 2 bipolar electrodes with an active conducting part (30 mm each) were connected. Lesion volumes and shapes were calculated by measuring the maximum vertical, long axis and short axis diameters of the macroscopic lesion. Lesion volume increased significantly with the treatment time and generator power applied (p 〈0.0001). Lesion size in multipolar ablated zones was larger than that in bipolar ablated zones. A reliable dose-effect relationship existed between the generator power/applied treatment time and ablated tissue lesion size. All lesions were elliptical. Bipolar and multipolar RF ablation with an internally cooled electrode and tissue resistance control represent an interesting advance in RF technology. The development of lesion size and volume is predictable, while a uniform lesion shape can be achieved in perfused ex vivo kidney tissue. Further in vivo trials are required to test whether complete and reliable tumor tissue ablation is possible with this system.
    Keywords: Kidney ; Surgical Procedures ; Minimally Invasive ; Carcinoma ; Renal Cell ; Catheter Ablation ; Swine ; Medicine
    ISSN: 0022-5347
    E-ISSN: 1527-3792
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  • 2
    In: BJU International, April 2006, Vol.97(4), pp.822-828
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1464-410X.2006.06038.x Byline: AXEL HACKER, STEFAN VALLO, CHRISTEL WEISS (*), THOMAS STEIN ([dagger]), PETER ALKEN, THOMAS KNOLL, MAURICE STEPHAN MICHEL Keywords: surgical procedures; minimally invasive; carcinoma; electrodes; radiofrequency ablation Abstract: OBJECTIVE To investigate the technical characteristics of a newly developed device for bipolar and multipolar radiofrequency ablation (RFA) of kidney tissue with a resistance-controlled power output. MATERIALS AND METHODS The standardized model of the isolated perfused ex vivo porcine kidney was used. Two different applicators (20 and 30 mm active length) were selected for bipolar RFA, and one pair of applicators (2 x 30 mm active length) for multipolar RFA. RF energy was applied at different power levels (20, 30, 60 W) depending on the total active length of the electrodes. Treatment times were 1, 3, 5 and 9 min. The ablation cycles were recorded in continuous digital real-time and displayed on a monitor showing pre-set power, actual applied power, applied energy, tissue resistance, and impedance. Lesion sizes were measured macroscopically. A coagulation coefficient (coagulated tissue volume per applied energy unit) was calculated. RESULTS There was a dosage-effect relationship between the generator power/treatment time and the sizes of the lesions. With increasing treatment time, less tissue volume was coagulated per unit of applied energy. The actual applied energy was lower than that calculated theoretically. The resistance and impedance values for the 30-W applicator were lower than those of the 20-W applicator. CONCLUSIONS The technical features of this RFA device, with internally cooled bipolar and multipolar applicators and a resistance-controlled power output, represents an innovative improvement in RF technology. In vivo studies are needed to confirm the expected advantages and the suitability of this device for complete and reliable ablation of renal tumours. Author Affiliation: (*)Department of Biomathematics, University Hospital Mannheim, Ruprecht-Karls University of Heidelberg, and ([dagger])Celon AG Medical Instruments, Teltow, Germany Article History: Accepted for publication 31 October 2005 Article note: Axel Hacker, Department of Urology, University Hospital Mannheim, Theodor-Kutzer-Ufer 1-3 68135 Mannheim, Germany. e-mail: axel.haecker@chir.ma.uni-heidelberg.de
    Keywords: Surgical Procedures ; Minimally Invasive ; Carcinoma ; Electrodes ; Radiofrequency Ablation
    ISSN: 1464-4096
    E-ISSN: 1464-410X
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  • 3
    Language: English
    In: Lasers in surgery and medicine, September 2014, Vol.46(7), pp.558-62
    Description: To evaluate the clinical value of different magnetic resonance imaging (MRI) sequences for a real-time thermo-monitoring during laser-induced thermotherapy (LITT) in kidneys. Twenty-eight ex vivo pig kidneys were treated with laser ablation under MR guidance in a high-field MR scanner (Magnetom Espree or Avanto Fit, Siemens, Germany). For the thermal ablation of the kidney, a neodymium yttrium-aluminum-garnet (Nd:YAG) laser was used in combination with a special protective catheter (length 43 cm, 4 French) which is sealed at the distal end. First, ablation was performed for 7, 10, and 13 minutes using FLASH sequences for investigation of time-dependent growth of lesion size. In the second step, we evaluated the optimal imaging sequence during a 7 minutes ablation of the kidney and after cooling using four different MR sequences (Haste, FLASH, radial VIBE, and Caipirinha DIXON). Macroscopic lesion volume increased from 3,784 ± 1,525 mm(3) to 7,683 ± 5,756 mm(3) after the ablation from 7 to 13 minutes and MR volume ranged from 2,107 ± 1,674 mm(3) to 2,934 ± 1,549 mm(3) after the ablation from 7 to 13 minutes. During ablation, FLASH (132 ± 34%) and radial VIBE (120 ± 43%) sequences displayed lesion volumes most efficiently with a trend to overestimation. The Caipirinha DIXON (323 ± 24%) sequence overestimated the volumes significantly during real-time monitoring. The volumes measured by MRI with FLASH (61 ± 30%), Haste (67 ± 28%), or radial VIBE (48 ± 14%) sequences after cooling of the kidney after ablation were always underestimated. The Caipirinha DIXON (142 ± 2%) sequence still overestimated the lesion volume after cooling of the kidney. LITT is a feasible ablation modality in kidney tissue. Moreover, macroscopic and MR lesion volume increases time-dependently. For online monitoring, radial VIBE and FLASH sequences seem to be most efficient.
    Keywords: Litt ; Mri ; Laser Ablation ; Real-Time Monitoring ; Renal Cancer ; Thermometry ; Surgery, Computer-Assisted ; Hyperthermia, Induced -- Methods ; Kidney -- Surgery ; Laser Therapy -- Methods ; Magnetic Resonance Imaging -- Methods
    E-ISSN: 1096-9101
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 4
    Language: English
    In: European Urology, 2005, Vol.48(4), pp.584-592
    Description: Radiofrequency Ablation is an investigational treatment option for RCC. The aim of our study was to test the ablation algorithms of four different RF systems in a standardized ex vivo perfused porcine kidney model. A multitine monopolar dry electrode (impedance-based system), a multitine monopolar dry electrode (temperature-based system), a single monopolar wet electrode (impedance-based system) and a single monopolar dry, internally-cooled electrode (impedance-based system) were selected. RF energy was applied at different treatment parameters (power with and without control, tissue temperature, saline enhancement) for 1, 3, 5 and 9 minutes in healthy perfused ex vivo porcine tissue. Each treatment parameter was repeated 5 times. Maximum vertical, long-axis and short-axis diameters of the macroscopic lesion were measured and lesion volumes/ shapes were calculated. Lesion volumes increased significantly with the pre-selected tissue temperature and saline enhancement. Saline enhancement created larger, but irregular shaped lesions. The impedance-based system created lesion volumes that were predictable by treatment time and generator power. Lesions were unpredictable when uncontrolled generator power was applied. The created lesion shape was dependent on the selected electrode configuration. The currently available monopolar RFA systems offer different specific technical features to control tissue ablation. Detailed knowledge of the specific characteristics of each RF system is necessary to provide a higher chance of successful clinical outcome by complete and reliable ablation.
    Keywords: Radiofrequency (Rf) Ablation ; Kidney ; Renal Cell Carcinoma ; Experimental Study ; Medicine
    ISSN: 0302-2838
    E-ISSN: 1873-7560
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