Control parameters for high-intensity focused ultrasound (HIFU) for tissue ablation in the ex-vivo kidney

作     者：Köhrmann, KU Michel, MS Steidler, A Marlinghaus, EH Kraut, O Alken, P 

作者机构：Klinikum Mannheim GmbH Urol Univ Klin D-68135 Mannheim Germany 

出 版 物：《AKTUELLE UROLOGIE》 (Aktuel. Urol.)

年 卷 期：2002年第33卷第1期

页      面：58-63页

核心收录：

学科分类：1002[医学-临床医学] 100210[医学-外科学(含：普外、骨外、泌尿外、胸心外、神外、整形、烧伤、野战外)] 10[医学] 

主　　题：ultrasonic therapy thermocoagulation experimental model HIFU control parameters 

摘      要：Purpose: Therapeutic application of contactless thermoablation by high-intensity focused ultrasound (HIFU) demands precise physical definition of focal size and determination of control parameters. Our objective was to define the focal expansion of a new ultrasound generator and to evaluate the extent of tissue ablation under variable generator parameters in an ex vivo modell. Materials and Methods: Axial and transversal distribution of ultrasound intensity in the area of the focal point was calculated by needle hydrophone. The extent of tissue necrosis after focused ultrasound was assessed in an ex vivo porcine kidney model applying generator power up to 400 Watt and pulse duration up to 8 s. Results: The measurement of field distribution revealed a physical focal size of 32 x 4 mm. Sharp demarcation between coagulation necrosis and intact tissue was observed in our tissue model. Lesion size was kept under control by variation of both generator power and impulse duration. At a constant impulse duration of 2 s, generator power of 100 W remained below the threshold dosis for induction of a reproducible lesion. An increase in power up to 200 W and 400 W, respectively, induced lesions with diameters up to 11.2 x 3 mm. Constant total energy (generator power x impulse duration) led to a larger lesion size under higher generator power. Conclusion: It is possible to induce sharply demarcated, reproducible thermonecrosis, which can be regulated by generator power and impulse duration, by means of a cylindrical piezo element with a paraboloid reflector at a focal distance of 10 cm. The variation of generator power was an especially suitable control parameter for the inducement of a defined lesion size.