During interdisciplinary collaboration in scientific-research programmes in the field of high power ultrasound applications in neurosurgery, a possibility to apply highpower ultrasonic point sources for minimally invasive neurosurgery has been noticed. Earlier experiences with noncontact applications of high energy ultrasound have induced the idea of ultrasonic energy transfer through an elastic wire waveguide. Development of a new type of neurosurgical endoscopic contact ultrasonic probe – knife, which started in 1999, has resulted in a fully functional prototype (NECUP 1). Further advances in interdisciplinary knowledge on contact applications of high-power ultrasound in general surgery, eventually resulted in development of an improved contact ultrasonic surgical system (NECUP 2). The scope of this thesis is to present the results of theoretical and experimental research in the field of generation and propagation of high-power ultrasound as well as of its application in minimally invasive surgery. Theoretical part of the thesis covers methods for calculation and modelling of optimised ultrasonic transducers giving a basis for design of a high-power ultrasonic point source for minimally invasive surgery. Generation and transmission of ultrasonic waves from the ultrasonic transducer, through the mechanical concentrator to the endoscopic tool and the ability for adaptation to different surgical applications have been described. By means of the conducted analysis, terms of transmission and transformation of the acoustic energy from the ultrasonic transducer to the endoscopic tool have been determined. In the analysis of the mechanical concentrators, with the help of finite elements method modelling, parametric optimisation of the concentrator shape and length has been conducted. In the experimental part of the thesis, methods for verification of the theoretical results have been presented. This includes methods for validation the performance of the 1,6 mm titanium wire as an endoscopic tool and experimental methods for assessment of electric and acoustic characteristics of the high-power ultrasonic point source. The emitted acoustic power, sound pressure distribution in the free field (vertical and horizontal plane) and the efficiency Alan Štimac Doktorska disertacija 179 coefficient of the ultrasonic probe have been determined experimentally by measurements in an anechoic hydroacoustical tank. The results of this research present a stimulus for application of high-power ultrasound in the minimally invasive surgery, while the experimental results indicates the need for metrological supervision of this and similar surgical equipment.