Sviluppo e sperimentazione clinica di nuovi laser per il trattamento mininvasivo della nefrolitiasi, delle neoplasie uroteliali e dell’ostruzione cervico-uretrale.

Laser, acronym for “Light Amplification by Stimulated Emission of Radiation”, represents a monochromatic light with a narrow wavelength bandwidth, and with the properties of coherence and collimation. Consequently, the laser beams have minimal divergence, are directional, and produce intense beams of energy that may be targeted with precision. Since Parson in 1966 used a pulsed-ruby laser in a dog’s bladder, the use of laser technology in Urology has undergone significant advances with regard to different types of lasers, wavelength of energy and optical fibers used, precision of laser application and cost reduction, further improving laser technology and extending its potential applications. During the last decade some laser technologies have become established as standard modalities widely available to urologists. In the current urological practice, laser is predominantly applied to the treatment of urinary stones. However, a number of diseases other than stones can be successfully managed, including urethral, ureteral and ureteropelvic junction strictures, benign prostate hyperplasia (BPH) and upper urinary tract (UUT) transitional cell carcinomas (TCCs). Nowadays, Holmium:Yttrium–Aluminium–Garnet (Ho:YAG) laser is the most widespread, versatile, available laser. Recently, low-power versions of Ho:YAG laser, that yield up to 20 W of power, allowed successfully treating urinary stones, urethral, ureteral and ureteropelvic junction strictures, and TCCs. In contrast, high-power holmium laser devices (80-100 W) are still necessary for benign prostate hyperplasia treatment. Similar to Ho:YAG laser, the continuous wave radiation at 1470 nm delivered by diode laser has a high absorption in water; therefore, the radiation could produce, with a fiber tip immersed in water, high energy plasma bubbles, with photothermal and cavitation effects. Aim of the first study was the evaluation of efficacy and safety of a new low-power Ho:YAG laser with a maximum power limited to 10 W (Ho:YAG laser CalculaseTM, built by Karl Storz, Tuttlingen, Germany) in the transureteral retrograde treatments of both urinary stones and UUT TCCs. Aim of the second experiment was to test the 1470 nm diode laser in order to better understand the inter-action modalities of this wavelength with water and biological matter, evaluating its capacity to function as a lithotripter. Moreover, as 980 nm diode laser used in the selective light vaporization of the prostate has a low absorption in water and a high absorption in blood, with an optimal haemostatic effect, our idea was to create a high power multi-diode laser source, capable of delivering two simultaneous diode wavelengths (980 nm and 1470 nm) through the same optical fiber (laser unit built by Biolitec AG, Bonn, Germany). The goal of this study was to test this new diode laser in the photo-vaporization of the prostatic tissues, both in vitro and in vivo. In the first study, the new employed low-power Ho:YAG laser, that operates using low repetition frequencies and energy levels, would seem to provide excellent stone free rates, regardless of the stone hardness. Likewise, the CalculaseTM Ho:YAG laser, proved to be safe and effective in the treatment of the UUT neoplasms, allowing for a fine and complete tumor photoablation. In the second study, the 1470 nm diode laser proved to be the first continuous wave source capable of producing a high energy plasma bubble with a high thermoablation effect, confirming its capacity to function as a lithotripter, capable of shattering calculi of medium hardness. Moreover, combining the 980 nm with the 1470 nm radiation, it was possible to merge the optimal haemostatic effect with the 980 nm wavelength and the fast thermoablative effect of the 1470 nm radiation, thus guaranteeing, in our initial in vivo experiments, an efficient and safe photovaporization of the prostate. In conclusion, our preliminary data suggest a promising role of the multi-wavelength diode laser in the treatment of renal stones as far as of BPH.