[Peculiarity of pulsed dye laser lithotriptor and its clinical application]

Ultrasound lithotriptors (USL) and electrohydraulic lithotriptors (EHL) are representative lithotriptors for endoscopic elimination of upper urinary tract stones. However, they have some disadvantages. For example, USL can not be used with flexible scopes and EHL can cause unexpected tissue injury. To overcome these problems, the pulsed dye laser lithotriptor (MDL-1, Candera Co.) was developed. The characteristics of this laser lithotriptor and its direct effects on tissue was investigated. This pulsed dye laser lithotriptor generates a 504 nm wavelength green light beam by using a combination of a xenon flash lamp and the greenish dye composed of coumarin solution. The maximum output energy is 60 mJ/pulse and the pulse duration is 1.5 microsecond. The pulse rate can be varied from 1 to 20 Hz. First, the intensity of the shock wave was measured by using a combination of a piezoelectric element and an oscilloscope, and then, the results were compaired with those obtained by a similar experiment with an EHL. The average intensity of the shock wave was 54.4 mW under the conditions of 40 mJ/pulse of output energy and 10 Hz of pulse duration. On the other hand, the EHL generated an average of 54.7 W under the conditions of 400 mJ/pulse output energy. Then, fragmentation of various kinds of urinary stones in saline solution was performed. The results showed that this lithotriptor could fragment almost all kinds of stones except cystine stones. Then, hen's eggs were used to observe the effect if laser bean influenced on the organism immediately behind the photoradiated object. Only the egg shell was demolished but the egg membrane below the eggshell did not undergo any change. After these experiments, skin, liver, kidney and urinary bladder of nude mice and human prostatic urethral mucosa in case of TUR-P were irradiated by this laser. The results showed that laser energy caused slight penetration and localized hemorrhage from the surface of epithelium to subcutaneous tissue. It was confirmed that these effects were generated when the tip of the quartz fiber was in direct contact with the object.(ABSTRACT TRUNCATED AT 250 WORDS)