Low-threshold cavitation in water using IR laser pulse trains.

The low-temperature cavitational disruption by trains of laser pulses was demonstrated in water. The trains used in the experiment were generated by a Raman laser at a wavelength of 1626 nm. The mean value of the fragmentation threshold energy density per pulse in a train was estimated to be equal to 7.2x10(6) J/m(3). The corresponding amplitude of the negative pressure had the order of 6-7 bars at a temperature jump of only about 2 degrees C. This result opens up prospects for developing precision nonthermal cavitational laser surgery.

[The biological effects and criteria for assessing the danger of laser radiation]. / Biologicheskie éffekty i kriterii otsenki opasnosti lazernogo izlucheniia.

Biological effects of laser radiation (LR) are determined by the absorption properties of the irradiated tissues and physiological characteristics of radiation. The high intensities of the effect are accompanied by melting, evaporation, substance ionization, formation of shock and acoustic waves. Under the action of the low-intensity LR there prevail photochemical, photobiological and thermal processes. The action of LR of one or another wave length is determined by the initial stages of its interaction with biological substrate. The biostimulating action of LR is widely used in clinical medicine. On the contrary, the effects that give rise to morphofunctional lesions of biological tissues determine the necessity of elaborating preventive measures ensuring protection of man from LR. It is generally accepted that thresholds of the damaging action on the retina and skin may be used as the main criterion for maximum allowable level (MAL) basing. In addition to the changes observable in the directly irradiated tissues, many authors point to a possibility of functional disturbances on the part of certain organs and systems of the body, followed by the formation of asthenic and vegetovascular syndromes. The experimental and clinical data confirm that the body may develop common nonspecific changes which, together with the local damaging effects, can be regarded as criteria for an adverse action of LR and, therefore, taken into account in MAL derivation.

[Laser transscleral contact-compression coagulation of the fundus oculi tissues]. / Lazernaia kontaktno-kompressionnaia transskleral'naia koaguliatsiia tkanei glaznogo dna.

Experimental investigations were carried out in monkeys and rabbits for the purpose of quantitative and qualitative assessments of contact transscleral methods of action on intraocular, structures using ruby and AIH with Nd lasers adapted with a quartz monofiber. It was found that compression of a monofiber into the sclera produces its clarification, this providing effective transmission of radiation without any loss. Essential distinctions of the character of interaction between laser radiation and eye coats in transmission of radiation by a monofiber with its compression into the sclera allowed to substantiate and recommend for a clinical usage the contact-compression transscleral method of laser microsurgery.