Quantitation of Laser Irradiation By-Products

In-vivo laser irradiation can create hazardous by-products. The purpose of the study was to evaluate the nature of the debris, and quantitate them. Segments of fresh porcine myocardium and vascular wall were irradiated in sodium phosphate buffer, with Argon laser. The amounts of tissue vaporized and accumulation of tissue debris were measured, and analyzed with Scanning Electron Microscopy (SEM). Gasseous & thrombi by-products & temperature changes were measured in an artificial circulation using a centrifugal pump (Bio-medicus 520D). Blood was hepar-inized (5000 u) and circulated @ 21/min. Contlnous laser irradiation of the blood was done @ 6 1/2 watts with 400 micron regular quartz or hot-tip fiber, for 10 minutes. Vascular walls and myocardial debris formed at a rate of 227 and 61.5 mg respectively per 1,000 mg tissue lased, showing charred fragmented tissue segments on SEM with sizes ranging up to 3 mm. Fragments of cell wall, and intracellular membranes were also identified. 23.5 and 15.5 ml of gas were formed by both fiberoptic and hot-tip irradiation respectively. Temperature elevations were between 1 and 3.9°C in lasing chamber and 1 and 2°C in downstream chamber. 15×5 and 6×4 mm charred thrombi formed at catheter tip respectively, regardless of anticoagulant used. In conclusion: very significant amounts of gas, tissue debris and charred thrombi were formed during continuous lasing process to the extent that' modifications in laser techniques and application must be developed before laser therapy can be applied in clinical settings.