Total energy output from an endovenous laser ablation (EVLA) console does not vary between continuous or pulsed use, despite observed variations.

BackgroundEndovenous laser ablation (EVLA) in truncal veins uses a constant power and smooth pull-back. In short veins (ie: incompetent perforator veins or neovascular tissue) power can be pulsed, allowing tissue cooling between pulses and reduction of thermal spread, protecting surrounding tissues. Power meter measurements suggest it takes over 2 seconds for a diode laser to reach 90% of maximum power output. Hence pulses shorter than 2 seconds might result in less energy being deposited into target tissues than indicated on the console. The aim of this study is to compare the power emitted from the tip of the laser device during continuous or pulsed use to that displayed on the console.MethodsA 600 micron radial fibre connected to a 1470 nm EVLA diode console was fired at 10 W onto a sensor connected to a power meter, until 100 J had been emitted, for each of the following: continuous; pulsed 1 sec on, 1 sec off; pulsed 0.5 sec on, 1 sec off. Each was repeated 5 times, and the power recorded every 0.1 sec.ResultsThe power meter recorded reduced peak powers in the pulsed experiments as expected, due to delay in reaching maximum output. However, all three protocols resulted in 94% of the total energy being emitted from the tip of the EVLA device. Analysis of the power data suggested that there was a delay in the power being recorded by the sensor and power meter both when activating and deactivating the laser.ConclusionPulsing the laser power did not affect the total energy emitted from the tip of the EVLA device. The delay in reaching maximum power recorded by the power meter appears to be due to a sensor delay responding to incident laser energy, rather than the output from the laser diode and console.