Ultrapulse, Superpulse or chopped?
These are marketing terms. All modern medical CO2 lasers are pulsed by electronic gating, and all can run continuously (referred to as CW) for short time periods. Chopped is a historical term that refers to mechanically gating the laser beam with a mechanical shutter of that actually chopped the beam.
All modern lasers are electronically gated or chopped. In general RF-excited lasers are designed to operate at a CW fixed power level, (240w for the Ultrapulse), and are pulsed by gating their CW power level. DC-excited lasers are also pulsed by electronic gating, but have the ability for superpulse (up to 250W for the Smartxide DOT), and the ability to vary the average power of each pulse.
When I was at Coherent, we designed the Ultrapulse as a high-power electronically-gated (chopped) CW-laser for ablation of large spots. For very short pulses and small spots used in fractional treatments the DC-excited lasers are more flexible since they can reach higher peak power levels for short times, and most important, the power can be varied. Thus, DC-excited lasers can ablate fractional channels at different drilling speeds resulting in the ability to vary the thermal zone for any depth. This cannot be done easily with the Ultrapulse or most of the RF-excited lasers. Modern scanning devices also allow DC-excited lasers, such as the Smartxide DOT from DEKA, to do full field ablation by scanning a superpulsed beam at higher irradiances than RF-excited lasers can supply.
Many other marketing terms have been used for pulsed lasers, and the branding can be confusing. The basic parameters are the length of the pulse, which determines the amount of thermal diffusion, and the power level of the pulse which determines the speed of ablation. Other interesting clinical effects can be obtained by modulating the shape of the pulse in various ways – a high enhanced pulse followed by a lower sustained power level will ablate very quickly and cleanly through the surface and then ablate at a slower rate depositing more heat below the surface.
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