Medical Lasers and Laser Safety

Transcription

1 Medical Lasers and Laser Safety Key Points Lasers & Laser Safety: - Know the three unique characteristics of laser light - Be familiar with the different medical laser technologies - solid, gas, excimer, semiconductor (diode) - Know the common solid state lasers - KTP, x-yag - Know the common gas lasers - CO 2, Argon - Know which lasers are: visible, UV, IR - Know the four application parameters of medical lasers - Know which class medical lasers belong to - Know the three safety design features required in medical lasers - Know the Non-Beam hazards associated with medical lasers - Know the most important measurements in the PM of a laser: safety checks, output verifications, and replacement of expendables D. J. McMahon rev cewood "light amplification by stimulated emission of radiation Basic principle of a LASER Under the right conditions, electrons can be temporarily raised to a higher energy level. When the electron drops back to its original state, it emits a photon. The input energy is converted to a different type of energy.

2 Stimulated emissions begin to cascade : one creates two, two create four, etc Original concept of the first type of laser, using a ruby rod as the medium: ruby: aluminum oxide with chromium Repeated pulses of light from the flash lamp pass into the ruby rod. Photons are emitted from increasing numbers of atoms

3 and begin to oscillate between opposite ends of the length of the rod until they gain enough energy to be emitted from the non-mirrored end of the rod, at one frequency, in phase, and as a linear beam. light is collimated; it escapes through a small port to stay linear Laser energy is Monochromatic: - emissions of one wavelength (frequency) Coherent: - emissions are all in phase Collimated: - emissions are all in one direction Monochromatic: animation with cool sound effects... A laser s light is only one specific wavelength, and not necessarily in the visible spectrum.

4 Most common medical lasers: and CO 2 at 10,400 nm

5 Application Parameters Varying fluence: > Wavelength of laser > Pulse duration > Pulse rate > Tissue area impacted by laser energy Expressed as fluence : energy per unit area, in joules / cm 2 PD = power dissipation Types of Lasers > Solid State Lasers > Gas Lasers > Excimer Lasers excited dimer - (dimer = a 2-part molecule) > Dye Lasers - use organic dyes (liquid) > Semiconductor Lasers Solid State Lasers Use a solid medium as the lasing source Most common medical types: x-yag Yttrium-Aluminum-Garnet (actually Yttrium-Aluminum Oxide) doped with a specific element x: Nd (Neodymium) Nd-YAG 1064 nm YAG laser Ho (Holmium) Ho-YAG 2100 nm Holmium laser Er (Erbium) Er-YAG 2940 nm Erbium laser (note: the x-yag lasers are all in the infrared spectrum) KTP (Potassium Titanyl Phosphate) 532 nm (visible spectrum) applications: General, GYN, Orthopedics, genito-urinary surgery, etc.

6 Gas Lasers > Use a gas as the lasing medium > Most common medical types are CO 2 and Argon Excimer Lasers CO 2 Lasers: wavelength = 10,600 nm - invisible, easily deflected - used for ENT, plastic, derm, & others - use mirrors in long arms to direct Argon Lasers: wavelength = 514nm - used for eye surgery (far infrared) (visible) > Use two gases which combine into a dimer when electrically stimulated. > Typical wavelength = ~193 nm > Used especially for corrective eye surgery - laser-assisted in situ keratomileusis or LASIK - photorefractive keratectomy or PRK Semiconductor (Diode) Lasers > Use a diode as the laser source > Low power > Wavelength can be varied > Commonly used in CD or DVD decks, etc > Medical use in ophthalmology & derm Lasers for Tattoo Removal Use a pulsed ( Q-switched ) mode (High energy in very short pulses) Use color-specific wavelengths: -- black or dark blue ink: 1064 nm -- green ink: 650 nm -- light blue ink: 585 nm -- red ink: 532 nm Medlite model C Q-switched, 532 / 585 / 650

7 Lasers for Hair Removal Photodynamic therapy (PDT): Similar to Stereolithography (SLA 3D printing) and dental curing lights for resin fillings. Tatoo removal: Skin resurfacing: Prostate laser surgery animation: Standards for Laser Safety Safe use of any laser, including maximum permissable exposures (MPEs), is covered in ANSI standard Z136.1 Safety issues specific to medical lasers are covered in ANSI standard Z136.3 ( Identical international standard is EN )

8 Safety Classifications of Lasers: Class 1 IEC safe under all conditions Class 1M safe under all conditions, except when passed thru magnifying optics Class to700 nm (visible) < 1mW continuous, <.25 sec exposure Class 2M Class 2, used thru magnifying optics Class 3R visible continuous wave, < 5mW Safety Classifications of Lasers, cont d: Class 3B continuous 315 nm and up, < 0.5 W pulsed 400 to 700 nm, < 30 mj eyewear required key switch & interlock required Class 4 any laser above the Class 3B limits capable of altering human tissue key switch & interlock required hazardous to view under any condition All medical lasers are Class 4 by definition Laser Safety Control Measures: > Laser Safety Officer > Procedures > The Laser Treatment Area > Protective Equipment > Warning Signs and Labels Non-Beam Hazards: - Electrical & Electronic - Smoke Plume - Fire & Explosion Hazards

9 Laser Safety Officer - RN or HTM tech who is trained on the safe use of lasers in healthcare. > Training is usually a 2-day course thru any of several independent agencies > Monitors laser procedures and logbooks to assure that there is good staff compliance > Notifies management of non-compliance > Member of the Laser Safety Committee Emergency shutoff switch Keyed power switch Key should only be inserted when the laser is in use (OSHA requirement) Room door interlock circuit Laser will not power up unless this circuit is closed, either by a door switch or a shunt connector (shown).

10 Laser eye protection -- for KTP (visible) laser Laser-safe endotracheal tubes Minimize the hazard of ignition of the plastic e/t tube within the airway. Reflective metallic surface on tube Dual tracheal cuffs filled with saline (not air)

11 Laser Maintenance & Repair Laser power meters -- - Most PM and repair on contract by manufacturer s field service engineers - Some service schools available - In-house PM s are mainly safety checks, output verifications, and replacement of expendables (coolants, seals, etc.) Many hospitals now rent lasers on a per-case basis. All major metro areas have companies who can provide a laser for a specific surgical procedure (usually with an operator) on 24 hours notice. As with any other outside equipment, it is the responsibility of CE to perform a safety check on these units each time they arrive on site. Major Players in Medical Lasers Lumenis (was Coherent, Sharplan, & HGM) AMS (was Laserscope) Iridex Zeiss & many others