Exposure Limits for Laser Radiation - · PDF fileEdinburgh, United Kingdom, 9-11 May 2012...

Edinburgh, United Kingdom, 9-11 May 2012ICNIRP 7th International NIR Workshop

Exposure Limits for Laser Radiation

ICNIRP Member

U.S. Army Medical Research Department (Recently retired!)

San Antonio, TX

Bruce E. Stuck, ICNIRPExposure Limits for Laser Radiation

Bruce E. Stuck

Lasers in Our Environment• Home (compact disk players, laser printers)• School (laser pointers, teaching optics)• Supermarket (bar code scanners)• Hospital (photocoagulate, burn, cut, ablate, PDT)• Communications (fiber optics, free space)• Entertainment (concerts, amusement parks, hotels,

electronic games)• Industry (heat, weld, cut, align, measure, count)• Military (rangefinders, designators, illuminators,

training devices)• Security Systems • Research Laboratories

Medical Applications of Laser Radiation• Used in most medical specialties to:

Heat, burn, cut, ablate, illuminate, stimulate• A few examples:

– Corneal refractive surgery • Photo refractive keratoplasty (PRK) • PRK LASIK (Laser in-situ keratomilieusis)

– Photocoagulation– Photodisruption (secondary cataract removal)– Photodynamic therapy (PDT)– Surgery - endoscope compatible– Biostimulation or biomodulation– Flourescence angiography– Imaging (SLO, Wavefront corrected retinal Imaging, OCT)– Alignment (MRI)– Doppler blood flow– Skin rejuvenation (fractional laser therapy)

WavelengthRange (nm)

Ultraviolet180-315

315-400

Visible400-700

WavelengthRange (um)

Near Infrared0.7-1.4

Infrared1.4-1000

Laser Type

ArF ExcimerKrCl ExcimerKrF ExcimerNd:YAG(quadrupled)ArgonXeCl Excimer

Helium CadmiumNitrogenXeF ExcimerArgonKrypton

Helium CadmiumArgonCopper VaporKryptonNd:YAG (doubled)Helium Neon(HeNe)Dye (Coumarin)Dye (Rhodamine)HeNe (yellow)HeNe (orange)

HeNe (red)

Wavelength(s)(nm)

193222248266275308

325337351

351, 363350.7, 356.4

441.6476, 488, 514.5

511, 568530532543

400-550550-700

594610

Laser Type

InGaAlPKryptonRuby

Ti:SapphireGaAIAsAlexandriteGaAIASGaAsNd:GlassNd:YAG(HeNe)Nd:YAG

Erbium GlassHolmiumHydrogen FlourideErbium YLFDeuterium FlourideCarbon MonoxideCarbon DioxideWater VaporHydrogen cyanide

Wavelength(s)(um)

670nm647-676 nm

694.3 nm

0.7-1.00.78

0.72-0.800.850.9051.0601.064

1.080, 1.1561.318, 1.338, 1.356

1.542.06

2.6-3.02.94

3.8-4.05.0-5.5

10.6118337

Common Lasers and Laser WavelengthsCommon Lasers and Laser Wavelengths

Laser Emission Characteristics• Emission Durations

– Single pulses as short as 10 femtoseconds (10-14 seconds)– Continuous wave (CW)– Repetitive pulses - Pulse repetition frequencies (single pulse

to 108 pps)• Emission Wavelengths

– Near ultraviolet to the far infrared– Usually highly monochromatic (single wavelength or color)

• Beam Divergence– Small beam divergence ( 0.1 - 1 milliradian)– 0.5 mr divergence - 50 cm beam diameter at 1 km– Retinal Hazard Region: retinal irradiance diameter can be 30

micrometers or slightly less– Most applications use a focused beam

Update of Exposure LimitsLaser Radiation Issues

• dependence of the injury threshold on retinal irradiance diameter

• ns pulses • near infrared exposures (wavelength

dependence – new work near 1.3 m) • repetitive pulses

Data Sources for Updates• Dose-response data (thresholds)

– Animal models– Cell models

• Interaction or injury mechanism assessment• Biophysical/computational models• Medical applications• Laser accident cases• Environment illumination

Laser Laser BioeffectsBioeffectsDose Response RelationshipsDose Response Relationships

Dose ResponseWavelength OphthalmoscopyExposure Duration AngiographyRadiant Exposure PathologyIrradiance diameter Electrophysiology Exposure Site Visual FunctionRepetitive Pulse Imaging (OCT,SLO)

Exposure ( Hz – MHz) Cellular metrics (apoptosis)Repeated exposure genomics)

Time of Observation (hours, days, years?)

Absorption• How effectively light is captured by a target tissue

Transmission• How effectively light penetrates overlying media to reach the target

tissue

Wavelength

Bruce E. STuck, ICNIRP Exposure Limitts for Laser Radiation

Measuring Retinal Injury Thresholds

ED50 – that dose having a 50% probability of producing an ophthalmoscopicallyobservable lesion at 1 – 48 hours after exposure. TIE – Total Intraocular Energy. That energy incident at the cornea of the eye within the area of the ocular pupil

Threshold laserThreshold laser--induced retinal injury induced retinal injury occurs at the RPE due to the melanin occurs at the RPE due to the melanin absorptionabsorption

Retinal ED50 Threshold Data and ELs for 0.7 to 1.4 mExposure Durations, 0.1 s and ns

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

wavelength, m

J 0.1 s ED50, 1 hr

ns ED50, 1 hrns ED50, 24 hr0.1 s model fitns model fitns MPE0.1 s MPEproposed ns MPEproposed 0.1 s MPEnew proposed ns MPEnew proposed 0.1 s MPE

Interaction/Damage Mechanisms

Retinal Injury Thresholds

MPE2007

MPE - Proposed

1 10010

(mrad)

Spot-size Dependence

D = 500 m

Coll. beam

1 10010

Number of Pulses

Repetitive Pulse

Summary• Updated Exposure Limits for Laser Radiation.

– Spot-size dependence (“time dependent max”)– Nanosecond exposure durations– Repetitive pulses– Near Infrared– Measurement acceptance angles more clearly defined

• Update had a long gestation period! Basis: Data acquired and reviewed in the last 3-10 years.

• Most of the Els have NOT changed. • Harmonization – Based upon ICNRIP Guidelines!

Future Research/ Issues• Long duration exposures

– Advanced imaging devices• Repetitive pulses• Far Infrared - 10 m to 1 mm (THz region)

Acknowledgements• Jack Lund• Brian Lund• Karl Schulmeister• Per Soderberg• David Sliney• Benjamin Rockwell• Robert Thomas• Jeremiah Brown, Jr.• Martin Mainster• Joseph A. Zuclich

Thank you!

Questions?

Exposure Limits for Laser Radiation - · PDF fileEdinburgh, United Kingdom, 9-11 May 2012...

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