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LaserSafety

MD6305Laser‐TissueInteractions‐Class12

JaeGwan Kim

jaekim@gist.ac.kr ,X2220

DepartmentofBioMedical Scienceand Engineering

Gwangju InstituteofSciencesandTechnology

Copyright.Mostfigures/tables/textsinthislecturearefromthetextbook“Laser‐TissueInteractionsbyMarkolf H.Niemz 2007”andthismaterialisonlyforthosewhotakethisclassandcannotbedistributedtoanyonewithoutthepermissionfromthelecturer.

PPT modified from Jay Young Bae’s presentation

Index. Contents

1. Introduction.2. Laserhazards.

– Chemical/Electrical/othersecondaryhazards.– Eyehazards.– Skinhazards.

3. LasersafetystandardsandHazardclassification.– LaserHazardsClasses.– Classificationsystem.– Eyeprotection.

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Introduction.

Endotracheal tube set on fire by a CO2 laser

Introduction

Introduction. Introduction

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Introduction. Introduction

Papillomatous lesion :  benign epithelial tumor growing exophytically(outwardly projecting) in nipple‐like and often finger‐like fronds

Introduction. Introduction

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Introduction. Introduction

• Specializedlaser‐resistantprotectedendotrachealtube

Introduction. Introduction

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Introduction. Introduction

Laser hazards – Chemical / Electrical / Other secondary.

‐ Rhodamine 6G is also used as a laser dye, or gain   medium, in dye lasers, and is pumped by the 2nd    (532 nm) harmonic from an Nd:YAG laser or nitrogen laser.

‐ Rhodamine 6G chloride is a bronze/red powder with the chemical formula C27H29ClN2O3. Although    highly soluble, this formulation is very corrosive to all metals except stainless steel.

‐ Cryogenic coolant hazards. (Nitrogen gas)‐ Excessive noise from very high energy lasers.‐ X radiation from faulty high voltage (>15KV) power supplies.‐ Explosions from faulty optical pumps and lamps.‐ Fire hazards

Laserhazards

• Chemical/Electrical/Othersecondary

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Laser hazards – Chemical / Electrical / Other secondary.

Laser on amalgam can cause mercury fume.

Laserhazards

Laser surgery on viral disease : 

Carbon dioxide laser energy is absorbed by intracellular water but not by proteins or nucleic acids. HPV DNA may be released during laser vaporization of genital HPV infected region. 

HPV DNA type 6 was found in pre‐filter canister after laser treatment. Without appropriate equipment, surgeon can be contaminated by viral RNA and DNA.

HPV: human papillomavirus. Most HPV infections cause no symptoms and resolve spontaneously. In some, they persist and result in warts or precancerous lesions. The precancerous lesions increase the risk of cancer of the cervix, vulva, vagina, penis, anus, mouth, or throat.

Laserhazards

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Miscellaneous. Miscellaneous

• AbravesurgeonconductedLMSsurgery(laryngealmicrosurgeryusinglaser)onAIDSpatientwithjustonesuctiontipandsimplesurgicalmask.

• WhenwegetfirstHOLEP(HolmiumLaserEnucleationoftheProstate)machine,itspowerconsumeexceededtheoperationroom’spowersupply.Consequently,theoperationroom’spowersupplyshutdownedandallelectricfacilitysuddenlystoppedincludingpatient’sventilatorandallmonitoringdevices

• Surgeonusuallyusesalcoholtosterilizethelesionandadjacentskin.Liversurgerywasstarted,buttheArgonlaserdevicedidn’tworked.Sosurgeondrewbackthedeviceandchecked,thenputitonthedrapedskin,waitingforserviceengineer.Thensuddenlythedeviceemittedlaserbeambutnoonerecognizedatthatmoment.Soonafter,firebrokeoutonalcohol‐wetdrape.

Power&Hazards

• Power&Hazards– Nospecificthresholdbetweensafe,potentiallyhazardous,clearlydangerousbeam.

– Factors:Beampower,Exposuretime,Distancefromthelaser,retinalinjurylocation.

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EyeHazards

• EyeHazard– Deliberatelystare:1mWbeamcouldcauseaspotontheretina

– Considering“Aversionresponse(blinking)”:5mWbeamistolerable

– Above10mW:Blinkingisnotenough.thepotentialhazardfromgeneraluse

– Around100mW:Causeachangetotheretinawhichcanbedefinedasaneyeinjury

Eye hazards. EyeHazards

• Effectsofdifferentwavelengthsontheeye

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Eye hazards.

Ultraviolet Light

EyeHazards

Infrared Light

• Visible(400nm– 780nm)andnearinfrared(780nm– 1400nm)

Eye hazards.

Visible : Blink reflex (up to 1mW)                     NIR : No natural protection

EyeHazards

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Eye hazards. EyeHazards

• Cataracts

Eye hazards. EyeHazards

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• Cataracts

Eye hazards. EyeHazards

• Photokeratitis (“welder’sflash”or“snowblindness”)

‐ Sunburnofthecornea

‐ Usuallycannotnoticeuntilseveralhoursafterexposure

‐ Symptoms:Tear,pain,likehavingsandintheeyes

Eye hazards. EyeHazards

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Skin Hazards. SkinHazards

• Skinisthelargestorganofthebodyand,assuch,isatthegreatestriskforcomingincontactwiththelaserbeam.(hands,head,orarms)

• Lasereffectsontissuedependonthepowerdensityoftheincidentbeam,absorptionoftissuesattheincidentwavelength,timethatbeamisheldontissue,andtheeffectsofbloodcirculationandheatconductionintheeffectedarea.

• Around150mW:canbefeltontheskin.

• 500mW:beginstoburnskinifthepersoniswithinafewmetersofthebeam.

Skin Hazards. SkinHazards

• ImmediateEffects– Thermalinjury(temperatureelevation)– Photochemicaleffect:sunburn(excessivelevelofUVradiation)

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Skin Hazards.

Only UV has been shown to cause it

Accelerated Skin aging Skin cancer

SkinHazards

• Long‐termdelayedeffects

Skin Hazards.

Wavelength (nm) Possible effects

230~380 (UV‐C, ‐B, ‐A)

Erythema, skin cancer, accelerated skin aging

280~480 (UV‐B,‐A, Visible)

Increased pigmentation

310~400 (UV‐A) Photosensitive reactions

400~600 (Visible) Photosensitive reactions

700~1000 (Infrared) Skin burns, excessive dry skin

Infrared light

‐ Thermal damage (Skin burn)

UV light

‐ Photochemical reactions

(Change in the pigmentation, erythema, skin ca.)

SkinHazards

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BasicBiologicalEffectsofLight

백내장

홍반각막염

LASER safety standards & Hazard classification.

Laser Hazards Classes

‐ Classes are defined by their ability to produce damage in exposed people.

‐ Lasers are classified based on the concept of AEL (Accessible Emission Limits).

AEL (Accessible Emission Limit) = MPE x Area of LA

‐Maximum power or energy that can be emitted in a specified wavelength range 

and exposure time that passes through a specified aperture stop at a specified 

distance.

‐Mathematical Product of MPE and an area factor Limiting Aperture (LA)

‐ Limiting Aperture : Depends on factors such as laser wavelength and physical 

factors like the fully dilated pupil size (7mm) and beam hotspots(1mm)‐ Hotspot : The brightest, central area in the beam

LaserSafetyStandards

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LASER safety standards & Hazard classification.

MPE (Maximum Permissible Exposure) 

‐ The highest power or energy density of a light source that is considered safe.

‐ The MPE is measured at the cornea of the human eye or at the skin, for a given wavelength and 

exposure time. (Usually about 10% of the dose that has a 50% chance of creating damage.)

LaserSafetyStandards

LASER safety standards & Hazard classification.

Classification systems

Hazardclassification

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LASER safety standards & Hazard classification.

ANSI Z136.1

Hazardclassification

LASER safety standards & Hazard classification.

ANSI Z136.1

Hazardclassification

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LASER safety standards & Hazard classification.

FDA/CDRH & IEC 60825

Hazardclassification

LASER safety standards & Hazard classification.

FDA/CDRH & IEC 60825

Hazardclassification

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LASER safety standards & Hazard classification.

Eye Protection

Optical density – how much incoming light is absorbed by a lens

→ H0: the anticipated worst case exposure

Ex) Nd:YAG laser, wavelength : 1064nm, output : 80mJ, 

MPE : 5*10‐6 J/cm2, limiting aperture : 7mm 

LaserProtection

LASER safety standards & Hazard classification.

Eye Protection

LaserProtection