Test Questions Flashcards
The same lens will focus different __________ to different ____________
wavelengths , focal lengths
What are the laser operator functions?
ensure policies are followed such as: signs on doors and windows covered, glasses available and worn in NHZ, aiming beam checked for alignment with surgical beam in EVERY case.
Wavelength: ArFi Excimer
193nm
Because different wavelengths will have different focal lengths through the same lens, the ______________ and the _______________ maybe dramatically different sizes on the tissue.
surgical beam , aiming beam
Degraded dye solution can show up in what ways when operating the laser?
Lower energies, misfires, and wavelength instability
How many optics should you clean, remove, or adjust at one time?
one
What are the ANSI documents relevant to our industry?
136.1 parent technical document and 136.3 safe use of lasers in health care facilities.
Wavelength: Argon
488nm and 515nm
Wavelength: nd:YAG
1064nm or 1.064u
Wavelength: nd:YAP
1.34u
Wavelength: Er:YAG
2.94u
What is typical laser divergence?
0.5-10 milliradians
How much amp draw does a typical Ion Laser power supply have?
30-50 amp draw
Ho:YAG lasers typically display and measure energy in what unit?
joules
What is an example of a use for CW dye lasers?
photodynamic treatment for cancer
What wavelengths of light can transmit through glass?
300nm to 2800nm
How often are diode lasers calibrated?
annually
In focusing handpieces for incisions/ablations, the shorter the focal length the ___________ the spot and the __________ the depth of field.
shorter and smaller
What is shock wave used for in pulse dye laser (green)?
urology - lithotripsy
What is thermal, non lethal heat used for from laser?
Tissue welding, skin rejuvenation
What does ANSI require when laser plume is created?
smoke evacuator
Wavelength: KTP/KDP
532nm
Wavelength: Copper bromide
577nm, 511nm
Wavelength: pulsed dye, vascular
594nm
When brewster windows are now kept clean, what is the result in Ion lasers?
Power loss
How often should your external meter be sent in for calibration to a national standard?
annually
In multiline lasers _____________ is the sum of all wavelengths when they may be emitted simultaneously.
max power output
In aligning a q-switch ophthalmic yag laser, because of the location of the target, what must be avoided?
pitting of the lens that sits against the capsule
Describe articulated arm alignment process.
Place tape mark on aim beam, then rotate 180 degrees and observe.
Adjust beam 1/2 way to mark, and continue back and forth until corrected.
Never adjust directly to center
CW Dye lasers use what as a power supply?
Incoming beam from an Argon or KTP laser.
Radiant exposure or energy density is measured in _________
j/cm2
What kind of meter is used to measure wavelength stability in a CW dye laser?
monochrometer
What is the most common crystal for frequency doubling?
KTP (Potassium Titanyl Phosphate), but KDP or others possible
What interior component is the greatest hazard to service people?
Power supply
What is combine to create the dye solution in dye lasers?
dye concentrate, antifreeze (ethylene glycol) carrier along with C.O.T.
What can mimic a failing flash lamp?
Bad D.I. water
What is adjusted to find peak power?
OC and HR mirrors are walked as a pair to find peak power.
How does an AR coating work?
works by destructive interference pattern
Why are laser repair technicians at greater burn and exposure risk?
They are exposed to open housings
Class 4 lasers are anything…
over 0.5W average power or anything that burns the skin and eye.
What can sometimes stop flow in water pumps and how is it corrected?
Vapor locks, purge lines
Which direction does the coating face, how is that determined, and what are the consequences if it is in the wrong direction?
The coating faces the incoming beam. It is identified by the V or seeing the backside edge at a critical angle. Placing them in the wrong direction can reduce power or destroy proximal optics.
All other things equal, smaller focal length lens results in what?
Smaller spot and smaller depth of field
What guidelines are used for enforcement by OSHA, JCAHO, and various state agencies?
ANSI
What axis are used to align Ophthalmic Ar or Kr lasers into fiber?
x, y, z
Define the Maximum Permissible Exposure (MPE)
maximum exposure limit for eyes and skin before a burn will occur.
Explain how Nd:YAG, KTP, Argon, etc (other than CO2 and Er:YAG) lasers measure internal power and provide readout during use?
beam splitter creates a small optical “shunt” into the meter, so the meter reflects actual value during use.
What is “harder” on optics in terms of wavelengths and energy pusles?
higher energy pulse and shorter wavelengths
What does dichroic filter allow for?
selective transmission of wavelengths
Wavelength: XeCl Excimer
308nm
What are the power supply characteristics of flowing gas and DC excited sealed tube lasers?
high voltage and low current: 15-20kv and 15ma
How many shots pulsed is the typical life of a flashlamp?
150K to 250K
Wavelength: Ruby
694nm
What is the active medium in CO2 lasers?
CO2
What is a symptom of deionizer cartridge/crystals deteriorating?
power losses or intermittent firing
What is the process called that makes surgical instruments black to reduce reflections?
ebonization
What is the “far” beam alignment?
The beam combiner which passes surgical laser and reflects the HeNe aiming beam.
In a flowing gas CO2 laser vacuum system, what does higher vacuum create?
Thins out the molecules and lowers max power output, but increases stability at low power outputs.
What is the fastest way to change power density in the laser?
Spot size
How many hours is the typical life of a flash lamp in a CW laser?
150-200 hours
Are ANSI recommendations law?
No
What is the range of visible light in nm?
400nm - 700nm
At their maximum, can longer or shorter wavelengths be focused to a smaller spot size?
shorter wavelengths
Repeated start up attempts and a “cracking” noise can be a symptom of what?
gradually failing flash lamp
Should optics be removed to be cleaned?
not if it is safe to clean them in place.
why are collimated handpieces considered a hazard at a distance?
They will keep their spot size regardless of distance.
How are flash lamps cooled?
A flow tube is used to direct water tightly around the lamp for cooling.
At full operational power, what is the best indication of tube condition in an Ion Laser?
power or current, a combination of both is best.
In CW dye lasers, ______________________ are required to measure energy from many types of diffusers.
Spherical integrators
How do you work the near/far adjustment into alignment?
Alternate between near and far, bringing the HeNe back on top of burn spot each time
Laser output calibrations are recommended how often?
annually
Class 4 lasers require what precautions in what areas?
All precautions required in the NHZ
Increasing the beam diameter (and lens) at the same focal length will result in what?
Smaller spot
Why is depth of focus important when aligning beam into fiber?
You want to cover as much of the face of fiber as possible to avoid small point that bruns it.
What is the active medium in Ruby lasers?
chromium ions
What is the active medium in KTP laser?
neodymium
In a multiline laser, a single line emission will have more or less power output than the maximum multiline power?
less
List the components of an Ion laser tube.
-Ceramic or glass bore (tube).
-Surrounding magnet to “squeeze” the ionized plasma into the middle of the bore.
-anode and cathode
-“Getter” which pulls out impurities such as hydrogen which may be in the tube
-Brewster window at each end to seal the tube.
Describe the rear mirror in of the lasing medium?
Highly reflective mirror, isolated from the optical train. Can be adjusted independently.
What do ion lasers have to prevent overheating? What do they do when overheating occurs?
Ion lasers have overheat sensors (thermistors) that will shut the unit down.
When measuring average power at 10hz, how do you calculate the J/pulse?
divide by 10
Pulse energy in Joules x rate (PRR) =
an average power in watts
In flowing gas CO2 laser, what is intermittent firing, especially at low levels, potentially a sign of?
Vacuum leak
In a CO2 laser, what is the laser gas mixture?
Mostly helium (He), some nitrogen (N2), and least of all CO2. The N2 gives it the characteristic pink/purple color.
Who is the father of lasers in medicine?
Dr. Goldman
What is purge gas in a CO2 laser and what does it do?
Compressed air or bottled nitrogen, which is filtered and used to keep smoke off the lens.
What are the units of measurement for electromagnetic “radiation”?
angstrom, nanometer, or micrometer. 5320A = 532nm =.532u
Why should eye protection be worn when handling flash lamps?
pressurized and can explode
Higher Flux in laser pulses results in what for applications such as hair removal, skin resurfacing, vascular treatment, fine incisions, etc?
Less thermal spread from intended target
What problems develop if Dye lasers sit unused for too long?
coating of the dye and solvent on the optics and tubes
CW lasers generally display and measure energy in what unit?
watts
CO2 lasers typically display and measure energy in what unit?
watts
What is the cause of a beam that is easily controlled but causes charring, burning, and scarring in tissue?
Power density too low
List multiline laser types.
Argon, Krypton, CuBr
Wavelength: Alexandrite
755nm
Wavelength: Diodes
~530nm - 1500nm
Who determines the frequency of RF excited CO2 lasers?
manufacturer
How do some lasers reduce dust on brewster windows?
Protective covers with pressurized gas flow
In Ho:YAG lasers, what is used to protect laser optics from fiber fragments when exploded?
Blast shield
What is shock wave used for in Ho:YAG laser?
Urology, lithotripsy
What is the most common frequency doubled in lasers?
nd:YAG 1064nm to 532nm
Why does higher average power not necessarily mean a more powerful impact?
because average power is energy in joules x rate. A low energy at a high rate can have a higher average power than a high energy at a low rate.
What alignment is closest to HeNe and is reflective?
“near” beam adjustment
Argon lasers typically display and measure energy in what unit?
watts
Why do high energies have lower maximum rate?
They require longer recovery time
What can be said about power density if the cut is clean but uncontrollable?
Power density is too high
Wavelength: CO2
10.6u (micrometers)
What type of light is produced by a CW dye laser?
CW 630nm red light
What are indirect laser hazards?
Laser plume
Electrical (greatest hazard to repair tech, including direct beam)
Dyes and Solvents
Laser gases
Who invented the first Ruby laser?
Ted Maiman
Why can’t sapphire contact tips or urological side firing fibers be fired into calibration port?
They will burn up
What does the Birefringent Tuner in a dye laser use to select wavelength?
dichroic filter in resonator cavity
What laser is the greatest burn hazard to laser technicians?
Co2 lasers
What is the partially reflective optic at the beginning of the optical train?
Output Coupler
1.5 Joules at 10hz will show as _____W average power. (or _____ J in one second)
15W or 15J
What is low level light therapy used for? (photobiomodulation)
chronic pain treatment, hair growth, wound healing, skin rejuvenation, etc. Also called cold therapy
When is radiant exposure / energy density used as a measurement?
When a “dosage” parameter of the laser is required, also used in IPLs
In aligning a q-switch ophthalmic yag laser, explain how the spark and red dot are aligned using the X, Y, and Z axis?
The red dot and spark are aligned on the X and Y axis. On the Z axis, the spark is placed just behind the red dot in the Z axis (depth) so that the dot focuses on the capsule and the spark occurs just behind it to create a shock wave that rips the membrane but spares the lens.
1W at .2s (.2J) is lower or higher flux than 2W at .1s (.2J)
lower flux (less energy more time)
In aligning a q-switch ophthalmic yag laser, the __________ is that target, which sits right against the new lens.
capsule
What are the typical power supplies of CO2 lasers?
Flowing gas and DC excited sealed tube or RF excited
How is AR coating calculated?
Coating is 1/4 of the wavelength of beam?
Ophthalmic diode lasers typically display and measure energy in what unit?
milliwatts
In flowing gas CO2 laser, what does excessive vacuum cause in anode and cathode?
Causes arcing and potential damage to laser electronics
What is the active medium in Ho:YAG?
holmium
List in order the hierarchy of laser eye hazards:
Pulse dye Yellow - high peak power and absorption by retina.
Infrared lasers - no aversion response
Visible light lasers - aversion response
CO2, Er:yag, and ArFl lasers - have lenses that focus short distance. Corneal hazard.
Ho:YAG - because of divergent fiber. Corneal hazard
Proximal changes affect all optics in which direction?
all “downstream” optics
What is the active medium in diode lasers?
the semiconductor
Lasers that operate at 632nm
Helium-Neon (HeNe), Gold Vapor, CW Dye (PDT)
What is the polarity of an anode vs cathode?
anode is negative and cathode is positive
How is RF transmitted in laser cavity?
transversely across cavity
Name the properties that make laser light different from “normal” light?
Collimated, coherent, monochromatic
What lasers don’t transmit through glass?
CO2, Er:YAG, ArFl
Wavelength: Pulsed dye green, lithotripsy
604nm
How are transmitting fibers that diverge at 10-20 degrees used on tissue?
can touch tissue or be used off tissue
How should flash lamps be cleaned?
Clean like an optic, never rub rigorously
What is the primary reason for overheating in Ion lasers?
Forgetting to turn on the external water source
What is the formula for angular measure?
ratio of the arc length on the circumference of a circle by that angle, divided by its radius
What liquid is used in CO2 cooling systems?
distilled water, sometimes antifreeze solution if transported in cold environments.
Passbank currents or voltage regulation are characteristic of what kind of laser power supply?
Ion Lasers
How does anodizing surgical equipment reduce reflections?
It creates a micro-rough surface.
Most surgical diode lasers typically display and measure energy in what unit?
watts
What does the Maximum Permissible Exposure determine?
Boundaries for the NHZ
How much does lens of eye increase power density?
100,000
What are direct beam hazards?
eye burns or damage
skin burns
fires or burning of material
accidental surgical perforations
RF excited CO2 lasers measure their power in _______.
watts
Dichroic filters placed inside the resonator cavity will do what?
Allow lasing of only that wavelength.
What happens if Argon and Krypton lasers sit for too long unused
overgassing, use weekly
Define flux
concept of delivering more energy in shorter time periods to reduce thermal spread
How does beam diameter impact divergence? (all other things equal) on test for sure
The larger the diameter of the beam the lower the divergence.
List the ANSI recommendations for service training:
must have laser safety training
must have laser repair training commensurate with the level of work
no requirement for any educational background or certification
no requirements for authorization or approval from manufacturer
Wavelength: Krypton
647nm, 568nm, 531nm
What is the formula to calculate Joules?
watts x seconds = Joules
Is laser radiation a risk to pregnant women?
No, and this is on the test.
What are attenuators used for in lasers?
-aiming beam brightness
-some sealed tube CO2 lasers because they are unstable at very low currents
What is the spot size range in ophthalmic argon lasers?
~50u to .5mm
Pulsed dye lasers typically display and measure energy in what unit?
joules
In a flowing gas CO2 laser vacuum system, what does insufficient vacuum allow?
Allows more molecules in tube and higher power output, but becomes stable at low powers.
What laser has no optical assemblies except for delivery optics, and no optical adjustments? (it either works or does not)
Diode laser
In a 3 phase pump such as older nd:yag lasers, what does the polarity control?
direction of motor rotation
Ion Laser power supplies are powered by what kind of line voltage and at what voltage?
rectified AC line voltage ~240V
Frequency doubling in “quasi continuous” pulse systems operate at high frequencies over ________khz
20Khz
What is the required sequence of alignments in any laser?
Power tweaking, aiming beam coincidence, delivery system
Diode lasers are used as the pump source on some of these types of lasers?
Solid state
In free beam lasers (fibers or focused) what is generated when light is absorbed into tissue?
Heat is generated
If a CO2 laser completely stops working, and the tube lights up more purple/pink than normal, what is the likely problem?
A mix up of the purge gas and the laser gas. (tank swapping). Won’t hurt the laser.
What are AR coatings used for?
Used to increase efficiency of optical coupling into optic and reduce losses
“Contact” fibers that have sharp or ball tips are used in what manner?
They get hot and cut tissue.
What is thermal, destructive heat used for with lasers?
cutting, ablating, photocoagulation, aesthetics, selective photothermolysis
You can use a power meter head to measure a pulsed laser by adjusting what?
repetition rate
What is the purpose of a Brewster Window?
enhances transmission (reduces reflection)
What can happen if water supply is turned on suddenly after overheating of an Ion laser?
cold water can crack the turb and cause extensive damage.
How do sapphire contact tips work?
Added to the end of the fiber catheter that converts the light energy into heat and work almost exclusively as a “hot knife”.
What is the most important property of laser light in medical use? (on the test for sure)
Collimation because this is a “point source” of light with rays travelling parallel. Optics will focus this down to diffraction limited spot sizes (very small spots)
What is the biggest problem in CO2 cooling systems and what is done for it?
algae growth, change water and add inhibitors
What is indicated by an Ion laser tube having too low of voltage?
tube is underpressure. Fill from reservoir -ballast tank - with caution to not overfill.
In a 3 phase pump such as older nd:yag lasers, what happens if the polarity is reversed?
The pump spins the impellor in the wrong direction, possibly shearing it from the shaft and stopping water flow.
Pulsed lasers typically display and measure energy in what unit?
Joules or millijoules
In sterile procedures, what must be done for the calibration of a fiber?
sleeve sterilized and fiber handled with sterile gloves
At 1 milliradian, a spot would increase by ______ for every 1000 feet in distance travelled.
1 foot
What is the unit of measurement of beam divergence?
radian
What is “shock wave” used for in q-switched Nd:YAG lasers?
In Ophthalmology for posterior capsulotomy, and for tattoo removal
What is the active medium in Argon/Krypton lasers?
Argon and Krypton gasses
How large should the spot be on the laser meter/detector?
Fill about 75% of the face of the detector
Q-switched ophthalmic nd:YAG lasers (pulsed dye green for lithotripsy) typically display and measure energy in what unit?
millijoules
Explain how CO2 and Er:YAG lasers measure internal power and provide readout during use?
they use a shutter to totally dump the beam into calorimeter, during use the reading is only memory or current.
What wavelengths are retinal hazards?
between 400nm and 1400nm (includes all visible light lasers)
What is indicated by an Ion laser tube have too high of voltage?
tube is overpressure, burn off is needed.
What lasers are brewster windows typically used in?
Ion lasers: Argon and Krypton
List and describe the desired order of optic cleaning:
Drop and drag - sheet of lens paper
Twist and wipe - folded paper in hemos
Roll and wipe - cotton tip applicator
Rub and Scrub - cotton tip applicator
What angle are brewster windows?
57.3 degrees (for quartz) - where the surface does not reflect the light of one linear polarization.
Wavelength: Ho:YAG
2.1u
Because different wavelengths will have different focal lengths through the same lens, it can cause a loss of ______________ between the aiming and surgical laser.
coaxialness
How much variance is acceptable in laser output calibration?
+/-20%
