31 - 208 - FUNDAMENTALS OF LASER AND LIGHT-BASED TREATMENTS

Question 1

Which laser can be used for telangiectasias?

a. Diode

b. Er:YAG

c. Ruby

d. Argon

Answer 1

D

Question 2

For large vessels and hair removal, which laser setting is best?

a. Nd:YAG; Selective coagulation; pulsed (ms)

b. Nd:YAG; Fast heating; pulsed (ns/ps)

c. Nd:YAG; Selective coagulation; pulsed (ns/ps)

d. Nd:YAG; Fast heating; pulsed (ms)

Answer 2

A

Question 3

What creates evenly distributed zones of microthermal injury in skin to produce columns of injury in the epidermis and dermis, leaving intervening columns of unaltered skin, thereby decreasing healing time and minimizing adverse effects?

a. Selective Thermolysis

b. Fractional Thermolysis

c. BOTH

d. NEITHER

Answer 3

B

Question 4

Which is NOT a main parameter of Optical Radiation?

a. optical power

b. fluence

c. intensity

d. all of the above are included

Answer 4

D

Question 5

The major chromophores in skin in order of depth of location are?

a. water-melanin-hemoglobin

b. melanin-water-hemoglobin

c. hemoglobin-water-melanin

d. hemoglobin-melanin-water

Answer 5

A

Question 6

Question 7

main parameters of optical radiation

Answer 7

wavelength,
optical power,
intensity,
the exposure time and
radiant exposure or fluence

Question 8

The spot size and the energy of the laser beam determine the

Answer 8

radiant exposure (J/cm2)

Question 9

most frequently modified parameter in laser treatments

Answer 9

radiant exposure or fluence (J/cm2)

Question 10

described as the conversion of laser energy to heat when its photons strike the target chromophore

Answer 10

Absorption

Question 11

occurs when the laser beam strikes the surface at an oblique angle and a portion of the beam bounces off the surface in a different direction

Answer 11

Reflection

Question 12

Because of the inherent reflective property of the stratum corneum, even laser beams perfectly perpendicular to the skin undergo about _____% reflectance

Answer 12

5%

Question 13

occurs when the light passes through the stratum corneum, but deviates once in the tissue due to contact with small molecules in the skin

Answer 13

Scattering of laser

This process is more likely to occur with shorter wavelengths

Question 14

occurs when the beam is not absorbed by the target chromophore and is conducted to deeper structures

Answer 14

Transmission

Question 15

This laser-tissue interaction is more likely to occur with shorter wavelengths

Answer 15

Scattering

Question 16

This laser-tissue interaction is more likely to occur with longer wavelengths and larger spot sizes

Answer 16

Transmission

Question 17

When laser or IPL light is absorbed by a chromophore, what types of interactions ensue

Answer 17

• chemical (photochemical),
• mechanical (photoacoustic or photodisruptive), or
• thermal

Question 18

An example of a this effect is the use of low-level laser therapy in the treatment of hair loss, in which photons are presumed to be absorbed by mitochondria and activate the cellular respiratory chain to induce hair growth

Answer 18

chemical (photochemical) effect

Question 19

This effect can be exemplified by the use of nanosecond or picosecond lasers in the treatment of pigmented lesions and tattoos: high-energy photons absorbed by pigment generate acoustic waves within the particles leading to their break up

Answer 19

mechanical (photoacoustic or photodisruptive)

Question 20

the mechanism on which most lasers rely, describe the transformation of light energy into heat when absorbed by a chromophore, causing direct damage to adjacent cells, tissues, and structures

Answer 20

Photothermal effects

Question 21

Lasers that preferentially interact with oxyhemoglobin

Answer 21

• neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm frequency doubled to 532 nm)
• pulsed dye lasers (585–600 nm)

Question 22

These lasers are less well absorbed by oxyhemoglobin and more suitable for pigmented chromophores in benign pigmented lesions and for hair removal

Answer 22

• ruby lasers (694 nm),
• alexandrite lasers (755 nm),
• diode lasers (around 810 nm)

Question 23

Radiation of this laser is minimally absorbed by all skin chromophores.

Answer 23

Nd:YAG laser (1064 nm)

Nevertheless, at high radiant exposures, this laser can be used for nonspecific coagulation of tissue as a continuous wave, or for pigmented or vascular lesions as a short or long pulse.

Question 24

lasers that interact solely with water heating up tissue for vaporization or ablation.

Answer 24

Infrared lasers such as the erbium-doped yttrium aluminum garnet (Er:YAG) and carbon dioxide (CO2 )

These ablative lasers induce thermal damage to the epidermis and dermis to stimulate neocollagenesis, tissue rejuvenation, and skin tightening.

Question 25

Question 26

At temperatures ________, reversible thermal damage, local vasodilation, and inflammatory cascade activation are produced

Answer 26

below 50°C

Question 27

At temperatures _________, tissue and its proteins undergo irreversible coagulation or denaturation

Answer 27

between 50°C and 100°C

Question 28

At temperatures ____________, tissue vaporization occurs, generating plume containing water vapor and tissue components

Answer 28

greater than 100°C

Question 29

defined as the time needed for the irradiated tissue to cool down to half of its heated temperature

Answer 29

thermal relaxation time ## Footnote * The keys to this theory are twofold: laser light must be absorbed by the target by selecting a wavelength absorbed by the chromophore in the target, and the correct pulse duration is essential for spatial confinement of heat in the target. * The pulse duration should be comparable to the thermal relaxation time (tR ), which mainly depends on the diameter of the target (D)

Question 30

The major chromophores in skin in order of depth of location are

Answer 30

water, melanin, and hemoglobin

Question 31

What lasers are absorbed by water

Answer 31

CO laser (10,600-nm) Er:YAG laser (2940 nm)

Question 32

Lasers that may be absorbed by both hemoglobin and melanin

Answer 32

* Argon-ion lasers (488 and 514 nm), * KTP lasers (532nm), and * pulsed dye lasers (585-595 nm)

Question 33

absorbed mainly by melanin pigment although a small amount of hemoglobin absorption also occurs

Answer 33

Ruby lasers (694 nm)

Question 34

preferentially absorbed by melanin, and therefore useful for pigmented lesions and hair.

Answer 34

Alexandrite lasers (755 nm)

Question 35

although there is no specific chromophore, this wavelength is absorbed, albeit less than with other visible wavelengths, by hemoglobin and melanin and at higher fluences it can be used to treat pigmented or vascular lesions.

Answer 35

Nd:YAG laser (1064 nm)

Question 36

determines the size of target that will be selectively damaged.

Answer 36

pulse duration

Question 37

Answer 37

correction: Hair follicles are 0.02 to 0.2 millimeters in diameter and not micrometer

Question 38

Hair follicles are 0.02 to 0.2 millimeters in diameter and are targeted by pulses in the range of _______

Answer 38

10 to 50 milliseconds

Question 39

Melanocytes are a few µm in diameter (average 7 µm) and require pulse widths ranging from

Answer 39

milliseconds to nanoseconds

Question 40

Melanosome diameter ranges from 1 to 1.5 µm and can be targeted by what pulse duration

Answer 40

nanosecond and picosecond pulses

Question 41

Tattoo pigment particles are on average 100 nanometers (0.1 µm) in diameter and are targeted by what pulse durations

Answer 41

nanosecond and picosecond pulses

Question 42

Question 43

Question 44

Radiation between 380 and 1400 nm is transmitted by the eye and absorbed by what structure in the eye

Answer 44

Retina Light of wavelengths longer than 1000 to 1400 nm is readily absorbed by water, does not penetrate deeply, and therefore may cause corneal injury, even ablation or vaporization, by a thermal process.

Question 45

Photons of wavelengths shorter than 380 nm are absorbed by organic molecules in what part of the eye

Answer 45

Cornea, thereby causing injury or cataract formation.

Question 46

Thermal damage occurs when energy is absorbed by the chromophore, such as melanin in the retina, at a pulse ranging from

Answer 46

microseconds to seconds Heat is generated faster than it can be dissipated, thereby denaturing proteins resulting in cell death and tissue necrosis.

Question 47

Mechanical injury is caused when energy is rapidly absorbed at pulse durations ranging from

Answer 47

picoseconds to nanoseconds

Question 48

Laser goggles are rated by optical density (OD) at various wavelengths, and an OD of at least _____ is considered safe.

Answer 48

4

Question 49

part of laser that is used to bring atoms and electrons to an excited energy state, and can take the form of an electrical current, flashlamp, or even another laser

Answer 49

energy source

Question 50

part of laser composed of a medium enclosed within a tube that contains 2 parallel mirrors, one of which is completely opaque and the other is partially transmissible

Answer 50

resonator

Question 51

this determines the resultant wavelength and properties of the laser

Answer 51

medium ## Footnote can be a solid, liquid, liquid crystal, or gas

Question 52

Question 53

Question 54

pulse duration that should be used for blood vessels

Answer 54

ms

Question 55

pulse duration that should be used for hair follicles

Answer 55

10 - 50 ms

Question 56

pulse duration that should be used for melanocytes

Answer 56

ms to ns

Question 57

pulse duration that should be used for melanosomes

Answer 57

ns to ps

Question 58

pulse duration that should be used for tattoo pigment particles

Answer 58

ns to ps

Question 59

where heat is transferred from the warm skin to the cooling agent

Answer 59

contact cooling

Question 60

regulatory document that provides guidance for the safe use of lasers in medicine

Answer 60

ANSI Z136.3

Question 61

laser settings that decrease the risk of injury to darker skin types

Answer 61

Lower fluences, longer pulse durations, and longer wavelengths or higher cutoff filters

Question 62

Radiation between **380 and 1400 nm **is transmitted by the eye and absorbed by what part of the eye?

Answer 62

retina ## Footnote * The refractive media of the eye gathers and focuses this spectrum onto the retina and increases the irradiance by a factor of more than 10,000 above the irradiance at the cornea. * Thus, even a small amount of energy from low-power lasers can still inflict significant damage on the retina.

Question 63

caused when energy is rapidly absorbed at pulse durations ranging from **picoseconds to nanoseconds**

Answer 63

Mechanical injury ## Footnote * A rapid absorption of energy and therefore rapid increase in temperature strips electrons from atoms, disintegrating tissue to a pool of ions and electrons, or plasma * Concomitant vaporization of water results in a compressive pressure pulse, or explosion, that disrupts surrounding tissue.

Question 63

Photons of **wavelengths shorter than 380 nm** are absorbed by organic molecules in what part of the eye?

Answer 63

cornea ## Footnote * thereby causing injury or cataract formation * Light of wavelengths longer than 1000 to 1400 nm is readily absorbed by water, does not penetrate deeply, and therefore may cause corneal injury, even ablation or vaporization, by a thermal process

Question 63

occurs when energy is absorbed by the chromophore, such as melanin in the retina, at a pulse ranging from **microseconds to seconds**.

Answer 63

Thermal damage ## Footnote * Heat is generated faster than it can be dissipated, thereby denaturing proteins resulting in cell death and tissue necrosis

Question 64

results from energy at relatively lower levels and longer pulse durations, more than a few seconds

Answer 64

Photochemical damage ## Footnote * The slow delivery of energy does not deliver enough heat to induce thermal damage. However, single photons can break molecular bonds in nucleic acids and proteins. * Retinal cells can recover from this type of damage over a period of weeks, but over a certain threshold damage can be irreversible

Question 65

important parameters of the radiation sources

Answer 65

wavelength, pulse duration, intensity, and radiant exposure ## Footnote * These parameters of a laser or IPL system determine the characteristics of the safety goggles.