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Fitzpatrick's Dermatology, 9th Edition (Entrance Exam / Board Exam Prep) > 208: Fundamentals of Laser and Light-Based Treatments > Flashcards

208: Fundamentals of Laser and Light-Based Treatments Flashcards

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1
Q

What are the key differences between laser light and intense pulsed light (IPL)?

A

Laser light is monochromatic, coherent, and collimated, while intense pulsed light (IPL) is polychromatic, broadband, and divergent.

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2
Q

What is selective photothermolysis and its significance in laser treatments?

A

Selective photothermolysis allows lasers to target specific chromophores in the skin, achieving desired effects while minimizing injury to surrounding tissues.

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3
Q

How does fractional photothermolysis work and what are its benefits?

A

Fractional photothermolysis creates microthermal injury zones in the skin, producing columns of injury while leaving intervening areas unaltered. This approach decreases healing time and minimizes adverse effects.

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4
Q

What is the role of the resonator in a laser device?

A

The resonator is composed of a medium enclosed within a tube with two mirrors. It amplifies light by allowing photons to bounce back and forth, increasing their number exponentially before exiting as a laser beam.

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5
Q

What are the unique traits of laser light compared to natural light?

A

Laser light is monochromatic, coherent, and collimated, which allows it to travel longer distances with minimal loss of intensity and enables selective absorption by specific chromophores.

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6
Q

What happens during the stimulated emission of photons in a laser?

A

When an electron in an excited state encounters a photon of the same energy, it releases another photon of the same wavelength, leading to a chain reaction that exponentially increases the number of photons.

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7
Q

What is the significance of the term ‘inversion’ in laser operation?

A

Inversion refers to the condition when the number of excited atoms exceeds the number of atoms in the ground state, which is necessary for the amplification of light in a laser.

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8
Q

How does the energy of a photon relate to its frequency and wavelength?

A

The energy of a photon is proportional to its frequency and inversely proportional to its wavelength, described by the equation: E = hν = hc/λ.

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9
Q

What are the key properties of laser light that distinguish it from natural light?

A

Laser light is monochromatic, coherent, and collimated, allowing for selective absorption, minimal divergence, and dense energy packing.

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10
Q

What is the significance of spot size in laser treatments?

A

Larger spot sizes allow deeper penetration into tissue and reduce scattering, enhancing the effectiveness of the treatment.

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11
Q

What is the significance of the electrical voltage applied to the crystal in achieving short pulse durations in laser technology?

A

The electrical voltage applied to the crystal changes the polarization of the photons, which prevents them from oscillating back and forth inside the resonator. This minimizes stimulated emission and allows for a high number of excited atoms or molecules, leading to intense laser pulses with durations in the range of nanoseconds to picoseconds.

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12
Q

How does Intense Pulsed Light (IPL) technology differ from traditional lasers?

A

IPL devices produce noncoherent light from a flashlamp, covering a broad spectrum of wavelengths that can be tuned for different treatments. In contrast, traditional lasers emit coherent light at specific wavelengths.

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13
Q

What are the main parameters of optical radiation that influence laser treatments?

A

The main parameters of optical radiation are: Wavelength, Optical Power, Intensity, Exposure Time, Radiant Exposure (Fluence). These parameters determine the energy delivered to the skin and the effectiveness of the treatment.

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14
Q

What role do articulated arms play in laser energy delivery?

A

Articulated arms facilitate the delivery of laser energy from the optical resonator to the tissue by transferring energy through a series of hollow, interconnected tubes with reflecting mirrors.

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15
Q

What are the advantages of fiber lasers compared to traditional laser systems?

A

Fiber lasers offer several advantages: High Efficiency, Compact Design, Flexibility, Reliability.

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16
Q

What is the purpose of using cutoff filters in IPL devices?

A

Cutoff filters tune the broad spectrum of IPL light to specific wavelengths, allowing only desired wavelengths to pass through for targeted treatment.

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17
Q

What is the mechanism of action of Q-switched lasers?

A

Q-switched lasers produce very intense laser pulses in the nanosecond to picosecond range by temporarily blocking photon oscillation, allowing maximum excitation of atoms before release.

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18
Q

What is the significance of radiant exposure (fluence) in laser treatments?

A

Radiant exposure, the product of light intensity and exposure time, is the most frequently modified parameter in laser treatments.

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19
Q

What are the four different responses that may occur when laser light reaches tissue?

A
  1. Reflection 2. Transmission 3. Absorption 4. Scattering
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20
Q

How does the absorption of laser light affect its interaction with tissue?

A

Absorption converts laser energy to heat when photons strike the target chromophore, leading to thermal effects in the tissue.

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21
Q

What is the significance of reflection in laser treatments, and what safety measure is necessary?

A

Reflection occurs when the laser beam strikes the surface at an oblique angle, necessitating the use of safety goggles to protect the eyes.

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22
Q

What happens to tissue when laser light is transmitted without absorption?

A

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

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23
Q

What are the effects of high-energy photons absorbed by pigment in the treatment of pigmented lesions?

A

High-energy photons generate acoustic waves within the particles, leading to their breakup.

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24
Q

What is the relationship between pulse duration and tissue vaporization in laser treatments?

A

Higher power and shorter pulse duration result in more tissue vaporization and less surrounding coagulative necrosis.

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25
What temperature range leads to irreversible coagulation of tissue during laser treatments?
At temperatures between 50 °C and 100 °C, tissue and its proteins undergo irreversible coagulation or denaturation.
26
How does the Nd:YAG laser interact with tissue compared to other lasers?
The Nd:YAG laser (1064 nm) is minimally absorbed by all skin chromophores and can be used for nonspecific coagulation of tissue or for pigmented or vascular lesions as a short or long pulse.
27
A patient presents with a pigmented lesion. Which lasers are most suitable for treatment?
Ruby lasers (694 nm), Alexandrite lasers (755 nm), and diode lasers (around 810 nm) are more suitable for pigmented chromophores.
28
What is the primary mechanism by which most lasers achieve their therapeutic effects?
Most lasers rely on photothermal effects, where light energy is transformed into heat upon absorption by a chromophore.
29
What is the difference between photochemical, photoacoustic, and photothermal effects in laser treatments?
Photochemical effects involve low-level energy absorption by mitochondria. Photoacoustic effects involve high-energy photons generating acoustic waves. Photothermal effects involve heat transformation causing tissue damage.
30
What is the relationship between wavelength and penetration depth in laser treatments?
In general, longer wavelengths penetrate more deeply into tissue, but wavelengths longer than 1100 nm are increasingly absorbed by water.
31
What are the effects of laser light on tissue at temperatures below 50°C?
At temperatures below 50°C, reversible thermal damage, local vasodilation, and activation of the inflammatory cascade occur.
32
What is the role of erbium-doped fiber lasers in dermatology?
Erbium-doped fiber lasers (1550 nm) provide precise, efficient, and reliable laser outputs for various dermatologic applications.
33
What is the effect of pulse duration on tissue vaporization and coagulative necrosis?
Shorter pulse durations result in more tissue vaporization and less coagulative necrosis, while longer pulse durations have the opposite effect.
34
What are the risks of using Nd:YAG lasers for deep tissue treatments?
Nd:YAG lasers can generate deep-seated steam cavities, leading to tissue explosion and ulceration.
35
What is the significance of the absorption coefficient in laser treatments?
The absorption coefficient determines how effectively a chromophore absorbs a specific wavelength of laser light.
36
What are the effects of laser light on tissue at temperatures between 50°C and 100°C?
Tissue undergoes irreversible coagulation or denaturation, leading to coagulative necrosis.
37
What is the effect of laser light on tissue at temperatures greater than 100°C?
Tissue vaporization occurs, generating a plume containing water vapor and tissue components.
38
What is the significance of the thermal relaxation time in selective photothermolysis?
The thermal relaxation time is the time needed for irradiated tissue to cool down to half of its heated temperature. It is crucial because the pulse duration of the laser must be shorter than this time to minimize damage to peripheral tissues.
39
What are the major chromophores in the skin and their absorption characteristics?
The major chromophores in the skin are Water, Melanin, and Hemoglobin, each with specific wavelengths and depths of penetration.
40
How does fractional photothermolysis differ between ablative and nonablative modes?
Fractional photothermolysis can be performed in two modes: Ablative involves controlled vaporization of thin columns of both epidermis and dermis, while Nonablative heats concentrated within the dermis, preserving the epidermis.
41
What are the two types of skin cooling methods used during laser treatments?
The two types of skin cooling methods are Contact Cooling (active or passive) and Noncontact Cooling.
42
You are treating a vascular lesion with a laser. What wavelength and pulse duration should you select to minimize peripheral tissue damage?
Use a wavelength absorbed by the chromophore (e.g., 577 nm for vessels) and a pulse duration shorter than the thermal relaxation time of the target.
43
What is the significance of the thermal relaxation time in laser treatments?
Thermal relaxation time is the time needed for irradiated tissue to cool down to half of its heated temperature, ensuring spatial confinement of heat to the target.
44
What is the role of fractional photothermolysis in dermatologic treatments?
Fractional photothermolysis creates spatially distributed columns of microthermal injury in the skin, allowing for controlled denaturation, collagen remodeling, and shorter healing times.
45
What are the advantages of using nonablative fractional lasers over ablative lasers?
Nonablative fractional lasers induce bulk heating of dermal collagen while sparing the epidermis, resulting in fewer side effects and shorter healing times.
46
What is the primary chromophore targeted by CO2 lasers, and what is its wavelength?
CO2 lasers target water as the primary chromophore and have a wavelength of 10,600 nm.
47
What is the role of melanin as a chromophore in laser treatments?
Melanin absorbs specific wavelengths of laser light, making it a target for treatments like hair removal and pigmented lesion correction.
48
What is the relationship between pulse duration and target size in laser treatments?
Pulse duration should match the thermal relaxation time of the target, which depends on its size.
49
What is the role of fractional photothermolysis in drug delivery?
Fractional photothermolysis creates microthermal zones that enhance laser-assisted topical drug delivery.
50
What is the role of melanosomes in laser treatments?
Melanosomes, with diameters of 1 to 1.5 μm, are targeted by nanosecond and picosecond pulses for treatments like pigmented lesion correction.
51
What are the benefits of using a dynamic cooling device (DCD) in laser treatments?
The DCD allows for uniform, precise, and reproducible cooling with every laser pulse, enhancing patient safety and comfort during procedures.
52
What are the common complications associated with dermatologic laser surgery?
The most common complications include cutaneous injuries, which can result in burns, scars, and pigmentary changes.
53
How does the choice of laser affect the risk of cutaneous injuries in patients with darker skin types?
Using lower fluences, longer pulse durations, and longer wavelengths or higher cutoff filters decreases the risk of injury to darker skin types.
54
What factors contribute to ocular injuries from laser light?
Ocular injuries arise from direct or indirect laser light, with 70% resulting from inappropriate or lack of use of eye protection.
55
What is the significance of using safety goggles during laser procedures?
Safety goggles are essential as they are composed of filters that either reflect or absorb specific wavelengths of light, protecting the eyes from harmful radiation.
56
What are the different types of ocular injuries caused by laser exposure?
Ocular injuries can be classified as thermal, mechanical, or photochemical.
57
What is the role of a laser safety officer (LSO) in maintaining laser safety?
The LSO is responsible for ensuring safety protocols are followed, receiving detailed training on laser fundamentals, bioeffects, exposure limits, and implementing safety checklists.
58
A patient with darker skin type is undergoing laser treatment. What parameters should be adjusted to minimize the risk of injury?
Lower fluences, longer pulse durations, and longer wavelengths or higher cutoff filters.
59
What are the types of damage that can occur to the retina?
Mechanical injury results from rapid energy absorption, and photochemical damage occurs at lower energy levels over longer durations.
60
What is the role of a laser safety officer (LSO) in maintaining laser safety?
The LSO is responsible for ensuring safety protocols are followed, receiving detailed training on laser fundamentals, bioeffects, exposure limits, and implementing safety checklists to maintain a safe environment around laser devices.
61
What parameters should be adjusted for patients with darker skin types undergoing laser treatment?
Lower fluences, longer pulse durations, and longer wavelengths or higher cutoff filters should be used to decrease the risk of injury to darker skin types.
62
What safety measures should be taken during a laser procedure to prevent ocular injuries?
Use safety goggles rated with an optical density (OD) of at least 4, specific to the laser's wavelength. Ensure all personnel wear them.
63
What are the risks associated with using ablative lasers, and how can they be mitigated?
Ablative lasers increase the risk of infection and scarring due to epidermal and dermal destruction. Fractionally ablative lasers reduce this risk significantly.
64
What is the role of dynamic cooling devices (DCD) in laser treatments?
DCD sprays cryogen at –15°C immediately before laser application, providing uniform, precise, and reproducible cooling with every laser pulse.
65
What are the potential complications of laser hair removal, and how can they be minimized?
Complications include burns, scars, and pigmentary changes. Use lower fluences, longer pulse durations, and appropriate cooling to minimize risks.
66
What are the safety considerations for patients with pacemakers undergoing laser treatments?
Avoid using devices that employ radiofrequency energy near pacemakers, and exercise caution in areas with tattoos or metal implants.
67
What is the purpose of appointing a Laser Safety Officer (LSO)?
The LSO ensures safety by implementing control measures, training personnel, and maintaining safety checklists.
68
What are the advantages of using noncontact cooling methods in laser treatments?
Noncontact cooling methods, like cryogen spray or forced cold air, provide cooling without interfering with the laser beam.
69
What is the purpose of using sapphire tips in active contact cooling?
Sapphire tips actively remove heat from the skin during laser treatments, providing effective epidermal protection.
70
What is the role of the macula in protecting the eye from laser light?
The macula activates the blink reflex within 150 to 250 milliseconds in response to visible light, providing some protection.
71
What is the significance of the aversion response in laser safety?
The aversion response, or turning away from the light source, is a natural defense against harmful visible radiation but is not rapid enough for most laser systems.
72
What is the effect of the Excimer laser at a wavelength of 308 nm?
The Excimer laser targets DNA and proteins, inducing photochemical reactions. It operates in pulsed mode with a duration of microseconds (µs).
73
What are the applications of the Argon laser with a wavelength of 488/514 nm?
The Argon laser is used for treating vascular lesions and tissue coagulation. Its applications include telangiectases, spider nevi, and venous lakes.
74
How does the Frequency-doubled Nd:YAG (KTP) laser affect vascular lesions?
The Frequency-doubled Nd:YAG (KTP) laser selectively coagulates vascular lesions and operates in pulsed mode with a duration of microseconds (µs).
75
What is the mode of operation for the Ruby laser and its effect on pigmented lesions?
The Ruby laser operates in pulsed mode (ns, ps) and selectively heats pigmented lesions, particularly melanin-containing lesions and tattoos, causing explosion effects.
76
What is the primary use of the CO2 laser in dermatology?
The CO2 laser is primarily used for vaporization of tissue and can also perform selective and fast heating (ablation). It operates in continuous wave mode for vaporization and pulsed mode for ablation.
77
What is the effect of the Erbium glass laser on tissue?
The Erbium glass laser selectively coagulates tissue in a nonablative manner and is used for skin remodeling and photoaging. It operates in pulsed mode (ms).
78
What types of lesions can the Diode laser treat, and what is its mode of operation?
The Diode laser can treat vascular lesions and tissue. It operates in pulsed mode (ms) for large vessels and hair removal applications.
79
What is stimulated emission in the context of laser light production?
Stimulated emission occurs when an excited atom collides with a photon of light of the same wavelength that it previously absorbed, returning to its resting state and emitting two photons of light energy of the same wavelength, traveling coherently and in parallel direction.
80
How does the process of stimulated emission contribute to the amplification of laser light?
In the laser cavity, excited atoms collide with photons of light energy, producing stimulated emission. This process amplifies the light as it reflects back and forth within the cavity, promoting further stimulated emissions and resulting in a coherent laser beam.
81
What are the states of electrons in an atom during the process of laser light production?
Electrons in an atom can exist in two states: the resting state and the excited state. Upon absorption of light energy, electrons transition to the excited state. When they return to the resting state, they can release energy through spontaneous or stimulated emission.
82
What are the key differences between the light emitted by a flashlight and a laser?
A flashlight produces light that is divergent, incoherent, and polychromatic, while a laser emits light that is spatially collimated, coherent, and monochromatic.
83
What are the types of laser-tissue interactions?
The types of laser-tissue interactions include: 1. Reflection - Light bounces off the surface. 2. Transmission - Light passes through the tissue. 3. Scattering - Light is dispersed in different directions. 4. Absorption - Light is taken up by the tissue, leading to various effects.
84
How does the emission spectrum of a typical intense pulsed light (IPL) relate to the absorption of different chromophores?
The emission spectrum of a typical IPL is broad and includes: - 500 nm cut-off: Overlaps with the absorption of oxyhemoglobin. - 650 nm cut-off: Overlaps with the absorption of melanin. This indicates that different filters can target specific chromophores in the tissue.
85
What are the absorption spectra of different chromophores in skin as indicated by various laser wavelengths?
The absorption spectra of different chromophores in skin are as follows: | Chromophore | Wavelength (nm) | Absorption Characteristics | |---------------|------------------|---------------------------| | Oxyhemoglobin | 532, 585 nm | High absorption | | Melanin | 694, 755, 810 nm | Varies, peaks at certain wavelengths | | Water | 11600 nm | High absorption at infrared wavelengths | Different lasers target these chromophores based on their absorption characteristics, which is crucial for effective laser treatments.
86
What are the temperature thresholds for tissue vaporization and thermal damage during laser treatments?
The temperature thresholds for tissue vaporization and thermal damage are as follows: | Temperature Range | Effect | |-------------------|---------------------------------| | >100°C | Vaporized tissue | | 50°C - 100°C | Reversible thermal damage | | <50°C | Reversible thermal coagulation | | >60°C | Irreversible thermal damage | Understanding these thresholds is essential for safe and effective laser therapy.
87
What is the effect of short pulse duration at high power on tissue vaporization compared to long pulse duration at high power?
Short pulse duration at high power results in more tissue vaporization and less surrounding coagulative necrosis, while long pulse duration at high power leads to less vaporization and more coagulative necrosis at the edge of the vaporized tissue.
88
How does longer laser exposure time affect thermal diffusion and collateral thermal injury?
Longer laser exposure time increases thermal diffusion out of the target and can damage adjacent structures. This collateral thermal injury can be minimized by selecting a wavelength that is specifically absorbed by the target chromophore and maintaining a pulse duration shorter than the thermal relaxation time of the target, a process known as selective photothermolysis.
89
What are the approximate sizes and pulse durations for different targets in laser surgery?
| Target | Approximate Size of Target | Pulse Duration | |------------------------|---------------------------|-----------------| | Blood vessels | 50-150 µm | ms | | Hair follicles | 0.02-0.2 mm | 10-50 ms | | Melanocytes | 7 µm | ms to ns | | Melanosomes | 1.5 µm | ns to ps | | Tattoo pigment particles| 100 nm (0.1 µm) | ns to ps |
90
What are the methods of cooling used in cutaneous laser surgery?
| Cooling Method | Type | |------------------------|-------------------------| | Active | Copper, sapphire tips | | Passive | Ice | | Passive | Aqueous gels | | Noncontact | Cryogen spray (liquid nitrogen) | | Noncontact | Pulsed cryogen spray (dynamic cooling device) | | Noncontact | Forced refrigerated air (Zimmer Cryo, Zimmer Medizin Systems, Irvine, CA) |
91
What are the principles of laser safety that should be considered during a procedure?
1. Set patient realistic expectations. 2. Discuss the procedure and possible side effects in detail. 3. Select the correct device for target chromophore and patient skin type. 4. Use lower fluences, longer pulse durations, longer wavelengths, and higher cutoff filters to decrease risk in darker skin types. 5. Precooling, cooling during procedure, and postprocedural cooling are important. 6. Avoid using radiofrequency energy on patients with implantable devices or pacemakers. 7. Use the lowest risk lasers that are vascular, pigment-specific, and nonablative types. 8. Be aware that ablative lasers are higher risk, with greater chances of infection and scarring. 9. Ensure appropriate eye protection is essential and device-specific. 10. Evacuate plumes when using lasers for tissue vaporization to avoid infectious material.
92
What is the significance of wavelength in laser treatments, particularly regarding tissue interaction?
1. Wavelength affects the penetration depth of laser light in tissues. 2. Longer wavelengths are absorbed more by water in the skin, which can reverse the increase in penetration depth. 3. Radiation shorter than certain wavelengths is absorbed by the cornea, potentially causing cataracts. 4. At temperatures above a certain threshold, tissue vaporization occurs, while below that, reversible thermal damage can happen.
93
What are the different types of lasers and their interactions with hemoglobin and pigmented lesions?
| Laser Type | Interaction with Hemoglobin | Suitability for Pigmented Lesions | |------------|---------------------------|----------------------------------| | 1. Type A | Preferentially interacts | Less suitable | | 2. Type B | Preferentially interacts | Less suitable | | 3. Type C | Interacts less | More suitable |
94
What are the mechanisms by which lasers induce effects in tissues?
1. Photochemical: Mechanism on which most lasers rely, involving absorption by mitochondria. 2. Photoacoustic: High-energy photons generate acoustic waves leading to tissue breakdown. 3. Photothermal: Transformation of light energy into heat, causing direct damage to cells and tissues.
95
A patient with a tattoo containing black, blue, and green pigments seeks removal. Which laser should you use?
Use a Q-switched laser, such as Nd:YAG (1064 nm) or Ruby laser (694 nm), which are effective for black, blue, and green pigments.

Fitzpatrick's Dermatology, 9th Edition (Entrance Exam / Board Exam Prep) (213 decks)

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