Bologna CH136 Lasers

Question 1

What are the four components common to all lasers?

Answer 1

Medium source delivers mirrors
1 - a gas, liquid or solid medium that can be excited to generate light
2 - a source of pump energy for exciting the medium
3 - mirrors at end of lasers forming optical cavity that favours the amplification process
4 - a delivery system

Question 2

Monochromicity refers to the emission of a well defined wavelength, rather than a band of wavelengths

Answer 2

True

Question 3

Coherence refers to a very parallel beam of light

Answer 3

False - this is collimation

Question 4

Collimation refers to light waves that travel in phase, both in time and space, similar to column of soldiers marching in step

Answer 4

False — this is COHERENCE

Question 5

“Q” switched lasers produce short, intense bursts of light particularly useful for selectively removing tattoos and pigmented lesions whilst limiting thermal damage to surrounding tissues

Answer 5

True

Question 6

Thermal relaxation time is the time required for a heated tissue to call halfway towards its initial temperature

Answer 6

True

Question 7

The key to clean ablation of tissue is to ablate it quickly, before too much heat is conducted into surrounding tissue

Answer 7

True

Question 8

The TRT of a target is proportional to the square of its size

Answer 8

True

Question 9

Methods for laser cooling

Answer 9

• liquid fluorocarbon sprayed onto skin
• solid contact cooling with cold sapphire window held against the skin
• cold air or cold gels for passive skin cooling

Question 10

Ablative lasers cause a “plume” of material leaving the skin

Answer 10

True

Question 11

Oxyhaemoglobin has an absorption band at 810nm

Answer 11

False - 577nm

Question 12

Pulsed dye laser treatment fluence is increased for more deeply pigmented skin

Answer 12

False - decrease fluence for deeply pigmented skin

Question 13

Purpura following pulsed dye laser results from delayed vasculitis , microvascular haemorrhage and subsequent thrombosis

Answer 13

True

Question 14

When pulse duration is under ~20 milliseconds, there is little or no immediate purpura because cavitation and vessel rupture are avoided

Answer 14

False - when it EXCEEDS 20ms

Question 15

Nd:YAG frequency doubled can remove epidermal melanin and red tattoos (by producing 532nm visible green light)

Answer 15

True

Question 16

Responses to non ablative rejuvenation are usually rapid and pronounced

Answer 16

False - gradual and subtle

Question 17

Non ablative fractional photothermolysis focuses mid-IR, laser microbeams to create pixilated patterns of microscopic columns of thermal damage - microthermal treatment zones (MTZs)

Answer 17

True

Question 18

Ablative fractional photothermolysis utilises CO2 or Er:YAG lasers to vaporise many large vertical channels that extend deeply into the skin

Answer 18

False - small vertical channels

Question 19

IPL can be used to treat vascular and pigmented lesions

Answer 19

True

Question 20

IPL are more target selective compared with lasers, as they can deliver very short pulses for selective photothermolysis

Answer 20

False - lasers more target selective , IPL cannot deliver very short pulses

Question 21

Radiofrequency (RF) represents a direct electric current that locally heats tissue based on both local current density and electrical impedance of the tissue

Answer 21

False - rapidly alternating current not direct

Question 22

Radiofrequency generators operate at frequencies similar to radio bands

Answer 22

True

Question 23

Radiofrequency current is delivered from one or more electrodes held in close proximity but NOT in contact with the skin

Answer 23

False - close proximity or contact with skin

Question 24

Cryolipolysis induces a cold panniculitis

Answer 24

True