Aesthetic breast surgery (see Chapter 7)

Laser surgery

Grabb and Smith, Lasers in Plastic Surgery; Achauer. PRS 1997

1. 1916 – Einsteins's theory of stimulated emission of radiation

2. 1950s – Schawlow and Townes: microwave amplification by stimulation emission of radiation (MASER)

3. 1957 – Maiman: light amplification by stimulated emission of radiation (LASER) using a synthetic ruby crystal

4. Helium neon laser, Nd:YAG, CO2 and argon lasers all developed in the early 1960s

5. Components of a laser:

• energy source

• electricity (argon laser)

• flashlamp (pulsed dye laser)

• another laser (CO2 laser)

1. laser medium – solid or gas

2. laser cavity (resonator)

• Laser medium is energized to excite electrons into a higher energy state (unstable orbit around the nucleus, ‘singlet state’)

• As electrons move back into a stable orbit (via a ‘metastable state’) a photon of light is emitted, i.e. spontaneous emission

• Generation of photons then perpetuates the movement of electrons of other atoms back into a stable orbit → more photons, i.e. stimulated emission

• Photons move randomly in the resonator but emerge through a pair of mirrors (one partially reflective) to become a parallel or collimated laser beam with all the same wavelength

• Longer wavelength → better penetration

• Energy (J) ∝ number of photons

• Power = energy s− 1, i.e. rate of delivery of energy (W)

• 1 W = 1 J s− 1

• rate of input of energy to create the laser beam

• Irradiance = power per unit area (W/cm2)

• Fluence = energy cm− 2 (J cm− 2)

• Gaussian distribution of heat within the spot – 10% overlap is not harmful

• Absorption coefficient of tissues also determines penetration

• Continuous wave lasers may be broken intermittently by a mechanical shutter to form a pulsed wave (pulsed-dye laser)

• […]