BIOMEDICAL OPTICSAND LASERS

By:

Engr. Joseph Ronald Cañedo

Outline

• Introduction / literature

• Basics of laser physics

• Matter acting on light

• Light acting on matter

• Medical laser applications

• Laser safety

Electromagnetic spectrum

LASER: Light Amplified by Stimulated Emission of Radiation

Laser beam characteristics

Matter acting on light

• reflection and refraction• absorption and scattering

Reflection and refraction

law of reflection: θ = θ‘law of refraction: n1 sin θ = n2 sin θ‘‘

Absorption• tissue absorption according to Lambert-Beer:

I(z) = I0 exp (−αz)

Scattering

Light acting on matter

Laser-tissue interactions

Photochemical interaction

Thermal interaction

Extra: Laser-induced interstitial thermotherapy (LITT)

Photoablation

Plasma-induced ablation

Photodisruption• pulse duration: 10−15 − 10− 9 sec• energy density: 1 − 1000 J/cm2• power density: 1011 − 1013 W/cm2• electric field strength: 107 − 108 V/cm

Laser applications in medicine

Laser applications in ophthalmology

• Indications:– retinal detachment– Cataract– Glaucoma– wrong-sightedness

Wrong-sightedness

Refractive power of the eye

Techniques in refractive corneal surgery

Model of keratomileusis

fs-LASIK: Laser in situ keratomileusis with the femtosecond laser

Laser applications in dentistry

Pain free caries therapy: Investigated laser systems

Caries diagnostics by plasma spectroscopy

Plasma spectroscopy

Laser applications in neurosurgery

Laser safety

Laser safety classes

Realized laser safety• laser safety officer• laser safety equipment:

1. warning sign and warning lamp2. safety curtain3. safety glasses