1. Dr. Ali Saad/ biomedical technology KSU 1 Medical L-A-S-E-R Ali S. Saad Department of Biomedical Engineering College of applied medical Sciences King Saud University

2. Dr. Ali Saad/ biomedical technology KSU 2 1961 Ruby laser invented (Maiman) 1965 Argon laser applied to eye surgery Surgical applications Opthalmology General surgery Ob-gyn Cardiac Orthopaedic Plastic/dermatology Medical L-A-S-E-R

3. Dr. Ali Saad/ biomedical technology KSU 3 Three elements required for a laser to work 1. Laser medium - promotes population inversion when Excited Solid, Gas or Liquid 2. Optical Cavity with resonating circuit One 100% reflective mirror One partially transmissive mirror 3. Source of energy (pumping) Electrical, light Laser Elements Laser Optics USA

4. Dr. Ali Saad/ biomedical technology KSU 4 Monochromatic - single wavelength Coherent - output waves in the same frequency and phase TEM mode - transverse electromagnetic field; 00 best; function of mirror alignment Modes Continuous, pulsed, Q-switched (micro second), Mode locked (pico second) Laser Characteristics

5. Dr. Ali Saad/ biomedical technology KSU 5 Laser Tissue Interaction Tissue characteristics - Color, etc. Laser wavelength - Far IR – UV Profio FREE ELECTRON LASER Selectable output laser Size of Votey building

6. Dr. Ali Saad/ biomedical technology KSU 6 Laser Tissue Interaction Energy is reflected, transmitted, absorbed and scattered Lambert Beer law I = Io 10 -  X α= absorption coefficient X = thickness of material Io = incident intensity I = transmitted intensity Extinction length = 1/α = L; where 90% of the intensity is absorbed.

7. Dr. Ali Saad/ biomedical technology KSU 7 Laser Tissue Interaction

8. Dr. Ali Saad/ biomedical technology KSU 8 Laser Tissue Interaction Power density important for tissue vaporization Spot size minimum proportional to wavelength Shorter wavelength ~ Smaller spot size

9. Dr. Ali Saad/ biomedical technology KSU 9 Carbon Dioxide Laser 10.6 um - Far infra-red - need visible aiming Gas mix - 5CO2 + 10N2 + 85He Electrical pumping - DC or RF 100+ watts may be used 10-20% efficient Absorbed by all tissue/H2O Extinction length is.03mm - vaporization Fiberoptic losses significant - use lens

10. Dr. Ali Saad/ biomedical technology KSU 10 ND:Yag Laser 1.06 um - Infra-red ND doped YAG crystal Optical pumping 1% efficiency Two types Continuous/pulsed for general surgery Excellent for coagulation, deep heating Weakly absorbed by H2O - transmit through H2O Can go thru fiberoptics easily Q-switched for opthalmology

11. Dr. Ali Saad/ biomedical technology KSU 11 Argon and argon dye laser 488 nanometers - blue light Argon gas Electrical pumping Low efficiency.1% Little absorption by H2O - high absorption by red objects (e.g. retina) Small spot size Argon dye provides multiple wavelengths Photoradiation therapy @ 630 nm Eximer

12. Dr. Ali Saad/ biomedical technology KSU 12 Diode and Holmium Laser - 193 nm - UV, Exciter fluoride gas, electrical pumping, very precise, ophthalmic use (corneal sculpting) Diode - aluminum gallium arsenide (AlGaAs) @ 810 nm or indium gallium arsenide (InGaAs) @ 980 nm, fiber optic transmission, long life Holmium:yttrium-aluminum-garnet (Ho:YAG), similar to ND:YAG; 2100 nm; orthopaedic,general and other procedures