Medical Applications of Lasers

Laser Applications in Medicine

• Lasers are used to deliver energy to tissue, which should absorb the laser wavelength strongly.
• Short wavelengths (400-600nm) are absorbed better than long wavelengths (700nm).
• Laser energy directed at human tissue causes a rapid rise in temperature, leading to tissue destruction.
• The amount of damage depends on the exposure time to increased temperature.

Laser Surgery and Treatment

• Lasers are used for painless removal of eye tumors.
• They act as a "bloodless knife" in surgery.
• Lasers repair retinal tears or holes that develop prior to retinal detachment through photocoagulation.
• They treat diabetic retinopathy, a complication of diabetes that affects the retina.
• Lasers are used in medical research for three-dimensional imaging called holography.

Applications of Visible Light in Medicine

Curved Surfaces and Endoscopy

• Curved lenses (convex, concave, cylindrical) and mirrors (ophthalmoscope, otoscope) are used in medical applications.
• Endoscopes (e.g., cystoscope, proctoscope, bronchoscope, gastroscope) view internal body cavities.

Transillumination and Phototherapy

• Transillumination transmits light through body tissues for detection of hydrocephalus, pneumothorax, sinuses, breasts, gums, and testes.
• Phototherapy helps premature infants recover from jaundice when exposed to visible light.

Microscopy and Fiber Optics

• Light microscopes resolve objects as small as 1 μm in diameter.
• Glass fiber (rigid endoscope) and plastic fiber (flexible endoscope) are used in microscopy, with glass providing clearer images.

Electromagnetic Spectrum

• UV photons have higher energy than visible photons.
• IR photons have lower energy than visible photons.
• UV light (100-400 nm) has higher energies, making it more useful than IR light (700-10000 nm).
• UV light can kill germs, cause skin reactions, and produce tanning, but is not visible to the eye.

Safety and Hazard Risks

• UV light is the major cause of skin cancer due to its absorption by DNA in cells.
• IR light, although not typically hazardous, can heat deep tissues and cause warmth.

Explore the use of lasers in delivering energy to tissues in medicine. Learn about the optimal wavelengths, tissue absorption, temperature effects, and damage to living tissue. Understand the absorbance and reflectance of skin based on wavelength.