Laser In Medicine Lecture Notes 2022-2023 PDF

AL Rasheed University College MEDICAL PHYSICS LASER IN MEDICINE Dr. ALI AQEEL 2022-2023 MEDICAL PHYSICS Dr. ALI AQEEL LASER Ordinary light, such as that from a light bulb, has many wa...

AL Rasheed University College MEDICAL PHYSICS LASER IN MEDICINE Dr. ALI AQEEL 2022-2023 MEDICAL PHYSICS Dr. ALI AQEEL LASER Ordinary light, such as that from a light bulb, has many wavelengths and spreads in all directions. The term “laser” stands for Light Amplification by Stimulated Emission of Radiation. A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term is an acronym for light amplification by stimulated emission of radiation. The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. A laser differs from other sources of light in that it emits light that is coherent. Lasers are used in optical disc drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optic, and free-space optical communication, semiconducting chip manufacturing (photolithography), laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. 1 MEDICAL PHYSICS Dr. ALI AQEEL Population inversion Ordinarily more atoms in the ground state than excited state An electron in an atom can absorb energy from light (photons) or heat (phonons) only if there is a transition between energy levels that match the energy carried by the photon or phonon. For light, this means that any given transition will only absorb one particular wavelength of light. 2 MEDICAL PHYSICS Dr. ALI AQEEL Photons with the correct wavelength can cause an electron to jump from the lower to the higher energy level. The photon is consumed in this process. When an electron is excited from one state to that at a higher energy level with energy difference ΔE, it will not stay that way forever. Eventually, a photon will be spontaneously created from the vacuum having energy ΔE. Conserving energy, the electron transitions to a lower energy level that is not occupied, with transitions to different levels having different time constants. This process is called spontaneous emission. 3 MEDICAL PHYSICS Dr. ALI AQEEL Both photons are in phase and have the same energy (color) (wavelength) Both photons can stimulate other atoms to emit photons that in turn stimulate the emission of more photons. 4 MEDICAL PHYSICS Dr. ALI AQEEL Laser Typical Characteristics uni-directional; same direction Single wavelength in visible region; same frequency same phase Intense beam Description Medical lasers are medical devices that use precisely focused light sources to treat or remove tissues. Laser light, on the other hand, has a specific wavelength. It is focused in a narrow beam and creates a very high intensity light. Because lasers can focus very accurately on tiny areas, they can be used for very precise surgical work or for cutting through tissue (in place of a scalpel). Procedures: Lasers are used in many types of surgical procedures. Some examples include. Cosmetic surgery (to remove tattoos, scars, stretch marks, sunspots, wrinkles, birthmarks, spider veins or hair) Refractive eye surgery (to reshape the cornea in order to correct or improve vision as in LASIK or PRK) Dental procedures (such as endodontic/periodontic procedures, tooth whitening, and oral surgery) General surgery (such as tumor removal, cataract removal, breast surgery, plastic surgery and most other surgical procedures). 5 MEDICAL PHYSICS Dr. ALI AQEEL With proper use, lasers allow the surgeon to accomplish more complex tasks, reduce blood loss, decrease postoperative discomfort, reduce the chance of wound infection, and achieve better wound healing. 6 MEDICAL PHYSICS Dr. ALI AQEEL DENTAL LASERS Dental lasers are widely deployed in the field for a wide variety of applications ranging from surgical cutting to curing. For cutting applications, single spatial mode lasers in the 1.5-micron range are typically deployed due to the high absorption of the water in the gums and the low absorption in teeth. Dental lasers allow for localized cutting and cauterization of the gum without causing harm to the tooth itself. Laser Dental Applications: 1- Reshape gum tissue (reduce prominence) 7 MEDICAL PHYSICS Dr. ALI AQEEL 2- Laser aided teeth whitening 3- Laser Drill Preparation for fillings Capable of killing bacteria located in a cavity No vibration Laser: Erbium Yag (Er: YAG) Wavelength 2940 nm, light of this wavelength highly absorbed by water Laser beam absorbed by decayed tissue because of large water content compared with healthy enamel Result: selective ablation of decay, conservation of healthy tooth no increase in pulp temperature. 8