Biophysics: Application of Light in Medicine Lecture Notes PDF

BIOPHYSICS (LECTURE) Dr. Mahmoud Ismail Dr. Diaa Rayan Biophysics (week 7) LIGHT IN MEDICINE Biophysics (week 7)  Nature of light  There are a dual nature of light:  Particle nature.  Wave nature  Light The word usually refers to visible light, which...

BIOPHYSICS (LECTURE) Dr. Mahmoud Ismail Dr. Diaa Rayan Biophysics (week 7) LIGHT IN MEDICINE Biophysics (week 7)  Nature of light  There are a dual nature of light:  Particle nature.  Wave nature  Light The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight.  Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum.  visible light occupies only a narrow band from about 400- 700 nm.  INVERSE SQUARE LAW  “Intensityof radiation striking the surface is inversely proportional to the square of the distance” from the source.  Inverse square law can be employed in practice; The closer the source of radiation , the greater the intensity of radiation being received by the skin, the further away, the less the intensity. INVERSE SQUARE LAW The Medical Applications of Light The light in medicine is beneficial in diagnostic purposes and therapeutic purposes.  visible light in medicine permit the physician to obtain visual information about the patient regarding.  endoscopes  A number of instruments, called endoscopes, are used for viewing internal body cavities.  Special purpose endoscopes are often given names indicating their purpose.  For example, cystoscopes are used to examine the bladder, proctoscopes are used for examining the rectum, bronchoscopes are used for examining the air passages into the lungs and colonoscopes are used for examining the colon. the ophthalmoscope for looking into the eyes and the otoscope for looking into the ears  flexible Vs rigid endoscopes  The image obtained with a flexible endoscope is not as good as that obtained with a rigid endoscope, but often the only alternative to a flexible endoscopic examination is exploratory surgery.  Flexible endoscopes usually have an opening or channel that permits the physician to take samples of the tissues (biopsies).  Light Therapy (phototherapy)  Since light is a form of energy and is selectively absorbed in certain molecules, it should not be surprising that it can cause important physiological effects.  Many premature infants have jaundice, a condition in which an excess of bilirubin is excreted by the liver into the blood.  Applications of UV and IR in medicine  The wavelengths adjacent to the visible spectrum also have important uses in medicine.  Ultraviolet photons have energies greater than visible photons, while IR photons have lower energies. UV light in medicine (Benefits) 1-Ultraviolet light with wavelengths below about 290nm is germicidal, that is, it can kill germs-and it is sometimes used to sterilize medical instruments.  UV light in medicine (Benefits) 2- Ultraviolet light also produces more reactions in the skin than visible light. Some of these reactions are beneficial, and some are harmful. One of the major beneficial effects of UV light from the sun is the conversion of molecular products in the skin into vitamin D. UV light in medicine (hazards) 4-Ultraviolet light from the sun affects the melanin in the skin to cause tanning. However, UV light can produce sunburn as well as tan the skin. 5- Lens and cornea can be damaged by ultraviolet (UV), it can developed cataracts which destroy the clarity.