in the field of biophotonics have created many opportunities for significant improvements in the quality of health care as well as for substantial reductions in the overall cost.
The discipline of biophotonics deals with the interaction of light, or electromagnetic radiation, with living organisms and biologically active macromolecules: proteins (hemoglobin), nucleic acids (DNA and RNA), and metabolites (glucose and lactose). Light interacts with biological material and organisms in many diverse ways, depending primarily on the energy or color of the photon. At both high (x ray) and low (radio frequency [RF]) energies the body is mostly transparent, thus allowing the non-invasive imaging of the internal structure of organs and bones. In contrast, certain colors or wavelengths in the infrared (IR) and ultraviolet (UV) regions are absorbed strongly by biological tissues. The intense, focused light of lasers with these colors can be used for a wide variety of unique therapeutic interventions: making incisions, cauterizing and sealing wounds, and selectively heating or even vaporizing specific regions of organs and tissues. In the visible region of the spectrum, some biologically active macromolecules naturally absorb specific photon energies or colors. The amount of this intrinsic absorption can be used to determine the physiological health of an organ—for example, whether the tissue is getting sufficient oxygenated blood flow. Non-absorbing macromolecules can be labeled using specifically engineered dyes that selectively bind to macromolecules. These dyes or biomarkers can be used in conjunction with visible and near-infrared light to highlight specific cell and tissue types, such as metastatic cancer cells circulating in the bloodstream. Modern biomedical instrumentation takes advantage of this wide range of interactions between photons and biological materials and provides a remarkably broad set of tools for the physician and life scientist.
Prior to the modern age of medicine, physicians primarily used their five senses directly to determine the causes of ill health.5 For example:
• The color of a person’s eyes was studied to detect jaundice and possible liver failure.
• The urine of patients was tasted for sweetness, to detect the presence of glucose and diagnose diabetes.
• An ammonia-like odor in urine implied possible kidney failure.
5 Berger, D. 1999. A brief history of medical diagnosis and the birth of the clinical laboratory. Part 1—Ancient times through the 19th century. Medical Laboratory Observer 31(7):28-30, 32, 34-40.