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Nuclear Medicine By Kristen Hanson Nuclear Medicine is considered a medical specialty involving the use of radioactive substances to aid in the diagnosis and treatment of disease. Nuclear Medicine procedures combine radionuclides to other elements which form chemical compounds, or they are combined to preexisting pharmaceuticals which form radio pharmaceuticals. When these radiopharmaceuticals are given to the patient they can be directed to specific organs and cell receptors. Radiopharmaceuticals help provide images of the extent of disease based on the cellular function and makeup rather than relying on physical changes in tissue anatomy. Nuclear medicine is basically “radiology preformed on the inside”, because it measures radiation emitting from within the body, whereas X-rays generate radiation towards the body. The idea of Nuclear Medicine dates as far back as the mid 1920 in Germany. When a scientist named George de Hevesy performed experiments on rats. He was able to establish the tracer principle. He administered radionuclides which produced metabolic pathways. Later on, in 1936 John Lawrence known as “the father of nuclear medicine” made the first application in patients using an artificial radionuclide phosphorus-32 in treatments for leukemia.[1] Marie Curie discovered radioactive thorium, polonium and coined the term “radioactivity” Nuclear medicine received public recognition on December 7, 1946, when the Journal of the American Medical Association published an article of a successful treatment of a patient with thyroid cancer. The patient, given radioiodine, the cancer metastasized. Though the radioiodine was used for thyroid cancer therapy it was later used to tract thyroid function and also used as therapy for Hyperthyroidism. In the early 1950’s Nuclear medicine gained a widespread clinical use. Knowledge of radionuclides, detection of radioactivity, and administering certain radionuclides allowed tracing of biochemical processes. The most important radionuclide that was discovered was Technetium-99m. It was discovered by C. Perrier and E. Serge which was the artificial element 43 on the periodic table. Today, the use of Technetium-99m is the most common element in Nuclear medicine. By the 1970’s almost all of the body’s organs could be seen using nuclear medicine procedures. In 1971, American Medical Association officially recognized nuclear medicine as a specialty.[2] in the 1980’s, radiopharmaceuticals were used in the diagnosis of heart disease. The discovery and development of the single photon emission computed tomography (SPECT) led to 3D reconstruction of the heart and thus brought about the field of Nuclear Cardiology. In a typical nuclear medicine study a patient is intravenously given a radionuclide. Most diagnostic radionuclides emit gamma rays. Therapeutic nuclides produce cell-damaging properties. Any patient undergoing nuclear medicine is at risk of inducing cancer. Radiation dosing guidelines say that it is similar to the risk of an X-ray but it is delivered internally rather from an outlying source such as an x-ray machine and that the dose is significantly higher. Nuclear medicine imaging is different from most other types of imaging in that diagnostic tests reveal the physiological function as opposed to the traditional anatomical imaging like an x-ray or CT scan. Nuclear medicine imaging is usually for tissues and organs such as the heart, brain and lungs. Diagnostic tests show how the body handles substances when there is a disease or pathogen present. When the radionuclide is administered to a patient, their body will begin to metabolize the chemical and acts accordingly, known as a tracer. Some aspects of the substance will gravitate to specific region and be absorbed or pool around disease causing what is known as a “hot spot”. Other disease processes exclude the radionuclide substance causing a “cold spot.” Radiopharmaceuticals used in nuclear medicine therapy and investigational diagnosis emit ionizing radiation which travel only a short distance, minimizing un wanted side effects. More often than not procedures are done on an outpatient basis. Although the risks of radiation exposure are not fully understood, precautions are taken to not over expose patients. “ALARP” (As Low as Reasonably Practical) was developed to take into account that a patient is not given higher doses of radiation then deemed necessary for proper imaging. The main device used in nuclear medicine imaging is the gamma camera. The gamma camera detects radiation emitted by the tracer in the body and then displays an image. With computer processing it can be displayed in several differ planes: axial, coronal and saggital. Nuclear medicine has come a long way since the early 1900’s with developing technology and the ability to diagnose disease on an internal level. References 1. Donner Labortory: The Birthplace of Nuclear Medicine http://jnm.snmjournals.org/content/40/1/16N.full.pdf 2. http://intractive.snm.org/docs/whatisnucmed.pdf from the Society of Nuclear Medicine