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Nuclear medicine and radiology are the whole of medical techniques that involve radiation or radioactivity to diagnose, treat and prevent disease. While radiology have been used for close to a century, “nuclear medicine” began approximately 50 years ago. Today, about one-third of all procedures used in modern hospitals involve radiation or radioactivity. These procedures are among the best and most effective life-saving tools available, they are safe and painless and don’t require anesthesia, and they are helpful to a broad span of medical specialties, from pediatrics to cardiology to psychiatry.
While both nuclear medicine and radiology are used as a diagnostic procedure (to determine a patient’s health, monitor the course of an illness or follow the progress of the treatment) and as a therapeutic procedure (to treat illnesses), they are different in that in nuclear medicine radioisotopes are introduced into the body internally, whereas in radiology X-rays penetrate the body from outside the body.
DID YOU KNOW?
Bone imaging is an extremely important use of radioactive properties. Supposed a runner is experiencing severe pain in both shins. The doctor decides to check to see if either tibia has a stress fracture. The runner is given an injection containing 99Tcm. This radioisotope is a gamma ray producer with a half-life of 6 hours.
After a several hour wait, the patient undergoes bone imaging. At this point, any area of the body that is undergoing unusually high bone growth will show up as a stronger image on the screen. Therefore if the runner has a stress fracture, it will show up on the bone imaging scan.
This technique is also good for arthritic patients, bone abnormalities and various other diagnostics.
Major Advances in Nuclear Medicine Diagnosis and Treatment
Exploratory surgery used to be the way doctors investigated health problems. Doctors would cut, poke, and prod. But since the 1940′s, nuclear technologies have offered an increasing array of diagnostic techniques that help patients avoid the pain of surgery while their physicians gain knowledge of the body’s inner workings.
X-rays, MRI scanners, CAT scans, and ultrasound each use nuclear science and technology to troubleshoot different parts of the body and diagnose conditions. Each of these are non-invasive procedures which means patients do not need to undergo any kind of surgery. More advanced nuclear medicine uses computers, detectors, and radioactive substances, called isotopes, to give doctors even more information about a patient’s internal workings. Known as nuclear imaging, these procedures include bone scanning, Positron emission tomography (PET), Single photon emission computed tomography (SPECT) and Cardiovascular imaging. The use of these procedures depends on the patient’s symptoms.
One out of three patients admitted to hospitals undergo at least one medical procedure that uses isotopes. Isotopes are substances with identical chemical properties that sit on the same place on the Periodic Chart of Elements, but they have different atomic weights. Both radioactive isotopes (also called radioisotopes) and stable isotopes contribute to techniques to improve a physician’s ability to diagnose ailments.
Radioisotopes are useful because the radiation they emit can be located in the body. They can be administered by injection, inhalation, or orally. A gamma camera captures an image from isotopes in the body that emit gamma radiation. Then, computers enhance the image, allowing physicians to detect tumors or fractures, measure blood flow, or determine thyroid and pulmonary functions.
The first radiopharmaceutical to be widely used was the fission product, iodine-131, in the form of the simple salt, sodium iodide, the use of which was established in the late forties as a diagnostic test for certain thyroid disorders. Because the drug could be administered orally, in solution, it was referred to in the press as the “Atomic Cocktail”.
Since those pioneering days, the practice of nuclear medicine has soared in most developed countries. Approximately 16 million people in the United States are tested diagnostically each year with a radioactive drug, either in vivo or in vitro.
Radiopharmaceuticals are used in-vivo to obtain clinical information by measuring the spatial distribution of the drug in an organ (scintigraphy), or by measuring the uptake or throughput of the drug within the organ (uptake or organ-function test).There are less than 50 radiopharmaceuticals for in vivo administration which are in common use. Many of them are used for identical diagnostic tests, the choice of a particular one frequently depending on the personal preferences of the practitioner. The development of more effective radiopharmaceuticals is being intensively investigated in several score laboratories all over the world and it is likely that the drugs used in nuclear medicine will be altered considerably during the next 10 to 20 years.
|1311 (also 12SI)- Sodium iodide||Thyroid uptake|
|1311 – Rose Bengal||Liver scan|
|1311 – Hippuran||Kidney scan|
|1311 – Human serum albumin||Blood volume, circulatory studies|
|1311 – lodinated oils||Fat absorption studies|
|51 Cr – Sodium chromate||Spleen scanning (by tagging red blood cells)|
|57Co – Vitamin B-12||Pernicious anemia diagnosis|
|198Au – Gold colloid (less than 1 micron diameter particle)||Liver scan|
|197Hg – Chlormerodrin||Brain and kidney scans|
|75Se – Selenomethionine||Pancreas scan|
|1311 or 99mTc – Macroaggregated serum albumin (30- 50 micron diameter particles)||Lung scan|
|18F – Sodium fluoride||Bone scan|
There are a number of in vitro clinical tests which employ radioactive reagents, but the most important one in present use is the radioimmunoassay for body hormones.Radioimmunoassay is an exceedingly sensitive method which is capable of measuring most hormones at the nanogram to picogram level. It is also very specific since the antibody binds its specific hormone very selectively. A surprisingly wide range of hormones and other antigens can be assayed by this method. A few examples are assays for insulin, thyroxine, prostaglandins, digitoxin, human growth hormone, and the “hepatitis associated” antigen, the test for which can minimize hepatitis injection through blood transfusions by pre-testing donors.
Center for Nuclear Science and Technology Information of the American Nuclear Society
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