Modern nuclear medicine (NM) utilizes small quantities of radioactive material to diagnose, estimate the severity of and to treat a variety of illnesses, such as numerous types of cancers, endocrine, gastrointestinal and neurological disorders, heart disease, etc. Its procedures offer high precision, have the potential to identify diseases in their earliest stages and to provide therapeutic interventions.
NM exploits four common types of radiation: the beta-plus and beta-minus rays, the gamma rays, alpha rays and x-rays. Beta-plus rays release photons, the journey of which is subsequently analyzed in Positron Emission technology. Beta-minus rays emit the negatively loaded particles and are mostly used in oncology. Gamma rays are commonly used for diagnostic purposes, as they can go through the matter of high thickness (Chandra & Mihailidis, 2012). The alpha rays are usually employed to transform the molecules of organic tissue. X-Rays, being the first type of radiation discovered and produced, mark the beginning of modern radiology. About 100 radioisotopes producing beta or gamma radiation are employed in nuclear medicine to treat and diagnose a number of conditions. The most commonly used are: 131I, 99mTc, and 60Co (Chandra & Mihailidis, 2012).
The majority of NM procedures are non-invasive and painless. The only exception is the intravenous injections of radio tracers or radiopharmaceuticals used in diagnostics and treatment. The latter can be either injected, inhaled or swallowed, eventually accumulating in the body area that has to be examined. The radiotracers produce radioactive emissions that are subsequently detected by an imaging device. The beta-minus labelled radiopharmaceuticals are often used in oncology to destroy cancer cells. Other therapeutic procedures offered by NM include but are not limited to: radioactive iodine therapy, cancer treatment, radioimmunotherapy employed to treat Non-Hodgkin’s lymphoma, etc. (Khalil & Zanzonico, 2011).
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Before starting a NM procedure, the patient is commonly asked several questions in order to estimate the possibility of negative side effects. Women are asked if there is a chance that they are pregnant, since certain NM procedures may negatively affect the fetus. Patients are as well asked to provide a full list of medications they are currently taking, including supplements and vitamins, inform about existing allergies or recent illnesses. Prior to the procedure any metallic objects, and jewelry are removed. The patient preparation instructions may vary, due to the type of NM procedure. Young children sometimes require sedation to prevent them from moving.
One of the major advantages offered by the nuclear medicine is the possibility to identify diseases in the early stages, often before the patient shows any symptoms. NM examinations provide a high precision information that is often unattainable through other assessment techniques. These are as well less expensive than some of the diagnostics procedures, such as exploratory surgery or surgical biopsy.
The small amount of radiotracer used during procedures result in comparatively low radiation exposure for the patient. Thus, the radiation risk is very low compared with the potential benefits. In case the radiotracer is injected into the body, redness and slight pain may appear. Allergic reactions to radiopharmaceuticals are possible, though extremely rare.
Positron Emission Tomography or PET is a NM diagnostic procedure most commonly used in the fields of oncology, cardiology, and neurology. PET scanning is designed to assess the metabolism of a particular tissue or organ, providing information about its physiology, anatomy and biochemical properties. The radiotracers used during PET procedures are usually isotopes with short half-lives such as nitrogen13, carbon11, oxygen15, fluorine11, etc. These may be incorporated into glucose, water, ammonia, or into molecules binding to receptors or other drug action sites.
Oncology-related PET usually employs fluorine-18 or fluorodeoxyglucose as tracers that provide an intense radiolabeling of body tissues having high glucose uptake, such as the liver, the brain and most types of cancer. Thus, PET is widely used for diagnosis, stage assessment and monitoring the treatment results of cancers, in particular lung cancer, Hodgkin’s and non-Hodgkin’s lymphoma (Menda, Madsen & Bushnell, 2000).
The application of PET in Neurology is grounded on the assumption that high radioactivity areas are associated with brain activity. The scan measures the blood flow in different brain areas, using the radiotracer oxygen-15 to diagnose Alzheimer’s disease, as well as other dementing illnesses. Fluorodeoxyglucose-based PAT, being a cost-efficient alternative to SPECT, is used to diagnose hibernating myocardium. PET imaging is also feasible in patients with atherosclerosis to estimate the risk of stroke.
- Chandra, R., & Mihailidis, D. (2012). Nuclear Medicine Physics: The Basics. 7th ed. Medical Physics, 39(10), 6525.
- Khalil, M., & Zanzonico, P. (2011). Basic Sciences of Nuclear Medicine. Medical Physics, 38(9), 5265.
- Menda, Y., Madsen, M., & Bushnell, D. (2000). PET in Oncology. Basics and Clinical Applications. Clinical Nuclear Medicine, 25(11), 949.
