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| Fig. 1: FDG molecule. (Source: Wikimedia Commons) |
Nuclear medicine is a branch of medical imaging that uses small amounts of radioactive material to diagnose and determine the severity of or treat a variety of diseases, including many types of cancers and other diseases within the body. Because nuclear medicine procedures are able to pinpoint molecular activity within the body, they offer the potential to identify disease in its earliest stages as well as a patients immediate response to therapeutic interventions. Essentially, nuclear medicine imaging uses small amounts of radioactive materials called radiotracers which give off energy which is then detected by a special camera to create images of the inside of the body. [1] As of 2006 there were roughly 100 different procedures that could be done using nuclear medicine and as of 2008 there were over 30 million nuclear medicine images produced.
Nuclear medicine imaging uses small amounts of radioactive materials called radiotracers that are typically injected into the bloodstream, inhaled or swallowed. The radiotracer travels through the area being examined and gives off energy in the form of gamma rays which are detected by a special camera and a computer to create images of the inside of your body. Nuclear medicine imaging provides unique information that often cannot be obtained using other imaging procedures and offers the potential to identify disease in its earliest stages.
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| Fig. 2: PET scan of a normal brain (Source: Wikimedia Commons) |
The most common type of radiotracers is F-18, fluorodeoxyglucose, or FDG, a molecule similar to glucose (Fig. 1). Cancer cells typically absorb glucose at a faster rate than other cells. These higher rates can be seen on PET (positron emission tomography) scans (see Fig. 2). [1] After a radionuclide such as F-18 is injected into the body, the radionuclide releases a positron which then makes contact with an electron within the body. When this happens, two gamma rays are released in opposite directions of each other. Through a very complicated algorithm, a gamma camera is able to detect these rays which are being released. [3]
The problem with PET scans, however, is they are typically very low resolution and are almost impossible to use without an accompanying X-ray or MRI. However, MRI and CT scans are very accurate anatomically but they are not as informative for biological information. For example, magnetic resonance (MRI) typically have a lower limit of detection at the millimolar level (6 × 1017 molecules per mL of tissue) while nuclear imaging allows for a lower limit of detection at the picomolar level (6 × 108 molecules per mL of tissue). [1]
Nuclear medicine today has the ability to detect, diagnose, and treat neurological diseases, cancer, gastrointestinal diseases, neurological diseases, genitourinary diseases, coronary artery disease, bone diseases and trauma, infections, and pulmonary diseases. The future of nuclear medicine looks incredibly promising. There are hopes that soon they will be able to detect links between brain chemistry and behavior (e.g. eating disorders). [2] Furthermore, there is an emerging field of "personalized medicine." Personalized medicine would allow doctors to very accurately determine what the response to a certain treatment would be. While this process is very slow and takes a lot of work and data, it can be a huge advancement in the way patients are treated because patients would receive the absolutely best treatment for the illness that they have.
© Brandon Wulff. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] S. R. Cherry, J. A. Sorenson, and M. E. Phelps, "Physics in Nuclear Medicine." (Saunders, 2012).
[2] Advancing Nuclear Medicine Through Innovation (National Academices Press, 2007).
[3] A. Rios, "Nuclear Medicine Imaging," Physics 214, Stanford University, Winter 2017.
