Nuclear medicine has become fundamentally life-saving as a diagnostic tool in today’s medicine, however exposure to radioisotopes has risks. Understanding these risks and making an educated decision is crucial in personal choices regarding medical treatment. This overview of recent and relevant research provides an insight and support to the benefits of radioisotope usage, whilst presenting the associated risks. ? INTRODUCTION: With the discovery of radioisotopes in 1934, and the production of radionuclides in 1946, the world has witnessed a major growth and evolution in the field of Nuclear Medicine.
(Mandal, 2012) This specialty field utilises radionuclides for the diagnosis and subsequent treatment of disease. The process involves administering radioactive materials to the patient, with the ability to localize this material to a specific organ. (Department of Nuclear Medicine – Austin Hospital, 2007) This then allows the specialists to map an organ’s cellular function, instead of the physical changes in it’s tissue which more traditional imaging techniques such as X-ray reveal. (DNM, 2007)
Although being highly effective in its application, the use of radioactive substances poses an inherent risk to both the patient, health professionals, and on a broader scale, the environment. This article discusses the implications of nuclear medicine and evaluates the dangers associated with it. ISOTOPES: WHAT ARE THEY? Many of the known chemical elements have a number of isotopes. (Gothard, 2004) Isotopes can be referred to as a ‘species’ of the base element, however, unlike elements, they feature a differing mass number, meaning the amount of protons and neutrons is imbalanced.
(Gothard, 2004) Sometimes, an isotope exists with an unstable nucleus, spontaneously emitting excess energy through radiation known as alpha (? ) particles, beta (? ) particles or gamma (?? ) rays. (Figure 1) (Mandal, 2012) This is known as a radioactive isotope, or radioisotopes. As radioisotopes emit certain particles over time, its nucleus will begin to decay until it becomes stable again. RADIOISOTOPES IN NUCLEAR MEDICINE: Following the discovery of radioisotopes, doctors were able to learn how to combine them with existing pharmaceuticals, which were already known, to concentrate in certain parts of the body.
By utilising the radioactivity of the resulting compound, specialist equipment was able to be designed to trace the distribution of these compounds through the patients body. Two major imaging systems currently in use are PET and SPECT scanners. (Mandal, 2012) POSITRON EMISSION TOMOGRAPHY (PET): This method of nuclear scanning involves injecting a radioactive glucose combination into a patient. As a result of the high metabolism of cancerous cells, the radioactive glucose will be rapidly consumed by a cancerous cell.
(National Cancer Institute, N/A) Subsequent rotational scanning of the patients body will allow an image to be developed through the detection of gamma rays emitted from the radioactive glucose mix. This shows the location of these cancerous cells due to their radioactivity. (NCI, N/A) The digital image is then converted into two and three dimensional images of the targeted organ. From the images, further analysis could determine if a previously identified cancer cell is dying, as the cancer would require a smaller amount of the glucose mix.
(PET PROS, 2009) SINGLE POSITRON EMISSION TOMOGRAPHY (SPECT): SPECT scans differ from PET scans by the medium they use to transport the radioisotope. (Mayfield Clinic, 2014) It involves radioactive material known as tracers, which, when injected into a patient, mix with the blood and are transported around the body. As with PET scanning, the makeup of the radioactive tracer can be controlled to give the ability to target a specific part of the body. (NCI, N/A) The gamma sensors are then able to record an image of the blood flow through the tissue.
The image resolution provided by SPECT scanning isn’t as high as a PET scan due to the internal processes and the way the radiation is measured. (NCI, N/A) However, SPECT scans are considerably cheaper due to requiring easily obtained radioisotopes. This allows a wider cross section of the community to take advantage of the technology. The SPECT scan opposite can be used to effectively identify abnormalities regarding the function of the patient’s brain. The two images on the top show decreased blood flow to the left side of the brain, confirming for surgeons the nonfunctioning area of the brain, causing seizures.
(Mayfield Clinic, 2014) ? RADIATION THERAPY: Radiation can be classified as either ionizing or non-ionizing. The difference lies in the radiation’s frequency. (American Cancer Society, 2010) Ionizing radiation has a very high frequency, and contains enough energy to alter the structure or DNA of the cell when it collides with it. It is this property that radiation therapy uses to kill off damaged cancer cells when high doses are directly targeted at the known cancer cells. (ACS, 2010) RISKS AND ISSUES: Radiation, despite the negative public image, is an everyday fact of life.
The light coming from the sun, and the heat that our bodies emit are all forms of radiation. (Radiation Protection, 2012) As was highlighted earlier, the radioisotopes used in nuclear medicine are all forms of ionization radiation. When administered, this radiation is designed to target the damaged, cancerous cells, however, normal, healthy cells are also exposed as a consequence. It is these damaged normal cells that may subsequently lead to secondary cancers. (Radiation Protection, 2012) Whilst the doses received are all low level, the obvious impact on the patients health can’t be overlooked.
Studies into the people affected by the WW2 atomic bombs, and the Chernobyl nuclear reactor failure, support the cancer causing affects of ionizing radiation. The amount of damage that a cell receives when exposed, is proportional to the length of exposure. In the above two cases, people were exposed to high doses of radiation for a long period, hence the cancers developed quickly. In figure 4 below, the equivalent exposure by natural radiation is given for a number of nuclear medicine procedures.
(Radiation Protection, 2012) Whilst nuclear medicine targets cancer cells, normal healthy cells can inevitably also be affected during the procedure. (Radiation Protection, 2012) Certain types of cancer have a higher risk of developing this way than others. Cancers of the thyroid gland and bone marrow have a greater risk of developing, and a young person’s growing body is more likely again. This risk of secondary cancer forms an integral part of the patients care plan, whereby the benefits of the treatment are weighed up against the dangers.
Figure 2 shows the various nuclear medicine procedures, listing the effective dose, the equivalent number of chest x-rays, and the equivalent period of natural radiation. (Maximum radiation levels per year for and adult are 4. 5 millisieverts) Figure 2 – (DNM, 2007) The exposure to radiation is not limited to the patient. The health care professionals that administer the radioactive pharmaceuticals, and any person that comes into contact with the patient in the short term after treatment are all exposed to a greater risk.
(Loy, 2008) Pregnant women who undergo nuclear medicine of any type, have a high risk of mutation to their fetus. As the development of a fetus is constantly under cell division (mitosis), the introduction of a radiopharmaceutical could have the potential to have very detrimental effects on the fetus. (Loy, 2008) ECONOMIC AND POLITICAL FACTOR: Nuclear medicine is costly, as it involves the use of complex machines and the production of artificial radioisotopes. (National Cancer Institute, 2007) They are created in a nuclear reactor or a cyclotron which are very expensive to construct and maintain.
(NCI, 2007) In order for the nuclear medicine industry to evolve and progress, prices are high and generally only available in very wealthy countries. As this field of medication receives most of its funding from the government, developing countries generally do not invest in this treatment, creating a problem concerning the political and economical factors. (NCI, 2007) ENVIRONMENTAL FACTOR: Environmentally, the creation of radioisotopes and their applications have the potential to be quite harmful.
As artificial radioisotopes are required to be made in a nuclear reactor, as seen in the past, they have the potential to leak and explode. (NCI, 2007) When this happens, the surrounding environment will be greatly affected. With the Chernobyl Nuclear Disaster in 1986, the city of Pripyat had to be evacuated, however, the realisation came too late and many people had been exposed to radiation before they left the city. Now, no one can enter the area within a 15km radius of the plant as the levels of radiation continue to remain high. CONCLUSION:
Nuclear medicine has been a rapidly growing industry since 1935. With our modern lifestyle and ageing population, we rely on a robust, professional health care system which demands the use of the latest science and technology. With an educated and responsible health care system, the inerrant secondary risks of nuclear medicine can be effectively managed. This is why governments are continuing to progress with this area of science, and, will probably continue for years to come. (ACS, 2010)
Bibliography Centers for Disease Control and Prevention. (2014, February 3). Cancer Prevention and Control.Retrieved February 9, 2014, from CDC: http://www. cdc. gov/cancer/dcpc/resources/features/WorldCancerDay/ Dr Jones, J. , & Dr El Banan, M. (N/A, N/A N/A). Electron-positron annihilation.
Retrieved February 8, 2014, from Radiopaedia. org: http://radiopaedia. org/articles/electron-positron-annihilation Gothard, R. (2004, N/A N/A). Isotopes. Retrieved February 8, 2014, from Science Online. Facts On File, Inc. : http://www. fofweb. com/Science/default. asp? ItemID=WE40&ID=19229&SID=8&SearchStyle=KEYWORD&submitquery=1&InputText=isotopes Mandal, D. A. (2012, October 31). History of Nuclear Medicine.
(A. Cashin-Garbutt, Editor) Retrieved February 8, 2014, from News – Medical: http://www. news-medical. net/article/Information. aspx National Cancer Institute. (2007, April 20). Radiation Therapy Side Effects. Retrieved February 9, 2014, from National Institutes of Health: http://www. cancer. gov/cancertopics/coping/radiation-therapy-and-you/page6 New World Encyclop? dia. (2009, February 2). Radioactive Decay. Retrieved February 8, 2014, from New World Encyclop? dia: http://www. newworldencyclopedia. org/entry/Radioactive_decay PET Professional Resources and Outreach Source. (2009, June N/A).
PET Scans: Get the Facts. Retrieved February 9, 2014, from PET PROS: http://www. snm. org/docs/PET_PROS/PET. pdf Radiation Protection. (2012, July 8). Halth Effects of Radiation Effects. Retrieved February 9, 2014, from U. S. Environmental Protection Agency: http://www. epa. gov/radiation/understand/health_effects. html Rennie, R. (N/A, N/A N/A). Annihilation. Retrieved February 8, 2014, from Science Online. Facts on File: http://www. fofweb. com/Science/default. asp? ItemID=WE40&ID=19229&SID=8&SearchStyle=KEYWORD&submitquery=1&InputText=isotopes The Editors of The Encyclop? dia Britannica.
(2014, N/A N/A). Radioactive Isotope. Retrieved February 8, 2014, from Encyclop? dia Britannica Online: http://www. britannica. com/EBchecked/topic/489027/radioactive-isotope The Energy Library. (N/A, N/A N/A). Radioisotopes in Medicine. Retrieved February 9, 2014, from The Energy Library: http://theenergylibrary. com/node/523 Turkington, T. G. (2001). Introduction to PET Instrumentation. Journal of Nuclear Medicine Technology , 29 (1), 4-11. Wikipedia. (2014, February 4). Chernobyl Disaster. Retrieved February 9, 2014, from Wikipedia: http://en. wikipedia. org/wiki/Chernobyl_disaster.