Saturday, March 2, 2013

Understanding Nuclear Medicine

Nuclear medicine involves the use of small doses of radiation for a variety of medical treatments or tests (Stanford, 2013, para. 1). Common examples of nuclear medicine are : CT- scans, PET- scans, MRI’s scans, and with these advancements early diagnosis of disease, disorders and dysfunction of the heart, thyroid, lungs and kidney became common place.  Diagnoses for infection, tumor spread, fractures, and injuries are the most common uses of nuclear medicine today. However, some nuclear medicine is used in the treatment of cancer also. While some may worry about the effects of nuclear medicine, nuclear medicine has been evaluated as safe, and as with all medicine that is not over the counter, it is always administered only after a patient is evaluated and a determination made that this type of therapy will work best, and/or the benefits outweigh the risks. In this paper we will explore the basics concepts behind nuclear technology, and the advantages of  nuclear technology like Positron Emission Tomography (PET) scans, X-ray computed tomography (CT), Magnetic resonance imaging (MRI), and Nuclear medicine therapy using radiopharmaceuticals.


The National Academies Press (2007), describes Nuclear Medicine as a highly multi-disciplinary science that creates and utilizes “instrumentation and radiopharmaceuticals to study physiological processes and non-invasively diagnose, stage, and treat diseases” (para. 1). To further clarify, the nuclear medicine radiopharmaceutical use is either “a radionuclide alone, or a radionuclide that is attached to a carrier molecule like a drug, protein, peptide or particle” (The National Academies Press, 2007, para. 2). When administered by injection, swallowing, or inhalation these small doses of radiopharmaceuticals will accumulate in the organ or tissue under treatment, this allows for the problem to be properly diagnosed or treatment to proceed with precision that is unmatched by previous technologies (The National Academies Press, 2007, para. 2).

Currently there are 2 ways to use nuclear medicine- to diagnosis and to give treatment. In diagnostic imaging internal images are created by an external scanner device in conjunction with the radiopharmaceutical or radionuclide that has been ingested into the body to create complex images. Unlike x-ray,  ultrasound or any other diagnostic tools that are used to determine the presence of disease based on structural appearance, nuclear medicine is capable of determining the cause of the medical ailment based on the function of the organ, tissue, or bone (Stanford, 2013, para. 1). Targeted radionuclide therapy is an example of nuclear medicine that does not exemplify an imaging or diagnostic tool. Targeted radionuclide therapy is a type of cancer treatment that delivers therapeutic doses of radiation to malignant tumors using a radiolabeled molecule that is designed to seek out certain cells and deliver the radiation to only the infected or sick cells (National Research Council & Institute of Medicine, 2007).

Previously, radiation therapy involved subjecting the area of the body affected with a cancer tumor to external radiation therapy using a beam of high-energy x rays (The National Academies Press, 2007, p .60). However, this procedure was only partially successful because there was no precise way too be sure that the infected cells nearby have been stopped.(The National Academies Press, 2007, p. 60) Previously, external radiation therapy was the best way to target these cells and stop these cells from the process that causes them to grow and divide (The National Academies Press, 2007, p. 60). Today, current cancer therapies are evolving to utilize radiation nuclear technology in ways that target cancerous cells, while leaving healthy cells unharmed (The National Academies Press, 2007, p. 60). This targeted radiopharmaceutical therapey have even proved to be effective with malignant lymphoma (The National Academies Press, 2007, p. 60).
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Nuclear medicine uses ionizing radiation in the form of electromagnetic rays, like X-rays and gamma rays- or particles like, alpha and beta particles (Health and Safety Executives, 2013, para. 1). Interestingly, ionizing radiation can occur in nature “from the radioactive decay of natural radioactive substances such as radon gas and its decay by- products”, however today it can also be made by man (Health and Safety Executives, 2013, para. 1). Nuclear medicine is not only safe and painless, but it is also a cost-effective diagnostic and treatment  tool that assists care providers in giving  treatment to otherwise inaccessible parts of the human anatomy (Stanford, 2013, para. 9). The amount of radiation one might receive in a diagnostic or common procedure is minimal, equivalent to what one might get from the environment in a few months of normal activity or at the hospital from 1 x-ray (Stanford, 2013, para. 6). Additionally, the radiation used is not active for long within the body, losing  its radioactivity fast it is quickly eliminated from the body through naturally occurring functions (Southern Nuclear Imaging, 2012, para. 6).

Rather than like its counterpart external radiation therapy, targeted radionuclide therapy is more like chemotherapy that only targets the affected cells (The National Academies Press, 2007, p. 60). This systemically administered and targeted radiotherapy is still a radiation therapy, it is just more complex using a molecule labeled with a radionuclide as a delivery system for the radiation. In this system, the known antitumor effects of ionizing radiation have been utilized in combination with a precision delivery system designed for cancer cell targeting (The National Academies Press, 2007, p. 60). A characteristic of these radionuclide’s is that they are known have what is known as a “bystander” or “crossfire” effect- which gives them the potential of also targeted close by cells that are affected with cancer and potentially treat them too (The National Academies Press, 2007, p. 60). This biological effect is a result of energy absorbed from radiation emitted by the radionuclide (The National Academies Press, 2007, p. 60). Unlike its counterpart nuclear imaging which uses gamma rays, all radionuclide’s utilized for targeted radionuclide therapy must have a short path length (The National Academies Press, 2007, p. 60). As a result, they utilize beta particles, alpha particles, and Auger particulate radiation (The National Academies Press, 2007, p. 60).

After the medicine is administered in nuclear imaging, the body naturally processes as the medicine or radioactive substances works its way through the body continuously emitting an invisible radiation, called gamma rays. Only when the medication has reached to the affected tissue can a scanner then be used too to demonstrate biochemical changes within the body (The National Academies Press, 2007, para. 2). Depending on the type of radiopharmaceuticals used, the location of the structure within the body, how fast your body processes, and how the medication was administered, the time it can take for the medication to reach its destination within the body can vary. When used in imaging, it may take up to a day or two for the medication to reach the location. Therefore it may be necessary for the medication to be administered up to two days before the scan (Southern Nuclear Imaging, 2013, para. 6).

The National Academies Press, (2007) states that conventional ultrasound, computed tomography [CT], or magnetic resonance imaging [MRI] can provide suitable imaging for basic structures of anatomy, but for “quantitative functional information about normal tissues or disease conditions in living subjects” nuclear medicine or a PET/CT is the choice diagnostic tool (para. 2). When the scan takes place, you will be positioned under or in a machine that holds the gamma camera used to create the images (Southern Nuclear Imaging, 2013, para. 6). The camera will be placed near the area that is to be inspected, and the camera will take pictures of the radioactive tracers (Southern Nuclear Imaging, 2013, para. 6). During the scan, the gamma camera (PET scanner) and/or probe will work with a computer to create images that show amazing detail by measuring the amount of radiotracer present and/or absorbed (Stanford, 2013, para. 4). These images will be used so they can see accurately what type of problems exists, and if it needs future treatment. 

Stanford School of Medicine, (2013) describes Positron Emission Tomography – Computed Tomography [PET/CT] scanning is a biological imaging examination that can image the biological chemistry and the processes of disease within the body (para.2).  PET is useful in the detection and staging of  most cancers, and can also give vital early information about neurological disorders, like Alzheimer's and lastly, heart disease (Stanford, 2013, para. 2). The PET is capable of giving information about the function of a tissue, and is so accurate that it can detect even the smallest tumors, and smallest changes with the heart and brain (Stanford, 2013, para. 3). During one scan, a PET/CT scan can image the entire body and discover hidden illness (Stanford, 2013, para. 4). Research indicates that early detection can give you time to make decisions with a doctor about how to treat these underlying diseases accurately, and quite often, this has a more successful result. Ultimately, the difference between PET/CT and MRI scan  result is CT and MRI scan results only show details about the structure of your body, whereas, a PET/CT-scan results can also relay information about function too (Stanford, 2013, para. 4).

A CT scan uses special x-ray equipment, and sometimes this equipment is used with a contrast material to produce pictures that can relay anatomic information to your care provider (Stanford Hospital & Clinics, 2013, para. 1). In some cases, a process called image fusion or co-registration is used to create special views and images by superimposing a CT or MRI with a PET scan (Stanford Hospital & Clinics, 2013, para. 3). However, just as often your PET is now done with a combined PET/CT scanner machine which does the two tests simultaneously (Stanford Hospital & Clinics, 2013, para. 4). These newer machines provide images that pinpoint the location of “abnormal metabolic activity” within the body and are therefore more accurate than when the each test is done independently (Stanford Hospital & Clinics, 2013, para. 1). While the MRI or magnetic resonance imaging scan does not use radiation or X-rays, it does use a magnet and computer to create images of your internal organs and structures (Stanford Hospital & Clinics, 2013, para. 1). The computer and magnet work together to make images that can be read off the computer by your care providers (Stanford Hospital & Clinics, 2013, para. 1). This type of imaging is often used while evaluating the  brain, neck, spinal cord, chest, heart, abdomen, joints, or blood vessels (Stanford Hospital & Clinics, 2013, para. 2).

During a nuclear scan side effects are extremely rare. However, when using radiation or radiopharmaceuticals some swelling of the salivary glands or nausea may occur, but these are temporary, treatable, and sometimes all together preventable (Southern Nuclear Imaging, 2013, para. 21). Typically, nuclear medicine scans do not require a long stay in the hospital, and usually you are only required to stay at the hospital for a few hours after the procedure then are released later that day (Southern Nuclear Imaging, 2013, para. 6). In some limited cases, particularly where there is concern about the nuclear waste being excreted from the body and not disposed of properly a short stay in the hospital may be required (Southern Nuclear Imaging, 2013, para. 6). However, more often than not this requires just visit or two to the hospital (Southern Nuclear Imaging, 2013, para. 11).

When nuclear medicine is used as a treatment, such as in cancer treatments, “highly targeted radiopharmaceuticals may be used to deposit lethal radiation at tumor sites”(The National Academies Press, 2007, para. 2). Treatments for “hyperthyroidism, thyroid cancer, blood imbalances, and any bony pain from certain types of cancer” are also available as a result of nuclear medicine (Southern Nuclear Imaging, 2013, para. 11). Overactive thyroid, thyroid cancer, and cancer are well known and widely used applications of treatments that utilize nuclear medicine (Southern Nuclear Imaging, 2013, para. 12). Treatments for arthritis can be done by injecting the radiopharmaceuticals into the body, or very commonly right into the joints (Southern Nuclear Imaging, 2013, para. 12). Newer applications, like those for the relief of tumor pain that has spread to bone, are also available by an intravenous injection of radiopharmaceuticals (Southern Nuclear Imaging, 2013, para. 12).

The utilization of nuclear medicine to diagnose and treat diseases that have such devastating effects is a promising development for those who are affected by them. The smalls risks associated with nuclear medicine clearly demonstrate that this application of science when used appropriately can have great success and should be further explored. Currently, applications of nuclear medicine are limited by the fact that they are at times time-consuming to administer. I personally feel the time is well spent doing it right. As these technologies can uncover and treat illnesses that previously had eluded us until it was too late and death was almost certain, today this type of treatment can be life saving for a patient. These scanning techniques and targeted therapies are sure to only get better as our understanding of nuclear medicine broadens. These advancements in nuclear medicine have paved the way for the better treatment of disease and suffering in human kind over the years, therefore future nuclear medicine will likely do so too. While some may worry about the effects of nuclear medicine, nuclear medicine has been evaluated as safe, and as with all medicine that is not over the counter, it is always administered only after a patient is evaluated and a determination made that this type of therapy will work best, and/or the benefits outweigh the risks.

References
Health and Safety Executives. (2013). Radiation. Health and Safety Executives. Retrieved from http://www.hse.gov.uk/radiation/ionising/
National Academies Press. (2007). 2 Nuclear Medicine. Advancing Nuclear Medicine Through Innovation. The National Academies Press. Retrieved from. Press.http://www.nap.edu/openbook.php?record_id=11985&page=17
National Academies Press. (2007). 2 Nuclear Medicine. Advancing Nuclear Medicine Through Innovation. The National Academies Press. Retrieved from. http://www.nap.edu/openbook.php?record_id=11985&page=60
National Research Council & Institute of Medicine. (2007). Targeted Radionuclide Therapy; Advancing Nuclear Medicine Through Innovation. Committee on State of the Science of Nuclear Medicine. National Academies Press (US). Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK11464/
Southern Nuclear Imaging. (2012). What is Nuclear medicine? Southern Nuclear Imaging. Retrieved from http://www.nuclearimaging.com.au/whatis.htm
Stanford. (2013). Nuclear Medicine. Stanford School of Medicine.  Retrieved from http://nuclearmedicine.stanford.edu/patient_care/
Stanford Hospital & Clinics. (2013). MRI. Stanford Hospital & Clinics. Retrieved from. http://stanfordhospital.org/clinicsmedServices/medicalServices/imaging/services_mri.html
Stanford Hospital & Clinics. (2013). CT/PET. Stanford Hospital & Clinics. Retrieved from. http://stanfordhospital.org/clinicsmedServices/medicalServices/imaging/services_petct.html