What is nuclear medicine and molecular imaging?
Nuclear medicine and molecular imaging allow us to visualize and treat patients at the cellular and molecular levels. Nuclear medicine allows scientists and physicians to:
- Locate disease
- Better understand the pathways of disease
- Improve the selection of therapy
- Treat disease
- Monitor patient response to treatment
How are nuclear medicine and molecular imaging used?
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- Imaging: Nuclear and molecular diagnostic imaging studies are used for virtually every major organ system in the body and include scans for oncology, neurology, and cardiology.
- Therapy: Nuclear medicine procedures are approved to treat thyroid cancer, prostate cancer, and neuroendocrine tumors. Clinical trials are underway to study its use in treating many other diseases.
- Research: In the laboratory, nuclear medicine and molecular imaging helps scientists gain a better understanding of the molecular pathways and mechanisms of disease and are contributing to the accelerated development of new and more effective drugs.
Why is nuclear medicine imaging unique?
Conventional imaging-such as x-rays, MRI and ultrasound-use external sources of energy to produce pictures of bone and soft tissue, depicting anatomical structure. In nuclear medicine and molecular imaging procedures, an energy source is introduced into the body, where it attaches to a specific tissue, organ or process and is then detected by a camera or scanner to provide information on organ function and cellular activity.
Because disease begins with microscopic cell changes, nuclear medicine and molecular imaging can identify disease in an earlier, more treatable stage. In many cases, the unique information obtained by these scans either would require more invasive procedures, such as biopsy or surgery, or would simply be unattainable.
How does this type of imaging work?
Nuclear medicine and molecular imaging use an imaging compound that is introduced into the body, usually by injection. This compound is made up of two parts:
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- Radiotracer—a very small amount of radioactive material that produces a signal that can be detected by a gamma camera, SPECT scanner, or PET scanner
- Targeting molecule—a molecule such as a protein or a monoclonal antibody that is designed to accumulate in a specific organ or attach to certain cells, such as cancer cells
After injection, the patient is imaged by a camera or scanner, which detects the compound’s signals and creates detailed images.
Examples of anatomical imaging (CT) compared to functional imaging (PET). In this patient, the CT scan (A) is negative for disease recurrence. However, the PET scan (B) shows a spot suggesting malignancy. The PET/CT fusion image (C) gives a clearer picture of what is happening. Reference: http://jnm.snmjournals.org/content/49/6/938.full
What are the different types of nuclear medicine and molecular imaging?
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- PET imaging—Positron emission tomography is performed using radiotracers such as FDG, PSMA, and FES, this type of imaging often is combined with CT or MRI studies to locate areas of abnormal cell activity.
- SPECT imaging—Single-photon emission computed tomography is performed with a gamma camera that rotates around the patient and creates three-dimensional images providing information on blood flow and organ function. Many SPECT studies are combined with CT studies.
- Hybrid Imaging— The combination of two imaging techniques allows information from two different types of scans to be viewed in a single set of images. PET/CT, PET/MRI, and SPECT/CT have become standard diagnostic tools because they provide detail on both the anatomy and the function of organs and tissues.
- Optical imaging—This includes numerous technologies that use light to measure cell function and characteristics. Scientists engineer tiny molecules, such as proteins that naturally emit light, to attach to specific cells or chemicals inside the body. Highly sensitive optical detectors track the movement and activity of these imaging agents and measure how tissue absorbs light. This type of imaging is primarily in the research phase and is not yet widely used.
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What are nuclear medicine therapies?
Because nuclear medicine can target cells so precisely, the same technology that allows for precision imaging also offers an excellent means for delivering treatment.
One of the earliest applications of nuclear medicine—radioactive iodine (I-131) ablation—has been a highly successful treatment for thyroid and hyperthyroidism for nearly eighty years. In I-131 targeted therapy, radioactive iodine is introduced into the body and absorbed by the thyroid cells or thyroid cancer cells, where it kills them.
In the past ten years, additional therapies have been introduced and approved to treat prostate cancer (using lutetium-177 and 223-radium) and neuroendocrine tumors (using lutetium-177 and yttrium-90). Clinical trials are underway to explore many additional therapies.
Because these therapies are highly selective—meaning they damage the cancer cells while limiting radiation exposure to healthy tissue—they generally are well tolerated and can produce fewer side effects than less targeted treatments.
Are Nuclear Medicine and Molecular Imaging Safe?
Nuclear medicine and molecular imaging procedures are noninvasive and safe. Nuclear medicine specialists use the ALARA principle (As Low As Reasonably Achievable) to carefully select the amount of radiotracer that will provide an accurate test with the least amount of radiation exposure to the patient. The actual dosage is determined by the patient’s body weight, the reason for the study, and the body part being imaged. In addition, newer imaging technologies are constantly emerging to reduce radiation exposure to patients while maintaining the diagnostic accuracy of the test.
Are Nuclear Medicine and Molecular Imaging Procedures Covered by Insurance?
Medicare and private insurance companies cover the cost of many nuclear medicine and molecular imaging procedures. You should check with your insurance company for specific information on your plan.
What Is the Future of Nuclear and Molecular Imaging?
Every day, nuclear and molecular imaging procedures make a difference in the lives of patients by contributing to the detection, diagnosis, treatment, and monitoring of disease. With the development of new technologies and imaging agents, many of which are now in clinical trials, nuclear medicine and molecular imaging promise to continue to deliver improvements to patient care.
Information on clinical trials specific to nuclear medicine can be found on the SNMMI website; information on all clinical trials in the United States can be found at www.clinicaltrials.gov; and information on how clinical trials work can be found in the SNMMI Patient Center.