Nuclear medicine/PET procedures
Positron emission tomography, or what is also known as (PET), is a certain nuclear medicine procedure. This procedure can measure the metabolic activity of cells throughout the tissues of the body. Radiology procedures such as PET are most often performed on cancer patients or patients with brain or heart conditions. Since PET helps focus on biochemical changes that take place in one’s body, it can be a very beneficial mixture of nuclear medicine and biochemical analysis. PET actually helps focus on changes in the body, such as the metabolism of the heart’s muscles.
Though PET is a form of nuclear medicine, it differs from most because it focuses on the metabolism of the body’s tissues, while other types of medicine detect the amounts of radioactive substances that have been collecting in the body’s tissue over time.
Since PET studies the metabolism of a certain tissue or organ in the body, it carries information based on the physiology and anatomy of each tissue or organ, as well as the biochemical properties. PET may also detect certain biochemical changes in a tissue or organ that can identify the start of a disease process before other, more visible changes may take place. These changes could be noticed before a computed tomography (CT scan) or even a magnetic resonance imaging (MRI) could catch it. PET scans require a small amount of a radioactive substance, which is known as radiopharmaceutical, to assist the examination process.
Who Uses PET?
Most often, PET is used by oncologists, neurosurgeons and neurologists and cardiologists. Since PET has become so advanced, it is being used by other professions all over.
PET is also great to use for other diagnostic testing, such as magnetic resonance imaging or computer tomography. Those types of tests offer more definitive answers when focusing on malignant tumors and lesions.
Advancements in PET
Fortunately, technology has brought a great opportunity to combine PET and CT. With the combination of PET/CT, physicians can diagnose and treat certain cancers and diseases.
Though PET used to be performed in PET centers only, radiopharmaceuticals are now able to offer PET scans as long as there is a PET scanner available.
Due to PET imaging becoming more available, there is a new system called the gamma camera systems that can allow patients to be scanned quicker and for a more affordable rate than a traditional PET scan. Gamma camera systems are devices that are used to scan a patient that has been injected with a small dose of radionuclides.
How Does PET Work?
PET examinations work by placing a patient in a scanning device that is then emitted by a certain radionuclide in the tissue or organ under examination.
PET scans often use natural chemicals that are used by a particular organ or tissue during the metabolic process, such as carbon, oxygen and glucose as the radionuclide. For example, a physician performing a brain scan will use the radioactive substance that is applied to glucose. That radionuclide is called fluorodeoxyglucose, or FDG. FDG is used because the brain depends on glucose for its metabolism.
For other PET scanning, different substances may be used, such as carbon, nitrogen, gallium or radioactive oxygen. It all depends on the blood flow and perfusion or the tissues and organs of interest.
Once the radionuclide has been injected into the vein through an IV, the PET scanner will slowly move across the body to examine it. Positrons are then emitted due to the breakdown of the radionuclide. As positrons are being emitted, gamma rays are created and detected by the scanner. Gamma rays are analyzed by the computer and then provide an image of the tissue or organ being studied. Based on the amount of radionuclide collected, it will affect how brightly colored the tissues or organs appear. The different levels will indicate the functions of the tissue or organ.
Why Must a PET Be Performed?
A PET scan is performed to evaluate tissues or organs that may appear diseased. PET scans can also determine the function of certain organs such as the brain or heart. Most commonly, PET scans are used to detect cancer and to evaluate the treatment for cancer.
More reasons for PET scanning may include:
- For diagnosing dementias or conditions that deteriorate a person’s mental function and neurological state such as:
- Epilepsy: a disorder in the brain that involves recurrent seizures.
- Huntington’s disease: a hereditary disease that affects the nervous system and may cause involuntary movements, abnormal posture and increased dementia.
- Parkinson’s disease: a progressing disease that affects the nervous system by causing muscle weakness, tremors and form of gait.
- To manage and treat lung cancers by staging lesions and checking the progression of the lesion post treatment.
- To examine the cancer treatment effectiveness.
- To detect reoccurring tumors earlier than other diagnostic modalities can.
- To examine the brain after trauma and to search for bleeding, blood clotting and perfusion of the brain’s tissue.
- To examine cancer that may spread to other areas of the body.
- To evaluate lesions or masses of the lungs that may have been detected on chest x-rays or chest CT scans.
- To evaluate a cerebrovascular accident or stroke.
- To examine the blood flow or perfusion of the myocardium (heart muscle) in order to determine the effectiveness of a therapeutic procedure done to improve the blood flow to the myocardium.
- To find a surgical site before surgical procedures are performed on the brain.
How Is PET Performed?
PET scans can either be done through an inpatient or outpatient basis.
Though each facility may require certain protocols, each PET scan procedure has generally this process:
- A patient must first remove any jewelry or clothing that can get in the way of the scan. If the patient must remove clothing, they will be given a gown.
- A patient must empty their bladder as much as possible before the scan takes place.
- A patient will be injected with radionuclide by either one or two intravenous lines. (These are often injected in either the arm or hand.)
- If the patient is undergoing an abdomen or pelvic exam, they may be required to have a urinary catheter to drain any urine.
- For some patients, they may be required to be positioned on a padded table in order to get an initial scan prior to the radionuclide being injected.
- The radionuclide will get injected into the IV, which will then be transmitted to the certain tissue or organ. This process takes about 30-60 minutes and the patient will remain in the facility.
- There are no health concerns to having radionuclide injected, as it has less radiation than an x-ray.
- Once the radionuclide has been fully absorbed by the tissues or organ, the scan will begin.
- Scanners move very slowly over the body in order to get the best results.
- Once the scan is complete, any IVs and/or urinary catheters will be removed.