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Patient FAQ
1. What is PET?
Positron Emission Tomography (PET) is a non-invasive, diagnostic imaging technique that can detect certain diseases before other modalities like computed tomography (CT) or magnetic resonance imaging (MRI). PET/CT is unique because it produces images of metabolic function; in particular, it shows how glucose is used metabolically by the brain, heart and certain cancers, and can detect physiological changes of organs. CT and MRI are unlike PET because they are used to detect structural changes in the body. This is important because functional change, as it relates to metabolic activity, often predates structural change in tissues and organs. PET/CT images may therefore demonstrate the existence of disease long before it would be revealed by modalities like CT and MRI.
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2. How is a PET/CT scan used?
PET is most commonly used to diagnose cancer and determine how far the cancer has progressed. It is a medical device that can accurately image many organs of the body with a single pass to allow determination of malignancy. It can also provide information to determine whether a primary cancer has metastasized to other parts of the body. PET/CT is particularly helpful to doctors diagnosing and staging cancers such as: breast, colorectal, head and neck, esophageal, lung, lymphoma, melanoma, musculoskeletal tumors, ovarian and pancreatic.
PET technology is frequently used for certain cardiology (heart) patients. It is also effective in assessing various neurological diseases such as Alzheimer’s and Parkinson’s disease as well as for the evaluation of stroke and epilepsy.
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3. Benefits of PET
PET may enable physicians to:
- Visualize tumor’s and allow for an early diagnosis
- Identify if cancer has spread
- Determine if cancer has returned or if it is only scar tissue from surgery
- Determine and track the efficacy of a patient’s therapy
- Eliminate more invasive exams or surgeries
- Assess or “stage” cancer prior to surgery or treatment
- PET is beneficial for certain cardiac diagnoses
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4. What are some of the diseases that PET/CT diagnoses?
PET is making critical contributions to effective patient management in four primary medical disciplines: oncology, cardiology, neurology, and psychiatry. Currently, PET/CT is most commonly used in oncology, specifically to diagnose and stage lung cancer, Solitary Pulmonary Nodules, head and neck cancer, colorectal cancer, lymphoma, breast cancer, esophageal cancer, and melanoma because Medicare reimburses only for these oncological studies at the present time. As clinical research continues, more applications are likely to be covered. In Cardiology it is used to determine if the heart muscle is viable prior to surgery. In Neurology it is used differentiate recurrence of brain tumor from scar. It is also used to determine foci of epileptic seizures. In psychiatry it is useful to help differentiate various types of mental disease.
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5. What are the advantages of PET’s diagnostic capabilities?
PET can often diagnose disease before structural changes become detectable. Early detection of disease can potentially improve a patient's prognosis. Once a diagnosis has been made, PET/CT helps your physician manage therapy by monitoring responses to a given regimen and by providing early feedback on its efficacy. In some cases, PET/CT can replace multiple diagnostic procedures with a single exam. In oncological situations, PET/CT can identify distant metastases that may affect the course of treatment and therefore change the way your physician manages your situation. PET/CT is also used to help predict the prognosis for surgical procedures to eliminate those that will not benefit the patient. All of the feedback provided by PET/CT can help reduce or avoid the cost of ineffective treatments or unnecessary hospitalization.
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6. PET/CT and Cancer
PET is considered effective in:
- The early detection of cancer.
- Confirmation of distant metastasis
- Staging the full extent of Cancer
- Differentiating between tumor recurrences from radiation necrosis or post-surgical changes.
- An earlier assessment of the effectiveness of chemotherapy
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7. PET/CT and Cardiovascular Disease
Physicians can differentiate between muscle damage from living muscle by measuring both metabolic rate and blood flow (perfusion) within the heart. This information can enhance the diagnosis of a patient’s condition.
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8. PET/CT and Neurological Disease
PET can depict areas where brain activity differs from the norm. This helps physicians better diagnose Alzheimer’s disease, Parkinson’s disease, epilepsy and neurological conditions. In Epilepsy, PET/CT is able to localize areas, causing epileptic seizures, of the brain more accurately than other modalities and help physicians determine if surgery is a viable option.
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9. What happens when I arrive for my PET/CT exam?
Report to the reception desk at your appointment time. You will be asked questions about your medical history and any previous exams. Then you will receive an injection of a radiopharmaceutical, which is usually a sugar compound tagged with a short-lived radioisotope. The FDG is used at a different rate by different parts of the body and represents the metabolism of sugar. Different colors or degrees of brightness on a PET/CT image represent different levels of body function. For example, because healthy tissue uses glucose for energy, it accumulates some of the FDG, which will show up as background area on the PET/CT images. Cancerous tissue which uses more glucose than normal tissue will absorb more of the substance and appear brighter on the PET/CT images.
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10. What happens during the PET/CT scan?
The PET/CT technician will ask you to lie down on the scanner table, relax and be very still. The table will then slowly pass through the PET/CT scanner. The PET/CT scanner detects and records the rays emitted from the radioisotope. A computer reconstructs images based on the data collected by the scanner. The scanning time required depends on the scan your doctor ordered and varies from fifteen to sixty (15-60) minutes.
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11. Should I be concerned about radiation?
No, the radiation exposure one receives while undergoing a PET/CT exam is well within the limits recommended by the FDA for radiological procedures and is equivalent to what one might receive when undergoing a CT scan or spinal x-ray.
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12. How long does the exam last?
Most patients should expect to spend at least two hours at the hospital, although the type of study being performed will determine the exact length of time. In most exams, patients are injected and wait for approximately forty (40) minutes before scanning begins, and the scanning process varies from fifteen to sixty (15-60) minutes depending upon the scan your doctor ordered.
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13. Is there any preparation for the exam?
Yes, your physician will give you specific instructions, but the following describes preparations typical for each type of study. In all cases, you will be asked to wear comfortable clothing, and in many cases you will not change for this exam. In some cases, a catheter or an IV may need to be placed to assure image quality.
Brain Study:
No Preparation is necessary
Head and Neck Study:
No preparation is necessary
Cardiology or Heart Study:
Follow your normal routine and eat your normal meals before the study. Follow your normal medical regimen as directed by your doctor
Breast or Lung Study:
You will be asked not to eat for a minimum of six (6) hours before the exam. Please do not chew gum, eat mints or anything with sugar or sugar substitutes during the six (6) hours before the exam because this could interfere with the results. You may drink a small amount of water and take normal medicines.
For All Other Scans:
You will be asked not to eat or drink anything but water six to eight (6 – 8) hours before your exam. Please do not chew gum or use any mints because this could interfere with the results.
If you take medications, drink only plain water to swallow them. In some cases, your physician will write a prescription for a bowel preparation, Golytely. Follow the instructions you receive on the evening prior to your exam. Please remember, the instructions described above are typical and do not replace specific instructions given to you by your physician or the hospital.
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14. What if I need to cancel my appointment?
If for any reason you are not able to keep your appointment, you must call the facility to cancel 24 hours in advance. The radiopharmaceutical is ordered specifically for your test. A charge may be imposed if you do not cancel the exam.
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15. How do I find out the results of my exam?
Your physician or healthcare provider will present the results of your exam as part of the normal course of treatment.
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16. Your Appointment is Important
Please provide 24 hours notice to your hospital’s radiology department if you cannot keep your appointment. This procedure uses a safe tracer (FDG) for this study and must be ordered 24 hours in advance of your scan. If your appointment is not cancelled with at least 24 hours notice, you may be charged for the FDG. As with all medical procedures, please bring your insurance card with you.
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