IMAGING: PET/CT

How It Works

An integrated PET/CT scan combines images from a positron emission tomography (PET) scan and a computed tomography (CT) scan that have been performed at the same time using the same machine. A CT scan provides detailed pictures of tissues and organs inside the body, while a PET/CT scan reveals any abnormal activity. Combining these scans creates a more complete image than either test can offer alone.

The CT scan creates a 3D image of the body with an X-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a vein to provide better detail in the images.

A PET/CT scan also creates 3D pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a vein. This substance is absorbed by the body’s cells depending on how much energy they use. Because cancer cells tend to use more energy than healthy cells, they absorb more of the radioactive substance. The PET/CT scanner then detects this substance to produce images.

Why We Do It

The majority of PET/CT scans are performed for oncologic applications. Physicians utilize PET/CT scans for diagnosing, staging, re-staging and evaluating treatments for their patients. The scan helps distinguish between benign and malignant disorders by assessing tissues at a cellular level.

A PET/CT scan can also show the extent of disease. For patients whose cancer is newly diagnosed, it is important to determine if the cancer has spread to other parts of the body so that appropriate treatment can begin as soon as possible. A PET/CT scan images the entire body in a single examination, and aids the physician in detecting the primary site(s) as well as any metastases. Thanks to a PET/CT scan, painful, costly and invasive surgery, such as thoracotomy, may no longer be necessary for diagnosis.

The scan will also help physicians monitor the treatment of disease. For example, chemotherapy leads to changes in cellular activity that is observable by PET/CT long before structural changes can be measured by CT alone. This gives physicians an alternative technique to evaluate treatment plans earlier, perhaps even leading to modifications in treatment, before an evaluation would normally be made using other imaging technologies.

After treatment is complete, a PET/CT scan allows the physician to investigate suspected recurrence of cancer, revealing tumors that might otherwise be obscured by scar tissue resulting from surgery and radiation therapy.

The Experience

Plan to be at the testing center for 2 to 2 ½ hours. It is important to arrive on time. If you cannot arrive on time, please call 24 hours in advance to reschedule your test.

A PET/CT scan is not painful but it requires patience. You will receive an injection in advance of the scan. It takes 60 to 90 minutes for the material to be distributed throughout your body. During this time you will be asked to relax comfortably in a recliner in a quiet room. You will also need to be still for the entire scan, which takes 25-45 minutes depending on what your doctor has ordered.

Prep & Safety

You will receive very detailed instructions to prepare for your study. The quality of your scan depends on your adherence to these directions, so it is very important to follow them closely. If you have any questions about this procedure, please call our office to speak to a specialist. Prep may vary based on your study. Please be sure to review the instructions specific to your study.

  • Do not eat or drink for at least 6 hours before your exam, with the exception of water.
  • Drink 3-4 8-oz glasses of water within 4 hours prior to your test; empty your bladder as often as needed.
  • If your doctor has told you to take your regular medicine, you may take it with water.
  • Eat a low-carbohydrate diet the day before your exam. Foods allowed include meat, tofu, hard cheeses, eggs, unsweetened peanut butter, oil, margarine, butter and non-starchy vegetables like broccoli, spinach, and green beans.
  • Do not eat: cereals, pasta, dry beans, sugar, candy, bread, rice, alcohol, gravy, jams, jellies, honey, and starchy vegetables like peas, corn, and potatoes.
  • Limit exercise the day before your exam.
  • Do not consume nicotine or caffeine 4 hours prior to your exam.

Safety notes

Please tell your doctor if you’ve ever had an allergic reaction to an enhancing agent or iodine; special medicine may be prescribed for you to take before your exam. If you are anxious about the test, or are claustrophobic, tell your physician before the day of your exam. Your doctor may choose to prescribe medicine to help you relax. Other nuclear medicine procedures should not be scheduled the same day as your PET/CT exam.

For your safety, please notify our scheduling department and technologists if you:

  • Are pregnant or breast-feeding.
  • Have ever had an allergic reaction to an enhancing agent or iodine.
  • Find it difficult or uncomfortable to lie flat on your back.

Prep Forms

Your Results

A highly specialized radiologist will interpret your images and prepare a diagnostic report for your physician. The results of our study will be reported to your physician within 48 hours. We provide consultation and analysis of the scans and collaborate with your physician if requested. However, only your physician is authorized to report the results to you.

COMMON QUESTIONS
Q.
How does a PET/CT scan differ from CT or MRI scans?
A.
CT and MRI scans are anatomic imaging modalities, which means that they look at the size and shape of organs and body structures. A PET/CT scan is a metabolic imaging modality, which means it looks at cellular activity. The information collected from a PET/CT scan is different from any other test that is available.
Q.
Is PET/CT scan safe?
A.
The risks associated with a PET/CT scan are very minimal. The quantity of radiation is low and the radiopharmaceutical degrades quickly so that no detectable radioactivity is present after several hours. In addition to the radioactive decomposition, the remaining radiopharmaceutical is eliminated from the body through urine. Family members are not at risk for exposure because approximately 90% of the radioactivity has left the body or decomposed before the patient has left the center.
Q.
Can I have a PET/CT scan if I’m allergic to contrast dyes?
A.
Yes
Q.
What steps do you take to reduce radiation?
A.
We adhere to the As Low As Reasonably Achievable (ALARA) principle, using tools that automatically adjust the radiation dosage based on body type and anatomy. As part of that commitment, we invested in a new technology called iDose that lowers the amount of radiation patients receive by 50% to 70%. The amount of radiation you receive varies by body type and the anatomic region being scanned. Your CT technologist can estimate your radiation dose at the time of your scan. If you had the same CT scan at Oregon Imaging Centers prior to our iDose, your technologist can determine the percentage of radiation reduction.
Q.
Is there an IV involved with the PET/CT?
A.
Yes, please read the “What to Expect” section for details.
Q.
How should I prepare for my CT?
A.
You will receive instructions when you schedule your appointment. You can also refer to the “prep” section of the website. Be sure to review the instructions for your particular study, as they can vary based on type of study.
Q.
Why is there a special diet?
A.
PET/CT scan measures the body’s metabolism. By adhering to the special diet and exercise restrictions we can better measure the metabolic rate of different areas within your body.
Q.
What is a radiopharmaceutical?
A.
A radiopharmaceutical is a radioactive drug. The most commonly used PET/CT radiopharmaceutical is a radioactive form of glucose (sugar). To begin the PET/CT procedure, a small amount of glucose is injected into your bloodstream. There is no danger to you from this injection. Glucose is a common substance that every cell in your body needs in order to function. Diabetic patients do not need to worry; it would take 1,000,000 doses of this radiopharmaceutical to equal the glucose in 1 teaspoon of sugar. Radiopharmaceuticals must pass multiple quality control measures before it is used for any patient injection.
Q.
Are there any potential side effects to a PET/CT scan?
A.
There are no side effects to having a PET/CT scan. Make sure you drink plenty of water and check with your physician if you have any concerns.
Q.
How often should I have a PET/CT scan?
A.
If you are under a physician's care, you should follow your physician's recommendations for frequency of PET/CT scans.
Q.
Why is PET/CT not well known?
A.
PET/CT has been around for years, but originally was used only in research. As the technology grew, PET/CT procedures were performed only in dedicated imaging facilities that had ready access to a cyclotron and a radiochemistry lab to make the radiopharmaceutical. Now, private companies are producing radiopharmaceuticals for distribution to imaging facilities across the country, making it feasible for more medical facilities to offer PET/CT scanning. Oregon Imaging Centers has been performing PET/CT scans in the community for nearly 15 years.
Q.
How many PET studies are performed per year?
A.
Approximately 1.5 to 1.7 million PET/CT scans were performed last year. The number of PET/CT scans performed increases dramatically every year.
Q.
Is a PET/CT scan painless?
A.
The only pain involved is the needle prick when you receive the radiopharmaceutical injection, which does not differ from any other type of injection.

Types of scans

FDG Metabolic Brain study

What: A PET brain scan is used to either diagnose, stage, restage, or monitor therapy response to primary brain cancers or metastatic brain tumors. FDG PET/CT brain studies can also differentiate different types of dementia.

Images are acquired of just the brain after the same uptake period used in all other PET exams.

What to expect: Plan to be at the testing center for 1 ½ to 2 hours. It is important to arrive on time. If you cannot arrive on time, please call 24 hours in advance to reschedule your test.

A PET-CT brain study is not painful but it requires patience. You will receive an injection in advance of the scan. It takes 60 minutes for the material to be distributed throughout your body. During this time you will be asked to relax comfortably in a recliner in a quiet dark room. You will also need to be still for the entire scan, which takes 15-25 minutes depending on what your doctor has ordered.

Prep: You will receive very detailed instructions to prepare for your study. The quality of your scan depends on your adherence to these directions, so it is very important to follow them closely. If you have any questions about this procedure, please call our office to speak to a specialist. Prep may vary based on your study. Please be sure to review the instructions specific to your study.

  • Do not eat or drink for at least 6 hours before your exam, with the exception of water.
  • Drink 3-4 8-oz glasses of water within 4 hours prior to your test; empty your bladder as often as needed.
  • If your doctor has told you to take your regular medicine, you may take it with water.
  • Do not consume nicotine or caffeine 4 hours prior to your exam.

Safety notes: Follow the same safety guidelines as the general PET/CT.

Sodium Fluoride (NaF18) Bone Scan

What: An NaF PET/CT Bone Scan is used to detect areas of bone abnormality due to fracture, tumors or other bone diseases. Most often, this exam is used for oncologic applications.

An image is taken of the entire skeletal system determining if cancer or other disease has spread to any bones in the body. This allows appropriate treatment to begin as soon as possible.

What to expect: Plan to be at the testing center for 2 to 2 ½ hours. It is important to arrive on time. If you cannot arrive on time, please call 24 hours in advance to reschedule your test.

The technologist will start an IV and inject a small amount of sodium fluoride. The IV will be removed and you will be asked to relax quietly in a comfortable recliner while the sodium fluoride works its way through your body. You may read or use electronic devices during the uptake period for a sodium fluoride bone scan.After the resting period you will be asked to empty your bladder and the technologist will escort you into the scanning room where you will lie down on the scanner table. It is important that you are comfortable and will need to lie as still as possible for 25-35 minutes as the table passes slowly through the scanner acquiring several sets of images. The procedure is painless and has no side effects.

Prep: The prep for the bone scan is different than a general PET/CT. You may continue to eat and drink normally prior to and after the scan. If you are on any medications, you may continue to take them. Drink plenty of fluids before and after the exam.

Safety notes: Follow the same safety guidelines as the general PET/CT.