Everything You Need to Know About a PET Scan

How long does a PET scan take? When can I expect my results? We answer these questions and more.

A positron emission tomography (PET) scan is an advanced medical imaging technique that uses a radioactive substance to examine internal organs and tissues. Doctors use PET scans to ensure an accurate diagnosis and to monitor the progress of diseases. This article will explain how PET scans work, what they’re used for and how long it takes to get your results back.

 

 

What is a Positron Emission Tomography (PET) scan?

A PET scan is an advanced imaging procedure that uses a radioactive tracer to assess the function of certain organs and to look for diseases like cancer, brain disorders and heart disease.

What is a radiotracer and when is it used in PET imaging?

A radiotracer is a radioactive sugar substance used in nuclear medicine to treat or evaluate patients. In a PET scan, that radioactive substance is tracked as it moves through cells, helping visualize how tissues and organs function.

The tracer is different from the contrast material used in CT scans. During a PET scan, the radiotracer collects in cells that require a lot of energy, like cancer cells. The tracer substance emits positrons, which the PET scanner detects and compiles into detailed images.

A radioactive drug called fluorodeoxyglucose (FDG), a type of radioactive glucose, is most commonly used. Usually the radiotracer is administered to patients by injection and it takes about an hour to be absorbed.

What is the difference between a PET scan and a CT scan?

A CT scan uses multiple X-rays to create cross-sectional images of different areas of the body, while a PET scan uses a radiotracer to capture the function of organs and tissue as well as images.

While a PET scan shows changes at the cellular level, a CT scan provides anatomic information of hard and soft tissues. A PET scan can find abnormal activity and changes to your body sooner, and it can be more sensitive than other imaging tests.

The two techniques are often used together. A PET-CT scan is a medical imaging test that delivers a PET scan and a CT scan at the same time. The procedure combines the views from the two different studies on one PET-CT scan image to give the radiologist a more thorough view of your body.

How long does a PET scan take from start to finish?

After the radiotracer is issued, it takes approximately an hour to work through your system. The length of the PET scan itself varies.

Some scans take 30-60 minutes if only a single organ is being imaged. Complex full-body scans can take two hours or more.

 

 

What does a PET scan show?

The most common reasons for getting a PET scan is to identify cancer or monitor cancer treatment. However, PET scans are also used to:

• Assess decreased blood flow to the heart to monitor heart disease
• Detect recurrent tumors (earlier than with other kinds of imaging tests)
• Monitor brain disorders and investigate the cause of seizures
• Investigate reduced blood flow and other changes in renal function

 

How can patients best prepare for PET scans?

It’s important to read all the information contained on your requisition. Ask the hospital or imaging clinic if there are any special instructions. Otherwise, there are several standard PET scan prep recommendations for patients, including:

• Don’t drink alcohol and avoid tobacco and caffeine for 24 hours before your scan
• Refrain from eating or drinking anything for 4-6 hours before your appointment
• Don’t perform any strenuous exercise the day before your PET scan
• Choose comfortable clothing without belts, buttons or metal (including zippers)
• Depending on what part of the body is being scanned, you may be asked to wear a hospital gown
• Inform the staff when you book your appointment if you have diabetes or are pregnant or breastfeeding

Are there any medications that patients should avoid taking before a PET scan?

It’s very important to inform the imaging clinic well before your scan if you have diabetes. Because the radioactive drug is a type of glucose, the clinic will have a separate preparation protocol with detailed instructions for people who require insulin.

Are there any potential risks or side effects associated with a PET scan?

The level of radiation is higher in a PET scan than in a CT scan, with a radiation exposure number of 7-10 (versus 1-2 for a CT scan). Overall, however, the exposure numbers are still minimal.

The levels of radiation exposure during a PET scan are very low and allergic reactions to the radioactive tracer are extremely rare. But the hospital will carefully monitor you during your PET scan, just to be sure.

PET scanners are small, enclosed spaces, which can trigger anxiety or claustrophobia in some patients. If you suffer from either condition, you can request a short-term, fast-acting sedative.

What should patients avoid after a PET scan?

You can resume most normal activities after a PET scan, though if you took a sedative, you’ll need someone to drive your home afterwards.

It will take 12-24 hours for the radiotracer to pass out of your body. Be sure to drink plenty of fluids after the test to help flush the radioactive glucose from your system. If you feel any symptoms such as itchy eyes, rashes, sneezing, tremors, pain, nausea, vomiting, dizziness, contact your doctor immediately.

Your doctor might also recommend you avoid close contact with babies, children and/or pregnant women for 24-48 hours after your scan. Women who are breastfeeding should pump breast milk before their appointment.

 

How to understand your PET scan results

Your results will contain PET scan images and a radiologist’s report full of complex medical terms. Always review your PET image results with your referring physician at a follow-up appointment.

Ahead of that conversation, it can help to familiarize yourself with some of the terminology commonly found in your PET scan report.

Here are some of the terms you’ll find:

• SUV (Standard Uptake Value): A ratio defining the activity of the radioactive tracer in a specific area of a PET scan image captured at a specific point in time. An increase in SUV over time can indicate new or aggressive cancer growth.
• FDG uptake: The amount and rate of the radioactive tracer “taken up” or used by cells. Areas with abnormal uptake may require further investigation.
• Deauville score: A score from 1 to 5, which indicates the least to most FDG uptake in certain areas of the body. The lower the number, the better.

PocketHealth can help you gain a better understanding of your report before your follow-up appointment. Report Reader provides simple definitions of specialized medical terms, while MyCare Navigator highlights any follow-up recommendations and provides customized questions to ask your doctor at your follow-up.

 

 

Are PET scan results read immediately?

When your scan results are read depends on the urgency and severity of your situation. In an emergency your results will be delivered immediately, while you’re still in the hospital. But for a regular booking, it usually takes several days for the PET imaging department or clinic to release your images and report to your doctor.

With PocketHealth you can have fast, secure access to your PET scan results before your follow-up appointment, often as soon as they’re released by the radiologist.

What does cancer look like in a PET scan image?

A PET scan captures images along three different planes and compiles them into colorful images. Bright spots on a PET scan image indicate high levels of metabolic activity (i.e. abnormal FDG uptake), which could be a sign of cancer.

However, not all cancers show up on a PET scan, which is why a PET scan is often reviewed along with other scans and lab results. Other tests are often needed to diagnose cancer, to assess whether an area that collected a lot of radioactive material is non-cancerous (benign) or cancerous (malignant).

 

PET scans: A proactive approach

PET scans illuminate the functioning of your organs and tissues to help doctors monitor disorders. A PET scan highlights what is metabolically active, which allows your healthcare team to track the progress of diseases.

PocketHealth gives you fast and secure access so you can view and share your PET scan images and report. The more information you have, the better prepared you are for the next steps in your healthcare journey.