What Is a PET/CT Scan – and Why Do I Need One?

Your provider has told you that you need a PET/CT scan. They explain that PET stands for ​“positron emis­sion tomog­ra­phy,” that CT stands for ​“com­put­ed tomog­ra­phy,” and that these are com­mon types of imag­ing tests that allow your provider to see what’s hap­pen­ing in your body.

After a quick joke con­firm­ing that a PET scan is a scan of your body and not Rufus’s, your mind starts rac­ing with ques­tions. What exact­ly is a PET/CT scan? What does it show?

Here are answers to com­mon ques­tions about PET/CT scans.

What Are PET Scans and CT Scans?

A PET scan is a form nuclear imag­ing. It uses a small amount of a radioac­tive sub­stance called a trac­er (also called radio­trac­ers or radio­phar­ma­ceu­ti­cals), a com­put­er, and a spe­cial cam­era to take images of your organs and tis­sues. A CT scan uses X‑rays and a com­put­er to cre­ate detailed 3D images of your body.

Both tests are pain­less and are typ­i­cal­ly out­pa­tient pro­ce­dures, mean­ing you can go home the same day.

Is a PET Scan a Type of CT?

You will often see ​“PET/CT,” but PET and CT scans are actu­al­ly two dif­fer­ent tests.

PET scans look at how your organs func­tion while CT scans exam­ine the struc­ture of your organs. 
It’s com­mon for both tests to be tak­en at the same time. The PET/CT com­bo puts the images from each test togeth­er into a more detailed image. This gives a clear, in-depth look into what’s hap­pen­ing with your organs and allows your provider to make a more accu­rate diagnosis.

Also read: Radi­ol­o­gy – Types of Imag­ing Explained

Why Would I Need PET/CT Scans, and What Do They Show?

PET/CT scans are often used for peo­ple with can­cer. If you have a lump or abnor­mal find­ing on a dif­fer­ent test, you might get a PET/CT scan to see if it’s can­cer­ous. If you already know you have can­cer, your provider may order a PET scan to see if it has spread, find the extent to which it has spread, deter­mine the best treat­ment approach, or eval­u­ate how you’re respond­ing to treat­ment. After treat­ment, a PET/CT scan can show how well it worked or assess the out­look of your cancer.

Also read: Can­cer Pre­ven­tion at Duly Health and Care

PET/CT scans aren’t just for can­cer. They also offer clues about what’s hap­pen­ing in the dif­fer­ent parts of your body. For exam­ple, PET/CT scans are a very use­ful form of car­diac imag­ing if you have had a heart attack or your provider sus­pects heart dis­ease. They are also good for brain imag­ing if you’ve had seizures or symp­toms of a brain disorder.

Also read: Inno­va­tion in Car­diac Imaging

How Long Is a PET/CT Scan?

The test itself only takes about 30 min­utes, but the whole process can take clos­er to two hours. It may take up to an hour for your body to ful­ly absorb the trac­er for the PET scan, and you may also need to wait a lit­tle bit after the test to make sure the images are clear. 

What Should I Expect?

You will get inject­ed with a trac­er via an IV, which might make you feel a brief cold sen­sa­tion going up your arm.

Next, you will rest for 30 min­utes to an hour as your body absorbs the trac­er. While you don’t need to keep com­plete­ly still, you will need to avoid move­ment and talk­ing as much as you can. Mov­ing too much can make the trac­er go to the wrong part of your body.

Dur­ing the scan, you will lie down on a nar­row, padded table that slides into a large tun­nel-shaped scan­ner. It’s crit­i­cal to remain still dur­ing the scan since move­ment can make the images blur­ry. You might hear some click­ing or buzzing sounds, but you won’t feel anything.

Will I Be Enclosed in a Small Space?

Yes, the scan­ner is enclosed. It’s nor­mal to feel some anx­i­ety about this, espe­cial­ly if you’re afraid of small, enclosed spaces. But you can rest assured that you’re safe – some­one will be mon­i­tor­ing you at all times.
If you’re ner­vous, let your physi­cian know before the scan. They may be able to give you some med­i­cine to help you relax.

Are PET/CT Scans Safe?

Try not to let the word ​“radi­a­tion” scare you. PET trac­ers have a very small amount of radi­a­tion. CTs do have a lit­tle more radi­a­tion, but the risk of get­ting can­cer from a sin­gle CT is still low and the ben­e­fits usu­al­ly far out­weigh the risks.

Also, it’s rare for there to be side effects after a scan. While it’s pos­si­ble to have an aller­gic reac­tion to the trac­er, it is extreme­ly unlike­ly. Even if you do have a reac­tion, it will prob­a­bly be mild (such as nau­sea or dizziness).

That said, PET/CT scans aren’t for every­one. You should not get one if you are preg­nant or breast­feed­ing. Your provider might also have you take some extra pre­cau­tions ahead of time if you have dia­betes or have had an aller­gic reac­tion to a trac­er or con­trast dye in the past.

How Do I Pre­pare for a PET/CT Scan?

There isn’t a lot of prep work for a PET/CT scan. A nuclear med­i­cine tech­nol­o­gist will call you with instruc­tions before your scan, but some gen­er­al rules of thumb include avoid­ing stren­u­ous exer­cise for a few days before­hand and not eat­ing for 4 to 6 hours before the scan. If you’re get­ting test­ed for a heart prob­lem, avoid caf­feine for 24 hours beforehand.

Whether it’s your first scan or you’ve had sev­er­al, it’s nat­ur­al to feel on edge before any test. Remem­ber that scans are safe and that your provider is there for you if you’re ner­vous or have questions.

Ques­tions about PET/CT scans or oth­er imag­ing tests? For ques­tions relat­ing to radi­ol­o­gy, call 630−545−7880 or talk to your provider who ordered the test.