MRIs and PET scans are imaging tests that doctors use to assess cancer, heart disease and brain conditions. Both of these scans produce detailed 3D images.
Both types of tests provide a lot of useful information about your health. However, they differ in how they work and what they can see.
MRIs vs. PET Scans
MRIs and PET Scans are both used to get detailed pictures of the organs and tissues inside your body. They’re also useful for diagnosing many different diseases, including heart disease and cancer.
An MRI uses a magnetic field and radio waves to produce images of your body’s interior structures. It can show how well your joints, spine and organs are functioning, as well as other problems such as clots or tumors. It is safe for most people, but may be uncomfortable for some, so it’s best to tell your doctor if you have metal implants, tattoos or are claustrophobic.
PET scans are a newer form of imaging that’s also used to diagnose certain diseases. They use a special dye with radioactive tracers to help the machine capture changes in chemical activity within your body. This helps your doctor identify diseases and abnormalities that may not show up on MRIs, such as heart or brain disorders.
The tracer is injected into a vein in your hand or arm. As it travels through your bloodstream, the tracer collects in areas where there is higher levels of biochemical or metabolic activity, which will then appear brighter on the PET scan.
This type of scanning can be especially helpful in detecting cancer before it forms, which is why doctors use it so often for screening purposes. In fact, it has an accuracy of 90% for breast cancer recurrence, which is far better than most other screening tests (X-rays, CT scans and mammography) combined.
A PET scan can also be used to see blood flow and metabolism, which are often the first signs of diseases. For example, if you have coronary artery disease, the tracer will collect in areas where your blood is flowing better than it does elsewhere. It’s important to let your doctor know if you have any other medical conditions that affect the way your body functions, such as diabetes or kidney problems.
Before having a PET scan, you’ll need to change into a hospital gown and remove all metal objects from your body, such as jewelry, belts and wire bras. You should not eat anything for six hours before the scan and avoid taking any drugs or supplements that might interact with the tracer. You should also notify your doctor if you are pregnant or breastfeeding so that they can make adjustments to the test.
What is an MRI?
MRI is a safe and painless procedure that makes detailed pictures of areas inside the body. It can help diagnose and plan treatment for a wide range of health conditions, including brain and spinal cord diseases, cancer, heart disease, and other conditions. It’s also used to find out how well a treatment is working.
An MRI works by using magnetic fields to show what’s going on inside your body. The magnetic field is created by passing electricity through wire coils, which cause the coils to vibrate. A computer processes the signals to create a series of images that a radiologist can study from different angles.
Your doctor may recommend an MRI if you have a condition or injury that affects your bones, muscles, joints, soft tissues, and organs. It is also very useful in imaging the heart and blood vessels, and finding out how a specific treatment is working.
Before you go to the MRI scanner, a doctor will talk to you about what to expect. If you have claustrophobia (a fear of enclosed spaces), your doctor might give you medication to make you less anxious. You’ll be placed on a movable table that slides into the opening of a tube-shaped cylinder that contains a magnet.
A radiologist then monitors you from another room. You’ll have a buzzer to hold if you need to alert the radiologist to any concerns. You will also be given earplugs or headphones to protect your ears as the machine makes noise.
When you’re in the MRI, you will be asked to remove any metal objects, such as keys and jewellery. This is important because the strong, static magnetic field will attract metal.
If you have a metal implant, such as a heart pacemaker, the device could be affected by the magnetic field. It’s best to tell your doctor about any implants or metal devices before you go to the MRI.
The radiologist may inject contrast dye into your vein before the scan, to help certain tissues and blood vessels show up more clearly. This dye is called gadolinium and can leave a metallic taste in your mouth.
What is a PET Scan?
PET, or positron emission tomography, is a type of radiology imaging test that helps your doctor see what’s happening in your body. It can be used to find cancer, heart disease, and brain disorders.
PET scans use a small amount of a radioactive substance (radiotracer) to make pictures of how your cells are working. This can help your doctor spot diseases early, before they’re visible on an MRI or CT scan.
The tracer is injected into a vein in your arm or hand. Then, you’ll wait quietly for about an hour to give the tracer time to get absorbed by your organs and tissues.
You’ll then be positioned in a room with a large machine that looks like a CT or MRI scanner. Your radiographer will help you lie down on the machine couch, and then they’ll take the pictures. They’ll use the gamma rays that are released by the tracer to create images of your body, which are then interpreted by a doctor specially trained in scan images (radiologist).
When you arrive at the hospital or radiology centre, you’ll be asked to change into a gown and remove all metal and jewellery items. Staff will then insert an intravenous line into a vein on the back of your hand or arm.
Your blood sugar levels will also be checked and for some scans, you’ll be given a drink of a special dye called contrast material to make the images more clear. The tracer can be harmful to people who have kidney disease or high creatinine levels from certain medications they’re taking.
After the PET scan, you’ll need to drink plenty of water to flush the tracer from your body. Your doctor will tell you how to do this, and will check your urine after the test to see if you’re safe to go home.
Generally, PET scans are very safe and rarely cause problems. The tracer doesn’t stay in your body long, and the radiation is very low. You’ll be able to get back to your normal daily activities as soon as the tracer is out of your system.
What is a PET/CT Scan?
A PET/CT scan, also called a positron emission tomography scan, is a type of test used to detect cancer and other diseases. It helps doctors understand how a disease is growing or spreading, and what treatments will work best. It can also be used to plan surgery for brain tumors or heart conditions like coronary artery disease (coronary artery bypass grafts).
A PET scan uses a special radioactive substance, called a tracer, to show which parts of your body are using energy differently than other parts. These areas usually pick up more of the radioactive sugar than healthy cells.
Then, a doctor will inject the tracer into a vein, usually in your arm. As the tracer moves through your bloodstream, it will collect in tumors or other inflamed areas and cancer cells for doctors to see on a CT scan.
When the tracer reaches your brain, it is detected by a ring of detectors in a machine that looks like a large donut. The detectors pick up the radiation given off by the tracer and create 3-D images of the area being scanned. The information from the PET scan is interpreted by a radiologist.
Some medical centers also combine PET scans with CT scans to provide a more comprehensive picture of the inside of your body. Typically, these tests are done at the same time in order to get more accurate results.
During the PET scan, you will lie on an exam table and move slowly through a scanner. You may be able to feel the radioactive tracer in your arms and legs as it moves through your body.
You will need to be very still during the procedure, so your doctor may have you wear a mask or cast to keep you comfortable. It’s important to let the technologist know if you have any health conditions, such as claustrophobia, that can make you uncomfortable during a PET scan.
The doctor will give you special instructions based on the type of test you have, and the specific part of your body that needs to be scanned. For example, if you have a heart condition, you will need to avoid caffeine for 24 hours before the test.