Modalities

 

MRI & MRA | CT Scans | PET Fusion CT Scans | Mammograms | Ultrasound | X-Rays

 

Positron Emission Tomography (PET) Scan:

 

How does a PET scan work?

 

A PET scan integrates two technologies to view your body: Computed Tomography (CT) and a radioactive material (tracer). The tracer is what allows doctors to see how your body tissues absorb and use different chemicals in real time.

 

Before the PET scan, a tracer is injected into your blood stream (similar to a contrast agent in CT/MRI scans). The tracer is radio-labeled, meaning it emits gamma rays that can be detected by the PET scanner.

 

Once the tracer is absorbed in your body, a ring-shaped scanner is positioned over the body area. The computer collects the information emitted by the tracer and translates it into two-dimensional cross sections.

 

What does a PET scan show?

 

PET scanning allows doctors to measure a range of activity including blood flow, blood volume, oxygen usage, tissue PH (acidity), glucose (sugar) metabolism and drug activity. PET is very useful in watching the activity of cancerous tumors. Because malignant cells grow at such a fast rate, they metabolize more sugar than normal cells and can give your doctor a glimpse into how aggressive a tumor is or how its growth is slowed by treatment therapies.

 

Another common use for PET is for pre-surgical evaluation of medically uncontrolled seizures. By detecting metabolic changes in the brain, the surgeon can pinpoint the nonfunctioning area of the brain causing seizures.

 

How does the tracer work?

 

The radioisotopes used in PET to label tracers are 11C, 13N, 150 and 18F (carbon, nitrogen, oxygen and 18F used as a substitute for hydrogen). These radioactive forms of natural elements will pass safely through your body and be detected by the scanner. Various drugs and other chemicals can be labeled with these isotopes without changing their properties.

 

The type of tracer used depends on what your doctor wants to measure. For example, if your doctor is looking at a tumor, he might use radio-labeled glucose (FDG) and watch how it is metabolized by the tumor.

 

Who performs the test?

 

A specially trained nuclear medicine technologist will perform the test in the Nuclear Medicine department of our outpatient imaging center. The radiologist review the images and report the findings.

 

How should I prepare for the test?

 

Do not eat or drink any substance other than water 12 hours before scan.

 

Wear comfortable, pin-less clothing.

 

Avoid carbohydrates, caffeine’s and strenuous activity the day before scanning.

 

Be prepared to stay for 2 hours.

 

What happens during the test?

 

First you will receive an injection of a small amount of radioactive tracer. You will be asked to rest for about 30-45 minutes until the tracer reaches your brain (2 hours to be absorbed by bone). Next, you will lie comfortably on a table that moves slowly through the PET scanner. Be sure to remain as still as possible so that the machine can get accurate pictures. Depending on the information your doctor needs, you may be asked to perform certain tasks like read or speak to activate specific areas of your brain.

 

Once the scan is complete, you can leave. Be sure to drink plenty of fluids to flush out any tracer left in your body.

 

What are the risks?

 

The radio-labeled tracer is radioactive, which means your body is exposed to about the same amount of radiation as in two chest x-rays. The radioactive chemicals have very short half-lives and they won’t remain in your system long. There is no need to avoid interacting with people. Women who are pregnant or nursing should not undergo a PET scan.

 

How do I get results?

 

The radiologist will promptly review your images and communicate directly with your referring doctor, who in turn will discuss the results with you. The estimated turn-around time for reports to be distributed to your physician, is 24 hours. This is typical timing unless your doctor has requested a Stat exam, in which the Radiologist will rush your dictation to the treating physician.

 

Since PET measures the chemical activity of tissues, some diseases such as diabetes or other metabolic disorders may give false results.