Question

(a) What is the advantage and disadvantage images from radioactivity compared imaging from ultrasound, x-ray and CT?

(b)Explain in detail the operation of a PET scanner, illustrating your points by using more than one drawing, appropriately labeled.

Answer 1

b) Positron Emission Tomography, also known as a PET scan, uses radiation to show activity within the body on a cellular level.

It is most commonly used in cancer treatment, neurology, and cardiology.

Combined with a CT or MRI scan, a PET scan can produce multidimensional, color images of the inside workings of the human body.

It shows not only what an organ looks like, but how it is functioning.

A PET scan is used to diagnose certain health conditions, to plan treatment, to find out how an existing condition is developing, and to see how effective a treatment is.

Fast facts on PET scans

Here are some key points about PET scans. More detail is in the main article.

• PET scans are often used to diagnose a condition or to track how it is developing.
• Used alongside a CT or MRI scan, it can show how a part of the body is working.
• PET scans are often used to investigate epilepsy, Alzheimer's disease, cancer, and heart disease
• A scan is not painful, but patients should not consume any food for at least 4 to 6 hours before a scan. They should drink plenty of water.

How it works

PET scans demonstrate the physical state and function of organs.

In a PET scan, a machine detects radiation that is emitted by a radiotracer.

A radiotracer consists of radioactive materialthat is tagged to a natural chemical, such as glucose.

This radiotracer is injected into the body, where it travels to cells that use glucose for energy.

The more energy a group of cells needs, the more the radiotracer will build up in that location. This will show up on images that are reconstructed by a computer.

The cells, or activity, will show up as "hot spots" or "cold spots."

Active areas are bright on a PET scan. They are known as "hot spots."

Where cells need less energy, the areas will be less bright. These are "cold spots."

Compared with normal cells, cancer cells are very active in using glucose, so a radiotracer made with glucose will light up areas of cancer.

A radiologist will examine the image produced on the computer, and report the findings to a doctor.

An example of a glucose-based radiotracer is fluorodeoxyglucose (FDG). In FDG, radioactive fluoride molecules are tagged to glucose to make a radiotracer. FDG is the radiotracer most commonly used today.

Instead of glucose, oxygen can be used.