A nuclear scan photographs function, not anatomy

A nuclear scan uses a small amount of radioactive material — a radiotracer
— and a special camera that detects the radiation coming from inside the body.

What sets it apart from every other scan is in one sentence: **it shows how
organs and tissues are working, not just what they look like.** The tracer
travels to the part of the body being examined, and **how much of it is
absorbed indicates how well that organ or tissue is functioning**. Structure
is what other imaging is for; function is what this measures.

What it is used for

• Checking how organs such as the heart, lungs or kidneys are working
• **Finding disease early — sometimes before changes appear on other imaging
  tests**, which follows directly from measuring function rather than shape
• Bone scans
• Evaluating the thyroid
• Checking how well cancer treatment is working

Getting the tracer in

The radiotracer is given as an injection, a pill or liquid to swallow,
or a gas to inhale, depending on the test.

**Always tell your provider if you are pregnant, think you may be, or are
breastfeeding.**

What happens on the day

You may be asked to change clothes and remove jewellery or anything else that
would interfere. Ask in advance whether there are special instructions.

Depending on the scan you may lie on a table, sit in a chair, stand, or —
for some heart scans — walk on a treadmill or ride a stationary bike. Stay
as still as possible unless movement is part of the test.

The images are made by a gamma camera, a SPECT (single-photon emission
computed tomography) scanner, or a PET (positron emission tomography)
scanner.

The long ones are long because the tracer needs time to distribute — the
waiting is part of the measurement.

Afterwards

Most people return to normal activities right away. Drinking fluids helps
the body clear the radiotracer. A radiologist reviews the images and
shares the results with your provider.

Source: MedlinePlus, U.S. National Library of Medicine.