Other imaging modalities (second half)

Does ultrasound use ionizing radiation?

No. Ultrasound does not use ionizing radiation.

What does an ultrasound transducer do?

It sends sound waves into the patient and receives reflected echoes.

What produces sound waves in an ultrasound transducer?

Piezoelectric ceramic crystals.

Why is conducting gel used during ultrasound?

Sound travels slowly through air and is scattered, so gel improves the image.

What is echogenicity?

The intensity of reflected echoes from a tissue.

What does anechoic mean on ultrasound?

Few or no echoes; appears black, like fluid.

What does hypoechoic mean?

Some echoes; appears grayish and darker than surrounding tissue.

What does hyperechoic mean?

Many echoes; appears bright and white, like bone.

What does isoechoic mean?

Two areas receive the same number of echoes and appear equally bright or dark.

Why does air scatter ultrasound sound waves?

There is virtually no medium to carry the waves.

What happens to ultrasound sound waves through bone?

Sound cannot pass through bone.

What is acoustic shadowing?

An artifact where sound cannot penetrate tissue, so the area beyond appears black.

What is acoustic enhancement?

Increased sound intensity beyond fluid or an anechoic area due to lack of attenuation.

What is attenuation?

Reduction in echo intensity as sound waves pass through tissue.

What does a higher-frequency transducer provide?

Greater image detail.

What does a lower-frequency transducer provide?

Deeper penetration into tissues.

What does B-mode stand for?

Brightness scan; most commonly used for routine scanning.

What does M-mode stand for?

Motion scan; used only for echocardiography.

What is an echocardiogram?

An ultrasound scan of the heart.

What is the purpose of contrast studies?

To improve visualization of structures that are difficult to see otherwise.

What do negative contrast studies use as contrast media?

Gases such as air, carbon dioxide, and oxygen.

How do gases appear on radiographs?

Black.

Why are gases useful as negative contrast?

They emphasize contrast between soft tissues with similar radiographic density.

What do positive contrast studies use as contrast media?

Liquids such as barium sulfate and iodinated compounds.

How do positive contrast media appear on radiographs?

White.

What are common positive contrast media?

Barium sulfate and iodinated compounds.

What is barium sulfate commonly used for?

The gastrointestinal (GI) tract.

When should barium sulfate NOT be used?

When GI perforation or aspiration is suspected.

What may an animal's feces look like after barium?

White.

What side effect may occur after barium administration?

Constipation.

What are iodinated compounds?

Water-soluble, clear positive contrast liquids.

When are iodinated compounds used in the GI tract?

When GI perforation is suspected.

Why can iodinated compounds be given intravascularly?

They have low viscosity.

What are possible adverse reactions to iodinated compounds?

Vomiting, irritation, and anaphylaxis.

What are the two types of iodinated compounds?

Ionic and nonionic.

Which iodinated compounds are safer?

Nonionic compounds.

What is fluoroscopy?

Imaging that provides real-time moving images.

What equipment does fluoroscopy use?

An X-ray tube plus an image intensifier and TV screen.

What is an advantage of fluoroscopy?

It provides real-time moving images that can be recorded.

What is another advantage of fluoroscopy?

Very short exposure times and reduced dose.

What is a limitation of fluoroscopy?

A TV screen is required to view the image.

What is another limitation of fluoroscopy?

The image is only as good as the TV screen.

What is important for fluoroscopy positioning?

Proper positioning is important.

What type of study can fluoroscopy show in real time?

A barium swallow.

How does the fluoroscopy screen display differ from a radiograph?

On the screen, bone is black and lungs are white.

How does the final fluoroscopy image appear?

Like a normal radiograph: bone white and lungs black.