Rad: Image Receptors

**Explain the difference between screen film and non-screen film:

• Screen film is more sensitive to and exposed by light from an IS.

• Non-screen film is sensitive to light solely from x-rays.

When would you use a screen-film?

Ab/Thor/pelvis/ortho— general day-today rads.

When would you use a non-screen?

Dentistry, thin tissues— requires more exposure.

How does the speed of the screen relate to the size of phosphor crystals?

• Larger crystals= faster the speed

• Smaller crystals= slower speed, but more detail.

Rare Earth Phosphor crystals emit light in the ___________ spectrum.

Green light.

Calcium Tungstate crystals emit light in the ____________ spectrum.

Blue light.

Which type of phosphor crystals have a greater light/conversion efficiency?

Rare Earth.

How do you clean your intensifying screen? What should you use?

IS with antistatic cleaner and kim wipes

• do NOT apply pressure while cleaning

What is a latent image?

An invisible image on the film that becomes visible once processed.

Cassettes need to be ____________ to x-rays.

Radiolucent to x-rays.

Cassettes need to be ______________ to light.

Radiopaque to light.

How should you store unexposed film?

Upright in low humidity, not around chemicals, and in the dark.

What type of crystals are found in in film?

Silver halide crystals.

What type of crystals are found in the cassette?

Rare Earth crystals (IS).

What percentage of exposure results from x-rays (with an IS)?

5%.

What is a split film mostly used for?

Extremity views.

What do intensifying screens allow?

A lower mAs to be used.

Screen film is used for dental imaging.

True or false?

False— used in abdominal/thoracic film— extremities.

What is the main advantage of today’s rare-earth coated screens?

They have a higher x-ray to light conversion.

Will non-screen film require greater or less exposure?

Greater.

With IS, what percentage of exposure is from the light from the intensifying screen, and what percentage of the exposure is from actual x-radiation?

• 95% from the IS

• 5% from actual radiation

The film and screen combination has to coincide/match.

True or false?

True.

What do IS mainly do?

Helps us lower the amount of radiation we use— lowers mAs.

What are the must-haves for IS?

• High level of x-ray absorption

• Must have high x-ray to light conversion

• Must have little to no afterglow.

What are the must-haves for cassettes?

• Must have lead backing to prevent scatter.

• Must be sturdy to last for future use.

• Front needs to be radiolucent to x-rays, and radiopaque to light.

What are the 4 layers of the IS?

• Base

• Reflective

• Phosphor crystals layer

• Protective coat

What are the 3 layers of film?

• Emulsion

• Base

• Supercoat

Are areas that are not exposed going to turn lighter or darker?

(Think the spray-paint analogy)

Lighter.

Are areas that are exposed going to turn light or darker?

(Think the spray-paint analogy)

Darker.

The thicker the phosphate layer =

Increase in absorption and light emission.

What is being described?

• Majority of exposure is from light (95%)

• Extremities, Abdo, Thor— thicker

• Purpose= decrease amount of radiation (lowers mAs)

  • Decreases our exposue + patient’s.

Screen films.

What is being described?

• 100% exposure from x-rays

• Used on thinner tissues

  • exotics or dentistry

Non-screen film.