Intensifying Screens

What is the main advantage of an IS, how is patient exposure affected?

It significantly decreases a patients dose therefore reducing patient exposure

Function of intensifying screens

Converts xray energy into visible light

What is the purpose of a reflective layer?

To intercept wayward light photons and redirect them back to the film. This processes doubles the number of light photons being emmitted.

What happens to film resolution as screen decreases?

As screen speed decreases, the film resolution increases.

Briefly explain spectral matching

The film sensitivity must be responsive to the color emitted by the screen

What does light do for an X-ray image?

It exposes film

What happens to speed when a reflective layer is added?

Speed increases

What is the conversion efficiency from xray to light photons for calcium tungstate?

5%

What happens to screen speed as room temp decreases

Temp decreases, speed increases

What unit is used to measure resolution detail?

Line pairs per millimeters LP/MM

40 mAs @ 10 kV using detailed screen (original) is used for lateral view of a thumb. What technique should apply if rare earth view is used?

The rare earth screen is 8 times faster (400/50=8). Therefore, you would need to decrease your mAs by a factor of 8. New technique 10 kV @ 5 mAs

The detail screen is 4 times slower than the high-speed screen (200 ÷ 50 = 4).
New technique: 70 kV @ 88 mAs (22 mAs × 4 = 88 mAs

A high screen (original) technique for a knee series requires 22 mAs @70kV, if an extremity screen(new) is used in place what exposure factors will be used.