What are the factors affecting the speed of intensifying screens?

What are the factors affecting the speed of intensifying screens?

The speed of intensifying screens is found to increase with shortened development time; to increase with increase of tube potential; to be independent of the tube current from 2 to 35 ma; to be independent of the target film distance from 9.5 to 2.5 meters; to increase as more filtering medium is interposed between the …

How do intensifying screen affect density?

Intensifying screens are used in the x-ray cassette to intensify the effect of the x-ray photon by producing a larger number of light photons. It decreases the mAs required to produce a particular density and hence decreases the patient dose significantly.

How does kVp affect density?

Increasing kVp also contributes to the overall density (darkness) of the image. A fairly small adjustment in kVp can have a significant effect on the image. Just a 15% increase in kVp is roughly equivalent to doubling the mAs. Conversely, a 15% decrease in kVp is roughly equivalent to cutting the mAs in half.

What is the speed of intensifying screen?

Detail (fine): A very slow system seldom used in modern radiography, used by Podiatrists in some instances. It has a relative speed of 50 when used with Hi Speed Blue Film.

How does intensifying screen affect contrast?

Intensifying screens are used to shorten exposure times and, some- times, to increase the photographic contrast. Considering that roentgen radiation was discovered through its fluorescent action (on barium plati- nocyanide), it is not strange that roentgen diagnostics very soon found a use for intensifying screens.

How does film processing affect density?

The darkness or density of the film increases as the exposure is increased. This general relationship is shown in the second following figure. The specific relationship between the shades of gray or density and exposure depends on the characteristics of the film emulsion and the processing conditions.

Why is it desirable to use fast speed film instead of slow speed?

-The faster the film speed, the less radiation is required to produce desirable density. A. Size of silver halide crystals: Larger the crystals, the faster the film speed, less radiation is necessary to produce an acceptable image.

What affects film density and contrast?

The sharper the angulation of the curve, the less the latitude of the film and the greater the contrast. The flatter the angulation, the greater / wider the latitude of the film and the less the contrast. Above a density of 3.00 the curve flattens out as this is the maximum density that can be perceived.

What is an intensifying screen made of?

An intensifying screen is a plastic sheet coated with fluorescent material called phosphors. Phosphors are materials which convert photon energy to light. LUMINESCENCE is the emission of light from a substance bombarded by radiation.

What affects radiographic density?

When the mA or exposure time increases, the number of x-ray photons generated at the anode increases linearly without increasing beam energy. This will result in a higher number of photons reaching the receptor and this leads to an overall increase in the density of the radiographic image (Figure 2).

What is the relationship to density of relative speed for film screen combinations?

What is the relationship to density/IR exposure of relative speed for film/screen combinations? As relative speed increases, the amount of exposure required to maintain the same density/IR exposure decreases.

What does intensifying screen speed mean?

Definition of Intensifying Screen Speeds. Blue Emitting Calcium Tungstate. Detail (fine): A very slow system seldom used in modern radiography, used by Podiatrists in some instances. It has a relative speed of 50 when used with Hi Speed Blue Film.

What is the speed of an intensifying screen-film receptor?

The actual speed varies, especially with the x-ray spectrum (KV) and film processing conditions. The sensitivity (speed) of an intensifying screen-film receptor depends on the type of screen and film used in addition to the conditions under which they are used and the film is processed.

What is the relative speed of green sensitive film?

Regular: Has a relative speed of 400 when used with regular green sensitive film. Far and away the most commonly employed film screen system today. Fast: The highest speed green rare earth screen. With regular green sensitive film you would have a 600 speed and with high speed green film you could get a speed of 1200.

What is the advantage of intensifying screens in cassettes?

The use of intensifying screens in cassettes keeps the exposure time as short as possible, but the images are less sharp than those obtained with direct analog film. The cassette should be checked regularly for light-tightness to ensure that no light can cause fogging of the film.