Xray Film Holders

Question 1

Film holder

Answer 1

Functions to shield the film from white light until it can be processed

Question 2

Non-screen, direct exposure, or cardboard cassette film holder

Answer 2

Designed to be used with non-screen film delivers excellent detail of small parts such as extremities
Require very high radiation dose

Question 3

Screen cassette film holder

Answer 3

Most common type of holder, contains intensifying screens or scintillators
Creates 95%-98% of image

Question 4

Frame

Answer 4

Either metal, plastic, or carbon fiber

Question 5

Front

Answer 5

Must be radiolucent and homogenous

Question 6

Back

Answer 6

Most cassettes have a varying amount of lead to absorb backscatter that would fog the image

Question 7

Pressure pad

Answer 7

A felt of foam pad located between the back screen and the back of the cassette
Meant to maintain good film screen contact

Question 8

Film/screen contact

Answer 8

Close contact between the screen and the film must be maintained in order to guarantee image sharpness
If there is poor contact there will be localized blurring in the image

Question 9

Causes of poor film/screen contact

Answer 9

1.Bent or warped cassette
2. Warped screens
3. Foreign objects in the cassette
4. Worn out pressure pad

Question 10

Intensifying screens

Answer 10

They contain crystals that will emit light when exposed to x-rays.
They are called scintillators in DR

Question 11

Intensifying function

Answer 11

Reduce the exposure to the patient
Film only absorbs 1% of incident photons while screen absorbs 50x mores

Question 12

Base of screen

Answer 12

Made up of either cardboard or polyester plastic, about 1mm thick, and act as a support for the rest of the screen

Question 13

Reflective layer

Answer 13

this is a layer of titanium dioxide that is about 25 μm thick.
Reflects light back toward film emulsion, increasing speed of screen

Question 14

Phosphor or active layer

Answer 14

Layer of microscopic crystals that will emit light when exposed to X-rays
Thicker in back to maintain speed as the front

Question 15

Phosphors must have which characteristics?

Answer 15

1.High atomic number - required to absorb X-rays.Higher atomic number, the greater the absorption
2.Emit large amount of light- The ability of screens to convert X-rays to lights, called conversion efficiency
3. Spectral emission - Light must be of proper color
4. No afterglow or lag - Continued luminescence of the screen after the exposure to xrays has stopped

Question 16

Absorbtion efficiency

Answer 16

The ability to absorb X-rays

Question 17

Spectral matching

Answer 17

Correctly matching the color sensitivity of the film to the color emission of the intensifying screen

Question 18

Protective layer

Answer 18

Layer of protective material to keep active layer from being damaged during the handling and cleaning

Question 19

Luminescence

Answer 19

The emission of light by a crystal following exposure to an outside stimulus, such as exposure to xrays or electrons
Occurs because xrays excite electrons, and when electrons return, they emit visible light

Question 20

Luminescence can occur by what 2 processes?

Answer 20

1. Fluorescence - Light is emitted within 10^-8 seconds after being exposed to outside stimulus, immediate exposure
2. Phosphorescence - Light is emitted sometime after 10^-8 after exposure to an outside stimulus, there is lag time, visually see it

Question 21

When does the greatest absorption of xrays occur?

Answer 21

when the x-ray photon energy and the binding energy of the K-shell electron are almost the same.
• This is called the K-edge effect

Question 22

Screen speed

Answer 22

Amount of light that is emitted for a given amount of x-ray exposure

Question 23

Intensification factor

Answer 23

Numerical value calculated
I.F.=exposure without screens/exposure with screens
I.F. Values for X-ray screens tend to range between 30 and 60

Question 24

Relative speed

Answer 24

Numerical value that has also carried over into digital image receptors
New mAs=old relative speed x old mAs/new relative speed

Question 25

Specific name

Answer 25

Older method used for non-rare earth screens

Question 26

Intrinsic factors

Answer 26

Those inherent or built in to the screen by manufacturer

Question 27

Type of phosphor material

Answer 27

Different phosphor materials will emit different amounts of light for the same x-ray exposure due to differences in atomic number and K-edge values.

Question 28

Phosphor materials are categorized into what 2 categories?

Answer 28

1. Non-rare earth - older materials that emit blue-violet light when exposed to x-rays.
2. Rare earth - made up of materials from the rare earth or lanthanide series of elements from the periodic table.

Question 29

Main rare earth phosphors

Answer 29

1. Gadolinium oxysulfide - Emits in the green portion of color spectrum
2. Lanthanum oxybromide. Emits light in blue-violet spectrum
3. Yttrium oxysulfide - emits both blue-violet and green
4. Lutetium tantalite - emits light in the blue portion

Question 30

Thickness of phosphor layer

Answer 30

The thicker the layer of crystals, the faster the speed of the screen
Rare earth screens can be made thinner because material is faster
Results in poorer image resolution

Question 31

Size and shape of phosphor crystals

Answer 31

Larger crystals, faster speed of intensifying screen

Question 32

Packing density

Answer 32

Number of phosphor crystals per unit area
Faster speed screens will have more crystals per unit area
Decreases image resolution

Question 33

Dye in phosphor layer

Answer 33

Light absorbing dyes may be added to phosphor layer of slower speed screens to control reflected light
Increases resolution but decreases screen speed

Question 34

Extrinsic factors

Answer 34

Factors that are outside of the screen itself

Question 35

Ambient temperature

Answer 35

The greater the temperature of the screen, the slower it will behave in speed
Higher temp give crystals more energy which causes them to emit light

Question 36

KVp

Answer 36

Energy of the X-ray beam will determine how much light is emitted from the screen

Question 37

Spectral response

Answer 37

The sensitivity of the film to a specific color of light