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Intensifying Screen
Principles of Radiographic Imaging 5th Edition Chapter 22
| Question | Answer |
|---|---|
| Delayed phosphorescent emission, also called screen lag | Afterglow |
| The base material tha tthe film is made from; it is usually polyester, tough, stable, rigid, and uniformly lucent; it usually contains blue tent | Base |
| The ability of the phosphor to emit as much light per x-ray photon interaction as possible, which is related to the screen speed | Conversion Efficiency |
| The ability of a material to emit light instantaneously in responses to excitiation within 1 nanosecond | Flourescence |
| Device used to amplify the incoming x-ray beam and reduce patient dose | Intensifying Screen |
| When the incident x-ray photons match the K-shell binding energy of the phosphor, there is an increase in the characteristic production within the screen | K-Shell Absorption Edge |
| Measurment of recorded detail, sharpness, and resolution; the minimum size and space between objects that can be visualized on the final image | Line Pairs per Millimeter(lp/mm) |
| Measures the ability of a film/screen system to accurately measure the boundaries of an image | Line Spread Function(LSF) |
| The ability of a material to emit light in response to excitation | Luminescence |
| Measurement of recorded detail, sharpness, and resolution; measures the resolving ability of a film/screen combination | Modulation Transfer Function(MTF) |
| The ability of a material to delay emission of light in repsonse to excitation | Phosphorescence |
| A layer of material used in an intensifying screen that is capable of absorbing the energy of an incident x-ray photon and then emitting light photons | Phosphor Layer |
| A layer of material used in an intensifying screen applied to the top of the phosphor layer to protect it from abrasions and stains; usually think plastic | Protective Coat |
| A layer of material used in an intensifying screen to reflect light toward the film | Reflective Layer |
| The most useful rating of intensifying screens; expressed with par-screens and film being arbitrarily assigned a relative speed number of 100 as a control point | Relative Speed |
| Delayed phosphorescent emission; also called afterglow | Screen Lag |
| An indication fo teh precise wavelength of light emitted by the phsphor | Spectral Emission |
| How do intensifying screens reduce patient dose? | Produce large quantities of light photons when struck by x-rays. Thereby amplifyingthe incoming x-ray beam and reducing patient dose. |
| What are the four basic components of an intensifying screen? | Base, reflective layer, phosphor layer, and protective coat. |
| What characteristics should an intensifying screen phosphor possess? | Resolution, speed, contrast and latitude. |
| What is the difference between fluorrescence and phosphorescence? | Fluorescence is instantaneous emission whereas phosphorescence is a delayed emission. |
| What is the relationship between resolution and phosphor crystal size, layer thickness, and phosphor concentration? | Phosphor cyrstal size and layer thickness are both inversely related to resolution and directly related to screen speed. |
| What is quantum mottle? | Caused by an insufficient quantity of photons striking the intensifying screen |
| What is the purpose of a cassette? | To create a portable, lightproof case for film to utilize the intensifying screens to best advantage and to attenuate the residual x-ray beam as much as possible. |
| What is the formula used to calculate a relative speed conversion from one film/screen combination to another? | mAs1/mAs2=RS2/RS1 |
| What are the three methods of measuring resolution? | Line Pairs per Millimeter(lp/mm), Line Speed Function(LSF), and Modulation Transfer Function(MTF) |
| How is film/screen contrast related to latitude? | The film/screen latitude is primarily dependent upon the latitude of the film, whichis directly realed to the contrast. |