Physics Chapter 14 Flashcards Preview

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Flashcards in Physics Chapter 14 Deck (46)
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Know the two ways that image intensifiers improved the image process

*Brightened the image significantly (eliminated the need to dark adapt)
*Allowed for a means of immediately viewing the fluoro image (reduced radiographic dose)


Know what the conventional fluoroscopic chain consists of

x-ray tube, an image intensifier, a recording system, and viewing system


Know the 5 basic parts that make up an image intensifier

Input phosphor, photo cathode, electrostatic focusing lenses, accelerating anode, and output phosphor


Know why the input phosphor is made of cesium iodide

It absorbs remnant x-ray photon energy and emits light in response


Know the size correlation between the input and output phosphor

output phosphor is much smaller


Know how brightness gain has traditionally been found

Multiplying the flux gain by the minification gain


Know the size of the image intensifier tube

50 cm in length and 15-58 cm diameter


Know how flux gain is expressed

The ratio of the number of light photons at the output phosphor to the number of light photons emitted in the input phosphor


WHat results from the higher the conversion factor or brightness gain factor

image appears brighter because the same number of electrons is being concentrated on a smaller surface area


Know what happens as the image intensifier tube ages

The ability of the image intensifier to increase brightness deteriorates with the age of the tube


Know what happens in regards to radiation as the image intensifier tube ages

More and more radiation is necessary to produce the same level of output brightness, translating to an increased patient dose


Know how ABC commonly operates

By monitoring the current through the image intensifier or the output phosphor intensity and adjusting the exposure factor if the monitored value falls below preset levels


Know how to find the degree of magnification

Dividing the full size input diameter by the selected input diameter


Know what magnification improves

The fluoroscopist's ability to see small structures (spatial resolution) but at the expense of increasing patient dose


Know how spatial resolution is measured

Line pairs per millimeter


Know what distortion is a result of in fluoro

Inaccurate control or focusing of the electrons released at the periphery of the photocathode and the curved shape of the photocathode


Define a pincushion appearance

The combined result is an unequal magnification (distortion) of the image


Know how a "noisy" or "grainy" image occurs

If too few x-rays exit the patient and expose the input phosphor, then not enough light is produced, which decreases the number of electrons released by the photocathode to interact with the output phosphor


Know how to fix a "noisy" image

increasing the mA


Know what the 2 devices are that convert the image from the output phosphor to an electrical image

The camera tube and charge-coupled device (CCD)


Know what the camera tube most often used is

vidicon tube


Know what the deflection coils act to accelerate

the electron beam


Know what the CCD is made from

A series of metal oxide semiconductor capacitors


Know what is sent from the capacitors

Charge is sent as an electronic signal to the tv monitor


Know what the purpose of the television monitor is

Convert the electrical signal from the camera tube to CCD back into visible light


Know what typical television monitors are called

525 line systems


Know the resolution of HIGH resolution monitors

1024 lines per frame


Know what the image intensifier is capable of resolving

Approximately 5 lp/mm whereas the monitor can display only 1-2 lp/mm


Know the 3 types of recording systems

Cassette sport film, film cameras, video recorders


Know what happens when the spot film exposure button is pressed

The cassette is moved into position between the patient and image intensifier and the machine shifts from fluoroscopic to radiographic mode and exposes the film