radiographic screens and digital imaging Flashcards

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1
Q

What is a cassette

A

the device that provides a light tight film holder and rigid support for film, as well as an intensifying screen

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2
Q

The cassette contains two intensifying screen, one on each side of the inside of the cassette. What is their purpose?

A

this doubles the film exposure obtained with a given x-ray exposure, thus reducing the amount of exposure to the patient

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3
Q

What type of film is used inside an X-ray cassette?

A

dual emulsion

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4
Q

What is the function of the padding in the pack of a cassette?

A

it ensures that there is a light positive pressure exerted on the film when the cassette is closed so that there is optimal film/screen contact at all points on the film

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5
Q

How do intensifying screens double the film exposure obtained with a given x-ray?

A

They are coated with phosphors, which are fluorescent crystals that give off light when exposed to x-rays
this is the property of luminescence that creates 99% of the x-ray image

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6
Q

The process of glowing only while being excited (such as during ionizing radiation) that will cease glowing at completion of exposure

A

fluorescence

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7
Q

luminescence that demonstrates afterglow (continues to flow for a period of time after the exposure to radiation has ceased)

A

phosphorescence

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8
Q

the emission of light from a substance bombarded by radiation

A

luminescence

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9
Q

what does the term radio parent mean?

A

does not have a habit of absorbing X-rays

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10
Q

What is radioparent in the X-ray cassette?

A

the cassette face

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11
Q

What is the reflective layer of screens in a cassette made of?

A

titanium oxide

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12
Q

What is the function of the reflective later of cassette screens?

A

it redirects light created during exposure back towards the film

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13
Q

Edison discovered calcium tungstenate to be able to glow efficiently when exposed to radiation. This material was the gold standard in X-ray technology for a long time, but has been replaced with what rare earth phosphors?

A

gadolinium
lanthanum
yttrium

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14
Q

The base layer of screens in mostly made of

A

polyester or cellulose triacetate, which are radioparent, chemically inert, tough and flexible

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15
Q

What creates “faster” screens?

A

thicker phosphor layers and larger crystals in the phosphor

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16
Q

thicker phosphor layers and larger crystals in the phosphor result in

A

lower detail than thinner phosphor layers and smaller crystals but greater speed of x-ray exposure

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17
Q

the portion of electromagnetic spectrum the film is most sensitive to?

A

spectral sensitivity

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18
Q

Spectral sensitivity should match what?

A

the spectral emission of the screens used in the film

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19
Q

What is the formula for adjusting mAs for changing screen speed

A

(speed1/speed2) x mAs1 = mAs2

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20
Q

What is spectral emission

A

the color of light emitted by a phosphor

21
Q

What is the protective layer of the screen

A

a thin transparent supercoat consisting of gelatin that protects the the emulsion of the phosphor on the film

22
Q

How often should screens be cleaned?

A

monthly if films are taken every day

quarterly if films are taken once a week

23
Q

What is screen speed?

A

the efficiency of a screen in converting x-rays to light

24
Q

greater screen efficiency =

A

less exposure = faster screen

25
Q

A screen with a speed of 200 would be twice as fast as a 100 speed screen and require _____ as much exposure

A

half

26
Q

What screen speed is used for general purpose radiography?

A

400-600

27
Q

What screen speed is used for extremity or other detailed radiography?

A

100

28
Q

big crystals in thick layer =

A

fast exposure, lower detail

29
Q

small crystals in thin layer =

A

slow exposure, greater detail

30
Q

How do you calculate the change in technique needed to create a film of equal density on two different system speeds?

A

(system speed 1/system speed 2) x mAs 1 = mAs 2

31
Q

Components of a film emulsion:

A
  • gelatin (support medium)
  • silver halide micro crystals (active ingredient, 90% silver bromide and 10% silver iodide)
  • silver sulfide (sensitivity center)
32
Q

Why is film screen contact important?

A

it prevents loss of detail

33
Q

film screen contact is negatively affected by:

A
  • foreign material in the cassette or on screen
  • dents due to objects dropped on screen or closed inside the cassette
  • damage due to improper mounting
  • deterioration of padding
  • warping of screen from getting wet
34
Q

What is a latent image?

A

the image that has been created after exposure but before development, so it cannot be seen yet

35
Q

What are some causes of undesired exposure of film?

A
  • unintended light exposure
  • scattered x-rays
  • heat
  • chemicals or fumes
  • pressure
  • age
36
Q

film speed is directly proportional to what?

A

mAs

37
Q

slower film speed = _____ detail

A

more detail

38
Q

faster film speed = _____ detail

A

less detail

39
Q

How should film be stored?

A

vertically oriented in a light proof case that is kept cool, clean, dry and ventilated

40
Q

The rules and best practices established by the American college of radiology (ACR) and the national electronic manufacturing association (NEMA) to ensure standard and protocols for image and communications formatting

A

DICOM (digital imaging and communications in medicine) standards

41
Q

Sets standard for what can and cannot be disclosed without the patient’s consent to provide for confidentiality, safety, and protection of health information

A

HIPPA (health insurance probability and affordability act)

42
Q

Establishes rules and incentives for transition to digital health record management and rules regarding digital acquisition, sharing, storage, safe keeping and privacy in the digital universe

A

HITECH (health information technology for economic and clinical health) act

43
Q

What are the three digital imaging platforms?

A
  • analog films converted to digital images
  • computer radiography
  • direct (digital) radiography
44
Q

computed radiography uses a ______ instead of film

A

detector plate (aka photostimulateable phosphor plate, PSP)

45
Q

The digital plate that is used in digital radiography is a(n) _______ consisting of millions of indexical semiconductor elements deposited onto a substrate material

A

active matrix liquid crystal flat panel display - AMLCD

46
Q

What is PACS?

A

picture archival and communication system - the software that stores, organizes and allows for seamless integration of images from storage to terminal interface

47
Q

All images subject to compression for storage purposes must have _____

A

reversible compression without loss of original data

48
Q

Can imaged being exported for interpretation or review be partial studies?

A

no, they must be complete studies

49
Q

Which is more expensive: direct or computed radiography?

A

direct radiography