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Imaging > Lecture 5- Fluoro > Flashcards

Lecture 5- Fluoro Flashcards

1
Q

which of the following is not an attribute of a fluorscopy vs. radiography

A

d

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2
Q

what is flour used for

A

real time X-ray imaging of anatomy with X-ray contrast agents or devices.

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3
Q

what is the difference between fluoro and cine

A

cine is higher dose for diagnosis and device placement while fluoro is used for navigation and localization

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4
Q

what is angiography

A

injection of contrast into vessels

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5
Q

what is not in a fluoroscopy X-ray assembly

A

output phosphor

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6
Q

what interaction creates xrays

A

bremsstrahlung

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7
Q

does the cathode give or take electrons

A

cathode gives the electrons.

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8
Q

what do filters do and what do collimators do

A

filters reduce the low energy rays so it decreases overall patient dose. the collimator restricts the field of view

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9
Q

what is a KAP meter

A

it is a radiation soe meter

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10
Q

what is AERC

A

automatic exposure rate control that set dose to be reserved so increase or decrease output so that patient gets a higher or lower dose

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11
Q

why is the dose per image lower for fluoro

A

it is given over a longer time so they need a lower starting dose per image

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12
Q

what is typical per pulse for fluro, acquisition, digital subtraction, and digital radiography

A

10-40, 120-250, 2000-4000, 5000-10,000.

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13
Q

what is the problem with noise from electrical components

A

needs to be very low because the signal is already low

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14
Q

what are X-ray control parameters

A

peak tube potential, beam filter, current, pulse duration, frame rate per second, collimation and field of view

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15
Q

what is usually used as a filter

A

copper

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16
Q

what happens to the spectrum when a copper filter is used also draw the changes in HVL

A

copper filters are used and it shifts the energy to the right because lose lowe energy. Image contrast reduction but decreases the dose significantly while only lowers contrast csome

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17
Q

when is the machine on and off for fluro

A

it used to be on constantly then the receptor pulsed, but not the X-ray is mostly off and the receptor is always on

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18
Q

how does AERC contribute to image quality

A

it does not normalize image quality. it only controls the specified radiation dose. due to changes in subject contrast with changes in KVP and contribution of scatter, AERC does not result in equal images for each condition.

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19
Q

as patient thickness increases, the SNR

A

decreases

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20
Q

what are the drawbacks of large patients

A

as KVP increases the subject contrast decreases, and the dose increases as the current increases, aAS the pulse duration has to increase, the blur increases as well. High anode heting is required for larger focal spot and there is larger penumbral blur. As scatter to primary increases, the SNR decreases. the net effect is that large patient equals large dose which decreases image quality

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21
Q

what is the risk of using iodine as contrast

A

kidney nephropathy

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22
Q

what is attenuation

A

absorption and scatter of X-ray beam by the patient substantially reduces the X-ray beam intensity AERC

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23
Q

what is the primary source of occupation exposure to xray

A

scatter fom the patient

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24
Q

what happens to X-rays that do not interact with tissue

A

it is transmitted

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25
Q

X-rays that interact- what happens

A

they are attenuated, which leads to scatter or some energy absorbed which is the radiation dose

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26
Q

what is the formula for exponential attenuation

A

It=Ioe-ut It is the transmitted insanity, I0 is the incident intensity, u is the linear attenuation coefficient, and t is the thickness

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27
Q

what does differential attenuation do

A

it produces modulation in X-ray intensity, image contrast, and so this is how images look different as it goes through different tissue

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28
Q

thicker patients means what to KEVP

A

it needs increased KEVP

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29
Q

what happens to the contrast potential of iodine

A

it decreases rapidly further to the right and this lowers the contrast potential

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30
Q

what is forward scatter

A

these are rays that go towards the detector and contribute to noise and decreased quality of the image

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31
Q

what is side scatter

A

occupation radiation

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32
Q

what is back scatter

A

occupation and contributes to the higher dose overall

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33
Q

what does an anti scatter grid do

A

it transmitters 80-75% of the primary and it transmitts 10-30% of the scattered beam. It improves the signal to noise ratio

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34
Q

what is the bucky factor

A

how much the dose must increases to make up for the grid taking out some of the primary

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35
Q

what does the detector do

A

it creases a shadow then image

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36
Q

what is an image intensifier

A

it makes the image better by turning low energy things into higher energy things

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37
Q

what is not a part of an image intensifier

A

photoiodide

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38
Q

what does an input screen do

A

the cesium iodide scintillator covers the X-rays into visible light

39
Q

what does the photocathode do

A

it concerts the visible light into free electrons

40
Q

what is the k edge of the scintillator

A

33 kev

41
Q

what is the photocathode made of

A

thin layer of antimony and alkali metals which emit electrons in response to visible light. very low conversion efficiency

42
Q

what is a focusing electrode

A

it focuses on the photocathode onto the output screen

43
Q

what is the brightness gain

A

it is the acclearation of electrons between the input screen and output screen

44
Q

what is the brightness gain range

A

is it 2500 to 7000

45
Q

what deformity can be caused by electron optics and speeding up

A

pincushion deformity

46
Q

what is the role of the output screen

A

it is positively charged, so it attracts electrons and converts the moving electrons to visible light

47
Q

what is optical coupling and what is it coupled to

A

output phosphor is attached to the camera, and it creaates the image

48
Q

is higher or lower SNR better

A

higher

49
Q

what is a CCD camera

A

it is a charge coupled device that couples the phosphor with the lines and aperture can lose SNR of it

50
Q

what is a CMOS camera

A

light to electrons, but each puzzle has its own ADC and sends its own things, so no stepping between the detector

51
Q

magnification mode with II

A

uses a smaller field of view, so it uses a small II area, so the entire area of output phosphor is used, and it increases the object plane-spatial resolution.

52
Q

does the increased magnification increase dose

A

it used to increase dose because it needed to maintain the output phosphor intensity and electron density, but requires an increased intensity and increased technique

53
Q

what is quantum detection efficiency

A

want to absorb lots of electrons and it is not a good decrepit of the detector to efficiently covery all X-ray fluency into a useful image

54
Q

flat panel what is the shape of the electrophores

A

the electrophorus are discrete

55
Q

what is the chemical used in this pixel

A

Cesium iodide

56
Q

how is the electric charge propogated through flat panel detector array

A

electronic charge is released pixel by pixel, amplified, and converted to a digital value by an analog to digital converter. Utilizes solid state and miniaturized components. Electronic noise results in lost SNR for low dose fluoro

57
Q

what happens to the stored charge in a flat panel detector

A

it is released, amplified, analog to digital, converted to digital, and sent to an image processor

58
Q

what happens to magnification with flat panel

A

it becomes gridy looking

59
Q

are images from fluro saved to the patient record

A

no

60
Q

what happens with continuous fluror

A

it is X-ray beam is continually on and creates images at 30 fps, and it is still used for portable

61
Q

what is pulsed fluoro

A

it is where the beam is switched on and off, and images at created at that rate. It is more common for angiography systems

62
Q

what is the dose rate of cine compared to fluro

A

it is 10-20x the rate

63
Q

are cine continuous or pulsed and are the images saved

A

images are saved, and it is at 15fps and the beam is pulsed and images are created at that rate

64
Q

DSA what is it and whats the rate and what is it used for

A

dose rate is higher than flour and it is used for vascular imaging, and used for diagnosis

65
Q

is DSA pulsed or continuous

A

it is pulsed and it is usually 2-4 fps

66
Q

what is the point of DSA

A

it can subtract overlying anatomical noise for better vessel pictures

67
Q

what are the methods behind DSA

A

acquire a mask of image of the anatomy, inject contrast into the vessel of interest. Acquire contrast image of the amantomy and contrast vessel then transform to subtract it

68
Q

what happens to noise when you use DSA

A

it decreases the noise because it subtracts other random noise as well DSA source images are high dose and high SNR

69
Q

what does a c-arm do

A

it can cone CT and recontruct the path of the arm

70
Q

what is the issue with cone beam CT or c-arm

A

it has streak atrifacts and high density and moving objects- limited rotational range

71
Q

what is the application of cone beam CT and angio

A

it can show native anatomy and measurements with device placement

72
Q

cone beam and angio are applied to what for the heart procedure

A

TAVR

73
Q

what happens to contrast in fluoro

A

signal difference between object of interest and neighboring anatomy

74
Q

what happens to noise in fluoro

A

small area variation in signal intenstity due to random nature of X-ray production and detection

75
Q

what happens to spatial resolution in fluoro

A

spatially lateral spread of signal within the imaging system. Penumbral blur, light spread, and X-ray scattering

76
Q

what happens to signal difference in fluoro

A

grayscale intesntity difference between object of interest and surrounding image

77
Q

what happens to resolution in fluoro

A

spatial precision which small objects and sharp edges are produced

78
Q

what happens to noise in fluoro

A

random, small area, greyscale intensity variation due to the random nature of X-ray production, attenuation, and detection

79
Q

what happens with when the signal increaseds with fixed noise

A

it can still be seen just fine, so sometimes the image is fine with more noise

80
Q

what leads to blur in terms of modelign

A

the lateral spread of the signal when it is transformed from a point stimulus to a point spread function leads to blur. the spread is from convolution

81
Q

flat panel does what with spatial resoltuon

A

flat panel has less things affecting spartial resolution

82
Q

what happens to spatial resolution as the field of view increases

A

resolution decreases with field of view because larger input phosphor are is forced onto a discrete matrix. Resolution decreased with the field of view because large FP pixel matrix is forced on a a smaller matrix electronic display

83
Q

what is image perception influenced by

A

technical image quality, image processing, visual acuity, experience, clinical context

84
Q

what tissue gets the highest dose in fluoro

A

skin

85
Q

what determines how the dose changes over a depth

A

inverse square law

86
Q

what monitors tube output

A

it is from air karma, It is a virtual point in space.

87
Q

what does air karma lack

A

correct Xray source to skin stance, correlation with skin irradiated, skin dose contribution from scatter internal to the patient

88
Q

what is the maximum air karma for fluoro

A

87.3 mgy/min

89
Q

what is the high level control max rate of fluoro

A

175 mgy/min

90
Q

is the max air karma rate distance the same as the image receptor

A

no it is at 30 com from the X-ray tube which is not the IRP

91
Q

is there a limit for maximum cine air karma rate

A

no

92
Q

what patients are most likely to get skin injury

A

large patients and complex lifesaving procedures

93
Q

what is the threshold dose for skin injury

A

2gy

Imaging (19 decks)

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