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MIDTERMS - 3RD YR TRANSES > INTERVENTIONAL RADIOLOGY > Flashcards

INTERVENTIONAL RADIOLOGY Flashcards

1
Q

In DF, the spatial resolution is determined both

A

image matrix and by the size of the image intensifier

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2
Q

Spatial resolution is limited by

A

pixel size

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3
Q

A major change from conventional fluoroscopy to DF is the use of a ___ instead of a TV camera tube

A

charge-coupled device (CCD)

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4
Q

Military applications ___

A

night vision scopes

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5
Q

The sensitive component of a CCD is a layer of __.

A

Crystalline Silicon

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6
Q

When this silicon is illuminated, ___ is generated, which is then sampled, pixel by pixel, and manipulated to produce a digital image.

A

electrical charge

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7
Q

Spatial resolution of a CCD: determine by

A

its physical size and pixel count

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8
Q

1024 matrix can produce images with __ spatial resolution.

A

10 lp/mm

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9
Q

Television camera tubes: __

A

“pin cushion” or “barrel” artifact

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10
Q

The CCD has greater sensitivity to

A

light

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11
Q

Because of heated filaments and voltage differences, a very small electric current always is flowing in any circuit
This is called

A

background electronic noise

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12
Q

The tube with a __ SNR provides five times the useful information and is more compatible with computer-assisted image enhancement

A

1000 : 1

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13
Q

The __ from the image-intensified digital image receptor is transmitted to an analog-to digital converter (ADC)

A

output signal

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14
Q

To be compatible with the computer, the __

A

ADC must have the same dynamic range as the DF system.

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15
Q

An 8-bit ADC would convert the analog signal into values between __

A

0 and 255

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16
Q

A 10-bit ADC would be more precise, with an ADC range from__

A

0 to 210 or 0 to 1023.

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17
Q

The output of the ADC is then transferred to ___ and is manipulated so that a digital image in matrix form is stored.

A

main memory

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18
Q

__ is amplified and is transmitted by cable to the television monitor, where it is transformed back into a visible image.

A

video signal

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19
Q

television monitor forms

A

one end of a closed-circuit television system. The other end is the television camera tube or CCD.

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20
Q

Two differences between closed-circuit television fluoroscopy and home television are

A

no audio and no channel selection

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21
Q

Usually, the radiologic technologist manipulates only two controls:

A

contrast and brightness

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22
Q

The principal advantages of DF examinations are the ___ that are possible and the enhanced visualization of vasculature that results from venous injection of contrast material

A

image subtraction techniques

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23
Q

Refers to a number of computer-assisted techniques whereby an image obtained at one time is subtracted from an image obtained at a later time.

A

Temporal Subtraction

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24
Q

Two methods are commonly used: the __ in temporal subtraction

A

a.) mask mode and the b.) time-interval difference (TID) mode

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25
Q

results in successive subtraction images of contrast-filled vessels

A

Mask Mode

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26
Q

Each image was obtained from a __ x-ray pulse. The time required for one video frame is __

A

33-ms; 33 ms

27
Q

Imaging sequence after acquisition of the mask can be ___

A

controlled manually or pre-programmed

28
Q

the use of later images as mask image.

A

Remasking

29
Q

Produces subtracted images from progressive masks and following frames

A

Time-Interval Difference Mode

30
Q

Occurs if patient motion occurs between the mask image and a subsequent image.

A

Misregistration artifact

31
Q

Same anatomy is not registered in the same pixel of the image matrix
This type of artifact frequently can be eliminated by __ of the mask. Done by shifting the mask by one or more pixels so that __ of images is again obtained

A

re-registration; superimposition

32
Q

Uses two different x-ray beams alternately. Images are results of differences in __

A

Energy Subtraction; photoelectric interaction

33
Q

When the incident x-ray energy is sufficient to overcome the K-shell electron binding energy of iodine, an abrupt and large increase in absorption occurs
Graphically, this increase is known as the

A

K absorption edge.

34
Q

Other methods: FOR ENERGY SUBTRACTION

A

(1) Alternately pulsing the x-ray beam at 70 kVp and then 90 kVp and
(2) Introducing dissimilar metal filters into the x-ray beam alternately on a flywheel

35
Q

Combining temporal and energy subtraction techniques

A

hybrid subtraction

36
Q

the components
used in conventional fluoroscopy

A

X-ray source, image intensifier, TV camera, TV monitor

37
Q

___ is a digital x-ray imaging
system that produces dynamic images obtained with
an area x-ray beam. The difference between conventional fluoroscopy and DF is the __

A

Digital fluoroscopy (DF); nature of the image and the manner in which it is digitized

38
Q

Images from DF are obtained by
pulsing the x-ray beam in a manner called

A

pulse progressive fluoroscopy

39
Q

During DF, the x-ray tube operates in the __

A

radiographic mode

40
Q

__ is required to produce a single video frame, x-ray exposures longer than this can result in unnecessary
patient radiation doses. This is a theoretical limit, however, and longer exposures may be necessary to ensure low noise and good image quality

A

33 ms

41
Q

The time required for
the x-ray tube to be switched on and reach selected
levels of kilovolt peak (kVp) and mA is called

A

interogation time

42
Q

The time required for the x-ray tube to be switched off is the

A

extinction time

43
Q

DF systems must incorporate high-frequency generators with interrogation and extinction times of less than __

A

1 ms

44
Q

The fraction of time that the x-ray tube is energized is called

A

duty cycle

45
Q

When this silicon is illuminated, electrical charge is generated, which is then sampled, pixel by pixel, and manipulated to produce a __.

A

digital image

46
Q

The CCD is mounted on the __ and is coupled through fiberoptics or a lens system

A

output phosphor of the image-intensifier tube

47
Q

Advantages of Charge-Coupled
Devices for Medical Imaging

A

High spatial resolution
* High SNR
* High DQE
* No warm-up required
* No lag or blooming
* No spatial distortion
* No maintenance
* Unlimited life
* Unaffected by magnetic fields
* Linear response
* Lower patient radiation dose

48
Q

Advantages of Flat Panel Image
Receptors Over Charge-Coupled Device
Image Intensifiers in Digital Fluoroscopy

A
  • Distortion-free images
  • Constant image quality over the entire image
  • Improved contrast resolution over the entire image
  • High DQE (see Chapter 16) at all radiation dose
    levels
  • Rectangular image area coupled to similar image
    monitor
  • Unaffected by external magnetic fields
49
Q

__ is particularly helpful for digital subtraction angiography (DSA) and results in improved
dynamic range and better contrast resolution.

A

linear response feature

50
Q

flat panel image receptor (FPIR). Such an image receptor is composed of

A

cesium iodide (CsI)/amorphous
silicon (a-Si) pixels

51
Q

The __ is much smaller and lighter and is manipulated more easily than an image intensifier. The __ imaging suite provides easier patient manipulation and
radiologist or technologist movement, and there are no
radiographic cassettes.

A

FPIR

52
Q

The image intensifier is limited by__ from the center to the
periphery of the circular image

A

nonuniform spatial
resolution and contrast resolution

53
Q

The video system used in conventional fluoroscopy is
usually a ___ system. Such a system is inadequate
for DF.

A

525-line system

54
Q

It is similar to the noise (fog) on a radiograph in that it conveys no information and serves
only to obscure the electronic signal and reduce image
contrast.

A

background electronic noise

55
Q

The tube with a 1000:1 SNR provides __ the useful information and is more compatible with computer-assisted
image enhancement

A

five times

56
Q

Important characteristics of a DF
system that are computer controlled include the

A

image matrix size, the system dynamic range, and the image
acquisition rate.

57
Q

The output signal from the image-intensified digital
image receptor is transmitted to an __

A

Analog-to-Digital converter

58
Q

The dynamic range of each pixel, the number of pixels, and the method of storage determine the
__ with which the image can be acquired, processed, and transferred to an output device.

A

speed

59
Q

DF provides better contrast resolution through __ of image subtraction

A

postprocessing

60
Q

__ mode produces subtracted images from
progressive masks and following frames.

A

TID

61
Q

The probability of photoelectric absorption in
all three decreases with increasing x-ray energy. At an
energy of __

A

33 keV

62
Q

___ is a special application of DSA. A mask
image is acquired and stored

A

roadmapping

63
Q
A

MIDTERMS - 3RD YR TRANSES (8 decks)

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