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FEESICKS BUSHBIRD III > Chapter 9 - Fluoroscopy > Flashcards

Chapter 9 - Fluoroscopy Flashcards

1
Q

The principal feature of the imaging chain that distinguishes fluoroscopy from radiography…

A

Ability to produce real-time X-ray images with high frame rates and a low-dose per image

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2
Q

Basic product of a fluoroscopic imaging system

A

Projection X-Ray image

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3
Q

4 principal components of an II(image intensifier):

A
  1. Vacuum housing
  2. Input layer
  3. Electron optics system
  4. Output phosphor
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4
Q

(II component) keeps air out and allow unimpeded electron flow

A

Vacuum housing

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5
Q

(II component) converts the absorbed incident X-rays into light, which in turn releases electrons

A

Input layer

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6
Q

(II component) accelerates and focuses the electrons emitted by input layer into the output layer

A

Electron optics system

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7
Q

(II component) converts the accelerated electrons into a visible light image

A

Output phosphor

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8
Q

In IIs, an antiscatter grid is mounted _____ to the input layer on the housing

A

Adjacent

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9
Q

Virtually all modern IIs use _____ for the input phosphor

A

Cesium Iodide (CsI)

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10
Q

The input phosphor/photocathode surface is CURVED to accommodate the physics of electronic focusing…distortion produce in the output image?

-result of projecting the image with a CURVED input phosphor to the flat output phosphor

A

Pincushion distortion

*remedy: position the desired anatomy in the central area of the FOV

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11
Q

Five-component (“pentode”) electronic lens system of the II

A

1-3. G1, G2, and G3 electrodes

  1. Input phosphor substrate (the cathode)
  2. Anode just proximal to the output phosphor
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12
Q

Made of zinc cadmium sulfide doped with silver (ZnCdS: Ag) , which has a green (530nm) emission spectrum

A

Output phosphor

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13
Q

A very thin (0.2 um) coating of aluminum on the vacuum side of the output phosphor, which is electrically conductive to carry away the electrons once they deposit their kinetic energy in the phosphor

A

Anode

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14
Q

The ratio of the area of the input phosphor to that of the output phosphor

A

Minification gain

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15
Q

Stray light reflecting inside the output window contributes to ______, which can reduce image contrast

A

Veiling glare

*reduce by using a thick (about 14 mm) clear glass window

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16
Q

Vidicon video systems typically operate at 30 FPS in an ____ scanning mode to reduce ____,the perception of the image flashing on and off.

A

INTERLACED, FLICKER

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17
Q

The human eye-brain system can detect temporal fluctuations slower than about ______

A

47 images/s

*therefore at 30 FPS, flicker would be perceptible

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18
Q

With interlaced systems, each frame is composed of two fields called _____

A

Odd and even fields

  • corresponding to every other row in the raster
  • ODD FIELD - starts at row 1
  • EVEN FIELD - starts at row 2
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19
Q

Solid-state electronic arrays (2) that convert a projection image into a digital image and then into a video signal

A
  1. Charge coupled device

2. Complementary metal oxide semiconductor (CMOS) photosensitive cameras

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20
Q

Characteristics unique to image intensifier systems (3):

A
  1. Brightness gain
  2. Pincushion distortion
  3. S distortion
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21
Q

Product of the electronic and minification gains of the II

A

Brightness gain

*as the effective diameter (FOV) of the input phosphor DECREASES, the brightness gain DECREASES.

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22
Q

A spatial warping of the image in an S shape thru the image

  • usually subtle
  • result of stray magnetic fields and the earth’s magnetic field affecting the electron trajectory from the cathode to the anode inside the II
A

S distortion

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23
Q

Comprised of thin film transistor (TFT) arrays of individual detector elements (dexels) that are packaged in a square or rectangular area

A

Flat panel detectors

24
Q

Regulates the SNR of the image constant when possible

  • Regulates the X-Ray exposure rate incident on the input phosphor of the II or flat panel detector
A

Automatic exposure rate control (AERC)

*formerly referred to as Automatic Brightness Control (ABC)

25
Q

Increasing kV, _____ the dose rate but contrast is _____

AERC

A

DECREASES; REDUCED

26
Q

Increasing mA, _____ the dose rate but ______ contrast

AERC

A

Raises; Preserves

27
Q

Produces a continuous X-Ray beam typically using 0.5 to 6 mA (depending on patient thickness and system gain)

A

Continuous fluoroscopy

28
Q

X-Ray generator produces a series of short X-Ray pulses

A

Pulsed fluoroscopy

29
Q

Yields higher spatial resolution for a smaller field of view

A

Magnification modes

30
Q

Brightness gain of the II ____ as the magnification increases

A

Decreases

31
Q

Can cause noticeable image lag with reduced temporal resolution

A

Frame averaging

32
Q

A common approach to frame averaging

  • the image just acquired is added together with the last displayed image
A

Recursive filtering

33
Q

Continuously displays the last acquired image or set of images on the fluoroscopy monitor

A

Last-frame-hold

34
Q

A software- and video-enhanced variant of the last-frame-hold feature and is useful for angiography procedures

A

Road mapping

35
Q

Capable of motorized rotation of about 220 degrees around the patient, which allows two-dimensional projection images to be acquired at many different angles around the patient

A

C-arm

36
Q

For routine QC testing in fluoroscopy, a ______ is commonly used to assess spatial resolution

A

Visual assessment of a resolution test object imaged with minimal geometric magnification

37
Q

Describes the maximum possible resolution in a digitally sampled imaging system

A

Nyquist Frequency

38
Q

Contrast resolution of fluoroscopy compared to radiography is ____

A

LOW

*chiefly due to the low SNR

39
Q

Contrast resolution is usually measured subjectively by viewing ___ under fluoroscopic imaging conditions

A

Contrast-detail phantoms

40
Q

2 advantages of fluoroscopy in comparison to radiography

A
  1. Excellent temporal resolution

2. Ability to provide real-time images

41
Q

Temporal blurring

A

Image lag

42
Q

Implies that a fraction of the image data from one frame carries over into the next frame

A

Lag

43
Q

Photoreceptors in the human eye produce a lag of about _____

A

0.2 s

44
Q

***page 301-303

FLUOROSCOPY SUITES

A
  1. Genitourinary
  2. Remote Fluoroscopy Rooms
  3. Peripheral angiography suites
  4. Cardiology catheterization suite
  5. Cardiology electrophysiology laboratory
  6. Biplane angiographic systems
  7. Mobile fluoroscopy - C arms
45
Q

The maximum permissible exposure rate to the patient
A. for normal fluoroscopy
B. For specially activated fluoroscopy

A

A. 87.3 mGy/m or (10 R/m)

B. 175 mGy/m (20 R/m)

46
Q

Dose rate limits are assessed at specified positions:
A. For systems in which the X-ray tube is below the patient
B. For c-arm fluoroscopes

A

A. One cm above the table

B. 30 cm from the image receptor toward the X-ray source along the central axis of the beam

47
Q

Typical entrance exposure rates for fluoroscopic imaging are about
A. For thin body parts
B. For the average patient

A

A. 8.7 to 17 mGy/m(1 to 2 R/min)

B. 26 to 44 mGy/m(3 to 5 R/min)

48
Q

Dose rates are evaluated in fluoroscopy by using a ___

A

Tissue-equivalent phantom

*made of a material such as polymethyl methacrylate (PMMA, aka Lucite or Perspex) placed in the field, with an ionization chamber positioned in front of it to measure the entrance skin dose

49
Q

To determine the maximum exposure rate , a ___ is placed between the PMMA and the detector system to attenuate the X-Ray beam and drive the AERC system to its maximum output

A

Sheet of lead

50
Q

Typical entrance Kerma rates for fluoroscopic detectors range from _____

A

8.7 nGy (1 uR) to 44 nGy (5uR) per frame

51
Q

Comprised of both leakage and scatter radiation

  • has a distinctly non-uniform distribution
  • chiefly due to backscattered radiation from the entrant beam surface
A

Stray radiation

52
Q

Required by some institutions when the integrated skin dose reaches predefined levels, in order to evaluate the benefits and risk of continuing with the procedure

A

Procedural pause

53
Q

Cumulative air Kerma may significantly over or underestimate the actual peak skin dose for three reasons (3)

A
  1. It does not account for backscattered radiation
  2. The X-ray beam may be incident upon a single area on the skin, or may be incident on multiple areas
  3. The skin may be closer or farther from the X-ray tube than the reference point at which the cumulative air Kerma is specified
54
Q

It is customary to wear a single dosimeter at the ______, in ____ of the protective apron

A

Collar level ; front

*second dosimeter may be worn on the body under the apron

55
Q

Most effective way to reduce patient dose during fluoroscopy

A

Use less fluoroscopy time

FEESICKS BUSHBIRD III (13 decks)

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