8. Image-Intensified Fluoroscopy Flashcards
1
Q
to aid the radiologist in dynamic studies of the human body
A
Fluoroscopy
2
Q
“real time” imaging
A
Fluoroscopy
3
Q
Thomas Edison invented the fluoroscope (calcium tungstate screen) year
A
1896
4
Q
William Chamberlain studies on the poor illumination from fluoroscopic screen year
A
1941
5
Q
development of image intensifier tube year
A
1950’s
6
Q
measure in units of Lamberts (L) and millilamberts (mL) (SI unit-lumens)
A
Illumination
7
Q
Radiographs are viewed under illumination level of ____
A
10 to 1000 mL
8
Q
Human vision– rods and cones
A
- Photopic and scotopic vision
* Visual acuity
9
Q
Fluoroscopic Chain
A
- Image intensifier
- Recording system
- Viewing system
10
Q
electronic vacuum tube that converts the remnant beam to light then to electrons, then back to light, increasing the light intensity in the process
A
Image intensifier
11
Q
complex electronic device that receives the remnant x-ray beam, coverts it into light, and increases the light intensity
A
Image intensifier
12
Q
it brightened the image significantly
A
Image intensifier
13
Q
allows for a means to indirectly viewing the fluoroscopic image
A
Image intensifier
14
Q
Basic Parts of an Image Intensifier
A
- Input Phosphor
- Photocathode
- Accelerating Anode
- Output Phosphor
- Electrostatic Focusing lenses
15
Q
Input Phosphor is made of
A
Cesium Iodide (CsI)
16
Q
Converts energy to visible light
A
Input Phosphor
17
Q
CsI crystals are tightly packed as ____ layer
A
100 to 200 micrometer
18
Q
composed of Cesium and antimony compounds
A
Photocathode
19
Q
emit electrons when stimulated by light (photoemission)
A
Photocathode
20
Q
maintains constant potential of approximately 25 kV
A
Accelerating Anode
21
Q
electrons interact to produce light
A
Output Phosphor
22
Q
usually made of silver-activated zinc-cadmium sulfide
A
Output Phosphor
23
Q
engineering aspects of maintaining proper electron travel
A
Electron Optics
24
Q
located along the length of image intensifier tube
A
Electrostatic Focusing Lens
25
not really lenses, but are negatively charged plates along the length of the Image Intensifier tube
Electrostatic Focusing Lens
26
approximately 50 cm in length and 15 to 58 cm in diameter
Image Intensifier Tube
27
high energy electrons that interact with the output phosphor each result in substantially more light photon than was necessary to cause their release at the photocathode
Image Intensifier Tube
28
Parts of Image Intensifier
* Output Window
* Output Phosphor
* Photocathode
* Input Window
* Input Phosphor
* Evacuated Tube
29
the ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor
Flux Gain
30
represents the tube’s conversion efficiency
Flux Gain
31
Flux Gain=
Flux Gain = number of output light photons/ number of input x-ray photons
32
an expression of the degree to which the image is minified from the input phosphor to output phosphor
Minification Gain
33
the ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor
Minification Gain
34
this characteristic makes the image brighter because the same number of electrons is being concentrated on a smaller surface area
Minification Gain
35
output phosphor size is fairly standard at _____
2.5 or 5 cm
36
input phosphor size varies from ___
10 to 35 cm
37
brightness gain of most image intensifiers is ____
5000 to 20,000
38
is an expression of the ability of an image intensifier tube to covert x-ray energy into light energy and increase the brightness of the image in the process
Brightness Gain
39
the ability of the image-intensifier tube to increase the illumination level of the image
Brightness Gain
40
Brightness Gain =
Brightness Gain = minification gain x flux gain
41
is an expression of the luminance at the output exposure rate
Conversion Factor
42
recommended by the ICRU to quantify the increase in brightness created by Image intensifier
Conversion Factor
43
as an image intensifier ages, the exposure rate to the patient ____ to maintain brightness
increases
44
a function of the fluoroscopic unit that maintains the overall appearance of the fluoroscopic image by automatically adjusting the kVp, mA or both
Automatic Brightness Control (ABC)
45
the voltage to the electrostatic focusing lenses is increased
•the increase tightens the diameter of the electron stream and the focal point is shifted farther from the output phosphor
Magnification Mode or Multi-field Mode
46
the effect is that only those electrons from the center area of the input phosphor interact with the output phosphor and contribute to the image, giving the appearance of magnification
Magnification Mode
47
may be found by dividing the full-size input diameter by the selected input diameter
degree of magnification (MF)
48
degree of magnification (MF) =
MF = 30 / 15 = 2 x magnification
49
improves the fluoroscopist’s ability to see small structures (spatial resolution) but at the price of increasing patient dose
Magnification
50
Fluoroscopic systems – ____ Lp/mm
4 to 6 Lp/mm
51
is a result of inaccurate control or focusing of the electrons released at the periphery of the photocathode
Distortion
52
combined result in unequal magnification
pincushion appearance
53
reduction of brightness at the periphery
Vignetting
54
results when insufficient information is present to create the image
Image Noise
55
insufficient quantity of x-rays
Image Noise
56
"grainy” or “noisy” image
Image Noise
57
Fluoroscopic Image Monitoring parts
* Camera Tube
| * Charged-coupled Device (CCD)
58
converts the light image into electric signal
Camera Tube – the television camera tube
59
are most often used television camera tube used in fluoroscopy
Vidicon and plumbicon
60
provides continuous stream of electrons
Electron gun
61
forms the electron streams into a “beam”
Control grid
62
Electromagnetic coils
* Deflection coils
* Focusing coils
* Alignment coils
63
act to accelerate and precisely control the electron beam
Electromagnetic coils
64
Through this action, the beam sweeps the anode back and forth from top to bottom in a sequence known as _____
Electromagnetic coils,
| raster pattern
65
light-sensitive semiconducting device that generates an electrical charge when stimulated by light and stores this charge in a capacitor
Charged-Coupled Device
66
the charge is proportional to the light intensity and is stored in rows and pixels
Charged-Coupled Device
67
is a series of metal oxide semiconductor capacitors, with each capacitor representing a pixel
Charged-Coupled Device (CCD)
68
Coupling the Television Camera
* Fiber-optics bundle
| * Lens-coupling
69
simply a bundle of very thin optical glass filaments
Fiber-Optics Bundle
70
very durable and simple in design but does not allow for spot filming
Fiber-Optics Bundle
71
series of optical lenses that focus the image from the output phosphor on the camera tube
Optical Lens System
72
Susceptible to rough handling, which may cause maladjustment of the mirrors and lenses and result in a blurred image
Lens-coupling
73
Beam-splitting mirror enables ____
spot filming
74
heart of television monitor
Television Monitor – television picture tube (cathode ray tube)
75
convert the electronic signal from the camera tube or CCD back into a visible image
Television Monitor – television picture tube (cathode ray tube)
76
Television Monitor – television picture tube (cathode ray tube) - ___ Lp/mm
1 to 2 Lp/mm
77
the camera tube and CCD are devices that couple the image intensifier to the television monitor to convert the image from the output phosphor to an electronic signal that can be reconstructed on the television monitor
Coupling Systems and Television Monitor
78
Recording Systems
* Cassette Spot Film
* Film Camera
* Video Recorders
79
static imaging process in which a standard radiographic cassette is used to obtain an image
Cassette Spot Film
80
The unit shifts to radiographic mode and the radiation dose to the patient is much higher than in fluoroscopic mode
Cassette Spot Film
81
sometimes called photo-spot cameras
Film Cameras
82
commonly use 105-mm “chip:film or 70-mm roll film
Film Cameras
83
static imaging that is used with an optical lens system incorporating a beam-splitting mirror
Film Cameras
84
used when dynamic imaging is desired
Video Recorders
85
useful in functional studies of the esophagus or placement of catheters or medical devices, for example
Video Recorders
86
used analog-to-digital converter (ADC)
Digital Fluoroscopy
87
computer between the camera tube and the monitor
Digital Fluoroscopy
88
a device that takes the video (analog) signal and divides in into a number of bits (1s and 0s) that the computer “understands”
Analog-to-Digital Converter (ADC)
89
the number of bits that the signal is divided into determines the contrast resolution of the system
Analog-to-Digital Converter (ADC)
90
eliminated some of the problems associated with the camera tube
CCD
91
more light-sensitive (higher DQE) and exhibits less noise and no spatial distortion
CCD
92
higher spatial resolution and less radiation
CCD
93
Flat-panel Detectors
* Cesium iodide amorphous silicon indirect capture
| * amorphous selenium direct-capture detector
94
Advantages of Digital Fluoroscopic Systems compared to Image Intensifier
* Reduction in size, bulk and weight of the fluoroscopic tower, allowing for easier manipulation, greater access to patient during examination
* Replace spot filming and other recording devices
* Can be readily archived with the patient record in PACS
* Does not degrade with age
* More durable
* Better contrast resolution
* Higher DQE
* Wider dynamic range
* Post-processing options
* Do not exhibit most image artifacts such glare and peripheral distortion
* Lower patient dose
