Flashcards in Physics Chapter 14 Deck (46):
1
Know the two ways that image intensifiers improved the image process
*Brightened the image significantly (eliminated the need to dark adapt)
*Allowed for a means of immediately viewing the fluoro image (reduced radiographic dose)
2
Know what the conventional fluoroscopic chain consists of
x-ray tube, an image intensifier, a recording system, and viewing system
3
Know the 5 basic parts that make up an image intensifier
Input phosphor, photo cathode, electrostatic focusing lenses, accelerating anode, and output phosphor
4
Know why the input phosphor is made of cesium iodide
It absorbs remnant x-ray photon energy and emits light in response
5
Know the size correlation between the input and output phosphor
output phosphor is much smaller
6
Know how brightness gain has traditionally been found
Multiplying the flux gain by the minification gain
7
Know the size of the image intensifier tube
50 cm in length and 15-58 cm diameter
8
Know how flux gain is expressed
The ratio of the number of light photons at the output phosphor to the number of light photons emitted in the input phosphor
9
WHat results from the higher the conversion factor or brightness gain factor
image appears brighter because the same number of electrons is being concentrated on a smaller surface area
10
Know what happens as the image intensifier tube ages
The ability of the image intensifier to increase brightness deteriorates with the age of the tube
11
Know what happens in regards to radiation as the image intensifier tube ages
More and more radiation is necessary to produce the same level of output brightness, translating to an increased patient dose
12
Know how ABC commonly operates
By monitoring the current through the image intensifier or the output phosphor intensity and adjusting the exposure factor if the monitored value falls below preset levels
13
Know how to find the degree of magnification
Dividing the full size input diameter by the selected input diameter
14
Know what magnification improves
The fluoroscopist's ability to see small structures (spatial resolution) but at the expense of increasing patient dose
15
Know how spatial resolution is measured
Line pairs per millimeter
16
Know what distortion is a result of in fluoro
Inaccurate control or focusing of the electrons released at the periphery of the photocathode and the curved shape of the photocathode
17
Define a pincushion appearance
The combined result is an unequal magnification (distortion) of the image
18
Know how a "noisy" or "grainy" image occurs
If too few x-rays exit the patient and expose the input phosphor, then not enough light is produced, which decreases the number of electrons released by the photocathode to interact with the output phosphor
19
Know how to fix a "noisy" image
increasing the mA
20
Know what the 2 devices are that convert the image from the output phosphor to an electrical image
The camera tube and charge-coupled device (CCD)
21
Know what the camera tube most often used is
vidicon tube
22
Know what the deflection coils act to accelerate
the electron beam
23
Know what the CCD is made from
A series of metal oxide semiconductor capacitors
24
Know what is sent from the capacitors
Charge is sent as an electronic signal to the tv monitor
25
Know what the purpose of the television monitor is
Convert the electrical signal from the camera tube to CCD back into visible light
26
Know what typical television monitors are called
525 line systems
27
Know the resolution of HIGH resolution monitors
1024 lines per frame
28
Know what the image intensifier is capable of resolving
Approximately 5 lp/mm whereas the monitor can display only 1-2 lp/mm
29
Know the 3 types of recording systems
Cassette sport film, film cameras, video recorders
30
Know what happens when the spot film exposure button is pressed
The cassette is moved into position between the patient and image intensifier and the machine shifts from fluoroscopic to radiographic mode and exposes the film
31
Know what happens in regards to radiation dose when imaging from fluoro to radiographic mode
fluoro to the radiographic mode uses a much higher radiation dose to the patient
32
Know what film is commonly used in the film cameras
105 mm "chip" film or 70 mm roll film
33
Know what the number of bits that a signal is divided into determines
the contrast resolution (number of gray shades) of the system
34
Know what the charge-coupled device (CCD) eliminated
Some of the problems associated with the camera tube
35
Know the 2 forms of flat panel detectors are used for fluoroscopic applications
*cesium iodide amorphous silicon indirect capture detector
*amorphous selenium direct capture detector
36
Know why the size, bulk, and weight of the fluoroscopic tower in digital fluoro is an advantage
Flat panel reduces all 3 allowing easier manipulation of tower, greater flexibility of movement and greater access to the patient during the exam
37
Know what the flat-panel detectors replaced
the spot0filming and other recording devices
38
Know why additional radiographic images are commonly not needed in digital fluoroscopy
they are capable of operating in radiographic mode
39
Be able to describe some of the other advantages of digital fluoro
*flat panel detectors don't degrade with age
*more durable
*provide more information
*better contrast resolution
*higher detective quantum efficiency
*wider dynamic range
40
Know the advantage of digital fluoro in regards to artifacts
They do not exhibit most image artifacts such as veiling glare and peripheral distortion seen with image intensifiers
41
Know the advantage of digital fluoro in regards to radiation dose
50% lower radiation dose
42
Know why Quality Control Programs are vitally important for all ionizing radiation producing equipment
to monitor equipment performance and minimize patient dose
43
Know the role of the radiologist in a quality control program
supervision of the whole quality control program and process
44
Know the role of a radiographer in a quality control program
facilitator in the process
45
Know the role of the medical physicist in a quality control program
has primary responsibility for performance testing and interpretation
46