Physics Test 3 Flashcards
(72 cards)
1
Q
What are the two types of Automatic Exposure Control (AEC) and where are they located?
A
Ion Chamber is located above the Image Receptor (IR) and Photomultiplier tube is located below Image Receptor (IR)
2
Q
Which AEC uses light?
A
Photomultiplier tube
3
Q
- What kind of an image can the AEC produce?
a. continuous
b. static
d. dynamic
e. all of the above
A
b. static
4
Q
How many cells are located in each AEC scenario?
A
3
5
Q
- When using an AEC, what happens after the capacitor is full?
A
The capacitor discharges terminating the exposure
6
Q
- What is the minimum response time?
A
The time you must AT LEAST have to make the exposure. 1 millisecond.
7
Q
- What is a backup timer?
a. A safety device to protect the patient
b. A safety device to protect the radiation tech
c. A safety device to protect the x-ray tube
d. A safety device to protect the IR
A
c. A safety device to protect the x-ray tube
8
Q
- What type of MA does the Image Intensifier (II) use? Why?
A
Low (3-5) because we use a lot of TIME (it runs for minutes)
9
Q
- What is the size of the output phosphor?
A
1”
10
Q
- What is the size of the input phosphor?
A
6’’ or 9”
11
Q
- What kind of image can the Image Intensifier produce?
a. continuous
b. static
d. cine
e. all of the above
A
e. all of the above
12
Q
- What is the formula for total brightness gain?
A
Flux gain (consistent- he uses 50) times minification gain (size of input phosphor (6 or 9) squared)
Ex. 50x(9x9)= 50x81 = 4050 times brighter
13
Q
- Calculate the total brightness gain when using a 6” output phosphor.
A
50x (6x6)= 50x36= 1800 times brighter
14
Q
- Why must lead aprons be worn when doing fluoroscopy procedures?
A
Since it is continuous there is a lot of scatter from interactions with the patient.
15
Q
- Name 2 procedures that Image Intensification is used in.
A
Angiography, c cath, Barium studies, pain clinics, myelogram, hysterosalpingogram, cookie swallow, cystourethrogram
16
Q
- AEC helps eliminate repeats as long as what?
A
As long as the patient’s anatomy being x-rayed is over the activated cell.
17
Q
- What does a beam splitter do?
A
Allows us to record multiple image modalities (in II)
18
Q
- Of scotopic and photopic, which is rod and which is cones?
A
Scotopic is rods and photopic is cones.
19
Q
- Which was used in early fluoroscopy, scotopic or photopic?
A
Scotopic
20
Q
- What did the early fluoroscopists complain about constantly?
A
That the images were dull; that they needed a brighter image.
21
Q
- How did early flouroscopists remedy the dull images? What were the benefits?
A
The image intensifier- it used photopic. Photopic means fine detail, sharpness, high resolution, and the ability to work in a semi-lighted room.
22
Q
- Fluoroscopy is what kind of imaging?
A
DYNAMIC
23
Q
- Who was the great pioneer that invented fluoroscopy?
A
Thomas Edison
24
Q
- Put the parts of the I.I. in order, bottom to top, and match them with their function.
a. output phosphor w. converts light to electrons
b. input phosphor x. converts x-rays to light
c. photocathode y. converts electrons into light
d. electrostatic lenses z. accelerates electrons
A
b-x
c-w
d-z
a-y
25
25. Which component of the I.I. is cesium antimony?
Photocathode (input phosphor is cesium iodide)
26
26. Why can’t the cine camera, the spot-film camera, static, and recording on the monitor all be done at the same time?
They all require light
27
27. What are the two types of Digital Radiography (DR)? Which is better?
Indirect and Direct. Direct is better because it has fewer conversions (you lose signal with conversions; conversions hurt signal)
28
28. What is the difference between the two systems of Digital Radiography?
In Direct the remnant beams exit the patient and strike the system where they are converted to an electronic signal. The signal is stored in the TFT (Thin-Film Transistor) before being released into the ADC (Analog to Digital Converter) where it is converted into a number.
In Indirect the remnant beams exit the patient and strike the system- the x-ray hits a Scintilation Plate (SP) and converts x-ray to light beam. The light beam then hits a photodetector that changes the light beam into an electron beam. It is then sent to the TFT before being released to the ADC where is it converted to a number.
(Indirect requires two extra steps)
29
29. Why don’t you need a reader with DR?
Because it is hardwired to a system
30
30. In Direct DR, what material converts the remnant beam to an electronic signal?
Amorphous selenium
31
31. In DR, where is the signal stored?
TFT
32
32. What ratio is used in Detective Quantum Efficiency (DQE)?
Signal to noise ratio (S:N) where signal is useful info and noise is static interference
33
33. What kind of ratio would indicate a better image quality?
A higher ratio
34
34. What would you expect to see with a lower ratio? Why?
Quantum mottle because there is not enough signal.
35
35. What does lower ratio look like on the image?
A pitted, grainy appearance. This occurs with not enough x-ray.
36
36. What is an artifact?
Something that is there that shouldn’t be; an undesirable brightness.
37
37. What causes artifact?
Plates can crack, cassette-adhesive, hair or makeup on plate)
38
38. What does collimation do?
It increases contrast because it produces less scatter.
39
39. What is shuttering?
It is a post processing technique that creates a dark background around the image. It is aesthetic.
40
40. What is the exposure indicator?
A number that you get after making an exposure (Low= quantum mottle)
41
41. What is HIS and RIS?
Hospital Information System- strategically placed around hospital for those that need it. Easy access. Time saved. Dictated report available. Can compare images. Super-high resolution monitors can magnify.
Radiology Information System- where image is produced
42
42. How do we benefit from Tele Radiology?
We can take an image and convert it to a signal and send it around the world. Images sent electronically to various sites to be viewed/dictated/diagnosed and sent back. Can get second opinion. Some radiologists never see patients, just read films.
43
43. What is DiCom?
Digital Imaging and Communications in Medicine. Allows modalities from different vendors in different PACS to share information.
44
44. What are PACS?
Picture Archive Computer System- archive where we store electronic images.
45
45. Name two advantages of II.
Fine detail, sharpness, high resolution, and the ability to work in a semi-lighted room
46
46. What is the look-up table used for?
Adjust brightness and contrast
47
47. What is an AEC and what does it do?
Automatic exposure control- it terminates the x-ray exposure once we have a good image
48
48. What can go wrong with the AEC and cause it to not work?
If the activated cell is not under the anatomy being x-rayed then it won’t receive x-rays, so it won’t shut off, increasing exposure to the patient.
49
49. Which study looks at the spinal canal?
Myelogram
50
50. Which study looks for obstructions in the fallopian tubes?
Hysterosalpingogram
51
51. Which study looks for reflux from the bladder up the ureters?
Cystourethrogram
52
52. Which AEC has a light panel that absorbs x-rays and converts them to light?
Photomultiplier tube
53
53. Which AEC has a capacitor that discharges when it gets full?
Both
54
54. How do the AEC cells work?
They contain air. When the x-ray hits it, it frees electrons. The electrons then flow from the cell to the capacitor.
55
55. In an AEC, what causes the exposure to terminate?
The capacitor discharging.
56
56. When using an AEC, when may the back-up timer be activated?
If the wrong cell is used. It will run and run and run (since the call isn’t getting electrons because it isn’t under the anatomy being imaged) creating heat in the tube. The back-up timer will shut it down to prevent burning out the tube.
57
57. What are some advantages of AEC?
Consistent image production, lower repeats, decrease exposure, increase department efficiency
58
58. Fluoro produces real-time dynamic images. What does dynamic mean?
In motion
59
59. What is the name for radiographic images taken during fluoro that can be sent to PACS?
Spot films
60
60. Why is contrast media used in fluoro?
To increase differential absorption
61
61. This type of fluoro replaced early conventional fluoro.
Image intensified fluoroscopy
62
62. Fluoro has a high or low dose?
High due to time
63
63. Which has more recorded detail or spatial resolution; fluoro or radiography?
Radiography
64
64. Lower mA = ___________ signal and _________ brightness.
Lower; lower
65
65. Which has higher visual acuity - cone or rod?
Cone/ photopic
66
66. In daylight we use ____________ vision and ____________ at night.
Photopic; scotopic
67
67. What is the main source of occupational dose with fluoro?
Scatter from patient
68
68. What vision has best contrast acuity?
Photopic
69
69. Photoemission of II is similar to ____________of x-ray tube.
Thermionic emission
--But thermionic is release of electrons in response to heat and photoemission is releasing electrons in response to light.
70
70. The output phosphor is in the ___.
Anode
71
71. The convergence of the electrons in the II (Image Intensifier) is called the ___.
Focal point
72
72. What happens to the orientation of the image as it passes through the II?
It flips upside down at the focal point and is upside down at the output phosphor
