Midterm Flashcards
1
Q
What are four appearances of artifacts?
A
Ring
Band
Streak
Shading
2
Q
What is the start and end location for a CT routine chest?
A
Just above lung apices to Kidneys
3
Q
Name two patient induced artifacts in CT?
A
Motion & Metal & Out of field
4
Q
Name the two correction/remedy for ring artifacts in CT?
A
detector calibration
detector replacement
5
Q
The only CT procedures that you have learned that is scan in Axial is?
A
Head
6
Q
What is the definition of the term “slice” in relationship to CT?
A
One 360 degree rotation around the patient pieced together
7
Q
What is the CT number for bone?
A
400 to 1000
8
Q
What is the CT number for air?
A
-1000
9
Q
What is the CT number for water?
A
0
10
Q
What is the CT number for lung?
A
-200
11
Q
Name the four step process of a conventional CT scanner?
A
1- start; tube and detectors are accelerated to const. speed
2- x-ray tube energized data collected for 360 degree
3-stop; tube and detectors slow down & stop
4-table & patient indexed to the next scanning position
12
Q
What is the display field of view?
A
the area at which the tube is imaging
13
Q
What is another name for a conventional CT scanner?
A
Slice by Slice scanner
14
Q
Name two requirements for a Spiral/Helical CT unit
A
-Complete a full 360 degree rotation continually
-Table move through the gantry continuously
15
Q
What is a pixel?
A
a 2 dimensional area of an image
16
Q
What is a matrix?
A
rows and columns of pixels together
17
Q
What are two advantages of a multi-slice CT scanner?
A
-Faster scan time- easier with single breath for patient
-Better spatial resolution
18
Q
Name the three steps for formation of CT images by a CT scanner?
A
-Data acquisition
-Image resolution
-Image display
DII ARD FORM
19
Q
Spiral CT was made possible because of what new technology?
A
Slipring technology
20
Q
What are two important features of the gantry?
A
-Apperature
-Tilting of the gantry
21
Q
Who was the person who developed the mathematics used to reconstruct the CT images?
A
Radon/Cormack
22
Q
Name the generation scanner that used a rectilnear pencil beam?
A
1st gen
23
Q
Name the generation scanner that used spiral?
A
6th gen
24
Q
Name the generation that used rotate-rotate?
A
3rd gen
25
Name the generation that used translate rotate?
2nd gen
26
What is the purpose of the detectors?
To capture the beam to help create the image
27
Name the two types of collimators in a CT unit?
-Precollimator
-Predetector
28
What is the most significant development in radiology in the past 40 years?
CT
29
When does tomography trace back to?
1920's
30
What does a CT scanner do?
Looks at a specific layer or section of the body
31
Conventional Tomography uses what type of tomography?
Axial
32
Computed Tomography uses what type of tomography?
Transverse image
33
How many major design advancements has Ct gone through since 1970's?
5
34
What type of beam did the 1st generation CT scanner use?
pencil beam
35
How much did the 1st generation scanner rotate?
180 degrees
36
What kind of scan was the 2nd generation?
translate rotate
37
How much did the 2nd generation CT scanner rotate?
180 degrees
38
How many detectors did the 2nd generation CT scanner have?
5 to 30 detectors
39
What was special about the 2nd generation over the 1st generation?
It had a faster scan time
40
What kind of scan did the 3rd generation use?
Rotate-Rotate
41
What kind of beam did the 3rd generation use?
A fan beam of 30-60 degrees for full patient coverage
42
What happens in the 3rd generation if one detector fails?
A ring artifact appears
43
How much did the 3rd generation scanner rotate?
360 degrees
44
Why didn't the 4th generation CT scanner last long?
-Cost of detectors
-Too much scatter given off
45
How did the tube rotate in 4th generation scanners?
Rotates around a stationary ring of detectors
46
What type of beam was used in the 4th generation scanner?
Fan beam
47
How many detectors did the 4th generation use?
8,000 detectors
48
What is the 5th generation scanner used for?
Heartscan
49
What was special about the 5th generation scanner?
Allowed for continuous rotation of the tube for spiral
The continuous motion made no interscan delay b/c as the tube moves the table moves
50
What made Spiral CT possible?
Slipring technology
51
What is another name for 6th generation scanner?
Spiral CT
52
What were benefits of Spiral CT?
-Less motion artifacts
-Improved lesion detection because the reconstructed image can be at arbitrary intervals
-Reduced scan time
-Advances in computer processing allows for multi-planar reconstruction and even 3D reconstruction
53
What are basic CT scanner components?
-Gantry includes the pedestal or table, tube, collimators, detectors, and high voltage generator
-Operators Console
-Computer
54
What are the three steps of the formation of CT images by a CT scanner?
1- Display Acquisition
2- Image Reconstruction
3-Image Display
DII ARD FORMATION
55
What is image acquisition?
Refers to the collection of x-ray transmission measurements from the patient
56
How many layers of laser are on the gantry?
3 layers
57
What is the tilt range for the gantry?
+/- 12 to +/- 30 degrees
58
Table weight limits vary from ____ to ____ lbs.
300 ; 600
59
What is Slice by slice data acquistion?
Conventional CT, the tube rotates around the patient to collect data from a single slice of tissue, followed by table moving so that the next contiguous slice can be scanned
60
What are the four steps of Interscan delay?
1- Tube must be accelerated to constant speed of rotations
2- Tube produces x-rays that are transmitted through the patient to fall on the detectors
3- patient resumes breathing while the tube slows down and comes to a stop
4- Unwind the cable so another 360 degree slice can be scanned
61
Is interscan delay in Spiral CT?
No, the scan stops and the patient moves
62
What are limitations of interscan delay?
-Longer exam times
-Omission of certain portions of anatomy b/c patient respiration phase may not be consistent
-Inaccurate generation of 3D images and multiplanar reformatted images, also from inconsistent levels of inspiration
63
How does Spiral-Helical CT work?
The tube rotates continuously around the patient
64
Why is Spiral Ct called Spiral CT?
The geometry describes a spiral or winding
65
The geometry of Spiral-Helical CT also is called? Why?
Spiral-helical Volume CT; It defines a volume of tissue
66
What are requirements for Spiral-Helical CT?
-Continuously rotating scanner based on slip ring technology
-Continuous table movement
-Increase load ability of the x-ray tube
-Spiral-Helical Algorithm
-Mass memory buffer to store the vast amount of data collected
-Increased cooling capacity of the x-ray tube
-Slip rings replaced the high tension cables and allowed for the continuous rotation of the tube
-Volume scanning, Spiral Helical Scanning are the same
67
What are advantages of Spiral CT?
-Multiplanar reconstruction
-Shorter scan times
-Artifacts reduced
68
When was multislice CT scanners announced?
1998
69
What were multislice CT scanners capable of?
Imaging four slices simultaneously per x-ray tube rotation
70
At the present time, multislice scanner are available to image how many slices per x-ray tube rotation?
320
71
What are the advantages of multislice scanners?
-Shorter acquisition time
-Decreased amount of contrast medium
-Improved spatial resolution
-Improved image quality
72
What is Raw Data?
The signal data from all of the detector responses and contain the most information for image production
73
What is another name for Raw Data?
Scan Data
74
What is Image Data?
Reconstructed data; The result of raw data undergoing computer computations and filtered back projection to produce the image
75
What is a matrix?
Grid formed from rows and columns of pixels
76
What is a pixel?
Two dimensional square picture element utilized toe display a digital image
77
What is a voxel?
A 3D cube of anatomy
78
What is a CT number/ Hounsfield number?
The number assigned that is related to the linear attenuation coefficient of the tissue within each voxel of the image
79
What is the CT number for fat?
-80 to -120
80
What is SFOV?
Area within the gantry from which the raw data are acquired
81
What is DFOV?
Determines how much of the raw data are used to create and image
82
What is ROI?
A display function available on all scanners defining and area on the image
83
What is algorithm?
set of mathematical calculations and processes applied in image reconstruction
84
What is the linear attenuation coefficient?
Numeric expression of the decrease in radiation intensity that follows transmission through matter
85
What is slice?
Section of the object that is being scanned
86
What are slip rings?
Devices that transmit electrical energy and allow continuous rotation of the x-ray tube for volumetric acquisition
87
What is volume scanning?
Refers to the acquisition of a volume of CT data, the patient moves through the gantry with uninterrupted rotation and output of the x-ray tube
88
What are indications for Head CT without contrast?
-Intracranial hemorrhage
-Early infarction
-Dementia
-Hydrocephalus
-Cerebral trauma
-Headaches
-Seizure
89
What are indications for Head CT with contrast?
-Mass
-Lesion
-AVM
-Aneurysm
-Metastasis
90
What ae indications for Chest CT with contrast?
-Infection
-Mass
-Emphysema
-Evaluation of abnormalities discovered on chest radiographs
-Evaluation of know or suspected congenital thoracic anomalies
-Evaluation of trauma
91
What are indications for Abdomen and Pelvis CT with contrast?
-Suspected abdominal mass
-Tumor staging
-Abscess
-Infection
-Pelvic mass
-Hematuria
-Renal Mass
92
What are indications of Renal stone study without contrast?
Suspected renal or ureteral calculi
93
What are indications for Cervical Spine CT?
Fracture or Dislocation
94
What are indications for Lumbar Spine CT?
Fracture or Dislocation
95
What are the scouts for Head CT?
AP & Lateral
96
What is the scan type for Head CT?
Axial
97
Where is the start and end location for Head CT?
Just below skull base (C1-C2)
Just above vertex
98
What are the window settings for Head CT?
-Soft Tissue
-Bone
99
What reconstructions are made for Head CT?
Sagittal & Coronal
100
How does the patient go in for Head CT?
Head first
101
What scouts are done for Chest CT?
AP & Lateral
102
What is the scan type for Chest CT?
Helical
103
Where is the start and end location for Chest CT?
Just above lung apices
To top of kidneys
104
What are the window settings for Chest CT?
Soft Tissue & Lung
105
What reconstructions are made for Chest CT?
Sagittal & Coronal
106
How does the patient go for Chest CT?
Goes in feet first with arms over head
107
What scouts are done for Abdomen & Pelvis CT?
AP & Lateral
108
What is the scan type for abdomen & pelvis CT/
Helical
109
Where is the start and end location for abdomen and pelvis CT?
Just above Diaphragm
Just below Symphysis pubis
110
What Contrast is used for abdomen and pelvis CT?
Iv and Oral
111
What are the window settings for abdomen and pelvis CT?
Soft Tissue
Lung
Liver
112
What reconstructions are made for abdomen and pelvis CT?
Sagittal & Coronal
113
How does the patient go in for abdomen and pelvis CT?
Goes in feet first with arms over head
114
What scouts are done for renal stone studies?
Ap & Lateral
115
What scan type is renal stone studies?
Helical
116
Where is the start and end location for renal studies?
Just above diaphragm
Just below Symphysis Pubis
117
Why don't you use contrast for renal stone studies?
Both stones and contrast appear white; making it difficult to see a stone
118
What are the window settings for renal stone studies?
Soft Tissue
119
What reconstructions are made for renal stone studies?
Sagittal & Coronal
120
How does the patient go for renal stone studies?
feet first with arms over head
121
What scouts are done for Cervical Spine CT?
Ap & Lateral
122
What is the scan type for Cervical Spine CT?
Helical
123
Where is the start and end location for Cervical Spine CT?
Just below Skull base (C1-C2)
Middle of T2
124
What are the window settings for cervical spine ct?
Soft Tissue
Bone
125
What reconstructions are made for Cervical Spine CT?
Sagittal & Coronal
126
How does the patient go for Cervical Spine CT?
Head first
127
What scouts are done for Lumbar Spine CT?
AP & Lateral
128
What scan type is Lumbar Spine CT?
Helical
129
Where is the start and end location for Lumbar Spine CT?
T12
S1
130
What are the window settings for Lumbar Spine CT?
Soft Tissue
Bone
131
What reconstructions are made for Lumbar Spine CT?
Sagittal & Coronal
132
How does the patient go for Lumbar Spine CT?
Feet first
133
What is an artifact?
Any discrepancy between the CT numbers represented in the image and the expected CT number based on the linear attenuation coefficient
134
What are the 4 appearances of artifacts?
-Streaks
-Band
-Shading
-Rings
135
What are sources of artifacts?
-Patient
-Imaging Process and Equipment
136
What are patient induced artifacts?
-Motion
-Metal Artifacts
-Out of field artifacts
137
Motion artifacts are caused by?
Voluntary and Involuntary Motion
138
What is the remedy for voluntary motion? involuntary motion?
voluntary: explanation of procedure and good communication
involuntary: short scan time
139
How does metal artifacts manifest itself?
Start Streaking
140
What is the remedy for metal artifacts?
-Removal of external metallic objects
-Mar Software
-Gantry angulation
141
What is out of field artifact?
Patient is not entirely enclosed in the scanning field of view
142
What is the remedy for out of field artifacts?
-Selection of larger SFOV
-Taping patient tissue
-Raising patients arms above their head on the scan of chest and abdomen
143
What are equipment imaging process artifacts?
-Ring
-Line in Topogram
-Staircase
144
What is ring?
Malfunction of a detector in a third generation scanner
145
What are the remedies for ring?
-Detector calibration
-Detector replacement
146
What is Line in Topogram?
Bad detector causes continuous line on the topogram
147
What is the remedy for Line in Topogram?
Detector Replacement
148
What is staircase?
Improper selection of slice thickness and slice incrementation when generation MPR and 3D images
149
What is the remedy for staircase?
-Thin Slice use
-50% overlap on recon slice incrementation
