1
Q
What is the most common CT scan performed?
A
Head CT
2
Q
T/F
The head is placed in a head holder for most CT protocols
A
True
3
Q
How is radiation exposure to the lens of the eyes reduced?
A
Align the supraorbital meatal line
*or glabella meatal line
4
Q
Why is scanning the posterior fossa of the brain a challenge?
A
Beam hardening artifacts
5
Q
How are beam hardening artifact reduced when scanning the posterior fossa of the brain?
A
Increase kvp
Decrease slice thickness
6
Q
T/F
Head CT scans are acquired with thin slices
A
True
7
Q
Why is a head holder not used for trauma patients?
A
They will go in head first
*also most likely in a collar
8
Q
What artifacts occur because of great tissue differences in the posterior fossa?
A
Beam hardening
Streak
9
Q
T/F
Every head scan will have artifacts in the posterior portion
A
True
10
Q
160ww/40wl
A
Soft tissue (brain)
*posterior fossa
11
Q
100ww/30wl
A
Soft tissue (brain)
*above posterior fossa
12
Q
2500ww/400wl
A
Bone
13
Q
200ww/60wl
A
Blood
14
Q
Why is a narrow window width used for the brain?
A
Small difference between white and grey matter
15
Q
35-45 HU
A
Grey matter attenuation
16
Q
20-30 HU
A
White matter attenuation
17
Q
40-50 HU
A
Circulating blood
18
Q
60-110 HU
A
Clotted blood
19
Q
4-8 HU
A
Cerebral spinal fluid
*just above water
20
Q
ICH
A
Intracranial hemorrhage
21
Q
T/F
CT is mostly used for the initial examination for intracranial hemorrhage
A
True
appearance of ICH will change over time
22
Q
If a person has a severe headache, what pathology might be suspected?
A
Subarachnoid hemorrhage
23
Q
How long does and ICH appear hyper dense (white) to normal tissue?
A
For approximately 3 days
*gradually decreases in density
24
Q
Where does the density of an ICH change first?
A
Density Decreases at the periphery first
*progressive density loss until fully hypodense (black) to brain tissue
25
26
ICH appearance
White
Onset to 3 days
27
ICH appearance
Hyper dense centre surrounded by concentric areas of hyper dense and hypodense tissue
4 to 10 days
28
ICH appearance
Isodense centre surrounded by areas of hypodense tissue
11 days to 6 months
29
ICH appearance
Hypodense to brain tissue
6 months
30
T/F
If a bleed is seen on an unenhanced CT head, a CT COW- carotid may be perfomed
True
31
-Hemorrhage above the dura
-radiographically shows **football sign**
-midline shift
Epidural hemorrhage
*blood between skull and dura
32
-Hemorrhage between dura and membrane of brain
-appears as a crescent
Subdural hemorrhage
*dura still attached to skull
33
-bleeding in the subarachnoid space
-usually caused by a rupture of an aneurysm
Subarachnoid hemorrhage
**star of death - high mortality
34
-3rd most frequent cause of death in North America
-leading cause of long term disability
Cerebrovascular disease
35
T/F
Thrombolytic therapy can be given for cerebrovasular disease to limit the extent of injury
True
*only effective in a small time frame
*imaging is very crucial in this period
36
T/F
The location of the stroke and the extent of the ischemic lesion, with the blood flow reduction will predict the outcome of the treatment of stroke
True
*assessment of cerebral blood circulation is necessary to determine whether a conservative or more aggressive therapy is needed in the early stage of a stroke
37
What percent of our body’s O2 is provided to the brain for a healthy and functional brain?
25%
38
What are the 2 main arterial systems that provide oxygen rich blood to the brain?
-carotid arteries
-basilar arteries formed by vertebral arteries
*connected to form the circle of Willis (COW)
39
Loop around the brainstem giving off major vessels supplying the brain
COW
40
T/F
Neurological deficits occur within an hour of a stroke
True
41
-clot forms as a result of atherosclerosis
-rigid arteries formed the clot
Thrombolytic stroke
*from fat, cholesterol…
42
-sudden blockage of artery by an embolus
-travels within the arteries and becomes lodged
-> decreased blood flow -> stroke
Embolic stroke
*other formations of clots
43
-tiny blood vessels branching off the main COW, can become occluded and cause tiny ischemic strokes
Lacunar stroke
44
-tangles of arteries and arterialized veins
-blood goes directly from arteries to veins
-high pressure in veins can cause vessels to rupture
-> hemorrhagic stroke
Arteriovenous malformation
45
What are major symptoms of stroke?
-unilateral weakness
-loss of feeling of the face, arm, leg
-aphasia (loss of verbalization)
-seizures, or coma
-hemorrhagic stroke: severe headache
46
tpA
Tissue plasminogen activator
47
What is the diagnosis and treatment of stroke?
-tpA administered within 3 hours of first sign of stroke
-importance of imaging and diagnoses on time
-reperfusion is possible (circulation can occur)
**tpA comes with high risk of hemorrhage**
48
Why is a patients head placed in a holder?
-helps immobilize head
-cradle extends beyond the tabletop, minimizing artifacts
49
What are the most important imaging planes for head scanning?
Axial
Coronal
50
-gives details of the foramina, facial structures, pituitary fossa, temporal bones
-CSF in the basal cistern and ventricles
-calcium in the choroid plexus, pineal gland falx cerebri
-definition of grey and white matter
Axial imaging plane
51
-useful for assessing bone when the plane of the bone runs parallel to the axial slice
-valuable for floor and roof of the orbit, base of skull, top of cranium vault, pituitary gland, sinuses
-ossicle and structures of the middle ear of temporal bones
Coronal Imaging plane
52
Not routinely used and seldom provided any significant information that can’t be obtained on good coronal and axials
Sagittal imaging plane
53
Collection of skin cells
Cholesteatoma
54
T/F
Multi detector CT and post processing techniques are one of the most used tools for investigating cerebrovascular disease of the head and neck
True
*other modality used is angiography and DSA. It has high spatial resolution but is time consuming
55
Why are CTA head and neck scans done?
-acute stroke
-brain perfusion studies to assess viability of parenchyma
-describe spatial relationship of organs and vessels for surgeons
56
What are the goals of CT head and neck?
-measure stenosis of carotid and vertebral arteries
-evaluate circle of Willis using reformats
-detect other vascular lesions such as dissection of occlusions
*CTV can also be done, but with bolus reaching the venous phase
57
Used for the depiction of vein anatomy
CTV
58
How is a CTA/CTV protocol performed?
CTA scanned and CTV scanned immediately after
59
T/F
CT brain perfusion studies allows for qualitative and quantitative evaluation of cerebral perfusion
True
*done by calculating regional cerebral blood flow (rCBF) and volume (rCBV) and mean transit time (MTT)
**Cerebral blood flow = CBV/MTT**
60
T/F
CT brain perfusion post processing is done by selecting reference artery and vein
True
61
How is a reference artery chosen for CT brain perfusion?
Should be:
-one of the first to enhance
-high enhancement peak
-curve with narrow width
62
How is a reference vein chosen for a CT brain perfusion?
Choose vein that produces the highest peak
63
What is the most common reference artery selected for CT brain perfusion?
Anterior cerebral artery
64
What is the most common vein chosen for CT brain perfusion that produces the highest peak?
Superior Sagittal sinus vein
65
What artifacts could be present when scanning for neck protocols?
Teeth
Shoulders
66
Why is a modified valsalva maneuver used for neck protocols? ( blowing out cheeks)
To distend the purified sinuses
67
What is the ROI for neck scanning?
Supraorbital margin to aortic arch
68
Why is contrast used for neck scanning?
To enhance mucosa, lymph nodes, pathologic tissues
*images acquired while the vasculature remains opacified
69
What happens if contrast is injected too early when performing neck scanning?
Leads to tissues being unenhanced
*inflammation and neoplasms can go undetected
70
What happens if contrast is injected too late when performing neck scanning?
Vascularity is not enhanced
*solution = split bolus
71
T/F
CT produces images of the spine with inherent soft tissue contrast
True
72
What is the typical axial slice thickness that studies of the head are routinely acquired in?
1.25mm
CT 2
flashcards
Decks in class (23)
# Cards
-
Patient Preperation22
-
Contrast Media65
-
Automated Injection Devices33
-
Tissue Enhancement56
-
Contrast Phases14
-
Abdomen-Pelvis Anatomy69
-
Abdomen Pelvis Protocols35
-
Protocols28
-
MSK Scanning39
-
Special Procedures63
-
Neuro Protocols72
-
Neuro Indications37
-
Scan Parameters12
-
Neuro - Contrast10
-
DFOV - Neuro10
-
Window Setting - Neuro10
-
Attenuation - Neuro8
-
Reformats - Neuro3
-
Thoracic Anatomy82
-
Thoracic Protocols70
-
Thoracic Indications10
-
Thoracic Scan Parameters15
-
Thoracic Contrast8
