Final Exam Flashcards
What is the first scan that is done following the presentation of symptoms of a stroke?
Non contrast CT
Why should we not start the examination of a stroke protocol with contrast?
- Don’t want to miss/mask a bleed
- We want to determine if it is an ischemic or hemorrhagic stroke
What vessel does CTA access?
The arteries
What are the advantages of preforming a CTA of the head following symptoms of a stroke?
-Non-invasive
-Quick
-Widely available.
(The time saving nature of CTA is an advantage in the case of patients suspected of suffering from an acute stroke in which treatment decisions must be made quickly.)
What is the goal of CTA?
- To accurately measure the stenosis of carotid and vertebral arteries and their branches.
- To evaluate the structure of the Circle of Willis
- To detect other vascular issues, such as occlusions or dissections.
What is the purpose of performing a CT Perfusion following the presentation of symptoms of a stroke?
Allows quantitative evaluation and assessment of regional cerebral perfusion. With a CT perfusion study, we can determine where the core and penumbra is.
How does infarcted tissue appear on a perfusion study?
-Decrease in cerebral blood flow
-Decrease in cerebral blood volume
-Increase in time to peak
-Increase in mean transit time
Tissues that match the above parameters are not viable, even if reperfusion is attempted.
How does penumbral tissue appear on a perfusion study?
-Decease in CBF
-Cerebral blood volume is normal or higher
-Increase in time to peak TTP
-Increase in mean transit time
Tissue that matches the above parameters are viable; salvageable if normal CBF is returned.
What pathologies in the head and neck of a patient can result in neurological deficits?
-Strokes/CVA
-Trauma (mass effects, bleed)
-Intracranial hemorrhage
-Brain tumours/mass/lesions/metastasis
-Abscess
-Meningitis
(cerebrovascular disorders)
What are the commonly selected regions for ROI placement following acquisition of CTP images of the head? Why?
-The anterior cerebral artery is commonly used to obtain arterial ROI because it travels along the axial plane, and is easy to locate.
-The superior sagittal sinus is usually used to obtain the venous ROI.
What is the window width?
1000
What is the window level?
0
What is the window width?
300
-Right=150
-Left=150
-150+150=300 WW
What is the window level?
WL=200
What is the window width?
WW=300
150+150
What is the window level?
0
What does the window width determine?
Determines the number of Hounsfield units (CT numbers) represented in an image
What is window level?
The center CT value of the assigned window width.
What window settings are seen in images A and B?
A=Lung window
B=Mediastinal window
Can’t get a complete picture without seeing these two window
What structures are seen well with a lung window? What are the limitations?
-Detail of the lung parenchyma seen
-Limitations=can’t appreciate mediastinal structures
What structures are seen well with a mediastinal window? What are the limitations?
-Clearer picture of the mediastinal structures
-Limitations=Don’t see a lot of the lung detail
What are the two types of reconstructions?
1.Retrospective
2.Prospective
Define reconstruction:
Used when raw data is manipulated to create an image.
Define reformation:
Used when image data are assembled to produce images in different planes, or to produce 3D images.