Imaging of CNS Flashcards
Why are skull x-rays largely eliminated?
CT now used instead
What is a skull x-ray important for?
Identifying calcification; eg: in some tumours
How does pneumoencephalography work?
Introduce air as negative contrast
Infer presence of masses by looking for distortions of ventricles
Is pneumoencephalography still used?
No
What form of catheter angiography is used today?
Digital subtraction angiography (DSA)
How does DSA work?
Initial x-ray without contrast and then subtract from all subsequent frames with contrast
How does a computer aided tomography (CT) scan work?
Fan of x-rays
Generated by x-ray tube
Transmitted photons received by row of detectors
Unit spins around patient while they’re moved through centre of unit
Reconstructed into cross-sectional images representing density
Where is ultrasound mainly used?
Neonates
What are the advantages of using ultrasound?
No radiation
Patient doesn’t have to be still
What is doppler ultrasound used for in adults?
Measure flow in middle cerebral arteries
How does magnetic resonance imaging (MRI) work?
Uses magnetic radiation to image hydrogen protons
Can use different sequences of magnetic pulses with different contrast between tissues
What property of the brain does fMRI depend on?
Autoregulation of blood flow in brain controlled very tightly
Allows precise imaging of active areas when presented with stimulus
What are two types of nuclear medicine?
Single positron emission computer tomography (SPECT)
Positron emission tomography (PET)
What can be labelled in PET?
Glucose
Other substances like amyloid
What does cortex look like on CT?
Grey matter and white matter have similar density
Need narrow window to distinguish them
Relatively noisy image
What is best for viewing the cortex: CT or MRI?
MRI, because it’s more sensitive than CT
Which MRI gives the most anatomical image of the brain?
T1
What can you identify with a T1 MRI?
Areas of cortical thickening
What are T2 MRI images better at outlining?
Areas of abnormal physiology
What do T2 MRI images identify?
Regions of brain with abnormal water content
What can cause an area to have abnormal water content?
Abnormal metabolism of normal cells
Abnormal cells
What is good at imaging ventricles?
T2 MRI
What can intracranial arteries be imaged with?
DSA
CT angiography (CTA)
MR angiography (MRA)
Transcranial ultrasound
What can intracranial veins and dural sinuses be imaged with?
DSA CT venography (CTV) MR venography (MRV)
