Lecture 23: Neuroradiology Flashcards
On CT the following appear: bone, gray matter, White matter, CSF, Fat, Muscle, Blood
bone = high intensity
gray matter = light grey
White matter = darker grey
CSF = Hypointense
Fat = very dark
Muscle = mid grey
blood = low-high intensity
Lesions are described by their?
Location, appearance and any other distinguishable feature
E.g. – Biconvex hyperintense lesion in the anterior cranial fossa extending to the midline causing mass effect compressing the frontal lobe and displacing the midline to the left.
Do we use contrast media to image the brain?
We use iodinated media for x-rays and CT and we use gadolinium based media for MRI. Does not normally cross the BBB unless there is an abnormality such as a stroke ot tumour.
Both are excreted by the kidneys so not good for renal failure patients.
Use of plain film radiograpy? (X-ray)
disadvantages
cheap, available, easy to perform
Cervical spine trauma, thoracic and lumbar spine degenerative disease, angiography with contrast
Useful for spinal osteoarthritis resulting in bony spurs or osteophytes as well as digital subtraction angiography for visualising blood vessels.
D = ionizing radiation, 2D, limited info, tends to be overused especially for skull examinations.
CT advantages, uses and disadvantages?
Fast (1-20min), relatively widely available, 3D reformatting and reconstruction, intermediate cost, can be used for density classification
USES: acute trauma, stroke to rule out bleeding, angiography with contrast media
D = high amounts of ionizing radiation and not cheap
Acute stroke management?
Use CT to rule out acute bleed
If non-haemorrhagic then we can give TPA (tissue plasminogen activator) or neuro-radiological intervention within 6h of stroke onset.
If blood is seen as bright signal on CT then TPA is withheld.
Differenced between epidural and subdural bleed?
Epidural bleed is a traumatic collection of blood between the inner aspect of the skull and the stripped off dura. Usually from trauma and bleeding from the middle meningial artery or middle cerebral artery. Lentiform in shape.
Subdural bleed is usually traumatic injury to veins between the dura and the arachnoid leads to collection of blood in the subdural space. Cresent in shape
Subarachnoid haemorrhage?
Bleeding into the subarachnoid space between the arachnoid and the pia
Blood is seen on the surface of the brain and in basal cisterns immediately after bleeding
Usually caused by aneurysms
MRI advantages and uses?
NO ionizing radiation, versatile, good for prenatal brain, contrast can be manipulated, multiplanar
Excellent for brain imaging, Acute ischemia demonstrated early with CT is normal, angiography with or without contrast
D - Can take up to 45 min and is very expensive and sensitive to movement. Saftey issues with it being a large magnet.
T1 and T2 weighted MRI scans?
T1 - CSF = Hypointense (dark) and Fat = hyperintense
T2 - CSF = Hyperintense (light) and Fat = usually hypointense
MRI and stroke diagnosis?
Within minutes of a stroke DWI (diffusion weighted imaging) signal is bright due to restriction of movement of water out of the cell caused by cytotoxic oedema.›
Which is a CT and why? Is the MRI T1 or T2
Left because of white bone
right is a T1 because of dark CSF
