Image interpretation Book - physics, Head and spine Flashcards
Which is the correct order of tissue densities?
1. Air < fat < fluid < Soft tissue < Bone
2. Air < fat < soft tissue < fluid < bone
3. Air < fluid < soft tissue < fat < bone
4. Air < fluid < fat < soft tissue < bone
- Air< fat< fluid< Soft tissue < Bone
How many times more radiation do you get from a AXR compared to a CXR?
1. 0.3
2. 3
3. 30
4. 300
- 30
Is air bright or dark on US?
bright
What is the monro-kellie law?
The total volume of brain matter, CSF and intercranial blood must be constant
If one increases another must decrease
How does a plain CT head appear in very early ischemic stroke?
normal
What is an intercranial haemorrhage?
A bleed inside the skull
What are the types of intercranial haemorrage?
Intra- axial - within the brain itself
Extra - axial - between the brain and the skull
Which bleeds are intra-axial?
intraparencymal and intraventricular
Which bleeds are extra-axial?
Extradural, subdural and subarachnoid
What is a extracranial haemorrhage?
outside the skull eg soft tissue bruising or hematoma
What are signs of mass effect on brain tissue?
midline shift,
ventricular effacement - slit like ventricles
Sulci effacement - loss of definition of sulci
herniation
How does different stages of blood appear on CT?
Acute (hours to days) = white
Sub acute (days to weeks) = grey
Chronic (weeks to months) = old blood = dark
Acute on chronic creates a layering effect
what is an Extradural haemorrahge?
A bleed that lies between the skull and the dura matter
Arterial bleed
Lemon / lenticular shaped
What are common causes of extradural haemorrhages?
Head trauma - particularly to the pterion which tears the middle menigeal artery.
What is a sub-dural haemorrhage?
A bleed that lies between the dura matter and the arachnoid matter.
Venous bleed
Banana / crescent shaped
What are common causes of sub-dural haemorrhages?
Common in alcoholics and elderly who have cerebral atrophy. There is more strain on the veins which tear with minor trauma.
What is a subarachnoid haemorrhage?
Bleed in the subarachnoid space
resembles a spider web
What are common causes of sub-arachnoid haemorrhages?
can occur after trauma or patients with AVMs or berry anyrysms.
What symptom do patients complain of if they have a sub-arachnoid haemorrhage?
thunderclap headache
Blood in the subarachnoid space can cause meningeal irritation and shows similar symptoms to meningitis.
What is the appearance of a subarachnoid haemorrhage?
High density blood in the sulci, basal cisterns and fissures
It may also extend into the ventricles
What is an intraparenchymal haemorrhage?
Intracerebral bleeds are found within the brain matter itself.
What are common causes of intraparenchymal haemorrhage?
Hypertension, trauma or haemorrhagic stroke
what is the appearance of an intraparenchymal haemorrhage
Area of high density within the brain matter
What is an intraventricular haemorrhage?
Bleed within the ventricles - can be primary or secondary extending from a subarachnoid bleed
How does a intraventricular bleed appear?
Bright blood within the ventricles.
can be a CSF-blood level as denser blood sinks
Symptoms of Ischemic strokes:
what arteries are affected and what symptoms are associated with
TACS - total anterior circulation stroke
Anterior / middle cerebral artery
all 3 of:
higher dysfunction
hemiparesis
hemianopia (loss of visual field)
Symptoms of Ischemic strokes:
what arteries are affected and what symptoms are associated with
PACS - partial anterior circulation stroke
anterior / middle cerebral artery
any 2 of:
higher dysfunction
hemiparesis
hemianopia (loss of visual field)
Symptoms of Ischemic strokes:
what arteries are affected and what symptoms are associated with
POCS - posterior circulation stroke
posterior cerebral artery
any 1 of:
cerebellar symptoms
LOC
hemianopia
Symptoms of Ischemic strokes:
what arteries are affected and what symptoms are associated with
LACS - Lacunar stroke
small vessel disease
hemiparesis / hemiparaesthesia
What are the appearances of ischemic strokes on CT?
low density area - takes hours to develop
loss of differentiation of grey/white matter
sulcal effacement
bright MCA sign
old infarcts have lower density than acute
What are the appearances of ischemic strokes on MRI?
DWI best to detect - on DWI Infarct is bright area that develops within minutes
What are the appearances of brain tumors?
Appearances vary but they are usually heterogenous (non-uniform texture) solid lesions.
sometimes lesions aren’t seen but vasogenic oedema or other signs eg midline shift is seen
Tumors generally enhance with contrast
What is the most common differential diagnosis from appearance compared to a lesion?
brain abscess
What is small vessel disease?
Due to age atherosclerosis affects the small arterioles in our brains which supply the subcortical, periventricular and lacunar areas.
Those areas become ischemic and low density on CT.
It can lead to vascular dementia.
How does small vessel disease appear?
Generalised low attenuation of ischemic white matter.
associated with age related cerebral atrophy - signs = enlarged ventricles and widened sulci
What causes alzheimers?
Accumulation of amyloid plaques and neurofibrillary tangles
What are the signs of a venous sinus thrombosis?
Headaches and neurological signs.
most occurring in people with prethrombotic risk factors.
It can progress to a cerebral infarct and secondary haemorrhage.
How does venous sinus thrombosis appear?
On a CT venogram -filling defect within a contrast enhanced venous sinus.
known as an empty delta sign
How do cerebral aneurisms appear?
localised dilatation along a cerebral vessel
What are the types of skull fractures?
- linear ( uncomplicated)
- Depressed (pushed in)
- Diastatic ( suture widening)
- Basilar (Base of skull)
What are the signs of a basilar skull fracture?
Bruising around the eyes (racoon eyes) and the mastoid processes ( battle sign) and CSF leakage from nose (rhinorrhoea) and ears (otorrhoea)
What is important when looking for skull fractures?
They can be confused for sutures so its important to follow the line to see if it runs in a suture line
What causes vertebral compression fractures?
Trauma or pathological reason
eg osteoporosis, lytic mets
How do spinal compression fractures appear on imaging?
X-Ray/ CT - looking for a cortical break and loss of height
MR - oedema of the bone (bright on T2)
NM bone scan - high uptake
What are the common causes of spinal cord compression?
vertebral fractures, disc prolapse, mass or lesion
How does spinal cord compression appear?
Bright edematous areas within dark cord on T2
Bright CSF signals surrounding the cord is lost
what is the name of the spinal cord at the level of L1/2 and below?
L1/2 = conus medullaris
Below = cauda equina
What is MS?
How is MS diagnosed?
multiple sclerosis - a chronic demyelinating disease of the CNS (brain + spine).
No definitive tests but MRI and CSF analysis are used
How does MS appear on imaging?
Bright plaques on MR (T2 or FLAIR)
Finger like appearance around the ventricles in sagittal view.
plaques can be found in the cerebellum, brainstem and spinal cord.
Plaques enhance with contrast - indicates current disease activity
