Head and neck Flashcards
What are the benefits of CT comparing to MRI for cerebral imaging?
Much easier and safer to use in emergency situation – quicker
Limitations of CT comparing to MRI?
Demonstrates anatomy only
cant show full extent of lesions into soft tissue
What pathologies is CT gold standard for?
Technique of choice for:
Serious head injury
Suspected ICH
Stroke
Infection
Other acute neurological emergencies
Very high dose of ionising radiation
What are the benefits of MRI comparing to CT?
Demonstrates anatomy and physiology; good for brain function (fMRI)
What are the limitations of MRI comparing to CT?
Constraints:
Availability
Patient acceptability (claustrophobia)
Patient handling in an emergency situation
Metal!
Not great bone detail; cannot detect calcium e.g. in a tumour
What does contrast highlight in CT images?
evaluate:
vessels from their origin at the aortic arch to the intracranial portion
non-vascular neck structures and brain parenchyma
Detection of small lesions
Lesion characterisation – post contrast (“+C”) certain lesions will enhance and others won’t, e.g. brain tumour v abscess
Lesion extent – often difficult to image boundaries of lesion due to distortion from surrounding oedema/necrosis – contrast depicts true size, shape and position of lesions
MRA – excellent anatomical picture; accurate representation of the size of stenoses; short acquisition time
What are the limitations of PET/NM in imaging the brain?
Not currently a gold standard in brain imaging/functionality,
- normal functioning brain has residual FDG activity which ‘masks’/makes it difficult to identify most pathologies
How is PET/NM useful in imaging the brain?
useful in identifying ‘active/involved’ brain tissue prior to surgical treatment for epilepsy (ictal and post-ictal)
provides another level of certainty prior to the management/treatment of neurological oncology patients, e.g. PET/CT can assess the homogeneity of brain tumour metabolic activity/hypoxic volumes etc. prior to RTh
future new PET/CT tracers will be able to identify early dementia type pathologies in-line with future treatments
Future PET tracers will lead to other imaging avenues also
What imaging is used for a glioblastoma?
head
ct - without + with (common to have associated necrosis and oedema)
MRI - t2 + contrast (midline shift/mass effect)
PET/CT/MRI
What imaging is used for a Meningioma?
CT - with/without contrast
MRI - T1W
Head and neck:
brain and spinal cord
associated erosion of inner table of skull
Brain metastasis radiographic appearances?
round
well defined
multiple or singular
sometimes associated oedema
enhancement with contrast
What are the advantages of MRI comparing cT for imaging brain tumours/mets?
And what do they appear as with different weighting?
More sensitive than CT (for lesions <5mm; 2-3x more lesions demonstrated than CT +C)
T1-W = hypointense/isointense lesions
T2-W = lesions and oedema hyperintense
T1-W+C = lesions hyperintense; oedema hypointense
What are the potential referring/initial pathways for a cerebrovascular disease (stroke)?
referral via GP if mild
A/E - most commonly
although can go unnoticed:
In some cases, there may be a delay, e.g. elderly person living alone; event goes un-noticed
What is the imaging modalities can be used for a cerebrovascular disease (stroke)?
Immediate imaging:
CT
Later:
MRI
CTA/MRA
Conventional angiography
Carotid U/S
Echocardiography
Ba Swallow (+SALT)
interventional
Imaging pathway for a TIA?
CT Brain + Carotid Doppler U/S (looking for stenosis)
CTA/MRA - looking for blockage (plaque or thrombus or haemorrhage or aneurysm)
Imaging pathway for an Ischemic stroke?
Radiographic appearance?
CT:
identify areas of ischemia
non-con rules out haemorrhage - before anticoagulant treatment
MRI:
more sensitive
not suitable on initial presentation for unstable patients
MRA/CTA can confirm a suspected blood vessel occlusion
CT:
Acute sign: hyperdense middle cerebral artery (not common)
Subacute signs: wedge shaped area of hypodensity
MRI T2W:
Acutely, may show vascular enhancement
Subacutely, hyperdensity of cortex
Imaging pathway for an INTRA-CEREBRAL HAEMORRHAGE stroke?
Radiographic appearance?
CT first line - Fast scanning ASAP at least 48hrs;
CTA/MRA/DSA later
Rupture of cerebral blood vessel (usually artery)
Timing determines appearances:
blood hyperdense initially, but fades as time goes on (blood is reabsorbed)
Imaging pathway for an Subarachnoid HAEMORRHAGE stroke?
Radiographic appearance?
CT first line;
CTA/MRA/DSA later
Conventional angiography - interventional suite
Usually due to ruptured berry (saccular) aneurysm
High-density acute blood in subarachnoid spaces
Traumatic brain injury potential initial/referring pathway/
Medical emergency,
so usually via A&E - consequences can worsen swiftly without treatment, therefore need to assess the situation rapidly
Trauma so usually ambulance
TBI pathway:
Physical examination
Imaging:
Normally CT first line (possibly MRI when stabilised), to look for:
Haemorrhage (same as ICH, in stroke)
Haematoma (clot)
Contusion (bruise)
Brain tissue swelling
Specialist referral:
Observation (minor)
ICP monitor (severe)
What injuries can a CT diagnose in regards to a TBI?
CT in a comatose patient may reveal:
No abnormality (30%)
Haemorrhagic contusion (20%)
Extradural or subdural haematoma (20%)
Areas of oedema (10%)
A combination of the above (20%)