Lecture 39 Neuroradiology Flashcards
List indications to perform a CT scan
Head trauma
Acute stroke
Headache
Cancer: looking for metastatic brain tumours in patients with symptoms
Post-surgical: hydrocephalus, haemorrhage
Contraindications of a CT scan
Minor head trauma: is GCS 15, no suspected open or depressed skull fracture, no haemotympanum, no ‘panda’ eyes, no CSF leakage from ears or nose, no post-traumatic seizure, no focal neurological deficit, <2 episodes of vomiting, no amnesia, age < 65 years, no coagulopathy, not struck by a motor vehicle, not ejected from a motor vehicle, fall < 1m
Seizure
List indications to perform an MRI scan for a neurologist
- Demyelination: for example, to help diagnose multiple sclerosis
- Epilepsy: NICE and SIGN guidelines (and if surgery is contemplated)
- Paediatric neurology: disorders of development, head circumference, congenital malformations
- Headache: benign intracranial hypertension
List indications to perform an MRI scan for a surgeon
- Spine: Intervertebral disc degeneration causing neural compression
- Cancer: clarifying the number, location and aggressiveness of brain tumours
State contraindications to perform an MRI scan
- Implanted electronics (check with manufacturer):
- Cardiac pacemakers, implantable defibrillators, cochlear implants
- Relative contraindication for programmable shunts, insulin pumps
- Moveable metallic implants (check make and model):
- Aneurysm clips, heart valves, recent intra-abdominal clips
- Claustrophobia, pregnancy, tattoos
What are the uses of angiography in the diagnosis of neurological pathology
Large vascular (arterial and venous) abnormalities Diagnosis and treatment 1. Aneurysm 2. Arteriovenous malformation 3. Carotidocavernous fistula 4. Unstoppable epistaxis
Understand the uses of CT perfusion
Perfusion is defined as the volume of blood passing through a defined volume of tissue per unit time
• Units: ml blood / 100g tissue / min
• Can be a CT or MRI technique
Disorders of abnormal perfusion
• Stroke – decreased perfusion
• Tumour – increased perfusion indicates angiogenesis and a more aggressive tumour
Not commonly used
What is the use of a PET scan
PET is usually used to map out glucose usage
Increased metabolism is seen in
• Tumour
• Inflammation
• Infection
Useful after brain tumour resection for differentiating granulation tissue (low energy usage) from leftover tumour (high energy usage).
How would you identify a plain radiograph
- Multiple superimposed bones, bones are white
- Immediately recognisable body parts
- Soft tissue is grey
- Air is black
How would you recognise a CT scan
• White circle of skull
• Black CSF in sulci and ventricles. Air is black.
• Grey brain with subtle grey-white matter difference
• Image quality:
reconstructed by back projection from a rotating fan beam of X-rays
beam hardening from radiodense objects
• Metal produces white starbust artefacts – slightly grainy
How would you recognise an MRI
• White CSF is the best clue, but only true for T2weighted MRI
Same anatomy with different sequences often shown
• Better grey-white matter differentiation than CT
• Image quality:
reconstructed from Fourier transforms of radio signals
has a JPEG-like quality, usually not grainy
How wold you recognise a Radionuclide radiology / nuclear medicine / PET scan
- Images often have bright and varied colours
* The image is fuzzy
How would you recognise an Ultrasound
- Wedge-shaped image with the edges of the image diverging away from top to bottom
- Often has a curve at the top matching the ultrasound probe (exception: flat probes)
- Very noisy image (like an old un-tuned TV)
- Objects which block the ultrasound beam (air, bone, stones) cast shadows cast downwards
Advantages of US
- No radiation
- Less expensive equipment
- Can be performed in neonatal unit
- Movement tolerant
Disadvantages of US
- Requires wide enough open fontanelle up to about 1.5 years
- Image quality and interpretation based on operator skill
