Neuroradiology Flashcards
What are common indications for head CT scan?
- Head trauma
- NICE guidelines
- Acute stroke
- NICE guidelines
- Headache
- SIGN guidelines, red flags for suspected tumour or subarachnoid haemorrhage
- Cancer
- Looking for metastatic brain tumours in patients with symptoms
- Post-surgical
- Hydrocephalus, haemorrhage
What are contraindications for head CT scan?
For head trauma follow NICE and SIGN guidelines:
- Such as GCS score of 15, no suspected open or depressed skull fracture, no CSF leakage from ears or nose, no post-traumatic seizure etc
NICE guidelines for seizure usually suggest MRI:
- Primary idiopathic generalised epilepsy
- No imaging
What are indications to perform MRI scan?
- Neurologists
- Demyelination
- Such as to help diagnose MS
- Epilepsy
- NICE and SIGN guidelines (and if surgery is contemplated)
- Paediatric neurology
- Disorders of development, head circumference, congenital malformation
- Headache
- Benign intracranial hypertension
- Demyelination
- Surgeons
- Spine
- Intervertebral disc degeneration causing neural compression
- Cancer
- Clarifying the number, location and aggressiveness of brain tumours
- Spine
What are contraindications to performing 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
Relative contraindications:
- Claustrophobia, pregnancy, tattoos
When is angiography used in neurology?
Large vascular (arterial and venous) abnormalities
Diagnosis and treatment of:
- Aneurysm
- Arteriovenous malformation
- Carotidocavernous fistula
- Unstoppable epistaxis
What is perfusion?
Volume of blood passing through a defined volume of tissue per unit of time
What are the units of perfusion?
Units are ml blood, 100g tissue or per minute
Is perfusion measured using CT or MRI?
Either, you get CT perfusion or MRI perfusion
What are some disorders of abnormal perfusion?
- Stroke
- Decreased perfusion
- Tumour
- Increased perfusion indicates angiogenesis and a more aggressive tumour
Is the perfusion in a stroke increased or decreased?
Decreased
Is the perfusion in a tumour increased or decreased?
Increased perfusion (indicates angiogenesis and a more aggressive tumour)
What are PET scans used for?
Usually used to map out glucose usage
Increased metabolism of glucose is seen in what?
- Tumour
- Inflammation
- Infection
Why are PET scans useful after brain tumour resection?
Differentiating granulation tissue (low energy use) from leftover tumour (high energy use)
What are clues for identifying that an image is a plain radiograph?
- Multiple superimposed bones, bones are white
- Immediately recognisable body parts
- Soft tissue is grey
- Air is black
What colour is air in a x-ray?
Black
What colour is soft tissue in a x-ray?
Grey
What are clues for indentifying an image is 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
What colour is the skull in a CT scan?
White
What colour is CSF in a CT scan?
Black
What colour is air in a CT scan?
Black
What colour is the brain in a CT scan?
Grey with subtle grey white matter differences
What are clues an image is a MRI scan?
- White CSF is the best clue (but only true for T2 weighted MRI)
- Same anatomy with different sequencing 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
What colour is CSF in a MRI scan?
White
What are clues an image is a radionuclide radiology/nuclear medicine/PET image?
- Images often have bright and varied colours
- The image is fuzzy
What are clues an image is 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 is flat probes)
- Very noisy image (like an old un-tuned TV)
- Objects which block the ultrasound beam (air, bone, stones) cast shadows downwards
What are some examples of important neurological emergencies?
- Trauma
- Acute stroke
- Cauda equine compression
- Subarachnoid haemorrhage
What is helpful when discussing neuroradiology referrals?
- For stroke
- Know about carotid arteries, cardiovascular risk and atrial fibrillation as well as functionally important areas of the brain
- Be able to differentiate upper motor neuron from lower motor neurone
- For cauda equine syndrome or intervertebral disk herniations you should be able to link reflexes and dermatomes to approximate spinal levels and be able to number vertebrae
What are advantages and disadvantages of US?
- Advantages
- No radiation
- Less expensive equipment
- Can be performed in the neonatal unit
- Movement tolerant
- Disadvantages
- Requires a wide enough fontanelle (ie about up to 1 year of age)
- Image quality and interpretation based on operator skill
What are advantages and disadvantages of plain radiographs?
- Advantages
- Almost universally available
- Fast
- Sequential images in subtraction angiography
- Disadvantages
- Lacks soft tissue detail
What are advantages and disadvantages of CT?
- Advantages
- Rapid
- Metal and pacemaker tolerance
- Good for demonstrating acute haemorrhage
- Disadvantages
- Radiation 2mSv
- More expensive cumbersome equipment
What are advantages and disadvantages of radionuclide radiology?
- Advantages
- Physiological information
- Glucose metabolism
- Perfusion
- Dopamine reuptake receptors
- Physiological information
- Disadvantages
- Unclear anatomical information
- Medium cost of equipment
- Radiotracers can be expensive
What are advantages and disadvantages of MRI?
- Advantages
- No radiation
- Soft tissue differentiation
- Physiological information
- Blood flow
- Diffusion restriction
- Metabolite concentrations
- Disadvantages
- Poor tolerance of metalwork
- Magnetic sensitive electronics may fail ore are contraindicated
- Pacemakers
- Cochlear implants absolutely contraindicated
- Least movement tolerance
- Slow, must limit sequence
- Most expensive equipment
Danger of metallic objects becoming projectiles
