Lecture 23: Neuroradiology Flashcards
What type of scan is this?
How do you know?
CT Scan
On CT:
Bone is very bright (high intensity)
Gray matter (light grey)
White matter (darker grey)
CSF (hypointense)
Fat (very dark)
Muscle (mid grey)
Blood (low-high intensity)
Which side is the lesion?
Why is it important to know which side the lesion is?
(the patient is going unconscious)
Right-frontal side (the patient is left is always on your right)
Need to know which side of skull to open at surgery.
Describe the lesion, location , appearance and other features
There is a bionvex (shape), hyperintense lesion in the antieror cranial fossa extending to the midline.
It’s causing a mass effect, _compressing the frontal lob_e and displacing the midline to the left.
What do you see on this chest X-Ray?
Always look around the edges of the film
The person has a missing scapula (and have tumours in the lungs)
What is intravascular contrast media?
Compounds injected to increase the contrast of structures or fluids on imaging
Usually do not cross the blood brain barrier unless therr it is not intact.
So areas of pathology such as tumour or stroke have ‘leakly’ vessles. The contrast agent enters the abnormal tissue and wash out is slow. It is thus is visualised on scanning as high signal
Both iodinated and gadolinium based media are associated with poor outcomes when used in renal failure as there are excreted via kidneys
Briefly describe Plain film radiography (X-Ray)
High energy X-rays pass through the body towards a photographic plate with an x-ray sensitive (silver bromide) film
Higher density structures such as bone stop/absnorb more of the xrays than low density tissue
X-rays that pass through the body strike the sliver bromide coat on an x-ray film and form stable silver. These will appear darker on the film
What are the advantages, uses and disadvantages of plain film radiopgraphy?
Advantages:
1) Cheap, 2) widely available and 3) easy to perform.
Uses:
1) Cervical spine trauma
2) Thraocic and lumbar spine degerenative disease
3) Angiography with contrast media +/- fluoroscopy
Disadvantages
1) Uses ionizing radiation (can cause cancer)
2) 2D so need 2 views to locate lesions
3) Infomration is limited
Tends to be over used especially for head trauma as there can be signifcant brain trauma without a skull fracture. Also fracture is very unlikely if the skin is not breached.
What should you look for in a X-ray of the neck?
1) Check alignment of anterior border of vertebral bodies (red)
2) Check alignment of Spinolaminar line (green)
3) Facet joints must be parallel
4) Check space between the discs
If you find abnormality, do a CT scan.
Diagnose
Spinal osteoarthritis
(results in bony spurs or osteophytes)
Describe Digital subtraction angiograpy (xray)
Take 1 image and take another image and subtract the 2 to get image of the vessels.
What are the Advantages, Uses and Disadvantages of CT scans?
Advantages
1) Fast 1-20 mins
2) relatively widely available
3) 3D reformatting and recnostruction possible
4) Intermediate cost
Uses
1) Acute trauma
2) Stroke to rule out bleed
3) Angiography with contrast media
Disadvantages
1) Use of radiation
2) Not cheap
Describe Acute Stroke Management
1) To Rule out acute bleed
- If a non haemorrhagic, stroke can be treated with tissue plasminogen activator (TPA) or neuro-oradiological intervention (clot removal) within 6 hours of stroke onset, the outcome is improved
- If haemorrhagic (blood seen as bright signal on CT), TPA is withehld as will likely cause more haemorrhage
How do CT scans work?
The CT anode produces a narrow continuous fan shaped stream of x-rays as it rotates around the head, paired with a detector at 180 degrees to the anode
The image is reconstructed using a number of algorithms,
What is this?
Early ischemic stroke
- look for blood leakage
1) Early signs of ischemia on CT: loss of definition between grey and white matter
2) Ill defined internal capsule
3) Hyperdense middle cerebral artery (not always seen)
If no blood- TPA or do an MRI
What is the difference between epidural and subdural bleed?
Epidural Bleed:
- Traumatic collection of blood between the i_nner aspect of the skull_ and the stripped off Dura
- Cuase is usually trauma and bleeding from the middle miningeal atery.
- Leniform in shape
Subdural Bleed:
- Usually tr_aumatic injury to veins_ between the d_ura mater_ and the arachnoid leads to collection of blood in s_ubdural space_
- Crescent in shape.
Diagnose the left picture
Acute Epidural Haemorrhage
Traumatic collection of blood between the inner aspect of the skull and the stripped off Dura
Cuase is usually trauma and bleeding from the middle miningeal atery.
Leniform in shape
Diagnose the right picture
Chronic Subdural bleed
Usually traumatic injury to veins between the dura mater and the arachnoid leads to collection of blood in subdural space
Crescent in shape.
Diagnose
(CT Scan)
- Subarachnoid haemorrhage
- Bleeding into the subarachnoid space between the arachnoid and pia
- Blood is seen on surface of brain and in basal cisterns immediately after bleed
- Ususally aneurysms cause subarachnoid haemorrhage. (Often results from hypertension and rupture of aneurysms of the cerebral vessels)
- High risk of re-bleed if aneurysm
What are the advantages, uses and disadvantages of MRI (magnetic resonance imaging)?
Advantages
1) No ionizing radiation
2) Great for brain imaging
3) Verstaile with mutiple modes/sequence types
4) Good for prenatnal brain
5) Tumours
Disadvantages
1) Long acquisition time 10-120 mins
2) Poorer access
3) Expensive
4) Motion sensitive
5) Safety issues- cochlea implants and joint replacements.
Describe the princicples of MRI
- Body is placed in a powerful magnetic field 40-60,000x earth’s magnetic field
- Some of the protein nuclei align themselves with the direction of the field. They act as if they are tiny bar magnets
- A radifrequency pulse is applied perpendicular to the main field, which flips the direction of the aligned nuclei
- 2 Basic types of MRI sequences are T1 weighted and T2 weighted.
- On T1 CSF, is hypointense and fat is hyperintense (eyeball is dark)
- On T2 CSF is hyperintense and fat is usually hypointese (eyeball is bright)
Is this T1 or T2 MRI scan?
T2- CSF is hperintensive
Describe the FMRI for surgical planning
Functional MRI
Reconstruction from MR imaging and functional activation (O2 consumption)
Demonstrates location of tumour as well as relation to cortex responsible for hand and foot control
Which is a CT scan and why?
Left: CT (white bone)
MRI (T1)
CT vs MRI which is better
1) Stroke imaging
2) Tumour
3) Bone re-construction
4) Angiography
5) Spine imaging
1) MRI
2) MRI
3) CT
4) CT (but massive radio-exposure)
5) MRI
