Imaging Flashcards
Cerebral ischemia Early signs on CT?
Hyperdense artery sign
insular ribbon sign
Loss of lentiform
nucleussulcal effacement
Easpects
Automated CT reader
Issue of CT scan passing the limit sensitivity remains
How unprofessional can spot stroke
Speech problem
Visual problem
Muscle weakness
How to professionally identify stroke
Imaging! Ischemic stroke -> Secluded artery leading to less blood -> change in tissue density -> less visual/recognised in imaging Look for signs (celebral ischemia): 1. Hyperdense artery sign Loss of caudate nucleus 2. Loss of lentiform nucleus (triangle) 3. Loss of insula cortex/ insular ribbon sign 4. Sulcal effacement (loss of sulcus)
Difficulty of analysing stroke in imaging
-ASPECTS (automated scores for consistency)
Analyse the brain by breaking it into 10 different parts
White cotton -> haemorrhage (rupture)
-By the time you can see it, probably too late
-Use of MRI imaging in addition to CT
Neuroradiology enabling stroke treatment
Ischemic貧血 or haemorrhage出血?
If it is not haemorrhage,
identify damage, show hypoperfusion, quantify collaterals and visualize pathway/access for clot removal
Neuroradiology assess time window for stroke
use tissue clock for the 12 -18 % stroke victims with unknown symptom onset; better if shown up within 1.5h (later you treat, more risk of haemorrhage)
Neuroradiology illustrate pathophysiology
perfusion imaging with Time Shift Analysis
O2 extraction fraction
pH imaging
Physics behind DWI
(cats stroke study)
below 12ml/100mg/min blood flow, cells die as detected as increased water content. Increase in water content, decrease x-ray density. This then can be detected on DWI
Blood supply of 12-20ml/100mg/min
penumbra where brain survives but not functional
Desmoteplase
drug which passed for stroke to clinical trial phase 2 but not until the end
Be careful with patients taking
Anticoagulation drug
Any metal related work (for MRI)
How does DWI work?
Before:
Cells are normal
Brown Movement detected
ISCHEMIA altering NA-K ATPase function causing cytotoxic edema INFARCTION Diffusion decrease hyperintensity on MRI
After:
Cell size increase
BM is limited
When is stroke visual in imaging?
30mins
decrease in CT density (dCT)
1.5 hours
decrease in apparent diffusion coefficient (dADC) for DWI for 1.5 hours
CT is not detecting but MRI is detecting
Why is MRI better than CT?
MRI had more accurate detection for both trained and untrained doctors. As untrained doctors are the ones active at emergencies e.g. midnight, it is better suited.
When one should give up rescuing?
Once the brainstem is affected which leads to coma
Why MRI (DWI) over CT
CT is good enough to decide ischemic vs haemorrhage, however the distinction may only be detected after it is too late for treatment (post penumbra)
However, MRI can give additional below information to decide optimal treatment
DWI – lesion with impaired membrane function which indicates “near cell death” in majority of affected voxels
Stable – risk to increase over hours
FLAIR – acute infarction, likely to detect whether stroke is older than 4.5 h
Stable – chance to improve over many hours
MRA – site of occlusion or severe stenosis
Stable – chance to improve over hours
Perfusion MRI – CBF of MTT show hypoperfusion
volatile – risk to increase over hours
All scanning of MRI takes only 6 minutes!
AI is not yet ready to takeover the radiologist works
Vessel Imaging
-Look for hyperdense artery sign
-Graph shows thrombus bigger than 6mm is quiet deathly
If it is 3.5mm or bigger, can be removed by endovenous clot removal (catheter; takes one hour)
-If bigger than 10mm, should consider intraarteral treatment
Comparing images for better understanding of condition
For CT, for accuracy take 3 pictures back to back
DWI show change in 3h, FLAIR at least 5h (called the DWI-FLAIR mismatch)
Alteplase
(example of TPA)
Potential drug for stroke
Favourable outcome within 90 days 1.6X more likely
Can treat wake-up patients (patients with unknown symptoms onset) with MRI
occulusion/infarction
閉塞／梗塞
Score of Rankin Scala
0 no symptom 1 neurologist can find something 2 patient can complain 3 everyone can see symptoms 4 severely affected 5 bad 6 death
Summary for stroke imaging
Everyone can detect brain haemorrhage on brain CT scan
There is advanced CT/MRI techniques to analyse the physiology
MRI can be done in 6 minutes
MRI machine all include DWI
TIME IS BRAIN!!!
Can MRI be used for stroke imaging?
YES!
BOLD delay closely corresponds to established measure of perfusion
BOLD delay can be used to monitor stroke therapy/changes in natural history of stroke
What other disease can be detected by imaging?
dementia
Biomarker for dementia is FLAIR
- Hyperintensity of whiteness in the white matter, small vessels are dysfunctioning reducing the nutrients to white matter (severe microangiopathy)
- Not only related to chronic hypertension but also related to diabetes and metabolic syndrome
- Edema can cause brightness in picture, but after recovery leaves some black spots
- All biomarkers are not accurate nor specific, need to look for combination
Dementia vs aging
Normal people lose about 1% temporal lobe/year
AD loses 3%/year
No effective drug but one promising is AN1792(The antibody aducanumab reduce Aβ plaques)
Dementia/AD and imaging
AD is a clinical diagnosis
But AD patients cannot be dealt without imaging to exclude 2 month metastasis and hematoma血腫
For clinical research, do more than clinical examination to make sure to exclude other source of dementia (pure AD is rare)
Do CSF assessments, HEPA assessments and MRI
If drug is design, trace the after effect using MRI
