Imaging

Question 1

Cerebral ischemia Early signs on CT?

Answer 1

Hyperdense artery sign
insular ribbon sign
Loss of lentiform
nucleussulcal effacement

Question 2

Easpects

Answer 2

Automated CT reader

Issue of CT scan passing the limit sensitivity remains

Question 3

How unprofessional can spot stroke

Answer 3

Speech problem
Visual problem
Muscle weakness

Question 4

How to professionally identify stroke

Answer 4

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)

Question 5

Difficulty of analysing stroke in imaging

Answer 5

-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

Question 6

Neuroradiology enabling stroke treatment

Answer 6

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

Question 7

Neuroradiology assess time window for stroke

Answer 7

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)

Question 8

Neuroradiology illustrate pathophysiology

Answer 8

perfusion imaging with Time Shift Analysis
O2 extraction fraction
pH imaging

Question 9

Physics behind DWI

Answer 9

(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

Question 10

Blood supply of 12-20ml/100mg/min

Answer 10

penumbra where brain survives but not functional

Question 11

Desmoteplase

Answer 11

drug which passed for stroke to clinical trial phase 2 but not until the end

Question 12

Be careful with patients taking

Answer 12

Anticoagulation drug

Any metal related work (for MRI)

Question 13

How does DWI work?

Answer 13

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

Question 14

When is stroke visual in imaging?

Answer 14

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

Question 15

Why is MRI better than CT?

Answer 15

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.

Question 16

When one should give up rescuing?

Answer 16

Once the brainstem is affected which leads to coma

Question 17

Why MRI (DWI) over CT

Answer 17

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

Question 18

Vessel Imaging

Answer 18

-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

Question 19

Comparing images for better understanding of condition

Answer 19

For CT, for accuracy take 3 pictures back to back

DWI show change in 3h, FLAIR at least 5h (called the DWI-FLAIR mismatch)

Question 20

Alteplase

Answer 20

(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

Question 21

occulusion/infarction

Answer 21

閉塞／梗塞

Question 22

Score of Rankin Scala

Answer 22

0 no symptom				
1 neurologist can find something				
2 patient can complain				
3 everyone can see symptoms				
4 severely affected				
5 bad				
6 death

Question 23

Summary for stroke imaging

Answer 23

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!!!

Question 24

Can MRI be used for stroke imaging?

Answer 24

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

Question 25

What other disease can be detected by imaging?

Answer 25

dementia

Question 26

Biomarker for dementia is FLAIR

Answer 26

• 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

Question 27

Dementia vs aging

Answer 27

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)

Question 28

Dementia/AD and imaging

Answer 28

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