Stroke Imaging

Discussion in Picture Form (mostly)

Jeremy Hopkin M.DNeuroradiology lead IHC

Goals

• Lots of pictures – little text

• Limit use of technical jargon

• Historical neuro imaging - biased to stroke

• Review current modalities and strength/weakness

• IHC approach to stroke imaging

• Have some fun (hopefully)

• End early

Skull x rays

Ventriculostomy – air contrast

Pneumoencephalography – air contrast

“Even if it could be made to work as you suggest, we cannot imagine a significant market for such an expensive apparatus which would do nothing but make a radiographic cross-section of a head.”

oldendorf

First CT

Hounsfield

Contrast - CTA

Contrast - CTP

MRI

Modalities for further discussion:

-CT-CTA-CTP-MRI

Focus on ischemic stroke but at least touch on hemorrhagic

CT – hemorrhagic stroke

Blood or Calcification?

CT -Ischemic stroke 4 hours

CT – 3.5 hours

CT - hemorrhage

CT subacute/chronic – “fogging”

CT - chronic

CT – accuracy?

CT - Dense MCA

CTA – hemorrhagic stroke

CTA – ischemic stroke

CTA – ischemiaSource images

CTA – multi phase “collateral”

CTP – ischemic stroke

Inherent limitations of technique:– Flow– Hematocrit– Oxygen extraction – Chronicity of ischemia– Metabolic demands of tissue– Temperature– Genetics

Quick understanding of market potential by vendorsDevelopment of multiple systems in collateralUsually proprietary methodsEnd is fairly dissimilar products trying to be utilized for the same goal

Extensive and confusing literatureIf A=B, and B=C and C=D does A=D ? They are often compared to one another or another surrogate marker for stroke but are not consistently compared to DWI

CTP - RAPID

CTP – bottom line

• CORRELATES with final infarct volume

• Wide variability between techniques/software

• Some software packages seem to be more precision (RAPID)

• CANNOT accurately depict final infarct volume

• Does it matter? Is correlation good enough for patient selection?

MRI – hemorrhagic stroke

MRI – ischemic stroke

DWI – Sensitivity/Specificity 95+ %Volume accuracy – typically within 5 ccRanges from 0-20cc

Advanced techniques - Summary

What we know - imaging

• MRI– Best non invasive evaluation of infarct core– Slightly more sensitive for blood than CT– Still relatively slow

• CT– Great for detecting blood– Not great for core– fast

• CTA– Great for detecting occlusion– CTA SI moderate for detecting core– Fast

• CTP– Moderate for detecting infarct core– Pretty fast– RAPID software is likely most precise and is fast

Approach to acute stroke imaging

• Be fast– Triage, access to equipment and transport– Streamline and standardize imaging towards speed– Open and standardized communication pathways

• Be accurate– Use best evidence to standardize image acquisition, post process

and display– Repetitive/Constant peer review

• Be reproducible– Standardized reporting

• Be open to innovation and flexible to incorporate new data– System approach lends itself to constant review of data and agility

to respond quickly

IHC approach (in evolution)

• CT (Service process model complete)– ASPECTS score report– Communication (documented)

• CTA (Service process model in process)– Performed for all stroke cases (ischemic/hemorrhagic)– Used at all centers seeing acute stroke patients with capability– Used liberally to screen for LVO with stroke symptoms– CTA SI ASPECTS score report– Communication of LVO (documented)

• CTP (Service process model in process)– Deployed selectively (typically at endovascular centers) – RAPID software at endovascuar centers

• MRI (not developed)– Use liberally for stroke mimics, difficult cases or standard acute cases if available– Standardize rapid stroke protocols

How do we get this done?

• NSCP– Guidance council for all things

neuro– Neuro lead takes information

from NSCP to inform SPM process development

• ISMC– Guidance council for radiology– Voting control from each group

– single representative– SPM presented and voted upon– Incentive/punitive for SPM use– SPM subject to yearly review at

minimum

Lessons from the past

• Potentially obsolete or underutilized technology may resurface – sometimes in unexpected ways

• Need for advanced imaging is almost always underestimated

• Slow becomes fast

• Less accurate becomes more accurate

• FUTURE - Move from anatomic towards physiologic/metabolic imaging fused with anatomy

Future directions stroke (Opinion)

• More MRI. – Speed?

• Screening? Got to make this fast. How is this not one of the first things on an EMR?

• More MRI compatible devices• More MRI with “non” compatible devices • Culture. Speed over quality. Historically this has been used in a non emergent

setting. CT techs and MRI techs don’t think the same. Barrow experience

– Physiologic/metabolic imaging. O2 imaging?– Better outcomes with improved risk stratification and selection

• CT advances– Dual energy for thrombus morphology?– Dual energy and core detection ?– New perfusion techniques??

• New technology from endovascular or diagnostic side

M2 occlusionDo you treat ?

Goals

• Lots of pictures – little text

• Limit use of technical jargon

• Historical neuro imaging - biased to stroke

• Review current modalities and strength/weakness

• IHC approach to stroke imaging

• Have some fun (hopefully)

• End early