Perfusion Computed Tomography in

Acute Ischaemic Stroke

Nguyễn Trường Giang Thai Nguyen Central General Hospital, Vietnam Central for Advanced Imaging, The University of Queensland, Australia

Hanoi, nov 2015

Outline

u  Brief introduction u  Stroke Imaging u  Perfusion CT techniques u  Use of perfusion CT in acute stroke u  Future direction of perfusion CT u  Conclusion

Introduction •  Stroke is one of the leading causes of deaths and disabilities. •  16 million new cases, approx. 6 million deaths annually (Strong,

2007) •  Ischaemic stroke accounts for 80% of all strokes •  Target for recanalisation treatment •  Blood-brain barrier breakdown is one of the major pathological

changes •  Infarct core:

–  Dead brain tissue –  Formed quickly after onset –  Cerebral blood flow threshold <20ml/100g/min –  Continue to grow and stabilises at day 5 from onset, gliosis

keep progressing. •  Penumbra:

–  Damaged but still alive tissue –  Salvageable with restoration of blood flow

Moustafa & Baron 2008

Heiss 2011

Four critical questions must be answered at patient admission (Shetty & Lev 2005):

a.  Is this a haemorrhagic stroke? b.  Is there thrombotic occlusion of a cerebral artery that can be treated

by thrombolysis or thrombectomy? c.  Is an infarct core present in the ischaemic region? d.  Is there potentially salvageable penumbral tissue?

Introduction

Stroke Imaging

u  Target for Stroke Imaging: u  Gives early diagnosis

u  Differentiates subtypes of stroke

u  Gives accurate amount of affected brain tissue and amount of dead brain

u  Unenhanced CT, CT Angiography & Perfusion CT u  Magnetic Resonance Imaging, MRA & MRP u  DSA & Endovascular intervention

Stroke Imaging

4+ Ps in Stroke u  Parenchyma: Indicate the early signs of acute ischaemic stroke, exclude haemorrhage

u  Pipes: Gives information of vessels u  Extracranial circulation (carotid and vertebral arteries of the neck)

u  Intracranial circulation for evidence of intravascular thrombus

u  Perfusion Assess cerebral blood volume, cerebral blood flow, and mean transit time

u  Penumbra Assess tissue at risk of dying if ischemia continues without recanalization of intravascular thrombus Imaging.

u  Permeability: Evaluate changes in blood-brain barrier permeability following ischaemic insult

Rowley (2001) AJNR 22(4):599-601

Stroke Imaging: Un-enhanced CT

Early signs of ischaemic stroke include:

u  Dense MCA

u  Obscuration of lentiform nucleus

u  Narrowing of cerebral sulci

Stroke Imaging: CT angiography

•  Indicate location, size of the clot •  Give information of collateral vessel •  Evaluate tortuosity of the carotid, access path of thrombectomy

Srinivasan (2006) Radiographics

Stroke Imaging: Perfusion CT

•  Give information of blood flow, blood volume •  Define the entire volume of affected tissue •  Measure volume of the infarct core and penumbra

u  Cerebral blood flow (CBF): Infarct starts when CBF<20ml/100g/min

u  Cerebral blood volume (CBV): infarct threshold 2ml/100g

u  Mean transit time (MTT): Abnormal threshold >145% compared to the contralateral hemisphere

u  Time to peak (TPP): Abnormal cut off 4 seconds delay compared to the opposite side.

Giang Nguyen 2013, PhD Thesis, University of Queensland

Stroke Imaging: Perfusion CT

Wintermark 2006

Stroke Imaging: Perfusion CT / Technique

Giang Nguyen (2012), AOCR Meeting, Sydney

Stroke Imaging: Perfusion CT / Technique

Giang Nguyen (2013) NeuroImage: Clinical

Stroke Imaging: Perfusion CT / Technique

Ostergaard 1996 & Konstas 2009

Stroke Imaging: Perfusion CT

CBF CBV MTT

Stroke Imaging: Perfusion CT / Permeability

Stroke Imaging: Perfusion CT / Permeability

MTT

CBF

CBV BBBP

Perfusion & Permeability maps may predict imaging outcome

Stroke Imaging: Perfusion CT / Permeability

CBF

CBV

MTT BBBP

Perfusion & Permeability maps may predict imaging outcome

Stroke Imaging: Perfusion CT / Permeability

CBF

CBV

MTT BBBP

Perfusion & Permeability maps may predict imaging outcome

u  Perfusion CT can be used in patient selection in some stroke centres •  Help to measure brain perfusion & blood-brain barrier permeability

•  High sensitive in detection ischaemic stroke in anterior circulation (Bivard 2013)

•  May help predict complications (haemorrhage, massive oedema) (Nguyen 2013)

•  Help considering recanalisation treatment

u  However, current stroke guidelines have not included perfusion CT

§  Lacuna, posterior circulation lesions and reperfusion information need to be validated (Bivard 2013)

§  CBV based infarct volume may not replace DWI – MRI (Copen 2015)

§  Perfusion parameters are varied between software packages (Kudo 2013)

§  Benefit of Perfusion CT for selecting patients has not ben proven (Power 2015)

§  Further randomised studies are necessary (Power 2015)

Stroke Imaging: Perfusion CT / Permeability

Stroke Imaging: Perfusion CT / Technique

SVD: Single Value Decomposition IF: Inverse Filter MS: Maximum Slope bMTF: Box Modular Transfer Function

Kudo (2010) Radiology

A variety of mathematic algorithms applied to measure perfusion parameters used in different software packages may lead to inconsistency in blood flow measurement

Perfusion CT: Future direction Tumoral perfusion: renal, lung, prostate…

Impossible d'afficher l'image. Votre ordinateur manque peut-être de mémoire pour ouvrir l'image ou l'image est endommagée. Redémarrez l'ordinateur, puis ouvrez à nouveau le fichier. Si le x rouge est toujours affiché, vous devrez peut-être supprimer l'image avant de la réinsérer.

Luczynska 2014 Chen 2014

Giang Nguyen 2014

Conclusion o  Perfusion CT give the last 3 Ps in 4P+ in Stroke imaging: Perfusion, Penumbra

& Permeability

o  Along with CT, CTA, Perfusion CT may help in patient selection for recanalisation treatment

o  Perfusion CT may help to predict stroke complications and radiological outcome

o  Perfusion CT may be more accessible than MRI in many stroke centres

o  Software to create perfusion map needs to be consistent

o  More randomised studies needed for prove benefit of perfusion CT

o  Perfusion CT may be used in other body parts: lung, prostate…

Thank you!

Acknowledgement:

•  Centre for Advanced Imaging, University of Queensland, Australia: David Reutens

•  Royal Brisbane & Women’s Hospital, Australia:

•  Alan Coulthard

•  Andrew Wong

•  Robert Henderson

•  Dept of Radiology, Newcastle Hospital, NSW, Australia: Mark Parsons

•  Thái Nguyên Central General Hospital, Vietnam