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Contents

Contributors

Preface

1 The importance of specific diagnosis in stroke patient management

Introduction: A stroke is not a ‘stroke’

‘Lumping’ vs. ‘splitting’

Advances in imaging and stroke diagnosis

Initial stroke diagnosis

Stroke or stroke-mimic

Arterial occlusion, arterial rupture, or venous thrombosis

Cerebral venous thrombosis

Hemorrhagic Stroke

Specific diagnosis and management of ischemic stroke

Acute stroke

Practical application of acute stroke MRI

Stroke etiology and secondary prevention

Diagnosis of vascular lesions

Specific vascular diagnosis and management

Cardiac-origin embolism

Lesions of the aorta and great vessels

Cervical vascular lesions

Intracranial stenoses

Pathophysiological stroke diagnosis

Thrombosis and embolism

Hemodynamic stroke

Migraine and vasoconstriction

Systemic stroke risk factors

Multiple possible causes of stroke

Stroke severity

Patient variables

Specific diagnosis and stroke patient management

REFERENCES

2 Limitations of current brain imaging modalities in stroke

Introduction

Patient factors

Computed tomography

Sequence of changes that are seen on CT following a stroke

Computed tomographic angiography and perfusion imaging

Magnetic resonance imaging

Early ischemic changes are subtle

MRI in intracerebral hemorrhage

Echoplanar magnetic resonance imaging

Single photon emission computed tomography

Acquisition of SPECT studies

Radiolabelled tracers

SPECT analysis

SPECT in stroke

SPECT limitations

Positron emission tomography

Acquisition of PET images

Cerebral blood flow

Cerebral blood volume

Cerebral metabolic rate of oxygen and oxygen extraction fraction

Other PET techniques used to study cerebral ischemia

Limitations of PET

Conclusions

ACKNOWLEDGEMENTS

REFERENCES

3 Clinical efficacy of CT in acute cerebral ischemia

Level 1 of clinical efficacy: technical capacity of CT in acute cerebral ischemia

CT detection of intracranial blood

CT detection of arterial obstruction

CT detection of brain tissue swelling

CT detection of ischemic brain edema

Level 2 of clinical efficacy: diagnostic accuracy of CT in acute cerebral ischemia

Diagnostic accuracy of CT in detecting intracranial hemorrhage

Diagnostic accuracy of CT in detecting arterial obstruction

Diagnostic accuracy of CT in detecting ischemic brain tissue swelling

Level 3 of clinical efficacy: diagnostic impact of CT in acute cerebral ischemia

Diagnostic impact on intracranial hemorrhage

Diagnostic impact on ischemic edema

Level 4 of clinical efficacy: therapeutic impact of CT in acute cerebral ischemia

Level 5 of clinical efficacy: impact on patient outcome of CT in acute cerebral ischemia

REFERENCES

4 Computerized tomographic-based evaluation of cerebral blood flow

Introducton

Xenon CT cerebral blood flow

Clinical applications of XeCT

Acute stroke

Chronic cerebral ischemia

Intracerebral hemorrhage (ICH)

Subarachnoid hemorrhage (SAH) and vasospasm

CT perfusion

Clinical applications of CT perfusion

Conclusions

REFERENCES

5 Technical introduction to MRI

Introduction

The integrated MR stroke ‘protocol’

The T-weighted image

The T-weighted image

Magnetic resonance angiography

Diffusion-weighted imaging

Perfusion-weighted imaging

Perfusion imaging using endogenous contrast agents

Magnetic resonance spectroscopy

Conclusion

REFERENCES

6 Clinical use of standard MRI

Introduction

Pathology of ischemic infarction

MRI technique

Plain MRI appearances of ischemic infarction

Conventional T- and T-weighted sequences

Contrast-enhanced T-weighted sequences

Fluid attenuated inversion recovery (FLAIR)

Magnetic resonance angiography (MRA)

Magnetization Transfer Contrast (MTC)

Hemorrhagic infarction

Differential diagnosis

Normal anatomical variants

Brain tumours

Encephalitis/cerebritis

Conclusion

REFERENCES

7 MR angiography of the head and neck: basic principles and clinical applications

Basic principles of MRA

Time of flight

Phase contrast

Contrast-enhanced MRA

Contrast agent dosage and timing

Technical considerations

Comparison of time-of-flight and CE 3DMRA

Clinical applications

Extracranial carotid and vertebral arteries

Stenotic disease

Flow measurement

Plaque

Dissection

Circle of Willis

Stenotic disease

Collateral flow and function

Aneurysm

Vascular malformation

Intracranial veins

Works in progress

Spiral imaging

Balanced steady-state free precession

Variants in K-space sampling

Parallel imaging

Conclusions

REFERENCES

8 Stroke MRI in intracranial hemorrhage

Introduction

MRI signatures of acute, subacute and chronic ICH

MRI in hyperacute ICH

MRI in subarachnoid hemorrhage

Future prospects of stroke MRI in ICH

Conclusion

REFERENCES

9 Using diffusion–perfusion MRI in animal models for drug development

Introduction

Diffusion–perfusion MRI in animal stroke models

Preclinical evaluation of new stroke therapies

Using diffusion–perfusion MRI in animals to assess therapy

Conclusions

REFERENCES

10 Localization of stroke syndromes using diffusion-weighted MR imaging (DWI)

Introduction

Clinical representations of DWI results

DWI sensitivity to strokes according to their location

DWI and stroke extent

Multiple cerebral infarcts: DWI demonstrates the one responsible for the acute symptomatology

Therapeutic impact of DWI

Conclusion

REFERENCES

11 MRI in transient ischemic attacks: clinical utility and insights into pathophysiology

Overview

Standard MR imaging studies in patients with transient ischemic attacks

MR spectroscopy in transient ischemic attacks

Diffusion MRI in transient ischemic attacks

UCLA study

Duke, Massachusetts General Hospital and additional studies

Discussion of diffusion MR findings

A new, tissue-based definition of transient ischemic attacks

Conclusion

ACKNOWLEDGEMENTS

REFERENCES

12 Perfusion-weighted MRI in stroke

Introduction

Contrast agents in PWI

Pulse sequences

Image postprocessing

Interpretation of perfusion-weighted images

Conclusions

REFERENCES

13 Perfusion imaging with arterial spin labelling

Introduction

Arterial spin labelling methods

Labelling strategies for ASL

Quantification of perfusion with ASL

Motion artefacts and ASL

Multislice ASL imaging

Validation of ASL perfusion MRI

Applications to cerebrovascular disease

Perfusion mapping in animal models

Clinical applications in stroke

Discussion

REFERENCES

14 Clinical role of echoplanar MRI in stroke

Introduction

Imaging techniques in brain ischemia (Table 14.1)

Clinical applications of EPI in acute stroke

Diagnosis of acute and chronic ischemia

Stroke prognosis

Relationship between DWI and PWI: imaging tissue at-risk in the ischemic penumbra

Infarct topography and pathogenesis

Use of DWI/PWI as surrogate endpoints in investigational drug trials

Selection of patients for acute therapies

MR spectroscopy in clinical practice

Conclusions and future directions

REFERENCES

15 The ischemic penumbra: the evolution of a concept

Definition

Importance

Flow thresholds for the ischemic penumbra

The dynamic and time-related nature of the penumbra

The ischemic penumbra: a molecular view

Defining the ischemic core in molecular terms

Defining the ischemic penumbra in molecular terms

Ischemic penumbra: operational definitions in humans

Positron emission tomography (PET)

O PET

Single photon emission computed tomography (SPECT)

Computerized tomography (CT) perfusion radiography

Xenon-enhanced CT

Magnetic resonance diffusion-weighted and perfusion imaging of the penumbra

Diffusion-weighted MRI (DWI)

Perfusion MRI

Magnetic resonance imaging: proton spectroscopy

Proton magnetic resonance spectroscopy

Future directions

REFERENCES

16 New MR techniques to select patients for thrombolysis in acute stroke

Introduction

Imaging the ischemic penumbra: the gold standard(s)

Diffusion- and perfusion-weighted imaging to study the ischemic penumbra.

DWI and ADC lesions are reversible

Visual analysis of the PWI lesion does not accurately identify tissue at risk of infarction

Factors influencing DWI and PWI lesion evolution

Monitoring thrombolysis using DWI and PWI

Use of DWI and PWI as surrogate markers in acute stroke trials

Future prospects

ACKNOWLEDGEMENTS

REFERENCES

17 MRI as a tool in stroke drug development

The need for a more rationale approach to clinical development of stroke therapeutics

Patient selection (Table 17.1)

Proof of pharmacological principle using MRI as a marker of response to therapy: replicating the preclinical experiment…

Surrogate endpoint in Phase III trials

Concluding remarks

REFERENCES

18 Magnetic resonance spectroscopy in stroke

Basic requirements

Basic principles of MRS

Quantification of metabolites

The normal [H]-MRS spectrum (Fig. 18.2)

N-acetyl aspartate (2.01 ppm)

Creatine (3.94 and 3.03 ppm)

Choline (3.22 ppm)

Lipid/macromolecule resonances

[H]-MRS changes in cerebral ischemia

Lactate (doublet at 1.33 ppm)

NAA (2.01 ppm)

Cr/PCr (3.94 and 3.03 ppm)

Choline (3.22 ppm)

Glutamate and other amino acids

Lipids/macromolecules

Reversible changes detected by [H]-MRS

Prediction of outcome

Understanding disability

Selection of patients for treatment

Conclusions

ACKNOWLEDGEMENT

REFERENCES

19 Functional MRI and stroke

Introduction

Technical background

Functional magnetic resonance imaging

Trial design and paradigm selection

Data analysis and statistics

Mapping with FMRI

Neural plasticity post-stroke

Imaging motor recovery

Recovery in post-stroke aphasia

Other FMRI studies of stroke recovery

Future directions

REFERENCES

Index