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					FERNE / MEMC IV Brain Illness and Injury Course:
Head CT Interpretation and Advanced Neuroimaging in ED Stroke Patients
Andrew Asimos, MD, FACEP


       Head CT Interpretation and
       Advanced Neuroimaging in
          ED Stroke Patients
                        Andrew Asimos, MD
                   Director of Emergency Stroke Care
                                                                            FERNE Brain Illness
                        Carolinas Medical Center
                              Charlotte, NC                                  and Injury Course
        Adjunct Associate Professor, Department of Emergency Medicine
         University of North Carolina School of Medicine at Chapel Hill




                                                                                    Disclosures
                                                                          • NovoNordisk, Boehringer Ingelheim
                4th Mediterranean                                           Advisory Boards
               Emergency Medicine                                         • Research support from Boehringer
                                                                            Ingelheim
                    Congress
                  Sorrento, Italy
               September 17, 2007
                                           Andrew Asimos , MD                                       Andrew Asimos , MD




           Session Objectives                                               Key Learning Points
           •   Review findings consistent with early                       • Non-contrast CT features of early ischemic
               ischemic changes on non-contrast CT                           stroke are subtle, with considerable inter-
                                                                             reader variability
           •   Understand the basis for the clinical                       • CTP more accurate than unenhanced CT for
               application of CTA and CTP imaging in                         detecting stroke and determining the extent
               acute stroke                                                  of stroke
           •   Understand the images that comprise a                       • CTA excellent at detecting large vessel
               CTA/CTP series                                                occlusion
                                                                           • CTA and CTP will likely replace non-
           •   Understand the limitations of CTP                             contrast CT as the imaging standard within
               imaging                                                       the next few years

                                           Andrew Asimos , MD                                       Andrew Asimos , MD




                                                                                                                           1
FERNE / MEMC IV Brain Illness and Injury Course:
Head CT Interpretation and Advanced Neuroimaging in ED Stroke Patients
Andrew Asimos, MD, FACEP


             Case: Patient presenting
              within 3 hour window                                                Essential Imaging Questions
                                      •   50 yo male                                      •   Is there hemorrhage?
                                                                                          •   Are findings consistent with acute
                                      •   CT less than 2 hours                                ischemic stroke?
                                          within symptom onset                            •   Can this imaging modality’s results
                                                                                              add to my risk/benefit analysis?
                                      •   Awake, alert, dysarthric                            •   Is there large vessel occlusion?
                                      •   Fixed right sided gaze                              •   Is there “irreversibly” infarcted core?
                                                                                              •   Is there “salvageable” penumbra?
                                      •   Left sided weakness                                 •   Are other findings present that should be
                                                                                                  considered
                                                                                                   •   Microbleeds
                                                                                                   •   Leukoaraiosis

                                                            Andrew Asimos , MD                                             Andrew Asimos , MD




                  The Four P’s of Acute
                     Stroke Imaging                                               Evolution of an Infarct on CT
       Parenchyma                      Assess early signs of acute stroke, rule
                                       out hemorrhage

       Pipes                           Assess intracranial and extracranial
                                       circulation for evidence of
                                       intravascular thrombus
       Perfusion                       Assess cerebral blood flow, blood
                                       volume, and mean transit time

       Penumbra                        Assess tissue at risk of dying if
                                       ischemia continues
       Rowley HA et al. Am J Neuroradiol 2001;22:599-601.
                                                                                   6hrs                24hrs       48hrs           72hrs        96hrs
                                                            Andrew Asimos , MD                                             Andrew Asimos , MD




          Hyperacute Stroke: Subtle
          Signs on Non-contrast CT                                                    Hyperdense MCA Sign
              •   Hyperdense MCA sign
              •   Obscuration of the lentiform
                  nucleus and basal ganglia
              •   Effacement of the subinsular cortex
              •   Subtle crowding of sulci from early
                  edema



                                                            Andrew Asimos , MD                                             Andrew Asimos , MD




                                                                                                                                                        2
FERNE / MEMC IV Brain Illness and Injury Course:
Head CT Interpretation and Advanced Neuroimaging in ED Stroke Patients
Andrew Asimos, MD, FACEP


        Obscuration of the Lentiform                      Effacement of the
         Nucleus and Basal Ganglia                        Subinsular Cortex




                         Andrew Asimos , MD                                   Andrew Asimos , MD




         Subtle Crowding of Sulci                   Case: Patient presenting
            from Early Edema                         within 3 hour window
                                                                •   50 yo male
                                                                •   CT less than 2 hours
                                                                    within symptom onset
                                                                •   Awake, alert, dysarthric
                                                                •   Fixed right sided gaze
                                                                •   Left sided weakness



                         Andrew Asimos , MD                                   Andrew Asimos , MD




         Case: Patient presenting                   Case: Patient presenting
          within 3 hour window                       within 3 hour window




                                                Initial    BF            BV             TTP

                         Andrew Asimos , MD                                   Andrew Asimos , MD




                                                                                                   3
FERNE / MEMC IV Brain Illness and Injury Course:
Head CT Interpretation and Advanced Neuroimaging in ED Stroke Patients
Andrew Asimos, MD, FACEP


                  Case:                                                       Case:
             “Wake up” Stroke                                             “Wake up” Stroke




               0735 at outside hospital
                              Andrew Asimos , MD                                                               Andrew Asimos , MD




                 Case:
             “Wake up” Stroke                                      Therapeutic Window
                                                            •    Time from symptom onset used for
                                                                 theoretical and practical reasons
                                                            •    Increasingly will rely on imaging
                                                                 studies to determine tissue
                                                                 salvageability and clot burden



                1030 at stroke center

                              Andrew Asimos , MD                                                               Andrew Asimos , MD




         Good Collateral Flow will Buy                 Advanced CT Imaging for Acute
          you Some Time and Brain                         Stroke: CTP versus MRI
                                                                      Parameters         Definition of   Advantages               Limitations
                                                                                          Penumbra

                                                      CT     CBF, CBV, MTT                               •Combined     •Limited brain coverage
                                                   Perfusion MTT, TTP threshold                          with plain    •Poorly sensitive to
                                                                                        at 145%          CT            posterior circulation
                                                                                                         •Available    •Iodonated contrast
                                                                                                         •Fast


                                                   DWI-PWI           CBF, CBV, Relative                  •Sensitive    •Limited availability
                                                    MRI              MTT, TTP, TTP (or                   •No           •Patientcooperation
                                                                     ADC       MTT) delay                radiation     required
                                                                               >45s and                                •Frequent
                                                                               normal                                  contraindications
                                                                               DWI
                                                   Muir KW et al. Lancet Neurology 2006; 5:755-768


                              Andrew Asimos , MD                                                               Andrew Asimos , MD




                                                                                                                                                 4
FERNE / MEMC IV Brain Illness and Injury Course:
Head CT Interpretation and Advanced Neuroimaging in ED Stroke Patients
Andrew Asimos, MD, FACEP



        CT Perfusion Terminology                                                               Definitions
                                                             Perfusion                                  The steady-state delivery of blood to
                                                                                                        cerebral tissue through the capillaries

                                                             CBF                                        Volume flow rate of blood through the
                                                                                                        cerebral vasculature per unit time
                                                             (Cerebral Blood Flow)

                                                             CBV                                        Amount of blood in a given amount of
                                                                                                        tissue at any time
                                                             (Cerebral Blood Volume)

                                                             MTT                                        Average time it takes for blood to
         Blood Flow     Blood Volume     Mean Transit Time                                              traverse from the arterial to the venous
                                                             (Mean Transit Time)
                                                      or                                                side of the cerebral vasculature
                                             Time to Peak

                                 Andrew Asimos , MD                                                                    Andrew Asimos , MD




       Changes in Cerebral Vascular Physiology
                                                                          Relationship between
        with Worsening Circulatory Impairment                              CBV, CBF, and MTT

                           CBF         CBV MTT
        Salvageable        ↓ ↔↑ ↑
        Penumbra
                           ↓↓ ↓ ↑
        Irretrievable      ↓  ↓ ↑↑                                   Blood Flow                          Blood Volume             Mean Transit Time
                                                                                                                                            or
        Infarct                                                            MTT= CBV/CBF                                               Time to Peak
                                 Andrew Asimos , MD                                                                    Andrew Asimos , MD




         Example of the Progression
            of Advanced Images                                                       Conclusions
                                                                      •   CTP more accurate than
                                                                          unenhanced CT for detecting stroke
                                                                          and determining the extent of stroke
                                                                      •   Possible to distinguish penumbra
                                                                          from infarcted tissue
                                                                      •   Correlation between PCT/CTA and
                                                                          MRI is excellent
                                                                      •   Already used in DIAS and DEDAS
                                                             Wintermark M et al. Am J Neuroradiol 2005;26(1):104-12.
                                 Andrew Asimos , MD          Wintermark M et al. Stroke 2006;37:979-985.               Andrew Asimos , MD
                                                             Wintermark M et al. Neurology 2007;68(9):694-697.




                                                                                                                                                      5
FERNE / MEMC IV Brain Illness and Injury Course:
Head CT Interpretation and Advanced Neuroimaging in ED Stroke Patients
Andrew Asimos, MD, FACEP


              Important Remaining
                CTP Questions
          •   What is the interrater reliability of visual
              estimation of lesion volumes?                                              Questions?
              •   Is that variability clinically important?
          •   Can computerization automate                               www.FERNE.org
              measurement of absolute perfusion
              thresholds and lesion volume in a
              clinically meaningful way?                                 aasimos@carolinas.org
              Will the current perfusion thresholds for
          •
              penumbra and infarct be maintained with
                                                                         704 355 4212
              rigorous future testing?
                                                               ferne_memc_2007_braincourse_asimos_neuroimaging_091707_finalcd
                                                               9/27/2007 10:49 AM
                                          Andrew Asimos , MD                                                             Andrew Asimos , MD




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