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Quantitative MR Imaging of Acute Stroke

Quantitative MR Imaging of Acute Stroke. Risto Kauppinen. Acute Stoke: Advances since 1990. Unambiguous diagnosis of acute ischemia by MRI (1990) Monitoring expansion of ischaemic damage by MRI (1991) rtPA introduced as a therapeutic agent (1996)

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Quantitative MR Imaging of Acute Stroke

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  1. Quantitative MR Imaging of Acute Stroke Risto Kauppinen

  2. Acute Stoke: Advances since 1990 • Unambiguous diagnosis of acute ischemia by MRI (1990) • Monitoring expansion of ischaemic damage by MRI (1991) • rtPA introduced as a therapeutic agent (1996) • Availability of CT scans for stroke A & E (since mid 90s) • [Shift to 3T MR scanners in Clinical Radiology (since 2005)] • [Computing power has increased and become cheaper]

  3. MRI: translation to clinic DWI (45 min) T2w (65 min)

  4. MRI: translation to clinic DWI (45 min) T2w (65 min) Kuharchyck et al. 1991 Warach et al. 1992

  5. Quantitative MRI (qMRI) • Each pixel in an image is represented by a physically • meaningful number • - Relaxation times (T1, T2, T1r), ADC, haemodynamics etc. • Normative values • - Requires acquisition of multiple data points Griffin JL et al. Cancer Res 63:3195, 2003

  6. qMRI in clinical settings Griffin JL et al. Cancer Res 63:3195, 2003

  7. qMRI in clinical settings Griffin JL et al. Cancer Res 63:3195, 2003

  8. Expectations from imaging in clinics Griffin JL et al. Cancer Res 63:3195, 2003 Radiol Clin N Am 49:1-26 (2011)

  9. Goals in acute stroke management • Rescue the penumbra • by maximising use of available • treatment strategies • Patient –specific management • Guide patient triaging • for investigational therapies

  10. DWI ADC image qMRI: Diffusion MRI in acute ischaemia -Catastrophic drop in CBF -Energy failure -Depolarisation -Disturbance in water homeostasis

  11. ADC and Blood Flow Ischaemia compromised normal blood flow Grohn et al. J Cereb Blood Flow Metab 20: 316, 2000

  12. ADC and Blood Flow Ischaemia penumbra normal blood flow ADC/Trace decrease in acute ischaemia is not an ON-OFF event motivation for qMRI Grohn et al. J Cereb Blood Flow Metab 20: 316, 2000

  13. qMRI: pixelwise histogram of ADCs ADC ADC map Normal Ischaemic Ischaemic + compromised V O L U M E

  14. qMRI: pixelwise histogram of ADCs ADC ADC map Normal Ischaemic Ischaemic + compromised V O L U M E

  15. qMRI: Potentials of (q)ADC • State of tissue beyond perfusion-diffusion mismatch as assessed • by volume (mis)match • Degree of ischaemia in parenchyma • Guide patient selection for reperfusion therapy

  16. qMRI: Potentials of (q)ADC • State of tissue beyond perfusion-diffusion mismatch as assessed • by volume (mis)match • Degree of ischaemia in parenchyma • Guide patient selection for reperfusion therapy

  17. Image pixels are either absolute T1 or T2 relaxation times Absolute T1/T2 are much more sensitive to parenchymal alterations than either T1w or T2w images MR relaxometry

  18. T1 and T2 in acute stroke

  19. 0.9 0.9 0.8 0.8 Dav Dav ( 10-3 mm2/s) Dav ( 10-3 mm2/s) 0.7 0.7 0.6 0.6 0.5 0.5 90 80 70 T1r 120 T1r(ms) 60 100 50 40 80 T1r(ms) 60 75 40 65 T2 T2(ms) 55 80 45 60 T2(ms) 40 20 25 min of reperfusion 24 h after ischaemia 45 min of ischaemia 35 min of hypoperfusion Multiparametric qMRI in acute ischaemia Gröhn O.H.J. et al. MRM 42: 268, 1999

  20. Areas analysed: Cortex1 Cortex2 Putamen Acute ischaemia Transition to irreversible 4 0.2 0.1 2 20 40 60 80 * 0 60 40 20 80 DDav (10-3 mm2/s) DT2 (ms) 0 -0.1 -0.2 * * -2 * * * ** * * -0.3 * * -4 * ** -0.4 ** -0.5 -6 Time post-ischaemia (min) Time post-ischaemia (min) Gröhn O et al. JCBFM 18:911 (1998)

  21. Time of Stroke Onset by MRI Vertebral artery occlusions Remote control graded occlusion 2 days later remote controlled gradual occluder Jokivarsi et al. Stroke 41; 2335-40, 2010

  22. Time of Stroke Onset Vertebral artery occlusions Remote control graded occlusion 2 days later remote controlled gradual occluder a) Controllable forebrain ischaemia b) Cortical hypoperfusion (’misery perfusion’) c) Middle cerebral artery (MCA) occlusion Jokivarsi et al. Stroke 41; 2335-40, 2010

  23. Time of Stroke Onset Vertebral artery occlusions Remote control graded occlusion 2 days later remote controlled gradual occluder a) Controllable forebrain ischaemia b) Cortical hypoperfusion (’misery perfusion’) c) Middle cerebral artery (MCA) occlusion Jokivarsi et al. Stroke 41; 2335-40, 2010

  24. Time of Stroke Onset Vertebral artery occlusions Remote control graded occlusion 2 days later remote controlled gradual occluder Calibration for human brain parenchyma not trivial a) Controllable forebrain ischaemia b) Cortical hypoperfusion (’misery perfusion’) c) Middle cerebral artery (MCA) occlusion Jokivarsi et al. Stroke 41; 2335-40, 2010

  25. Absolute T2 in Acute Stroke <3 hours of stroke: qT2 @1.5T Cut-off 7.5ms Sensitivity 0.824 Accuracy 0.794 ROC 0.757 (ROC(ADC) 0.635) Siemonsen et al. Stroke 40: 1612, 2009

  26. T1 in Acute Stroke 30 min 2.5 h 24 h Very early increase in T1 in Str by 63±16ms (+6%) Able to discriminate lesion expansion and non-damaging cortex, despite similar CBF values in early stroke

  27. C3 S2 C2 S1 C1 Multi-parametric MRI of Acute Stroke Jokivarsi et al. MRM under revision

  28. C3 S2 C2 S1 C1 Multi-parametric MRI of Acute Stroke 30 min of ischaemia 24 hours of ischaemia Jokivarsi et al. MRM under revision

  29. Focus on endogenous metabolites qMR spectroscopy (qMRS)

  30. State-of-the-art 1H MRS NAA Cr (lac) ‘1H MRS neurochemical profile at 3T’ Wilson et al. Magn Reson Med 65: 1 (2011)

  31. 1H MRS Metabolites in Stroke NAA Cr Lac Van der Toorn et al. MRM 32: 865 (1994)

  32. 1H MRS in Acute Stroke Saunders et al. JMRI 7: 1116 (1997)

  33. Reduced NAA: clinical stroke syndrome, more extensive infarction, severe drop in blood flow, presence of lactate Increased lactate: large infarcts and reduced NAA

  34. Reduced NAA: clinical stroke syndrome, more extensive infarction, severe drop in blood flow, presence of lactate Increased lactate: large infarcts and reduced NAA

  35. Low NAA and high lactate predicted expansion of DWI lesion

  36. qMR in acute stroke: Conclusions • Potentials to provide clinically important data from a single exam • Objective assessment of tissue status (early on) • Potentially guides clinical management of patients • Aids to maximise use of available therapies • Allows patient –specific treatment protocols

  37. qMRI/S in clinical setting • Standard clinical hardware • Requires expertise and commitment • Standardised MR protocols • Regular QA according to appropriate procedures • Automated on-line data processing • Computer-assisted decision making tools

  38. Stroke Management in the 21st Century Active prevention Thrombolysis Minocyclin Hematopoetic growth factors Hypothermia Remote preconditioning

  39. Application specific scanners Lower capital costs Lower running costs Increased availability at A&E Faster through-put Improved data quality Tissue status assignment for therapeutic procedures Improving overall outcome of stroke patients MR in Evaluation of Acute Stroke Patients in 2020s

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