Contrast-Enhanced MR Perfusion Imaging - University of Wisconsin ...

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Overview: CT and MR Perfusion Methods Inject Scan Model Parameter Maps Overview: CT and MR Perfusion Methods Inject Scan Model Parameter Maps CT I CT I MTT CBV CBF MR Gd MR Gd Key Perfusion Parameters • Cerebral Blood Flow (CBF) – Delivery of blood to tissue / unit time – Units: ml / 100g brain / min • Cerebral Blood Volume (CBV) – Measure of autoregulation – Units: ml / 100 g brain • Mean Transit Time (MTT) – Average time to flow thru capillaries (artery → vein) – Units: seconds CBF = CBV MTT Central Volume Principle Ischemia: Hemodynamics & Perfusion • ↑ Collateral flow → ↑ MTT • Vasodilatation → ↑ CBV (until CPP ↓) • End result: ↓ CBF Central volume theory MTT CBF = CBV MTT CBV CBF Ischemia: Hemodynamics & Perfusion Perfusion Modeling • ↑ Collateral flow → ↑ MTT • Vasodilatation → ↑ CBV (until CPP ↓) • End result: ↓ CBF MTT CBV CBF Central volume theory CBF = CBV MTT Zaharchuk, G. AJNR 2007; 28: 1850-1858
Perfusion and Traffic Jams… • Long transit times MTT • Collateral routes CBV • Variable net effect CBF Penumbral Imaging Perfusion-Diffusion Mismatch DWI MTT Penumbra = Target for Intervention Clinical Trials - PWI/DWI Mismatch • DIAS, DEDAS, DIAS-2 (Hacke) – 3-9 hours, Desmoteplase vs placebo • DEFUSE (Wechsler) – 3-6 hours, open label IV tPA • EPITHET (Davis) – 3-6 hours, IV tPA vs placebo – Selected by CT, but all get PWI/DWI – MR at 3-5 days and 90 days – Unique design: is the PWI/DWI concept valid? • MR RESCUE (Kidwell) – 0-8 hours – MERCI retrieval vs medical therapy Desmoteplase Trials: DEDAS / DIAS Dose Escalation study of Desmoteplase in Acute ischemic Stroke Desmoteplase In Acute ischemic Stroke Trial Overview: Double blind, randomized, placebo controlled trials IV delivery, 3-9 hour time window Plasminogen activator – from vampire bat saliva Selection based on PWI-DWI Mismatch MRI Inclusion: PWI defect at least 2 cm AND ~20% larger than DWI PWI should be obvious, even visible on raw images MRI Exclusion: DWI > 1/3 MCA MRA: ICA occlusion DIAS Results: Hacke et al Stroke 2005; 36:66-73 DEDAS Results: Furlan et al Stroke 2006; 37:1227-1231 BATS Diffusion-Perfusion Mismatch Treatment Triage % 80 70 60 50 40 Desmoteplase – DIAS Results Hacke et al, Stroke 2005; 36:66-73 46.7 46.7 71.4 60 49.3 38.7 102 patients 3-9 hours IV DSPA PWI > DWI 30 20 10 0 23.1 13 19.2 22.2 62.5 90 125 Total Placebo Desmoteplase dose (μg/kg) vs placebo Reperfusion Favorable Outcome
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