Computed Tomography Perfusion Is Beyond Prime Time

Computed tomography perfusion (CTP) is beyond prime time, ready for use to select patients with acute ischemic stroke for intravenous and endovascular reperfusion therapies in routine clinical practice. After 2 decades of fervent stroke research using advanced imaging and revascularization techniques, recent stroke trials astutely combined imaging and therapeutic expertise, likely the recipe for their resounding success. Multimodal CT, including CTP, was a key element in these trials that selected individuals with favorable collateral profiles and resultant improved outcomes after effective reperfusion. Academic discourse about optimal thresholds of ischemic core and mismatch volumes comprise late news, beyond prime time. Literature of only a few years ago aptly predicted the pivotal role of CTP. Lev eloquently noted the impact of collateral perfusion, critical data from a snapshot of hemodynamics, and the essential imaging goals of delineating core to avert hemorrhage while measuring salvageable tissue at-risk that need not be perfect. Prior trials failed to leverage advanced imaging or alternatively, entwined imaging and reperfusion inefficiently. In 2015 and beyond, triage of acute ischemic stroke for potential reperfusion should rapidly and efficiently identify optimal candidates for thrombolysis and thrombectomy across the broadest population. Multimodal imaging can swiftly address ischemic injury in the brain, arterial occlusion, collateral status, and the topography of perfusion that map the risk of hemorrhagic transformation and nutritive reperfusion. As noted by Lev, multimodal imaging is brain and may improve outcomes and optimize costs. The stroke community has historically been polarized between minimalists and extremists regarding the role and nature of imaging for acute stroke evaluation. Minimalists have argued that noncontrast CT may suffice; yet this approach will no longer work in the endovascular era when presence/ absence and location of arterial occlusion and collateral profile are pivotal. In addition, telemedicine supplant refutes the minimalists’ argument that extra imaging is needless if one does not know how to interpret it. At the other extreme, some insist on the need for physiologically perfect measurements, when recent successful endovascular trials have shown that a sound operational concept is sufficient. These trials, including Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN), Extending the Time for Thrombolysis in Emergency Neurological Deficits–Intra-Arterial (EXTEND-IA), Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times (ESCAPE), and Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment Trial (SWIFT PRIME), used a considerable proportion of CTP. They all demonstrated relatively low rates of hemorrhagic transformation and dramatically improved outcomes with effective reperfusion. These studies follow the success of CTP selection with intravenous thrombolysis in Thrombus Aspiration in ST-Elevation Myocardial Infarction in Scandinavia (TASTE). It is time for both the imaging minimalists and extremists to learn from recent trials rather than perpetuate archaic arguments that impede progress and promote further trials purely for research perpetuation. CTP rapidly provides an accurate measure of ischemic core that simultaneously averts risk of hemorrhagic transformation and potential benefit of reperfusion. Even when chronic collaterals may cause extensive delay in time Computed Tomography Perfusion in Acute Ischemic Stroke Is It Ready for Prime Time?