capabilities. MRI is also useful for planning subsequent treatments, if needed.

12.2.7\ Endovascular Reconstructive Treatment for Acute Ischemic Stroke Using Intra-arterial Thrombolysis or Embolectomy

Various catheter-based devices and techniques have been devised for clot removal from the cerebral arteries. Some of these include the use of a snare, the alligator retrieval system, the Phenox clot retriever, the Merci catheter, and the Penumbra and stent retrievers among others (Fig. 12.51). Angiographic imaging can confirm successful recanalization following mechanical thrombectomy or intra-arterial thrombolysis

(Fig. 12.52). Following successful embolectomy or thrombolysis, patients are at risk for reperfusion hemorrhage, which occurs in an estimated 5–10% of patients. Edema due to infarction peaks at approximately 72 h following the procedure, whereas edema due to hemorrhage may take a week to reach its peak. Patients are at risk for herniation during this time. Imaging can be used to evaluate the extent of infarction, reperfusion edema, and hemorrhage. Potential complications from embolectomy that can be visible on cerebrovascular imaging include intraprocedural hemorrhage, vessel rupture, and vessel dissection. Potentially confounding is the frequently encountered extravasation of contrast into areas where there has been breakdown of the blood-brain barrier. Residual contrast staining from the procedure due to blood-brain barrier leakage in infarcted

Fig. 12.52  Mechanical thrombectomy. Pre-procedure axial CTA MIP image (a) shows complete occlusion of the left distal M1 (encircled). Post-procedure CTA MIP

image (b) shows interval patency of the left M1 with minimal residual irregularity

Fig. 12.53  Retained contrast in infarcted parenchyma. Axial CT image obtained 18 h following embolectomy (a) shows hyperattenuation within the left basal ganglia. Axial CT image obtained 24 h later (b) shows that the

hyperattenuation has nearly cleared and instead there is hypoattenuation due to edema from infarction in the left basal ganglia

Fig. 12.54  Retained contrast and dual energy CT. Axial (a) CT image at 120 keV obtained after mechanical thrombectomy shows a hyperattenuating area in the right

insula (arrow). The corresponding iodine overlay image (b) confirms the presence of contrast (Courtesy of Rajiv Gupta, M.D., Ph.D.)