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(Stroke. 2009;40:2875.)
© 2009 American Heart Association, Inc.

Research Letters

Avoiding "Pseudo-Reversibility" of CT-CBV Infarct Core Lesions in Acute Stroke Patients After Thrombolytic Therapy

The Need for Algorithmically "Delay-Corrected" CT Perfusion Map Postprocessing Software

Pamela W. Schaefer, MD; Kit Mui, MD; Shahmir Kamalian, MD; Raul G. Nogueira, MD; R. Gilberto Gonzalez, MD, PhD Michael H. Lev, MD

From the Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston.

Correspondence to Pamela W. Schaefer, MD, Department of Radiology, Division of Neuroradiology, Gray 273A, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114. E-mail pschaefer{at}partners.org

Background and Purpose— Rarely, acute ischemic stroke (AIS) patients have pretreatment CT-CBV abnormalities larger than final infarct volumes. We sought to determine: (1) the prevalence of CT-CBV "reversibility" in AIS patients treated with thrombolytic therapy, and (2) whether the presumed tissue salvage of these CT-CBV lesions depends on the CTP software.

Methods— We reviewed the admission CT-CBV maps (calculated with an algorithm sensitive to tracer arrival time) and follow-up images of 148 AIS patients who received thrombolytic therapy. When the follow-up infarct appeared smaller than the admission CT-CBV lesion, the CTP source images were reprocessed using "delay-correction" software (GE, CTP 4). Original and "delay-corrected" CT-CBV ischemic lesion volumes were compared to each other and follow-up infarct volumes using the Student t test.

Results— 11/148 (7.4%) patients had admission CT-CBV larger than follow-up lesions (mean difference –69.5 cc, range –146.0 to –14.0 cc; P<0.05). For all patients, the admission CT-CBV lesions were smaller on the delay- versus nondelay-corrected maps (mean difference –83.1, range –233 to –2 cc; P<0.05). Only 2 patients had delay-corrected CT-CBV lesions larger than follow-up infarctions, with a 12- to 17-cc difference in volume. 7/9 of the remaining patients had extracranial hemodynamic factors potentially delaying tracer arrival, including atrial fibrillation (AF; n=4), congestive heart failure (CHF; n=4), or extracranial internal carotid artery (ICA) stenosis (n=1).

Conclusion— True "reversibility" of CT-CBV "core" lesions in AIS patients after thrombolytic therapy is rare, with small volumes of "salvaged" tissue. Pseudoreversibility of core lesions in standard CT-CBV maps can be avoided by using specific algorithmically optimized delay-correction software. Further investigation is warranted to determine whether this finding applies to algorithms provided by other vendors.

Key Words: stroke management • CT perfusion