DWI was performed with a spin echo-echoplanar imaging sequence (field of view=240 mm, repetition time=5 seconds, echo time=minimum allowed, slice thickness=5 mm, number of slices=19, slice gap=1 mm, acquisition matrix=128×128) and lesion volumes determined by a semiautomated thresholding algorithm, which identified regions of high signal intensity that exceeded a region in the contralateral frontal lobe by >3 standard deviations. Dynamic susceptibility PWI was performed with gradient echo- echoplanar imaging (field of view=240 mm, repetition time=2 seconds, echo time=60 ms, slice thickness=7 mm, number of slices=12, slice gap=0, acquisition matrix=128×128, dynamic scans=40), and maps of the time to peak of the residue function (ie, Tmax) were generated by deconvolution of the tissue concentration over time curve with use of an arterial input function from the contralateral middle cerebral artery. The prespecified Tmax delays used to quantify the hypoperfusion on PWI were >2, >4, >6, and >8 seconds. Perfusion/diffusion mismatch was defined as a PWI lesion that was 10 cm3 larger and ≥120% of the DWI lesion volume. The “no mismatch” profile was defined as a PWI volume <120% of DWI. The “small lesion” profile was defined as baseline DWI and PWI volumes that were both <10 cm3. The “malignant” profile was defined as DWI or Tmax >8 seconds lesion volume >100 cm3. The mismatch patients without a malignant profile were classified as “target mismatch.” Early reperfusion was defined on the basis of a PWI scan performed 4 to 6 hours after initiation of intravenous tPA therapy. A PWI volume that was at least 30% less than the initial PWI volume qualified as reperfusion.
For the current substudy, we redefined the perfusion/diffusion mismatch groups according to 4 prespecified Tmax thresholds (>2, >4, >6, and >8 seconds). Penumbra salvage and infarct growth were calculated for each patient. Penumbra salvage was defined as the difference between baseline PWI lesion and final infarct volumes from each of the 4 Tmax thresholds. Infarct growth was defined as the difference between baseline DWI lesion and final infarct volume. The presence or absence of early reperfusion (a >30% reduction in PWI volume) was determined for each patient from each of the 4 prespecified Tmax thresholds) as previously described.8 (link) Patients with the small-lesion profile (n=18), those with technically inadequate initial (n=9) or early follow-up (n=3) PWI imaging results, and patients missing 30-day follow-up scans (n=11) were excluded from this substudy.
For the current substudy, we redefined the perfusion/diffusion mismatch groups according to 4 prespecified Tmax thresholds (>2, >4, >6, and >8 seconds). Penumbra salvage and infarct growth were calculated for each patient. Penumbra salvage was defined as the difference between baseline PWI lesion and final infarct volumes from each of the 4 Tmax thresholds. Infarct growth was defined as the difference between baseline DWI lesion and final infarct volume. The presence or absence of early reperfusion (a >30% reduction in PWI volume) was determined for each patient from each of the 4 prespecified Tmax thresholds) as previously described.8 (link) Patients with the small-lesion profile (n=18), those with technically inadequate initial (n=9) or early follow-up (n=3) PWI imaging results, and patients missing 30-day follow-up scans (n=11) were excluded from this substudy.
