Evaluation of early reperfusion and IV tPA therapy using diffusion- and perfusion-weighted MRI

Objective: To characterize the effects of recombinant tissue plasminogen ac tivator (rt-PA) therapy and early reperfusion on diffusion-weighted (DWI) a nd perfusion-weighted imaging (PWI) changes observed following acute ischem ic injury. Methods: Twelve patients were evaluated prospectively using echo planar DWI and bolus tracking PWI. Six patients received IV rt-PA 0.9 mg/k g and were compared with six patients who did not. Patients receiving rt-PA were initially imaged (T1) 3 to 5 hours postictus (mean, 4 hours 20 minute s)whereas those not treated with tissue plasminogen activator (tPA);were im aged 4 to 7 hours postictus (mean, 5 hours, 25 minutes), Follow-up imaging was performed 3 to 6 hours (T2), 24 to 36 hours (T3), 5 to 7 days (T4),and 30 days (T5) after the first:scan in all patients. Lesion volumes were meas ured on both DWI and time-to-peak maps constructed from PW images. Results: PWI was performed successfully at T1 and T3 in 11 of 12 patients. In the g roup that received IV tPA, initial PT;VI volumes were less than DWI volumes in five of six patients (83%), whereas only one of five patients (20%) not receiving tPA had PWI ( DWI volume (p = 0.08). PWI normalized by 24 to 36 hours (T3) in 6 of 11 patients (early reperfusers), with 5 of 6 of these ea rly reperfusers having received tPA. The aggregate: apparent diffusion coef ficient ADC) values for the early reperfusers were consistently higher at T 2 (p = 0.04), T3 (p = 0.002), and T4 (p = 0.0005). Five of six patients wit h early reperfusion demonstrated regions of elevated ADC within, the ischem ic zone (mean ipsilateral ADC/contralateral ADC, 1.46 +/- 0.19) by 24 to 36 hours, whereas none of the nonearly reperfusers showed these regions of el evated ADC (p = 0.015). Conclusion: Early reperfusion is seen more frequent ly with IV tPA therapy. In addition, the study showed that ADC may undergo early increases that are tied closely to, reperfusion and marked ADC hetero geneity may exist within the same lesion; Early reperfusion is seen more fr equently with IV tPA therapy.