The sample size calculation for the French patients has been performed for the primary objective of OPHELIE assuming an expected difference of 5% for the primary end-point with alpha and beta risks of 5% and 20% respectively and a expected proportion of patients with a mRS score 0-1 of 40% at month-3, according to trials, observational registries and data published in the Lille centre for a baseline NIH score of 11: 900 patients will be necessary. To detect an absolute difference of 10 % for the primary end-point with an alpha risk of 5% and a power of 80%, a sample size of 1040 eligible patients is necessary, assuming that 12 to 16% of patients will have criteria for pre-existing dementia. This 10% absolute difference in the proportion of patients with mRS 0-1 at month 3 between those with and without pre-existing dementia corresponds to the difference below which the beneficial effect of rt-PA may be lost, taking into account that approximately 30% of patients under placebo, and 40% under rt-PA have a mRS 0-1 at month 3 for a median baseline NIH score of 11. Assuming that 20% of patients included in OPHELIE will not be eligible for OPHELIE-COG according to the proportion of exclusions found in previous studies with the IQCODE, we can expect a recruitment of 720 patients in the French arm of the study. The 320 other patients will be recruited in Japan, meaning that 400 patients have to be recruited to compensate the usual 20% rate of patients who cannot have an IQCODE in due time.