 RANDOMISATION: In NOR-SASS-A two step randomisation, 1st randomisation is 1:1 to either tenecteplase TNK or alteplase tPA; 2nd randomisation is 1:1 to either CEST or no CEST. In NOR-SASS-B, randomisation is 1:1 to either CEST or no CEST. In NOR-SASS-C, randomisation is 1:1 to either CES or no CES. 