To find out if you are eligable to sit for the ARDMS exam and to get information on the application, go to their website
http://www.ardms.org. This is the certification required by most hospitals here in the U. S. who are hiring ultrasound technologists or sonographers. There is also an ultrasound exam offered by the ASRT but to take that exam you have to be a graduate of an accredited program and I don't think that includes any foreign programs except, perhaps, Canadian ones. The ARDMS has education requirements but has some alternate methods of qualification that might work for you.