Doppler imaging uses ultrasound, not MRI.
It works by sending ultrasonic (too high frequency to hear) sound waves through your body, and measuring the reflections. Normal ultrasound can determine the distance traveled by the reflected sound, and thus create a picture of what's inside. Doppler ultrasound also looks at the frequency of the reflections, which lets it figure out the velocity of whatever it was that reflected the sound. Thus, Doppler ultrasound shows the location and structure of your veins, and the direction and speed of blood flow.
Doppler ultrasound is not widely available, so people are exploring ways to use other imaging, such as MRI, to identify vein abnormalities. I believe the Buffalo study is using a special MRI protocol (SWI MRI) that is sensitive to iron deposits, which are thought to be strongly correlated with venous blockage.
Bottom line, MRIs aren't actually the preferred means to test for CCSVI right now, so your inability to get an MRI isn't a show-stopper, at least for CCSVI assessment.