What you want to do is to use the loft command, but it's not simple or easy. Refer to the 3.5a Matlab Interface document and go to page102 for the "Images, Interpolation, and MRI Data"
On page 105, COMSOL gives an example using the built in MRI data that comes with MATLAB. If you try this, I recommend in step 5 (page 106), that you show your value of k, so you know which kf value needs to be changed. Note, this is indicated by giving you a warning, but the code will continue to run.
And I wish I could give you some advice on steps 7-9, setting up the appropriate el values with the right matrix sizes that are created by the repmat commands... Well, that's how I stumbled onto your question. Let me know if this is old news to you and you've already done this and you could provide some hints!
Note, as of right now, COMSOL 4.0 and 4.0a do not support the loft commands, so this needs to be done in COMSOL 3.5a. Luckily, a document COMSOL posted months ago, said they plan on supporting the loft command when 4.1 comes out... Which should be any day now.
PS, I ran this example on a server license of MATLAB (there was only 1 license). I couldn't get it to work without erroring out at the same line in the example every single time - the error was that there was only one license and it was in use. That required me going to COMSOL's support team.
Anyway, I hope some of this can help you.