Determine World Coordinates for image resampling

Hello. I want to determine the World Coordinates (x,y) of the pixels of DICOM image No.1. Having them, I want to create a new image by determining the value of the pixel from DICOM image No.2 at the same World Coordinates (x,y) by interpolating the neighbours values. My question is:

How can I get the World Coordinate of any pixel in a DICOM image? I'm running MATLAB R2009b , so

 >>imref2d() or imref3d()

does not work...

Thank you for helping, DB