1. A method for use in registering medical images in a medical imaging system, comprising: obtaining a fixed first image; obtaining a second image; down-sampling the first and second images to generate at least one down-sampled image first image and at least one down-sampled second image; registering said first and second down-sampled images to determine a deformation; up-sampling said deformation; and utilizing said up-sampled deformation to register said first and second images.