Comparison and evaluation of rigid, affine, and nonrigid registration of breast MR images

Purpose: A new nonrigid registration method, designed to reduce the effect of movement artifact in subtraction images from breast MR, is compared with existing rigid and affine registration methods. Method: Nonrigid registration was compared with rigid and affine registrati on methods and unregistered images using 54 gadolinium-enhanced 3D breast M R data sets. Twenty-seven data sets had been previously reported normal, an d 27 contained a histologically proven carcinoma. The comparison was based on visual assessment and ranking by two radiologists. Results: When analyzed by two radiologists independently, all three registr ation methods gave better-quality subtraction images than unregistered imag es (p < 0.01), but nonrigid registration gave significantly better results than the rigid and affine registration methods (p < 0.01). There was no sig nificant difference between rigid and affine registration methods. Conclusion: Nonrigid registration significantly reduces the effects of move ment artifact in subtracted contrast-enhanced breast MRI. This may enable b etter visualization of small tumors and those. within a glandular breast.