DETECTION OF SUBTLE BRAIN CHANGES USING SUBVOXEL REGISTRATION AND SUBTRACTION OF SERIAL MR-IMAGES

Objective: The aim of this study was to examine the potential of accur ate image registration for detecting subtle changes in the brain. Mate rials and Methods: Isotropic T1-weighted volume images were obtained i n 10 normal subjects and five patients on two or more occasions (inclu ding pre- and postcontrast studies). The images were segmented and a 3 D rigid body translation and rotation technique was used with sine int erpolation to precisely match the images using a chi(2)-test. The regi stered images and the subtraction images produced from them were used to detect changes in signal intensity, site, shape, and size of the br ain. Results: Small changes due to differences in orientation of the h ead, growth, and development as well as inhalation of oxygen and carbo gen (95% O-2/5% CO2) were observed in normal subjects. Changes were al so observed in patients with minor head trauma, a meningioma, an astro cytoma, and multiple sclerosis. Differences due to contrast enhancemen t and surgery and/or anesthesia were also seen. Conclusion: With use o f subvoxel registration, subtle changes in the brain were detected in a variety of physiological and clinical situations where differences h ave hitherto been difficult or impossible to detect.