HIPPOCAMPAL MR-IMAGING MORPHOMETRY BY MEANS OF GENERAL PATTERN-MATCHING

PURPOSE: To determine the repeatability and validity of a pattern-matc hing method for the segmentation and measurement of hippocampi on magn etic resonance (MR) images. MATERIALS AND METHODS: Comparable two-dime nsional MR images obtained in 18 subjects (nine healthy control subjec ts [six men, three women; aged 24-54 years] and nine patients with sch izophrenia [six men, three women; aged 22-61 years]) were twice segmen ted manually and twice segmented by using pattern matching with digita l atlas transformation. The atlas transformation was accomplished in t wo steps: global followed by local matching. Global matching was perfo rmed with use of landmarks; local matching was performed with use of a viscous fluid model. RESULTS: The mean percentage of difference betwe en two atlas-based measurements was 1.33% +/- 1.23 (+/- standard devia tion); that between two manual measurements was 4.67% +/- 4.71. The va lidity of the atlas transformation measurements was demonstrated by me ans of the high correlation (intraclass correlation coefficient = .96) with manual segmentation measurements. Schizophrenic hippocampal area s tended to be smaller; however, no differences in hippocampal shape w ere found between patients with schizophrenia and patients with contro l subjects. CONCLUSION: General pattern matching of a digital brain at las to an individual MR image is a mathematically robust method of mea surement that is reproducible and less variable than manual measuremen t.