Parse it in chunks: 功能 (function) + 磁共振 (magnetic resonance) + 成像 (imaging) + 术 (technique). Drop the 功能 prefix and you get plain MRI: 磁共振成像.
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Specialist medical/scientific term. In casual writing the English abbreviation fMRI is increasingly used directly; the full Chinese form appears in academic papers, textbooks, and formal news.
