FACTOR-ANALYSIS OF MEDICAL IMAGE SEQUENCES IN MR OF HEAD AND NECK TUMORS

PURPOSE: To evaluate factor analysis of medical image sequences (FAMIS ), a means whereby physiologic contrast enhancement kinetics, called f actors, and their spatial distribution, termed factor images, are esti mated after acquisition of dynamic MR images. The method is intended t o recognize and characterize the different tissue kinetics automatical ly. METHODS: This method was evaluated in a series of 22 patients with head and neck tumors. Eleven patients presented with a previously unt reated lesion. Six were examined for tumor recurrence, previously trea ted by multiple therapies. Five patients had preoperative chemotherapy and underwent MR before and after chemotherapy. In all cases, MR imag es were correlated with surgical and pathologic data. MR examinations were performed on a 1.5-T unit with static sequences and dynamic seque nces acquired after bolus injection of gadolinium and processed by FAM IS. RESULTS: FAMIS was able to identify three factors representing con trast-enhancement kinetics and their associated factor images. The neo plastic component was associated with the earlier factor image, Fl. Fi brosis and chemotherapy and/or radiation-induced changes were associat ed with the two later factors, F2 and F3. The limits of this method we re highly vascularized tissues whose earlier factor was similar to tha t of neoplastic tissues (mucosae and salivary glands), patient motion, responsible for artifacts in FAMIS, and lesions of less than 5 mm. CO NCLUSION: FAMIS of dynamic MR studies was useful for differentiating n eoplastic tissue from tissue having undergone changes by chemotherapy and/or radiotherapy, but it did not improve the ability of MR to chara cterize neoplastic tissues in previously untreated patients.