EXHIBIT 21 4-D NEUROIMAGING LIST OF SUBSIDIARIES SEPTEMBER 30, 2000 Jurisdiction Percentage of in which Voting Securities Name Incorporated Owned by Parent Biomagnetic Technologies GmbH (A) Germany 100% Neuromag Oy (B) Finland 100% (A) The subsidiary changed its name in October 1991. It was formerly known as S.H.E. Kryotechnische Instrumente und Systeme GmbH. Substantially all assets and liabilities of the subsidiary were transferred to Biomagnetic Technologies, Niedelassung, a branch of 4-D Neuroimaging on October 1, 1997. (B) The company was acquired in December 1999.