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                                                                   Exhibit 10.21



Addendum to Contract with GKF and KMC/WKNI, dated June 1, 1998

27.     Miscellaneous Provisions

D)      Research & Development Treatments

        Per Procedure payments referenced in paragraph 6 shall be waived for
        procedures deemed to be of a research nature. Payments due to GKF are
        based solely on procedures that are presently reimbursed by health
        insurers, Medicare or Medicaid. It is understood by Medical Center that
        procedures deemed to be of research nature shall be performed at such
        time as to not conflict with the scheduling of clinical procedures.

E)      Medical Center shall pay to GKF a per procedure payment of * for the
        first * procedures performed annually. For annual paid procedures in
        excess of *, Medical Center shall pay GKF * for each procedure performed
        in excess of * during the same 12 (twelve) month period. For purposes of
        this payment schedule, the counting of the number of procedures will
        commence from the date of the First Clinical Gamma Knife procedure at
        the Site until the date which is twelve (12) months thereafter (the
        First Reset Date). On the First Reset Date and on each anniversary of
        the First Reset Date, counting of procedures for this purpose will be
        reset and commence from zero (0). Terms are as otherwise specified in
        paragraph 6.

F)      Charity Cases

        As a means to permit Medical Center to perform charity care for a
        persons who require Gamma Knife procedures, who are not covered by
        Medicare or private insurance programs (whether indemnity, preferred
        provider, health maintenance organization, etc.) and who do not have the
        means to pay for such procedures based upon Medical Centers adopted
        standards of indigency, GKF shall waive the per procedure payment
        described in this paragraph 6 for * Gamma Knife procedure for each *
        Gamma Knife procedures performed under this Agreement by Medical Center
        for which a per procedure payment is made to GKF in the manner described
        herein. Medical Center shall be solely responsible (and GKF shall not in
        any manner be or become responsible) (a) whether any person described
        herein requires a Gamma Knife procedure, (b) who shall receive a Gamma
        Knife procedure, hereunder if more than one (1) person described herein
        requires a Gamma Knife procedure, and (2) whether any person meets the
        standards of indigency. Medical Center shall provide reasonable written
        documentation evidencing satisfaction of the conditions set forth herein
        to GKF at or prior to the expected time of payment in order for GKF to
        waive the per procedure payment set forth in paragraph 6.







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G)      Externalities

        The Medical Center is aware that external conditions may exits whereby
        either GKF or Elekta may not be able to deliver a Gamma Knife to the
        designated site in Kettering, Ohio in a timely manner. If delivery is
        not taken by the Medical Center by August 31, 1999 and the failure to
        take delivery of the Gamma Knife is not due to delays caused by
        Kettering Medical Center, this entire lease agreement will be considered
        void, with no further obligations by either party, and each party
        holding the other harmless for any expenses or damages incurred as a
        result of or in anticipation of entering this Agreement.




Medical Center                             GK Financing, LLC



By:  /s/ Frank Perez                       By:  /s/ Craig K. Tagawa
    --------------------------------           --------------------------------
         Frank Perez                                Craig K. Tagawa
         Chief Executive Officer                    Chief Executive Officer