definiens: ( as defined below ) for each that is performed by Medical Center or its representatives or affiliates, whether on an inpatient or outpatient basis, and irrespective of whether the Procedure is performed on the Equipment or using any other equipment or devices ', including but not limited to any ( defined below ) . Notwithstanding the foregoing, and for the avoidance of doubt, if at any time in addition to the Equipment, Medical Center purchases, leases or otherwise acquires from any third party the use of a Leksell Gamma Knife unites ) of any model type or configuration ( an ), then, in addition to the Purchased Services Payments that are payable to GKF for Procedures performed using the Equipment as set forth above, Medical Center shall pay to GKF the Purchased Services Payments on a monthly basis for any and all Procedures performed using the Additional GK Leksell Unit, and/or any other equipment or devices, whether on an inpatient or outpatient basis . The parties acknowledge that the Purchased Services Payments represent fair market value for the use of the Equipment as described in this Agreement . As used herein : ( i ) means any treatment that involves stereotactic, external, single fraction, conformal radiation, commonly called radiosurgery, that may include one or more isocenters during the patient treatment session, delivered to any site(s ) superior to the foramen magnum . shall expressly exclude ( 1 ) any procedures which the Equipment is unable to perform or which, in the opinion of Elekta, the Equipment is not designed or reasonably suitable to perform ; and/or ( 2 ) any fractionated procedures for a single tumor involving more than a single fraction ( commonly called fractionated stereotactic radiotherapy ) where such fractionated treatment is medically indicated