The present invention provides a method and system for determining the position of the image of a target object or the position of the x-ray source in digital tomosynthesis, as the x-ray source is moved relative to the object so as to obtain multiple two-dimensional images of the object from multiple angles. In particular, the present invention provides a method and apparatus for temporarily immobilizing a local area of heart tissue to thereby permit surgery on a coronary vessel in that area without significant deterioration of the pumping function of the beating heart. If the mobile station is capable of accommodating the service option preferred by the base station, a service connect message is sent to the mobile station to initiate toggling of the service option. The device may also include at least a second sensor external to the screen. This reclaimed memory is not made available to the operating system but is rather used as a hardware controlled disk cache to increase system performance. The determined N digits form a number matching a PIN associated with the name of the user, which authenticates the user to access a resource.