Abstract: In combination with a diagnostic CT scanner using radiant energy for imaging, an apparatus for therapeutically irradiating a target, comprising a mask that partially attenuates the radiant energy passing therethrough, but transmits through an aperture sufficient radiant energy for imaging. The mask, intermediate the radiant energy source and the target, passes an unattenuated portion of the radiant energy to irradiate the target. The cross-sectional shape and spatial position of the mask aperture can be selectively varied. A post-mask is aligned with the mask aperture and attenuates the radiant energy passing therethrough to an energy level essentially uniform with that of the radiant energy passing through the mask to permit continued imaging during therapeutic irradiation of the target. A method of using the invention in combination with a diagnostic CT scanner using radiant energy for imaging is also provided.

Abstract: A system for creating and modifying strings of symbols in a computer storage apparatus includes a two-part cursor for guiding the operator. One cursor part indicates the exact location where entered symbols will be inserted. A second cursor part highlights a selected substring which is the object of certain commands, such as the delete command. Internally, the system provides memory management techniques for inserting and deleting symbols in response to operator commands. The display, including the two-part cursor, is derived from the memory contents with the aid of pointers, tables, and state variables.