Combined high speed backprojection and forward projection processor for

Abstract

A CT scanner (10) generates views of data such as equal angular increment detector fan views (FIG. 2A) which are convolved or filtered by an array processor (24). A combined backprojector and forward projector (28) backprojects the data from the array processor into an output memory (30) and forward projects lines of image representation data from an input memory (26) to the output memory. Each view representation may again be an equal angular increment detector fan format view (FIG. 2A), a parallel ray format view (FIG. 2B), an equal linear increment source fan format view (FIG. 2D), a source fan format view (FIG. 2C), an equal angular incremental detector fan format (FIG. 2E), an equal linear increment detector fan format (FIG. 2F), or an equal angular increment source fan format (FIG. 2G). In a backprojector mode, the projector is addressed by line and row addresses of a pixel of the output memory. A look-up table (76) and a multiplier (82) generate a weighting function W. A multiplier (78 ) and an adding means (80) along with the look-up table convert the memory addresses into an appropriate address for a line of view data stored in a projector memory (60). An element of view data retrieved in response to the received address is multiplied (84) by the weighting function. In a forward projector mode, a parallel ray forward projection configuration (92) is provided. A view format transform assembly (90) transforms other format view designations and addresses into the corresponding parallel ray format view designations and addresses.