Radiographic gantry with software collision avoidance

Claim 1

A multi-axis radiographic system comprising: (1) a radiation source and detector; (2) an arm supporting at least one of the radiation source and detector and movable within movement limits to arm positions in at least two dimensions; (3) a patient support adapted to position a patient with respect to the arm; (4) an operator input device providing command signals to initiate movement of the arm along a movement dimension from a current arm position; (5) an electronic computer communicating with the arm so as to determine the arm position and to provide motion signals for moving the arm between arm positions, the electronic computer having a memory storing: (a) a legal space table that relates arm positions, within the movement limits of the arm, to one of a contacting and non-contacting state, the contacting state corresponding to one of movement limits and arm positions where there is a high risk of contact between one of the arm, radiation source and radiation detector, and one of the table and patient, and non-contacting states being other arm positions; and (b) a program for controlling the electronic computer so as to: (i) receive command signals from the operator input device indicating a movement dimension; (ii) search the legal space table from the current arm position through arm positions along the movement dimension until a first arm position related to a contact state is found, the first arm position being designated a soft limit; and (iii) provide movement signals to the arm to move the arm in the movement dimension only so long as the current arm position is before the soft limit.