Tomographic imaging system

A tomographic imaging system comprising: generating means for generating penetrating radiation toward an object under investigation; detecting means including an array of radiation sensitive detectors for detecting the radiation from said generating means transmitted through the object and for providing an output indicative thereof, said detecting means including at least one side of said detector array of radiation sensitive detectors, a checking detector being responsive to the radiation generated by said generating means which normally does not pass through the object under investigation for checking whether the object is positioned within a field of view of said detector array of radiation sensitive detectors, said checking detector providing an output indicative of the radiation generated which normally does not pass through the object; means for comparing the output of said checking detector with a predetermined value for determining whether the object is positioned within the field of view of said detector array; means for rotating said generating menas and said detecting means while keeping a predetermined relative relationship in position with respect to each other; and means for processing the output form said detector array to produce a tomographic image of the object