A method for operating an inspection system, comprising steps of: (a) moving an item under inspection through a tunnel of rectangular cross-section in a first direction relative to and at least partially between at least one radiation source and at least some radiation detectors illuminated by the at least one radiation source; (b) operating the at least one radiation source and the radiation detectors such that ray paths extending linearly between the at least one radiation source and at least some of the radiation detectors form acute angles with respect to a plane having a normal direction coinciding with the first direction that are substantially in excess of three degrees; and (c) processing data accumulated by the radiation detectors to form a three-dimensional tomographic data image of at least a portion of the item under inspection, wherein: the at least some radiation detectors comprise an L-shaped detector array having segments that span multiple sides of the tunnel; the at least one radiation source comprises at least first and second radiation sources, each radiation source configured and arranged so as to emit a beam of radiation towards the detector array over a different range of angles than the other radiation source, and each radiation source configured and arranged to emit the beam with an angular range such that the beam impinges on all the radiation detectors in the detector array; and the method further comprises: illuminating the radiation detectors with each of the first and second radiation sources; and controlling the first and second radiation sources so that the first radiation source illuminates the radiation detectors during first periods, and so that the second radiation source illuminates the radiation detectors during second periods that are substantially non-overlapping with the first periods. (a) moving an item under inspection through a tunnel of rectangular cross-section in a first direction relative to and at least partially between at least one radiation source and at least some radiation detectors illuminated by the at least one radiation source; (b) operating the at least one radiation source and the radiation detectors such that ray paths extending linearly between the at least one radiation source and at least some of the radiation detectors form acute angles with respect to a plane having a normal direction coinciding with the first direction that are substantially in excess of three degrees; and (c) processing data accumulated by the radiation detectors to form a three-dimensional tomographic data image of at least a portion of the item under inspection, the at least some radiation detectors comprise an L-shaped detector array having segments that span multiple sides of the tunnel; the at least one radiation source comprises at least first and second radiation sources, each radiation source configured and arranged so as to emit a beam of radiation towards the detector array over a different range of angles than the other radiation source, and each radiation source configured and arranged to emit the beam with an angular range such that the beam impinges on all the radiation detectors in the detector array; and the method further comprises: illuminating the radiation detectors with each of the first and second radiation sources; and controlling the first and second radiation sources so that the first radiation source illuminates the radiation detectors during first periods, and so that the second radiation source illuminates the radiation detectors during second periods that are substantially non-overlapping with the first periods. illuminating the radiation detectors with each of the first and second radiation sources; and controlling the first and second radiation sources so that the first radiation source illuminates the radiation detectors during first periods, and so that the second radiation source illuminates the radiation detectors during second periods that are substantially non-overlapping with the first periods.