An apparatus is provided for positioning a sample in the radiation field of a computerized axial tomographic scanner (CAT) for scanning by the CAT. The apparatus has a first support on a first side of the CAT and a second support on a second side of the CAT opposite the first side of the CAT. Both supports have respective guides and respective trolleys mounted upon their guides. The trolley on the first support is coupled to the second trolley by a suitable coupling so that movement of the first trolley by its motor causes similar movement of the second trolley, and the coupling with a sample mounted thereon passes through the radiation field of the CAT. A controller controls the motor to correctly position the sample as determined by a sample position sensor.