Section 18 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; clocks and watches; musical instruments; parts and accessories thereof 90 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; parts and accessories thereof 90 22 APPARATUS BASED ON THE USE OF XRAYS OR OF ALPHA, BETA , GAMMA OR OTHER IONISING RADIA 90 22 12 Computed tomography apparatus Commodity Code Description 90 22 12 00 Computed tomography apparatus