A prototype portable tomographic system for microwave imaging is presented in this paper as non-destructive testing technique for the full-volume inspection of a work of art, as it can give morphological and physical information on the inner structure of the investigated sample. A custom-made 3D-printed structure has been built to support the antenna elements of the systems and enclose the target being tested. Transmission measurements between pairs of antennas have been acquired through a Vector Network Analyzer connected to a modular switching matrix. Finally, data have been inverted by an open-source reconstruction algorithm to generate the image.