Design and manufacture of a radioactive 3D printed phantom for PET quality control

It is proposed to incorporate radioisotopes into the resin material of 3D-printers to facilitate the production of complex phantoms for PET quality control. This project aimed to demonstrate this possibility by producing a lesion detection phantom with associated software for PET image evaluation and optimisation.

80 MBq of ⁸⁹Zr were added to the support resin of an Objet30-Pro 3D-printer and printed alongside the build resin to create a bespoke phantom with a heterogeneous activity distribution. The phantom contained 40 radioactive cylinders ranging from 1.3 to 13.9 mm in diameter. The lesion to background activity concentration varied down the length of the phantom at ratios of 3:2, 2:1, 4:1, 8:1 and 1:0. Imaging was performed using a list mode acquisition on a Siemens Biograph-mCT PET/CT scanner. Reconstructions were performed using a subset of the data, representing acquisition durations ranging from 5 s to 1 h, with and without point spread function (PSF) modelling. Receiver operator characteristic analysis was conducted and the area under the curve calculated to quantify image quality.

The phantom took 96 h to manufacture and was produced with suitable print quality, matching the original design specification. Differences in image quality, due to acquisition duration, image contrast and PSF modelling were quantified. The testing approach was also shown to be repeatable in a test-retest scenario, demonstrating the usefulness of such phantoms for image evaluation and quality control.

Radioactive 3D printing is a promising tool and could be utilised for the manufacture of PET QC phantoms.