Dedicated 3D-Printed Radioactive Phantoms With ¹⁸F-FDG for Ultrahigh-Resolution PET

This study explores the potential of digital light processing to 3-D print radioactive phantoms for high-resolution positron emission tomography (PET). Using a slightly modified desktop 3-D printer and mixtures of 18F-FDG (T1/2: 109.8 min) and photopolymer resin, we have printed standardized and custom radioactive objects designed for ultrahigh-resolution PET, also as a first step toward complex geometries. The phantoms were: a flood source to assess uniformity, a two-point phantom for spatial resolution assessment, a multiline phantom for validating submillimeter printing resolution, a fish-like phantom with different activity concentrations, and a 50%-downscaled micro-PET image quality phantom (National Electrical Manufacturers Association NU 4-2008). Positron range effects were examined on the latter using a removable cover. The evaluation relied on planar images from a phosphor imager and tomographic images from a commercial small animal PET scanner. We were able to print radioactive uniform distributions with relative standard deviation below 4.5% and structures as small as 0.3 mm. Our two-point phantom outperformed a commercial one in terms of peak difference (6% versus 72%) and peak-to-valley ratio (75.3 versus 14.1). The fish-like phantom shows that printing hot regions and air cavities onto a uniform background is feasible. Future steps include using longer-lived radionuclides like 89Zr and 22Na.