Abstract
Purpose: Phantoms are routinely used in molecular imaging to assess scanner performance. However, traditional phantoms with fillable shapes do not replicate human anatomy. 3D printed phantoms have overcome this by creating phantoms which replicate human anatomy which can be filled with radioactive material. The problem with these is that small objects suffer from boundary effects and therefore boundary-free objects are desirable. The purpose of this study was to explore the feasibility of creating resin-based 3D printed phantoms using 18 F-FDG. Methods: Radioactive resin was created using an emulsion of printer resin and 18 F-FDG. A series of test objects were printed including twenty identical cylinders, ten spheres with increasing diameters (2 mm to 20 mm) and a double helix. Radioactive concentration uniformity, printing accuracy and the amount of leaching were assessed. Results: Creating radioactive resin was simple and effective. The radioactivity remained bound to the resin for the duration that it was radioactive. The radioactive concentration was uniform among identical objects; the CoV of the mean, max and total signal were 3.6%, 3.8% and 2.6%, respectively. The printed cylinders and spheres were found to be within 4% of the model dimensions. A double helix was successfully printed as a test for the printer and appeared as expected on the PET scanner. The amount of radioactivity leached into the water was measurable (0.72%) but not visible above background on the imaging. Conclusions: Creating an 18F-FDG radioactive resin emulsion is a simple and effective way to create boundary-free, accurate, complex 3D phantoms that can be imaged using a PET/CT scanner. This technique could be used to print clinically realistic phantoms, however, they are single use, and cannot be made hollow without an exit hole. Also, there is a small amount of leaching of the radioactivity to take into consideration.
Optimizing reconstruction parameters for quantitative 124I-PET in the presence of therapeutic doses of 131I