Design and fabrication of an anthropomorphic 3D printed thoracic phantom for MyoSPECT validation in obesity imaging

Abstract

Introduction: The primary aim of this study was to create a custom 3D-printed phantom and evaluate the MyoSPECT Myocardial Perfusion Imaging (MPI) system’s ability to image morbidly obese patients. Additionally, the study investigated the use of various fat-tissue replication materials, including Polylactic Acid (PLA) and gelatin-based mixtures, in imaging applications. Methodology: A 3D-printed thoracic anthropomorphic phantom was designed and fabricated to represent a patient with Body Mass Index (BMI) of 45kg/m2. The phantom was developed using a 10% lightning infill, chosen to ensure structural integrity while maintaining anatomical realism. The performance of the MyoSPECT was explored by testing the imaging in both supine and prone positions. Results: The results confirmed that the extended Field of View (FOV) of the MyoSPECT was not sufficient to fully image the left ventricle within the phantom, particularly in the supine position. Prone imaging offered slightly better image uniformity and coverage of the left ventricle, however, some areas of the phantom remained incompletely imaged. In contrast, imaging with conventional Single-photon emission computed tomography (SPECT)/CT provided complete coverage and uniformity, confirming the challenges that MyoSPECT faces when imaging larger patients. The study also explored the use of PLA and gelatin as potential fat-tissue replication materials. Although they could not be directly applied to the printed model, both materials were tested separately for their Hounsfield Unit (HU) values. The results showed that PLA with an 80% infill closely replicates the HU values of adipose tissue, while a 6% gelatin mixture also provided promising results. Conclusion: This research shows that 3D-printed phantoms can be used effectively to investigate performance of imaging systems. The MyoSPECT is unable to adequately image patients with Body Mass Index (BMI) of 45kg/m2 and over. Future research is needed to refine phantom designs and determine the exact cut-off patient dimensions for extended FOV systems.