An Improved 3D Printed Cardiac Phantom

391 Objectives: Cardiac imaging has held a place of prominence in the field of nuclear medicine for decades. Cardiac images are acquired with gamma cameras, PET scanners, and dedicated ‘cardio-centric’ systems. The current field of nuclear cardiac imaging instrumentation has a need for a simple to use affordable phantom, which mimics the specific anatomical imaging task. While anthropomorphic cardiac phantoms have existed for some time, they remain difficult to use compared to other widely used phantoms in nuclear medicine. They may also be prohibitively expensive. Additionally, they also provide limited information, due to a small number of structures within the imaged insert. The objective of this study was to develop and test a new cardiac phantom utilizing 3D printing techniques in order to create a low cost, user-friendly, and highly detailed phantom. Methods: A three-dimensional drafting software was used to design the phantom. A stylized left ventricle was generated as a fillable volume with a diameter of 50 mm and a height of 75 mm. Within the myocardial volume, nine objects of varying volume were placed to mimic ischemic lesions. Sets of three lesions were placed 60 degrees apart on their own axial location along the long axis of the left ventricle. The sizes of the ischemic regions were selected to mimic contrast-detail objects to better quantify the limiting detectability of cardiac imaging devices. A larger rectangular container was designed to maintain the ventricle insert at an approximate angle of 25 degrees from the transaxial plane and 45 degrees from the sagittal plane as well as to hold water to mimic torso attenuation. The phantom also has two ports attached at the apex of the ventricle that extends through the outer container which allows for injection access to the left ventricle and the surrounding container’s volume. The entire phantom was 3D printed with PLA filament. Then it was coated with a rubberized sealant spray to ensure watertight surfaces. Once printed and sealed the phantom was filled with water and injected with 0.5 mCi of activity into the ventricle and 0.5 mCi into the surrounding ‘background water’. Finally, it was scanned on a traditional NaI scintillation camera, a multi-pinhole cardio-centric imaging device, and a PET scanner. The reconstructions were conducted per standard clinical protocols and polar maps generated for comparison. Results: The phantom proved effective as a simpler means of cardiac phantom scanning. Compared to other phantoms, it does not require draining, refilling, or reaching into water to remove and inject an insert. The two ports are readily accessible to inject activity into the background and left ventricle which reduces the time handling radioactivity. The overall approximate cost of the printed phantom was found to be less than $250, compared to $2100 for one of the commercially available phantoms. Finally, the acquisition results exposed differences in the detectability between systems. The PET scanner was able to discern all nine lesions from background. The dedicated cardio-centric imaging system was able to discern six lesions. The traditional gamma camera was only able to discern four. Conclusions: A novel cardiac phantom was 3D printed and scanned on three imaging systems. The phantom was found to be easier to implement due to a fixed cardiac insert that does not need removal to fill with activity. The phantom was also found to be more affordable than existing phantoms. Finally, it was able to discern variable performance from three scanners by simply counting the number of visible lesions. The phantom does have some limitations. There is a potential for leaks associated with imperfect 3D printing techniques. Also, the location of the ischemic lesions should be optimized to maximize visibility. The lesions often blur into each other and may obscure visibility of adjacent lesions. Despite these areas of possible improvement, the phantom has shown promise as a tool for quality improvement and benchmarking of the ever-growing field of cardiac imaging devices in nuclear medicine.