Evaluation of the Small-animal Nano Scan PET/CT System using Zr.

Introduction: The purpose of the present work was to evaluate the imaging characteristics of Zr-PET in comparison with those obtained using fluorine-18 Fluorodeoxyglucose (18FFDG) PET (a gold standard tracer in PET imaging) using a small-animal NanoScan PET/CT scanner.

Methods: The system's spatial resolution, sensitivity, uniformity, and image quality were measured on a Nano Scan small-animal PET/CT scanner according to the NEMA NU4-2008 protocols. For reconstruction images, we used 2D and 3D reconstruction algorithms. The reconstruction methods included filter back projection (FBP), the ordered subsets expectation maximization (OSEM) algorithm, and the 3D Tera-Tomo algorithm, which are developed for the NanoScan small-animal PET/CT scanner.

Results: The results obtained showed a significant difference in the spatial resolution for Zr as compared to 22Na and 18F when using a 2D reconstruction algorithm. The spatial resolution values were much enhanced by using the 3D Tera-Tomo reconstruction for each isotope, the Full width at half maximum (FWHM) values was less than 1 for all isotopes at the center of the field of view (FOV). This difference in spatial resolution is dependent on the positron range, energy, and the reconstruction method.

Conclusion: The long half-life of Zr makes it an ideal positron emitter for performing immuno- PET, which is matched with the biological half-life of intact mAbs.Zr can also give several advantages over other long half-life positron emitters in relation to the overall imaging performance because of its relatively short positron range and simpler decay scheme. The values of Zr sensitivity that were obtained in the present study were less than those of previous studies.