RESIST-PC: U.S. Academic Foray into PSMA Theranostic Trials.

1438 Objectives: A reproducible and high throughput workflow is often a must when large cohorts of mice need to be scanned. A strategy to increase imaging throughput is to image multiple animals within a single scan. This is particularly helpful when radioactive isotopes with short half-lives are used, when the radiochemical yield or specific activity of new compounds is low or when performing complex dynamic studies with long acquisition times. Furthermore, the total imaging time, and as a result the total operating cost related to the study, can be significantly reduced. In the current study, we evaluate the performance and image quality of a high sensitivity, high resolution PET system (MOLECUBES ꞵ-CUBE) when using a multi-mouse (mouse hotel) bed versus the single mouse bed. Methods: Spatial resolution, sensitivity, uniformity and quantitative accuracy were evaluated on 4 versus 1 imaging position(s) in the mouse ‘hotel’ bed and at a central position in the single animal bed, respectively. The spatial resolution and sensitivity were measured with the NEMA recommended 0.25 mm diameter Na22 point source (20 µCi, 15/12/2011) and the source was positioned at the transaxial and axial center of each quadrant (mouse hotel bed) or in the center of the FOV (single mouse bed) using a robot stage. At each position, spatial resolution (FWHM) was determined by fitting 1D Gaussian profiles through the reconstructed image volume. The sensitivity was calculated as follows: Absolute sensitivity (%)= ((promptshot - delayedhot)-(promptsblank - delayedblank))/(calibrated activity * branching ratio) PET uniformity was assessed by using a uniform cylinder with a diameter of 20 mm. Image uniformity was measured with a 10 mm long volume of interest covering the central 75% of the phantom. Lastly, quantitative accuracy was evaluated on a uniform cylindrical phantom with known activity concentration. Quantitative accuracy was calculated as % deviation from the expected value from the dose calibrator. To demonstrate the in vivo use of the bed, a static 18F-NaF and dynamic 18F-FDG PET/CT scan was performed. In Figure 1 the coregistered CT and PET image can be appreciated, together with the time activity curves of the brain, liver and kidney. All phantom and in vivo data was reconstructed using a 3D OSEM edge preserving noise reduction algorithm using 30 iterations and a voxel size of 400 µm. A general purpose CT scan was done and used for attenuation correction. Results: The phantom results are shown in Table 1. The in vivo results are shown in Figure 1. Image 1: In vivo results. A: static 18F-NaF PET-CT on 4 mice using the mouse hotel. B: Time activity curves of the dynamic 18F-FDG acquisition in 4 mice simultaneously. C: QR code with link to movie of the dynamic acquisition.Discussion: In this study, the performance of the β-CUBE was evaluated when using a mouse hotel vs. a single mouse imaging bed. Thanks to depth-of-interaction capabilities of the single crystal detectors, a uniform sub-mm spatial resolution is achieved across the FOV. Results also demonstrate homogeneous sensitivity, uniformity and quantification accuracy. To conclude, the multi-mouse hotel allows the user to evaluate more animals with one radiosynthesis batch while maintaining imaging quality, hereby increasing the throughput and reducing the overall study cost.