The Effect of a Partial Shoulder PET Ring in the NeuroEXPLORER Design

Abstract

The NeuroEXPLORER design has been proposed as the next generation human brain PET system to support non-invasive, quantitative brain imaging at very high spatiotemporal resolution and sensitivity that cannot be achieved by any existing commercial or research prototype systems such as the HRRT. A long axial field-of-view (FOV) and small bore size is essential to achieve high angle of acceptance and sensitivity. However, the brain cannot be placed in the center of FOV in long systems with small apertures. To position the brain in the center of the FOV, a partial shoulder ring (the 6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> ring) was designed, with 5 other complete rings. This design allows us to put brain in the axial FOV center for best sensitivity performance. Analytical simulations using the XCAT phantom was carried out to investigate sensitivity, and image artefacts. Three difference settings were simulated. In the first one, full shoulder ring out was included and the brain was put in the center FOV to simulate the best possible scenario. In the second setup, partial shoulder ring was used with the brain in the center FOV to simulate the outcome of the design. In the third setup, full shoulder ring were added and the shoulder region was excluded in the FOV, which also made the brain off center. This stands for the real scenario without should cutoff. Both noise free and noisy (10 seconds) scans were simulated and reconstructed. The reconstructed noise-free images showed that with shoulder cut-offs in the partial shoulder ring, significant image difference is present in the shoulder region, but minimal image difference is observed in the brain region or carotid artery region. In noisy simulations, increased noise was observed in cases where brain was off-center due to the size of shoulders. In this study, we showed that the shoulder cut-off design was the best trade-offs to provide a high sensitivity brain PET system in current NX design framework.