Simulations of a combined fan-beam and multi-pinhole SPECT system for clinical I-123 DaTscan imaging

We propose an inexpensive method to enhance the resolution and sensitivity of DaTscan imaging for the general-purpose dual-head SPECT systems. DaTscan is a 123I labeled SPECT imaging agent used for diagnosis and monitoring progression of Parkinson's Disease (PD), where the structures of interest, the putamen and caudate are in the central interior portion of the brain. The occipital lobe, located at the rearmost portion of the skull, is also required with PD for calculation of the striatal binding ratio (SBR), a parameter of significance in early diagnosis, differentiation of PD from other disorders with similar clinical presentations, and monitoring progression. A dedicated brain SPECT system with MPH collimators focusing on these specific volumes of interests (VOI) would be an ideal imaging solution to improve the sensitivity and resolution. However, the cost of such a system is likely prohibitive especially considering relatively low amount of procedures performed for brain imaging. Our relatively inexpensive method will use a specifically designed MPH collimator on one detector head providing enhanced spatial resolution/sensitivity for the interior brain, allowing the differentiation of the key brain structures. The fan-beam collimator on the other head will provide lower resolution, but complete sampling of the brain, addressing data sufficiency and allowing SBR calculation over the occipital lobe. We built the proposed SPECT system geometry using the GATE simulation package. To verify the system geometry, we performed GATE and analytic (developed in our Lab) simulations of a cylinder and point source centered in the imaging FOV. We obtained nearly a perfect match between the two simulations. We will continue our investigation with GATE simulations of the XCAT realistic human brain phantom. Optimization of the MPH collimator to enhance the resolution/sensitivity and reduce/model the penetration and an investigation of combined reconstruction methods will follow.