Combined Multi-Pinhole and Fan-Beam Brain SPECT

Univ Of Massachusetts Med Sch Worcester, Worcester MA

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Abstract

DESCRIPTION (provided by applicant): The recent FDA approval of the SPECT imaging agent I-123 labeled DaTscan for diagnosis and monitoring progression of Parkinson's Disease (PD) has open up a new era in SPECT brain imaging. Unlike with perfusion imaging where the entire brain is the volume of interest, with PD the structures of interest are the putamen and caudate (and potentially substantia nigra) which lie in the interior portion of the brain. However imaging of the occipital lobe is also required with PD for calculation of the striatal binding rati (SBR), a parameter of significance in the early diagnosis and differentiation of PD from other disorders with similar clinical presentations. Our hypothesis is that combining a specifically designed MPH collimator on one detector head with a fan-beam collimator on the remaining head of current dual-headed SPECT systems, coupled with iterative reconstruction with modeling system spatial resolution, will result in improved detection and quantification of structures in the interior region of the brain at marginal cost (the price of collimator(s) and reconstruction software). The MPH collimator would be designed to provide enhanced spatial resolution / sensitivity for the interior of the brain. The fan-beam collimator would provide lower resolution but complete sampling of the brain addressing data sufficiency and allowing a volume-of-interest to be defined over the occipital lobe for calculation of SBR's. Clinically this would provide a low-cost system allowing improved visualization and relative quantification of function of structures in the interior region of the brain, potentially as small as the ~4 mm substantia nigra, which cannot currently be achieved by other than expensive, brain dedicated, SPECT systems. This would greatly impact the early detection and differentiation of PD, and possibly other neurological disorders as new SPECT imaging agents are approved. Our approach for investigating our hypothesis is organized into two specific aims. The first specific aim is to select the MPH collimator designs to be compared under the second specific aim by task-based performance studies, and develop the combined reconstruction of MPH and fan-beam collimators to enable this comparison. The second specific aim is to perform task-based optimization and then comparison of the selected designs based on detection using the Channelized Hoteling Observer (CHO) and quantification of striatal function by calculation of the SBR. Using these task-based criteria we will investigate the trade-off of resolution versus sensitivity by variation in the diameter of the pinholes, and ways to improve sensitivity through judicious usage of not enforcing uniqueness in the portion of the detector irradiated by each pinhole (allowing multiplexing), and curvature of the plate the pinholes are mounted on to bring the lateral and cranial pinholes closer to the patient.