Theoretical analysis of full-ring multi-pinhole brain SPECT

Abstract

Presently used clinical brain SPECT suffers from limited spatio-temporal resolution. Here we investigate the feasibility of high-resolution and highsensitivity full-ring multi-pinhole brain SPECT (MP-SPECT). Using an analytical model we optimized pinhole-detector geometries of MP-SPECT for different detector intrinsic resolutions R i . System resolution and sensitivity of optimized MP-SPECT were compared to conventional clinical SPECT. The comparison of the system resolution of different systems was done at matched sensitivity, which was achieved by tuning pinhole diameters. Similarly, sensitivities were compared at matched system resolution. For MP-SPECT that uses detectors with intrinsic resolutions of 4 mm > R i 0.5 mm a sensitivity can be achieved that is 6.0 times higher than the sensitivity of conventional dualhead SPECT systems with parallel-hole collimators (DualPar), while system resolution can be improved by a factor of 2.4. To achieve these improvements a large detector-to-collimator distance is needed. In contrast, for detectors with intrinsic resolutions < 0.2 mm, it is beneficial to place the detectors close to the pinholes, resulting in a high number of de-magnified projections. For a detector intrinsic resolution of 0.05 mm, a 14.5-fold improvement in sensitivity and a 3.8-fold improvement in system resolution compared to DualPar is predicted. Furthermore, we found that for optimized MP-SPECT the sensitivity scales proportionally to system resolution squared, with the proportionality constant depending on R i . From our sensitivity-system resolution trade-off equations we deduced that MP-SPECT with an ideal detector (R i → 0) can have a system resolution that is 2.0 times better than optimized MP-SPECT with a conventional detector (R i 3 mm). The high performance of optimized MP-SPECT may open up completely new molecular imaging applications.

An enhanced high-resolution EMCCD-based gamma camera using SiPM side detection

“…Rogulski et al (1993), Beekman and Vastenhouw (2004), Meng et al (2006), Rentmeester et al (2007), Shokouhi et al (2009) and Goorden et al (2009); recent work by Meng et al (2009a) validates the efficacy of high-resolution detectors in small-animal SPECT applications. High-resolution gamma-ray detectors have been developed for applications ranging from astronomy and particle physics to biomedical imaging.…”

Theoretical Bounds and System Design for Multipinhole SPECT

“…To see the effect when this is not the case, we introduce the rate of oversampling, , to denote the ratio of the magnified geometric resolution to the intrinsic resolution, defined as (22) In combination with (1) we obtain (23) Inserting this expression in (19), we find that, for a fixed rate of oversampling, the upper bound of the sensitivity is reduced with a factor of resulting in (24) For example, a rate of oversampling of reduces the maximum sensitivity with a factor of 0.5, with a factor of 0.8, with a factor of 0.9, and so on. Another study, [25], concurrent with ours, derives the maximum sensitivity while incorporating the effects of penetration in the pinhole knife edge, in the context of brain SPECT. Through an approximation using a first-order Taylor expansion they identify two regimes, one for low-resolution and one for high-resolution detectors.…”

Design and performance of a compact and stationary microSPECT system

“…Others have published 95 multi-pinhole SPECT optimization procedures for human brain imaging [16]. System optimization in these references is performed according to figure 2, assuming that the detector surface can be represented by a sphere.…”

“…This 40 means that smaller detectors can be used and as a consequence, more pinhole-detector pairs can be placed in the same space. On a system level, this can finally result in better sensitivity for equal spatial resolution [16]. In our lab, we are constructing a prototype system that exploits this principle, not to improve system performance, but to enable small, low cost and stationary microSPECT imaging at uncompromised performance.…”