Evaluation of image reconstruction for mouse brain imaging with synthetic collimation from highly multiplexed SiliSPECT projections

Abstract

We have performed a theoretical study to explore the potential and limitations of synthetic collimation for SPECT imaging with stacked detector acquisition (dual magnification). This study will be used to optimize SiliSPECT, a small-animal SPECT for imaging small volumes such as mouse brain at high sensitivity and resolution. The synthetic collimation enables image reconstruction with a limited number of camera views and in the presence of significant multiplexing. We also developed a new formulation to quantify the multiplexed object sensitivity and investigated how this changes for different acquisition parameters such as number of pinholes and combinations of front and back detector distances for imaging objects as large as a mouse brain. In our theoretical studies, we were not only able to demonstrate better reconstruction results by incorporating two detector magnifications in comparison to either alone, but also observed an improved image reconstruction by optimizing the detector-collimator distances to change the multiplexing ratio between the front and back detectors.

Design and performance of a small-animal imaging system using synthetic collimation

“…The system described in this work uses the technique known as synthetic collimation which combines multiplexed and non-multiplexed data to produce high-resolution, artefact-free reconstructions (Wilson et al 2000). By combining images of an object at different magnification factors it has been shown in simulations (Wilson et al 2000, Shokouhi et al 2010, Mahmood et al 2010), and experimentally with a slit-slat collimator (Mahmood et al 2011), that the effect of multiplexing can be removed. The data contain information on how the projections overlap which enables us to reconstruct the object using maximum-likelihood estimation (Wilson et al 2000).…”

Reducing Multiplexing Artifacts in Multi-Pinhole SPECT With a Stacked Silicon-Germanium System: A Simulation Study

“…The percentage of multiplexing for each data set was determined using the method of Shokouhi et al [11], in which the sum of counts in detector pixels contributed by projections through more than one pinhole is divided by the total number of counts in the projection. The percent of multiplexing for each detector’s projection, pinhole, and object combination is shown in Table I, when the Si detector’s pixel dimensions were 512 × 512.…”

“…This concept has been demonstrated in previous simulation work in our lab using a limited-angle stacked Si detector design [11, 12]. This concept has also been demonstrated experimentally in a limited-angle small-animal system with 46 pinholes where the detector is moved to allow data collection at multiple focal lengths [13].…”

Advances in Preclinical SPECT Instrumentation

“…This approach is known as synthetic collimation and involves the acquisition of pinhole projection data at multiple magnifications (Figure 1) (8, 9). The basic concept behind the synthetic-collimator approach is to combine lower-resolution data containing little (or no) multiplexing with higher-resolution data that is more highly multiplexed.…”