Fisher information analysis of list-mode SPECT emission data for joint estimation of activity and attenuation distribution

Abstract

Inverse Problems 36 (2020) 084002 M A Rahman et al a clinical system using realistic computational studies with 2D digital synthetic and anthropomorphic phantoms. Experiments with anthropomorphic phantoms simulated myocardial perfusion and dopamine transporter (DaT)-Scan SPECT studies. The method was also applied to LM data containing up to secondorder scatter for a synthetic phantom. The results show that the CRB obtained for the attenuation and activity coefficients was typically much lower than the true value of these coefficients. An increase in the number of detected photons yielded lower CRB for both the attenuation and activity coefficients. Further, we observed that systems with better energy resolution yielded a lower CRB for the attenuation coefficient. Overall, the results provide evidence that LM SPECT emission data, including the scatter-window data, contains information to jointly estimate the activity and attenuation coefficients.

A List-Mode OSEM-Based Attenuation and Scatter Compensation Method for SPECT

“…To address this issue, we use the fact that each detected photon traverses through a specific discrete sub-unit of space after being emitted. We refer to this sub-unit as a path [ 13 , 22 ]. For example, in Fig.1 , P1, P2, and P3 denote 3 such paths.…”

“…1 , we can write the log-likelihood of the acquired LM data, denoted by as The term represents the radiation that is transmitted through the path . The expression for this term is given by [ 13 ] where denotes the activity of the starting voxel of the path, . The term is independent of object activity, and models the sensitivity of the path to the detector surface.…”

“…There is much interest in exploring whether uptakes in these regions can help with improved diagnosis of Parkinson’s disease. A 2D clinical SPECT scanner with a geometry similar to the Optima 640 parallel-hole collimator and imaging uptake of Ioflupane (I-131) tracer within the brain was simulated [ 13 ]. Patient anatomy and physiology were modeled using the Zubal digital brain phantom [ 24 ].…”

“…Prior work in PET imaging has shown that using LM data and incorporating energy information led to improved ASC [ 11 , 12 ]. More recently, we observed that SPECT LM emission data containing the energy attribute contains information to jointly estimate the activity and attenuation distributions [ 13 ]. Also, several studies have shown that LM data can yield improved reconstruction and quantification compared to binned data in SPECT imaging [ 14 , 15 , 16 , 17 , 18 , 19 ].…”

“…Existing SPECT reconstruction methods also typically use only the photo-peak (PP) window data for estimating the activity. In this context, recent studies have shown that addition of data from scatter window can provide more information to estimate the activity uptake compared to using data from only the PP window [ 13 , 20 ]. Using data from PP and scatter windows for activity estimation also increases the effective sensitivity of SPECT systems, that otherwise, is typically very low ( < 100 counts/million emitted counts).…”