Assessment of a fully 3D Monte Carlo reconstruction method for preclinical PET with iodine-124

Abstract

Iodine-124 is a radionuclide well suited to the labeling of intact monoclonal antibodies. Yet, accurate quantification in preclinical imaging with I-124 is challenging due to the large positron range and a complex decay scheme including high-energy gammas. The aim of this work was to assess the quantitative performance of a fully 3D Monte Carlo (MC) reconstruction for preclinical I-124 PET. The high-resolution small animal PET Inveon (Siemens) was simulated using GATE 6.1. Three system matrices (SM) of different complexity were calculated in addition to a Siddon-based ray tracing approach for comparison purpose. Each system matrix accounted for a more or less complete description of the physics processes both in the scanned object and in the PET scanner. One homogeneous water phantom and three heterogeneous phantoms including water, lungs and bones were simulated, where hot and cold regions were used to assess activity recovery as well as the trade-off between contrast recovery and noise in different regions. The benefit of accounting for scatter, attenuation, positron range and spurious coincidences occurring in the object when calculating the system matrix used to reconstruct I-124 PET images was highlighted. We found that the use of an MC SM including a thorough modelling of the detector response and physical effects in a uniform water-equivalent phantom was efficient to get reasonable quantitative accuracy in homogeneous and heterogeneous phantoms. Modelling the phantom heterogeneities in the SM did not necessarily yield the most accurate estimate of the activity distribution, due to the high variance affecting many SM elements in the most sophisticated SM.

Effect of filters and reconstruction algorithms on I-124 PET in Siemens Inveon PET scanner

“…The difference between the point spread functions may lead to errors for MAP reconstructions of I-124 PET on Siemens Inveon PET scanners. Recently, Moreau and colleagues calculated the system matrix for the reconstruction of I-124 [15]. When these derived system matrices of I-124 were implemented on a Siemens Inveon PET scanner, the resulting spatial resolution with MAP reconstruction was improved.…”

Implementation of a Spatially-Variant and Tissue-Dependent Positron Range Correction for PET/CT Imaging

“…To overcome the limitations induced by the PR effects, several PR correction (PRC) methods have been proposed ( Derenzo, 1986 ; Bai et al, 2003 ; Rahmim et al, 2008 ; Fu and Qi, 2010 ; Kraus et al, 2012 ; Cal-González et al, 2015 ; Moreau et al, 2015 ; Bertolli et al, 2016 ), most of which assume a spatially uniform Gaussian PR distribution ( Derenzo, 1986 ). However, fewer, yet more realistic approaches, consider a heterogeneous tissue-dependent distribution following an isotropic Gaussian distribution within a specific tissue ( Bai et al, 2003 ; Alessio and MacDonald, 2008 ; Cal-González et al, 2015 ).…”