Positron range estimations with PeneloPET

Abstract

Technical advances towards high resolution PET imaging try to overcome the inherent physical limitations to spatial resolution. Positrons travel in tissue until they annihilate into the two gamma photons detected. This range is the main detector-independent contribution to PET imaging blurring. To a large extent, it can be remedied during image reconstruction if accurate estimates of positron range are available. However, the existing estimates differ, and the comparison with the scarce experimental data available is not conclusive. In this work we present positron annihilation distributions obtained from Monte Carlo simulations with the PeneloPET simulation toolkit, for several common PET isotopes ( 18 F, 11 C, 13 N, 15 O, 68 Ga and 82 Rb) in different biological media (cortical bone, soft bone, skin, muscle striated, brain, water, adipose tissue and lung). We compare PeneloPET simulations against experimental data and other simulation results available in the literature. To this end the different positron range representations employed in the literature are related to each other by means of a new parameterization for positron range profiles. Our results are generally consistent with experiments and with most simulations previously reported with differences of less than 20% in the mean and maximum range values. From these results, we conclude that better experimental measurements are needed, especially to disentangle the effect of positronium formation in positron range. Finally, with the aid of PeneloPET, we confirm that scaling approaches can be used to obtain universal, material and isotope independent, positron range profiles, which would considerably simplify range correction.

Improved quantification for local regions of interest in preclinical PET imaging

“…To correct for positron range (Cal-González et al 2015b, 2011) we introduced an analytical expression for the positron range blurring kernel, obtained from fits to MC simulations of positron range (Cal-González et al 2013). This kernel is employed to deconvolve the image for the blurring attributable to positron range during reconstruction.…”

Searches for discrete symmetries violation in ortho-positronium decay using the J-PET detector

“…Minus sign denotes forbidden correlations and observing their nonvanishing value will be evidence for symmetry violation (QED) effects, as well as effi ciency for the gamma quanta detection. Detailed description of these effects can be found, for example, in [16][17][18].…”

Technical Note: Transconvolution based equalization of positron energy effects for the use of 68 Ge/68 Ga phantoms in determining 18 F PET recovery

“…68 Ga, the daughter nuclide of 68 Ge, emits β + on average with 836.02 keV and with an endpoint energy of 1899.1 keV . The different isotope energies lead to different source‐centred radial positron annihilation distributions, here referred to as positron range functions (PRFs). In PET, the image blur and its consequent PVE will therefore depend on the very isotope used for data acquisition …”

“…Akin to Wiener filtering, the PET/CT system's intrinsic PSF () acts hereby as a spatial filter against image noise amplification. As described previously, is directly determinable from the same phantom acquisitions as the RCs, while necessary PRF models are available from measurements or from computer simulations …”

“…Thus, knowing a β + emitter's energy spectrum, PRF models can be calculated from Monte Carlo (MC) simulations. In this work, the MC derived model provided by J. Cal‐González et al . was used with its specific parameters for 18 F and 68 Ga PRFs.…”