The Impact of Positron Range on PET Resolution, Evaluated with Phantoms and PHITS Monte Carlo Simulations for Conventional and Non-conventional Radionuclides

Abstract

Purpose: The increasing interest and availability of non-standard positron-emitting radionuclides has heightened the relevance of radionuclide choice in the development and optimization of new positron emission tomography (PET) imaging procedures, both in preclinical research and clinical practice. Differences in achievable resolution arising from positron range can largely influence application suitability of each radionuclide, especially in small-ring preclinical PET where system blurring factors due to annihilation photon acollinearity and detector geometry are less significant. Some resolution degradation can be mitigated with appropriate range corrections implemented during image reconstruction, the quality of which is contingent on an accurate characterization of positron range. Procedures: To address this need, we have characterized the positron range of several standard and non-standard PET radionuclides (As-72, F-18, Ga-68, Mn-52, Y-86, and Zr-89) through imaging of small-animal quality control phantoms on a benchmark preclinical PET scanner. Further, the Particle and Heavy Ion Transport code System (PHITS v3.02) code was utilized for Monte Carlo modeling of positron range-dependent blurring effects.

68Ga-DOTATOC-PET/MRI—A Secure One-Stop Shop Imaging Tool for Robotic Radiosurgery Treatment Planning in Patients with Optic Nerve Sheath Meningioma

“…For the Siemens Biograph PET/MRI, studies using PET image quality phantom (Esser) filled with fluorodeoxyglucose (F18) presented a detectability of the spheres down to 5 mm when sphere-to-background activity concentrations were 8:1 and acquisition time was 180 s. The size of the lesion in patient 5 was 4 mm and therefore beneath the resolving power. Furthermore, the smallest resolvable rod diameter differs between the radionuclides and is larger for Ga68 than for F18 [26].…”

Moving the goalposts while scoring―the dilemma posed by new PET technologies

“…In non-PSF PET, this results in a steady decrease in spatial resolution from the FOV center to its periphery, which is compensated for by PSF reconstruction [26]. Notably, PSF reconstruction usually refers to the correction for F-18 while optimal PSF compensation for other radionuclides would require integrating their different PSF based on specific positron ranges [27,28].…”

Unprecedented Kinetic Inertness for a Mn2+‐Bispidine Chelate: A Novel Structural Entry for Mn2+‐Based Imaging Agents

“…Given its low b + decay intensity (29.6 %), PET resolution as good as 1.2 mm could be achieved, which is particularly important in small animal imaging. [4] Thelong t 1/2 value makes 52 Mn particularly adapted to image slow biological processes.A ltogether,M n 2+ is the unique metal ion to offer detection capabilities in both MRI and PET. [5] Thermodynamically stable and kinetically inert complexation of Mn 2+ is indispensable to avoid in vivo release of the free metal ion, which could potentially cause toxicity during MRI for which large contrast agent quantities are needed, or lead to off-target signals in PET examinations.Inaddition, for good MRI efficiency,the complex should contain at least one inner sphere water molecule.H owever, the lower charge (with respect to Gd 3+ )a nd the lack of ligand-field stabilization energy for the high-spin d 5 electron configuration are not favorable to achieve high thermodynamic stability.…”