Manganese-52 positron emission tomography tracer characterization and initial results in phantoms and in vivo

摘要

Purpose: Manganese(II) is employed as a contrast agent with magnetic resonance imaging (MRI) for study of neuronal activation in rats and mice. However, at the concentrations required for MRI, Mn may induce pharmacological or toxic effects. Positron emission tomography (PET) imaging of 52MnCl2 at tracer doses has the potential to allow similar Mn studies as manganese-enhanced MRI while providing quantitative results and avoiding toxic effects. In this work, 52MnCl2 is produced and characterized as a PET tracer in phantoms and in rats. Methods: 52MnCl2 was produced by proton irradiation of natural Cr foil and separated by column chromatography. Images were acquired on a Siemens Focus 120 small animal PET scanner. Phantom images were acquired to assess uniformity, resolution, cascade background correction, and count rate linearity. Images of rats were also acquired after systemic and intracerebroventricular (ICV) administration of 52MnCl2 to investigate Mn(II) distribution in vivo. Results: Irradiation yield was 74.6 ± 8.5 kBq//xAmin 52Mn at end of bombardment with initial specific activity of at least 3.5 MBqmol. 52Mn PET images show similar uniformity and resolution to 18F. 18F based detector efficiency normalization is adequate for 52Mn imaging. Subtraction of a rescaled random events distribution from sinogram data is effective for cascade correction of 52Mn PET data. After systemic injection, 52Mn appears in structures throughout the body of rats, including bones, liver, intestines, and the pituitary gland, but does not appear detectably throughout the brain. After ICV injection, 52Mn remains in the brain and spinal cord. Conclusions: 52Mn is a promising tracer for small animal PET imaging, yielding image quality comparable to 18F. Potential applications include studies similar to Mn-enhanced neuronal MRI, and in other organ systems including bones, spinal cord, and the digestive tract.