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Inhaled radioactive CO is currently the tracer of choice for blood volume quantification by positron emission tomography (PET). This measurement is of great interest for several clinical and research applications. However, owing to the short half-life of the radiolabeled CO, it can only be used in centers equipped with a cyclotron. In the present work, we propose an alternative method to label the red blood cells with [(18) F] in order to obtain blood volume measurements by PET. The use of the radioactive synthon [(18) F] N-succinimidyl 4-[(18) F]fluorobenzoate ([(18) F]SFB) was evaluated for erythrocyte labeling and PET blood volume imaging. The images provided by [(18) F]SFB labeled erythrocytes were compared with those obtained with inhaled [(11) C]CO. Blood volumes obtained with [(18) F]SFB labeled erythrocytes were similar to those obtained with [(11) C]CO in all of the evaluated organs with the exception of spleen, which presented lower uptake with this method. Since the [(18) F]-SFB binds irreversibly to red blood cells, in vivo stability of the radiolabel was higher compared with the [(11) C]CO method. Additionally, owing to the longer half-life and the shorter positron range of [(18) F], the image quality was also higher with the [(18) F]SFB radiolabeled erythrocytes. The labeling of red blood with [(18) F]SFB represents an advantageous alternative to radioactive CO for blood volume measurement by PET and cardiovascular isotopic imaging.

Santiago Rojas et al., Purpose: [18F]Fluoromisonidazole (18F-FMISO) is a nitroimidazole derivative that has been proposed as a positron emission tomography (PET) radiotracer to detect hypoxic tissue in vivo. This compound accumulates in hypoxic but viable tissue and may be a good candidate for evaluating the ischemic penumbra. We evaluated the time course of 18F-FMISO uptake using PET in a rat model of permanent cerebral ischemia and the correlation with histological changes. Procedures: Rats (n = 14) were subjected to permanent ischemia by intraluminal occlusion of the middle cerebral artery in order to assess by PET the uptake of 18F-FMISO at various times over 24 h following ischemia. The PET results were compared to histological changes with Nissl and 2,3,5 triphenyltetrazolium chloride staining. Results: Elevated uptake of 18F-FMISO was detected in the infarcted area up to 8 h after occlusion but was no longer detected at 24 h, a time point coincident with pan necrosis of the tissue. Conclusions: Our findings suggest that salvageable tissue persists for up to 8 h in this rat model of brain ischemia. We propose 18F-FMISO PET as a tool for evaluating the ischemic penumbra after cerebral ischemia. © 2010 Academy of Molecular Imaging and Society for Molecular Imaging., Francisca P Figueiras has a PhD fellowship from the Fundacao para a Ciencia e a Tecnologia, POCI 2010, FSE SFRH/BD/38341/2007, and the European Community's Seventh Framework Program (FP7/2007-2013), HEALTH F2 2008 200728. We thank the European Community DiMI (LSHB-CT-2005-512146) for its support in this study.

Positron emission tomography (PET) has been used extensively to evaluate the neuropathology of Alzheimer's disease (AD) in vivo. Radiotracers directed toward the amyloid deposition such as [18F]-FDDNP (2-(1-{6-[(2-[F]Fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile) and [11C]-PIB (Pittsburg compound B) have shown exceptional value in animal models and AD patients. Previously, the glucose analogue [18F]-FDG (2-[(18)F]fluorodeoxyglucose) allowed researchers and clinicians to evaluate the brain glucose consumption and proved its utility for the early diagnosis and the monitoring of the progression of AD. Animal models of AD are based on the transgenic expression of different human mutant genes linked to familial AD. The novel transgenic 5XFAD mouse containing 5 mutated genes in its genome has been proposed as an AD model with rapid and massive cerebral amyloid deposition. PET studies performed with animal-dedicated scanners indicate that PET with amyloid-targeted radiotracers can detect the pathological amyloid deposition in transgenic mice and rats. However, in other studies no differences were found between transgenic mice and their wild type littermates. We sought to investigate in 5XFAD mice if the radiotracers [11C]-PIB, and [18F]-Florbetapir could quantify the amyloid deposition in vivo and if [18F]-FDG could do so with regard to glucose consumption. We found that 5XFAD animals presented higher cerebral binding of [18F]-Florbetapir, [11C]-PIB, and [18F]-FDG. These results support the use of amyloid PET radiotracers for the evaluation of AD animal models. Probably, the increased uptake observed with [18F]-FDG is a consequence of glial activation that occurs in 5XFAD mice. © 2013 Elsevier Inc., This study was supported by grant SAF2009-13093-C02-02 and CSD2010-00045 from the Spanish Ministerio de Ciencia e Innovación (MCINN), MOIF-CT-2006-039637 from the European Union, 2009/SGR/214 from the Generalitat, Catalonia, and CDTI under the CENIT Programme (AMIT Project).

Inhaled radioactive CO is currently the tracer of choice for blood volume quantification by positron emission tomography (PET). This measurement is of great interest for several clinical and research applications. However, owing to the short half-life of the radiolabeled CO, it can only be used in centers equipped with a cyclotron. In the present work, we propose an alternative method to label the red blood cells with [(18) F] in order to obtain blood volume measurements by PET. The use of the radioactive synthon [(18) F] N-succinimidyl 4-[(18) F]fluorobenzoate ([(18) F]SFB) was evaluated for erythrocyte labeling and PET blood volume imaging. The images provided by [(18) F]SFB labeled erythrocytes were compared with those obtained with inhaled [(11) C]CO. Blood volumes obtained with [(18) F]SFB labeled erythrocytes were similar to those obtained with [(11) C]CO in all of the evaluated organs with the exception of spleen, which presented lower uptake with this method. Since the [(18) F]-SFB binds irreversibly to red blood cells, in vivo stability of the radiolabel was higher compared with the [(11) C]CO method. Additionally, owing to the longer half-life and the shorter positron range of [(18) F], the image quality was also higher with the [(18) F]SFB radiolabeled erythrocytes. The labeling of red blood with [(18) F]SFB represents an advantageous alternative to radioactive CO for blood volume measurement by PET and cardiovascular isotopic imaging.

Rodent models are frequently used in aging re search to investigate biochemical age effects and aid in the development of therapies for pathological and non pathological age related degenerative processes In order to validate the use of animal models in aging research and pave the way for longitudinal intervention based animal studies, the consistency of cerebral aging processes across species needs to be evaluated The dopaminergic system seems particularly susceptible to the aging process, and one of the most consistent findings in human brain aging research is a decline in striatal D2-like receptor (D2R) availability, quantifiable by positron emission tomography (PET) imaging In this study we aimed to assess whether similar age effects can be discerned in rat brains, using in vivo molecular imaging with the radioactive compound [C-11] raclopride We observed a robust decline in striatal [C-11] raclopride uptake in the aged rats in comparison to the young control group, comprising a 41% decrement in striatal binding potential In accordance with human studies, these results indicate that substantial reductions in D2R availability can be measured in the aged striatal complex Our findings suggest that rat and human brains exhibit similar biochemical alterations with age in the striatal dopaminergic system, providing support for the pertinence of rodent models in aging research (C) 2010 IBRO Published by Elsevier Ltd All rights reserved