G. Karcher

Compared vulnerabilities to small cardiac motions between different cameras used for myocardial perfusion imaging

This phantom-based study was aimed to determine whether cardiac CZT-cameras, which provide an enhanced spatial resolution and image contrast compared to Anger cameras, are similarly affected by small cardiac motions. Translations of a left ventricular (LV) insert at half-SPECT acquisitions through six possible orthogonal directions and with 5- or 10-mm amplitude were simulated on the Discovery NM-530c and DSPECT CZT-cameras and on an Anger Symbia T2 camera equipped with an astigmatic (IQ.SPECT) or conventional parallel-hole collimator (Conv.SPECT). SPECT images were initially reconstructed as currently recommended for clinical routine. The heterogeneity in recorded activity from the 17 LV segments gradually increased between baseline and motions simulated at 5- and 10-mm amplitudes with all cameras, although being higher for Anger- than CZT-cameras at each step and resulting in a higher mean number of artifactual abnormal segments (at 10-mm amplitude, Conv.SPECT: 3.7; IQ.SPECT: 1.8, Discovery: 0.7, DSPECT: 0). However, this vulnerability to motion was markedly (1) decreased for Conv.SPECT reconstructed without the recommended Resolution Recovery algorithm and (2) increased for DSPECT reconstructed without the recommended cardiac model. CZT-cameras and especially the DSPECT appear less vulnerable to small cardiac motions than Anger-cameras although these differences are strongly dependent on reconstruction parameters.

Development of 6-[(18) F]fluoro-carbohydrate-based prosthetic groups and their conjugation to peptides via click chemistry.

This work describes the development of new 6-[(18) F]fluoro-carbohydrate-based prosthetic groups equipped with an azido arm that are able to participate in copper(I)-catalyzed cycloadditions for (18) F labeling of biomolecules under mild conditions. The radiolabeling in high radiochemical yields (up to 68 ± 6%) of these different prosthetic groups is presented. The flexibility of the azido arm introduced on the carbohydrate moieties allows efficient click reactions with different alkyne functionalized peptides such as gluthation or Arg-Gly-Asp derivatives in order to prepare glycopeptides. The radiosyntheses of (18) F-labeled glycopeptides proceed in high radiochemical yields (up to 76%) in an automated process with excellent radiochemical purity. The addition of a sugar moiety on peptides should enhance the bioavailability, pharmacokinetic, and in vivo clearance properties of these glycopeptides, compared with the unlabeled native peptide, and these properties are highly favorable for positron emission tomography imaging. A high uptake of (18) F-β-gluco-c(RGDfC) is shown by positron emission tomography imaging in a subcutaneous abscess model in the rat, revealing the potential of this tracer to monitor integrin expression as a part of inflammation and/or angiogenesis processes.

Article originalImpact d’une réduction d’activité sur la mesure de la fraction d’éjection du ventricule gauche sur caméra D-SPECTImpact of a decrease in recorded counts on the left ventricular ejection fraction measurement from the D-SPECT camera

Introduction Radionuclide ventriculography provides a reproducible measurement of the left ventricular fraction ejection (LVEF) but with a significant body radiation (effective dose of 5,9 mSv for the injection of 850 Mbq of 99mTc). The highly sensitive semi-conductor (CZT) cameras could allow decreasing the injected activity by a factor 3, similarly to that of myocardial perfusion imaging. Our study was aimed to determine whether the LVEF measurement provided by radionuclide ventriculography on the CZT D-SPECT camera is impacted by a 70% reduction in recorded counts.

Synthesis and preliminary in vivo evaluation of new [18F]fluoro-inositols as Positron Emission Tomography radiotracers

This study describes the synthesis and radiosynthesis of eight new [18F]fluoro-inositol-based radiotracers in myo- and scyllo-inositol configuration. These radiotracers are equipped with a propyl linker bearing fluorine-18. This fluorinated arm is either on a hydroxyl group, i.e. O-alkylated inositols, or on the cyclohexyl backbone, i.e. C-branched derivatives. To modulate lipophilicity, inositols were synthesized in acetylated or hydroxylated form. Automated radiosynthesis was performed on the AllInOne module and the radiotracers were produced in good radiochemical yields (15-31.5% dc). Preliminary in vivo preclinical evaluation of these eight [18F]fluoro-inositols as Positron Emission Tomography (PET) imaging agents in a breast tumour-bearing mouse model was performed and compared with [18F]-2-fluoro-2-deoxy-d-glucose ([18F]FDG). Amongst the different inositols, [18F]myo-2 showed the highest tumour uptake 2.34±0.39%ID/g, revealing the potential of this tracer for monitoring breast cancer.

Fully automated production of sodium [(18)F]fluoride on AllInOne and miniAllInOne synthesizers.

A fully automated production of the imaging agent sodium [(18)F]fluoride ([(18)F]NaF) on two different modules commercialized by Trasis®, the AllInOne and the miniAllInOne, is reported. Both modules allow to prepare [(18)F]NaF in good radiochemical yield (around 97%) in less than 4min with the same specifications. Quality control of [(18)F]NaF produced by this way was performed according to the US and European Pharmacopeia monograph requirements.