Development of new copper-64 labeled rhodamine: a potential PET myocardial perfusion imaging agent.

BACKGROUND: Myocardial perfusion imaging (MPI) is one of the most commonly performed investigations in nuclear medicine procedures. Due to the longer half-life of the emerging positron emitter copper-64 and its availability from low energy cyclotron, together with its well-known coordination chemistry, we have synthesized 64Cu-labeled NOTA- and 64Cu-NOTAM-rhodamine conjugates as potential cardiac imaging agents using PET. RESULTS: 64Cu-NOTA- and 64Cu-NOTAM-rhodamine conjugates were synthesized using a traightforward and one-step simple reaction. Radiochemical yields were greater than 97% (decay corrected), with a total synthesis time of less than 25 min. Radiochemical purities were always greater than 98% as assessed by TLC and HPLC. These synthetic approaches hold considerable promise as a simple method for 64Cu-rhodamine conjugates synthesis, with high radiochemical yield and purity. Biodistribution studies in normal Fischer rats at 60 min post-injection, demonstrated significant heart uptake and a good biodistribution profile for both the radioconjugates. However, the 64Cu-NOTAM-rhodamine conjugate has shown more heart uptake (~ 10% ID/g) over the 64Cu-NOTA-rhodamine conjugate (5.6% ID/g). CONCLUSIONS: These results demonstrate that these radioconjugates may be useful probes for the PET evaluation of MPI.

Evaluation of the Small-animal Nano Scan PET/CT System using 89Zr.

INTRODUCTION: The purpose of the present work was to evaluate the imaging characteristics of 89Zr-PET in comparison with those obtained using fluorine-18 Fluorodeoxyglucose (18FFDG) PET (a gold standard tracer in PET imaging) using a small-animal NanoScan PET/CT scanner. METHODS: The system's spatial resolution, sensitivity, uniformity, and image quality were measured on a Nano Scan small-animal PET/CT scanner according to the NEMA NU4-2008 protocols. For reconstruction images, we used 2D and 3D reconstruction algorithms. The reconstruction methods included filter back projection (FBP), the ordered subsets expectation maximization (OSEM) algorithm, and the 3D Tera-Tomo algorithm, which are developed for the NanoScan small-animal PET/CT scanner. RESULTS: The results obtained showed a significant difference in the spatial resolution for 89Zr as compared to 22Na and 18F when using a 2D reconstruction algorithm. The spatial resolution values were much enhanced by using the 3D Tera-Tomo reconstruction for each isotope, the Full width at half maximum (FWHM) values was less than 1 for all isotopes at the center of the field of view (FOV). This difference in spatial resolution is dependent on the positron range, energy, and the reconstruction method. CONCLUSION: The long half-life of 89Zr makes it an ideal positron emitter for performing immuno- PET, which is matched with the biological half-life of intact mAbs.89Zr can also give several advantages over other long half-life positron emitters in relation to the overall imaging performance because of its relatively short positron range and simpler decay scheme. The values of 89Zr sensitivity that were obtained in the present study were less than those of previous studies.

Sodium-22-radiolabeled silica nanoparticles as new radiotracer for biomedical applications: in vivo positron emission tomography imaging, biodistribution, and biocompatibility.

Despite their advantageous chemical properties for nuclear imaging, radioactive sodium-22 ((22)Na) tracers have been excluded for biomedical applications because of their extremely long lifetime. In the current study, we proposed, for the first time, the use of (22)Na radiotracers for pre-clinical applications by efficiently loading with silica nanoparticles (SiNPs) and thus offering a new life for this radiotracer. Crown-ether-conjugated SiNPs (300 nm; -0.18±0.1 mV) were successfully loaded with (22)Na with a loading efficacy of 98.1%±1.4%. Noninvasive positron emission tomography imaging revealed a transient accumulation of (22)Na-loaded SiNPs in the liver and to a lower extent in the spleen, kidneys, and lung. However, the signal gradually decreased in a time-dependent manner to become not detectable starting from 2 weeks postinjection. These observations were confirmed ex vivo by quantifying (22)Na radioactivity using γ-counter and silicon content using inductively coupled plasma-mass spectrometry in the blood and the different organs of interest. Quantification of Si content in the urine and feces revealed that SiNPs accumulated in the organs were cleared from the body within a period of 2 weeks and completely in 1 month. Biocompatibility evaluations performed during the 1-month follow-up study to assess the possibility of synthesized nanocarriers to induce oxidative stress or DNA damage confirmed their safety for pre-clinical applications. (22)Na-loaded nanocarriers can thus provide an innovative diagnostic agent allowing ultra-sensitive positron emission tomography imaging. On the other hand, with its long lifetime, onsite generators or cyclotrons will not be required as (22)Na can be easily stored in the nuclear medicine department and be used on-demand.