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124I &89Zr Radiopharmaceuticals as an Alternative to F-18 Tracers a Comparative Study on Radionuclide Properties, Manufacturing, and ApplicationsIvan Ludzhev, Plovdiv UniversityDimitar Ivanov, Plovdiv University

IntroductionThe convergence of molecular and cellular biology with imaging sciences to molecular imaging has in vivo revolutionized current biomedical research. Molecular imaging is defined as the characterization and measurement of biologic processes at the cellular and molecular level .

Molecular and cellular processes can be studied and visualized in vivo at various levels of resolution by means of imaging techniques, which span from ultrasonic to gamma-ray frequencies.

Mathematical methods for the evaluation of PET measurements within the framework of compartment models are well established. Within the spectrum of available positron emitters, fluorine-18 (F) is an almost ideal radionuclide for PET, thanks to its easy of 18 production and favorable physical properties, such as a 109.8 min half-life and low energy + (0.64 MeV).

The most frequently used radionuclides for PET have relatively short half-lives :11C: 20.4 min; 18F: 109.8 min; Which may limit both the synthesis procedures and the time frame of PET studies. Iodine-124 (124I, t1/2 = 4.2 d) is an alternative long-lived PET radionuclide attracting increasing interest for long term clinical and small animal PET studies.

PET imaging of 124IPET relies on the detection of the two back-to-back 511 keV photons in coincidence. These two photons arise from positron annihilation following the positron (+) decay of the radioisotope on the labeled pharmaceutical. For the traditional PET isotopes, + decay occurs greater than 96 percent of the time. For 124I however, + decay occurs only 23 percent of the time with the positrons having higher energies when compared with the traditional PET isotopes.

Imaging of 89ZrPositron emission tomography (PET) imaging with radiolabeled monoclonal antibodies has always been a dynamic area in molecular imaging. With decay half-life (3.3 d) well matched to the circulation half-lives of antibodies (usually on the order of days), (89)Zr has been extensively studied over the last decade.

Labeling of mAbsI-124 & Zr-89 immuno-PET

Preclinical and clinical examplesImmuno-PET

Conclusions

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