124Iodine: A Longer-Life Positron Emitter Isotope-New Opportunities in Molecular Imaging

(124)Iodine (I-124) with its 4.2 d half-life is particularly attractive for in vivo detection and quantification of longer-term biological and physiological processes; the long half-life of I-124 is especially suited for prolonged time in vivo studies of high molecular weight compounds uptake. Numerous small molecules and larger compounds like proteins and antibodies have been successfully labeled with I-124. Advances in radionuclide production allow the effective availability of sufficient quantities of I-124 on small biomedical cyclotrons for molecular imaging purposes. Radioiodination chemistry with I-124 relies on well-established radioiodine labeling methods, which consists mainly in nucleophilic and electrophilic substitution reactions. The physical characteristics of I-124 permit taking advantages of the higher PET image quality. The availability of new molecules that may be targeted with I-124 represents one of the more interesting reasons for the attention in nuclear medicine. We aim to discuss all iodine radioisotopes application focusing on I-124, which seems to be the most promising for its half-life, radiation emissions, and stability, allowing several applications in oncological and nononcological fields.