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Radiopharmaceuticals for Radionuclide Therapy
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Meltem Ocak, Emre Demirci, Jessie R. Nedrow, Rebecca Krimins
Radium-223 (223Ra) is a calcium mimetic isotope and is deposited on hydroxyapatite crystal [73]. 223Ra-dichloride (223RaCl2) is developed to target metastatic bone disease, accumulating in areas of increased bone turnover. The availability of a long-lived 227Ac/227Th generator and a physical half-life of 11.4 d, which enables fast delivery to end users due to the long time between development and expiry, are among its advantages. Ra-223 has a complex decay mechanism in which, during each decay, four α-particles are emitted, resulting in high energy deposition (28.2 MeV), with 95 per cent of the emission energy. A radiation’s high linear energy transfer results in greater biological effectiveness than β-radiation, as well as the generation of double-strand DNA breaks, resulting in cytotoxicity that is independent of dose rate, phase of cell cycle formation, and concentration of oxygen. Due to the range of the alfa particles, less hematologic toxicity would be expected compared to β-radiation [76].
Theranostic approaches in nuclear medicine: current status and future prospects
Published in Expert Review of Medical Devices, 2020
Luca Filippi, Agostino Chiaravalloti, Orazio Schillaci, Roberto Cianni, Oreste Bagni
As specifically concerns the nuclear medicine contest, there are some radionuclides particularly suitable for theranostic approach, such as the already cited 131I, or luthetium-177 (177Lu), since they are characterized by both gamma and beta emission. In other cases, different radioisotopes can be labeled to the same biomolecule, the former with diagnostic purpose and the latter for therapy. In the majority of cases, isotopes suitable for positron emission tomography (PET) imaging are preferred in the diagnostic phase, since PET presents higher spatial resolution than conventional scintigraphy, also providing the opportunity of carrying out accurate quantitative information. As concerns the therapeutic counterpart, beta-emitting radionuclides, such as yttrium-90 (90Y) or 177Lu, are widely used, even though alpha-emitters, such as radium-223 (223Ra) and actinium-225 (225Ac), are emerging as useful potential tools [6].
Nuclear Medicine in Oncology
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2018
Carla Oliveira, Rui Parafita, Ana Canudo, Joana Correia Castanheira, Durval C. Costa
The most commonly used radionuclides for therapeutic applications are: IODINE-131, ITRIUM-90, LUTETIUM-177 (beta minus emitters) and more recently RADIUM-223 (alpha emitter). Although the main basis for therapeutics has relied upon the availability of the beta minus emitters, there is a growing trend to study the implementation of new radiopharmaceuticals labelled with alpha emitting radionuclides, chemistry and radiopharmacology permitting. Examples of newly proposed alpha emitters are: AMERICIUM-241, ASTATINE-211 and, in particular, BISMUTH-213 obtained from a generator of ACTINIUM-225/BISMUTH-213. The debate continues over the most adequate characteristics for choosing radionuclides (either beta minus or alpha emitters) to use with molecular-targeted therapy. The resulting radiopharmaceutical pharmacokinetics, production costs and targeted cellular functions are some of the most difficult obstacles to overcome during their research and development of new radioligands for therapeutic, as well as for diagnostic applications.