Progress in nuclear medicine has been always tightly linked to the development of new radiopharmaceuticals and efficient production of relevant radioisotopes. The use of radiopharmaceuticals is an important tool for better understanding of human diseases and developing effective treatments. The availability of new radioisotopes and radiopharmaceuticals may generate unprecedented solutions to clinical problems by providing better diagnosis and more efficient therapies.
Impressive progress has been made recently in the radioisotope production technologies owing to the introduction of high-energy and high-current cyclotrons and the growing interest in the use of linear accelerators for radioisotope production. This has allowed broader access to several new radionuclides, including gallium-68, copper-64 and zirconium-89. Development of high power electron linacs resulted in availability of theranostic beta emitters such as scandium-47 and copper-67. Alternative, accelerator-based production methods of technetium-99m, which remains the most widely used diagnostic radionuclide, are also being developed using both electron and proton accelerators.
Special attention has been recently given to α-emitting radionuclides for in-vivo therapy. A few years ago, the first α-emitting radiopharmaceutical, Xofigo, (pharmaceutical-grade radium-223 dichloride solution) has been approved by the US FDA for cancer treatment. Many other α-emitting radiopharmaceuticals based on astatine-211, bismuth-212, bismuth-213, actinium-225, radium-223, lead-212, thorium-227 and terbium-149, are currently being developed. However, demand for these α-emitting radionuclides significantly exceed their supply. Numerous research groups worldwide are working on efficient production of these much sought after α-emitters.
The field of radiopharmaceuticals has witnessed continuous evolution thanks to the immense contributions of scientists from diverse disciplines such as radiochemistry, inorganic chemistry, organic chemistry, organometallic chemistry, biochemistry, molecular biology, physiology and pharmacology. Several milestones can be cited in the trajectory of this growth, which include continuing development of technetium-99m radiopharmaceuticals, automated synthesis of fluorine-18 labelled compounds, radiopharmaceuticals labelled with generator eluted gallium-68, labelled peptides and monoclonal antibodies for accurate diagnosis and treatment of tumours. The concept of theranostic radioisotopes, that combines the diagnosis and therapy properties of one radioisotope or a pair of similar radioisotopes, may provide an attractive paradigm for future development of medical applications of radionuclides. Biomolecules developed for specific molecular target and labelled with theranostic radionuclides provide clinically significant information for diagnosis, suitability of radionuclide therapy, dosimetry and post therapy planning, making personalised medicine a reality.