Exploitation of solid targetry for scandium-44 production at INMAS: a potential alternative to generator-produced radioisotopes

The aim of this work is to develop an alternative method of production of long-lived positron emission tomography (PET) radioisotopes (44-scandium) in quantities and quality useful for medical purposes in India. ⁴⁴Sc is useful in PET imaging (T_1/2 = 3.97 h; E_β+ = 1475 keV, 94.3%). The longer half-life permit longer radiolabeling manipulations and transportation to remote areas. It can be a potential alternative to ⁶⁸Ga in clinical PET diagnosis, offering longer half-life and better resolution than ⁶⁸Ga. Production options for ⁴⁴Sc include ⁴⁴Ti/⁴⁴Sc generator or cyclotron production. At INMAS, the production was planned using 16.5 MeV medium-sized medical cyclotron at INMAS. The produced ⁴⁴Sc was planned to label the well-characterized DOTA analogs. The tracers will be assessed with respect to their in vivo pharmacokinetic imaging capacity, as well as the total radiation dose to the patients in a head-to-head comparison with ⁶⁸Ga- labeled analogs. The entire production was planned as stepwise optimization with following steps involved: (a) development of a targetry system (b) development/optimization of the separation method, and (c) chelator development for scandium. The production of ⁴⁴Sc from natural 40-calcium was planned using the 16.5 MeV medium-sized medical cyclotron at INMAS. Pellets of target were prepared by pressing method and placed in aluminum target. The target was cooled using water and air combination and irradiated for varying time (5-10 min) and varying beam currents (5-10 μA). The absolute radioactivity of ⁴⁴Sc and other obtained radionuclides was measured by. A prototype shuttle was designed which could result in a homogenous target and ensure that there will be higher ⁴⁴Sc yields. Calculations were carried using the beam energy to arrive at the thickness of the shuttle. By beam optimization experiments, it was inferred that 10 μA beam current with an irradiation time of 10 min was sufficient to have radioactivity. To optimally separate ⁴⁴Sc from the irradiated calcium targets, a separation system was designed. Briefly, the irradiated natCaCO₃ target was dissolved in acid solution and passed through a combination of Dowex and DGA column to separate scandium. The present study attempts to establish the use of nucleolipids as imaging agent for brain. Feasible synthesis of DAU-loaded Ag nanoparticles has been synthesized along with its characterization. (author)