Medical applications

The wide variety of medical radioisotopes for both therapy and imaging are directly accessible at an ISOL facility. Most importantly, an ISOL facility provides a universal means to produce essentially all isotopes of medical interest practically carrier free and of high purity. Consequently, one can enable systematic biokinetic studies, simultaneously with different isotopes and different tracers. Besides the research for new and innovative medical radioisotopes, such isotopes can be systematically produced in very clean conditions with the extended beam times available at ISOL@MYRRHA.

Example of 149Tb

Single cancer cells and small cancer cell clusters can be effectively targeted with a tumor-seeking tracer labeled with α-emitting radio-isotopes. The tumor-seeking tracer is a molecule that specifically binds to the cancer cells and the α-emitting radio-isotopes attached to the tracer delivers the required dose. Alpha-emitting radio-isotopes may be of great advantage in this kind of therapy, because of the shorter penetration track compared to β and γ radiation. It has been shown that only very few α hits are sufficient to kill a cell, while the short range of the α particles (30-80 μm) increases the safety profile of α emitters. Nonetheless, the α-emitting nuclide has to fulfill several important requirements such as half-life, radiotoxicity of the daughter isotopes, biokinetics (in-vivo stability of the tumor-seeking tracer, clearance,…), affordable production price, and reliable supply.

It has been demonstrated that single cancer cells can be sterilized with high efficiency using rituximab labeled with 149Tb [1]. The study was carried out on 26 SCID (Severe Combined Immuno-Deficient) mice, which, being deficient in the immune defense of so-called B- and T-cancer cells, easily develop tumor masses after injection of such cancer cells. As shown in the figure, only the mice treated with the 149Tb-labelled rituximab were almost completely protected and did not show any signs of disease for four months after injection.

Survival graph of four different groups of SCID mice.  

Survival graph of four different groups of SCID mice. (picture from [1]) 

[1] G. J. Beyer et al., Eur. J. Nucl. Med. Mol. Imaging 31 (2004) 547