A cancer patient from Italy was recently treated with tiny microspheres loaded in Delft. The university developed a special, flexible radiation facility for that purpose.
At the Delft research reactor, called Flexbefa, Holmium-165 is now irradiated in a new holder. This allows the spheres to be irradiated to high activity without damaging the biodegradable casing by gamma radiation. Holmium-165 is cleverly converted into radioactive Holmium-166 in this way. This is what cancer patients are often irradiated with, but the radioactivity of this material decreases rapidly, making it a race against time to get it to the patient as soon as possible. The major advantage of the new method is that the microspheres can be charged with more activity and there is more time to get the final product to the hospital, where it is then administered to the patient. Thanks to this Delft invention, patients worldwide will soon be able to benefit from this internal radiotherapy treatment.
Dr.ir. Antonia Denkova, associate professor in the Delft research group 'Applied Radiation and Isotopes', is working on a new technical facility to make materials deliberately radioactive under controlled conditions. Denkova: "We are doing this in particular to develop production routes for better-quality radioisotopes." Worldwide and also in the Netherlands, the demand for isotopes for medical use has increased for years.
Irradiating a stable material with neutrons creates an unstable isotope, which then 'decays' to another isotope. That decay releases radiation, and that radiation is used for medical purposes. This may be for diagnostics (radioisotopes in the body give off radiation that can be detected by SPECT scanners, for example, to diagnose areas such as cardiology, oncology or urology) or for treatment (radioisotopes near a tumour give off radiation that destroys cancer cells but spares healthy cells).
Packed in spheres
To safely introduce radioisotopes into the body, they are packaged in microscopic spheres (30 micrometres) of a body-friendly material. When producing these spheres, it is more practical to put the non-radioactive base material into the package beforehand and irradiate the whole thing. Until now, however, it has not been possible to emit only the desirable neutron radiation. And the packaging cannot handle the by-product, gamma radiation, very well.
Delft has now built a modular holder that shields the sphere from gamma radiation, while letting neutron radiation through. This allows you to make more radioactive beads, which are usable for longer after irradiation. The research team has now reduced the harmful gamma dose by a factor of 5.
Applicable in any nuclear reactor
The radiation facility developed in recent months has been named 'Flexible Radiation Facility', or 'FlexBeFa' for short. It is, irreverently put, a 20 by 40 by 40 cm box. The FlexBeFa is applicable in any nuclear reactor. Research leader Antonia Denkova: "There are 246 operational nuclear reactors in the world. Yet radioisotopes are currently produced on a commercial basis in only six of them. The principle of the FlexBeFa can be used everywhere, allowing for a larger network of producers close to the patients who specifically need the short-lived isotopes."
In addition, the FlexBeFa enables systematic research into new production methods for radioisotopes. Denkova: "Molybdenum-99, which is popular for medical diagnostics, is currently produced by irradiating slabs of Uranium-235, then dissolving it and finally extracting and purifying the molybdenum from the solution. We are trying to find an alternative that requires less highly enriched uranium and produces less radioactive waste."
Plans have been made to later incorporate cooling capabilities to further protect the sensitive beads from temperature increases due to the irradiation. Such an engineering modification is quite something as the leaden facility has to be hoisted in and out of a reactor. "Safety comes first," agrees Denkova.
By: Kelly Bakker
Source: TU Delft
