Therapeutic use of radioactive isotopes
In December, researchers from ISOLDE-CERN, the Paul Scherrer Institute (PSI) and the Institut Laue-Langevin (ILL) published the results of an in vivo study which successfully proved the effectiveness of four terbium isotopes for diagnosing and treating cancerous tumours.
Four terbium isotopes suitable for clinical purposes.
“ISOLDE is the only installation capable of supplying terbium isotopes of such purity and intensity in the case of three out of the four types used in this study,” explains Karl Johnson, a physicist at ISOLDE. “Producing over a thousand different isotopes, our equipment offers the widest choice of isotopes in the world!” Initially intended for fundamental physics research, ISOLDE has diversified its activities over time to invest in various projects in the materials science, biochemistry and nuclear medicine fields.
The proof-of-concept study has confirmed that the four terbium isotopes 149Tb, 152Tb, 155Tb produced by ISOLDE and 161Tb produced by ILL can be used in matched pairs to simultaneously diagnose and treat tumours. Having attached itself to a cancerous cell, one of the isotopes emits radiation detectable by medical imaging instruments while the other produces short-range radiation which destroys the surrounding cells. This makes it possible to monitor the status of the cancerous tumour throughout the patient’s treatment and to adapt the prescribed terbium isotope dose accordingly.
“Although the first clinical trials with terbium isotopes were performed in the 1990s, the project only really took concrete form two years ago when activities started in the framework of the PSI-ILL-ISOLDE collaboration,” explains Karl Johnston. “The main difficulties were logistic rather than of a physics nature. For instance, as isotopes have very short lifetimes, it was essential to reduce the timelag between their production and their use by medical staff to the absolute minimum. So the laboratories performing the clinical tests had to be located no more than three hours away by car! We therefore had to produce the terbium samples between 4 a.m. and 8 a.m. Then we had to pack the samples within 30 minutes with the help of CERN's Radiation Protection Group. If everything went according to plan, the isotopes were delivered to the PSI laboratories by 11.30 a.m.!”
Science and patience. This proof-of-concept study, jointly carried out by experts in the physics and nuclear medicine fields, has confirmed the therapeutic and diagnostic potential of terbium. However there is a long way to go before terbium can be used in our hospitals because the quantities produced by ISOLDE are too small to allow large-scale statistical studies to be performed. We will have to await the resumption of activities following the performance-enhancement upgrades during the LHC shutdown. Next appointment in June 2014.
| Terbium (Tb) is the only element in the Mendeleev periodic table that has four isotopes suitable for clinical purposes. The nuclear decay characteristics of these four isotopes mean that all the nuclear medicine procedures can be covered. 155Tb and 152Tb emit gamma rays detectable by gamma cameras or PET scanners. While 161Tb produces, inter alia, beta minus particles which damage the surrounding cells over a few millimetres, 149Tb produces short-range alpha particles which allow very localised destruction of the cancerous cells. |
If you want to find out more, you can read the press release
published by the Institut Laue-Langevin.
|  CERN Internal Communication is organising a visit to ISOLDE – an opportunity for you to see the CERN set-up that can produce over 1000 different isotopes! If you wish to participate, you can sign up for a visit by sending us an e-mail. Note that the visits will take place between 18 and 22 February, and will be open only to CERN access-card holders. The visit will include an introduction by experts and a tour of the ISOLDE set-up. |
by Caroline Duc
