Production of 11C for PET imaging using a high repetition
rate laser-driven proton source.
In recent years, there has been a growing interest in laser-driven ion accelerators as a potential
alternative to conventional accelerators. A particularly promising application is the production of
radionuclides relevant for medical diagnosis, such as 11C for PET imaging. Typically, the
production of these nuclides is centralised in cyclotrons, which reduces the number of facilities
required, but limits the range of usable radionuclides to those with
longer lifetimes.
In this context, compact laser-driven accelerators appear to be an attractive option for the in situ
production of short-lived isotopes. Although the activities required for PET imaging (>MBq) are well
above those achievable by a single laser irradiation (~kBq), the advent of high power, high
repetition rate laser systems open the way to demonstrate relevant activities by continuous
irradiation, provided a suitable target system is developed. In this context, we have developed and
commissioned a target assembly based on a rotating wheel and automatic alignment procedure for
laser-driven proton acceleration at multi-Hertz rates. The assembly, which can host more than 5000
targets and ensuring continuous target replenishment with micron-level precision, has been
demonstrated to provide stable and continuous MeV proton acceleration at rates of up to 10 Hz
using the 45 TW laser system at L2A2 (Univ. of Santiago de Compostela).
The continuous production of 11C via the proton-boron reaction 11B(p,n)11C reaction has been
recently demonstrated using our target assembly on the 1 Hz, 1 PW VEGA-3 system (CLPU,
Spain). In an initial campaign, an activity of ~12 kBq/shot was measured, with a peak activity of
234 kBq achieved through accumulation of 20 consecutive shots. Furthermore, results of a more
recent campaign will be presented, where activation levels in excess of 4 MBq where achieved, as
measured through using coincidence detectors, and supported by online measurements of highflux
neutron generation. We demonstrate that the degradation of the laser-driven ion beam due to
heating of optics is currently the only bottleneck preventing the production of preclinical (~10 MBq)
PET activities with current laser systems. The scalability to next-generation laser systems and new
technologies for the continuous replenishment of the target will allow in the near future the
production of clinical (~200 MBq) activities.
