Production, PET performance and dosimetric considerations of¹³⁴Ce/¹³⁴La, an Auger electron and positron-emitting generator for radionuclide therapy

We propose the use of the Auger electron and positron-emitting generator ¹³⁴Ce/¹³⁴La (half-lives 3.16 d and 6.45 min) for radionuclide therapy. It combines emission of high-energy beta particles with Auger electrons. The high-energy beta particles have similar energies as those emitted by ⁹⁰Y. Many cancer patients receiving radionuclide therapy have both bulk tumours, which are best treated with high-energy beta particles, and single spread cells or micrometastasis, which are preferably treated with low-energy electrons such as Auger and conversion electrons. Furthermore, the position-emitting ¹³⁴La can be used to study kinetics and dosimetry using PET. Production and PET performance were investigated and theoretical dosimetry calculations were made. PET resolution, recovery and quantitative accuracy were slightly degraded for ¹³⁴La compared to ¹⁸F. ¹³⁴Ce/¹³⁴La absorbed doses to single cells were higher than absorbed doses from ⁹⁰Y and ¹¹¹In. Absorbed doses to spheres representing bulk tumours were almost as high as for ⁹⁰Y, and a factor 10 higher than for ¹¹¹In. Whole-body absorbed doses, based on kinetics of the somatostatin analogue octreotide, were higher for ¹³⁴Ce/¹³⁴La than for ⁹⁰Y because of the ¹³⁴La annihilation photons. This initial study of the therapeutic possibilities of ¹³⁴Ce/¹³⁴La is encouraging and justifies further investigations.