Use of Radioactive Ion Beams for Biomedical Research 2. in-vivo dosimetry using positron emitting rare earth isotopes with the rotating prototype PET scanner at the Geneva Cantonal Hospital

% IS331 \\ \\ The use of radioactive metal ions (such as $^{90}$Y, $^{153}$Sm or $^{186}$Re) in cancer therapy has made some progress, but has been hampered by factors that could be addressed at CERN with a greater likelihood of success than at any other installation in the world. The present proposal seeks to use the unique advantage of CERN ISOLDE to get round these problems together with the PET scanners at the Cantonal Hospital Geneva (PET~=~positron emission tomography). Radioisotope production by spallation at ISOLDE makes available a complete range of isotopes having as complete a diversity of types and energy of radiation, of half-life, and of ionic properties as one would wish. Among these isotopes several positron-emitters having clinical relevance are available.\\ \\Some free rare earth chelatas are used presently in palliation of painful bone metastases. Curative effects are not able for the moment with this kind of radiopharmaceuticals. More and better data on the biokinetics and bio-distribution in individual patients are required to optimise the injected dose in each individual case. Positron-emitting isotopes of the same element used for palliation, in combination with PET, allow us to measure quantitatively the radionuclide uptake in bone metastases. From such data clear relationships between radiation doses delivered to the metastases and the corresponding response can be evaluated.\\ \\A common chelator, EDTMP (EDTMP~=~ethylenediamine-tetramethylene phosphonic acid) is used in combination with the positron-emitters $^{142}$Sm or $^{86}$Y, while the corresponding $\beta$-emitting $^{153}$Sm or $^{90}$Y respectively is normally used in the therapy. The corresponding studies with the rotating PET scanners are performed in the Division of Nuclear Medicine, Cantonal Hospital Geneva.\\ \\The experiments will be continued in the frame of a new experiment and an extended collaboration.