Preliminary study of metabolic radiotherapy with Re-188 via small animal imaging

Re-188 is a beta(-) (Emax = 2.12 MeV) and gamma (155 keV) emitter. Since its chemistry is similar to that of the largely employed tracer, Tc-99m, molecules of hyaluronic acid (HA) have been labelled with 188Re to produce a target specific radiopharmaceutical. The radiolabeled compound, i.v. injected in healthy mice, is able to accumulate into the liver after a few minutes. To study the effect of metabolic radiotherapy in mice, we have built a small gamma camera based on a matrix of YAP:Ce crystals, with 0.6 x 0.6 x 10 mm(3) pixels, read out by a R2486 Hamamatsu PSPMT. A high-sensitivity 20 mm thick lead parallel-hole collimator, with hole diameter 1.5 mm and septa of 0.18 mm, is placed in front of the YAP matrix. Preliminary results obtained with various phantoms containing a solution of Re-188 and with C57 black mice injected with the Re-188-HA solution are presented. To increase the space resolution and to obtain two orthogonal projections simultaneously we are building in parallel two new cameras to be positioned at 90 degrees. They use a CSI(TI) matrix with 1 x 1 x 5 mm 3 pixels read out by H8500 Hamamatsu Flat panel PMT.