Intraoperative beta- detecting probe for radio-guided surgery of brain tumors

The innovation of the radio-guided surgery exploiting β- emitters is the higher tumor-to-non-tumor ratio (TNR) allowing both a smaller radiopharmaceutical absorbed dose to detect cancerous remnants and the possibility of extending the technique also to cases with a large uptake of surrounding healthy organs, as for brain tumors. Our first study cases are meningiomas, since an appropriate β- emitting drug is already available (90Y-DOTATOC), but the goal is to apply this technique to gliomas. We verified the uptake of the radiotracer in 8/10 patients affected by meningiomas with TNR ≥ 10 and in 9/12 patients with a TNR ≥ 4 in case of gliomas. We developed prototypes of an intraoperative probe detecting β- radiation. The core of the probe is a millimetric scintillator made of para-terphenyl due to its high light yield and low density. Tests in laboratory showed that with a radiotracer activity on the tumor of 5 kBq/ml and a TNR of 10 a 0.1 ml cancerous residual can be detected in 1s. That corresponds to administer to the patient 1 MBq/kg of radiopharmaceutical, which is a dose comparable to those administered for diagnostic use. Finally we estimated with a detailed simulation the exposure of the surgeon resulted in ~0.1 Sv/h to the whole body and ~1 Sv/h to the hands, well below the corresponding values for established RGS with gamma radiation.