Only few studies have explored the use of PET radiotracers for sig1R imaging of tumours, and even less have addressed brain tumours in particular [36,39,67,68,69,70] such as the investigation of sig1R in an ectopic glioma rat model as well as in spontaneous pituitary tumours in rats using [11C]SA4503 by the group of van Waarde [39,69,70]. The gene discussed is SIGMAR1; the disease is central nervous system cancer.