Since the adenosine A3 receptor (A3R) is considered to be of high clinical importance in the diagnosis and treatment of ischaemic conditions (heart and brain), glaucoma, asthma, arthritis, cancer and inflammation, a suitable and selective A3R PET tracer such as [18F]FE@SUPPY would be of high clinical value for clinicians as well as patients. The gene discussed is ADORA3; the disease is glaucoma.