Over 30 different radiotracers have been investigated within this volume of work, including agents aimed at binding to receptors over-expressed on certain cancer cells, such as 18F-PSMA or 68Ga-PSMA and 68Ga-DOTA [10,11,12,13,14,15], while other radiotracers assess other metabolic processes, such as hypoxia, using 18F-FMISO, 18F-FAZA or 18F-HX-4 [16,17,18,19,20,21,22]. Here, FOLH1 is linked to cancer.