HK1 and neoplasm: Given that 99mTc-3PRGD2 is a target-specific radiotracer whose biodistribution is determined by its receptor, the high expression level of αvβ3 in early HCC contributes to the high tumour uptake of 99mTc-3PRGD2; therefore, 99mTc-3PRGD2 imaging is able to sensitively detect early HCC while 18F-FDG imaging is used to evaluate glucose metabolism, the main mechanism of 18F-FDG uptake in malignant tumours largely depends on the presence of facilitated glucose transporters, especially type 1 (Glut 1) and a rate-limiting glycolytic enzyme, especially hexokinase (HK) type II.