ERBB2 and neoplasm: At 1 h post-injection, no difference was observed between the HER2-negative and HER2-positive tumor-to-blood ratios (0.39 and 0.37, respectively), whereas at 2 h post-injection, HER2-positive mice showed close to a four times higher ratio compared to the HER2-negative mice at 1.01 and 0.27, respectively (Figure S5A).