Copper-64 (64Cu)-DOTA-trastuzumab PET images of metastatic brain tumors in patients with human epidermal growth factor receptor 2 (HER2)-positive primary breast tumors. The white arrows show the metastatic brain tumors. Upper panels: 64Cu-DOTA-trastuzumab PET images. Lower panels: gadolinium (Gd)-DTPA-enhanced T1-weighted MR imaging images. White arrows indicate metastatic brain lesions detectable by both MR imaging and 64Cu-DOTA-trastuzumab PET, and the red arrow indicates a lesion detectable by MR imaging but not by 64Cu-DOTA-trastuzumab PET. In the PET image from patient 2, nonspecific high uptake in the blood was noted. (From Kurihara H, Hamada A, Yoshida M, et al. 64Cu-DOTA-trastuzumab PET imaging and HER2 specificity of brain metastases in HER2-positive breast cancer patients. EJNMMI Res 2015;5(8):4; with permission.)