Fig. 4: Patterns and classification of 89Zr-trastuzumab lesion uptake based on visual assessment, confronted with an FDG PET/CT.

a HER2 PET/CT (upper row, maximum intensity projection (MIP) and axial PET and fusion images) in a patient with liver lesion showing no 89Zr-trastuzumab uptake (class 1, HER2-negative lesion) and a mediastinal lymph node showing uptake close to background activity (class 2, HER2-negative lesion) confronted with the FDG PET/CT images (lower row, MIP and axial PET and fusion images). b HER2 PET/CT (upper row, MIP and axial PET and fusion images) in a patient with axillary lymph node showing visible 89Zr-trastuzumab uptake (class 3, HER2-positive lesion) and a liver lesion showing clearly visible, high uptake (class 4, HER2-positive lesion) confronted with the FDG PET/CT images (lower row, MIP, and axial PET and fusion images).