Histopathological characteristics of recurrent tumours (WHO grade I-IV) Safety and Toxicity (evolution according to CTCEA v3.0 criteria): the NCI Common Terminology Criteria for Adverse Events v3.0 is a descriptive terminology, that is used for Adverse Event (AE) reporting. A grading scale is provided for each AE term. Attached is a selection of categories, which are required to assess safety and toxicity of FET PET examinations.