Choline is an important building block of phospholipids in cell membranes. Certain cancers and medical conditions are known to demonstrate increased absorption and incorporation of choline into their cell membranes. 18-F-fluorocholine (F-choline) and 11-C-choline (C-choline) are diagnostic positron emission tomography (PET) radiotracers that can be used to image, in vivo, the metabolism of choline. Both tracers have been extensively studied in prostate cancer and C-choline has obtained US FDA approval for the investigation of recurrent prostate cancer. F-choline is currently not approved for clinical use by the FDA or Health Canada, but it offers many advantages over C-choline due to its better physical characteristics (mainly due to its positron range, shorter and longer half-life). In recent years, reports have started to emerge on broader potential applications of choline PET imaging, particularly for imaging parathyroid adenomas, certain cervical cancers and certain liver cancers. The main objective is to discover and explore potential new and emerging indications in which F-choline could play a role and provide clinically relevant information. Secondary objectives are 1) To assess the safety of F-choline PET imaging using F-choline produced at the CRCHUM; 2) assess changes in patient/disease management following F-choline PET imaging. Researchers hypothesize that F-choline will provide useful and incremental clinical information in a variety of conditions, and outperform the standard workup in numerous conditions. F-Choline PET exams will be performed on hybrid PET/CT scanners according to standard procedures. These examinations could be repeated at the discretion of the treating physician (up to a maximum of 4 exams per year) if the treating physician and the research team deem this could provide additional clinically useful information (for example, by helping to assess response to newly started therapy). The results will be provided to the attending physician and any new knowledge could lead to a change in treatment or an investigation of the condition that prompted enrollment in the study.