In comparison to conventional nuclear medicine imaging approaches for localization of the offending parathyroid tissue, positron emission tomography with computed tomography (PET/CT) offers superior image resolution with an additional advantage of attenuation correction and co-registration of functional and anatomical information. 18F-fluorocholine is a PET tracer which is commonly used for prostate cancer imaging. In contrast to 18F-fluorodeoxyglucose (18F-FDG), it is also taken up by well-differentiated neoplasms in which 18F-FDG uptake is unreliable. The investigators hypothesize that 18F-fluorocholine might be efficiently taken up by parathyroid adenomata and/or hyperplasia.