Radiopharmaceuticals are complex products which contain a radioactive compound (isotope). For the PET examination, the isotope used at the GOC’s Nuclear Medicine Department, is the 18F, that is “connected” to FDG, PSMA, FET, FLT, NaF, FMISO, L-DOPA, FES, SiFAlin-TATE depending on the medical question. The term “radiopharmaceutical” includes the word “pharmaceutical”. However, we are not dealing with identical concepts. As far as the radiopharmaceutical is concerned, its uniqueness lies upon in its production and in its availability. The production of a radiopharmaceutical is a very complicated procedure with many steps that need to be taken and is carried out exclusively by specifically trained personnel in special facilities with state-of-the-art equipment. Once the radiopharmaceutical is produced, a very demanding quality control is carried out, so that we can be certain that the substance fulfills all European requirements and is suitable and safe to be administered to the patient. The final decision for administration is always taken by the responsible physician. The availability of the radiopharmaceutical is unfortunately not guaranteed. The aforementioned process takes place daily in the department more than once, due to the short half-life of the isotope (only 110 minutes). The whole procedure begins long before the patient reaches our facilities and usually ends when the patient is within the Department. As it can be made clear, the short half-life is also why radiopharmaceutical is not directly available. This also explains why in most cases any problem occurring at any step of the production of the radiopharmaceutical cannot be foreseen but is realized only at the time that occurs. Therefore, any change, i.e. delay of the examination, cancellation or modification of its date, can usually occur on the very day of the examination and relatively close to the time or even after patient’s arrival in the center. In conclusion, a prediction of any modification is difficult and, in most cases, not possible. The unpleasant scenario of delay or rescheduling an examination, occurs only after repeated attempts to resolve any problem throughout the procedure prior to the administration of the radiopharmaceutical. The above decision is taken to ensure that the examination is carried out under sound production conditions and the final product fulfills all quality standards. Any inevitable change is made solely in order to achieve the above objectives.