Radiopharmaceuticals are used in nuclear medicine diagnosis and treatment ptotochols. The radiopharmaceutical activity given to the patient should be determined by dose calibrator before administration. The activity given to the patient is very important to know how the radiation affect the patient.It is not possible to understand the presence of radiation with the sense organs. The contact with the substance is essential for radiation to be detected. While doing any practices involving the nuclear medicine administration of a radiopharmaceutical, it is essential to use sensitive instrumentation for the detection and measurement of radioactive emissions. This is also especially important for experimental work contributing to scientific knowledge relating radiation doses to biological effects and it is importatnt to use an accurate measure of therapeutic levels of radioactivity. Dose calibrators, unlike other ion chamber detectors, are closed and pressurized rooms filled with argon gas. Ionization chamber radionuclide calibrators analyze the total amount of activity present by measuring the total amount of ionization produced by the sample. Therefore, for both application accuracy and radiation safety, it is very important that the dose calibrator accurately determines the activity to be delivered to the patient.