Stability Study of Ionization Chambers in Standard Mammography Radiation Beams

The ionization chambers are widely utilized in diagnostic radiology quality control and dosimetry. They are simple to use, and can be found commercially in various types depending on their applications. They are the recommended devices for the determination of the beam qualities in mammographic range. To assure the reliability of the measurements, the stability of the response of the ionization chamber should be within international limits. In this work, the stability of two ionization chambers of the Calibration Laboratory of IPEN was evaluated. The ionization chambers utilized in this work were a homemade tandem ionization chamber and a reference class ionization chamber. They were irradiated in standard mammography beams at the Calibration Laboratory of IPEN. For the short-term stability, the chambers presented a maximum value for the coefficient of variation of 2.9%, within ± 3% as stated in the IEC 61674 standard. The long-term stability test results for the ionization chambers were within ± 2%, as recommended by the international standard.