KVp versus PPV in diagnostic x-ray dosimetry

The SSDL-ININ has developed the infrastructure to set up the Calibration and Measurement Capabilities (CMC) by determining the Practical Peak Voltage (PPV) for the RQR, RQA RQT and RQR-M reference field qualities for diagnostic X-ray dosimetry. In this present work, emphasis is given to the PPV quantity, whose purpose is to normalize the contrast resolution in images obtained with X-ray generators operated at different kVp. The PPV concept is defined in the IEC 61267:2005 and the IEC 61676:2002 standards and in the IAEA code of practice TRS 457:2007. The PPV is, essentially, a weighted average of the X-ray tube voltages given any arbitrary shape of the voltage ripple in the X-ray high voltage HV generator. The characterization of quality reference fields: RQR, RQT, RQA and RQR-M for diagnostic X-ray dosimetry in terms of PPV is a pending task for the work of the dosimetrist in Mexico. The PPV should be used in the calibration of equipment for patient dosimetry and image quality control, with the purpose to attain the uncertainty goal of U(k=2)=7% in the air kerma in diagnostic X-Rays, according the IAEA TRS 457:2007.