A system for imaging an object comprising: an X-ray source operative to transmit X-rays through the object; a detector operative to receive the X-ray energy of the X-rays after having passed through the object and to generate corresponding object X-ray intensity; a dosimeter operative to measure a detector entrance dose at an entrance of the detector; and a controller operative to: measure, using the dosimeter, the detector entrance dose with no object being placed on the X-ray beam path; determine a relationship between an X-ray tube electrical parameter and the detector entrance dose; determine a relationship between the X-ray tube electrical parameter, the detector entrance dose and a detector average pixel intensity with no object being placed on the X-ray beam path; obtain a normalized air map as a function of the X-ray tube electrical parameter based on a normalized average of a series of calibration images acquired by the detector with no object being placed on the X-ray beam path; generate an air map based on the normalized air map, the detector entrance dose and the detector average pixel intensity; and reconstruct an image of the obj ect based on the air map and the measured object X-ray intensity. an X-ray source operative to transmit X-rays through the object; a detector operative to receive the X-ray energy of the X-rays after having passed through the object and to generate corresponding object X-ray intensity; a dosimeter operative to measure a detector entrance dose at an entrance of the detector; and a controller operative to: measure, using the dosimeter, the detector entrance dose with no object being placed on the X-ray beam path; determine a relationship between an X-ray tube electrical parameter and the detector entrance dose; determine a relationship between the X-ray tube electrical parameter, the detector entrance dose and a detector average pixel intensity with no object being placed on the X-ray beam path; obtain a normalized air map as a function of the X-ray tube electrical parameter based on a normalized average of a series of calibration images acquired by the detector with no object being placed on the X-ray beam path; generate an air map based on the normalized air map, the detector entrance dose and the detector average pixel intensity; and reconstruct an image of the obj ect based on the air map and the measured object X-ray intensity. measure, using the dosimeter, the detector entrance dose with no object being placed on the X-ray beam path; determine a relationship between an X-ray tube electrical parameter and the detector entrance dose; determine a relationship between the X-ray tube electrical parameter, the detector entrance dose and a detector average pixel intensity with no object being placed on the X-ray beam path; obtain a normalized air map as a function of the X-ray tube electrical parameter based on a normalized average of a series of calibration images acquired by the detector with no object being placed on the X-ray beam path; generate an air map based on the normalized air map, the detector entrance dose and the detector average pixel intensity; and reconstruct an image of the obj ect based on the air map and the measured object X-ray intensity.