A method, comprising: providing a beam from a laser Compton x-ray or gamma ray source; directing said beam onto a first location of an object; detecting, at a threshold of detection of a detector, a first portion of said beam that passes through said first location, to produce a first detected signal at said detector; the threshold of detection of the detector being determined by a number of photons required at a pixel of the detector to achieve a threshold level of detectability, to thus produce said first detected signal; upon reaching said threshold of detection and producing said first detected signal, preventing said beam from propagating onto said first location; determining a first number of photons or a first beam energy directed at said first location, wherein said first number of photons or said first beam energy is the amount required to produce said first detected signal at said threshold of detection of said detector; directing said beam onto a second location of said object; detecting, at said threshold of detection of said detector, a second portion of said beam that passes through said second location, to produce a second detected signal at said detector; upon reaching said threshold of detection and producing said second detected signal, preventing said beam from propagating onto said second location; determining a second number of photons detected at said second location if said first number of photons was determined, or a second beam energy detected at said second location if said first beam energy was determined at said second location, wherein said second number of photons or said second beam energy is the amount required to produce said second detected signal at said threshold of detection; and producing a map of the density variations of said object using (i) said first number of photons and said second number of photons, or (ii) said first beam energy and said second beam energy. providing a beam from a laser Compton x-ray or gamma ray source; directing said beam onto a first location of an object; detecting, at a threshold of detection of a detector, a first portion of said beam that passes through said first location, to produce a first detected signal at said detector; the threshold of detection of the detector being determined by a number of photons required at a pixel of the detector to achieve a threshold level of detectability, to thus produce said first detected signal; upon reaching said threshold of detection and producing said first detected signal, preventing said beam from propagating onto said first location; determining a first number of photons or a first beam energy directed at said first location, wherein said first number of photons or said first beam energy is the amount required to produce said first detected signal at said threshold of detection of said detector; directing said beam onto a second location of said object; detecting, at said threshold of detection of said detector, a second portion of said beam that passes through said second location, to produce a second detected signal at said detector; upon reaching said threshold of detection and producing said second detected signal, preventing said beam from propagating onto said second location; determining a second number of photons detected at said second location if said first number of photons was determined, or a second beam energy detected at said second location if said first beam energy was determined at said second location, wherein said second number of photons or said second beam energy is the amount required to produce said second detected signal at said threshold of detection; and producing a map of the density variations of said object using (i) said first number of photons and said second number of photons, or (ii) said first beam energy and said second beam energy. <EOS>