1. Process for use of an osteodensitometry system ( 1 ) using cone beam X-rays with at least two energies, this system comprising an X-ray source ( 1 a ) capable of supplying a cone X-ray beam with at least a first energy called the high energy and a second energy called the low energy and less than the first energy, a two dimensional X-ray detector ( 2 ) and electronic means ( 3 a, 3 b ) for processing images supplied by this detector, this process being characterised in that the low energy image of a part of the anatomy of a patient ( 1 c ) is acquired, and the high energy image of this part of the anatomy is acquired to take patient movements into account in the bone density measurements, and these images acquired at low energy and at high energy are matched before building up the map of bone densities of the part of the anatomy.