The non-destructive test of a structure (10) such as an aircraft fuselage is done by placing an X-ray source (16) on one side of the structure, and placing a digital camera (24) on the other side. The microcomputer (28) analyzes the image output by the digital camera in real time. If this image is unusable, at least one setting of the source (16) is modified immediately and a new acquisition is made without wasting any time. The adjustment can then be made manually or using a slaving system. The adjustment may relate to the wave length of the X-ray beam, the dose level or the pose time if the fault concerned is related to the gray level of the image. If a directional source is being used, the defect may also have an influence on the sharpness of the image and may be caused by an alignment problem.