1. A method of quantitative reconstruction of a human breast of predetermined thickness (H) comprising: using an x-ray source to obtain a plurality of other projection views of the breast where each view is offset by an angle (θ) which might vary or be constant between views, using a reference point in one reference projection view to obtain a reference value P fato for a projection view; estimating the breast thickness variation between a pixel (x) and the x-ray source for each of the other projection views using a total thickness estimation equation; estimating a reference value (P fatj ) for each of the other projection views (I j ) using a reference value estimation equation; using the estimated reference value (P fatj ) for each view to obtain a respective volume of fibroglandular tissue (V i ) for the projection view, (Vo) being the volume for a reference projection view; adjusting the estimated reference value (P fatj ) for each projection view, so that the difference between a volume (V i ) and (Vo) is within a predetermined range; and using the reference values, to determine the volume of fibroglandular tissue in the human breast to a preselected accuracy.