It is estimated that more than 110 million active mines are a permanent threat in some 70 countries, resulting in about 2000 casualties per month, most of them being civilians. The anti-personnel mines (APM) and anti-tank mines (ATM) found in several affected countries are mostly buried, non-metallic or with minimum metal content.
Using the classical technologies (metal detector, dogs, prodding) finding, localizing and identifying the landmines is a time consuming, expensive and extremely dangerous procedure. In addition, it will take a long time to de-mine the affected countries, mainly because the same tedious procedure has to be applied to all areas suspected to be contaminated with landmines. Mined areas are generally close to the battlefields, being consequently heavily infested by metal pieces from the explosions of different ordnances (explosion of an ordnance can result in more than 1000 small metal fragments). The presence of metal clutter produces a large number of false alarms in the metal detectors (MD) commonly used in de-mining. As a consequence, there is a need for a technological breakthrough in this field to solve definitively the land-mine problem.
X-ray or gamma-ray based imaging is the only technique which enables a direct view of objects embedded or buried in soil. State of the art systems can give good precision density measurements with high-resolution three-dimensional images. The observed shapes and mechanical structure of detected objects may help to identify a particular mine type or at least to distinguish a mine from other buried objects such as metal scrap. Metal can be distinguished further by the available gross information about the elemental content of the inspected item (low Z vs. high Z discrimination). Recent examples of systems under investigation will be discussed as well as emerging ideas of combining gamma and neutron detection to further increase the sensitivity and selectivity of such systems.