A method and system for determining the bone mineral density of a body extremity. An image of a body extremity is acquired using a mammography x-ray system whereby a bone mineral density can be performed on the image. The system for determining the bone mineral density of a body extremity includes: a support for supporting the body extremity; a detector for capturing an image of the body extremity; and an x-ray source adapted to project an x-ray beam through the body extremity toward the detector, the x-ray source having a voltage of no more than about 45 kVp and having a target/filter combination of rhodium/rhodium, molybdenum/molybdenum, molybdenum/rhodium, or tungsten/rhodium. An attenuation filter separate from the target/filter combination may be provided between the source and the body extremity, between the body extremity and the detector, or both.