A device that consists of a uniform density or a two or three-dimensional (3-D) pattern of objects, materials, or openings of varying dimensions. It includes phantoms that come in both fixed and variable configurations and is a quality assurance (QA) device used in both subjective and quantitative evaluations of various calibration and performance characteristics of ultrasound bone density measurement systems (bone densitometers) and associated image acquisition, display, and analysis computer programs.