There are 2 products.
The Gammex 156 provides the physical standard baseline for assuring the quality of the images produced by your mammographic system.
The 156 simulates the x-ray attenuation of a 4.2 cm slab of compressed human breast composed of 50% adipose tissue and 50% glandular tissue.
The Gammex 156D Stereotactic Mammographic Accreditation Phantom is used for monitoring digital mammography systems currently used for stereotactic biopsy and localization.
The 156D is accredited by the ACR.