Typically taken of joints with external force applied in a direction that is different from main movement of the joint. Test of stability. Weight-bearing - Generally with the subject standing up HBL, HRL, HCR or CTL - Horizontal Beam Lateral, Horizontal Ray Lateral, Horizontal Central Ray, or Cross Table Lateral. Used to obtain a lateral projection usually when patients are unable to move. Prone - Patient lies on their front Supine - Patient lies on the back Decubitus - Patient lying down. Further described by the downside body surface: dorsal (backside down), ventral (frontside down), or lateral (left or right side down). OM - occipito-mental, an imaginary positioning line extending from the menti (chin) to the occiput (particularly the external occiputal protuberance) Cranial or Cephalad - Tube angulation towards the head Caudal - Tube angulation towards the feet By target organ or structure Breasts Projectional radiography of the breasts is called mammography. This has been used mostly on women to screen for breast cancer, but is also used to view male breasts, and used in conjunction with a radiologist or a surgeon to localise suspicious tissues before a biopsy or a lumpectomy. Breast implants designed to enlarge the breasts reduce the viewing ability of mammography, and require more time for imaging as more views need to be taken. This is because the material used in the implant is very dense compared to breast tissue, and looks white (clear) on the film. The radiation used for mammography tends to be softer (has a lower photon energy) than that used for the harder tissues. Often a tube with a molybdenum anode is used with about 30 000 volts (30 kV), giving a range of X-ray energies of about 15-30 keV. Many of these photons are "characteristic radiation" of a specific energy determined by the atomic structure of the target material (Mo-K radiation). Chest Chest radiographs are used to diagnose many conditions involving the chest wall, including its bones, and also structures contained within the thoracic cavity including the lungs, heart, and great vessels. Conditions commonly identified by chest radiography include pneumonia, pneumothorax, interstitial lung disease, heart failure, bone fracture and hiatal hernia. Typically an erect postero-anterior (PA) projection is the preferred projection. Chest radiographs are also used to screen for job-related lung disease in industries such as mining where workers are exposed to dust. For some conditions of the chest, radiography is