outside the phantom the preferred contents include a sample of human bone tissue for example the proximal end of the femur 20 or a lumbar vertebra not shown the utility of a bone sample is in adjusting the x ray machine for common exposure of skeletal parts such exposure represents one of the basic uses of x ray equipment a container of aqueous solution of iodine contrast agent 22 as is commonly used in the x ray art is included as an aid in identifying human organs within container 22 illustrated as approximating the shape of a gallbladder may be placed several small stones 23 of composition similar to gallstones these stones 23 are best shown in fig4 and represent a subject requiring careful machine adjustment for good x ray pictures because phantom 10 may be x rayed from any side or angle the stones may be viewed in a variety of positions as they shift within container 22 according to its orientation with respect to the ground another difficult x ray job is locating polypoids and container 25 is included to simplify the task this container holds a contrast agent 26 such as barium sulfate bas0 4 suspended in a heavy medium such as heavy oil or molasses the interior sides of container 25 support several modules 27 of dense material such as silicone rubber which radiographically simulate occupying lesions otherwise known as polypoids barium sulfate is a commonly used contrast agent in x ray investigation of the digestive tract and it is used in container 25 to.