Diagnostic imaging is a branch of medicine that makes use of electromagnetic radiation and other technologies to produce images of the body’s internal structures for accurate diagnosis. It is roughly equivalent to radiology, which is the branch of medicine that uses radiation in the treatment and diagnosis of disease. However, in diagnostic imaging, other technologies – which may include ultrasounds and endoscopies – may also be used alongside more traditional, radiation-based imaging. X-rays are the first and most traditional type of radiation used to provide images of the body’s internal structures. One of the limiting factors of x-rays, however, is that they have an inability to distinguish between adjacent, differentiated soft tissues which have roughly the same density. Usually, to achieve the contrast needed, a contrast medium – typically a liquid or gaseous substance that is opaque, or comparatively so, to x-rays or similarly transparent – is injected into the body or otherwise ingested. Contrast medium fluids can be injected into bodily cavities, the bloodstream, and lymphatic vessels, or swallowed or introduced into the body by an enema to study the digestive tract or injected in an organs’ surroundings to show their external contours. Different contrast mediums allow for the x-ray imaging of particular or different types of soft tissue structures, including arties and veins in angiography. Any part of the body can be examined for physiological disturbances through x-ray analysis, and x-ray motion pictures can record the body’s processes as the contrast media enters and leaves different parts of the body. Endoscopy and other related procedures, which make use of flexible optical instruments that are inserted through bodily openings – either naturally occurring or those made during a surgical procedure – are also included in diagnostic imaging. Many instruments used in these scope procedures are outfitted with video cameras, which allow the physician to view the tissues being examined in real-time; certain scopes are also fitted with instruments to allow for tissue biopsies, where a tissue sample is collected for study.