An X-ray image is produced when a small amount of radiation passes through the body to expose sensitive film on the other side. The ability of X-rays to penetrate tissues and bones depends on the tissue's composition and mass. The difference between these two elements creates the images. The chest X-ray is the most common radiologic examination. Contrast agents, such as barium, can be utilized to highlight the esophagus, stomach, and intestine and are used to help visualize an organ or film.
Computed tomography, otherwise known as a CAT Scan (Spiral Scan Type), shows organs of interest at selected levels of the body. CT examinations produce detailed organ studies by stacking individual image slices. CT can image the internal portion of organs and separate overlapping structures precisely. The scans are produced by having the source of the X-ray beam encircle or rotate around the patient. X-rays passing through the body are detected by an array of sensors. Information from the sensors is computer processed and then displayed as an image.
Like CT, MRI produces images, which are the visual equivalent of a slice of anatomy. MRI, however, is also capable of producing those images in an infinite number of projections through the body. MRI uses a large magnet that surrounds the patient, radio frequencies, and a computer to produce its images. As the patient enters a MRI scanner, his body is surrounded by a magnetic field. The scanner subjects nuclei of the body's atoms to a radio signal, temporarily knocking select ones out of alignment. When the signal stops, the nuclei return to the aligned position, releasing their own faint radio frequencies from which the scanner and computer produce detailed images of the human anatomy.
Ultrasound is a technique that uses sound waves to show a picture of arteries, veins, organs or fetus. Because it uses sound waves instead of radiation, ultrasound is safer than X-rays. Ultrasound has become an increasingly important part of prenatal and general healthcare by providing information that can guide a provider's care plan. Today, up to 70 percent of pregnant women in the U.S. have an ultrasound examination performed.
How does ultrasound work?
Ultrasound works by bouncing sound waves. The echoes from these sound waves are converted into an image — called sonogram. The technique is sometimes called sonography.