Radiographs, most often called x-rays, produce shadow-like images of bones and certain organs and tissues. They can show some organs and soft tissues, but MRI and CT scans often give better pictures of them.
Another contrast study, an intravenous pyelogram (MVP), uses a special dye to look at the structure and function of the urinary system (ureters, bladder, and kidneys). For instance, in the past, angiography was often used to help learn the stage or extent of cancer, but now CT and MRI scans are most often used to do this.
A special tube inside the x-ray machine sends out a controlled beam of radiation. After passing through the body, the beam hits a piece of film or a special detector.
Tissues that block high amounts of radiation, such as bone, show up as white areas on a black background. Soft tissues block less radiation and show up in shades of gray.
Other than removing metal objects that might interfere with the picture, no special preparation is needed before having a standard x-ray. Always be sure to tell your health care provider whether you have allergies to iodine or have had problems with contrast materials in the past.
You’ll need to remove jewelry or other objects that might interfere with the image. You’ll be asked to sit, stand, or lie down, depending on the body part to be x-rayed.
Your body is put against a flat box or table that holds the x-ray film. The technologist then moves the machine to aim the beam of radiation at the right area.
You may have special shields put over parts of your body near the area being x-rayed so that they’re not exposed to the radiation. Usually the technologist leaves the room to operate the machine by remote control.
Contrast studies Angiography: You’ll be asked to not eat before this test. You will lie still on a table as the skin over the injection site is cleaned and numbed.
A tiny cut will be made so the catheter (thin plastic tube) can be put into a blood vessel (usually the artery at the top of the thigh) and slid in until it reaches the area to be studied. Firm pressure might be needed on the catheter site for a while to make sure it doesn’t bleed.
You’ll also need to lie flat and keep your leg still for up to several hours. Magnetic resonance angiography (MRA) is an MRI study of the blood vessels.
Intravenous pyelogram (MVP): You’ll probably be asked not to eat or drink anything for about 12 hours before this test, and you must take laxatives to clean out your bowel. Another series of x-rays is taken over the next 30 minutes or so to get pictures of the dye as it moves through the kidneys and out of your body.
Pressure may be applied to the belly to help make the image clearer. Once the dye has reached the bladder, you’ll be asked to pass urine while another x-ray is taken.
Lower GI series (barium enema): Your diet may be restricted for a few days before this test. Then liquid barium is put into your bowel through a small, soft tube placed in your rectum.
Upper GI series: You will probably be asked to not eat or drink for 8 to 12 hours before this test. You will lie down and be strapped to a tilting table while a series of x-rays are taken as the barium coats your esophagus and stomach.
You’ll need to swallow the barium mixture a few times during the test. You might also be asked to swallow baking soda crystals to create gas in your stomach.
Venography : As you lie still on a table, the skin over the vein to be used is cleaned and numbed. The contrast dye is put in to make the veins show up on the x-ray, and a series of x-ray pictures is taken.
Extra fluids may be given through the catheter to help wash the dye out of your body. Firm pressure may be needed on the site for a while to make sure it doesn’t bleed.
The contrast material may cause nausea, vomiting, flushing, itching, or a bitter or salty taste. In rare cases, people can have a severe allergic reaction to the contrast material that affects their breathing and blood pressure.
There’s also a small risk of damage to the blood vessel from the catheter, which could lead to internal bleeding. A hematoma (a large collection of blood under the skin) may develop where the catheter was put in if pressure is not kept on the site long enough.
Intravenous pyelogram (MVP): The contrast dye sometimes causes some people to have flushing, mild itching, or a bitter or salty taste. In rare cases, people have a severe reaction to the contrast material and need emergency treatment.
Lower GI series (barium enema): The test can be uncomfortable. The barium contrasts material will make your stools a light color for a few days after the test and may cause constipation.
Your arm or leg (where the catheter is put in) may feel numb during the test. In rare cases, people can have a severe allergic reaction to the contrast material that affects their breathing and blood pressure.
There’s also a small risk of damage to the blood vessel from the catheter, which could lead to internal bleeding. A newer technology, called digital radiology, produces pictures on computer screens rather than on film.
The size and contrast of the pictures can be digitally adjusted to make them easier to read, and they can be sent to computers in other medical offices or hospitals. From the WebMD Archives April 8, 2005 -- When the news that Peter Jennings had lung cancer hit earlier this week, many WebMD users asked why doctors don't use chest X-rays to diagnose lung cancer at an early stage, when it's more treatable.
WebMD turned to cancer expert Harold Burstein, MD, assistant professor of medicine at Harvard Medical School in Boston, for the answer. The vast majority of lung cancer cases are caused by smoking, ” Burstein tells WebMD.
Chest X-rays are inadequate for diagnosing lung cancers at an early stage, when they are more treatable. “By the time lung cancers are discovered on chest X-ray, the tumor is often too far advanced to allow the patient to be cured with surgery or radiation therapy.
The hope was that these CT scans would be able to find smaller, earlier cancers without leading to further unnecessary tests. “A variety of recent studies in the U.S. and Japan have suggested that high-resolution CT scans can often detect lung cancers.
However, he explains that these were small, early studies that were not able to answer the questions of whether CT scans can actually save lives. Continued Burstein says a recent analysis of potential lung cancer screening tests shows there is inadequate data to recommend widespread lung cancer screening at this time.
The report by the federal Agency for Healthcare Research and Quality and the U.S. Preventive Health Services Task Force says evidence that chest X-rays, CT scans, and other forms of screening can save lives is poor. For example, dense materials, such as bone, show up white on a film, while fat and muscle may appear in varying shades of gray.
Today, improvements such as better photographic films, more accurate focusing systems and more sensitive detection methods have led to better imaging technology and results. Advances in technology have led to the development of computed tomography (CT), which combines multiple X-ray images into a 3-D model.
A valuable medical tool, the X-ray is a non-invasive procedure used for diagnosing disease, monitoring therapy and planning surgical treatment. To help identify a specific area of the body on an image, a contrast medium like barium or iodine may be given to patients undergoing certain types of X-rays.
In low doses, X-rays may be used to capture images of structures inside the body to detect and stage a tumor. The image of the chest appears on a film called a radiograph, which shows structures inside the body as light or dark, depending on absorption rates of the different tissues.
Dense materials, such as bone, are white, while fat and muscle appear as varying shades of gray. In low doses, X-rays may be used to construct images of structures inside the body to detect and stage a tumor.