X-ray and Asthma

X-ray and Asthma

Summary

X-rays use small amounts of radiation to produce images of bones and internal organs of the body. One of the oldest forms of creating medical images, x-rays are painless tests routinely used to diagnose diseases and help physicians plan more effective treatment methods.

Bones, joints, the chest and the abdomen are parts of the body frequently examined through x-rays. Physicians can use x-rays to:

  • Screen for disorders of the heart or lungs (e.g., asthma, emphysema, pneumonia)
  • Evaluate infections of the sinuses (e.g., rhinosinusitis)
  • Provide baseline information for diagnosis and future comparison of long-term conditions such as asthma and allergies
  • Detect and diagnose cancer
  • Discover whether or not certain organs are infected
  • Identify the presence of foreign objects (e.g., coins or metal lodged in the esophagus, airway or lungs)

The procedures can be performed in a physician’s office, at a diagnostic laboratory or in a hospital radiology department. The test generally takes only a few minutes and patients are typically asked to remain in one or more positions as a series of x-rays are taken showing different angles of a body part.

Although x-rays expose patients to small amounts of potentially harmful radiation, the risk of serious damage is small when the procedure is done correctly. Most physicians believe the benefits of information learned from x-rays far outweigh any potential risks from the procedure. Women who are pregnant or think they might be pregnant are advised to inform their physician and the x-ray technician performing the test. Exposure to the low levels of radiation may be harmful to developing fetuses.

About x-rays

An x-ray is a painless test in which an image of part of the body is created by using low doses of radiation and recorded on film or fluorescent screens. These images, also known as radiographs or roentgenograms, are used to diagnose and monitor the treatment of various diseases and conditions ranging from asthma to cancer. They are noninvasive, relatively inexpensive and fast.

X-rays produce images using electromagnetic radiation emitted by machines. The x-ray machines produce high-energy photons that pass through the body and are detected by sensitive film. The images projected onto the film are white, black or gray, depending on the ability of photons to pass through the various body parts.

When viewing an x-ray, the following types of images may appear on the film:

  • White images. The density of bone prohibits most photons from passing through, so bones and other dense objects will appear white. Metal and contrast media (chemicals used to outline body areas) block almost all photons and appear bright white.
  • Gray images. Skin, muscle, fat and fluids allow more photons through and produce a gray image. Diseases such as cancer usually will appear lighter than normal, healthy tissue.
  • Black images. A structure that contains air, such as lungs and sinus cavities, will allow even more photons through and appear black.

X-rays are an important diagnostic test for patients with asthma and allergies. Whenever breathing is affected it is important to have a baseline chest x-ray for both future comparison and present diagnosis of allergies and asthma. X-ray images help to distinguish between asthma and other possible causes of breathing problems, such as cystic fibrosis in children and emphysema in adults.

In addition, physicians may order x-rays to:

  • Evaluate infections of the sinuses (e.g., rhinosinusitis)
  • Detect and diagnose cancer
  • Discover whether or not certain organs are infected
  • Identify the presence of foreign objects (e.g., coins or metal lodged in the esophagus, airway or lungs)

How x-rays work

X-rays work by passing small amounts of electromagnetic radiation through the body to produce images of bones, teeth and internal organs. The type of x-rays administered depends on which part of the body needs to be examined.

The x-ray is the oldest imaging technology still in use today. It was discovered in the 1890s by a German scientist named Wilhelm Conrad Roentgen. Because no one understood the rays that were at work in forming these images, the rays were initially called x-rays. Much more is now known about this form of radiation. 

Bones and cartilage (tissue that connects bones and joints) tend to be dense and absorb x-rays better than soft tissues (e.g., skin, fat, internal organs). As a result, bones appear white on x-rays whereas tissues often are gray. Organs or structures containing mostly air, such as the lungs, appear black. Generally, the denser the bone or organ, the more clearly it will show up on an x-ray. The results may first be viewed by a physician with special training in interpreting x-ray results (radiologist) before they are explained to the patient.

An x-ray machine produces a beam of radiation that is pointed by a tube at the part of the body being examined. The area to be examined is placed between the metal film cassette and the x-ray tube, which is surrounded in lead casing except for a small opening through which the rays are beamed. Within the x-ray tube, a beam of electrons is fired into a heavy metal target (e.g., tungsten, copper), emitting photons that travel straight and outward from a point on the target to the area being x-rayed. The resulting images are recorded on film or a fluorescent screen.

The energy contained in the photons may cause some cell damage. Most of this cell damage is repaired quickly, but some may be permanent. Considering the low doses of radiation involved in modern x-rays, most physicians feel the benefits of x-rays outweigh their risks. However, young children and developing fetuses are more sensitive to radiation. Women should advise their physician if they are pregnant or might be pregnant before getting an x-ray.

Additional techniques may be necessary to get a clear view of softer tissues, hollow areas or fluid-filled body parts. For example, a physician may administer a special dye known as a contrast medium to produce sharper contrasts in light and dark areas on the x-ray. These contrasts give the physician a clearer image of areas such as the spinal cord, blood vessels, urinary tract and the gallbladder.

Types and differences of x-rays

X-rays can be used for various purposes. They can help detect broken bones or find the presence of cancer. They also can reveal if an organ is infected. Some of the more common x-ray procedures include:

  • Chest x-rays. Used to help physicians distinguish the nature of a disorder affecting the lungs, such as asthma, chronic obstructive pulmonary disease (COPD), pneumonia or lung cancer. Patients with allergies and asthma should have a baseline chest x-ray performed for future comparison and present diagnosis. If asthma has been recently diagnosed or has suddenly become more severe, x-rays help to classify the disease severity, and rule out the remote possibility that symptoms are cancer-related. Chest x-rays may be recommended for patients with respiratory difficulties.

  • Sinus x-rays. An x-ray of the sinuses (air-filled cavities in the frontal bones of the skull) that can detect an inflammation of the mucous membranes known as rhinosinusitis. Sinus x-rays can also detect the buildup of fluids in the sinuses. Sinus x-rays are also indicated when facial pain suggests sinus disease or if there are nasal polyps. Severe unrelenting asthma may be triggered by sinus disease. However, x-ray results may indicate rhinosinusitis even among people who display no symptoms of infection.

  • Sinus computed tomography (CT) scan. A series of x-rays linked to computer technology that can be used to produce three-dimensional images of internal body structures. A contrast medium may be used with this imaging test.

Other types of imaging tests are available that do not use x-ray technology and may sometimes be preferred. For example, magnetic resonance imaging (MRI) uses a magnetic field and pulses of radio wave energy to provide detailed images of internal body tissue and structures, but without the radiation involved in x-rays. It is more expensive but not as widely available as x-rays. Ultrasound is another type of imaging technology that does not involve x-ray radiation.

Before the x-ray test

Preparation for an x-ray procedure will greatly depend on the nature of the x-ray. Those having x-rays of the chest or sinuses may not need to do anything to prepare for the x-rays. Just before the x-ray, patients may be asked to remove all jewelry or metal objects and change into a hospital gown.   

Patients should keep track of the number of x-rays they have. This information should be shared with the physician, especially when the patient has used more than one primary care physician. While x-rays are generally safe when performed properly, the procedures do expose patients to small amounts of radiation. Therefore, exposure should be limited to medically necessary situations only.

Women who are or might be pregnant should inform their physician and the x-ray technician performing the procedure. X-rays can potentially affect a developing fetus. Non-emergency x-rays may be postponed if a woman is pregnant.

During and after the x-ray test

In some instances, a patient will be given a flexible lead apron to shield portions of the body, particularly the pelvic region and reproductive organs, from exposure to radiation. The neck may need to be shielded during sinus x-rays to protect the thyroid gland. The patient will then be asked to stand, lie or sit while a technician positions the patient’s body in a manner that will facilitate the best possible image.

Once the patient is well-positioned, the x-ray tube attached to the imaging machine will be pointed at the part of the body to be x-rayed. The technician will move behind a protective panel. When everything is in place, the technician will press a button. The x-ray machine will pass a beam of radiation through the part of the body being x-rayed and is absorbed onto special film or fluorescent screen.

Patients will feel no discomfort from the procedure, although they may be asked to lie in uncomfortable positions for brief periods of time. Patients also maybe asked to breathe deeply and hold their breath, or to remain still for periods of time. This helps prevent motion, which can blur radiograph images.

X-ray procedures can last anywhere from a couple of minutes to an hour or more. After the procedure is complete, patients usually can proceed with their normal activities. The x-rays will be read by a radiologist, who will report the results to the patient’s physician. The physician will provide the results to the patient and suggest any additional tests that may be necessary or follow-up visits and treatments.

Potential risks with x-rays

During an x-ray, a small amount of the photons emitted by the x-ray machine passes through the body. The remaining photons are absorbed by the bones, organs and tissues, which can be damaged by the energy in the photons. Most of this damage is reversible through natural healing processes, but some of it may be permanent. There is a very small risk of cancer associated with x-rays. There is also a risk of damage to ovarian cells or sperm cells that can be passed on to offspring. However, experts usually consider the risk relatively low and worth taking considering the benefits of information gleaned from x-rays.

Young children and developing fetuses are more susceptible to damage from x-rays. Women who are or think they might be pregnant should inform their physician. It may be necessary to postpone x-rays or use alternative imaging methods (e.g., ultrasound) to protect the fetus.

In some cases, a contrast medium may be administered prior to the x-ray procedure. The contrast medium may be given orally or intravenously. If intravenous, it may result in soreness at the injection site for a few days after the procedure. In rare cases, patients may experience a reaction very similar to an allergic reaction from contrast medium. This can result in redness, itching, swelling, pain or bleeding at the injection site, a generalized urticarial (hive) reaction, or other systemic reactions much like anaphylaxis. This is called an anaphylactoid reaction. Patients who experience such a reaction to contrast material should consult their physician, or seek immediate medical care in the event of severe symptoms. Patients who have had adverse radio-contrast reactions in the past must be pre-medicated if they urgently require a medical test or procedure that uses contrast.

Questions for your doctor regarding x-rays

Preparing questions in advance can help patients have more meaningful discussions with healthcare professionals regarding their condition. Patients may wish to ask their doctor the following questions about x-ray tests:

  1. Why are you recommending that I undergo an x-ray?
  2. What area will be x-rayed?
  3. What are the risks involved?
  4. Will I need a contrast medium?
  5. Do I need to follow any special preparations?
  6. How long will the x-ray take?
  7. When and from whom will I receive the results?
  8. What type of test results should I consider normal or abnormal?
  9. Will I need any additional tests to make a diagnosis?
  10. How often can I have x-rays?
  11. If I’m pregnant, can I still have an x-ray? Should I take any precautions?
  12. If I do not want an x-ray, is there an alternative test?
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