Chest Imaging

Chest imaging studies include

(See also Medical History and Physical Examination for Lung Disorders Medical History and Physical Examination for Lung Disorders A doctor first asks the person about symptoms. Chest tightness or pain, shortness of breath ( dyspnea) either at rest or during exertion, cough, coughing up of sputum or blood (hemoptysis),... read more and Respiratory System Overview of the Respiratory System To sustain life, the body must produce sufficient energy. Energy is produced by burning molecules in food, which is done by the process of oxidation (whereby food molecules are combined with... read more .)

X-rays of the chest are almost always done when doctors suspect a lung or heart disorder. Other imaging tests are done as needed to provide doctors with specific information to make a diagnosis.

Chest x-rays are routinely taken from the back to front. Usually a view from the side is also taken. Chest x-rays provide a good outline of the heart and major blood vessels and usually can reveal a serious disorder in the lungs, the adjacent spaces, or the chest wall, including the ribs. For example, chest x-rays can show most pneumonias, lung tumors, chronic obstructive pulmonary disease, a collapsed lung (atelectasis), and air (pneumothorax) or fluid (pleural effusion) in the pleural space. Although chest x-rays seldom give enough information to determine the exact cause of the abnormality, they can help a doctor determine whether and which other tests are needed to make a diagnosis.

Computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT) of the chest provides more detail than a plain x-ray. With CT, a series of x-rays is analyzed by a computer, which then provides several views in different planes, such as longitudinal and cross-sectional views. During CT, a substance that can be seen on x-rays (called a radiopaque contrast agent) may be injected into the bloodstream or given by mouth to help clarify certain abnormalities in the chest. High-resolution CT and helical (spiral) CT are more specialized CT procedures. High-resolution CT may reveal more detail about lung disorders. Helical CT can provide three-dimensional images. Generally, CT scans are done after a person takes a deep breath (inhales). Sometimes, CT images are obtained after people both inhale and exhale to better look at small airways.

CT angiography CT angiography In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more uses a radiopaque contrast agent injected into an arm vein to produce images of blood vessels, including the artery that carries blood from the heart to the lungs (pulmonary artery). Currently, CT angiography is usually done instead of nuclear lung scanning to diagnose blood clots in the pulmonary artery (pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or... read more ). However, CT angiography may not be possible if a person has kidney disease, which can be worsened by the contrast agents, or allergies to the contrast agents Allergic-type contrast reactions During imaging tests, contrast agents may be used to distinguish one tissue or structure from its surroundings or to provide greater detail. Contrast agents include Radiopaque contrast agents... read more used.

Magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI) also produces highly detailed pictures that are especially useful when a doctor suspects blood vessel abnormalities in the chest, such as an aortic aneurysm Overview of Aortic Aneurysms and Aortic Dissection The aorta, which is about 1 inch (2.5 centimeters) in diameter, is the largest artery of the body. It receives oxygen-rich blood from the left ventricle of the heart and distributes it to all... read more . However, MRI takes longer to do and is more expensive than CT. Also, the resolution of MRI is lower than CT for diagnosing abnormalities in the lungs, and therefore MRI is not frequently used for chest imaging. Unlike CT, MRI does not use radiation.

Ultrasonography Ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more creates a picture from the reflection of sound waves in the body. Ultrasonography is often used to detect fluid in the pleural space (the space between the two layers of pleura covering the lung and inner chest wall). Ultrasonography can also be used for guidance when using a needle to remove the fluid. Bedside ultrasonography is sometimes done to diagnose pneumothorax Pneumothorax A pneumothorax is partial or complete collapse of the lung due to the presence of air between the two layers of pleura (thin, transparent, two-layered membrane that covers the lungs and also... read more . Endobronchial ultrasonography (EBUS) can be used together with bronchoscopy Bronchoscopy Bronchoscopy is a direct visual examination of the voice box (larynx) and airways through a viewing tube (a bronchoscope). A bronchoscope has a camera at the end that allows a doctor to look... read more to help guide doctors when they need to obtain a sample of lung tissue to look for cancer (needle biopsy Needle Biopsy of the Pleura or Lung A needle biopsy is a procedure in which a biopsy needle is inserted into the lung or through the membrane surrounding the lung (pleura) and is used to remove a piece of tissue for examination... read more ). In this case, the ultrasound probe is located on the bronchoscope to obtain images from inside the airways.

Nuclear lung scanning Radionuclide Scanning In radionuclide scanning, radionuclides are used to produce images. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more can be useful in detecting blood clots in the lungs (pulmonary emboli) but has largely been replaced by CT angiography CT angiography In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more to diagnose this disorder. However, nuclear lung scanning may be done when CT angiography is not possible because a person has kidney disease, which can be worsened by the contrast agents, or allergies to the contrast agents used in CT. Nuclear lung scanning also may be used during the preoperative evaluation of people having part of their lung removed to treat lung cancer Lung Cancer Lung cancer is the leading cause of cancer death in both men and women. About 85% of cases are related to cigarette smoking. One common symptom is a persistent cough or a change in the character... read more or severe chronic obstructive pulmonary disease Chronic Obstructive Pulmonary Disease (COPD) Chronic obstructive pulmonary disease is persistent narrowing (blocking, or obstruction) of the airways occurring with emphysema, chronic obstructive bronchitis, or both disorders. Cigarette... read more (COPD) to see how well the rest of the lungs are functioning. Nuclear lung scanning uses minute amounts of short-lived radioactive materials to depict the flow of air and blood through the lungs. Usually, the test is done in two stages. In the first stage (lung perfusion scan), a radioactive substance is injected into a vein, and a scanner creates a picture of how it is distributed throughout the blood vessels of the lung. If the perfusion scan is abnormal, a second stage is necessary (lung ventilation scan). In a lung ventilation scan, the person inhales a radioactive gas, and a scanner creates a picture of how the gas is distributed throughout the lungs. This procedure enables doctors to determine whether the remaining lung is able to absorb enough oxygen.

Pulmonary artery angiography (also called pulmonary artery arteriography) is done by injecting a radiopaque contrast agent directly into the pulmonary artery through a long, thin plastic tube (catheter) passed through a vein, into the heart and then into the pulmonary artery. After the contrast agent is injected, doctors use conventional x-rays to view the contrast agent in the lungs (angiography Angiography In angiography, x-rays are used to produce detailed images of blood vessels. It is sometimes called conventional angiography to distinguish it from computed tomography (CT) angiography and magnetic... read more ). Angiography has traditionally been used most often when pulmonary embolism was suspected, usually on the basis of abnormal lung scan results, and is still considered the most accurate test for diagnosing or excluding pulmonary embolism. However, currently, angiography of the pulmonary arteries is usually done instead with CT angiography because pulmonary artery angiography, involving an injection directly into the large pulmonary artery, is more invasive.

Positron emission tomography Positron Emission Tomography (PET) Positron emission tomography (PET) is a type of radionuclide scanning. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more (PET) scanning may be used when cancer is suspected. This radiographic imaging technique relies on different metabolic rates of malignant (cancerous) compared with benign (noncancerous) tissues. Glucose molecules are combined with a compound that is visible using PET. These molecules are injected intravenously and accumulate in rapidly metabolizing tissue (such as in cancerous lymph nodes), making these tissues visible on PET scans. Benign growths usually do not accumulate enough molecules to be visible. PET scans are often combined with CT scans to provide two different methods to visualize lung tumors.