What is a Lung Scan?

A lung scan is a medical test conducted to screen for abnormalities in the lungs. An individual may be advised to have a scan of the lungs if he or she is exhibiting specific symptoms. These symptoms may include shortness of breath, coughing up blood, chest pain, wheezing and a persistent cough. A person with an existing lung disease may undergo a scan to learn of the disease progression. In addition, individuals suspected to have blood clots in the lungs may have a scan to confirm or rule out the possibility.

One type of lung scan is a ventilation scan, which is usually done to determine the lung's ability to ventilate air. For this type of scan, a patient will wear a special mask covering the mouth and nose. He or she will be asked to inhale a special tracer gas. Special cameras will capture multiple pictures as the tracer travels through the lungs. In most cases, the patient is instructed to exhale and inhale at various times throughout this test.

A ventilation scan is usually combined with a perfusion scan. This type of lung scan is most often used to analyze blood flow within the lungs. During this scan, a radioactive tracer is injected into the patient's vein. A special camera is used in this scan as well to highlight the radioactive tracer as it travels through the veins and into the cavities of the lungs. Blood circulating equally in the lungs will show an even distribution of the tracer, while abnormal blood flow will be unevenly distributed.

Ventilation and perfusion scans are commonly done when a doctor suspects a patient may have a blood clot. These tests may also be done to diagnose pulmonary embolism, a blockage of one or more lung arteries, which is caused by blood clots. Pulmonary embolism can cause a disruption of both the air flow and blood circulation in the lungs. In most cases, the results of ventilation and perfusion scans are similar in a person with healthy lungs. Significantly unequal results will generally indicate some type of lung abnormality.

If a doctor suspects lung cancer, he or she may order an additional lung scan. He or she may order an imaging test. This may include a lung magnetic resonance imaging (MRI), lung positron emission tomography (PET) or computerized tomography (CT) scan of the lungs. These types of scans may be done as part of a lung cancer screening. They may also be conducted in an individual with an existing diagnosis of lung cancer.

Doctors may order just one lung scan for a patient or multiple ones. Generally, an individual's symptoms and health history may factor into the type of scan he or she undergoes. Certain scans may be more suitable for some patients than others. After undergoing a scan of the lungs, doctors will call the patient and inform him or her of the results. The results can provide relevant information on what, if any, treatment may be necessary following a scan.