A lung scan is a medical imaging procedure used to visualize the internal structures of the chest, particularly the lungs and their surrounding blood vessels. These tests employ various technologies to create maps of the pulmonary system, helping healthcare providers identify abnormalities. The procedure is typically ordered when a person experiences respiratory symptoms such as a persistent cough, shortness of breath, or chest discomfort. Lung scans provide detailed images necessary for diagnosing a wide range of conditions and monitoring treatment effectiveness.
Defining the Purpose of a Lung Scan
A primary function of lung imaging is to identify blood clots within the pulmonary arteries, a serious condition known as a pulmonary embolism. When a blood clot is suspected, the scan quickly locates the blockage, which disrupts normal blood flow to the lung tissue. Imaging is also used for the early detection and evaluation of suspicious masses or nodules, which may indicate lung cancer. For individuals at high risk, a low-dose computed tomography (CT) scan is often recommended as a routine screening measure.
Lung scans are further used to assess the extent of damage from chronic lung diseases, such as emphysema or Chronic Obstructive Pulmonary Disease (COPD). Scans provide anatomical and functional details regarding the air sacs and airways, helping to stage the disease or plan interventions. A lung scan can also identify infections, including pneumonia, by showing areas of consolidation or fluid buildup. This visualization aids in accurate diagnosis, allowing for the timely initiation of medical care.
Common Imaging Technologies Used
Several different imaging modalities are categorized under the umbrella of a “lung scan,” each using a distinct method to capture images of the chest. The most fundamental method is the Chest X-ray, which uses ionizing radiation to create a two-dimensional image of the heart, lungs, and bones. While quick and widely accessible, its utility is limited to detecting large abnormalities like significant fluid accumulation or pronounced infections.
A more detailed examination is provided by a Computed Tomography (CT) scan, which utilizes a rotating X-ray beam and computer processing to generate cross-sectional “slices” of the lungs. This technology offers superior spatial resolution, making it effective at detecting small pulmonary nodules or characterizing complex lung diseases like fibrosis. Low-dose CT scans use less radiation and are employed for annual lung cancer screening in eligible patients.
Another specialized method is the Ventilation-Perfusion (V/Q) scan, a nuclear medicine procedure that focuses on lung function rather than anatomy. The test involves two parts: a ventilation scan, where the patient inhales a radioactive gas to map air distribution, and a perfusion scan, where a tracer is injected into a vein to map blood flow. Comparing these two maps is effective for diagnosing pulmonary embolisms, as a mismatch between ventilation and perfusion suggests a blockage in the blood supply. Less frequently, Magnetic Resonance Imaging (MRI) is used to evaluate soft tissues without radiation, and Positron Emission Tomography (PET) scans are combined with CT to assess the metabolic activity of suspected tumors.
What Happens During the Procedure
Preparing for a lung scan generally involves few specific restrictions. Patients are typically instructed to remove all metal objects, including jewelry, eyeglasses, and clothing containing metal fasteners. This precaution is necessary because metal can interfere with the imaging equipment, causing artifacts that obscure the diagnostic quality. For certain types of CT scans that use an intravenous (IV) contrast dye to enhance the visibility of blood vessels, patients may be asked to fast for a few hours before the appointment.
During the scan, the patient lies on a motorized table that slides into a large, doughnut-shaped machine. A technologist operates the equipment from a separate control room but remains in communication with the patient via an intercom system. The patient must remain completely still throughout the imaging process. The technologist may ask the patient to briefly hold their breath to prevent movement blur, especially during a CT scan.
The total time spent in the scanning room is usually brief, often lasting only a few minutes for image acquisition, though the entire appointment typically takes about 30 minutes. If a V/Q scan is performed, the patient will either breathe a radioactive gas through a mask or receive a tracer injection into an arm vein. Following the procedure, most people can immediately resume their normal daily activities.