Pneumonia is an infection that causes inflammation within the small air sacs of one or both lungs. To diagnose the condition, physicians rely on a physical exam and imaging tests to see the extent and location of the infection. These tools are important for confirming the presence of pneumonia and guiding treatment decisions.
Why a CT Scan Is Used Instead of an X-ray
A chest X-ray is frequently the initial imaging test ordered when pneumonia is suspected. It is a fast and widely accessible method that provides a general overview of the chest, including the lungs and heart. An X-ray produces a single, two-dimensional image by passing a small amount of radiation through the body. This can reveal larger areas of inflammation or fluid in the lungs that are characteristic of pneumonia.
A Computed Tomography (CT) scan, however, offers a more detailed view. This technology uses X-rays and a powerful computer to create numerous cross-sectional images of the lungs. Think of it as viewing the lung one thin slice at a time, which provides a three-dimensional perspective. This level of detail allows doctors to see fine structures within the lungs, like airways and blood vessels, with exceptional clarity.
This enhanced detail means a CT scan can detect subtle signs of pneumonia that might be missed on a standard X-ray. Early-stage infections or pneumonia in areas of the lung that are difficult to see on a flat image can become visible. The detailed images help a physician understand the infection’s extent and identify any underlying issues within the airway that could be contributing to the pneumonia.
Specific Situations Requiring a CT Scan
A physician may order a CT scan when a chest X-ray does not provide a clear answer. If the X-ray results are inconclusive, a CT scan can offer the clarity needed for a definitive diagnosis and distinguish pneumonia from other conditions.
Another use for CT scans is managing pneumonia for immunocompromised patients. Individuals with weakened immune systems, such as organ transplant recipients or those undergoing chemotherapy, are at a higher risk for severe infections. In these cases, a CT scan can detect pneumonia early and with greater accuracy for timely treatment.
CT imaging is also employed when complications from pneumonia are suspected. A standard X-ray may not clearly show a lung abscess (a collection of pus in the lung tissue) or an empyema (a buildup of pus between the lung and chest wall). A CT scan can precisely locate these complications, guiding medical interventions like drainage.
If a case of pneumonia is severe or not improving with standard treatment, a CT scan may be recommended. For non-resolving pneumonia, the detailed images can help determine if there is an underlying cause, such as an obstructed airway or another lung disease. This helps ensure the treatment plan is appropriate.
What to Expect During the Procedure
When you arrive for a CT scan, you will be asked to lie on a narrow, motorized table that slides into the center of a large, donut-shaped scanner. The machine is large but open, so you will not be fully enclosed. The scan itself is quick and painless.
During the scan, it is important to remain as still as possible to ensure the images are clear. The technologist operating the machine will be in a separate room but can see and speak with you through an intercom. You may be asked to hold your breath for short periods while the images are being captured.
In some cases, a contrast dye may be used to highlight the blood vessels and tissues in the lungs, making them more visible. This dye can be administered orally as a drink or injected into a vein. If an intravenous contrast is used, you might feel a warm sensation throughout your body, which is a normal reaction and subsides quickly. You may also be instructed to fast for a few hours before a scan that uses contrast material.