A heart CT scan can reveal lung abnormalities, including lung cancer, as an unexpected discovery. While the primary purpose of this scan is to image the heart and its associated blood vessels, the imaging process captures surrounding chest structures. A heart CT scan is not specifically designed as a screening tool for lung cancer.
How CT Scans Work in the Chest
A Computed Tomography (CT) scan uses a series of X-ray images taken from various angles to create detailed cross-sectional views of the body. For a cardiac CT scan, the machine focuses on capturing precise images of the heart, its chambers, valves, and the coronary arteries that supply blood to the heart muscle. This specialized focus allows for the detection of issues like blockages or structural problems.
During this process, the X-ray beam passes through and images the chest cavity surrounding the heart. This includes the lungs, chest wall, and major blood vessels. While the heart is the central area of interest, adjacent structures like the lungs are also visible in the resulting images.
Incidental Detection of Lung Abnormalities
An “incidental finding” in medical imaging refers to an abnormality discovered on a scan performed for a different reason. Heart CT scans commonly detect lung abnormalities because the lungs are within the scan’s field of view.
Incidental lung findings can range from benign to potentially more serious issues. Common examples include small lung nodules, which are small masses of tissue, or signs of old infections, scarring, inflammation, or enlarged lymph nodes. Pulmonary nodules are the most common, appearing in 5% to 20% of cardiac CT scans. The vast majority of these findings, especially smaller nodules, are benign and not cancerous.
What Radiologists Look For
Radiologists play a significant role in reviewing CT scans, evaluating all tissues within the scan’s field of view, not just the primary area of interest. When an incidental lung nodule or abnormality is identified, radiologists carefully assess several characteristics to determine its significance. These features include the nodule’s size, shape, and its density, which can be solid, sub-solid, or ground-glass.
Nodule margins (smooth or irregular) and the presence of calcification are also evaluated. If previous CT scans are available, radiologists compare the current images to past ones to look for any changes in size or appearance over time. This evaluation helps distinguish between benign conditions, such as old healed infections or granulomas, and findings that might warrant further investigation for malignancy.
Follow-Up After a Lung Finding
If a heart CT scan reveals a suspicious or indeterminate lung finding, specific follow-up steps are recommended. This often begins with further imaging, such as a dedicated low-dose lung CT scan for more detailed views of the lung tissue. In some cases, a PET (positron emission tomography) scan may be recommended to assess the metabolic activity of the nodule to help differentiate between benign and malignant lesions.
Consultation with a pulmonologist or an oncologist is also a common next step. They consider the patient’s overall health, risk factors like smoking history, and the specific characteristics of the finding to determine the most appropriate course of action. If suspicion for malignancy remains high, a biopsy may be necessary for definitive diagnosis.