On a CT scan, healthy lungs appear a typical size without signs of inflammation. They allow the diaphragm to dome. Lungs with emphysema can look overinflated, with loss of muscle, making the diaphragm misshapen. The destruction of air sacs causes cystic changes.
Computerized tomography (CT) scans allow doctors to look at detailed pictures of a person’s lungs.
They are similar to X-rays, which show larger images of the affected body part.
CT scans can take a range of smaller pictures than X-rays. These potentially give doctors a clearer view of whether a person’s lungs are healthy or have emphysema.
Each lung comprises lobes, or sections. There are three of these in the right lung and two in the left lung. The lobes then contain smaller sections known as lobules. Different types of emphysema affect different parts of the lung.
Centrilobular emphysema is the most common type of emphysema and has a link to smoking. It starts in the central part of the lobules, known as the secondary pulmonary lobules.
To begin with, this type of emphysema looks like small holes on a CT scan. They start to merge as the disease progresses. Centrilobular emphysema destroys or narrows the farthest parts of the airways down to the alveoli (the tiny air sacs in the lungs).
It mainly shows up in the upper part of the lung on CT scans.
Researchers have classified the different stages of disease progression in centrilobular emphysema as follows:
- Trace: Minimal transparent areas taking up less than 0.5% of the lung section.
- Mild: Scattered transparent areas taking up between 0.5% and 5% of the lung section. Large areas of healthy lung separate these areas.
- Moderate: Many well-defined transparent areas taking up more than 5% of the lung section.
- Confluent: A mass of transparent areas spanning several secondary pulmonary lobules. There is no trapped air overinflating the secondary pulmonary lobules or distorting the structure of the lungs.
- Advanced destructive: Transparent areas that span the lobes. Trapped air overinflates the secondary pulmonary lobules and distorts the structure of the lungs.
Learn more about centrilobular emphysema here.
Paraseptal emphysema most often appears in the upper lobes of the lungs on CT scans.
It also has a link to smoking. However, it affects different parts of the secondary pulmonary lobules from centrilobular emphysema, including the:
- mediastinal surface (between the lungs)
- costal surface (between the ribs)
- fissural pleural surface (extensions of the pleural space between lobes of the lungs)
Learn more about paraseptal emphysema here.
CT scans of a lung with panacinar emphysema show a reduction in functional tissue with a narrowing of blood vessels in the affected lung. A person with severe panacinar emphysema may have severe centrilobular emphysema at the same time.
Panacinar emphysema can
This type of emphysema has a link to an inherited condition known as alpha-1 antitrypsin deficiency, which causes lung and liver disease.
CT scans are the most accurate and sensitive method for doctors to find and measure a person’s emphysema if it is severe. The images can show features that regular X-rays may not be capable of picking up, including:
- specific emphysema-related lung damage
- small lung nodules
- small lung cancers
Can CT scans detect mild emphysema?
A study from 2021 in
This is because they expose a person to radiation even though the radiographer may use a low-dose technique.
Learn about the relationship between COPD and emphysema here.
Emphysema is the strongest known imaging biomarker of lung cancer risk, regardless of how extensive a person’s emphysema may be. It may also be a marker of more aggressive tumors.
Healthy lungs are a typical size and with properly functioning diaphragm muscles. Unhealthy lungs may have overinflation with loss of muscle in the diaphragm.
CT scans provide doctors with more detailed pictures of a person’s lungs than X-rays. Doctors may use CT scans to help them measure a person’s emphysema. However, in milder cases of the disease, the risk from radiation exposure may outweigh the benefits of CT scans.