Lung disease can be imaged by taking three-dimensional photos of the lungs, commonly called CT scans. CT scans can identify areas of lung damaged by diseases, such as lung fibrosis. Lung CT scans are typically assessed in a hospital by a specialist imaging doctor, called a radiologist. While radiologists can diagnose a disease on the CT scan well, estimating precisely how much of the lungs are damaged can be very challenging. Looking at over 500 images of a CT scan and calculating what percentage of the lung is damaged on each image is very complicated and time-consuming. Using computers to accurately quantify the amount of damage on a CT scan could be a possible solution. Computers can also be trained by humans to identify patterns of disease on CT imaging previously overlooked by radiologists. In lung fibrosis, where imaging appearances are complex, this could help identify important disease patterns that predict future clinical deterioration.
Our study used a computer algorithm trained to identify an imaging pattern called pleuroparenchymal fibroelastosis (PPFE) in patients with idiopathic pulmonary fibrosis (IPF). PPFE occurs in parts of the lung far away from typical IPF-related lung damage. We calculated the amount by which PPFE changes over two CTs scans performed on average a year apart (Figure 1a). We performed two analyses: first in 414 IPF patients and second in 98 patients with another lung fibrosis disease called fibrosing hypersensitivity pneumonitis (FHP).
Our study findings showed that between 22–26% of IPF and FHP patients had progressive PPFE (Figure 1b: see red arrow). Worsening of PPFE was unrelated to the severity of worsening of underlying fibrosis. Worsening PPFE predicted the time to death for patients with IPF and FHP, regardless of how severe and progressive their underlying fibrosis was.
These results indicate that PPFE is a disease process that occurs independent of the rate of worsening of underlying lung fibrosis. Importantly, PPFE may be a second pathological phenomenon that worsens life expectancy in patients with lung fibrosis.
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[Published May 2023]