High-resolution CT (HRCT) bests chest x-ray when it comes to identifying interstitial lung disease (ILD), according to a presentation delivered at the recent ARRS meeting in Pittsburgh.
Why? Because although chest x-ray is often the initial imaging exam for evaluating ILD, subtle findings can be missed, said presenter Nellie Massey, MD, of the University of Mississippi Medical Center in Jackson.
"CT chest and HRCT imaging provide a more optimal evaluation of [the] findings of early ILD," she noted.
ILDs are a group of conditions characterized by inflammation and subsequent fibrosis of the lung parenchyma and air spaces, Massey explained, and there is significant overlap of radiological findings. What's tricky is that ILD etiologies are "vast and carry significant implications for prognosis and treatment," she said.
"Precise and early diagnosis is essential to preventing progression to end-stage respiratory failure," Massey said. She noted that although the gold standard for evaluating ILD patterns is HRCT, chest x-ray is often used for initial imaging, which can be problematic as "pattern findings can be more difficult to discern, resulting in delays and vastly underestimated incidence rates."
ILD patterns and associated findings may include usual interstitial pneumonia, nonspecific interstitial pneumonia, and pneumoconiosis. Massey outlined the utility and limitations of chest x-ray and HRCT for identifying ILDs, comparing the two modalities in the following manner:
Chest x-ray | HRCT |
Moderate sensitivity and high specificity compared to HRCT; specificity decreases as patients age | Gold standard for ILD evaluation (edge enhancement, volumetric images) |
Low cost, widely available | Expensive and less accessible |
Minimum radiation exposure | Increased radiation exposure |
Often recommended for initial evaluation of pulmonary symptoms | Despite its definitive diagnostic capabilities, HRCT is considered a less suitable initial diagnostic tool |
ACR categorizes use of chest x-ray as "usually appropriate" for chronic dyspnea, unclear etiology, chronic cough lasting more than eight weeks, suspected diffuse lung disease | ACR categorizes use of HRCT as "may be appropriate" for chronic dyspnea, unclear etiology, chronic cough lasting more than eight weeks |
Massey explained that HRCT enables assessment for air trapping on supine expiration -- which "supports or excludes small airway diseases" -- and can image posterior lung inflation on prone inspiration, which allows for "a more accurate summation of the presence and severity of disease" -- a benefit that may translate into better patient outcomes.
"Earlier diagnosis of patients can allow for earlier initiation of treatment with the hopes of preventing or at least slowing the progression of disease," she concluded.
