CT Density Distribution Analysis in Patients with Cystic Fibrosis: Correlation with Pulmonary Function and Radiologic Scores

Rationale and Objectives: The progressive changes in lung morphology observed in cystic fibrosis (CF) can potentially affect the statistical distribution of computed tomography (CT) density values. This study aimed to characterize the lung CT density distributions by quantifying indices of the kurtosis and skewness of the lung density distribution and to compare these indices to radiologic scores and lung function parameters in children and young adults with CF. Materials and Methods: CT scans and lung function of 26 patients with CF were retrospectively examined. The Bhalla radiologic scoring was performed separately, in random order, by two expert radiologists, blinded to the patient's identity, age, clinical status, results of lung function tests, and the other paired observer's score. Results: Positive relations were evidenced between the log indices of lung density distribution kurtosis (iKurtosis) and the overall radiologic scores (RS) of both observers (R = 0.58; P<.001 vs RS1 and R = 0.71; P<.001 vs RS2). A similar relationship was evidenced with the log index of the degree of distribution asymmetry (iSkewness; R = 0.62; P<.001 vs RS1 and R = 0.62; P <.001 vs RS2). Log-iKurtosis and log-iSkewness were related to FEV1 (R = -0.56; P <10(-5) and R = -0.55;P<10(-5)) and to residual volume (R = 0.40; P<.001 and R = 0.45; P<.001, respectively). Both radiologic scores showed significant relation with lung function. The correlation between RS1 and RS2 was excellent (R = 0.93), with a Cohen weighted kappa of 0.43. Conclusions: Characteristic indices of lung CT density distribution are correlated to lung function and radiologic scores in patients with CF and merit further evaluation as part of more comprehensive automated methods for quantifying CF lung CT data.