Abstract
<title>Abstract</title> <p>Objectives: Interstitial lung disease (ILD) is the primary clinical sign of antisynthase syndrome (ASS) and polymyositis/dermatomyositis (PM/DM), with disease progression leading to poor outcomes. Based on achieving early differential diagnosis, we aimed to evaluate the value of the spectral CT quantitative parameters in differentiating ASS-ILD from PM/DM-ILD. Material and methods: This retrospective study involved 69 ASS-ILD patients and 96 PM/DM-ILD patients who underwent spectral and HRCT scans. Quantitative measurements, such as lung lobe volume, 70 keV monoenergetic CT number (MCTN), effective atomic number (Zeff), and electron density (ED), were taken for each lung lobe. We compared the spectral CT parameters between the two groups with the same radiological patterns and features. Results: The ASS-ILD group demonstrated significantly smaller volume, higher MCTN and ED in the right lower lobe (RLL) and the left lower lobe (LLL) (all, p<0.003) compared to PM/DM-ILD group. With the same nonspecific interstitial pneumonia (NSIP) pattern, the values of ED (28.75[22.8, 43.1] vs. 24.6[19.9, 31.65], p=0.026) were higher, and MNCT (-717[-778.95, -570.525]vs -758.2[-803.6, -689.1], p=0.024) was lower in the ASS-ILD group than that in the PM/DM-ILD group in LLL. With the same radiological feature of ground-glass opacity(GGO), the values of ED(29.7[24.1,43.8] vs. 25.3[20.05,32.78], p=0.003), MNCT(-706.3[-763.15, -562.5] vs. -749.7[-802.98, -678.33], p=0.003), and Zeff(6.21±0.37 vs.6.04[5.87, 6.28],p=0.039) were higher in the ASS-ILD group than those in the PM/DM-ILD group in LLL. Receiver operating characteristic (ROC) analysis indicated that the combination of volume, ED, and Zeff in RLL had the best performance for discriminating between ASS-ILD and PM/DM-ILD(AUC = 0.742), with a sensitivity of 75% and a specificity of 69.57%. Conclusion: The quantitative parameters of the spectral CT are capable of distinguishing ASS-ILD from PM/DM-ILD, especially in the lower lung lobes. Even with the same radiological patterns and features, the spectral CT can be used to differentiate the two diseases.</p>