ABSTRACT
This paper proposes a quantitative analysis method for lung ultrasound (LUS) images to evaluate the severity of COVID-19 pneumonia. Specifically, biomarkers related to the pleural line, including the thickness of pleural line (TPL) and the roughness of pleural line (RPL), and biomarkers related to the B-lines, including the accumulated width of B-lines (AWBL) and the acoustic coefficient of B-lines (ACBL), are extracted from LUS images to characterize the image patterns associated with the disease severity. 27 patients of COVID-19 pneumonia are enrolled in this study, including 13 moderate cases, 7 severe cases, and 7 critical cases. Patients of moderate cases are regarded as non-severe patients, and patients of severe and critical cases are regarded as non-severe patients. Biomarkers among different cases are compared, and the performances in the binary diagnosis of severe and non-severe patients are assessed using a support vector machine (SVM) classifier with all the biomarkers as the input. The classification performance is optimal using the SVM classifier (area under the receiver operating characteristics curve = 0.93, sensitivity = 0.93, specificity = 0.85). The proposed method may be a promising tool for the automatic grading and follow-up of patients with COVID-19 pneumonia. © 2021 IEEE.
ABSTRACT
BACKGROUND AND OBJECTIVE: Lung ultrasound is an inherently user-dependent modality that could benefit from quantitative image analysis. In this pilot study we evaluate the use of computer-based pleural line (p-line) ultrasound features in comparison to traditional lung texture (TLT) features to test the hypothesis that p-line thickening and irregularity are highly suggestive of coronavirus disease 2019 (COVID-19) and can be used to improve the disease diagnosis on lung ultrasound. METHODS: Twenty lung ultrasound images, including normal and COVID-19 cases, were used for quantitative analysis. P-lines were detected by a semiautomated segmentation method. Seven quantitative features describing thickness, margin morphology, and echo intensity were extracted. TLT lines were outlined, and texture features based on run-length and gray-level co-occurrence matrix were extracted. The diagnostic performance of the 2 feature sets was measured and compared using receiver operating characteristics curve analysis. Observer agreements were evaluated by measuring interclass correlation coefficients (ICC) for each feature. RESULTS: Six of 7 p-line features showed a significant difference between normal and COVID-19 cases. Thickness of p-lines was larger in COVID-19 cases (6.27 ± 1.45 mm) compared to normal (1.00 ± 0.19 mm), P < 0.001. Among features describing p-line margin morphology, projected intensity deviation showed the largest difference between COVID-19 cases (4.08 ± 0.32) and normal (0.43 ± 0.06), P < 0.001. From the TLT line features, only 2 features, gray-level non-uniformity and run-length non-uniformity, showed a significant difference between normal cases (0.32 ± 0.06, 0.59 ± 0.06) and COVID-19 (0.22 ± 0.02, 0.39 ± 0.05), P = 0.04, respectively. All features together for p-line showed perfect sensitivity and specificity of 100; whereas, TLT features had a sensitivity of 90 and specificity of 70. Observer agreement for p-lines (ICC = 0.65-0.85) was higher than for TLT features (ICC = 0.42-0.72). CONCLUSION: P-line features characterize COVID-19 changes with high accuracy and outperform TLT features. Quantitative p-line features are promising diagnostic tools in the interpretation of lung ultrasound images in the context of COVID-19.