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Investigating the link between intensity of lung ultrasound vertical artifacts and penetration depth of ultrasound waves, in silico study

Lung ultrasound (LUS) is nowadays widely applied for lung surface evaluation. In particular, LUS is often based on the analysis of vertical artifacts, which correlate with various pathologies but whose genesis is not fully comprehended yet. To better understand the phenomena causing these artifacts' appearance, numerical simulations can represent a powerful tool. Specifically, we present a simulation study (k-Wave MATLAB toolbox) that investigates whether a link exists between the intensity of these artifacts and the penetration depth of ultrasound waves through the lung parenchyma. The size of the simulated numerical domain is 4 cm × 2 cm, with the simulated lung surface located at a depth of 2 cm. Different alveolar structures were modeled by varying the alveolar diameter (from 40 to 800 μm), the inter-alveolar axial-spacing (from 40 to 790 μm) and inter-alveolar lateral-spacing (from 10 to 100 μm). For each configuration, Gaussian pulses (with bandwidth equal to 0.5 MHz at −6 dB) having different center frequencies (from 1 to 5 MHz) were transmitted without focusing (plane wave imaging). Results highlight how the artifacts' intensity seems to be independent from waves' penetration depth.