Mechanistic analysis of B-line formation in lung ultrasound

Abstract

The number and distribution of lung ultrasound (LUS) imaging artifacts—B-lines—is correlated with the presence of lung interstitial syndrome such as viral infection and pulmonary edema. The detection and quantification of B-lines is machine and operator dependent, and the mechanisms for B-line formation are not fully understood. The goals of this work were to collect RF data during LUS exams in patients with pulmonary edema and to compare to the signals and corresponding images simulated numerically to elucidate the B-line formation process. Verasonics ultrasound engine (VUE) with a phased array probe (4.5 MHz) was used to perform standard 10-zone LUS in ten patients with confirmed pulmonary edema. The RF data corresponding to each B-mode image and a series of 35 plane wave acquisitions were collected for off-line analyses. Finite element modeling of LUS pulse propagation was performed in COMSOL with fluid-filled inclusions of variable sizes and shapes in air-like medium simulating edematous lung areas. The B-mode image resulting from the simulated RF signals was reconstructed using VUE beamforming. The B-lines similar to those observed experimentally formed in simulated images only under specific conditions of sizes and shapes of water-filled areas relatively to LUS imaging wavelength. [Work supported by NIH R01EB023910.]