The impact of B-lines' frequency characterization on lung ultrasound imaging, in vitro- and in vivo study

Abstract

Lung ultrasound (LUS) is an established technique that allows clinicians to evaluate the state of the lung surface. However, LUS is based on the visual evaluation of imaging artifacts (e.g., A- and B-lines) and is hence affected by qualitative and subjective interpretations. Moreover, the impact of imaging settings on the visualization of artifacts is still greatly unknown. To shed light on these fundamental aspects of LUS, the results from two studies are presented. The first analyses through controlled in vitro- experiments the dependence of B-lines on three key imaging parameters, viz., center frequency, focal point, and active-aperture size. The second investigates thanks to a clinical study involving 26 patients the potentiality of B-line frequency characterization to differentiate pulmonary fibrosis from other diseases. A multi frequency imaging approach was used. Center frequencies ranging from 3 to 6 MHz and from 3 to 12 MHz were investigated for the invivo and in vitro- study, respectively. Raw RF data were acquired with a ULA-OP platform and a LA533 linear array probe. Results show that the imaging frequency significantly influenced the intensity of B-lines and that their frequency characterization can be exploited to discriminate fibrotic patients with a sensitivity and specificity equal to 92%.