Understanding lung ultrasound artifacts using a phantom lung model

Abstract

Lung ultrasound has become increasingly utilized as a diagnostic tool in chest trauma and more recently, to differentiate respiratory failure and types of circulatory shock. Extravascular lung water (EVLW) refers to lung water outwith the lung vasculature. There is evidence suggesting lung ultrasound as an ideal point-of-care investigation to assess EVLW. Diseased lungs have better ultrasound penetration and resolution, producing ultrasound artifacts known as B-lines. The association between the presence of B-lines and increased EVLW demonstrates a useful and responsive measure of EVLW changes. However, there has been limited study assessing B-line artifacts as a function of EVLW volume. This project aims to recreate A-line and B-line ultrasound artifacts using a phantom lung model, and determine the factors influencing changes in these artifacts, and the possibility of quantifying these changes. A phantom lung model was created from melted gel wax and placed over an air-filled plastic container with 10µL and 200µL pipette tips, and 0.5mL tube embedded within the model. The results showed that scanning empty pipette tips and tube created A-lines. B-lines were created by scanning pipette tips and tube filled with liquid (i.e. water, Gelofusin, and plasma) and semisolid (i.e. meshed gel wax) materials. The thickness of phantom model is directly proportional to the distance between A-lines, but inversely proportional to the number of A-lines. The B-lines in pipette tips filled with water showed broader distance between each B’-lines compared to pipette tips filled with meshed gel wax. The average length of B-lines appears to increase with increasing meshed gel wax weight. The distance between each B’-lines appears to be shorter in water-filled and plasma-filled compared to Gelofusin-filled tubes. Although there were factors demonstrating good association with ultrasound artifacts, there were several limitations identified. Further improvement to the phantom model design is required for more accurate study.