The Mechanisms Underlying Vertical Artifacts in Lung Ultrasound and Their Proper Utilization for the Evaluation of Cardiogenic Pulmonary Edema

Abstract

The recent advances in lung ultrasound for the diagnosis of cardiogenic pulmonary edema are outstanding; however, the mechanism of vertical artifacts known as B-lines used for the diagnosis has not yet been fully elucidated. The theory of “acoustic trap” is useful when considering the generation of vertical artifacts. Basic research in several studies supports the theory. Published studies with pilot experiments indicate that clarification of the relationship between the length and intensity of vertical artifacts and physical or acoustic composition of sources may be useful for differentiating cardiogenic pulmonary edema from lung diseases. There is no international consensus with regard to the optimal settings of ultrasound machines even though their contribution to the configuration of vertical artifacts is evident. In the clinical setting, the configuration is detrimentally affected by the use of spatial compound imaging, the placement of the focal point at a deep level, and the use of multiple focus. Simple educational materials using a glass microscope slide also show the non-negligible impact of the ultrasound machine settings on the morphology of vertical artifacts.

New International Guidelines and Consensus on the Use of Lung Ultrasound

“…LUS can be performed using low MI (see Statement 6), avoiding harmonic imaging and cosmetic filters, keeping the focal point on the pleural line, avoiding saturation phenomena of the pleural line and using the highest frame rate possible 24,39 . Imaging modalities based on compounding should not be utilized, as they can generate deceiving artifactual patterns 247 . Convex or linear probes should be used, according to the patient's body size.…”

The effect of attenuation inside the acoustic traps on the configuration of vertical artifacts in lung ultrasound: an experimental study with simple models

“…Thus, a simple characterization of vertical artifacts can be misleading [ 19 ]. In future clinical studies related to these topics, a certain degree of standardization of machine settings for lung ultrasound should be implemented [ 11 , 18 , 19 , 23 ].…”

“…The depth of the screen was set at 10 cm based on clinical usage recommended in the WFUMB position paper [ 11 ]. A single focal point was set at the distance from the footprint of the transducer to the object being used as the source of a vertical artifact to emphasize the artifact and keep the artifact as narrow as possible [ 9 , 18 , 19 ]. Spatial compound imaging was turned off to avoid generating multiple linear artifacts from the object [ 9 , 18 ].…”

“…A single focal point was set at the distance from the footprint of the transducer to the object being used as the source of a vertical artifact to emphasize the artifact and keep the artifact as narrow as possible [ 9 , 18 , 19 ]. Spatial compound imaging was turned off to avoid generating multiple linear artifacts from the object [ 9 , 18 ]. The dynamic range was set at 72 dB, which is slightly wider than the range used in clinical settings.…”

“…Given the above, we conducted another experimental study using a diagnostic ultrasound scanner to confirm this hypothesis based on a preliminary report [ 18 ].…”