Differences in ultrasound elevational beam width (slice thickness) between popular handheld devices

Background: Handheld ultrasound devices are increasingly used by medical professionals for bedside ultrasound-guided interventions. Especially for vascular access procedures, the width of the imaging plane, known as the slice thickness or elevational beam width is a prominent source for misinterpretation. A wide slice thickness can lead to the interpretation that 2 objects (i.e. needle and vessel) are on the same plane while in fact they are not and thereby negatively influencing the performance of in-plane ultrasound-guided interventions. Therefore, the beam profiles of three popular handheld US devices are tested and compared to a conventional US device. Methods: The GE VScan, Philips Lumify and Butterfly IQ ​+ ​are tested using a slice phantom to determine the slice thickness. For comparison, a Philips Affiniti machine was investigated. Both linear and curved array settings were analyzed. In a slice phantom, a diffuse scattering plane at an angle of exactly 45° is scanned. For each imaging depth, the vertical height of the imaged rectangle corresponds to the slice thickness at that depth. Main results: For the linear array transducers, the focus depth ranges from 1.5 to 3.5 cm. At the focus depth, all transducers have a reasonable slice thickness of approximately 1 mm. More superficially, the slice thickness varies between 1 and 4 mm. The curved array probes have larger focus depths, ranging from 2.7 to 7.3 cm. The slice thickness at focus depth varies between 1.4 and 3.8 mm, but at 2 cm depth is even more than 5 mm. Conclusions: The slice thickness of handheld ultrasound transducers varies between the different devices, and can be suboptimal for superficial in-plane ultrasound-guided interventions. The larger slice thickness of the curved array settings may complicate in-plane guidance. Handheld ultrasound users should be aware of the beam characteristics of their devices to optimize guidance for interventions.