Assessment of ultrasound image quality in a reference phantom using gel and liquid standoff pads

Abstract

Background

and Methods: This paper presents a review of image quality in ultrasound imaging when using gel and liquid standoff pads, compared to imaging without a standoff pad. Imaging metrics assessed are lateral resolution, nearfield target intensity, and contrast to noise ratio of echogenicity targets. Measurements were made with a Canon Aplio i800 ultrasound system on a standardized ultrasound phantom (Computerized Imaging Reference Systems, Inc.), and custom-made agarose phantoms. Two cases are examined: when the ultrasound images are taken with the probe at different heights above the phantom (the normal clinical use-case for standoff pads); and when the ultrasound probe is artificially always placed at the same height above the phantom (allowing for direct image comparison).

Results and conclusion

The main differences in the standard clinical use-case were observed in nearfield image intensity, with a mean difference of 22.4 ± 11.1 % between highest and lowest positions. Investigation of probes at the same height above the phantom shows that differences appear to be due primarily due to the height of the probe above the phantom, rather than the pads themselves. Elevational beamwidth was found to be a minimum of 2.2 mm at 25 mm axial depth, and adding a standoff pad can change vessel and cyst visualization due to the elevational beamwidth. This is a useful result to be aware of for clinicians using standoff pads on modern ultrasound systems.