Evaluating imaging reproducibility of portable ultrasound devices with histogram analysis: a phantom study

Ultrasound (US) imaging is a widely used imaging modality for tumor diagnosis, image-guided intervention, and therapy response assessment in cancer management. However, one major limitation hindering the use of quantitative US is the lack of reproducibility when applied across different institutions and clinical settings. We propose a histogram-based method to examine the imaging reproducibility of US scanners. We tested this method on 8 portable US devices, which included 4 convex and linear dual head scanners and 4 transvaginal probes, providing 3 types of transducers and containing 4 probes of each model. B-mode images were obtained from a Sun Nuclear phantom with fixed scanning settings, and a region of interest (ROI) capturing the uniform background tissue was used to obtain a pixel intensity histogram. Eight histogram-based features were calculated: entropy, meanDeviation, uniformity, mean, median, variance, root-mean-square (RMS), and standard deviation (STDEV). The feature variances among the 4 probes in each group were used to assess their imaging reproducibility. For the convex US transducers, most histogram features varied within 5%. For the linear US, all histogram features varied within 15%. For the transvaginal US, most histogram features varied within 10%. These experiments provide valuable reproducibility measurements of the portable US devices, which are critical for performing multi-center quantitative studies.