In vivo assessment of lymph nodes using quantitative ultrasound on a clinical scanner: A preliminary study

Quantitative ultrasound (QUS) methods evaluating the backscattered echo signal provide a means to infer the microstructural properties of soft tissues. High-frequency (≥20 MHz) QUS has been used to detect metastases in excised human lymph nodes (LNs), but limited evidence exists about the efficacy of conventional-frequency QUS for characterizing LNs in vivo using a standard clinical scanner. In this study, 11 LNs from 11 patients with known primary tumors were scanned in vivo using a GE Logiq E9 scanner with a 10-MHz linear array. Metastatic status was determined by fine needle aspiration. Echo frames were processed using QUS methods to compute five parameters from the backscattered echo power spectrum and four from histograms of the echo envelope values. The spectral slope was found to be significantly higher in metastatic nodes (p < 0.001), whereas benign nodes exhibited significantly lower values of spectral intercept (p < 0.001), midband fit (p = 0.004), scatterer diameter (ESD, p < 0.001), and acoustic concentration (EAC, p = 0.003). A linear discriminator operating on ESD and EAC correctly differentiated benign and metastatic nodes with sensitivity of 0.89, specificity of 0.83, and area under the ROC curve of 0.91. These preliminary results demonstrate the feasibility of characterizing LNs in vivo at conventional frequencies using a clinical scanner.