Ultrasound Elastography of Parotid Gland Tumors: A New Shear Wave Elastography Parameter

Miroslav Heman
Radiology, University Hospital Olomouc, Czech Republic

PURPOSE: The aim of this presentation is to show ability of shear-wave elastography parameters to discriminate benign and malignant lesions in the parotid gland.

METHOD AND MATERIALS: The institutional review board approved this prospective observational study. We performed conventional ultrasound and shear-wave elastography in 124 consecutive patients with parotid gland lesions (58 woman, 66 men aged 15–85 years) one day prior to the surgery. Minimum, maximum, mean and standard deviation elastography parameters were measured using selected region of interest (ROI). These parameters were used to build a predictive model discriminating benign from malignant lesions. The strength of all individual predictors was evaluated by means of univariate analysis (chi-square test or Fisher's exact factorial test in contingency tables). Then a multivariate logistic regression model was built. Its sensitivity and specificity were computed for different cut-off levels and the receiver operating characteristic curve was plotted.

RESULTS: The maximum stiffness was a reliable univariate predictor of malignancy (p=0.0008). Surprisingly, the minimum stiffness was a good predictor as well (p=0.01) in the sense that lower minimum stiffness increased the probability of malignancy. This stifled the predictive value of mean stiffness which was not significant as a predictor of malignancy (p=0.15). The standard deviation of stiffness proved to be a very good predictor (p=0.0004), however, it was affected by the size of ROI. We proposed a coefficient of stiffness variability as the ratio of the maximum and minimum stiffness values. The coefficient of stiffness variability was the strongest univariate predictor of malignity (p<0.0001) – it discriminated malignant from benign lesions better than any other shear-wave elastography parameter.

CONCLUSION: Our newly created coefficient of stiffness variability defined as the ratio of the maximum and minimum stiffness values was found to be the best elastography parameter to discriminate benign and malignant lesion in the parotid gland.

Miroslav  Heman
Miroslav Heman