Sonoelastographic strain ratio: how does the position of reference fat influence it?

Purpose: The purpose of this study was to evaluate how the reference fat position influenced the calculation of the sonoelastographic strain ratio. Methods: Three hundred fifty-eight breast masses (256 benign lesions and 102 malignant lesions) in 300 women (mean age 47.4 years; age range 17–82 years) who had been scheduled for a percutaneous needle biopsy or surgical excision were examined using B-mode ultrasonography and elastography. The sonoelastographic strain ratio was calculated twice per lesion; once by dividing the strain value of the fat near the mass by that of the mass (FLR 1) and once by dividing the strain value of the subcutaneous fat by that of the mass (FLR 2). Results: Most (91.9 %) showed a difference of less than 0.5 between FLR 1 and FLR 2 values. Regardless of the position of reference fat, there was no statistically significant difference between the FLR 1 and FLR 2 values (p value = 0.077 and 0.0825, respectively). According to the pathology of the lesion, a difference between FLR 1 and FLR 2 less than 0.5 occurred in 95.3 % of the benign lesions and 84 % of the malignant lesions (p < 0.001). Conclusions: The sonoelastographic strain ratio was not significantly affected by the position of reference fat.