Lesion size in vibrational Doppler imaging relative to B-scan as a differentiator between benign versus malignant masses in the breast

Abstract

Objective: The aim of this study was to differentiate between benign versus malignant breast masses by lesion size in vibrational Doppler imaging (VDI) relative to B-scan. Methods: VDI uses power Doppler imaging to visualize the tissue vibrational response to externally applied audio-frequency vibration. The VDI apparatus included an audio-frequency transducer driven by a 2-watt audio amplifier and variable-frequency tone generator. The audio transducer was attached to the ultrasound transducer through a vibration-dampening rubber pad. Vibrations at 69–247 Hz were applied to the breasts of 21 patients presenting with 22 histologically confirmed masses. Induced tissue resonance vibrations were visualized by power color Doppler at 6 MHz with color gain at 10–15 dB below typical blood flow settings. Lesion boundaries seen in VDI and B-scan were superimposed for comparison. Results: The breast masses studied included 13 fibroadenomas and fibrocystic masses, one benign phyllodes tumor, and 8 infiltrating ductal carcinomas. Among fibroadenomas and fibrocystic lesions, VDI lesion size was smaller than B-scan lesion size in 9 cases, the VDI lesion boundary precisely followed the B-scan lesion boundary in 3 cases, and the VDI lesion boundary was incomplete at adjacent fat in one case. Although the phyllodes tumor was lobulated, VDI lesion size matched the B-scan. However, in all 8 cases of infiltrating ductal carcinoma, the VDI lesion boundary was irregular (spiculated or lobulated), indistinct, and larger than the lesion seen in B-scan. Conclusions: Irregular and indistinct VDI boundaries with lesion size larger than in B-scan are consistent with invasive neoplastic changes extending beyond the body of malignant tumors. VDI may provide a better estimate of the minimum extent of a primary malignant lesion than B-scan. VDI lesion boundary provides criteria in addition to those of B-scan for differentiating benign versus malignant masses in the breast, thus potentially improving diagnostic confidence.