Use of resistance index for the diagnosis of breast tumours

Aim: To determine whether the resistance index (RI) contributes to the differential diagnosis of breast masses. Patients and methods: In 56 breast tumours colour-coded Doppler sonography was performed and their resistance indices calculated from their spectral Doppler tracings. Histologic evaluation was obtained by excision biopsy. Results: In seven of 28 benign tumours (25%) no lesion was seen on ultrasound. In another seven benign tumours, no intratumoral vessels were demonstrated. The resistance index of the remaining 14 lesions (50%) varied between 0.5 and 0.75 with a mean value of 0.62 (standard deviation 0.08). Ultrasound missed one of 28 carcinomas (3.5%) and in one other tumour (3.5%) no flow was demonstrable. The resistance index of 26 malignant tumours varied between 0.56 and 0.9 with a mean value of 0.7 (standard deviation 0.08). Conclusion: Breast malignancies have higher resistance indices with a wider range as assessed by colour-coded Doppler ultrasound (81% exceed 0.6) than do benign lesions. Due to the considerable overlap of the range of the resistance index, the measurements in any single patient may not be diagnostic. The absence of flow does not definitively exclude malignancy.