Breast Cancer Chemotherapy Response Evaluation Using 3-D Power Doppler Ultrasound

The tumor vascularity is a critical factor for growth, invasion, and metastasis. Generally, tumors need more blood vessels to obtain sufficient nutrients for growing and surviving. Recently, the Doppler ultrasound (US) is applied for detecting the blood flow successfully, and the studies of tumor vascularity have played important roles to diagnose diseases of breast and evaluate the therapeutic response of neoadjuvant therapy. In this paper, the three-dimensional (3-D) power Doppler US is adopted for evaluating the vascularity. The conventional vascularity index (VI) method has been broadly used to evaluate the vascularity. However, this method could not provide enough reproducibility for monitoring the chemotherapy response due to the unavoidable displacement between the 3-D volumes scanned before and after the chemotherapy. Hence, a new vascularity evaluation method is proposed to reduce the inaccuracy caused by volume misalignment in this paper. First, the noise reduction algorithm for the vessel image is performed to reduce the noise caused by the systole, breath, and body movement. Second, a predefined threshold value is applied to filter out the less significant vessels and main vessels can be preserved. To revise the misalignment between two 3-D volumes for evaluation, volumes are registered by the image registration technique. After registering the two volumes, the intersection of these two volumes is found and the change ratio of vessel densities in the intersected volume is calculated as the monitor index. In our experiment, the correctness of classifying responder and non-responder by using the vessel density is 100% (9/9). This result is consisted with the conventional evaluation method based on the change of tumor sizes. Furthermore, the accuracy of early prediction by evaluating the vessel densities calculated about 3 weeks after the first chemotherapy is up to 89% (8/9).