Monitoring treatment response with color and power Doppler

Color and power Doppler are now widely used to monitor treatment response because of the latest technologic advances and of the increasing use of echo-enhancing agents. The assessment of treatment response is based on the amount of necrosis obtained and changes in local vascularization indicate a successful treatment. To date, clinical experiences have mainly concerned the treatment of hepatocellular carcinomas, hyperfunctioning nodules of the thyroid and parathyroid glands and the neoadjuvant chemotherapy of breast cancer. Aim of this review is to describe the role and potentials of color and power Doppler in this field. Hepatocellular carcinomas are currently treated with surgery or percutaneous ethanol injection and/or chemoembolization. Treatment response can be monitored with color Doppler: after a successful treatment, color signals are no longer detectable on color Doppler images. Conversely, the presence of arterial signals indicates persistent viable tumor. Unfortunately, color Doppler is limited when the hepatocellular carcinoma is hypovascular, small or deep. Echo-enhancing agents may help overcome these limitations, although spiral computed tomography or dynamic magnetic resonance imaging cannot be replaced yet in the definitive assessment of tumor necrosis. Color and power Doppler are well-established tools in the study of functioning thyroid and parathyroid adenomas after percutaneous ethanol injection. Echo-enhancing agents may improve Doppler sensitivity in the detection of residual viable tissue. Other interesting applications of color and power Doppler in this field are secondary hyperparathyroidism and hyperfunctioning thyreopathies (Graves' disease) treated with mercaptoimidazole. The evaluation of systolic flow velocity in the inferior thyroid artery is more reliable than the quantitative analysis of color signals in monitoring treatment response in Graves' disease. In our experience, systolic velocity in the inferior thyroid artery decreased from 150-250 to 60-80 cm/s after medical therapy. Finally, Doppler studies have provided good results in the follow-up of breast cancers after neoadjuvant therapy. In our experience on 18 patients treated with local parenteral repeated administration of antiblastic drugs, sonography showed no more signals within the lesion in 16 patients at the end of therapy. In the remaining two cases with persistent tumor at ultrasound, some color spots were still present and histopathology confirmed residual tumor cells. In conclusion, the results of color and power Doppler are encouraging. Thus, we believe that Doppler will be increasingly used in monitoring treatment response.