Does three-dimensional power Doppler ultrasound help in discrimination between benign and malignant ovarian masses?

Objectives: To determine if tumor vascularity as assessed by three-dimensional (3D) power Doppler ultrasound can be used to discriminate between benign and malignant ovarian tumors, if adding 3D power Doppler ultrasound to gray-scale imaging improves differentiation between benignity and malignancy, and if 3D power Doppler ultrasound adds more to gray-scale ultrasound than does two-dimensional (2D) power Doppler ultrasound.

Methods: One hundred and six women scheduled for surgery because of an ovarian mass were examined with transvaginal gray-scale ultrasound and 2D and 3D power Doppler ultrasound. The color content of the tumor scan was rated subjectively by the ultrasound examiner on a visual analog scale. Vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were calculated in the whole tumor and in a 5-cm(3) sample taken from the most vascularized area of the tumor. Logistic regression analysis was used to build models to predict malignancy.

Results: There were 79 benign tumors, six borderline tumors and 21 invasive malignancies. A logistic regression model including only gray-scale ultrasound variables (the size of the largest solid component, wall irregularity, and lesion size) was built to predict malignancy. It had an area under the receiver-operating characteristics (ROC) curve of 0.98, sensitivity of 100%, false positive rate of 10%, and positive likelihood ratio (LR) of 10 when using the mathematically best cut-off value for risk of malignancy (0.12). The diagnostic performance of the 3D flow index with the best diagnostic performance, i.e. VI in a 5-cm(3) sample, was superior to that of the color content of the tumor scan (area under ROC curve 0.92 vs. 0.80, sensitivity 93% vs. 78%, false positive rate 16% vs. 27% using the mathematically best cut-off value). Adding the color content of the tumor scan or FI in a 5-cm(3) sample to the logistic regression model including the three gray-scale variables described above improved diagnostic performance only marginally, an additional two tumors being correctly classified.

Conclusions: Even though 2D and 3D power Doppler ultrasound can be used to discriminate between benign and malignant ovarian tumors, their use adds little to a correct diagnosis of malignancy in an ordinary population of ovarian tumors. Objective quantitation of the color content of the tumor scan using 3D power Doppler ultrasound does not seem to add more to gray-scale imaging than does subjective quantitation by the ultrasound examiner using 2D power Doppler ultrasound.