DECAY CONSTANT OF DOPPLER FLOW WAVE-FORM AS A POSSIBLE INDICATOR OF OVARIAN MALIGNANCY

The objectives of this study were to analyze the decay constant (tau) of the Doppler flow waveform in ovarian tumors; to determine if differ ences in this constant can discriminate between malignant and benign o varian tumors; and to compare the decay constant to the known resistiv e index (RI), in order to determine its potential prognostic applicati on. Patients with ovarian masses (46) were evaluated in a retrospectiv e study; 13 had malignant tumors, 7 showed tumors with low malignant p otential (LMP), 11 had benign masses, 4 had secondary ovarian metastas es and 11 had functional ovarian masses. Doppler flow waves measured i n the ovary before operation were analyzed from archival videotapes. T he RI was calculated preoperatively, and the decay constant of the flo w waveform was analyzed retrospectively. We approximated the decaying portion of the how waveform from the systolic peak to the diastolic le vel to an exponential curve. Then, the decay constant associated with the flow signal was compared for different types of ovarian pathology. Ovaries with malignancies showed significantly higher mean values for the decay constant (89.7; 95% confidence interval 60.0-119.3) than th ose with benign tumors (41.8; 25.7-57.9) (p < 0.007), where tau is pro vided in pixels (in this study each pixel equals approximately 11.4 ms ). The mean RI value for malignant tumors was 0.44 +/- 0.12 whereas, i n benign tumors, it was 0.622 +/- 0.11. For the benign tumors, both ta u and RI did not differ significantly from the measured indices in LMP tumors, metastases and functional ovarian findings. In addition, when the cutoff value of tau was set at 48, 92.3% of all malignancies were identifiable using only tau. This preliminary study indicates that th e decay constant of the Doppler flow waveform is able to discriminate between malignant and benign masses and may, thus, provide substantial assistance as an additional parameter in the diagnosis of malignant o varian tumors in postmenopausal patients. (C) 1997 World Federation fo r Ultrasound in Medicine & Biology.