Preliminary results from use of multifrequency ultrasound imaging for quantitative tissue characterization

The attenuation coefficient (AC) measures the loss of ultrasound (US) signal amplitude as it propagates at depth. In this research, we detail a pixel-based AC estimation method using a new multifrequency US imaging (MFUI) approach. A research scanner equipped with an L11-5v transducer was used in a plane wave imaging mode. Radiofrequency data at 24 different transmit frequencies that span the range of the transducer bandwidth were sequentially collected. Each acquisition involved 21 angled planes waves in the ±18° range. B-mode US images were generated by applying a Hilbert transformation applied to the angled compounded data followed by logarithmic scaling. Local ACs were estimated from the series of multifrequency US images based on knowledge of the relationship between US image intensity, transmit frequency, and depth at each spatial location. Preliminary MFUI tests were conducted using an US phantom having two different regions with ACs of 0.70 or 0.95 dB/cm/MHz. AC images were summarized as mean ± standard deviation. Average MFUI-derived ACs from the phantom material with known values of 0.70 and 0.95 dB/cm/MHz were estimated to be 0.70 ± 0.007 and 0.95 ± 0.002 dB/cm/MHz, respectively. AC estimates were within 0.04 dB/cm/MHz of the true value. Preliminary results indicate MFUI is a promising approach for local estimation of AC values.