High range resolution ultrasonographic vascular imaging using frequency domain interferometry with the capon method

For high range resolution ultrasonographic vascular imaging, we apply frequency domain interferometry with the Capon method to a single frame of in-phase and quadrature (IQ) data acquired using a commercial ultrasonographic device with a 7.5 MHz linear array probe. In order to tailor the adaptive beamforming algorithm for ultrasonography we employ four techniques: frequency averaging, whitening, radio-frequency data oversampling, and the moving average. The proposed method had a range resolution of 0.05 mm in an ideal condition, and experimentally detected the boundary couple 0.17 mm apart, where the boundary couple was indistinguishable from a single boundary utilizing a B-mode image. Further, this algorithm could depict a swine femoral artery with a range beam width of 0.054 mm and an estimation error for the vessel wall thickness of 0.009 mm, whereas using a conventional method the range beam width and estimation error were 0.182 and 0.021 mm, respectively. The proposed method requires 7.7 s on a mobile PC with a single CPU for a 1\times 3~{\hbox {cm}} region of interest. These findings indicate the potential of the proposed method for the improvement of range resolution in ultrasonography without deterioration in temporal resolution, resulting in enhanced detection of vessel stenosis.