For high range resolution acoustic vascular imaging we apply frequency domain interferometry and Capon method to a few frames of in-phase and quadrature (IQ) data acquired by a commercial ultrasonographic device. To suit the adaptive beamforming algorithm to medical acoustic imaging we employ three techniques; frequency averaging, whitening, and pseudo-double RF data conversion. The proposed method detected two couples of boundaries 0.26 and 0.19 mm apart using a single frame and two frames of IQ data, respectively, where each couple of boundaries is indistinguishable from a single boundary utilizing B-mode images. Further this algorithm could depict a swine femoral artery with higher range resolution than conventional B-mode imaging. These results indicate the potential of the proposed method for the range resolution improvement in ultrasonography, originating the progress in detection of vessel stenosis.