Conventional ultrasound imaging based on scan conversion suffers from blurring artifacts caused by interpolation. Especially, when zooming an image for enlarging lesions during scan conversion (i.e., read-zoom), this blurring artifact becomes severe. To reduce blurring artifacts, a write-zoom method was previously proposed. However, it still presents blurring artifacts and lowers the frame rate due to increased line density. In this paper, a new high definition zoom method based on compounded direct pixel beamforming (CDPB) capable enhancing the detail and boundary of lesions is presented. The performance of the proposed method was evaluated with phantom and <i>in vivo</i> experiments by measuring the information entropy contrast (IEC). The radio-frequency channel data were acquired by using a 3.5-MHz convex array transducer with the SonixTouch research platform (Ultrasonix Medical Corp., Vancouver, BC, Canada). The enlarged images using a new high-definition zoom method based on CDPB (i.e., HDZ-CDPB) with 128 transmit scanlines were reconstructed along with read- and write zoom (RZ and WZ) images based on scan conversion by using 128 and 256 transmit scanlines, respectively. From the phantom experiments, the IEC value with the proposed HDZCDPB method was enhanced by maximally 42% and 29% compared to the RZ and WZ methods, respectively. This preliminary results indicate that the proposed HDZ-CDPB method would be useful for generating a high definition ultrasound zoom image with improved image quality compared to the conventional scan conversion based methods (i.e., RZ and WZ) while achieving the high frame rate.
An ultrasound vector Doppler imaging is useful for detecting flow components normal to the ultrasound beam
direction. However, the conventional vector Doppler imaging method suffers from the bias of the time interval between
samples caused by the mismatch between transmit and receive directions during demodulation. In this paper, a new
directional demodulation method, in which demodulation is performed with a modified sample interval depending on the
receive beam steered angle to reduce the bias occurred in a conventional ultrasound vector Doppler imaging is presented.
To evaluate the performance of the proposed directional demodulation method, the pre-beamformed radio-frequency
(RF) data from in-vitro experiments were obtained using a commercial ultrasound system and a Doppler string phantom.
The true flow velocity of the phantom was 0.3 m/s. The center frequency of 5 MHz and the pulse repetition frequency of
4 kHz were used for the experiments. Also, a 32-element sub-aperture on a 128-element 7.2-MHz linear array probe
were used for emission and reception while changing the flow direction from -45 degrees to 0 degree by a step of 5
degrees. The proposed directional demodulation method successfully visualizes all flow directions. In addition, it lowers
a bias on flow estimation compared to the conventional method (i.e., 0.0255±0.0516 m/s vs. 0.0248±0.0469 m/s of error
of velocity, 2.4862±3.8911 degrees vs. 2.4857±3.5115 degrees of error of direction, respectively). These results indicate
that the proposed directional demodulation method can enhances the accuracy in flow estimation for vector Doppler