An approach for acquiring 3D data using a modified transducer array was previously described. This array employs one “Imaging” array and two “Tracking” arrays placed perpendicular to the Imaging array. Any component of diagonal motion due to imperfect elevational scanning has the potential to cause dimensional error in the 3D reconstruction. In this paper, diagonal motion is determined by examining the ratio of cross-correlation values, between successive image frames, from both the Imaging array data sets and the Tracking array data sets. The elevational translation is computed using a speckle tracking method on the Tracking array data if there is more elevational motion than azimuthal motion. Similarly, the speckle tracking is performed on the Imaging array data if there is more azimuthal motion. The angle of motion and the translational component derived from one of the two orientations of arrays allows computation of the component of translation in the other direction. MATLAB simulations and experimental result illustrate that the error in speckle tracking was dependent on the angle of the diagonal motion, and that there were distinct rates of decorrelation from each array for different diagonal motions.
Conventional ultrasound Doppler velocity measurements are scaled by the cosine of the angle between the blood flow axis and ultrasound beam axis. In the approach used here, a transducer array was used to acquire a first cross-sectional Doppler data set of the vessel under examination. The transducer array was then moved to a different angle to acquire a second cross-sectional Doppler data set. Thereafter, we used the known angle between the two arrays ultrasound beams and the cosine (theta) scaled Doppler estimates to solve for the true angle between the blood flow axis and ultrasound beam axis of the first data set. Upon integrating the angle corrected velocity estimates over the entire vessel cross-section, we were able to estimate blood volume flow rate. The performance of the new approach was tested in a flow phantom that was designed to provide a constant flow in a simulated vessel. The data were collected for two sets of angles and three different flow velocities for each angle set. The unknown Doppler angle was calculated from the data and used to correct the flow velocity.
An approach for acquiring dimensionally accurate 3D ultrasound data, based on a modified 1D transducer array, is presented. Th method avoids many of the drawbacks of conventional approaches to 3D ultrasound data acquisition. Scanning is simple and easy to perform in a clinical setting. A modified 1D transducer array is employed comprising a central conventional 1D imaging array and two perpendicular tracking arrays - each integrally mounted at each end of the imaging array. As the transducer is scanned in the elevation direction of the central array, the images acquired by the tracking array remain coplanar and hence it is possible to accurately track image motion using any one of several image tracking techniques. Methods for improving the performance and ergonomics of the transducer array are presented. In particular, a crossed electrode transducer structure is proposed for minimizing the total transducer footprint (contact surface area). The versatility of the approach in terms of its suitability for scanning breast, carotid and prostate is discussed. We have acquired both phantom and in-vivo 3D ultrasound data with the prototype imaging approach. Initial studies suggest that the linear dimensional accuracy in the elevation direction (i.e., the reconstructed direction) is approximately 5%.