A modified synthetic aperture focusing technique using beam characteristics of transducer for ultrasound image improvement

The synthetic aperture focusing technique (SAFT) has been proposed to improve the lateral resolution of ultrasound image outside the focal region of the transducer. Yet, SAFT would result in an unexpected artifact image at the region near the focal point of the transducer due to the use of a virtue source concept associated with limited numbers of scan lines. To further improve this issue, the present study incorporated the transducer’s depth-dependency beam characteristics into SAFT-based imaging procedure. The imaging process was implemented on a graphic processing unit (GPU) platform for improving the computational efficiency. Ultrasound images were acquired from a commercial phantom with various contrast regions using a 3.5 MHz single element transducer. The -20dB beam width of transducer as a function of axial depth were measured for better estimating the time delay of each scanning point. Two scanning intervals, 50 and 200 μm, were acquired for B-mode imaging. Subsequently, the linear interpolation was performed for correcting the error associated with the time delay estimator for the image at the focus region. Results demonstrated that SAFT-based images implemented with virtual source correction corresponding to scanning intervals of 50 and 200 μm both displayed darker regions near the depth of 23 mm. The SAFT-based images modified with the correction of -20dB beam width of the transducer may not only improve the artifact region but also better restore the shape and contrast regions in the deeper regions of phantom. In additional, the computational efficiency is verified able to be greatly improved by the implementation with GPU platform. These results verify that current modified SAFT-based imaging may greatly enhance ultrasound image quality.