Multiline Acquisition Beamforming for Ultrasound Computed Tomography

In recent years, ultrasound computed tomography (USCT) systems have been developed for early detection of breast cancer. In this paper, a multiline acquisition (MLA) beamforming method for USCT is proposed, and the steering angle of the receiving multiline for ring array is discussed. The principle of MLA beamforming is to produce several receiving lines from one transmitted event. It can provide images with less noise and artifacts, higher resolution and better contrast compared to the traditional B-mode imaging method. The validation of the MLA is described through the breast phantom experiment and in vivo experiments. The radio-frequency (RF) data were captured by the USCT system developed in the Medical Ultrasound Laboratory. The main components of the USCT system consist of a ring-type transducer, a multiplexer, a channel data acquisition system and a workstation. The ring-type transducer with 1024 elements has an inner diameter of 200 mm. The center frequency of the transducer is 2.5 MHz. Experimental results show that the reconstructed images by MLA method get the higher signal to noise ratio (SNR) and more homogeneous background compared to the delay and sum (DAS) method. For the breast phantom, MLA gives the better contrast properties for the hyperechoic cyst. Artifacts are removed more efficiently while the clutters are suppressed simultaneously. For in vivo experiments, the CR of the upper arm image increases from 3.18 dB to 24.23 dB, and the CR of the lower leg image increases from 19.19 dB to 45.17 dB in the regions of interest (ROI). The skeletal muscle, the bone of the upper arm and the lower leg can be distinguished more clearly. In the breast experiment, all the evaluation indices including CR, CNR, and SNR are improved at ROIs, and more details of the breast tissue can be shown.