Ultrasound computed tomography his paper designs and implements a high throughout, extensible and flexible ultrasound excitation and data acquisition system that transmits sustained high-speed ultrasound data to the server by Ethernet technology. The system is mainly used for the second-generation ultrasound computed tomography system designed in the medical ultrasound lab, but can also be utilized by other types of ultrasound imaging systems. The system consists of one or more ultrasonic excitation and acquisition boards. Each board includes multiplexing switches, pulse generators with T/R switches, analog front ends, analog-to-digital converters, and an FPGA, and can be used to excite a 256-element probe to transmit and receive ultrasound signals. The peak and the average bandwidth of one single board are 44.8Gbps and 4Gbps, respectively. Potential users can combine several excitation and acquisition boards to build high-end ultrasound imaging systems. The system has been applied to upgrade our ultrasound computed tomography system.
Breast ultrasound tomography imaging (BUTI) is a new ultrasound imaging technique developed in recent years. In contrast to traditional ultrasound, BUTI uses a ring transducer to surround an object in a water tank and transmits the ultrasound echo from each element sequentially while receiving all the reflective and transmission signals from all elements. The tomography image is reconstructed using a similar reconstruction technique like x-ray computed tomography (X-CT) but much complicate due to the echo travelled along the curve instead of straight line like X ray. In this paper, with the objective of developing a breast ultrasound screening product, in vitro- and in vivo evaluation experiments were performed before proceeding to formal clinic trials. For the in vitro evaluation, a Breast Ultrasound Needle Biopsy Phantom from Supertech, IN, USA, was scanned by BUTIS (Breast ultrasound tomography imaging system) developed in HUST (Huazhong University of Science and Technology, Wuhan, China), MRI and traditional ultrasound scanner. Their image qualities were compared. In addition, the spatial resolution was estimated by using a nylon wire phantom. The results demonstrated that the spatial resolution of BUTIS is over 180 μm, which is almost 1 order higher than the traditional ultrasounds with the same frequency transducer. The in vivo evaluation was composed of a human arm and leg, the breast of a pregnant goat as well as human breasts from a female volunteer. The experimental results demonstrated that BUTIS can not only obtain exceptionally high contrast and high resolution images of soft tissue like the breast in vivo both for animal or human volunteer, but it can also be used to scan the subject with bones inside such as human arms and legs, which seems impossible for traditional ultrasounds. It illustrated that BUTIS will become a new efficient ultrasound imaging technique with wide potential applications in clinics.
In recent years, many research studies have been carried out on ultrasound computed tomography (USCT) for its application prospect in early detection of breast cancer. The synthetic aperture focusing technique (SAFT) widely used for the USCT image reconstruction is highly compute-intensive. Speeding up and optimizing the reconstruction algorithm on the graphics processing units (GPUs) have been highly applied to medical ultrasound imaging field. In this paper, we focus on accelerating the processing speed of SAFT with the GPU, considering its high parallel computation ability. The main computational features of SAFT are discussed to show the degree of computation parallelism. On the basis of the compute unified device architecture (CUDA) programming model and the Single Instruction Multiple Threads (SIMT) model, the optimization of SAFT parallel computation is performed. The proposed method was verified with the radio-frequency (RF) data of the breast phantom and the pig heart in vitro captured by the USCT system developed in the Medical Ultrasound Laboratory. Experimental results show that a 1024×1024 image reconstruction with a single NVIDIA GTX-1050 GPU could be 25 times faster than that with a 3.20-GHz Intel Core-i5 processor without image quality loss. The results also imply that with the increase of the image pixels, the acceleration effect is more notable.
In recent years, many research studies have been carried out on ultrasound computed tomography (USCT) for improving
the detection and management of breast cancer. This paper investigates a signal pre-processing method based on
frequency-shift low-pass filtering (FSLF) and least mean square adaptive filtering (LMSAF) for USCT image quality
enhancement (proposed in our previous work). FSLF is designed base on Zoom Fast Fourier Transform algorithm (ZFFT)
for processing the ultrasound signals in the frequency domain, while LMSAPF is based on the least mean square (LMS)
algorithm in the time domain. Through the combination of the two filters, the ultrasound image is expected to have less
noises and artifacts, and higher resolution and contrast. The proposed method was verified with the radio-frequency (RF)
data of the nylon threads and the breast phantom captured by the USCT system developed in the Medical Ultrasound
Laboratory. Experimental results show that the reconstructed images of nylon threads by the proposed method had
narrower main lobe width and lower side lobe level comparing to the delay-and-sum (DAS). The background noises and
artifacts could also be efficiently restrained. The reconstructed image of breast phantom by the proposed method had a
higher resolution and the contrast ratio (CR) could be enhanced for about 12dB to 18dB at different region of interest
(ROI).
KEYWORDS: Image filtering, Linear filtering, Ultrasonography, Digital filtering, Image enhancement, Signal processing, Image resolution, Data acquisition, Image quality, Chromium
Ultrasound image quality enhancement is a problem of considerable interest in medical imaging modality and an ongoing challenge to date. This paper investigates a method based on frequency-shift low-pass filtering (FSLF) and least mean square adaptive filtering (LMSAF) for ultrasound image quality enhancement. FSLF is used for processing the ultrasound signal in the frequency domain, while LMSAPF in the time domain. Firstly, FSLF shifts the center frequency of the focused signal to zero. Then the real and imaginary part of the complex data are filtered respectively by finite impulse response (FIR) low-pass filter. Thus the information around the center frequency are retained while the undesired ones, especially background noises are filtered. Secondly, LMSAF multiplies the signals with an automatically adjusted weight vector to further eliminate the noises and artifacts. Through the combination of the two filters, the ultrasound image is expected to have less noises and artifacts and higher resolution, and contrast. The proposed method was verified with the RF data of the CIRS phantom 055A captured by SonixTouch DAQ system. Experimental results show that the background noises and artifacts can be efficiently restrained, the wire object has a higher resolution and the contrast ratio (CR) can be enhanced for about 12dB to 15dB at different image depth comparing to delay-and-sum (DAS).
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