Purpose: Magnetic particle imaging (MPI) allows for imaging of the spatial distribution of magnetic nanoparticles (MNPs) in positive contrast, with high sensitivity, high spatial resolution, and high imaging speed. It...Purpose: Magnetic particle imaging (MPI) allows for imaging of the spatial distribution of magnetic nanoparticles (MNPs) in positive contrast, with high sensitivity, high spatial resolution, and high imaging speed. It is necessary to increase the signal-to-noise ratio to enhance the reliability of MPI. The purpose of this study was to investigate the effect of signal filtering on the image quality and quantitativity in projection-based MPI using phantoms. Materials and Methods: We fabricated two kinds of phantom (cylindrical tube phantom with a diameter of 6 mm and A-shaped phantom) and evaluated the effect of signal filtering in terms of root-mean-square (RMS) granularity and the correlation coefficient between iron concentrations of MNPs and average MPI values for four filter modes (THRU, BPF, BEF, and LPF). In the THRU mode, the signal input was output without passing through the filter. In the BPF mode, only the third-harmonic signal was passed using a band-pass filter (central frequency: 1200 Hz, band width: 1/3 octave). In the BEF mode, the first-harmonic signal was eliminated using a band-elimination filter (central frequency: 400 Hz, band width: 1/3 octave). In the LPF mode, only the signal with a frequency less than the third-harmonic frequency was passed using a low-pass filter (cut-off frequency: 1200 Hz, -24 ± 2 dB/octave). The RMS granularity was obtained by calculating standard deviations of the pixel values in the MPI image without MNPs, whereas average MPI values were obtained by drawing a circular region of interest with a diameter of 6 mm on the MPI image of the cylindrical tube phantom. Results: When using the filtered back-projection (FBP) method with a ramp filter for image reconstruction, the RMS granularity and correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF. In the BPF mode, however, some artifacts were observed. When using the maximum likelihood-expectation maximization (ML-EM) algorithm with an iteration number of 15, the correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF, whereas the RMS granularity did not largely depend on the filter mode and was significantly (p Conclusion: The BEF mode is adequate for the FBP method in projection-based MPI, whereas THRU is a best option in use of the ML-EM algorithm.展开更多
中值滤波算法是一种常见的图像去噪算法,其性能受滤波器窗口大小的影响较大,因此提出一种能够根据噪声点自动调节滤波窗口大小的改进中值滤波算法,可以有效克服中值滤波不能调整窗口大小的缺点,避免图像边缘模糊。通过利用Matlab进行仿...中值滤波算法是一种常见的图像去噪算法,其性能受滤波器窗口大小的影响较大,因此提出一种能够根据噪声点自动调节滤波窗口大小的改进中值滤波算法,可以有效克服中值滤波不能调整窗口大小的缺点,避免图像边缘模糊。通过利用Matlab进行仿真实验,将所提算法与中值滤波和维纳滤波算法进行对比,并计算峰值信噪比(Peak Signal to Noise Ratio,PSNR)来分析去噪结果。实验表明,与中值滤波和维纳滤波相比,改进中值滤波算法能够更加快速准确地去除图像中的噪声。因此,该改进中值滤波算法是一种有效的图像去噪算法。展开更多
This paper is a systematic study of the properties of infinite-length roots of median filters. We have succeeded in characterizing all the roots of median filters, especially roots of the second category. Special emph...This paper is a systematic study of the properties of infinite-length roots of median filters. We have succeeded in characterizing all the roots of median filters, especially roots of the second category. Special emphasis is placed on the structure of infinite-length roots of the second category.展开更多
视频图像处理系统从最早期的以模拟系统为主逐步向数字化转变,而目前常用的用数字信号处理专用芯片(digital signal processor,DSP)做处理器的数字视频图像处理系统在高速信号实时处理中难以达到要求,系统可靠性低;相对而言,FPGA用于实...视频图像处理系统从最早期的以模拟系统为主逐步向数字化转变,而目前常用的用数字信号处理专用芯片(digital signal processor,DSP)做处理器的数字视频图像处理系统在高速信号实时处理中难以达到要求,系统可靠性低;相对而言,FPGA用于实时图像处理,在速度上具有很大的优势,其内部自身结构易于实现分布式的算法结构,使得各功能块可以同时工作,更有利于高速数字信号处理。FPGA(现场可编程门阵列)设计技术将尽可能大而完整的电路系统在单一SOPC(片上可编程系统)中实现,从而使得所设计的电路在规模、可靠性、开发成本、产品维护和硬件升级等多方面实现最优化。展开更多
文摘Purpose: Magnetic particle imaging (MPI) allows for imaging of the spatial distribution of magnetic nanoparticles (MNPs) in positive contrast, with high sensitivity, high spatial resolution, and high imaging speed. It is necessary to increase the signal-to-noise ratio to enhance the reliability of MPI. The purpose of this study was to investigate the effect of signal filtering on the image quality and quantitativity in projection-based MPI using phantoms. Materials and Methods: We fabricated two kinds of phantom (cylindrical tube phantom with a diameter of 6 mm and A-shaped phantom) and evaluated the effect of signal filtering in terms of root-mean-square (RMS) granularity and the correlation coefficient between iron concentrations of MNPs and average MPI values for four filter modes (THRU, BPF, BEF, and LPF). In the THRU mode, the signal input was output without passing through the filter. In the BPF mode, only the third-harmonic signal was passed using a band-pass filter (central frequency: 1200 Hz, band width: 1/3 octave). In the BEF mode, the first-harmonic signal was eliminated using a band-elimination filter (central frequency: 400 Hz, band width: 1/3 octave). In the LPF mode, only the signal with a frequency less than the third-harmonic frequency was passed using a low-pass filter (cut-off frequency: 1200 Hz, -24 ± 2 dB/octave). The RMS granularity was obtained by calculating standard deviations of the pixel values in the MPI image without MNPs, whereas average MPI values were obtained by drawing a circular region of interest with a diameter of 6 mm on the MPI image of the cylindrical tube phantom. Results: When using the filtered back-projection (FBP) method with a ramp filter for image reconstruction, the RMS granularity and correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF. In the BPF mode, however, some artifacts were observed. When using the maximum likelihood-expectation maximization (ML-EM) algorithm with an iteration number of 15, the correlation coefficient decreased in the order of THRU, BPF, BEF, and LPF, whereas the RMS granularity did not largely depend on the filter mode and was significantly (p Conclusion: The BEF mode is adequate for the FBP method in projection-based MPI, whereas THRU is a best option in use of the ML-EM algorithm.
文摘中值滤波算法是一种常见的图像去噪算法,其性能受滤波器窗口大小的影响较大,因此提出一种能够根据噪声点自动调节滤波窗口大小的改进中值滤波算法,可以有效克服中值滤波不能调整窗口大小的缺点,避免图像边缘模糊。通过利用Matlab进行仿真实验,将所提算法与中值滤波和维纳滤波算法进行对比,并计算峰值信噪比(Peak Signal to Noise Ratio,PSNR)来分析去噪结果。实验表明,与中值滤波和维纳滤波相比,改进中值滤波算法能够更加快速准确地去除图像中的噪声。因此,该改进中值滤波算法是一种有效的图像去噪算法。
基金Project supported by the National Natural Science Foundation of China
文摘This paper is a systematic study of the properties of infinite-length roots of median filters. We have succeeded in characterizing all the roots of median filters, especially roots of the second category. Special emphasis is placed on the structure of infinite-length roots of the second category.
文摘视频图像处理系统从最早期的以模拟系统为主逐步向数字化转变,而目前常用的用数字信号处理专用芯片(digital signal processor,DSP)做处理器的数字视频图像处理系统在高速信号实时处理中难以达到要求,系统可靠性低;相对而言,FPGA用于实时图像处理,在速度上具有很大的优势,其内部自身结构易于实现分布式的算法结构,使得各功能块可以同时工作,更有利于高速数字信号处理。FPGA(现场可编程门阵列)设计技术将尽可能大而完整的电路系统在单一SOPC(片上可编程系统)中实现,从而使得所设计的电路在规模、可靠性、开发成本、产品维护和硬件升级等多方面实现最优化。
