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Journal Cover Ultrasonic Imaging
  [SJR: 0.818]   [H-I: 34]   [1 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0161-7346 - ISSN (Online) 1096-0910
   Published by Sage Publications Homepage  [842 journals]
  • Combining the APES and Minimum-variance Beamformers for Adaptive
           Ultrasound Imaging
    • Authors: Mohammadzadeh Asl; B.
      Pages: 239 - 253
      Abstract: In recent years, adaptive minimum-variance (MV) beamforming has been successfully applied to medical ultrasound imaging, resulting in simultaneous improvement in imaging resolution and contrast. MV has high resolution and hence can provide accurate estimates of the target locations. However, the MV amplitude estimates are significantly biased downward, especially when occurring the errors in model parameters. The amplitude and phase estimation (APES) beamformer gives much more accurate amplitude estimates at the target locations, but at the cost of lower resolution. To reap the benefits of both MV and APES, we have proposed a modified APES (MAPES) beamformer by adding a parameter which controls the trade-off between spatial and amplitude resolutions. We have also proposed an adaptive beamformer which combines the MV and APES. The proposed beamformer first estimates the peak locations using the MV estimator and then refines the amplitude estimates at these locations using the MAPES estimator. By using simulated and experimental data—point targets as well as cyst phantoms—we show the efficacy of the proposed beamformers.
      PubDate: 2016-06-01T05:12:42-07:00
      DOI: 10.1177/0161734615600167
      Issue No: Vol. 38, No. 4 (2016)
       
  • Nonlocal Total-Variation-Based Speckle Filtering for Ultrasound Images
    • Authors: Wen, T; Gu, J, Li, L, Qin, W, Wang, L, Xie, Y.
      Pages: 254 - 275
      Abstract: Ultrasound is one of the most important medical imaging modalities for its real-time and portable imaging advantages. However, the contrast resolution and important details are degraded by the speckle in ultrasound images. Many speckle filtering methods have been developed, but they are suffered from several limitations, difficult to reach a balance between speckle reduction and edge preservation. In this paper, an adaptation of the nonlocal total variation (NLTV) filter is proposed for speckle reduction in ultrasound images. The speckle is modeled via a signal-dependent noise distribution for the log-compressed ultrasound images. Instead of the Euclidian distance, the statistical Pearson distance is introduced in this study for the similarity calculation between image patches via the Bayesian framework. And the Split-Bregman fast algorithm is used to solve the adapted NLTV despeckling functional. Experimental results on synthetic and clinical ultrasound images and comparisons with some classical and recent algorithms are used to demonstrate its improvements in both speckle noise reduction and tissue boundary preservation for ultrasound images.
      PubDate: 2016-06-01T05:12:42-07:00
      DOI: 10.1177/0161734615600676
      Issue No: Vol. 38, No. 4 (2016)
       
  • Handheld Thermoacoustic Scanning System Based on a Linear-array Transducer
    • Authors: Ji, Z; Ding, W, Ye, F, Lou, C.
      Pages: 276 - 284
      Abstract: To receive the information necessary for imaging, traditional microwave-induced thermoacoustic imaging systems (MITISs) use a type of circular-scanning mode using single or arc detectors. However, the use of MITISs for body scanning is complicated by restrictions in space and imaging time. A linear-array detector, the most widely used transducer in medical ultrasound imaging systems for body scanning, is a possible alternative to MITISs for scanning biological tissues, such as from the breast or limbs. In this paper, a handheld MITIS, based on a linear-array detector and a multiple data acquisition system, is described, and the capacity of the system is explored experimentally. First, the vertical and lateral resolution of the system is discussed. Next, real-time imaging of a moving object, obtained with an image capture rate of 20 frame/s, is described. Finally, a phantom experiment is detailed, investigating the overall imaging capability. The results show that this system achieves rapid scanning with a large field of view. The system has the obvious advantages of being handheld, not using coupled fluids, and achieving real-time imaging with a large field of view, which make this MITIS more suitable for clinical applications.
      PubDate: 2016-06-01T05:12:42-07:00
      DOI: 10.1177/0161734615601987
      Issue No: Vol. 38, No. 4 (2016)
       
  • Backscatter-difference Measurements of Cancellous Bone Using an Ultrasonic
           Imaging System
    • Authors: Hoffmeister, B. K; Smathers, M. R, Miller, C. J, McPherson, J. A, Thurston, C. R, Spinolo, P. L, Lee, S.-R.
      Pages: 285 - 297
      Abstract: Backscatter-difference measurements may be used to detect changes in bone caused by osteoporosis. The backscatter-difference technique measures the power difference between two portions of an ultrasonic backscatter signal. The goal of this study is to evaluate the feasibility of using an ultrasonic imaging system to perform backscatter-difference measurements of bone. Ultrasonic images and backscatter signals were acquired from 24 specimens of human cancellous bone. The signals were analyzed in the frequency domain to determine the normalized mean backscatter-difference (nMBD) and in the time domain to determine the normalized backscatter amplitude ratio (nBAR). The images were analyzed to determine the normalized pixel value difference (nPVD), which measures the difference in average pixel brightness between regions of interest placed at two different depths in the image. All three parameters were found to increase with bone mineral density. The signal-based parameters, nMBD and nBAR, correlated well with bone mineral density, yielding linear correlation coefficients that ranged from 0.74 to 0.87. The image based parameter, nPVD, performed somewhat less well, yielding correlation coefficients that ranged from 0.42 to 0.81. These results suggest that ultrasonic imaging systems may be used to perform backscatter-difference measurements for the purpose of ultrasonic bone assessment.
      PubDate: 2016-06-01T05:12:42-07:00
      DOI: 10.1177/0161734615603703
      Issue No: Vol. 38, No. 4 (2016)
       
 
 
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