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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  [838 journals]
  • Computational Complexity Reduction of Synthetic-aperture Focus in
           Ultrasound Imaging Using Frequency-domain Reconstruction
    • Authors: Moghimirad, E; Mahloojifar, A, Mohammadzadeh Asl, B.
      Pages: 175 - 193
      Abstract: A new frequency-domain implementation of a synthetic aperture focusing technique is presented in the paper. The concept is based on synthetic aperture radar (SAR) and sonar that is a developed version of the convolution model in the frequency domain. Compared with conventional line-by-line imaging, synthetic aperture imaging has a better resolution and contrast at the cost of more computational load. To overcome this problem, point-by-point reconstruction methods have been replaced by block-processing algorithms in radar and sonar; however, these techniques are relatively unknown in medical imaging. In this paper, we extended one of these methods called wavenumber to medical ultrasound imaging using a simple model of synthetic aperture focus. The model, derived here for monostatic mode, can be generalized to multistatic as well. The method consists of 4 steps: a 2D fast Fourier transform of the data, frequency shift of the data to baseband, interpolation to convert polar coordinates to rectangular ones, and returning the data to the spatial-domain using a 2D inverse Fourier transform. We have also used chirp pulse excitation followed by matched filtering and spotlighting algorithm to compensate the effect of differences in parameters between radar and medical imaging. Computational complexities of the two methods, wavenumber and delay-and-sum (DAS), have been calculated. Field II simulated point data have been used to evaluate the results in terms of resolution and contrast. Evaluations with simulated data show that for typical phantoms, reconstruction by the wavenumber algorithm is almost 20 times faster than classical DAS while retaining the resolution.
      PubDate: 2016-04-13T04:27:56-07:00
      DOI: 10.1177/0161734615583461
      Issue No: Vol. 38, No. 3 (2016)
  • Improved Correlation of Strain Indices with Cognitive Dysfunction with
           Inclusion of Adventitial Layer with Carotid Plaque
    • Authors: Wang, X; Mitchell, C. C, Varghese, T, Jackson, D. C, Rocque, B. G, Hermann, B. P, Dempsey, R. J.
      Pages: 194 - 208
      Abstract: Plaque instability may lead to chronic embolization, which in turn may contribute to progressive cognitive decline. Accumulated strain tensor indices over a cardiac cycle within a pulsating carotid plaque may be viable biomarkers for the diagnosis of plaque instability. Using plaque-only carotid artery segmentations, we recently demonstrated that impaired cognitive function correlated significantly with maximum axial and lateral strain indices within a localized region of interest in plaque. Inclusion of the adventitial layer focuses our strain or instability measures on the vessel wall-plaque interface hypothesized to be a region with increased shearing forces and measureable instability. A hierarchical block-matching motion tracking algorithm developed in our laboratory was used to estimate accumulated axial, lateral, and shear strain distribution in plaques identified with the plaque-with-adventitia segmentation. Correlations of strain indices to the Repeatable Battery for the Assessment of Neuropsychological Status Total score were performed and compared with previous results. Overall, correlation coefficients (r) and significance (p) values improved for axial, lateral, and shear strain indices. Shear strain indices, however, demonstrated the largest improvement. The Pearson correlation coefficients for maximum shear strain and cognition improved from the previous plaque-only analyses of –0.432 and –0.345 to –0.795 and –0.717 with the plaque-with-adventitia segmentation for the symptomatic group and for all patients combined, respectively. Our results demonstrate the advantage of including adventitia for ultrasound carotid strain imaging providing improved association to parameters assessing cognitive impairment in patients. This supports theories of the importance of the vessel wall plaque interface in the pathophysiology of embolic disease.
      PubDate: 2016-04-13T04:27:56-07:00
      DOI: 10.1177/0161734615589252
      Issue No: Vol. 38, No. 3 (2016)
  • Breast-lesion Segmentation Combining B-Mode and Elastography Ultrasound
    • Authors: Pons, G; Marti, J, Marti, R, Ganau, S, Noble, J. A.
      Pages: 209 - 224
      Abstract: Breast ultrasound (BUS) imaging has become a crucial modality, especially for providing a complementary view when other modalities (i.e., mammography) are not conclusive in the task of assessing lesions. The specificity in cancer detection using BUS imaging is low. These false-positive findings often lead to an increase of unnecessary biopsies. In addition, increasing sensitivity is also challenging given that the presence of artifacts in the B-mode ultrasound (US) images can interfere with lesion detection. To deal with these problems and improve diagnosis accuracy, ultrasound elastography was introduced. This paper validates a novel lesion segmentation framework that takes intensity (B-mode) and strain information into account using a Markov Random Field (MRF) and a Maximum a Posteriori (MAP) approach, by applying it to clinical data. A total of 33 images from two different hospitals are used, composed of 14 cancerous and 19 benign lesions. Results show that combining both the B-mode and strain data in a unique framework improves segmentation results for cancerous lesions (Dice Similarity Coefficient of 0.49 using B-mode, while including strain data reaches 0.70), which are difficult images where the lesions appear with blurred and not well-defined boundaries.
      PubDate: 2016-04-13T04:27:56-07:00
      DOI: 10.1177/0161734615589287
      Issue No: Vol. 38, No. 3 (2016)
  • Doppler Tissue Evaluation of Atrial Conduction Properties in Patients With
           Non-alcoholic Fatty-liver Disease
    • Authors: Ozveren, O; Izgi, C, Eroglu, E, Simsek, M. A, Turer, A, Kucukdurmaz, Z, Cinar, V, Degertekin, M.
      Pages: 225 - 235
      Abstract: Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in clinical practice, and there is an increasing trend in its prevalence in the general population. Recent studies have demonstrated increased risk of atrial fibrillation (AF) in NAFLD. However, information on the mechanism of increased risk of AF in NAFLD is lacking. Impaired atrial conduction is an important factor in the pathophysiology of AF. We aimed to investigate atrial conduction properties in patients with NAFLD by tissue Doppler echocardiography. Fifty-nine ultrasound diagnosed NAFLD patients without clinical diagnosis of hypertension, diabetes mellitus, or cardiac disease and 22 normal subjects as controls were included in this study. Atrial conduction properties were assessed by electromechanical delay (EMD) derived from Doppler tissue echocardiography examination and P-wave dispersion (PWD) calculated from the 12-lead electrocardiogram. Inter-atrial and intra-atrial EMD intervals were significantly longer in NAFLD patients than in controls (inter-atrial EMD, 31.9 ± 8.5 ms vs. 23.4 ± 4.6 ms, p = 0.0001, and intra-atrial EMD, 14.3 ± 5.2 vs. 10.2 ± 4.0 ms, p = 0.001). Similarly, PWD was significantly higher in NAFLD patients compared with controls (49.2 ± 6.3 ms vs. 43.3 ± 4.2 ms, p = 0.0001). Maximum left atrial volume was also significantly higher in the NAFLD group than in controls (51 ± 11 mL vs. 34 ± 9 mL, p < 0.0001). This study demonstrated that atrial conduction is impaired in patients with NAFLD. Also, in a patient population of NAFLD without any clinical diagnosis of cardiac disease, diabetes, or hypertension, left atrial volume was increased compared with controls. These findings suggest impaired atrial conduction as a factor in increased risk of AF in NAFLD.
      PubDate: 2016-04-13T04:27:56-07:00
      DOI: 10.1177/0161734615595015
      Issue No: Vol. 38, No. 3 (2016)
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