title: Improvement of displacement estimation of breast tissue in ultrasound elastography using the monogenic signal.
abstract: BACKGROUND
  In breast ultrasound elastography, tissues displacements estimation is obtained through a technique that follows the evolution of tissues under stress. However, during the acquisition of B-mode images, tissue displacements are often contaminated with multiplicative noise caused by changes in the speckle pattern in the tissue. Thus, the application of monogenic signal technique on the B-mode image in order to estimate displacement tissue, result in a presence of amplified noise in the deformation tissue image, which severely obscures the useful information. In this paper, we propose a new method based on the monogenic features, that is to improve the old monogenic signal (OMS) technique by improving the filtering step, so that the use of an effective denoising technique is enough to ensure a good estimation of displacement tissue. Our proposed method is based on the use of a robust filtering technique combined with the monogenic model.
  
  
  METHODS
  Two models of phantom elasticity are used in our test validation sold by CIRS company. In-vivo testing was also performed on the sets of clinical B-mode images to 20 patients including malignant breast tumors. Shrinkage wavelets has been used to eliminate the noise according to the threshold, then a guided filter is introduced to completely filter the image, the monogenic model is used after excerpting the image feature and estimating analytically the displacement tissue.
  
  
  RESULTS
  Accurate and excellent displacement estimation for breast tissue was observed in proposed method results. By adapting our proposed approach to breast B-mode images, we have shown that it demonstrated a higher performance for displacement estimation; it gives better values in term of standard deviation, higher contrast to noise ratio, greater peak signal-to-noise ratio, excellent structural similarity and much faster speed than OMS and B-spline techniques. The results of the proposed model are encouraging, allowing quick and reliable estimations.
  
  
  CONCLUSIONS
  Although the proposed approach is used in ultrasound domains, it has never been used in the estimation of the breast tissue displacement. In this context, our proposed approach could be a powerful diagnostic tool to be used in breast displacement estimation in ultrasound elastography.
authors.affiliation: Laboratory of Biophysics and Medical Technologies, High Institute of Medical Technologies of Tunis, University of Tunis El Manar, 9th Dr. Zouhair Essafi Street, 1006, Tunis, Tunisia. slimi.taher@hotmail.com.
authors.forename: Taher
authors.initials: T
authors.lastname: Slimi
authors.affiliation: Department of Medical Imaging and Radiology, University Hospital Center of Monji Slim, 2046, Marsa, Tunisia.|Department of Biophysics, Faculty of Medicine of Tunis, University of Tunis El Manar, 1007, Rabta, Tunisia.
authors.forename: Ines Marzouk
authors.initials: IM
authors.lastname: Moussa
authors.affiliation: Laboratory of Biophysics and Medical Technologies, High Institute of Medical Technologies of Tunis, University of Tunis El Manar, 9th Dr. Zouhair Essafi Street, 1006, Tunis, Tunisia.|Department of Biophysics, Faculty of Medicine of Tunis, University of Tunis El Manar, 1007, Rabta, Tunisia.|Department of National Radiation Protection Center, Bab Sadoun Children's Hospital, 1006, Tunis, Tunisia.
authors.forename: Tarek
authors.initials: T
authors.lastname: Kraiem
authors.affiliation: Laboratory of Biophysics and Medical Technologies, High Institute of Medical Technologies of Tunis, University of Tunis El Manar, 9th Dr. Zouhair Essafi Street, 1006, Tunis, Tunisia.
authors.forename: Halima
authors.initials: H
authors.lastname: Mahjoubi
mesh_terms: D000465:Algorithms; D001940:Breast / Q000503:physiopathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D055119:Elastic Modulus / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008327:Mammography / Q000295:instrumentation / Q000379:methods*; D009038:Motion; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical
keywords: Breast static elastography; Displacement estimation; Monogenic signal; Shrinkage wavelets