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1.
Ultrason Imaging ; 45(4): 187-205, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37231671

RESUMO

Accurately estimating all strain components in quasi-static ultrasound elastography is crucial for the full analysis of biological media. In this study, 2D strain tensor imaging was investigated, focusing on the use of a regularization method to improve strain images. This method enforces the tissue property of (quasi-) incompressibility, while penalizing strong field variations, to smooth the displacement fields and reduce the noise in the strain components. The performance of the method was assessed with numerical simulations, phantoms, and in vivo breast tissues. For all the media examined, the results showed a significant improvement in both lateral displacement and strain, while axial fields were only slightly modified by the regularization. The introduction of penalty terms allowed us to obtain shear strain and rotation elastograms where the patterns around the inclusions/lesions were clearly visible. In phantom cases, the findings were consistent with the results obtained from the modeling of the experiments. Finally, the easier detectability of the inclusions/lesions in the final lateral strain images was associated with higher elastographic contrast-to-noise ratios (CNRs), with values in the range of [0.54-9.57] versus [0.08-0.38] before regularization.


Assuntos
Técnicas de Imagem por Elasticidade , Técnicas de Imagem por Elasticidade/métodos , Algoritmos , Imagens de Fantasmas
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2021: 2847-2851, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34891841

RESUMO

Accurately estimating all strain components in quasi-static ultrasound elastography is crucial for the full analysis of biological media. In this paper, 2D strain tensor imaging is investigated, using a partial differential equation (PDE)-based regularization method. More specifically, this method employs the tissue property of incompressibility to smooth the displacement fields and reduce the noise in the strain components. The performance of the method is assessed with phantoms and in vivo breast tissues. For all the media examined, the results showed a significant improvement in both lateral displacement and strain but also, to a lesser extent, in the shear strain. Moreover, axial displacement and strain were only slightly modified by the regularization, as expected. Finally, the easier detectability of the inclusion/lesion in the final lateral strain images is associated with higher elastographic contrast-to-noise ratios (CNRs), with values in the range [0.68 - 9.40] vs [0.09 - 0.38] before regularization.


Assuntos
Técnicas de Imagem por Elasticidade , Algoritmos , Imagens de Fantasmas
3.
Ultrasound Med Biol ; 43(12): 2904-2913, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29031983

RESUMO

Ultrasound applications such as elastography can benefit from 3-D data acquisition and processing. In this article, we describe a specific ultrasound probe, designed to acquire series of three adjacent imaging planes over time. This data acquisition makes it possible to consider the out-of-plane motion that can occur at the central plane during medium scanning, and is proposed with the aim of improving the results of strain imaging. In this first study, experiments were conducted on phantoms, and controlled axial and elevational displacements were applied to the probe using a motorized system. Radiofrequency ultrasound data were acquired at a 40-MHz sampling frequency with an Ultrasonix ultrasound scanner, and processed using a 3-D motion estimation method. For each of the 2-D regions of interest of the central plane in pre-compression data, a 3-D search was run to determine its corresponding version in post-compression data, with this search taking into account the region-of-interest deformation model chosen. The results obtained with the proposed ultrasound data acquisition and strain estimation were compared with results from a classic approach and illustrate the improvement produced by considering the medium's local displacements in elevation, with notably an increase in the mean correlation coefficients achieved.


Assuntos
Imageamento Tridimensional/métodos , Ultrassonografia/instrumentação , Ultrassonografia/métodos , Movimento (Física) , Imagens de Fantasmas , Estresse Mecânico
4.
Ultrasound Med Biol ; 40(2): 300-12, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24315397

RESUMO

The objective of this study was to assess the in vivo performance of our 2-D locally regularized strain estimation method with 35 breast lesions, mainly cysts, fibroadenomas and carcinomas. The specific 2-D deformation model used, as well as the method's adaptability, led to an algorithm that is able to track tissue motion from radiofrequency ultrasound images acquired in clinical conditions. Particular attention was paid to strain estimation reliability, implying analysis of the mean normalized correlation coefficient maps. For all lesions examined, the results indicated that strain image interpretation, as well as its comparison with B-mode data, should take into account the information provided by the mean normalized correlation coefficient map. Different trends were observed in the tissue response to compression. In particular, carcinomas appeared larger in strain images than in B-mode images, resulting in a mean strain/B-mode lesion area ratio of 2.59 ± 1.36. In comparison, the same ratio was assessed as 1.04 ± 0.26 for fibroadenomas. These results are in agreement with those of previous studies, and confirm the interest of a more thorough consideration of size difference as one parameter discriminating between malignant and benign lesions.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/fisiopatologia , Técnicas de Imagem por Elasticidade/métodos , Interpretação de Imagem Assistida por Computador/métodos , Modelos Biológicos , Palpação/métodos , Ultrassonografia Mamária/métodos , Adulto , Força Compressiva , Simulação por Computador , Módulo de Elasticidade , Feminino , Dureza , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estresse Mecânico , Resistência à Tração
5.
Ultrasound Med Biol ; 29(7): 1007-15, 2003 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12878247

RESUMO

An imaging system was developed for prostate elastography in vivo using a transrectal ultrasound (US) probe to guide high-intensity focused US (HIFU) therapy of prostate cancer. Uniform compression was applied using a balloon, while a sector image was acquired. Strain was calculated from the gradient of the displacements obtained from the ultrasonic signal using the cross-correlation technique. Elastograms were acquired on a total of 31 patients undergoing HIFU therapy for localised prostate cancer. For two patients, only part of the prostate was treated and posttherapy magnetic resonance imaging (MRI) confirmed the size and position of the HIFU lesions seen in the elastograms as low strain areas, with a strain contrast ratio between 1.6 and 3.2. The whole prostate was treated for the next 29 patients. After treatment, the whole prostate appeared to be stiff in the elastograms and a 40% to 60% (mean 50%) decrease in average strain was observed when compared to strains measured before HIFU application. Tumours identified by biopsies and sonograms could occasionally be seen in the preoperative elastograms. Decorrelation effects occurred mainly because of low sonographic signal-to-noise ratio (SNR) and of out-of-plane motion induced by respiration.


Assuntos
Adenocarcinoma/terapia , Próstata/diagnóstico por imagem , Neoplasias da Próstata/terapia , Terapia por Ultrassom/métodos , Adenocarcinoma/diagnóstico por imagem , Adenocarcinoma/fisiopatologia , Elasticidade , Humanos , Imageamento por Ressonância Magnética , Masculino , Próstata/fisiopatologia , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/fisiopatologia , Processamento de Sinais Assistido por Computador , Ultrassonografia
6.
Physiol Meas ; 23(2): 313-24, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-12051303

RESUMO

Our objective is to evaluate the external and internal dimensions of bone diaphysis and the speed of sound in cortical bone and in medullar marrow. The diaphysis is modelled by a cylindrical hollow tube. The theory of rays is used and an approximation allows us to break free from the data gained by ultrasonic field amplitude. Then, acoustical and dimensional parameters are only related to the time of flight of reflected and transmitted acoustic echoes in the tube. From the arrival time of particular echoes, the inverse problem resolution then allows us to experimentally determine the sought parameters. This method is validated in vitro on a bovine femur and gives satisfactory results.


Assuntos
Diáfises/diagnóstico por imagem , Fêmur/diagnóstico por imagem , Modelos Biológicos , Ultrassonografia/métodos , Acústica , Animais , Medula Óssea/diagnóstico por imagem , Bovinos
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