Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
1.
J Acoust Soc Am ; 132(3): 1249-52, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22978851

RESUMO

Ultrasound tomography (UST) is being developed to address the limitations of mammography in breast cancer detection. Central to the success of UST is the possibility of obtaining high-resolution images of tissue mechanical properties across the whole breast. A recent paper [Huthwaite and Simonetti, J. Acoust. Soc. Am. 130, 1721-1734 (2011)] made use of a numerical phantom to demonstrate that sufficient image resolution can be obtained by simply treating refraction and diffraction effects in consecutive steps through the combination of ray-based time of flight and diffraction tomography. This letter presents the first experimental demonstration of the method using phantom and invivo data from a cancer patient.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Mama/patologia , Interpretação de Imagem Assistida por Computador , Ultrassonografia Mamária , Algoritmos , Feminino , Análise de Fourier , Humanos , Imagens de Fantasmas , Valor Preditivo dos Testes , Ultrassonografia Mamária/instrumentação
2.
Med Phys ; 36(7): 2955-65, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19673194

RESUMO

Ultrasound is commonly used as an adjunct to mammography for diagnostic evaluation of suspicions arising from breast cancer screening. As an alternative to conventional sonography that uses hand-held transducers, toroidal array probes that encircle the breast immersed in a water bath have been investigated for ultrasound tomography. In this paper, two sets of experiments performed with a prototype ultrasound scanner on a phantom and a human breast in vivo are used to investigate the effects of diffraction and coherence in ultrasound tomography. Reconstructions obtained with transmission diffraction tomography (TDT) are compared with conventional reflection imaging and computerized ultrasound tomography showing a substantial improvement. The in vivo tests demonstrate that TDT can image the complex boundary of a cancer mass and suggest that it can reveal the anatomy of milk ducts and Cooper's ligaments.


Assuntos
Tomografia/métodos , Ultrassonografia Mamária/métodos , Algoritmos , Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/patologia , Feminino , Humanos , Imagens de Fantasmas , Ultrassonografia Mamária/instrumentação
3.
Phys Rev E Stat Nonlin Soft Matter Phys ; 76(3 Pt 2): 036601, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17930351

RESUMO

The classical diffraction limit excludes the possibility of resolving features of an object which are spaced less than half a wavelength apart when scattering experiments are performed from the far field. However, recently it has been shown that this limit could be a consequence of the Born approximation that neglects the distortion of the probing wave as it travels through the object to be imaged. Such a distortion, which is due to the multiple scattering phenomenon, can encode unlimited resolution in the radiating component of the scattered field thus leading to super resolution. In this context, a resolution better than lambda/3 has been reported in the case of elastic wave probing [F. Simonetti, Phys. Rev. E 73, 036619 (2006)], lambda being the wavelength of the wave illuminating the object. This paper demonstrates a resolution better than lambda/4 and approaching lambda/6 for objects immersed in a water bath probed by means of a ring transducer array that excites and detects ultrasonic pressure waves in a full view configuration. This is achieved despite the presence of a high level of noise in the measurements (the signal to noise ratio was below 0 dB). Moreover, while previous papers have provided experimental evidence of super resolution for objects small compared to the wavelength, here the case of extended objects is also investigated.

4.
Comput Med Imaging Graph ; 40: 170-81, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25456144

RESUMO

Ultrasound Computer Tomography (USCT) is a promising breast imaging modality under development. Comparison to a standard method like mammography is essential for further development. Due to significant differences in image dimensionality and compression state of the breast, correlating USCT images and X-ray mammograms is challenging. In this paper we present a 2D/3D registration method to improve the spatial correspondence and allow direct comparison of the images. It is based on biomechanical modeling of the breast and simulation of the mammographic compression. We investigate the effect of including patient-specific material parameters estimated automatically from USCT images. The method was systematically evaluated using numerical phantoms and in-vivo data. The average registration accuracy using the automated registration was 11.9mm. Based on the registered images a method for analysis of the diagnostic value of the USCT images was developed and initially applied to analyze sound speed and attenuation images based on X-ray mammograms as ground truth. Combining sound speed and attenuation allows differentiating lesions from surrounding tissue. Overlaying this information on mammograms, combines quantitative and morphological information for multimodal diagnosis.


Assuntos
Neoplasias da Mama/diagnóstico , Neoplasias da Mama/fisiopatologia , Imageamento Tridimensional/métodos , Imagem Multimodal/métodos , Ultrassonografia Mamária/métodos , Filme para Raios X , Algoritmos , Simulação por Computador , Feminino , Humanos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Modelos Biológicos , Reconhecimento Automatizado de Padrão/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Técnica de Subtração
5.
Phys Med Biol ; 60(14): 5381-98, 2015 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-26110909

RESUMO

Application of the frequency domain acoustic wave equation on data acquired from ultrasound tomography scans is shown to yield high resolution sound speed images on the order of the wavelength of the highest reconstructed frequency. Using a signal bandwidth of 0.4-1 MHz and an average sound speed of 1500 m s(-1), the resolution is approximately 1.5 mm. The quantitative sound speed values and morphology provided by these images have the potential to inform diagnosis and classification of breast disease. In this study, we present the formalism, practical application, and in vivo results of waveform tomography applied to breast data gathered by two different ultrasound tomography scanners that utilize ring transducers. The formalism includes a review of frequency domain modeling of the wave equation using finite difference operators as well as a review of the gradient descent method for the iterative reconstruction scheme. It is shown that the practical application of waveform tomography requires an accurate starting model, careful data processing, and a method to gradually incorporate higher frequency information into the sound speed reconstruction. Following these steps resulted in high resolution quantitative sound speed images of the breast. These images show marked improvement relative to commonly used ray tomography reconstruction methods. The robustness of the method is demonstrated by obtaining similar results from two different ultrasound tomography devices. We also compare our method to MRI to demonstrate concordant findings. The clinical data used in this work was obtained from a HIPAA compliant clinical study (IRB 040912M1F).


Assuntos
Algoritmos , Transdutores , Ultrassonografia Mamária/métodos , Ondas Ultrassônicas , Ultrassonografia Mamária/instrumentação
6.
Jugosl Ginekol Opstet ; 18(3-4): 269-77, 1978.
Artigo em Servo-Croata (Latino) | MEDLINE | ID: mdl-757243

RESUMO

The frequency of various presentations and positions of the fetus in individual gestational weeks in the third trimester was examined in 1137 pregnant women based on 1785 ultrasonic findings. Cephalic presentation at 28 weeks was observed in 62% cases and at the end of pregnancy in 95%. Breech presentation decreased from 29% to 4% before delivery, and transverse presentation was 10 times less frequent at delivery than at the beginning of the third trimester. The first and second fetal positions occurred almost equally in both of the main longitudinal presentations. Dynamics of changes regarding position and presentation was examined in 32 patients regularly each week. In 10 of them there was no presentation change and in 22, changes occurred once or several times, tending to attain a physiologic cephalic presentation before delivery. This presentation, once attained, did not change after the 33rd week. With regard to breech presentation, changes are possible even up to the 36th week. The optimal time for ultrasonic examination with the purpose of determining fetal presentation and position is 33-37 full gestational weeks.


Assuntos
Feto/fisiologia , Apresentação no Trabalho de Parto , Terceiro Trimestre da Gravidez , Feminino , Humanos , Movimento , Gravidez
7.
Jugosl Ginekol Opstet ; 23(5-6): 126-9, 1983.
Artigo em Servo-Croata (Latino) | MEDLINE | ID: mdl-6679001

RESUMO

From 1971 to 1975, when beta sympathicomimetics were not used, from total 13 561 deliveries 6.06% were preterm deliveries. In years 1976-1980, when these tocolytics are routinely used from total 15 242 deliveries 5.24% were preterm deliveries. Significance is statistically characteristic, p = = 0,01. In the anamnesis of all parturients in both periods, frequency of factors which effect on the rate of preterm deliveries is equal.


Assuntos
Trabalho de Parto Prematuro/prevenção & controle , Propanolaminas/uso terapêutico , Ritodrina/uso terapêutico , Feminino , Fenoterol/uso terapêutico , Humanos , Trabalho de Parto Prematuro/epidemiologia , Gravidez
8.
Med Arh ; 46(3-4): 71-2, 1992.
Artigo em Servo-Croata (Latino) | MEDLINE | ID: mdl-1364517

RESUMO

Respiratory diseases are in prevalence under the other diseases in industry of leather. The exposition to the chemical irritances like bensen and toluene is very important, because a short exposition gives early symptoms. We found in 54% of examined population pathologic ORL cases in a sense of hypertrophic and atrophic forms rhinitis and pharyngitis. Bacterial flora is pathologic in 20% of examined workers and comparing positive bacteriologic form between nose and pharynges we found infections of mucose of nose more frequent than the throat. The occupational atmosphere and its microclime is very important in pathology of upper respiratory diseases. It is etiological factor in morphological changes of the respiratory mucosas. At the end, we can say that the ordinary monitoring which contains monitoring of working place, and biologic monitoring which means ORL, bacteriological, biochemical and toxicologic examinations must be regulated.


Assuntos
Doenças Profissionais/etiologia , Doenças Respiratórias/etiologia , Curtume , Humanos , Doenças Profissionais/diagnóstico , Exposição Ocupacional , Doenças Respiratórias/diagnóstico
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA