Ultrasonic imaging

An ultrasonic transducer can be made to produce a pulse which will propagate in a straight line into the sodium. If it encounters an inter ce with a region in which the speed of sound is different - a solid object, for example - it will be reflected. If the interface is flat and smooth and normal to the direction of propagation it will be reflected back to the transducer, which can be arranged to detect it. The time interval between transmission and reception can be measured and, if the speed of sound in sodium is known, the distance from the transducer to the object can be deduced. 

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A novel approach for suppression of material noise in ultrasonic signals, based on noncoherent detector statistics and signal entropy, has been presented. Experimental evaluation of the technique, using ultrasonic images from samples with coarse material structure, has proven its high performance. 

Hopgood, F.F., N. Woodcock, N.J. HaUam, and P.D. Picton, Interpreting ultrasonic images using rules, algorithms and neural networks , European Journal of NDT, Vol. 2, No. 4, April 1993, pp. 135-149. 

CHAUVEAU (D.), Introduction to the ultrasonic imaging, Soudage et techniques connexes, 1993, 47,11. 

DRAI (R.), BENTALEB (N.), ABDAT (F.), SELLIDJ (F), Application of real time ultrasonic imaging method for control of materials, Atmales de Chimie - Sciences des materiaux. Vol.22, 143, 1997. 

Segmentation method based on the analysis by Co-Occurrence Matrix is developed. We try to increase the quality of the obtained results by means of the application of two dimensional (2D) processing. We use Co-Occurrence Matrix for ultrasonic image segmentation. This tool, introduced by Haralick (1), was selected for the present study as several general considerations were favourable ... 

Automatic Methods with the help of appropriate algorithms permit the calculation of the threshold to segment ultrasonic images. It is this work, this method has been adopted. 

For our ultrasonic images, pixels belonging to the vertical axis ate separated by the displacement px of the translator, while on the horizontal axis, pixels are separated by a period of sampling. 

The ultrasonic images that we want to process are HF- type, (i.e., huilt from High Frequency signals. Fig. 4). Consequently, the noise is situated in the eentral part of the matrix. In order that we define two thresholds tl and t2. These last will be determined by using one of some measures quoted in the bibliography. 

The weld depths penetration for gold-nickel alloy and tantalum cylinders have been well controlled by an entirely contactless ultrasound method. Nevertheless, the development of signal and image processing will allow to increase the resolution of the ultrasonic images. Moreover, in order to be able to size quite well the lacks of weld penetration, the simulation of the interaction beam-defect is presently developed in our laboratory. 

Papoulis, A. and Chamzas, C., Improvement of range resolution by spectral extrapolation. Ultrasonic Imaging /, pp. 121-135 (1979)... 

It is to be taken into account that there is a difference between ultrasonic and radiography defect imaging, so the ultrasonic image recognition knowledge required for the person interpreting the inspection results. The ISONIC postprocessing mode allows to ease sueh interpretation because it s maximally approached to inspection standards. 

Hillger, W. Ultrasonic Imaging of Defects in CFRP-Laminates, Acustical Imaging, Proceedings of the IP International Symposium, Volume 19, pp. 575 - 579, Plenum Press, New York and London. 

For ultrasonic imaging systems (B-, C- and C-scans) single-shot measurements, fast data recordings, and fast data transfer must be performed. 

The external trigger input allows automatic inspections and ultrasonic imaging. The clock signal of an encoder or of stepper motors can be used as a trigger for the pulser. An internal software controlled divider allows different scan resolutions. 

The software US-SCAN 3.0 (IBT GmbH, Ober-Ramstadt, Germany) provides all functions of a portable flaw detector and a powerful ultrasonic imaging in A-, B-, C- and D-scans. Not only motor driven scanners can he used, but also manual scanning systems with encoders. Further documentation and test reports can be carried out with Windows software. 

Hillger, W. Ultrasonic imaging of defects in Sandwich Composites -from laboratory reseach to in-field inspections, 7 " ECNDT 1998, Copenhagen, Conf. Proc. 

C.E. Springer, Ultrasonic Imaging of Cylindrical Explosive Loads , NWL TR2737... 

J. Ophir, I. Cespedes, H. Ponnekanti, Y. Yazdi and X. Li, Elastography a quantitative method for imaging the elasticity of biological tissues, Ultrason. Imaging, 1991, 13, 111-134. 

I. Cespedes and J. Ophir, Reduction of image noise in elastography, Ultrason. Imaging, 1993, 15, 89-102. 

S. Y. Emelianov, M. A. Lubinski, A. R. Skovoroda, R. Q. Erkamp, S. F. Leavey, R. C. Wiggins and M. O Donnell, Reconstructive ultrasound elasticity imaging for renal transplant diagnosis kidney ex vivo results, Ultrason. Imaging, 2000, 22, 178-194. 

L. S. Wilson and D. E. Robinson, Ultrasonic measurement of small displacements and deformations of tissue, Ultrason. Imaging, 1982, 4, 71-82. 

L. Sandrin, S. Catheline, M. Tanter, X. Hennequin and M. Fink, Time-resolved pulsed elastography with ultrafast ultrasonic imaging, Ultrason. Imaging, 1999, 21, 259-272. 

Medicine Ultrasonic imaging (2 -10 MHz) is used, particularly in obstetrics, for observing the foetus and for guiding subcutaneous surgical implements. In physiotherapy lower frequencies (20-50 kHz) are used in the treatment of muscle strains, dissolution of blood clots and cancer treatment. 

As in the established imaging modalities, such as X-ray, computed tomography (CT), magnetic resonance imaging (MRI) and ultrasonic imaging (US), the... 

For other applications such as ultrasonic imaging, it is more important that the conversion of mechanical to electrical energy is high. 

Laser-induced ultrasonic imaging is used quite widely to study the interiors of opaque objects such as sculptures and paintings from the exploitation of laser-induced stress waves [8]. 

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