Measuring and testing – Vibration – By mechanical waves
Patent
1995-01-12
1996-12-03
Williams, Hezron E.
Measuring and testing
Vibration
By mechanical waves
73625, 12866101, 367125, 367126, G01N 2900, A61B 800
Patent
active
055810365
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an array imaging system, and more particularly to an ultrasonic array imaging system in which ultrasonic echoes reflected from an object to be imaged and received by an array transducer are focused in a digital fashion by applying a bandwidth sampling technique. Such an ultrasonic system can be utilized in medical diagnosis, non-destruction inspection, underwater investigation, etc. Moreover, the present invention can be applied to imaging systems using any type of array transducers including linear, phased, convex, concave and annular arrays. The present invention can be applied not only to ultrasonic imaging systems but also to radar systems using array transducers for the beam forming purpose. The present invention can be applied to any imaging modelity in which the analytic signal can be effectively utilized, including B, C and M mode images, for flow measurement, phase aberration correction, tissue characterization, etc.
2. Description of the Related Art
Generally, in an ultrasonic imaging system, an ultrasonic pulse signal is transmitted toward an object to be imaged, reflected from a surface of an acoustic impedance discontinuity of the object, and received by an array transducer. The received signals are then converted into electric signals which are displayed on a video monitor after various processing. The resulting image conveys some information of the characteristics of the object being examined. In this case, the use of a short pulse increases the signal resolution and the use of an array obtains focusing capability to improve lateral resolution. In the past, various methods have been used to improve the resolution, in particular, the lateral resolution.
FIG. 1 is a schematic block diagram of a conventional ultrasonic imaging system. An ultrasonic pulse signal generated from a pulse generator 11 is supplied to an array transducer 10 via switch 12. The array transducer 10 converts an electric pulse signal into an ultrasonic signal and provides the converted signal to an object 13 to be imaged. Then, the ultrasonic signal is reflected from an acoustic impedance discontinuous surface of the object 13 and the reflected signal is again received by the array transducer 10. At this time, in a case where there are a plurality of acoustic impedance discontinuous surfaces, the ultrasonic signal is in turn reflected from each of discontinuous surfaces and is supplied to a number of transducer elements. The array transducer 10 is composed of a plurality of transducer elements. The ultrasonic signal supplied to the array transducer 10 is converted by transducer elements into an electric signal a with magnitude proportional to an intensity of the ultrasonic signal. The electric signal is amplified to the predetermined magnitude in an amplifier 14 via switch 12, processed to a video signal in a signal processor 15, and transmitted to a cathod ray tube (CRT) 16.
In such an ultrasonic imaging system, the array transducer of a probe is composed of a plurality of transducer elements in the array form. This array form improves the resolution of a picture to be displayed with focusing an ultrasonic signal. Ultrasonic signals, which are reflected from the object and supplied to the array transducer, reach the transducer elements at different times according to the positions of the respective transducer elements. That is, the farther their positions are from the middle of the array transducer 10, the amount of time necessary to reach the transducer elements increases. Even if signal focusing can be performed at a transmission focusing step of transmitting the ultrasonic signal from the array transducer 10 to the object, it is preferred that signal focusing occur at a receiving focusing step, capable of dynamic focusing, rather than the former step. In receiving focusing, differences between reach times should be respectively compensated after delayed, they are so as to focus electric signals output from the transducer elements.
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Chang Seong H.
Park Song B.
Medison Co. Ltd.
Moller Richard A.
Williams Hezron E.
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