Surgery – Truss – Pad
Patent
1994-08-29
1996-05-28
Manuel, George
Surgery
Truss
Pad
73626, A61B 800
Patent
active
055201849
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an ultrasonic diagnostic method and an ultrasonic diagnostic apparatus and, more specifically, to an ultrasonic diagnostic method that employs grating lobes to enhance real-time performance, to enlarge visual field and to improve S/N ratio, and an ultrasonic diagnostic apparatus for carrying out the ultrasonic diagnostic method.
BACKGROUND ART
In carrying out Doppler color flow mapping (CFM) by the conventional ultrasonic diagnostic apparatus, the pitch p of oscillatory elements and the wavelength .lambda. of an ultrasonic sounding wave are determined so as to meet an inequality, p<.lambda./2 so that only a main lobe exists in the visual field, i.e., so that no grating lobe exists in the visual field, and the visual field is scanned by the main lobe.
The grating lobe is prevented from existing in the visual field to prevent formation of a virtual image by the grating lobe.
Although not directly related to the present invention, because the grating lobe is different from the side lobe, a technique of preventing a virtual image attributable to the side lobe is disclosed in Japanese Patent Laid-open (Kokai) No. 61-11030.
In the Doppler CFM by the ultrasonic diagnostic apparatus, the real-time performance can be enhanced by increasing the frame rate F, the visual field can be enlarged by increasing the number N of sound rays, and the S/N ratio can be improved by increasing the pulse repetition frequency P.
However, since the relation between the frame rate F, the number N of sound rays, the pulse repetition frequency (the number of successive pulses to cause the phase variation of one sound ray) P, the maximum detection depth Dmax and the sound velocity c is expressed by: F.times.N.times.P.times.2D.sub.max /c<1, the increase of the frame rate F, the increase of the number N of sound rays, and the increase of the pulse repetition frequency P contradict each other.
Accordingly, the enhancement of the real-time performance, the expansion of the visual field or the improvement of the S/N ratio, entails inevitably the sacrifice of the visual field or the S/N ratio, the real-time performance or the S/N ratio, or the real time performance or the visual field.
DISCLOSURE OF THE INVENTION
Accordingly, it is an object of the present invention to provide an ultrasonic diagnostic method capable of enhancing real-time performance, enlarging visual field and improving S/N ratio without sacrificing any of real-time performance, visual field and S/N ratio, and to provide an ultrasonic diagnostic apparatus for carrying out the ultrasonic diagnostic method.
In a first aspect of the present invention, an ultrasonic diagnostic method comprises; dividing a visual field into two or more sections; generating sounding waves forming a main lobe and grating lobes to scan the sections of the visual field respectively by the main lobe and the grating lobes; separately processing an echo wave received along the direction of the main lobe and echo waves received along the directions of the grating lobes to form images of the sections separately; and combining the images of the sections to display an image of the visual field.
In a second aspect of the present invention, an ultrasonic diagnostic apparatus comprises: an ultrasonic probe; a transmission control means for making the ultrasonic probe generate sounding waves forming a main lobe and grating lobes and scan two or more sections of a visual field by the main lobe and the grating lobes, respectively; a main lobe receiving and processing means having a directivity only in the direction of the main lobe and capable of forming an image of the section scanned by the main lobe; a grating lobe receiving and processing means having directivities only in the directions of the grating lobes and capable of forming images of the sections scanned by the grating lobes; and an image display means for combining the image of the section scanned by the main lobe and the images of the sections scanned by the grating lobes and displaying an
REFERENCES:
patent: 4497322 (1985-02-01), Nagasaki
patent: 4779622 (1988-10-01), Nakamura
GE Yokogawa Medical Systems Limited
Kojima Moonray
Manuel George
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