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DESCRIPTION JPH0444750

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DESCRIPTION JPH0444750
[0001]
[Object of the Invention] (Industrial field of application) The present invention relates to an
ultrasonic diagnostic apparatus for detecting an echo signal obtained from a probe whose
scanning angle is variable to create an ultrasonic image. (Prior Art) In recent years, blood flow
diagnosis by ultrasonic Doppler method for obtaining blood flow velocity information noninvasively from outside the body is being put to practical use. FIG. 4 is an explanatory view of
blood flow diagnosis using such an ultrasonic Doppler method, in which the ultrasonic probe 1 is
brought into contact with the body surface of the living body 2 and an ultrasonic beam 3 is
transmitted. Then, the frequency fo- of the echo signal obtained from the red blood cells 5
flowing in the blood vessel 4 slightly deviates from the transmission frequency f0. Then, the
blood flow velocity V of the red blood cells 5 is calculated based on this shift amount. FIG. 5
shows a conventional example of an ultrasonic diagnostic apparatus including the ultrasonic
probe 1. As illustrated, the echo signal obtained from the ultrasonic probe 1 is subjected to a
band pass filter 6 to remove components outside a predetermined band, and then to a
logarithmic amplifier via a bypass filter 7 and a system noise removal circuit 8. It is sent and an
ultrasound image is created. At this time, it is known that the azimuth resolution is improved as
the frequency band of the band pass filter 6 is narrower, and the distance resolution is improved
as this band is wider. The characteristic of the band pass filter 0 was set so that (Problems to be
Solved by the Invention) In addition, since such a conventional device emphasizes the distance
resolution 2 while doing so, the azimuthal resolution is not good when the blood flow diagnosis
shown in FIG. 4 is performed. There is a problem that the accuracy of the image at the time of
oblique scanning is poor. The present invention has been made to solve such conventional
problems, and its object is to provide an ultrasonic diagnostic apparatus capable of improving the
azimuth resolution. [Composition of the Invention] (Means for Solving the Problems) "-E1. In
order to achieve the target, the present invention is directed to an ultrasonic diagnostic
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apparatus for detecting and creating an ultrasonic image after passing an Euclidean code
obtained from a probe having a variable elevation angle through a band pass filter. A plurality of
different band pass filters arranged in parallel, 7 in accordance with the scanning angle of the
probe; Alternatively, the band pass filter is selected. (Operation) According to the abovementioned configuration, as the scanning angle by the ultrasonic probe is inclined with respect to
the vertical scanning, the narrow band pass filter of the frequency band is selected to be selected.
Therefore, an image of high distance resolution can be obtained at the time of vertical scanning,
and an image of good azimuth resolution can be obtained as the scanning angle is inclined. As a
result, high-precision ultrasound images can always be obtained regardless of the scanning angle.
(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. As
illustrated, the ultrasonic diagnostic apparatus of the present embodiment transmits an
ultrasonic wave to a subject (not shown) and receives an echo signal of the transmission wave,
and nj of the obtained echo signal. A switch for switching the power to output to the first band
pass filter 6a or the second band pass filter 6b, and a bypass filter 7 for removing low-pass
components of output signal components of both band pass filters 6a and 6b; The system has a
system noise removing circuit 8 for removing system noise mixed in the bypass filter. The first
band pass filter 6a has a narrow frequency band and has, for example, a filter characteristic as
shown in FIG. 2 (A). The second band pass filter 6b widens the respective frequency bands, and
has, for example, the = noise characteristic as shown in FIG. 2 (B). Next, the operation of this
embodiment will be described. Now, in the case of scanning vertically to the body surface of the
subject, a conventional scanning method may be used, and the switch 9 shown in FIG. 1 is
switched to the second band pass filter 6b side. As this switching method, the scanning direction
by the probe J may be detected and switched λ by software or manually operated. As a result,
the same circuit as that of the conventional device shown in FIG. 5 is formed, so that the distance
resolution is improved. This is because, as the frequency band of the second band pass filter 6b is
wide, as shown in FIG. 3 (A), the speckle pattern 11 of the object is elliptical, and each speckle
pattern 11 is chained. This is because continuous lines can be obtained by connecting them. If
the second band pass filter 6b is selected without scanning the switch 9 and scanning is
performed in an oblique direction, the elliptical speckle pattern 11 is not shown in FIG. 3 (B). The
image is projected so as to be perpendicular to the scanning direction. For this reason, a
continuous line can be obtained. Then, when the switch 9 is switched to the first band pass
“no” side, the frequency band is narrowed as shown in FIG. 2 (A), whereby the speckle pattern
11 becomes circular. As a result, as shown in FIG. 3 (C), each speckle pattern 11 (7 is connected,
thereby a continuous straight line without a break 1) can be obtained.
In this manner, in the present embodiment, band pass filters with different frequency bands are
selected for scanning in the case of scanning perpendicularly to the body surface with the
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ultrasonic probe and in the case of scanning in the oblique direction. ing. Therefore, it is possible
to obtain an ultrasound image always with high accuracy regardless of the direction of the scan.
Although the present embodiment shows an example in which two band pass filters are arranged
in parallel, the present invention is not limited to this, and three or more band pass filters are
provided, and the scan angle is inclined based on the vertical scan. If a narrow band pass filter of
the frequency band is selected, a more accurate ultrasonic image can be obtained. [Effects of the
Invention] As described above, in the present invention, a plurality of band pass filters having
different frequency bands are provided, and the narrow band of the frequency band is obtained
as the scanning angle of the ultrasonic probe is inclined with respect to vertical scanning. A pass
filter is selected. Therefore, an effect is obtained that an ultrasonic image with high accuracy can
always be obtained regardless of the scanning angle.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory
view showing a frequency band of a band pass filter, FIG. 3 is an explanatory view showing a
speckle pattern of an ultrasonic image, and FIG. Explanatory drawing of the blood-flow diagnosis
which used the ultrasonic doppler method, FIG. 5 is a block diagram which shows a prior art
example.
1: Ultrasonic probe 6a: first band pass filter 6b: second band pass filter
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