Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-05-22
2003-10-21
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S443000, C600S444000, C600S472000
Reexamination Certificate
active
06635018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an ultrasonic diagnosis apparatus. More particularly, the present invention relates to an ultrasonic diagnosis apparatus for, when ultrasonic beams are scanning in a living body, setting optimal transmission conditions for such each scanning line, achieving a uniform image quality over an image, and providing effective information for analysis on an application site.
2. Description of Related Art
An ultrasonic diagnosis apparatus for obtaining an image signal by transmitting and receiving an ultrasonic signal to/from a subject is used in a variety of modes utilizing noninvasive properties of such an ultrasonic signal. This ultrasonic diagnosis apparatus is mainly of type acquiring a tomographic image of soft tissues of a living body using an ultrasonic pulse reflection technique. There is a variety of imaging techniques based on this ultrasonic pulse reflection technique. In recent years, as one of such techniques, there has been paid special attention to a technique called “harmonic imaging” for imaging a high harmonics component that is a non-basic component in an ultrasonic echo signal.
The harmonic imaging includes a technique called THI (Tissue Harmonic Imaging) for sampling and imaging a high harmonics component caused by distortion of waveforms of such ultrasonic pulses while ultrasonic pulses propagates a living organ; and a technique (hereinafter, referred to as a “contrast echo”) using a contrast echo technique for sampling and imaging a contrast medium-derived high harmonics component caused by the fact that micro-bubbles (very small air bubbles) such as levobist being a main component of the contrast medium are stronger in acoustic non-linearity than a living organ, and generates many more high harmonics components.
In the case of the THI, a signal of such high harmonics component is not directly transmitted from a transducer, and is generated by the transmitted ultrasonic pulses propagating from the oscillator by a proper distance. Thus, multiple echoes from an obstacle located immediately beneath the vibrator (for example, ribs when a circulatory region is scanned from a site between ribs) are significantly reduced. In addition, more high harmonics components are generated at a site at which a sound pressure is high. Thus, the beam in a focus direction, i.e., a main lobe is enhanced, and conversely, a side lobe is reduced. As a result, a profile of a sound field beam with its excellent directivity is formed. Therefore, according to a THI having such characteristics, there is provided an advantage that a noise due to multiple reflection or side lobe artifact is reduced, and thus, an image quality is improved, and, for example, the boundary of organs and contrast ratio are improved.
On the other hand, in the case of the contrast echo, a nonlinear component relevant to a basic transmission frequency, in particular, a reflection echo signal of a secondary harmonics component, is detected, and signal levels are discriminated between organs where harmonics are hardly generated. For example, a reflection echo signal includes a basic frequency component of a transmission pulse wave and a harmonics component caused by micro-bubbles that is a main component of contrast medium. Thus, by sampling only such harmonics component from the reflection echo signal, a signal ratio of a contrast medium echo signal to a living organ echo signal is remarkably improved, and an image including a harmonics component, i.e., degree of enhancement caused by contrast medium can be obtained. Therefore, according to a contrast echo having such characteristics, the presence or absence of contrast medium in a region of interest, i.e., a blood flow perfusion or the like, can be observed merely by administrating a comparatively small amount of contrast medium, and information useful for diagnosis is obtained.
In the case of harmonics imaging such as the described THI or contrast echo, the following inconveniences have occurred as compared with a vase of imaging caused by general B mode scanning.
In general, in a sector probe generally used in examination of circulatory organs using an ultrasonic diagnosis apparatus, transmission conditions are identical in scanning lines, each of which configures an image. If a beam deflection angle is greater, the following phenomenon that a transmission sound field differs depending on scanning lines occurs because: 1) a sound pressure of transmission beams formed on scanning lines is reduced; and 2) a beam width increases as compared with a case in which transmission beams are not deflected, and spatial resolution is degraded. Thus, in a conventional B mode scan of ultrasonic beam, in order to take countermeasures against the phenomenon, there is employed a technique for adjusting an image quality such as a receiving gain every scanning line from a receive signal from a non-uniform transmission sound field, thereby generating more uniform images.
However, such countermeasures assume a case of a general B mode image, failing to assume a case of harmonics imaging such as THI or contrast echo.
That is, in harmonics imaging, a transmission sound field, in particular, a sound pressure becomes an important factor relevant to sensitivity, and there is a limitation to compensating for non-uniformity of a transmission sound field by adjustment of a received image quality. Thus, the uniformity of the transmission sound field is required for fully achieving these advantageous effects. The intensity of the harmonics component is proportional to a square of the sound pressure, and thus, a receiving gain having a square in amplitude must be corrected as compared with a conventional B mode. A change in such receiving gain causes a change in noise level, thereby producing a non-uniform image with its different noise level in image.
In harmonics imaging, such tendency is more significant in the case of a contrast echo utilizing micro-bubbles (for example, levobist) that is a contrast medium. That is, in the case of THI, even if the transmission sound pressure is low, although the receiving gain is increased concurrently, whereby a noise component increases in proportional to such increase, sampling/correction of a high harmonics component is possible. In contrast, in the case of contrast echo, if the transmission sound pressure is low, micro-bubbles to be detected may not make a nonlinear response. In such a circumstance, even if the receiving gain is increased to the maximum, it is difficult to detect a micro-bubble derived high harmonics component.
In addition, the beam width generally increases as the transmission beam deflection angle increases irrespective of whether or not harmonics imaging is carried out. With respect to this phenomenon, the non-uniformity of spatial resolution occurs. In particular, in the case of parallel, simultaneous receiving, there is a possibility that a phenomenon such as beam curving is increased.
The foregoing problems apply to another probe such as linear probe as well as sector probe. That is, these problems apply to all the probes that undergo scanning under the same transmission conditions, although actual transmission sound fields are different from each other relevant to a respective one of the scanning lines in order to form the same transmission beams.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing conventional problems. It is a primary object of the present invention to provide an ultrasonic diagnosis apparatus for scanning the inside of a living body by using electronic scanning, and generating and displaying an image, wherein an entirely uniform image quality with its less non-uniformity is achieved, and more useful information is provided by diagnosis at a clinical application site.
It is another object to achieve an entirely uniform image quality with its less non-uniformity, and to provide more effective information for diagnosis at a clinical application site in the case of harmonics imaging such as THI o
Kamiyama Naohisa
Kawagishi Tetsuya
Mine Yoshitaka
Jaworski Francis J.
Jung William
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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