Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-05-31
2002-08-20
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C128S916000
Reexamination Certificate
active
06436049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diagnostic ultrasound apparatus capable of providing a three-dimensional image by scanning in real time a three-dimensional region of an object to be diagnosed and a method of switching over the images, and in particular, the apparatus and the method directed to a contrast echo technique with a contrast agent of which essential constituent is microbubbles, in which the contrast echo technique is suitable for observation of dynamics of flows of blood through vessels, observation of dynamics of flows of blood in an organic tissue by means of detecting perfusion, and quantitative measurement of those dynamics.
2. Description of the Prior Art
Ultrasound signals have now been clinically used in various fields, in which one usage is an application to a diagnostic ultrasound apparatus. The diagnostic ultrasound apparatus acquires image signals through transmission and reception of an ultrasound signal toward and from an object and is used in a variety of modes utilizing non-invasiveness of the signal. One typical type of diagnostic ultrasound apparatus produces tomographic images of a soft tissue of a living body by using a method of ultrasound pulse reflection imaging. This imaging method non-invasively produces tomographic images of the tissue. Compared with other medical modalities such as a diagnostic X-ray apparatus, X-ray CT scanner, MRI system, and diagnostic nuclear medicine system, this imaging method is advantageous in many aspects such that real-time display is possible, a compact apparatus is manufactured at relatively lower costs, the exposure of X-rays will not occur, and blood imaging is possible thanks to ultrasound Doppler imaging.
Thus, this imaging is widely used in diagnosis of the heart, abdomen, mammary gland, urinary organs, and obstetrics and gynecology, and possesses various advantages. In particular, pulsation of the heart or motion of a fetus can be observed in real time just through a manipulation that is as simple as placing an ultrasound probe on the patient's surface. Still, since there is no need to worry about patient's exposure, screening can be carried out repeatedly many times. Furthermore, there is an advantage that an apparatus can be moved to a bedside position to examine a patient easily.
In the field of this diagnostic ultrasound apparatus, for screening the heart or abdominal organs, contrast echo imaging has newly been introduced and spotlighted recently, by which an ultrasound contrast agent (hereinafter called contrast agent) is trans-venous injected into a patient for evaluating the kinetics of blood flow. Since the trans-venous injection of a contrast agent is less invasive than trans-arterial injection type of contrast echo imaging, diagnosis using such trans-venous injection technique tends to become popular. A main constituent of the contrast agent is composed of minute bubbles (microbubbles) that act as sources of reflecting ultrasound waves. The larger the amount and concentration of an injected contrast agent is, the larger the effect of contrast imaging is. However, due to some characteristic of microbubbles of a contrast agent, a situation where radiation of ultrasounds results in a shortened duration of the contrast effect. Considering such a situation, a contrast agent having characteristics of long persistency and high durability against sound pressure has been developed in recent years.
Concurrently with such development of imaging techniques, a need for three-dimensional imaging for ultrasound diagnosis has been needed, like in the fields of the CT and MRI. In a three-dimensional volume image, information about an object in its back and forth direction is acquired in addition to information obtained from a two-dimensional tomographic image, it is possible to know more clearly shapes of tissues and dynamics of flows of blood. Thus, in conducting ultrasound diagnosis, visualizing three-dimensional images has drawn attention as a way of developing a new diagnostic field.
As one way of three-dimensional scanning, there is a technique of acquiring three-dimensional echo data as a probe of which ultrasound transducers arranged one-dimensionally is moved along the body surface of a patient. Practically, a convex probe or linearly arrayed probe for abdominal imaging is moved by hand or mechanically. Alternatively, a trans-esophagus multi-plane probe having a mechanism of rotating a sector probe is used.
However, the above one-dimensional probe requires that it take a large amount of time to acquire three-dimensional echo information itself even when any scanning method is adopted, compared to the conventional cross sectional scanning method. A fast-moving object, such as the heart, is therefore difficult to be traced with high accuracy. Even if an object does not move so fast as does the heart, distortion of images becomes too large unless a probe is located in a sufficiently secured manner.
In recent years, a diagnostic ultrasound apparatus has been researched eagerly, which comprises a probe having phased array transducers arranged two-dimensionally so as to scan an ultrasound beam three-dimensionally is used to scan a three-dimensional volume region at a frame rate closer to realtime scanning, for example, 30 frames/sec.
Though well known, the advantages of a three-dimensional volume image include, obtaining information about an image in its the back and forward direction, which has not been given by the conventional two-dimensional tomographic image; making it possible to observe a region of interest from a point viewing along in an arbitrary direction; and others. Such a three-dimensional volume image (three-dimensional information) is displayed on a two-dimensional planar display, except display that uses particular volume image display devices. This display is realized by cutting out a two-dimensional section from a three-dimensional volume image so as to provide the section image, or producing a projection image viewing a three-dimensional volume image from a specified point of view so as to provide the projection image. This way to produce projection images include a maximum intensity (luminance) projection technique (Max IP technique) and a minimum intensity (luminance) projection technique (Min IP technique).
Although the techniques of visualizing the foregoing projection images are relatively easily available for displaying an object in the air, there are some cases where they cannot offer an effective display for ultrasound images.
In other words, owing to the fact that an ultrasound image into which a contrast agent has not been injected represents an object's tissue region corresponding to the foregoing air and producing an echo signal of which intensity is relatively high, displaying a two-dimensional projected image using, for example, the maximum intensity projection technique may result in that constituents, such as tumors in tissue and blood vessels, are hidden by a tissue image portion. In this case, the minimum intensity projection technique can be used to extract blood vessels on the projection image, because echo signals from the blood vessel portion represent smaller intensities and their display luminance degrees are lower.
In contrast, when carrying out a contrast echo technique with a contrast agent injected, tissue and blood vessel systems are subject to a contrast effect and higher in luminance than organic tissue. As a result, for the contrast echo technique carried out after the start of an injection of the contrast agent, the maximum intensity projection technique is more advantageous.
In general, in cases the contrast echo technique is performed, it is not necessarily true that injecting a contrast agent is merely followed by scanning. It is necessary that both images acquired before and after injecting the contrast agent be traced sequentially in time. In the case that the maximum intensity projection (Max IP) technique or the minimum intensity projection (Min IP) technique are selectively emplo
Kamiyama Naohisa
Ogasawara Yoichi
Imam Ali M.
Kabushiki Kaisha Toshiba
Lateef Marvin M.
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