Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-06-15
2003-06-03
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S458000, C128S916000
Reexamination Certificate
active
06572548
ABSTRACT:
REFERENCE TO RELATED APPLICATION
The present patent application claims foreign priority benefits under 35 U.S.C. §119 to Italian patent application No. SV2000A000027, filed Jun. 22, 2000, now pending.
BACKGROUND OF THE INVENTION
The invention relates to a method of ultrasound imaging, including the following steps:
transmitting ultrasonic beams generated by transducers into an object volume corresponding to an object body or a part thereof;
receiving and storing echo signals generated by the ultrasonic beams in said object volume;
processing the received signals into image data associated to image dots or lines of a video display;
displaying at least a few image data on the display in accordance with parameters set by the user and related to a predetermined section or projection plane of the image of said object volume;
processing of ultrasonic beams and/or displaying being specifically predetermined with reference to a preliminary selection of a section plane or an image projection plane of the object volume to be imaged.
Methods of this type are known, for instance, from U.S. Pat. No. 5,396,890 or EP 952,463 or U.S. Pat. No. 5,226,113, U.S. Pat. No. 5,928,151 and U.S. Pat. No. 5,497,776.
These known methods aim at performing three-dimensional ultrasound imaging by a number of different techniques, e.g. acquiring a succession of section planes of the object body, processing the individual reflected echoes in each plane and constructing a three-dimensional image memory in which the received echo signals are associated to a set of voxels, i.e. image dots of a three-dimensional image, while accounting for the relative position of the individual scan planes.
During image acquisition, the whole object volume is generally scanned, through successive two-dimensional section planes staggered to a predetermined extent to cover the whole object volume. Then, the signals of the reflected echoes are processed and transformed into image data in the form of a three-dimensional matrix of image dots. This process must be substantially exhaustive to allow the desired image to be displayed in a plane having any spatial orientation and crossing the object volume. Hence, a selected image may be displayed only after scanning the whole volume and, above all, after completely processing the echo signals to generate the three-dimensional image data matrices. Therefore, image displaying times are relatively long and require highly powerful and costly hardware to obtain an acceptable processing time. Moreover, these very long displaying times are a severe shortcoming when related to the difficulties the patient encounters in keeping perfectly still for long periods of time and when transient events are to be observed whose starting time is not exactly predefined. An important example consists in the combined use of ultrasound imaging with the so-called contrast agents. These substances are injected into the tissues under examination. A certain time, of a few tens of seconds, passes before they reach the object region. Further, the time during which contrast agents remain in the object tissues, as regards both their passage therethrough and their decay, is short, also being of the order of a few tens of seconds. Hence, by using prior art imaging methods, it may be frequent that scanning is performed when contrast agents have not reached the object region yet. If this is the case, the doctor or the user will only be able to assess this condition later, when processing is completed, hence in unfavorable conditions, and will not have the time for a new image acquisition in order that imaging may take place when contrast agents are present or have not decayed in the object region. In this case, a new injection of contrast agents will be required to repeat scanning. Such a situation is definitely undesirable, as it reduces the non-invasiveness degree of the ultrasound imaging method.
Identical or similar problems are encountered when the probe is not properly positioned, whereby even though scanning is performed while contrast agents are present in the object region, it must be repeated, for instance if probe orientation does not allow scanning of the volume of interest and provides an unusable or anyway useless image.
The multiple techniques described in the above documents are based on a concept shared by all ultrasound imaging methods or systems, i.e. that the user may first select an imaging type, related to an imaging mode, e.g. the so-called B-mode, Doppler, Power Doppler, harmonic imaging, etc.
The selection of the view or section plane of interest takes place after image acquisition and processing of image data matrices. These steps are substantially preset in the apparatus.
The invention has the object of providing an ultrasound imaging method, particularly in three dimensions, which allows to obviate the drawbacks of prior art methods, without requiring any considerable complication of the method and higher costs of the apparatus for implementing it, while allowing a real time image display in section or projection planes having any orientation in space and with reference to the volume of interest.
The invention achieves the above purposes by providing a method of ultrasound imaging as described above, which has the following additional steps:
defining a virtual volume coincident with the object body or part thereof or a three-dimensional reference system, provided it has a definite orientation with respect to the imaging planes generated by the ultrasound probe;
selecting the section plane of the object body and/or part thereof along which ultrasound imaging is to be performed.
determining the position-defining coordinates for the dots which form said section plane along which imaging is to be performed, with reference to the virtual volume;
restricting the scanning operation to the region which coincides with said section plane along which imaging is to be performed;
transmitting the transmission signals and receiving the reflected echoes only along such lines of view of the probe which coincide with the surface or the projection slice of the selected section plane along which imaging is to be performed;
only processing and displaying the received echo signals.
This method drastically reduces the number of steps required for image data processing from the received signals and considerably speeds up such processing. In fact, thanks to the preliminary selection of the section plane of the object body or part thereof to be imaged, the method restricts not only the amount of signals to be processed for imaging, but also scanning times, with the probe transmitting and receiving not along the whole scan plane thereof, but only for a limited slice, coinciding with said projection region of the selected section plane, along which imaging is to be performed.
It will be understood that the principle of this method is reversed as compared to the one currently in use. At present, as stated above, the modes of transmitting and receiving ultrasonic signals and processing reflected echoes are preset and independent from the section plane or projection plane of the object volume to be imaged and the selection of said planes, or more particularly of their orientation with respect to the object volume takes place a posteriori, i.e. when substantially all useful signals have been converted to image data by scan converters. In the present invention, it is the selection of the section plane or of the projection plane to be imaged which determines the modes of transmitting and receiving ultrasonic signals, as well as processing modes, aimed at generating the image data three-dimensional matrix, wherefrom images are generated. From said transmission and reception, i.e. from the scanning operation, all the regions which do not intersect or fall within the selected section plane along which imaging is to be performed, are excluded, to filter out all the signal portions which do not contribute to form dots, lines or unit volumes of the image coinciding with or belonging to the section plane to be imaged.
It is important
Esaote S.p.A.
Imam Ali M.
Lateef Marvin M.
Woodard, Emhardt, Naughton Moriarty & McNett LLP
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