Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-05-04
2003-11-25
Manuel, George (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S437000, C600S454000, C600S455000
Reexamination Certificate
active
06652460
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention pertains to a method for ultrasonic imaging, particularly of moving bodies, such as tissues, flows, or the like, which includes the following steps:
Periodically emitting ultrasonic pulses along a predetermined view line and with a predetermined repetition rate through one or more transducers;
Receiving the echoes produced by the body and/or the tissues or flows and transforming them into echo signals;
Processing the echo signals for extracting information therefrom and for generating an image based on such information.
Particulalrly the invention relates to an apparatus for implementing and using the method and to an apparatus for detecting intraoperative surgical instruments and calcifications or similar biological structures
The ultrasonic imaging technique consists in generating an ultrasonic pulse beam, having frequencies in the RF range, from a set of aligned emitting transducers to illuminate or soundproof a definite section of a body or of a body part to be examined. As the individual pulses propagate in the body according to a predetermined penetration depth, as determined by their nature and by the nature of the body being examined, they are reflected by the structures forming the body and generate reflected echoes, which are detected by detectors and transformed into echo signals. The different structures or types of tissues encountered by the illuminating pulses while the latter propagate in the body along a propagation axis or view line produce changes in the emitted carrier, in the form of amplitude modulations or phase variations. These changes are the information to be extracted by the echo signals to obtain the ultrasonic image.
In the simplest form of ultrasonic image, the so-called B-mode image, a black and white image is generated, in which the different tones of gray, black and white are related to the intensity or the amplitude of the received echo signal. Processing requires synchronization, on a predetermined time base, of the emitted pulses and of the received echo signals to accurately reconstruct the zones wherefrom the echoes arrive along the propagation line, in accordance with the propagation of the illuminating pulse and further to allow correlation of the echo signals to their respective illuminating pulse-emitting transducers.
Therefore, the information contained in the echo signals may be interpreted either with respect to amplitude modulations of the illuminating pulse, as in the so-called B-Mode, or with respect to phase variations, such as in the so-called Doppler, Power Doppler, Color Doppler, or the like.
From surgical point of view there is a need to control position and displacement of intraoperative utensils in the human or animal body by means of a non invasive technique which is capable of giving an intelligible image of the region where the intraoperative utensil is placed.
From the diagnostic point of view, there is the need of noninvasively imaging particular tissue types, such as for example calcifications or similar biological structures in the human and animal body. This kind of tissues are not simple to be scanned with ultrasound techniques.
From the diagnostic point of views there is also a very high interest in the ultrasonic imaging of flows in the human bodies, particularly of blood flows. The problem consists in that most of the physiological liquids, such as blood, urine, bile, cyst contents, etc. are anechogenic, i.e. transparent, or only partially reflect ultrasounds.
Thus, ultrasonic imaging with the conventional B-Mode method is not feasible and produces poor, unusable results. Therefore, several techniques have been implemented to detect flows, particularly blood flows, with ultrasound apparati, the so-called Doppler, Power Doppler, Color Doppler techniques, or the so-called Harmonic Imaging technique, in which the echo signal is examined with respect to its harmonics. These prior art techniques require both processing in the frequency or phase domain, which add a considerable processing burden, and the use of the so-called contrast agents, consisting of microbubbles, which, when injected in spontaneous flows, have a hyperechogenic behavior.
Actual techniques for imaging of physiological flows are not optimized for imaging of surgical apparatus or for biological structures such as calcifications. Indeed imaging apparatus and techniques normally are arranged and chosen in such a way as to avoid the contributes of the scattered ultrasonic beams due to the presence in the region being scanned of surgical intraoperative utensils or biological structures such as calcifications.
The present invention has the object to provide a method for ultrasonic imaging, particularly of moving bodies, such as intraoperative utensils, tissues, flows or the like, which allows fast real time and simple imaging of the said utensils and or tissues and also real time imaging of body flows even without using contrast agents, without excluding the combined use thereof, and at the same time is highly sensitive to movement, thereby allowing to considerably simplify processing of echo signals for extracting and displaying information.
The invention achieves the above purposes by providing a method for ultrasonic imaging, particularly of moving bodies, such as surgical inytraoperative utensils, tissues, flows, or the like, which includes the following steps:
determining a real time vector difference between the echo signals of two pulses successively emitted at predetermined time intervals;
using said difference signal as an information signal for ultrasonic imaging.
Therefore, a direct and vector difference between the received RF echo signals is determined, which involves suppression of the contributions or portions of the echo signals produced by the stationary parts of the body, tissues or the like, whereas the portions of the echo signals produced by moving bodies, such as intraoperative surgical utensils, calcifications or the like and/or tissues or elements, such as red blood cells, etc. give non-zero contributions due to displacement of said moving bodies or parts.
Processing of the difference signal for imaging is performed as in conventional ultrasonic imaging techniques.
The method of the invention allows ultrasonic imaging of moving bodies, particularly of spontaneous body flows, i.e. of blood flows or the like, without using radiopaque agents.
The method of the invention is highly sensitive to movement, therefore it can generate images of very slow or low flow rate flows or of parts which perform micromovements.
The resulting images have a high definition and a considerable level of contrast and, in combination with high sensitivity to movement and micromovement of bodies in the operating range of the probe, they allow to display and monitor movements of invasive surgical instruments, such as microinstruments, intraoperative probes, needles, etc. better than the other prior art ultrasonic methods.
Thanks to the high sensitivity of the method, ultrasonic images may be also obtained from biological structures which are highly echogenic, but perform little or very slow movements, i.e. perform even slow micromovements, such as calcifications or breast cancer formations.
In order to adapt the imaging technique according to the invention to the different kind of analysis needed, the difference RF signal is further treated by non linear filtration of the signal components which are not of interest for the specific analysis and may hinder correct evaluation of the interesting part of the echo signals.
Indeed high echogenic tissues or materials may contribute very significatively to the echo signals and with such an high response that the contribution to the signal due to the tissue of interest is reduced to a very insignificant part of the signal.
Due to the said sensitivity of the method according to the invention to micromovements, high ecogenic materials, such as in the case of surgical utensils or calcifications may generate some sort of intensity flashes that let the contribution of less ecogen
Fabiano Mauro
Merlanti Marco
Pellegretti Paolo
Esaote S.p.A.
Jung William C.
Manuel George
Woodard Emhardt Moriarty McNett & Henry LLP
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