Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-09-29
2002-05-21
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S439000, C600S443000, C600S472000
Reexamination Certificate
active
06390978
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to an imaging method for determining a physical or chemical condition of tissue in human or animal bodies using ultrasound, where at least one ultrasonic pulse in the diagnostic frequency and power range is directed into the tissue, and the ultrasonic echo pulse reflected by the tissue is received and processed in ultrasonographic image processing means.
The invention further generally relates to an imaging system for determining a physical or chemical condition of tissue in human or animal bodies using ultrasound, having ultrasound-generating means for generating at least one ultrasonic pulse in the diagnostic frequency and power range, ultrasound application means for applying the ultrasonic pulse into the tissue, ultrasound receiving means for receiving the ultrasonic echo pulse reflected in the tissue and ultrasonographic image processing means for processing the ultrasonic echo pulse.
An imaging method of the before-mentioned kind, also known as ultrasonic echo pulse method, and an imaging system of the before-mentioned kind are generally known.
In imaging methods of this kind an electric pulse is converted to an ultrasonic pulse for example by means of a piezoelectric ultrasonic transducer. The electronic pulse is then injected into the tissue under examination. As the ultrasonic pulse enters the tissue, part of it is reflected at the boundary surfaces of the tissue, while part of it penetrates deeper into ion the tissue. Consequently, this method permits several tissue layers, lying one behind the other, to be localized and the condition of those tissue layers to be determined.
Physical condition in the meaning of the present invention is meant to describe, for example, geometrical parameters, such as the extension in space, the position in space, the thickness of the tissue, as well as other physical variables, such as the density of the tissue under examination as a function of the locus. The method is, however, also simply used to describe the visual display of tissue in an image-display unit. The term chemical condition is used, for example, to describe the composition of the tissue.
The ultrasonic echo pulse method allows tissues of organs to be visually displayed and information regarding the tissue to be acquired, it being possible, for example, to determine a pathological condition of the tissue by evaluation of the ultrasonographic image. In order to generate a two-dimensional sectional image a continues sequence of ultrasonic pulses is injected into the tissue through a scanning process which may be of an electronic or mechanical kind.
The advantages of the ultrasonic echo pulse method over the x-ray imaging method lie mainly in the fact that it protects the tissue and can be realized at low cost. Another advantage of the ultrasonic echo pulse method is the relatively great depth of penetration of the ultrasonic pulses into the tissue.
A disadvantage of the ultrasonic echo pulse method lies, however, in the comparatively low axial resolution of the ultrasonographic image. The term axial resolution as used in this connection means the resolution along the axis of irradiation. The resolution along the axis of irradiation is dependent from the frequency and spread of the injected ultrasonic pulse.
At present, standard frequencies in the range of between 5 to 10 MHz are used for the abdominal region. For special tissue structures near the surface, frequencies of up to 50 MHz are already used today. Although such high frequencies achieve improved axial resolution, the attenuation coefficient of the tissue likewise increases linearly with the frequency so that in the case of very high frequencies, which in principle would allow improved resolution, the depth of penetration of the ultrasound into the tissue is heavily limited due to physical reasons so that the advantage of ultrasound, namely that depth information can be obtained about the tissue in a tissue-sparing way, is lost.
The highest possible axial resolution obtainable with high-frequency ultrasound is at present in a range down to 30 &mgr;m.
In WO 97/32182 an optical imaging method is described which is known as “optical coherence tomography (OCT)”. With OCT a light beam is generated and splitted up into a measuring light beam and a reference light beam, the measuring light beam being directed into the tissue to be examined. The relative optical path between the reference light beam and the measuring light beam is adjusted, and the measuring light beam scattered back from the tissue is brought to interference with the reference light beam.
In one embodiment in WO 97/32182 an applicator for applying the measuring light beam into the tissue to be examined is described, which is configured in form of an endoscope, in a tip of which a prism or a silver-coated mirror is disposed so that the measuring light beam is injected into the tissue to be examined perpendicular to the longitudinal axis of the endoscope. An ultrasonic transducer is disposed in the tip of the endoscope which directs ultrasonic waves onto the silver-coated mirror which then are injected from the mirror into the tissue to be examined in opposite direction of the measuring light beam.
Further, from WO 98/55025 an ultrasonographic imaging method is known, where it is proposed to combine the ultrasonographic imaging method with optical coherence tomography. In this document, however, it is not described how to carry out the method of optical coherence tomography in connection with an ultrasonographic imaging method.
It is an object of the present invention to improve an imaging method and an imaging system of the type described above so that improved resolution of the imaging method is achieved in order to obtain more precise information about the tissue without losing the depth information.
SUMMARY OF THE INVENTION
According to the present invention, an imaging method for determining a physical or chemical condition of tissue in a human or animal body using ultrasound is provided, comprising the steps of directing at least one ultrasonic pulse in the diagnostic frequency and power range into said tissue along a beam axis, receiving an ultrasonic echo pulse reflected by said tissue, processing said ultrasonic echo pulse in ultrasonographic image processing means, generating at least one light beam and splitting said light beam into at least one measuring light beam and at least one reference light beam, directing said measuring light beam along said beam axis into said tissue, such that said ultrasonic pulse and said measuring light beam are superimposed, adjusting a relative optical path between said reference light beam and said measuring light beam, and bringing said measuring light beam scattered back by said tissue into an interference relationship with said reference light beam and processing the interferometric signal in optical image processing means.
Further, according to the present invention, an imaging system for determining a physical or chemical condition of tissue in a human or animal body using ultrasound is provided, comprising ultrasound-generating means for generating at least one ultrasonic pulse in the diagnostic frequency and poser range, ultrasound application means for applying said ultrasonic pulse into said tissue; ultrasound receiving means for receiving an ultrasonic echo pulse reflected by said tissue, ultrasonographic image processing means for processing said ultrasonic echo pulse, light generating means for generating at least one light beam, beam splitter means for splitting up said light beam into at least one measuring light beam and at least one reference light beam, adjusting means for adjusting a relative optical path between said measuring light beam and said reference light beam, light application means for applying said measuring light beam into said tissue, said light application means and said ultrasound application means being configured such that said ultrasonic pulse and said measuring light beam are superimposed and directed into s
Beck Gerd
Irion Klaus M.
Imam Ali M.
Karl Storz GmbH & Co. KG
Lateef Marvin M.
St. Onge Steward Johnston & Reens LLC
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