News Column

Patent Issued for Ultrasonic Diagnostic Apparatus

June 25, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventor Matsumura, Takeshi (Tokyo, JP), filed on April 14, 2009, was published online on June 10, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8747320 is assigned to Hitachi Medical Corporation (Tokyo, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Generally, an ultrasonic diagnostic apparatus is for performing a diagnosis such that ultrasonic waves are transmitted into a body of an object from an ultrasonic probe (hereinafter, simply referred to as a probe), a reflected echo signal of the ultrasonic waves which have been reflected from the inside of the body is received by the probe, and an image or the like which is suitable for the test of a tissue, a function, or the like inside the body is created based on the received reflected echo signal (RF signal).

"In such an ultrasonic diagnostic apparatus, for the test by a B mode image, it is preferable to obtain an image with a high image quality by placing the probe on the object with a relatively strong force, pressing and deforming the body tissue so that the deep tissue can be closer to the probe, and imaging the tissue since the ultrasonic waves attenuate in the course of the propagation inside the body tissue. On the other hand, in the bloodstream test such as the Doppler measurement, the CFM, or the like, since it is not possible to obtain correct information on the bloodstream because the cross-section of the blood vessel is deformed when the probe is placed on and pressed against the body tissue with an excessively strong force, it is preferable to perform the test with the pressurizing state which is gentler than that at the time of the B mode diagnosis. In addition, since the body tissue has a nonlinearity in which the hardness of the tissue changes in accordance with the strength of the pressurizing even in the test by elastography for creating an image of elastic information regarding the hardness or the softness of the body tissue, it is important to perform a diagnosis based on an elasticity image obtained under a pressurizing state with a constant absolute pressure.

"Accordingly, it is preferable to measure and display the absolute pressure applied to the body tissue in real time since there is a concern that an appropriate prompt diagnosis is hindered if the test proceeds in an inappropriate pressurizing state in various testing methods or when the testing method is changed, for example.

"In order to measure an actual pressure to be applied to the body tissue of the object, that is, an absolute pressure to be applied to the body tissue (hereinafter, simply referred to as an absolute pressure), Patent Literature 1 discloses that the distortion of an elastic coupler is obtained with the use of a known displacement and distortion calculation based on a pair of RF signal frame data, which was obtained at different timings, and the obtained distortion is converted into the absolute pressure with the use of a pre-set elastic modulus of the elastic coupler.

"Thus, according to the method of calculating the pressure disclosed in Patent Literature 1, it is possible to obtain the elastic information on the hardness or the softness of the body tissue by measuring the absolute pressure applied to the object, for example."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "Problem to be Solved by the Invention

"However, although it is basically possible to detect the absolute pressure with high sensitivity and high accuracy in the method of detecting the absolute pressure by the elastic coupler according to Patent Literature 1, there is still room for improvement as described below.

"For example, when there is a part with irregular contact, in which fine unevenness, an air layer, or the like is interposed, due to a poor contact property between a contact surface of the elastic coupler on the side of the object and a body surface of the object, it is not possible to appropriately detect the boundary with the body surface of the object, and thereby it is not possible to appropriately detect the thickness of the elastic coupler in some cases. In addition, since the deformation in the contact part around the non-contact part becomes larger when there is a part with irregular contact, it is not possible to appropriately measure the distribution of the absolute value if the deformation and the distortion at the boundary part is measured and converted into the absolute pressure.

"The object to be achieved by the present invention is to accurately perform the detection of the absolute pressure.

"In addition to the above object, the object to be achieved by the present invention is to simplify the operation for detecting the absolute pressure with the use of an appropriate elastic coupler depending on the testing method or the like and thereby to enhance usability.

"Means for Solving the Problem

"As the first aspect of the present invention, in an ultrasonic diagnostic apparatus including an ultrasonic probe for transmitting and receiving ultrasonic waves while being in contact with an object, a transmitting unit for driving the ultrasonic probe, a receiving unit for receiving and processing an RF signal which is a reflected echo signal received by the ultrasonic probe, and an image creating unit for creating an ultrasonic image based on the RF signal output from the receiving unit, a pressure calculating unit for obtaining the pressure applied to the object based on the deformation of an elastic coupler which has been attached to an ultrasonic wave transmitter/receiver surface of the ultrasonic probe is provided, whereby the elastic coupler is formed to have at least two layers, and the pressure calculating unit detects the position of the boundary surface between the two layers, obtains the positional change of the boundary surface based on the detected position of the boundary surface and the initial position of the boundary surface which has been obtained in advance, and obtains absolute pressure based on the positional change and an elasticity property of the elastic coupler.

"That is, the elastic coupler is formed to have at least two layers with different ultrasonic wave reflectance properties by an elastic material having flexibility, and the boundary surface between the layers with different ultrasonic wave reflectance properties is disposed between the attachment surface which is attached to the ultrasonic wave transmitter/receiver surface and the contact surface which is in contact with the body surface of the object. The pressure calculating unit is characterized by detecting the position of the boundary surface in the thickness direction of the elastic coupler based on the RE signal output from the receiving unit, obtaining the positional change of the boundary surface based on the detected position of the boundary surface and the initial position of the boundary surface, which was obtained in advance, and obtaining the absolute pressure applied to the object based on the positional change and the pre-set elasticity property of the elastic coupler.

"Since the position of the boundary surface formed inside the elastic coupler is detected, and the absolute pressure is obtained based on the positional change, it is possible to stably detect the boundary surface inside the elastic coupler regardless of the contact property between the elastic coupler and the body surface of the object as compared with the case in which the boundary between the elastic coupler and the body surface of the object is detected. Accordingly, it is possible to accurately detect the absolute pressure. In addition, the initial position of the boundary surface in the initial state in which no pressurizing force is applied to the elastic coupler can be detected based on the RF signal output from a receiving unit in the same manner as in the positional detection of the boundary surface in the pressurized state in which the pressurizing force is applied.

"In addition, in order to accurately perform the detection of the absolute pressure, in regard to the characteristic configuration of the second aspect of the present invention, although the elastic coupler is the same as that in the first aspect, the configuration of the pressure calculating unit is different from that in the first aspect. That is, the pressure calculating unit is characterized by detecting the displacement of the position of the boundary surface in the thickness direction of the elastic coupler based on the pair of RF signal frame data which was obtained at different timings and output from the receiving unit, obtaining the distortion of the boundary surface in the thickness direction based on the displacement, and obtaining the absolute pressure applied to the object based on the distortion in the thickness direction and the pre-set elasticity property of the elastic coupler.

"With such a configuration, it is possible to stably detect the boundary surface inside the elastic coupler regardless of the contact property between the elastic coupler and the body surface of the object, and thereby to accurately detect the distortion of the boundary surface. Accordingly, it is possible to accurately detect the absolute pressure based on the relation between the distortion and the elasticity property.

"Furthermore, in the second aspect, the pressure calculating unit can sum up the distortions of the boundary surface in the thickness direction from the initial state, in which no pressure is applied to the elastic coupler, over the passage of time and obtain the absolute pressure applied to the object based on the summed-up value of the distortion and the pre-set elasticity property of the elastic coupler. With such a configuration, since the distortions of the boundary surface in the thickness direction are summed up, it is possible to further precisely detect the distortions of the boundary surface, and thereby to further accurately detect the absolute pressure based on the relation between the distortion summed-up value and the elasticity property.

"In the first or second aspect, a configuration can be made such that the elastic coupler is formed to have a thin intermediate layer interposed between the boundary surfaces of the two layers, and the ultrasonic wave reflectance property of the intermediate layer is formed to be different from those of the other two layers. In this case, the intermediate layer can be extended in a direction perpendicular to the scanning direction of the ultrasonic beam of the ultrasonic probe and be configured by a plurality of linear ultrasonic wave reflection bodies which are spaced from each other.

"If the intermediate layer is provided in the elastic coupler, the pressure calculating unit of the first aspect can be configured so as to detect the position of the intermediate layer in the thickness direction, obtain the positional change of the intermediate layer based on the detected position of the intermediate layer and the pre-set initial position of the intermediate layer, and obtain the absolute pressure applied to the object based on the positional change and the pre-set elasticity property of the elastic coupler.

"In addition, if the intermediate layer is provided in the elastic coupler, the pressure calculating unit of the second aspect can be configured so as to detect the displacement of the position of the intermediate layer of the elastic coupler in the thickness direction based on the pair of RF signal frame data which was obtained at different timings and output from the receiving unit, obtain the distortion of the intermediate layer in the thickness direction based on the displacement, and obtain the absolute pressure applied to the object based on the distortion in the thickness direction and the pre-set elasticity property of the elastic coupler. Moreover, the pressure calculating unit of the second aspect can be configured so as to sum up the distortions of the intermediate layer in the thickness direction from the initial state in which no pressure is applied to the elastic coupler over the passage of time and obtain the absolute pressure applied to the object based on the distortion summed-up value and the pre-set elasticity property of the elastic coupler.

"Furthermore, a configuration is possible in which the elastic coupler is formed to have a two-layer structure, in which the layer on the side of the contact surface which is in contact with the body surface of the object is thinner and has a stronger ultrasonic wave reflectance property. In addition, the elastic coupler can be configured such that the ultrasonic wave attenuation property is greater by mixing ultrasonic scattering bodies into the elastic material.

"On the other hand, in order to achieve the object of simplifying the operation for detecting the absolute value with the use of an appropriate elastic coupler depending on the testing method or the like and enhancing usability, the elastic coupler of the first or second aspect is configured such that the position of the boundary surface between the two layers in the thickness direction is made to be different depending on the type of the elastic coupler and an identification code is formed with which the type of the elastic coupler can be identified with the RF signal. The pressure calculating unit in this case can be configured so as to identify the type of the elastic coupler by detecting the identification code based on the RF signal or the RF signal frame data and obtain the absolute pressure based on the elasticity property which was set to correspond to the type of the elastic coupler.

"With this configuration, it is possible to automatically identify the type of the elastic coupler in the state, in which the elastic coupler is attached to the ultrasonic probe, by the pressure calculating unit when a plurality of elastic couplers with different elasticity properties are prepared, and the elastic coupler is replaced with the one which is suitable for the appropriate measurement of the absolute pressure in accordance with the testing method, the depth of the site of interest, or the like. Accordingly, it is possible to calculate the absolute pressure in a manner matching with the elasticity property of the type of the elastic coupler if the elasticity property in accordance with the type of the elastic coupler is stored in advance in the pressure calculating unit.

"In addition, in regard to the identification code, the position of the boundary surface between the two layers in the thickness direction can be configured to differ. In such a case, the pressure calculating unit can be configured to identify the type of the elastic coupler based on the depth distribution pattern of the RF signal in a coupler echo region based on the RF signal or the RF signal frame data.

"In addition, in regard to the identification code, a configuration can be made such that the ultrasonic scattering bodies are formed while being encoded and dispersed in at least one of the scanning direction and the thickness direction in the regions on the both sides of the elastic coupler in the scanning direction. In such a case, the pressure calculating unit can be configured to identify the type of the elastic coupler from the pattern of the RF signal in the region on the both sides of the elastic coupler based on the RF signal or the RF signal frame data.

"Here, the elasticity property set in the coupler database can be at least one of an elastic modulus, a relation curve between the deformation in the thickness direction and the elastic modulus, a relation curve between the distortion in the thickness direction and the elastic modulus, a relation curve between the summed-up value of the deformation or the distortion in the thickness direction and the elastic modulus, and an elastic modulus correction coefficient with respect to the deformation or the distortion in the thickness direction.

"Advantageous Effects of Invention

"According to the present invention, it is possible to accurately detect the absolute pressure. In addition, the operation is simplified, and usability is enhanced."

URL and more information on this patent, see: Matsumura, Takeshi. Ultrasonic Diagnostic Apparatus. U.S. Patent Number 8747320, filed April 14, 2009, and published online on June 10, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8747320.PN.&OS=PN/8747320RS=PN/8747320

Keywords for this news article include: Hitachi Medical Corporation.

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Source: Journal of Engineering


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