JP2012065936A - Ultrasonograph and ultrasonic image display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonograph removing noise components of a blood flow dynamic image.SOLUTION: The good ultrasonograph having the probe 2 transmitting ultrasonic wave to and receiving the same from an object to be photographed, an image data constituting section for constituting tomographic image data, and a blood flow dynamic image constituting section 14 for constituting the blood flow dynamic image in which opacification is carried out based on the flowing time of the contrast agent considering the brightness changing qualities of the respective pixels of the tomographic image data, the evaluating section 12 for evaluating the respective pixels of the blood flow dynamic image from the brightness changing forties of the respective pixels of the tomographic image data, and the noise removing section 13 for removing the pixels corresponding to the noise components of the blood flow dynamic image based on the evaluation of the evaluating section 12.

Description

  The present invention relates to a technique for transmitting ultrasonic waves inside a living body and imaging information inside the living body based on the received signal, and in particular, efficiently detecting dynamic information of blood flow from a plurality of time-series contrast images. The present invention relates to an ultrasonic diagnostic apparatus for imaging.

  The ultrasonic diagnostic apparatus is an image display apparatus that is widely used in clinical settings together with CT and MRI, and has a feature that it is small and capable of capturing moving images. The ultrasonic diagnostic apparatus is excellent in spatial resolution and temporal resolution, and can observe fine blood flow dynamics by using a contrast agent, and has an important function in diagnosing tumor properties.

  The method described in Patent Document 1 calculates a statistical value of a value such as an average luminance value from a measured TIC (Time Intensity Curve) and displays an image color-coded according to the value. The technique described in Patent Document 2 detects the inflow time of a contrast medium for each blood vessel, and displays the relative difference as a color difference. An area of interest is set on the screen, and an image is configured with a color scheme using the inflow time in this area as a reference time.

JP 2005-81073 A JP 2010-94220 A

  Regarding the function of displaying the hemodynamic image in which the relative difference in blood flow during the inflow time of the contrast agent is shaded by the difference in color, it is disclosed that the noise component of the hemodynamic image is removed. Absent.

  The present invention provides an ultrasonic diagnostic apparatus that removes noise components from a blood flow dynamic image.

  In order to solve the problems of the present invention, attention is paid to a probe that transmits and receives ultrasonic waves to an imaging target, an image data configuration unit that configures tomographic image data, and a luminance change amount of each pixel of the tomographic image data. , An ultrasonic diagnostic apparatus comprising a blood flow dynamic image forming unit that forms a blood flow dynamic image that has been stained based on the inflow time of a contrast agent, from the amount of luminance change of each pixel of tomographic image data An evaluation unit that evaluates each pixel of the blood flow dynamic image, and a noise removal unit that removes a pixel corresponding to a noise component of the blood flow dynamic image based on the evaluation of the evaluation unit.

  In the present invention, it is possible to remove a noise component of a blood flow dynamic image obtained by applying a color difference to the relative difference in blood flow dynamics during the contrast agent inflow time.

The figure which shows the whole structure of the ultrasonic diagnosing device in this invention. The figure which shows TIC in this invention. The figure which shows the evaluation method of the evaluation part in this invention. The figure which shows the display form of the display part in this invention. The flowchart which shows the operation | movement in this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a block diagram of the ultrasonic diagnostic apparatus according to the first embodiment of the present invention. The ultrasonic diagnostic apparatus includes a probe 2 that transmits / receives ultrasonic waves to / from the imaging target 1, and a transmission beamformer 4 that gives a time delay for forming a desired transmission / reception beam to the piezoelectric elements that constitute the probe 2. Receiving beamformer 7, A / D converter 6 and D / A converter 3 for analog / digital conversion of transmission / reception signals, and TGC (Time (Gain Controller) 5, an envelope detection unit 8 that detects a received RF signal and converts it into an image signal, and a scan converter 9 that forms two-dimensional tomographic image data from the image signal. Components other than the probe 2 are referred to as an image data configuration unit.

  The ultrasonic diagnostic apparatus further includes an image memory 11 that stores tomographic image data from the scan converter 9, an evaluation unit 12 that evaluates blood flow dynamics (luminance change) from the tomographic image data, and an evaluation by the evaluation unit 12 A noise removing unit 13 that removes the noise component, and a blood flow dynamic image constructing unit 14 that constitutes the blood flow dynamic image from which the noise component has been removed. The blood flow dynamic image is an image in which a relative difference in blood flow dynamics during a contrast agent inflow time is expressed by a color difference. Specifically, the blood flow dynamic image is an image obtained by performing staining according to the inflow time difference of the contrast agent, paying attention to the luminance change of each pixel (pixel) of the tomographic image data.

  The tomographic image data refers to black and white images (B mode) and contrast agent images (images in which signals from contrast agents are emphasized by transmission / reception sequences, filter processing, etc.) commonly used in clinical settings. Is generally known. The ultrasonic irradiation surface of the probe 2 has a one-dimensional array configuration in which a plurality of piezoelectric elements are arranged in a line, and each element is responsible for transmitting and receiving ultrasonic waves. A voltage pulse from the transmission beam former 4 is input to each piezoelectric element via the D / A converter 3, and ultrasonic waves are irradiated toward the imaging target 1 by piezoelectric vibration of the element. At this time, a predetermined time delay is electronically given to each piezoelectric element, and the ultrasonic wave transmitted from each piezoelectric element is focused at a predetermined position inside the imaging target 1. The reflected echo from the imaging target 1 is received by each piezoelectric element, and the TGC 5 performs amplitude correction on the received signal according to the propagation distance. Thereafter, the reception signal is sent to the reception beam former 7 via the A / D converter 6, and the addition result is output by multiplying the delay time according to the distance from the focal position to each piezoelectric element (phased addition). .

  As a technique for emphasizing a signal from a contrast agent and imaging it, for example, there is a method of transmitting two signals whose phases are inverted and adding the received signals. While the fundamental frequency component mainly including the tissue component is suppressed by the addition of the received wave signal, the harmonic component mainly including the signal from the contrast agent is enhanced. As a result, an image in which the contrast medium is emphasized is obtained.

  The probe 2 can obtain a two-dimensional reflected echo distribution of the imaging target 1 by performing ultrasonic transmission / reception with all scanning lines along the piezoelectric element array. An RF signal divided into a real part and an imaginary part is output from the reception beamformer 7 and sent to the envelope detection unit 8. The signal sent to the envelope detection unit 8 is converted into a video signal, and then pixel interpolation between the scan lines is performed by the scan converter 9 and reconstructed into two-dimensional tomographic image data, and then the display unit 10 Is displayed.

  The operator fixes the probe 2 in a state where the imaging object 1 is captured within the imaging surface and administers a contrast medium. At the same time before or after the administration of the contrast agent, the operator presses the tomographic image data acquisition start button on the ultrasonic diagnostic apparatus, and the time-series tomography from the stage where the contrast agent flows into the imaging target 1 to the stage where it is full Image data is stored in the image memory 11. The tomographic image data in this embodiment includes RAW data.

  The surgeon designates the start and end time ranges of the tomographic image data used for the blood flow dynamic image processing while viewing the tomographic image data displayed on the display unit 10. The start time is set to a time immediately before or immediately after the contrast medium flows into the imaging target 1. The end time is appropriate when the inflow of the contrast medium into the blood vessel of interest is completed, or when the contrast of the tissue can be confirmed through angiography.

  After designating the time range of the tomographic image data, the time one second before the designated start time is automatically reset as a new start time, and the tomographic image data in that range is sent to the evaluation unit 12. The 1-second tomographic image data immediately before the start time specified by the operator is used to calculate the amount of change in luminance due to factors other than the contrast agent. The value of 1 second is preset as a time corresponding to one heartbeat, and the luminance fluctuation during this time can be regarded as a speckle pattern fluctuation mainly caused by the heartbeat. The calculated luminance change amount is always present in a TIC (Time Intensity Curve) and is a value necessary for accurately calculating the luminance change amount due to the contrast agent from the TIC. Note that the setting of 1 second can be freely changed by the operator, and is appropriately adjusted according to, for example, the heart rate of the patient. If the newly set start time exceeds the acquired tomographic image data range, 0 seconds is set as the start time.

FIG. 2 shows the TIC in the pixel (X1, Y1). In the evaluation unit 12, the maximum value I _max and the minimum value I _min in the time range from the start time to the end time (t _{start to} t _end ), the set brightness I _α set by the operator in advance, and the time when the set brightness is reached. arrival time t _alpha are calculated from the TIC for each pixel. In the evaluation unit 12, the TIC is analyzed for all the pixels of the tomographic image data, and the maximum value I _max , the minimum value I _min , the set luminance I _α , and the arrival time t _α are calculated.

The threshold luminance I _alpha is a value obtained by multiplying the coefficient alpha surgeon to the maximum value I _max is preset. The value of the coefficient α is arbitrarily determined by the operator, but when the inflow start time of the contrast medium is used as a mapping parameter, it is necessary to capture the blood flow dynamics of the inflow of the contrast medium in the TIC. In order to capture the blood flow dynamics of inflow of contrast medium in TIC, the coefficient α is empirically about 0.5 to 0.8.

Next, the evaluation unit 12 calculates a luminance change amount ΔI (I _α −I _min ) due to the contrast agent for each pixel. The inflow of contrast agent is mainly blood vessels. The luminance change amount ΔI in the blood vessel is relatively large. Therefore, a pixel having a relatively large luminance change amount ΔI is an image display component. On the other hand, when the luminance change amount ΔI is small, it can be regarded as a noise component due to body movement, pulsation or the like. Here, when the luminance change amount ΔI of the pixel of the tomographic image data is smaller than the noise removal threshold N, the evaluation unit 12 evaluates the pixel of the tomographic image data as a noise component, and the luminance change amount ΔI of the pixel of the tomographic image data is If it is larger than the noise removal threshold N, the pixels of the tomographic image data are evaluated as image display components.

  The evaluation method of the evaluation unit 12 is shown in FIG. The pixel (X1, Y1) in FIG. 3 (a) is an image display component because the luminance change amount ΔI is larger than the noise removal threshold value N. The pixel (X2, Y2) in FIG. 3B is a noise component because the luminance change amount ΔI is smaller than the noise removal threshold N. As described above, the evaluation unit 12 compares the luminance change amount ΔI and the noise removal threshold N in each pixel (all pixels) of the tomographic image data, and evaluates the image display component and the noise component. Note that the surgeon can arbitrarily set the noise removal threshold N for the evaluation unit 12.

The blood flow dynamic image constructing unit 14 generates tomographic image data that is stained according to the contrast agent inflow time difference based on the change in luminance of each pixel of the tomographic image data, and constructs the blood flow dynamic image . The blood flow dynamic image construction unit 14 performs a shadowing process on the pixels evaluated as the image display component to construct a blood flow dynamic image. The dyeing process is a process of coloring each frame after the frame where the coloring starts (dyeing start frame). Opacification start frame is a frame corresponding to the luminance arrival time t _alpha. This is specified from the luminance arrival time tα and the frame rate of the tomographic image data. And the process which colors the said pixel of the frame after the dyeing | staining start frame of tomographic image data to be analyzed is performed. The coloring, in association with the segment luminance arrival time t _alpha is the case, using a display color specified by the color to be recorded in a predetermined color chart.

  The blood flow dynamic image constructing unit 14 converts the pixel evaluated as a noise component to 0 as a non-contrast part, and is not colored as described above. That is, a blood flow dynamic image is not created for a pixel evaluated as a noise component.

  FIG. 4 shows a display form of the display unit 10. The display unit 10 displays a morphological image 40 based on two-dimensional tomographic image data. The region 42 is a pixel region evaluated as an image display component of the blood flow dynamic image. A region 44 is a pixel region evaluated as a noise component of the blood flow dynamic image.

  FIG. 4 (a) shows a display form of the display unit 10 to which the present invention is not applied. The display unit 10 displays a pixel region 42 evaluated as an image display component of a blood flow dynamic image and a pixel region 44 evaluated as a noise component of the blood flow dynamic image. Since the region 44 is not a blood vessel, it can be confirmed that it is a noise component.

  FIG. 4 (b) shows a display form of the display unit 10 to which the present invention is applied. The display unit 10 displays only the pixel region 42 evaluated as the image display component of the blood flow dynamic image. The pixel region 44 evaluated as a noise component of the blood flow dynamic image could be removed.

  Next, the operation procedure in the present embodiment will be described with reference to FIG.

  (S10) The surgeon arbitrarily sets the noise removal threshold N for the evaluation unit 12.

  (S11) The evaluation unit 12 calculates the luminance change amount ΔI due to the contrast agent for each pixel (all pixels).

  (S12) If the luminance change amount ΔI is smaller than the noise removal threshold N, the evaluation unit 12 evaluates it as a noise component, and if the luminance change amount ΔI is larger than the noise removal threshold N, evaluates it as an image display component.

  (S13) The blood flow dynamic image construction unit 14 converts the pixel evaluated as a noise component to 0 as a non-contrast part, is not colored, and does not create a blood flow dynamic image.

  (S14) The blood flow dynamic image construction unit 14 performs a shadowing process on the pixels evaluated as the image display component to construct a blood flow dynamic image. On the display unit 10, only the pixel region evaluated as the image display component of the blood flow dynamic image is displayed.

  As described above, according to the present embodiment, attention is paid to the probe 2 that transmits and receives ultrasonic waves to the imaging target, the image data configuration unit that configures the tomographic image data, and the luminance change amount of each pixel of the tomographic image data. , An ultrasonic diagnostic apparatus comprising a blood flow dynamic image forming unit 14 that forms a blood flow dynamic image that has been stained based on a contrast agent inflow time, and a luminance change amount of each pixel of tomographic image data Are provided with an evaluation unit 12 that evaluates each pixel of the blood flow dynamic image and a noise removal unit 13 that removes a pixel corresponding to a noise component of the blood flow dynamic image based on the evaluation of the evaluation unit 12. Therefore, the noise component of the blood flow dynamic image can be removed.

  Example 2 will be described. The evaluation unit 12 sets the noise removal threshold N based on the luminance change amount ΔI of all pixels of the tomographic image data.

  Specifically, the evaluation unit 12 sets the noise removal threshold N so that a luminance change amount ΔI of a predetermined ratio or more among the luminance change amounts ΔI of all pixels of the tomographic image data becomes an image display component.

  A blood flow dynamic image is an image of a contrast agent in a blood vessel and is equal to or less than a desired ratio of the entire image. Therefore, for example, the evaluation unit 12 sets the noise removal threshold value N so that the luminance change amount ΔI of the upper 20% becomes an image display component. That is, 20% of the entire image is calculated as the image display component of the blood flow dynamic image.

  In the above description, the noise removal threshold value N is set so that the luminance change amount ΔI of the top 20% becomes an image display component. However, the surgeon arbitrarily sets a predetermined ratio for the evaluation unit 12. Can do.

  As described above, according to this embodiment, an appropriate noise removal threshold N can be automatically set.

  Example 3 will be described. The blood flow dynamic image construction unit 14 is a point that removes the frame of the blood flow dynamic image based on the distribution of the noise component or the image display component of the blood flow dynamic image.

  The blood flow dynamic image configuration unit 14 determines whether the pixel area evaluated as the noise component of the blood flow dynamic image is equal to or larger than the predetermined area of the entire image, or the pixel area evaluated as the image display component of the blood flow dynamic image If the total area is equal to or smaller than the predetermined area, the frame of the blood flow dynamic image is removed because it is not worth displaying the blood flow dynamic image. That is, the blood flow dynamic image is not displayed on the display unit 10.

  Specifically, the hemodynamic image construction unit 14 determines whether the pixel evaluated as the noise component of the hemodynamic image is an area of, for example, 95% or more of the entire image, or the image display component of the hemodynamic image. If the evaluated pixel has an area of, for example, 5% or less of the entire image, the frame of the hemodynamic image is removed.

  In addition, if the area of the pixel block (connection) evaluated as the image display component of the hemodynamic image is less than or equal to the predetermined area, it is not worth displaying the hemodynamic image and the frame of the hemodynamic image is displayed. It may be removed.

  The surgeon can arbitrarily set a predetermined area in the noise component of the blood flow dynamic image or a predetermined area in the image display component of the blood flow dynamic image with respect to the blood flow dynamic image configuration unit 14.

  As described above, according to the present embodiment, it is possible to efficiently display a blood flow dynamic image having a luminance change amount by a contrast agent.

  1 Subject, 2 Probe, 3 D / A converter, 4 Transmit beamformer, 5 TGC, 6 A / D converter, 7 Receive beamformer, 8 Envelope detector, 9 Scan converter, 10 Display, 11 Image memory, 12 evaluation unit, 13 noise removal unit, 14 image composition unit

Claims (6)

Focusing on the probe that transmits and receives ultrasound to and from the imaging target, the image data configuration unit that constitutes the tomographic image data, and the luminance change amount of each pixel of the tomographic image data, based on the inflow time of the contrast agent An ultrasonic diagnostic apparatus comprising a blood flow dynamic image configuration unit that configures a blood flow dynamic image subjected to staining,
An evaluation unit that evaluates each pixel of the blood flow dynamic image from a luminance change amount of each pixel of the tomographic image data, and a pixel that corresponds to a noise component of the blood flow dynamic image is removed based on the evaluation of the evaluation unit An ultrasonic diagnostic apparatus comprising a noise removing unit.   2. The blood flow dynamic image forming unit forms a blood flow dynamic image in which a relative difference in blood flow dynamics during a contrast agent inflow time is shaded by a color difference. Ultrasonic diagnostic equipment.   The ultrasonic diagnostic apparatus according to claim 1, wherein the evaluation unit evaluates a noise component when a luminance change amount of each pixel of the tomographic image data is smaller than a noise removal threshold.   The ultrasonic diagnostic apparatus according to claim 3, wherein the evaluation unit sets the noise removal threshold based on a luminance change amount of all pixels of the tomographic image data.   The ultrasonic diagnostic apparatus according to claim 1, wherein the blood flow dynamic image configuration unit removes a frame of the blood flow dynamic image based on a distribution of a noise component or an image display component of the blood flow dynamic image. .   A step of constructing tomographic image data by transmitting and receiving ultrasonic waves to and from an imaging target; a step of evaluating blood flow dynamics from the tomographic image data; a step of removing noise components based on the evaluation; And a step of constructing the removed blood flow dynamic image.

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