JP4796468B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus that forms a three-dimensional ultrasonic image.

  When performing hemodialysis, blood vessels in the forearm are often used to remove blood from the dialysis patient's body and return it to the body. If hemodialysis is continued for a long time, blood vessels in the forearm may hurt and stenosis may occur.

  In order to treat a blood vessel having a narrowed inner diameter due to stenosis, a treatment is performed to expand the inner diameter of the blood vessel by inserting a balloon or a stent into the blood vessel. When performing this treatment, it is necessary to insert the distal end of the catheter from the outside of the body (for example, the elbow or the base of the foot) into a blood vessel in the body, move the distal end of the catheter to the position of the narrowed blood vessel, and perform positioning. . Conventionally, a diagnostic method using an X-ray imaging apparatus has been used to confirm the position and route of the distal end of the catheter. However, since there is a problem of exposure when X-rays are used, it has been studied to apply an ultrasonic diagnostic apparatus having little influence on a living body.

  Patent Document 1 describes an image forming technique based on a volume rendering method using ultrasonic waves, for example, in order to diagnose a blood vessel in the forearm with the forearm as a diagnosis target. Patent Document 2 discloses a medical device that can observe the position of a catheter inserted into a blood vessel. In this medical apparatus, in order to obtain a three-dimensional image, projection images from two directions of the subject are formed using two X-ray imaging apparatuses and the like. Patent Document 3 describes a surgical support method for forming a three-dimensional image of a catheter to be inserted into a blood vessel. In this method, the user manually sets the shape and initial position of the surgical instrument, and then a three-dimensional image inside the blood vessel is formed.

JP 2002-336253 A JP 2002-119507 A Japanese Patent Laid-Open No. 10-334220

  In order to acquire a three-dimensional image using an ultrasonic diagnostic apparatus, a stereoscopic projection image of a blood vessel can be obtained by using the apparatus described in Patent Document 1. In order to display a blood vessel image clearly, an appropriate rendering condition is set for the blood vessel. When rendering conditions are optimized for a blood vessel as a display target, it is difficult to image the device even if some device exists inside the blood vessel.

  On the other hand, if the purpose is only to image an instrument in a blood vessel, imaging can be performed by uniformly changing the setting of opacity (opacity) that is a rendering parameter. Since a device such as a catheter is generally a highly reflective material, a high level echo signal can be obtained. However, if the device is clearly imaged by uniformly changing the opacity parameter, it becomes difficult to image the blood vessel this time.

  If the state of the device in the blood vessel can be imaged, the position of the blood vessel to be treated and the device can be grasped, but the opacity parameter is adjusted using a conventional ultrasonic diagnostic apparatus. However, the blood vessel and the instrument inserted into the blood vessel could not be clearly visualized simultaneously.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of visualizing both blood vessels and instruments simultaneously as clear three-dimensional images.

  The present invention provides an ultrasonic diagnostic apparatus that sequentially executes voxel operations in the depth direction for each ray set for a voxel data group obtained by transmitting and receiving ultrasonic waves to a blood vessel in which an instrument is inserted. For each ray, a first rendering means for obtaining a pixel value constituting the first three-dimensional image based on a result of sequential execution of the voxel calculation from a first start point; and a determination means for determining a second start point for each ray And a pixel constituting the second three-dimensional image in which the instrument is reflected by the result of sequential execution of the voxel calculation from the second start point for the ray in which the second start point is determined among a plurality of rays Second rendering means for obtaining a value; synthesis processing means for synthesizing the first 3D image and the second 3D image to form a synthesized 3D image; and a display for displaying the synthesized 3D image And having a, the.

  According to the above configuration, each pixel value is obtained by sequentially executing the voxel calculation from the first start point on each ray set for the voxel data group. That is, each pixel value is obtained by the first rendering process, and a first three-dimensional image is formed. In addition, when the second start point is determined on each ray set for the voxel data group, the second three-dimensional image is formed on the data on the ray on the back side from the second start point. The second rendering process for is performed.

  Depending on the first rendering means, it is possible to form a first three-dimensional image. Depending on the second rendering means, a plurality of voxel data after determining the second start point can be used to insert the instrument inserted into the blood vessel. The reflected second 3D image can be formed. That is, when the second start point exists, two images of the first three-dimensional image and the second three-dimensional image are formed to form a composite three-dimensional image. Each of the devices inserted into the blood vessel can be clearly formed into a three-dimensional image.

  As a method for determining the second start point, various methods can be applied as long as the images of the tissue and the instrument can be clearly displayed. That is, in the present invention, the stepwise switching of rendering is one of the features, and the switching condition may be appropriately determined according to various uses.

  Note that a ray may be set from an arbitrary viewpoint position in the three-dimensional space, and the ray and the ultrasonic beam may be in the same direction. As the voxel calculation, a transmitted light amount calculation by a volume rendering method using opacity (opacity) may be performed, or another calculation for three-dimensional image configuration may be used.

  Preferably, the determination means determines a depth position in the blood vessel and on the near side of the instrument as the second start point. According to the above configuration, the second rendering process for the intravascular device can be performed by setting the second start point on the near side of the device in the direction of each ray.

  Preferably, the determination means determines the second start point based on a sequential execution result of the voxel calculation from the first start point for each ray. According to the above configuration, on each ray set for the voxel data group, the second start point is set by satisfying a predetermined condition from the sequential execution result of the voxel calculation from the first start point. Since the volume rendering calculation conditions for performing the voxel calculation can be changed, for example, the rendering process can be ended at the position of the blood vessel to be visualized, and the end point can be set as the second start point.

  Preferably, the determination means determines the second start point based on a sequential execution result of the voxel calculation from the first start point for each ray. According to the above configuration, since the determination of the second start point is performed based on the values sequentially calculated by the voxel calculation, the second start point reflecting the ultrasonic echo intensity, that is, the state inside the living tissue. Judgment can be made.

  Preferably, the determination means determines the second start point based on an integrated value of parameters used in a voxel calculation from the first start point that is sequentially executed for each ray. . According to the above configuration, since the determination of the second start point is performed based on the integrated value of the parameter used in the voxel calculation, it is possible to select a flexible second adaptable to the state of the living tissue according to the value set in the parameter. Two starting points can be set. Here, as parameters, for example, values indicating opacity and transparency can be used.

  Preferably, the image processing apparatus includes pre-processing means for performing luminance inversion processing on the voxel data string on each ray, and at least one of the determination means, the first rendering means, and the second rendering means is the luminance inversion. The processing is executed based on the processed voxel data string.

  According to the above configuration, the voxel data sequence that has been subjected to the luminance inversion processing is the processing target. By reversing the received signal intensity of the ultrasonic wave and performing image formation processing, and displaying the synthesized three-dimensional image on the display means, the low level signal is replaced as a high level signal, and the original high level signal is reversed. The level signal is replaced as a low level signal. Therefore, by treating the low level echo signal obtained from the blood as a high level echo signal, it is possible to perform signal processing on the portion where the blood flows.

  Furthermore, in general, a high level signal is often obtained from an instrument, but a high level signal can be similarly obtained for an instrument inserted into a blood vessel. Therefore, the signal processing is such that the instrument is emphasized with a normal signal treatment. However, it is also possible to perform a process that does not emphasize the appliance by performing the luminance inversion processing on the voxel data string mainly including the appliance. As described above, by arbitrarily selecting a signal to be inverted and a signal not to be inverted, it becomes possible to select and process a portion to be emphasized or a portion not to be emphasized when displaying a three-dimensional image. .

  Desirably, a color Doppler processing means is further provided for performing quadrature detection on a reception signal obtained by transmitting and receiving ultrasonic waves and detecting a position of blood flow in accordance with a Doppler shift frequency component generated along with blood movement. And the determination means determines the second start point based on blood flow position information detected by the color Doppler processing means. According to the above configuration, since the position of the blood can be detected according to the Doppler shift frequency generated when the blood moves in the living body, the second portion is surely present in the portion where the blood flow exists. A second starting point for rendering can be defined.

  Preferably, the synthesis processing unit forms the synthesized 3D image by superimposing a second 3D image mainly representing the instrument on the first 3D image mainly representing the blood vessel. It is characterized by that. According to the above configuration, even if the first three-dimensional image and the second three-dimensional image are combined to form a three-dimensional image, the image information of the original first three-dimensional image and the second three-dimensional image is visually displayed. Can be identified. Since the first 3D image is an image mainly composed of a living tissue and the second 3D image is an image mainly composed of an instrument, the position of the instrument can be clearly grasped even in the synthesized 3D image.

  Preferably, the synthesis processing means performs the synthesis process while visually differentiating the first 3D image and the second 3D image. According to the above configuration, the first three-dimensional image and the second three-dimensional image can be easily identified. Examples of the synthesizing process that is visually different include coloring display, blinking display that changes the luminance, and outline emphasis display.

  As described above, according to the present invention, both blood vessels and instruments can be visualized simultaneously as clear three-dimensional images.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a state in which an ultrasonic transmitter / receiver is in contact with a forearm portion 10 of a human body. In the present embodiment, a dialysis patient undergoing hemodialysis is a target of ultrasonic diagnosis, and an example is a case where a device 16 is inserted into a blood vessel 14 in which a stenosis occurs in the forearm 10 and treatment is performed. explain.

  This instrument 16 is a surgical instrument inserted into the blood vessel 14, and specifically shows a catheter. The probe body 12 is an electronic scanning ultrasonic probe having an array transducer (not shown), and a water bag 18 is mounted on the wave transmitting / receiving surface side of the probe body 12. The probe main body 12 is held by a mechanical scanning mechanism 22 (not shown) described later, and the mechanical scanning mechanism 22 is configured as a probe unit 30 by combining the probe main body 12 and the water bag 18. Is done.

  FIG. 2 is a block diagram showing a schematic overall configuration of the ultrasonic diagnostic apparatus according to the present invention. The ultrasonic diagnostic apparatus in the present embodiment is roughly composed of a probe unit 30 and an apparatus main body 40. First, the probe unit 30 will be described in detail. The probe unit 30 includes a movable part 20 and a mechanical scanning mechanism 22. The movable part 20 is composed of the probe main body 12 and the water bag 18 as described above. As the electronic scanning method of the probe body 12, an electronic linear scanning method is used in this embodiment. An electronic sector scanning method or other electronic scanning methods may be used. The outer surface of the water bag 18 is formed of a flexible film-like member, and the inside thereof is filled with, for example, distilled water.

  When the probe main body 12 is brought into contact with the forearm 10, the water bag 18 is flexibly deformed in conformity with the curved shape of the forearm 10, and ultrasonic waves transmitted from the array transducer are transmitted to and received from the forearm 10. An ultrasonic transmission path is formed. In the present embodiment, one echo data string is acquired according to the formation of one ultrasonic beam. The echo data string is output from the probe unit 30 to the apparatus main body 40 side. By scanning the ultrasonic beam electronically, the scanning surface 19 (see FIG. 1) is formed in a direction perpendicular to the longitudinal direction of the forearm. By acquiring the echo data array on the scanning plane in the apparatus main body 40, two-dimensional tomographic information on one scanning plane can be obtained.

  The mechanical scanning mechanism 22 is a mechanism that performs positioning scanning based on a signal from the mechanical scanning control unit 24. A scanning surface is formed by electronic scanning of the probe main body 12, and the mechanical scanning mechanism 22 mechanically scans the movable portion 20 in a direction orthogonal to the scanning surface. In the present embodiment, the movable portion 20 is moved along the longitudinal direction of the arm by the mechanical scanning mechanism 22 while keeping the water bag 18 in contact with the forearm portion 10. Then, a plurality of scanning planes parallel to each other in the longitudinal direction of the forearm are sequentially formed. By moving the movable unit 20 in the longitudinal direction of the forearm, it is possible to acquire an echo data group including a plurality of echo data arrays, and three-dimensional spatial information inside the forearm 10 can be obtained.

  Next, the configuration of the apparatus main body 40 will be described. The apparatus main body 40 includes an input unit 42 including a keyboard and a trackball. The input unit 42 has a numerical value input function for performing condition setting and parameter setting necessary for forming a three-dimensional ultrasonic image, or color adjustment of the three-dimensional ultrasonic image. The input content of the input unit 42 is read by the main control unit 44, and the main control unit 44 controls the operation of the entire apparatus. The mechanical scanning control unit 24 whose operation is controlled by the main control unit 44 outputs a signal for controlling the movable unit 20 to the mechanical scanning mechanism 22.

  The transmission / reception unit 46 has a transmission beamforming function and a reception beamforming function. That is, the transmission / reception unit 46 has a transmission beam forming function for forming an ultrasonic beam by setting a delay time for each vibration element constituting the array transducer, and adjusting the signal reception timing of the reception signal. In addition, it has a reception beam forming function including a phasing addition function for matching the phases of a plurality of reception signals. The transmission / reception unit 46 includes a signal processing circuit such as a dynamic range conversion circuit that corrects the intensity of the reception signal. The echo data string output from the transmission / reception unit 46 is transmitted to the three-dimensional image processing unit 48. Incidentally, the echo data string output from the transmission / reception unit 46 may be output to the color Doppler processing unit (not shown) simultaneously with the output to the three-dimensional image processing unit 48.

  The three-dimensional image processing unit 48 has a function of forming a plurality of three-dimensional images. In the present embodiment, the inversion processing unit 50, the first rendering start point determination unit 52, the first rendering processing unit 54, and the second A rendering start point determination unit 56 and a second rendering processing unit 58 are provided. Incidentally, in this embodiment, the ray that is the line of sight of volume rendering is set in the same direction as the traveling direction of the ultrasonic beam. Therefore, the echo data string input to the three-dimensional image processing unit 48 can be processed as it is as a voxel data string that is a target of voxel calculation.

  The inversion processing unit 50 has a function of inverting the luminance of input data and outputting it. In the inversion processing unit 50, the signal level of each echo data constituting the echo data string is inverted and converted. When this inversion is performed, the low level echo data is replaced with high level echo data. Therefore, the inversion processing unit 50 is a means for facilitating detection of an echo signal from a blood flowing portion in a biological tissue having a low reflection intensity with respect to ultrasonic waves, that is, in the forearm.

  The first rendering start point determination unit 52 has a function of determining the first start point of the voxel calculation performed by the first rendering processing unit 54. For the determination of the first start point, an inverted echo data string output from the inversion processing unit 50 is used. The determination condition of the first start point is determined by using, for example, ROI region setting performed by the operator of the ultrasonic diagnostic apparatus operating the input unit 42. Incidentally, as a determination condition of the first start point, a method of detecting a boundary surface between the subject surface and the coupling body described in JP-A-2002-336253 can be used.

  The first rendering processing unit 54 performs sequential calculation of voxel calculation with the first start point determined by the first rendering start point determination unit 52 described above as the starting point of signal processing. It has a function for obtaining a pixel value. For the voxel calculation, for example, a known voxel calculation method described in JP-A-10-33538 can be used.

  As an example of the voxel calculation method, by adding the light emission amount represented by the product of the opacity of the voxel and the echo value, and the attenuation light amount represented by the product of the transparency of the voxel and the input light of the voxel. An operation for obtaining an output light amount from the voxel is given. Since the input light amount to the voxel is the same value as the output light amount of the previous voxel adjacent to the voxel, the luminance value of the pixel in the ray direction can be obtained by performing sequential calculation. However, when the calculation target voxel reaches the last voxel on the ray or the opacity integrated value of a plurality of voxels on the ray becomes 1, an end condition is added to end the sequential calculation.

  The second rendering start point determination unit 56 has a function of determining the second start point of the voxel calculation performed by the second rendering processing unit 58. In the present embodiment, the result of sequential execution of voxel calculations performed by the first rendering processing unit 54 is used to determine the second start point. That is, when the value of the transmitted light amount by the voxel calculation performed in the first rendering processing unit 54 exceeds a predetermined threshold, the echo data that is the calculation target of the voxel calculation is set as the second start point.

  The ultrasound diagnostic apparatus according to the present embodiment is characterized by executing the second rendering process based on the result of the first rendering process, and the second rendering process starts from the second starting point. Is done. The second start point is a restart point or a reset point of the rendering process for acquiring the second 3D image mainly including the instrument. In order to form a second 3D image depicting the device inserted into the blood vessel, it is necessary to set a second starting point at the portion of the blood vessel wall, more preferably at the portion of the blood flow that flows in the blood vessel. There is.

  Using the physical phenomenon that the echo intensity of each of the blood vessel wall and blood changes greatly, the position that enters the inside of the blood vessel can be detected as the second starting point. Changing the rendering process that forms the ultrasound image from the second starting point, which is the position that has entered the inside of the blood vessel, is a very effective method for visualizing foreign substances other than blood existing in the blood vessel. In particular, in the case of three-dimensional imaging, it is effective for recognizing the position of the instrument in the three-dimensional space.

  For the determination method of the second start point, in addition to the method using the fact that the value of the transmitted light amount exceeds the predetermined threshold as described above, some other determination methods can be used.

  As another determination method of the second start point, for example, an opacity integration calculation that is executed in parallel with the sequential calculation of the voxel calculation can be used. That is, when the integrated value of opacity by the voxel calculation exceeds a predetermined threshold, the echo data that is the calculation target of the voxel calculation can be set as the second start point.

  Further, as another determination method of the second starting point, the same method as the method of detecting the boundary surface between the subject surface and the coupling body described in the aforementioned Japanese Patent Application Laid-Open No. 2002-336253 is used. Thus, the second starting point can be determined. The similar method is that the region of interest is set in advance at a position that does not include the subject surface, the data in the region of interest that does not include the subject surface is inverted in luminance, and then the first rendering processing unit 54 It is a technique to process. When N pieces of high-intensity inverted echo data continue (for example, five), the N-th echo data can be set as the second start point.

  Furthermore, as another determination method of the second start point, a differential value of a continuous data string can be used. That is, when image reconstruction is performed by voxel calculation, differentiation is performed on a plurality of data that are constituent elements of a continuous data sequence along the ray direction, and the position corresponding to data in which the differential value changes rapidly Can be the second starting point.

  The second starting point can be detected using any one of the several detection methods described above.

  The second rendering processing unit 58 has a function of obtaining a pixel value of a three-dimensional image on a certain ray by performing sequential calculation of voxel calculation from the second start point determined by the second rendering start point determination unit 56 described above. Have. The second rendering processing unit 58 receives the echo data as it is before being inverted. The voxel operation performed by the second rendering processing unit 58 may be the same method as the voxel operation performed by the first rendering processing unit 54, or may be a 3D image construction operation different from the voxel operation. .

  Next, the 3D image composition unit 60 will be described. The three-dimensional image composition unit 60 has a function of superposing two types of three-dimensional images to form one composite three-dimensional image. The three-dimensional image composition unit 60 includes a first three-dimensional image memory 62, a second three-dimensional image memory 64, and the like. The first 3D image memory 62 is a memory that stores a first 3D image configured by mapping a plurality of pixel values obtained by the first rendering processing unit 54. The second 3D image memory 64 is a memory that stores a second 3D image configured by mapping a plurality of pixel values obtained by the second rendering processing unit 58. By synthesizing the first 3D image and the second 3D image in these memories, one synthesized 3D image is formed.

  The display unit 68 is composed of a CRT or LCD, and displays the synthesized 3D image so that the operator can observe it.

  FIG. 3 is an explanatory diagram relating to each calculation process of the first and second rendering processes performed by the 3D image processing unit 48. FIG. 3 schematically shows a three-dimensional image capturing area obtained by bringing the movable portion 20 into contact with the forearm portion 10.

  A plurality of scanning planes parallel to each other are formed by moving the movable portion 20. On the foremost scanning plane 70, a cross section of the blood vessel 14 and the instrument 16 inserted into the blood vessel are included. In addition, a setting range of a region of interest (ROI) 80 for forming a three-dimensional image centered on the blood vessel 14 is shown on the scanning plane 70. In addition, a boundary portion 82 where the body surface of the forearm portion 10 and the water bag 18 come into contact with each other is shown in a portion close to the movable portion 20 on the scanning surface 70. Incidentally, the set shape of the ROI 80 is a three-dimensional rectangular parallelepiped shape that extends in the Y-axis direction.

  In FIG. 3, the voxel data string acquired in accordance with one ultrasonic beam is represented as one straight line parallel to the Z axis on the scanning plane. For example, the voxel data string A72 is a voxel data string acquired at a position where the blood vessel 14 does not exist.

  The first start point of the voxel data string A72 is determined in relation to the setting area of the ROI 80. The position of the first start point can be determined as a point P1 where the straight line indicating the voxel data string A72 and the upper end surface of the ROI 80 intersect on the scanning plane 70 shown in FIG.

  The voxel calculation for the voxel data string A72 is performed on a data string in a range from the position of the point P1 that is the first start point to the point P2 that intersects the lower end surface of the ROI 80. In the middle of executing the voxel calculation cumulatively, if the calculation end condition is satisfied, the calculation is stopped, and the calculation result at that time becomes the pixel value related to the voxel data string A72. Or, even when the point P2 on the lower end surface of the ROI 80 is reached, if the calculation end condition is not satisfied to the end, the calculation result in the last voxel becomes the pixel value. That is, in performing the first rendering process, one pixel value is obtained for one voxel data string regardless of whether or not the calculation end condition is satisfied. The pixel value is the beam-corresponding pixel value A (86) shown in FIG. If a point that satisfies the determination condition for the second start point is detected during the execution of the first rendering process, the process switches to the second rendering process, but the voxel data string A72 has no blood vessel. Since it is a voxel data string acquired in a part, the second starting point is not detected.

  Next, calculation processing related to the voxel data string B88 acquired at a position where the blood vessel 14 and the instrument 16 exist will be described. In the voxel data string B88, the first start point is determined in relation to the setting area of the ROI 80, similarly to the above-described voxel data string A72. The position of the first start point can be determined as a point P3 where the straight line indicating the voxel data string B88 and the upper end surface of the ROI 80 intersect on the scanning plane 70 shown in FIG. The first rendering process is performed on the voxel data string B88 after the determination of the first start point P3.

  When the first rendering process is executed in sequence, the calculation of the voxel data at the position inside the blood vessel 14 is performed. Although weak echo data is obtained from blood, it is converted into high echo data by inversion processing. Therefore, a point satisfying this condition is determined using a determination condition that the output light amount value of the first rendering process exceeds a certain threshold value. It should be noted that the first rendering process can be stopped when the determination condition that the output light amount value of the first rendering process exceeds a certain threshold is satisfied. In this case, the first end point P4 that is the end point of the first rendering process is the same point as the second start point P5 described above. The beam corresponding pixel value B1 (90) shown in FIG. 3 is obtained by performing the first rendering process on the voxel data between the first start point P3 and the first end point P4.

  Next, a second start point P5 that is a start point of the second rendering process is set based on the first end point P4 of the first rendering process. The second start point P5 is set at a position inside the blood vessel 14. The second rendering process is executed in accordance with the setting of the second start point P5. In the second rendering process, the non-inverted voxel data string B88 is the target of the calculation process. The second rendering process is a process for imaging an instrument in a blood vessel. For instrument imaging, rendering parameters are set to high-level echo data reflecting the instrument.

  When the second rendering process is sequentially executed, a strong level of echo data is detected from the surface of the instrument 16. A position on the voxel data string B88 and intersecting the surface of the instrument 16 can be set as the end point P6 of the second rendering process. The beam corresponding pixel value B2 (92) shown in FIG. 3 is obtained by performing the second rendering process on the voxel data between the second start point P5 and the second end point P6.

  In general, since a high-level echo signal is obtained from the surface of the instrument, the second rendering process can be set to end on the surface of the instrument 16. However, depending on the volume rendering parameter setting, the calculation of voxel data existing in the depth direction can be accumulated.

  As described above, the beam-corresponding pixel value A (86) and the beam-corresponding pixel value B1 (90) are obtained in the first rendering process by performing the two-stage rendering process. Then, the beam-corresponding pixel value B2 (92) is obtained by the second rendering process. The first three-dimensional image 94 is formed by performing the first rendering process not only on the two illustrated voxel data strings A72 and the voxel data string B88 but also on all the voxel data strings existing in the ROI 80. In addition, a second rendering process is performed on the voxel data sequence for which the second start point has been determined, whereby a second three-dimensional image 96 is formed.

  The first three-dimensional image 94 is formed based on a voxel data sequence corresponding to a living tissue in which no blood vessel exists and a voxel data sequence corresponding to a living tissue in front of the blood vessel in a portion where the blood vessel exists. That is, the first three-dimensional image 94 does not include information inside the blood vessel, and is a three-dimensional projection image that mainly represents the living tissue. The second three-dimensional image 96 is formed based on a voxel data string corresponding to a blood vessel or a living tissue located on the back side of the blood vessel. Therefore, the instrument projection portion 98 can be recognized in the second three-dimensional image 96.

  FIG. 4 is a diagram showing the areas to which the first rendering process and the second rendering process are applied in the scanning plane 70 shown in FIG. FIG. 4 shows only the region of the ROI 80 in the scanning plane 70 shown in FIG.

  At the upper end of the ROI 80, a first start point group 162 at which the first rendering process is started is shown as a straight line. The aforementioned point P3 also exists on the first start point group 162. Further, the first end point group (164A, 164B) is shown as two line segments at the lower end of the ROI 80. Since the rendering condition is set so that the first rendering process ends in the blood vessel in the portion where the blood vessel 14 exists, the first end point group 166 for the blood vessel has an arc shape corresponding to the shape of the blood vessel wall. Since the region where the first rendering process is performed is a region sandwiched between the first start point group 162 and the first end point group (164A, 164B, 166), the reverse concave hatched region illustrated in FIG. 160.

  In the present embodiment, the second rendering process is executed on the voxel data string obtained from the position where the blood vessel exists. Therefore, the first end point group 166 in the blood vessel becomes the second start point group 168. Since the second rendering process starts from the second start point group 168 along the depth direction of the ray 170, the area to which the second rendering process is performed is a hatched area 172 illustrated in FIG. Incidentally, the second rendering process can be stopped at the position of the surface of the instrument 16.

  FIG. 5 is a diagram in which various signals generated by performing signal processing on one echo data string are arranged. FIG. 5A shown at the top of FIG. 5 shows the intensity level of the echo data string. The horizontal axis of Fig.5 (a) is a time axis, and a vertical axis | shaft shows the intensity level of echo data. This echo data string represents an echo data string obtained by transmitting one ultrasonic beam toward an instrument existing in a blood vessel. The voxel data string B88 shown in FIG. 3 corresponds to this echo data string.

  The echo data string 100 has a level that suddenly drops (104a, 104b) or temporarily shows a peak (106) in an intermediate portion 102 of the data string. The level drops sharply because the echo data of this part reflects the low echo intensity in the blood vessel, and the level temporarily shows a peak because the echo data of this peak part is This is because the echo intensity by the instrument is reflected. The echo data that is not included in the intermediate portion 102 and spreads back and forth on the time axis is echo data obtained by living tissue.

  FIG. 5B is a graph showing an inverted echo data sequence 108 obtained by inverting the echo data sequence 100. The definitions of the horizontal and vertical axes in FIG. 5B are the same as those in FIG. By performing the inversion process, the low level portions (104a, 104b) in the echo data string 100 are converted into high level data.

  Here, the explanation of FIG. 5 is temporarily separated, and an example of the echo data inversion processing characteristic is shown using FIG. FIG. 6 is a diagram illustrating an example of echo data inversion processing characteristics. The horizontal axis represents the echo signal input level, and the vertical axis represents the echo signal output level. When the conversion process according to the curve 124 is performed, a low level input signal is converted as a high level output signal, and conversely, a high level input signal is converted as a low level output signal. Since the graph shows non-linear characteristics, the lower the level of the input signal, the higher the inverted signal that is emphasized. An input signal that exceeds a certain threshold also has a cutoff characteristic that is not converted as an output signal.

  Returning to FIG. 5, the signal processing of the inverted echo data sequence 108 will be described. In the ultrasonic diagnostic apparatus according to the present embodiment, the first rendering process is performed on the inverted echo data sequence 108. As the first rendering processing unit 54 executes the voxel calculation, an output light amount value from each voxel data is obtained, and an opacity integrated value is also obtained at the same time.

FIG. 5C shows a cumulative change of the integrated opacity value (Σαi) by the first rendering process, and FIG. 5D shows a cumulative change of the output light amount value (C1out) by the first rendering process. ing. In the present embodiment, the second rendering process is started when the value of the output light amount value (C1out) exceeds a certain threshold value. Therefore, the presence of the intersection T between the curve 112 representing the output light amount value and the horizontal line representing the threshold value Cth in FIG. 5D means the start of the second rendering process. In the present embodiment, the first rendering process is interrupted when the second rendering process is started. However, the calculation of the first rendering process may be continued until the end condition is satisfied regardless of the start of the second rendering process. This is because the first rendering process is executed independently of the second rendering process. In FIG. 5D, it is indicated by a broken line that the interruption or continuation of the first rendering process is arbitrary. Since the voxel calculation is executed in unison with the opacity integration calculation, a part of the curve representing the integration value is also indicated by a broken line in FIG.

  FIG. 5E shows an echo data string 118 to be processed in the second rendering process. The echo data string 118 has the same value as the echo data string obtained after the second half of the echo data string 100 shown in FIG. 5A, that is, after the time indicated by the alternate long and short dash line 116 on the time axis. What should be noted regarding the second rendering process is that the data string to be processed is not an inverted echo data string, and that the second opacity for the second rendering process is newly accumulated from zero. In the case of performing the second rendering process, if an inverted echo data string is used, high-level data is processed from the beginning, which is not suitable for imaging an instrument. Since the second rendering process is started when a certain determination condition is satisfied, the opacity integration calculation is newly started from the time when the determination condition is satisfied. By performing the second rendering process, the pixel value corresponding to the appliance is obtained based on the echo data 120 of the appliance showing a peak in the echo data string 118.

  FIG. 5F shows a change in the output light amount value C2out (122) due to the second rendering process. In the second rendering process, it is preferable to set the rendering parameters in preference to clearly imaging the instrument. Therefore, the output light quantity value C2out also has a large change in the output light quantity value in the temporal range corresponding to the instrument or blood vessel, but since then, it tends to be saturated, the temporal change is small.

  FIG. 7 is a configuration block diagram of an ultrasonic diagnostic apparatus according to another embodiment. Compared to the configuration block diagram of FIG. 2, the configuration of the three-dimensional image processing unit 130 is different. Therefore, in FIG. 7, the same components as those shown in FIG.

  In the 3D image processing unit 130, an echo data sequence that has not been inverted is input to the second rendering start point determination unit 56. In the second rendering start point determination unit 56, when M pieces of low-level echo data continue (for example, five), the determination processing is performed with the M-th echo data as the second start point. Is called. After the low-level echo data is detected, the determination condition is not satisfied unless M data continues, so that the second start point can be set at a position where it has surely entered the blood vessel. When the second start point that satisfies the determination condition is detected, the information is transmitted to the first rendering processing unit 54. This information transmission direction is opposite to the information transmission direction shown in the functional block diagram shown in FIG. In the first rendering processing unit 54 shown in FIG. 7, the voxel calculation that has been executed until immediately before the detection is stopped when the second start point is detected. On the other hand, according to the present embodiment, when the second start point is detected, it can be reliably determined that the process has shifted to the rendering process in the blood vessel instead of the living tissue. Therefore, according to the 3D image processing unit 130, by detecting the position where the first rendering process is substantially unnecessary based on the information of the echo data obtained from a position deeper than the second start point. The first rendering process can be forcibly stopped.

  In the ultrasonic diagnostic apparatus according to another embodiment, a color Doppler processing unit (not shown) provided in the apparatus main body 40 of the ultrasonic diagnostic apparatus shown in FIG. Two starting points can also be detected.

  The color Doppler processing unit receives the reception signal output from the transmission / reception unit 46 and outputs the analysis result to the second rendering start point determination unit 56. The color Doppler processing unit can detect the average frequency and power of the Doppler shift frequency by performing quadrature detection on the received signal, removing the low Doppler shift frequency by the MTI filter, and performing autocorrelation calculation. The technique for performing blood flow imaging display based on the average frequency and power of the Doppler shift frequency in this manner is a known technique called color flow or power flow. By using this known technique, it is possible to determine a boundary between a portion where blood flow exists and a portion where blood flow does not exist on an ultrasonic tomographic image. In the second rendering start point determination unit 56, the determination result, that is, boundary information indicating the position of blood flow on each ray obtained by the color Doppler processing unit is transmitted to the second rendering start point determination unit 56. A second starting point can be defined. According to this determination method, there is an advantage that the second start point can be reliably set at a position inside the blood vessel where blood flow exists.

  The process performed in the color Doppler processing unit is preferably a power flow process rather than a color flow process. Since the power flow process has less dependence on the Doppler angle compared to the color flow process, the traveling of the blood vessel can be captured continuously. In general, the speed at which the instrument moves in the blood vessel is negligibly small compared to the speed at which blood flows in the blood vessel, so that the Doppler shift frequency is not affected by the movement of the instrument.

  FIG. 8 is a block diagram illustrating a configuration of a 3D image composition unit according to another embodiment. A three-dimensional image composition unit 140 shown in FIG. 8 is a modification of the three-dimensional image composition unit 60 shown in FIG. The three-dimensional image composition unit 140 can be used in place of the three-dimensional image composition unit 60, and has a function of adding luminance weighting to each image when synthesizing two three-dimensional images. ing. The three-dimensional image composition unit 140 is different from the above-described three-dimensional image composition unit 60 in that it includes a first display processing unit 142 and a second display processing unit 144. The first display processing unit 142 has a function of converting or adjusting the luminance and color of the first three-dimensional image. In order to use the function, for example, the luminance conversion coefficient J (settable range: −1 ≦ The parameter of J ≦ 1) is used. The second display processing unit 144 has a function of converting or adjusting the luminance and color of the second three-dimensional image. In order to use the function, for example, the luminance conversion coefficient K (settable range: − 1 ≦ K ≦ 1) parameters are utilized. Incidentally, the luminance conversion coefficients J and K are coefficients that are output from the main control unit 44 and input to the three-dimensional image composition unit 140 based on an operation input signal from the operator from the input unit 42.

  The functions of the luminance conversion coefficients J and K are the same. That is, when the luminance conversion coefficient is 1 (J = 1, K = 1), the luminance adjustment of the three-dimensional image is not performed at all, and the luminance conversion coefficient is −1 (J = −1, K = −1). In this case, luminance inversion processing is performed. When a decimal value between 1 and −1 is commanded as the brightness conversion coefficient, brightness gradation adjustment is performed.

  By having such brightness reversal and adjustment functions, the first 3D image and the second 3D image can be adjusted independently of each other. Therefore, even if echo data inversion processing is performed before rendering processing in order to visualize blood flow clearly, in a synthesized three-dimensional image, a living tissue and an instrument are differentiated by lightness or color difference. It is possible to identify them, and both can be clearly formed as a three-dimensional image.

  FIG. 9 is an explanatory diagram of image composition performed using the 3D image composition unit 140. In either the three-dimensional image composition unit 60 described with reference to FIG. 2 or the three-dimensional image composition unit 140 described with reference to FIG. 8, image composition of the first three-dimensional image and the second three-dimensional image is performed. . The image composition is executed by a so-called overlay process in which the second 3D image is superimposed on the first 3D image. The first three-dimensional image 146 shown in FIG. 9 shows the blood vessel 152 bent in the living tissue. The first three-dimensional image 146 is a three-dimensional projection image formed by performing a three-dimensional rendering process. The portion of the blood vessel 152 is displayed in white because the first three-dimensional image 146 is formed by the echo data group whose luminance is inverted. The second three-dimensional image 148 shows the shape of the instrument 154 inserted into the blood vessel. The second 3D image 148 is also a 3D projection image. The reason why the portion of the instrument 154 is displayed in white is that the second three-dimensional image 148 is formed by the echo data group whose luminance is not inverted. If the two three-dimensional images are combined in a state where both the blood vessel 152 and the instrument 154 are displayed in white in the state shown in FIG. 9, it is difficult to identify the position of the instrument 154 in the blood vessel. In order to facilitate identification, the luminance conversion coefficients J and K described with reference to FIG. 8 are set to J = 1 and K = −1, whereby the inversion process is executed only for the second three-dimensional image 148. . Then, since the portion of the instrument 154 is converted to black, the three-dimensional shape of the blood vessel 152 is clearly displayed in the synthesized three-dimensional image 150, and at the same time, the position of the instrument 156 in the blood vessel can be clearly grasped. . If colored display is applied to the second three-dimensional image, the portion of the instrument 154 can be displayed in a color different from that of the living tissue, and both can be identified more clearly.

It is the figure which showed typically the state which has contact | abutted the ultrasonic transmitter / receiver in the forearm part. 1 is a block diagram showing a schematic overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is explanatory drawing regarding each arithmetic processing of the 1st and 2nd rendering processing performed in a three-dimensional image process part. It is the figure which showed distinction of the area | region of the 1st and 2nd rendering process visually. It is explanatory drawing about 2 signal processing of a certain one echo data sequence. It is a figure which shows an example of the inversion processing characteristic of echo data. It is a block diagram of a configuration of an ultrasonic diagnostic apparatus according to another embodiment. It is a block diagram of a configuration of a three-dimensional image composition unit according to another embodiment. It is explanatory drawing of the image composition performed in a three-dimensional image composition part.

Explanation of symbols

  14 blood vessels, 16 instruments, 20 moving parts, 70 scanning plane, 72 voxel data A, 80 region of interest (ROI), 82 boundary portion, 86 beam corresponding pixel value A, 90 beam corresponding pixel value B1, 92 beam corresponding pixel value B2 94 first 3D image, 96 second 2D image, 98 instrument projection part, P1, P3 first start point, P2, P4 first end point, P5 second start point, P6 second end point.

Claims (9)

In the ultrasonic diagnostic apparatus that sequentially executes voxel operations in the depth direction for each ray set for the voxel data group obtained by transmitting and receiving ultrasonic waves to the blood vessel in which the instrument is inserted,
For each ray, a first rendering means for obtaining a pixel value constituting the first three-dimensional image from a result of sequential execution of the voxel calculation from a first start point;
Determining means for determining a second starting point for each ray;
For a ray for which the second start point is determined among a plurality of rays, a pixel value constituting a second three-dimensional image in which the device is reflected is obtained by a result of sequential execution of voxel calculation from the second start point. Second rendering means to be obtained;
Combining processing means for combining the first three-dimensional image and the second three-dimensional image to form a combined three-dimensional image;
Display means for displaying the synthesized three-dimensional image;
An ultrasonic diagnostic apparatus comprising: The ultrasonic diagnostic apparatus according to claim 1,
The ultrasonic diagnostic apparatus according to claim 1, wherein the determination unit determines a depth position in the blood vessel and on the near side of the instrument as the second start point. The ultrasonic diagnostic apparatus according to claim 1,
The ultrasonic diagnostic apparatus, wherein the second start point is set in the blood vessel based on a first end point that satisfies a voxel calculation end condition from the first start point. The ultrasonic diagnostic apparatus according to claim 1,
The ultrasonic diagnostic apparatus according to claim 1, wherein the determination unit determines the second start point based on a sequential execution result of the voxel calculation from the first start point for each ray. The ultrasonic diagnostic apparatus according to claim 1,
The ultrasonic diagnosis characterized in that the determination means determines the second start point based on an integrated value of parameters used in a voxel calculation from the first start point that is sequentially executed for each ray. apparatus. The ultrasonic diagnostic apparatus according to claim 1,
Including pre-processing means for performing luminance inversion processing on the voxel data string on each ray,
An ultrasonic diagnostic apparatus, wherein at least one of the determination unit, the first rendering unit, and the second rendering unit executes processing based on a voxel data sequence that has been subjected to the luminance inversion processing. The ultrasonic diagnostic apparatus according to claim 1,
Further includes color Doppler processing means for performing quadrature detection on a received signal obtained by transmitting and receiving ultrasonic waves and detecting a position of blood flow in accordance with a Doppler shift frequency component generated along with blood movement;
The ultrasonic diagnostic apparatus characterized in that the determination unit determines the second start point based on blood flow position information detected by the color Doppler processing unit. The ultrasonic diagnostic apparatus according to claim 1,
The synthesis processing means forms the synthesized 3D image by superimposing a second 3D image mainly representing the instrument on a first 3D image mainly representing the blood vessel. Ultrasonic diagnostic equipment. The ultrasonic diagnostic apparatus according to claim 1,
The ultrasonic diagnostic apparatus characterized in that the synthesis processing means performs synthesis processing while visually differentiating the first 3D image and the second 3D image.

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