JP2010259528A - Ultrasonograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately set a distance measuring direction in carrying out distance measurement between two trace lines. <P>SOLUTION: A first trace line portion 200A including a focal point P<SB>i</SB>of attention is specified on a first trace line 200 and a second trace line portion 202A is specified on a second trace line 202 accordingly. The two trace line portions are weighting synthesized and then a proximate straight line L is defined on the basis of the result of the synthesis. An orthogonal line M is defined as a direction intersecting the proximate straight line L at right angles, specifically an orthogonal direction passing through the focal point P<SB>i</SB>of attention. The orthogonal line M becomes a distance measuring direction. When no reference pixels are present on the orthogonal line M, a point R<SB>i</SB>of measurement is set as the nearest point of the orthogonal line M. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a technique for automatically detecting a boundary line (contour line) of a living tissue on an ultrasonic image.

  Ultrasound diagnostic apparatuses are used in the medical field. The ultrasonic diagnostic apparatus is an apparatus that transmits and receives ultrasonic waves to and from a living body and forms an ultrasonic image based on reception data obtained thereby. The ultrasonic diagnostic apparatus has a plurality of operation modes (B mode, Doppler mode, etc.) and a plurality of measurement functions. Examples of such a measurement mechanism include an NT (Nuchal Translucency) measurement function and an IMT (Intima-Media Thickness) measurement function. They are common in that the distance is measured between two points (or between two boundary lines) on the tomographic image.

  More specifically, in NT measurement (NT thickness measurement), the size (thickness) of posterior cervical edema (NT) in the fetus is measured. The edema can be generally recognized on the back side of the neck in a fetus about 10 to 14 weeks of gestation. Usually, the edema is observed as an elongated bag-like tissue on a tomographic image. When the outline is roughly divided into two boundary lines running in parallel, the interval between the two boundary lines (contour lines), in particular, the maximum width of edema (body fluid part) in the direction perpendicular to the longitudinal direction of the edema (hereinafter referred to as “NT thickness”). ")" Is known to be one index value for diagnosing fetal conditions or diseases. For example, when the NT thickness is larger than the reference value, more congenital diseases such as Down's syndrome are recognized than when the NT thickness is not. Therefore, it is desired to check the NT thickness using ultrasonic diagnosis. In the NT measurement, ultrasonic waves are transmitted / received to / from the fetus, whereby a tomographic image is displayed on the screen. On the tomographic image, two marks are manually accurately positioned on two boundary lines indicating the fetal cervical edema. At that time, the direction and position for distance measurement are determined by visual observation. Thereafter, distance measurement is automatically performed, that is, the distance between two marks is measured as NT thickness. Similar measurements are performed at a plurality of locations as necessary.

  On the other hand, in IMT measurement, one or both of the front wall and the rear wall (viewed from the probe) in the carotid artery is a measurement target. The blood vessel wall (that is, the anterior wall and the posterior wall) is composed of an intima, an intima and an adventitia when viewed from the blood flow side, that is, has a three-layer structure. In the IMT measurement, the thickness (IMT) of the composite including the inner membrane and the inner membrane is measured. This is because, on the tomographic image, the blood vessel wall is displayed quite thin, but the inner boundary line inside the intima and the outer boundary line between the media and the outer membrane are relatively likely to appear. IMT is measured as the distance between the two boundaries. It is known that when arteriosclerosis is promoted, IMT increases. By measuring IMT, one index value for diagnosing the degree of arteriosclerosis in a subject can be obtained. Specifically, in IMT measurement using an ultrasonic diagnostic apparatus, ultrasonic waves are transmitted to and received from the carotid artery, thereby displaying a tomographic image. Next, the markers are manually positioned on the inner and outer boundary lines on the front or rear wall, respectively. At this time, the two markers are positioned so that the two markers are aligned in a direction orthogonal to the blood vessel axis as much as possible. The distance between the two markers is then automatically measured and taken as IMT. The IMT may be measured at a plurality of locations, and in such a case, the maximum value, the average value, etc. are calculated.

  The following Patent Documents 1 to 6 disclose an ultrasonic diagnostic apparatus that performs IMT measurement. Patent Document 7 describes a stepwise setting of a threshold based on a histogram. Patent Document 8 describes the calculation of the standard deviation for the histogram.

JP 2008-168016 A JP 2007-319255 A JP 2000-271117 A JP 2006-51285 A JP 2006-122686 A JP-A-2005-268 Japanese Patent Publication No. 7-32773 JP 2008-253379 A

  In the manual thickness measurement as described above, the burden on the inspector is large and the reproducibility is not very good. Differences in measurement results tend to occur between inspectors. Moreover, since it is based on visual judgment, when the boundary line is unclear, the reliability of measurement tends to be extremely lowered. In particular, the direction for obtaining the distance is intuitively determined, and there is a risk of lack of accuracy. Therefore, it is desired to automatically measure the distance between two boundaries after automatically measuring the two boundaries.

  However, since the two boundary lines are not straight but meandering or curved, it is difficult to immediately determine the distance measurement direction from them. By the way, it is conceivable that an approximate straight line is generated based only on one boundary line, and the distance measurement direction is determined as the vertical line, but the determined direction does not consider the traveling shape of the other boundary line at all. Therefore, the distance measurement direction tends to be inappropriate.

  An object of the present invention is to enable a distance measurement direction to be determined in an appropriate direction according to the shape of two tissue boundary lines.

  Alternatively, an object of the present invention is to enable the distance measurement direction to be determined in consideration of empirical rules in distance measurement.

  Alternatively, an object of the present invention is to provide information that can easily recognize the collective and statistical properties of a plurality of calculated distances.

  (1) The ultrasonic diagnostic apparatus according to the present invention includes a first trace line representing a first target boundary line in a target tissue and a first trace in the target tissue based on a tomographic image obtained by transmitting and receiving ultrasonic waves. Boundary detecting means for generating a second trace line representing a boundary line of interest; an approximate straight line generating means for generating an approximate straight line on the tomographic image based on the first trace line and the second trace line; Distance measuring means for determining a distance measuring direction with reference to the approximate straight line and measuring a distance between the first trace line and the second trace line.

  According to the above configuration, after the approximate straight line is defined based on both of the two trace lines, the distance measurement direction is determined based on the approximate straight line. Therefore, since the form of the two trace lines is taken into account when specifying the distance measurement direction, the distance measurement direction can be determined as a desired direction. It is desirable that the distance measurement direction is basically determined as a direction orthogonal to the approximate straight line. However, when there is no pixel that can be referred to in such an orthogonal direction, it is desirable that the effective pixel closest to the orthogonal direction or a pixel that satisfies other conditions be a distance measurement target (measurement point). In this case, strictly speaking, the distance measurement direction is a direction connecting the attention point on the first trace line and the measurement point on the second trace line. In calculating the approximate line, the two trace lines may be considered equally, but each may be given a weight. According to experiments, if a large weight is given to the trace line that is closer to flat, the actual distance measurement direction can be determined in a good direction from the rule of thumb. In addition, according to such a configuration, it is possible to avoid the problem that the distance measurement direction becomes excessively complicated or complicated due to excessive response to the shape change of the non-flat trace line. Note that the weight distribution can be dynamically changed.

  Desirably, it includes a region-of-interest setting means for setting a region of interest including the first target boundary line and the second target boundary line on the tomographic image, and at each position in a reference direction defined by the region of interest, A first line portion is referred to from among the first trace lines, and a second line portion is referred to from among the second trace lines, and the approximate straight line generating means is configured to change the first line portion at each position in the reference direction. The approximate straight line is sequentially generated based on the one line portion and the second line portion. According to this configuration, a single approximate line is not defined between two trace lines, but an approximate line reflecting the form of two line portions is defined at each position in the reference direction. Even if one trace line is meandering, curved, etc., the distance measurement direction can be appropriately determined at each position. You may variably set the magnitude | size of a 1st line part and a 2nd line part according to the nonlinearity of each line, a bending degree, etc. The reference direction is preferably the horizontal direction of the region of interest, but may be a direction according to the display coordinate system.

  Incidentally, it is desirable to use the coordinate system of the region of interest when determining the second line portion corresponding to the first line portion. That is, it is desirable that two line portions are cut out from two trace lines in the same horizontal section on the horizontal axis of the region of interest. However, if the approximate traveling directions of the two trace lines are known in advance, the first line portion and the second line portion can be associated with each other in the direction orthogonal to the traveling direction. Alternatively, the first line portion and the second line portion can be associated according to an absolute display coordinate system.

  Preferably, the first line portion is a portion extending on both sides of the target position in the reference direction, and the second line portion is a portion corresponding to the first line portion. The reference direction is preferably a direction defined as the upper or lower side of the region of interest. Desirably, each line portion is defined as a range having a spread around the position of interest. If the range is increased, the distance measurement direction is not significantly affected by the bending of the two trace lines (the inclination does not change much with respect to the vertical direction of the region of interest). On the other hand, if the range is reduced, the distance measurement direction is greatly affected by the bending of the two trace lines (the inclination is likely to change with respect to the vertical direction of the region of interest).

  Preferably, the approximate line generation unit calculates a weighted composition process based on the first line portion and the second line part, and calculates the approximate line based on the result of the weighted composition process. And calculating means. As a rule of thumb, when a relatively flat trace line and a trace line with a large variation that are not parallel are running side by side, the distance measurement direction tends to be determined based on the former. If the distance measurement direction is determined based on the latter, the distance measurement direction will be different in the part where the curvature of the trace line is large, and sometimes it will be complicated and crossed each other. Deviation from the sense of the distance measurement direction becomes large. Therefore, it is desirable to define an approximate straight line with more emphasis on the flat trace line as described above, and weighting synthesis processing realizes this. However, it is also possible to give a larger weight to the trace line having a larger variation depending on the purpose. Furthermore, the weight distribution can be automatically and adaptively determined.

  Preferably, the first trace line has a form closer to a straight line than the second trace line, and the synthesis processing unit gives a large weight to the first line portion and a small weight to the second line portion. give. Desirably, the said composition processing means raises the reference density about the said 1st line part rather than the reference density about the said 2nd line part. In calculating the approximate line, weighting can be easily realized if the reference densities (number of reference pixels per unit distance) for the two trace lines are made different. That is, the reference density per unit length is varied. This is equivalent to changing the thinning rate.

  Preferably, the distance measurement direction is an orthogonal direction orthogonal to the approximate straight line or an approximate orthogonal direction approximate to the orthogonal direction. The approximate orthogonal direction is a direction that is determined by slightly correcting it because, for example, there is no effective sample point in the orthogonal direction. Therefore, both may be considered as orthogonal directions.

  Preferably, display processing means for displaying a plurality of lines representing a plurality of distance measurement directions obtained for a plurality of positions in the reference direction together with the first trace line and the second trace line on the tomographic image. Including. According to this configuration, the measurement status can be confirmed. When displaying all of the plurality of distance measurement directions, the screen content becomes complicated. Therefore, a plurality of representative directions may be displayed by thinning out or the like.

  Preferably, the distance histogram is displayed, including means for generating a distance histogram based on a plurality of distances obtained for a plurality of positions in the reference direction. Preferably, the horizontal axis of the distance histogram indicates the magnitude of the distance, and the vertical axis of the distance histogram indicates the relative frequency. According to this configuration, it is possible to intuitively understand the distance distribution or the statistical situation. If the vertical axis is standardized, it is easy to compare distance histograms.

  (2) The ultrasonic diagnostic apparatus according to the present invention includes a first trace line representing an outer boundary line in a blood vessel wall and an inner boundary line in the blood vessel wall based on a tomographic image obtained by transmitting and receiving ultrasonic waves. Boundary detection means for generating a second trace line representing the same, approximate line generation means for generating an approximate line based on the first trace line and the second trace line on the tomographic image, and the approximate line as a reference And a distance measuring means for measuring a distance as a thickness of the blood vessel wall between the first trace line and the second trace line.

  (3) The ultrasonic diagnostic apparatus according to the present invention includes a first trace line representing a lower boundary line of fetal posterior cervical edema based on a tomographic image obtained by transmitting and receiving ultrasonic waves, and the posterior fetal cervix Boundary detecting means for generating a second trace line representing the upper boundary line of edema; and an approximate straight line generating means for generating an approximate straight line based on the first trace line and the second trace line on the tomographic image; A distance measuring unit that determines a distance measuring direction based on the approximate straight line and measures a distance as a thickness of the posterior cervical edema between the first trace line and the second trace line; Features.

  (4) A program according to the present invention is a program executed in an ultrasonic diagnostic apparatus or an information processing apparatus that processes an ultrasonic image, and represents a first target boundary line in a target tissue based on a tomographic image. A function of generating a first trace line and a second trace line representing a second target boundary line in the target tissue, and an approximate straight line based on the first trace line and the second trace line on the tomographic image And a function of determining a distance measuring direction with reference to the approximate straight line and measuring a distance between the first trace line and the second trace line.

  According to the present invention, the distance measurement direction can be determined in an appropriate direction according to the shapes of the two tissue boundary lines. Or the information which can recognize easily the collective and statistical property of the calculated several distance can be provided.

1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows IMT measurement on the tomographic image of a blood vessel. It is a figure which shows NT measurement (NT thickness measurement) on the tomographic image of a fetus. It is a figure which shows the setting of three area points on each search line in IMT measurement. It is a figure which shows the other setting method of three area points in IMT measurement. It is a figure which shows the two belt | band | zone area | regions set in the region of interest in IMT measurement. It is a figure which shows the distance measurement (IMT measurement) between two trace lines. It is a flowchart for demonstrating the operation example in IMT measurement. It is a figure for demonstrating the section setting on each search line in NT measurement. It is a figure which shows the belt | band | zone area | region set in each sub region of interest in NT measurement. It is a figure which shows the distance measurement (NT thickness measurement) between two trace lines. It is a flowchart for demonstrating the operation example in NT thickness measurement. It is a figure for demonstrating the determination method of the distance measurement direction based on two trace lines. It is a figure for demonstrating the other synthetic | combination method of two trace lines. It is a figure for demonstrating the synthesis | combination of the data sequence between two trace lines. It is a flowchart for demonstrating the specific example of the distance measurement between two trace lines. It is a figure for demonstrating IMT measurement. It is a figure for demonstrating NT thickness measurement. It is a figure for demonstrating the production | generation of the distance histogram represented as relative frequency. It is a figure which shows an example of the distance histogram represented as relative frequency.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

(1) Configuration of Ultrasonic Diagnostic Device FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic device according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof. The probe 10 is an ultrasonic probe that is brought into contact with the body surface, and transmits ultrasonic waves to the living body and receives reflected waves from within the living body. The probe 10 has a 1D array transducer (not shown). The 1D array transducer is composed of a plurality of transducer elements, whereby an ultrasonic beam B is formed. The ultrasonic beam B is electronically scanned, thereby forming a scanning surface S that is a two-dimensional data capturing area. As the electronic scanning method, electronic linear scanning, electronic sector scanning, and the like are known. A 2D array transducer for forming a three-dimensional data capture area may be provided in the probe 10. In the present embodiment, when IMT measurement is performed, the probe unit 10 is brought into contact with the neck, thereby acquiring tomographic image information of the carotid artery. On the other hand, when NT measurement is performed, the probe 10 is brought into contact with the abdomen of a pregnant woman, whereby tomographic image information of the fetus is acquired.

  The transmission unit 12 functions as a transmission beam former. The transmitter 12 supplies a plurality of transmission signals to the 1D array transducer during transmission. As a result, a transmission beam is formed. On the other hand, when a reflected wave is received by the probe 10 from the living body, a plurality of reception signals are output in parallel from the 1D array transducer, and are processed by the reception unit 14. The reception unit 14 is configured as a reception beam former, and performs phasing addition processing on a plurality of reception signals, thereby outputting a reception signal (beam data) after phasing addition.

  The signal processing unit 16 performs some signal processing on the beam data. Such signal processing may include processes such as detection, logarithmic compression, noise removal and the like. Beam data output from the signal processing unit 16 is sent to the image forming unit 17. The image forming unit 17 is configured by a digital scan converter (DSC) in this embodiment. The image forming unit 17 has a coordinate conversion function, an interpolation processing function, and the like. In the image forming unit 17, a tomographic image is constructed based on the plurality of beam data. The image data is sent to the display processing unit 18 and also to the measurement unit 22.

  The display processing unit 18 has an image composition function and the like, and outputs display image data to the display unit 20. In the display processing unit 18, processing for combining a graphic image with a tomographic image is performed. The display unit 20 displays a tomographic image as an ultrasonic image. An ultrasonic image (such as a two-dimensional color Doppler image) other than the tomographic image may be displayed.

  The control unit 24 performs operation control of each configuration shown in FIG. 1, and the control unit 24 includes a CPU and an operation program. An operation panel 26 is connected to the control unit 24. The operation panel 26 includes a keyboard and a trackball and functions as a user input device. Using the operation panel 26, the user can set a region of interest (ROI). Specifically, while viewing a tomographic image displayed on the screen, an arbitrary position and an arbitrary rotation angle on the tomographic image. It is possible to specify a region of interest with an arbitrary size. Based on this user input, the control unit 24 sets (recognizes) the region of interest.

  The measurement unit 22 functions as an IMT measurement unit and an NT measurement unit in this embodiment. Specifically, the measurement unit 22 traces two boundary lines (contour lines) in the region of interest to generate two trace lines, and measures a distance, that is, a thickness between them. Incidentally, the coordinate information of the region of interest is given from the control unit 24 to the measurement unit 22. The measurement unit 22 is actually realized as a calculation function of software, and it may constitute a part of the control unit 24. The measurement result of the measurement unit 22 and necessary graphic data are sent from the measurement unit 22 to the display processing unit 18.

  FIG. 2 shows the state of IMT measurement. The image 28 is a tomographic image (B-mode image) of the blood vessel. A cross section of the blood vessel is represented on the tomographic image 28, and the blood vessel has a front wall 30 and a rear wall 32. Incidentally, the side closer to the probe side is the front wall 30 and the side farther from the probe side is the rear wall 32. Between the front wall 30 and the rear wall 32 is a blood flow part 34. As is well known, the front wall 30 includes an inner membrane 36, a middle membrane 38 and an outer membrane 40 as viewed from the blood flow portion 34 side. Here, the intima 36 is a very thin layer, which appears substantially on the image as a single line. In the IMT measurement, the thickness of the complex between the inner boundary line 42 and the outer boundary line 44, that is, the inner membrane 36 and the inner membrane 38 is measured. Similar to the front wall 30, the rear wall 32 includes an inner membrane 46, a middle membrane 48, and an outer membrane 50 as viewed from the blood flow portion 34. Reference numeral 52 represents an inner boundary line, and reference numeral 54 represents an outer boundary line.

  When performing IMT measurement on the front wall 30 on the tomographic image as described above, a region of interest (ROI) 56 is set so as to include the front wall 30 in order to limit the calculation range. Similarly, when performing IMT measurement on the rear wall 32, the region of interest (ROI) 60 is set so as to include the rear wall 32. In the region of interest 56, as indicated by reference numeral 58, the distance between the intima boundary line 42 and the epicardial boundary line 44 is measured as IMT 58. Similarly, in the region of interest 60, the distance between the inner boundary line 52 and the outer boundary line 54 is measured as the IMT 62.

  In this embodiment, the regions of interest 56 and 60 are specified by the user, and at that time, the horizontal lines (upper side and lower side) of the regions of interest 56 and 60 are as parallel as possible to the respective boundary lines. The tilt angle of the area is specified. In the present embodiment, the lower side of the region of interest 56 is the base line 56A, and the base line 56A functions as a start line when a plurality of search lines are set. On the other hand, in the region of interest 60, the upper side is defined as a baseline 60A, and the baseline 60A also functions as a start line when defining a plurality of search lines. Incidentally, when performing IMT measurement, the region of interest 56, 60 is designated by the user so that both the inner boundary line and the outer boundary line are included in the region of interest 56, 60. Of course, such a setting can be automated. In FIG. 2, the X direction represents the horizontal direction on the display screen, and the Y direction represents the vertical direction on the display screen. The x direction described later is the horizontal direction of the region of interest, and the y direction is the vertical direction of the region of interest. The former is an absolute display coordinate system, while the latter is a relative coordinate system based on the region of interest.

  FIG. 3 shows a state where NT measurement (that is, NT thickness measurement) is performed. The tomographic image 164 represents a cross section of the fetus 166. Reference numeral 168 represents the placenta. Reference numeral 170 represents a fetal cervical edema. The edema 170 appears as an elongated cavity on the tomographic image 164. Specifically, the edema is a region surrounded by an upper boundary line 174 and a lower boundary line 176 that run side by side on the tomographic image, and the inside 172 is a body fluid part.

  In this embodiment, when performing NT measurement, the region of interest 178 is designated by the user as shown. The region of interest 178 is configured as a combination of two sub-regions of interest 180 and 182, and a base line 178 </ b> A serving as an intermediate line is formed between the sub-regions of interest 180 and 182. The upper boundary line 174 is traced in the upper sub region of interest 180, and similarly, the lower boundary line 176 is traced in the lower sub region of interest 182. When two trace lines are drawn by these processes, the NT thickness 184 is measured between them. In such NT measurement, similarly to the above-described IMT measurement, when the user designates the region of interest 178, the calculation process basically proceeds automatically after the designation, thereby reducing the burden on the user. . Moreover, since it does not depend on subjectivity, objectivity or reproducibility can be improved. Incidentally, when specifying the region of interest 178 by the user, the position and inclination of the combined region of interest 178 are specified so that the boundary lines 174 and 176 are included in the sub regions of interest 180 and 182, respectively. In particular, the region of interest 178 is defined such that the base line 178A, which forms an intermediate line, is located exactly between the two boundary lines 174, 176. Here, the base line 178A forms a start line when a plurality of search lines are set in each of the sub-regions of interest 180 and 182. Therefore, it is desirable to define the region of interest 178 so that the base line 178A is as parallel as possible to the two boundary lines 174 and 176.

(2) Specific Example of IMT Measurement Next, a specific example of IMT measurement will be described with reference to FIGS.

  In FIG. 4, a region of interest 56 is shown. The region of interest 56 includes a part of the inner boundary line 42 and a part of the outer boundary line 44. In FIG. 4, the boundary lines 42 and 44 are represented as straight lines for convenience. Incidentally, the code | symbol 30 represents the front wall and the code | symbol 34 represents the blood-flow part. That is, the region of interest 56 is a region of interest set for the front wall 30.

  In FIG. 4, the lower side of the region of interest 56 functions as a baseline 56A. That is, the base line 56A is a line extending in the x direction, and a search line 58 is formed in the y direction at each position in the x direction. Specifically, each search line 58 is a line extending in the y direction orthogonal to the base line 56A, starting from each point (each pixel) on the base line 56A. That is, the direction becomes the search direction. If the ROI is rectangular, the search direction is parallel to the left and right sides of the region of interest 56. As shown in FIG. 4, pixel value reference and edge detection are sequentially performed from the start point 58A toward the search direction (forward) on each search line. That is, the pixel value of the target pixel is referred to, and the pixel value is compared with a predetermined threshold value (provisional threshold value). If the pixel value is larger than the threshold value, it is identified as an edge point (rising point), and The point becomes the reference edge point. In the figure, reference edge points are indicated by reference numeral 60. The reference edge point 60 functions as a first section point in the present embodiment, and the second section point 62 and the third section point 64 are determined based on the reference edge point 60. The temporary threshold may be a fixed value, but is preferably a threshold determined from a histogram formed by referring to the entire region of interest. Various methods are conventionally known as a method for determining a threshold value from a histogram.

  More specifically, the reference edge point 60 is a point detected in front of the inner boundary line 42. In other words, a temporary threshold is set so that such a rising point on the near side is detected. ing. The reference edge point 60 serves as a reference point when the two sections are defined, that is, the origin, and the second section point 62 is defined as a point obtained by adding a certain distance W1 forward in the search direction with respect to the reference edge point 60. Thus, the third section point 64 is determined as a point obtained by adding a certain distance W2 forward in the search direction with respect to the second section point 62. The third section point 64 may be determined by adding the distance W2 to the reference edge point 60. W2 is larger than W1. A section between the first section point 60 and the second section point 62 is a first section, and a section between the second section point 62 and the third section point 64 is a second section. The first section constitutes an element of a first belt region described later, and the second section constitutes an element of a second belt region described later. As a result, each first section is set to straddle the inner boundary line 42, that is, the sizes of the reference edge points 60 and W1 are determined so that such a condition is satisfied. Similarly, the position of the third section point 64, that is, the size of W2 is determined so that each second section straddles the outer boundary line 44.

  In the specific example shown in FIG. 4, the reference edge point 60 is detected on the front side of the inner boundary line, but instead, a method as shown in FIG. 5 can be adopted. In the method shown in FIG. 5, edge detection processing is sequentially executed from the start point along the search line 58. Here, the temporary threshold value is set to a value that allows detection of the inner boundary 42 that is the original edge or a position close thereto, and as a result, the temporary edge point 66 is found on or near the inner boundary 40. A first section point 68 is set at a predetermined distance on the near side of the temporary edge point 66, and a second section point 70 is set at a predetermined distance on the far side of the temporary edge point 66. A portion between the first section point 68 and the second section point 70 is determined as the first section. On the other hand, the search is started again from the temporary edge point 66 forward in the search direction. In that case, another temporary threshold value is set so that the outer boundary line 44 or its vicinity is detected, and by repeating the comparison between such another temporary threshold value and each pixel value, the temporary edge point 72 is obtained. Detected. With this as a reference, a first segment point 74 is defined on the front side thereof, and a second segment point 76 is defined on the back side, that is, the front side of the temporary edge point 72. Between the first section point 74 and the second section point 76 is the second section. As described above, an edge to be detected or a point close thereto may be detected, and the section may be determined based on the detected edge. However, according to the method shown in FIG. 4, the second interval point 62 and the third interval point 64 can be set immediately by simply detecting the reference edge point that is relatively close to the start point. The advantage is that it can be reduced to achieve rapid processing.

  In FIG. 6, the reference edge point is detected on the search line 58 at each coordinate in the x direction and two section points are set based on the reference edge point, thereby arranging a plurality of first section points on the plurality of search lines 58 first. As shown in FIG. Similarly, a second section point line 80 is configured as an array of second section points on the plurality of search lines 58. Further, a third section point line 82 is configured as an array of a plurality of third section points on the plurality of search lines 58. A region between the first segment point line 78 and the second segment point line 80 is defined as an inner band region 84. Similarly, the outer zone area 86 is defined between the second segment point line 80 and the third segment point line 82.

  The inner band region 84 includes the inner boundary line 42 therein, which is a region near the inner boundary line. The outer belt region 86 includes an outer boundary line 44 therein, which is a region near the outer boundary line. The inner band area 84 is a local area referred to for determining a threshold (main threshold) used when detecting the inner boundary line 42, and at the same time, the inner band area 84 is a search area for the inner boundary line 42. But there is. The outer band region 86 is a local region that is referred to in order to determine a threshold value (this threshold value) used when detecting the outer boundary line 44, and the outer band region 86 is a search region for the outer boundary line 44. It is what you make.

  Specifically, by referring to the band region 84, a histogram is created based on a plurality of pixel values included therein, and a threshold for edge detection (this threshold) is directly or indirectly determined from the histogram. Determined. Also for the band region 86, a histogram is created by referring to the internal pixel value group, and a threshold (main threshold) is determined based on the histogram. Conventionally, various methods have been proposed as a method for determining a threshold value based on a histogram. The inner boundary point 88 is detected on each search line 58 using the threshold value determined by referring to the inner band region 84. In that case, on each search line, the first interval point line 78 in the inner band region 84 is used as a start line, and edge detection processing using a threshold value is sequentially executed from there to the second interval point line 80 side. Similarly, in the outer band region 86, the detection of the outer boundary point 90 is executed on each search line using the threshold value determined by referring to the outer band region 86. Also in this case, edge detection is sequentially performed on the side of the third section point line 82 on each search line using the second section point line 80 as a start line.

  FIG. 7 shows the inner trace line 92 and the outer trace line 94 formed as described above. The inner trace line 92 is constituted by an array of a plurality of inner boundary points 88 obtained by edge detection with respect to the inner boundary line. The outer trace line 94 includes a plurality of outer boundary points obtained by edge detection with respect to the outer boundary line. Of course, a smooth trace line may be configured by applying interpolation processing, smoothing processing, or the like to the arrangement of a plurality of boundary points. When the two trace lines 92 and 94 are automatically extracted and drawn as described above, IMT measurement is performed between the two trace lines 92 and 94. Specifically, IMT measurement is performed at one or more points in the x direction. Here, IMT is represented by reference numeral 96. In this case, the direction in which the thickness, that is, the distance is measured is the y direction in the example shown in FIG. The distance measurement direction may be adaptively determined based on the shapes of the two trace lines.

  According to the above-described method, the inner boundary line and the outer boundary line can be accurately and accurately detected after determining appropriate threshold values for each band area by exploratory setting of the two band areas. There is an advantage that the trace line can be accurately drawn. In the past, the entire region of interest was always referred to when setting the threshold. However, such a method refers to a lot of information other than the information near the target boundary line, and in some cases it is affected by noise. However, in this embodiment, it has been confirmed by experiments that such a problem can be greatly alleviated or avoided. In particular, in the present embodiment, since the band regions are defined for two boundary lines, the threshold value suitable for each boundary line can be set to greatly increase the reliability of boundary detection.

FIG. 8 shows an example of an IMT measurement method as a flowchart. In S100, a region of interest (ROI) is designated by the user on a tomographic image representing a blood vessel. In that case, it is desirable to set the ROI so that the horizontal axis in the region of interest is as parallel as possible to the two boundary lines. In S102, the entire region of interest is referred to determine a temporary threshold, and a histogram (overall histogram) is created based on a plurality of pixel values included therein. In S104, the provisional threshold a ₀ is calculated based on the histogram. The temporary threshold a ₀ is for determining the reference edge point as described above, and does not require strict boundary detection. Therefore, even when the entire region of interest is referred to when determining the temporary threshold a ₀ There is basically no problem.

In S106, the search for the reference edge point is started on any of the search lines designated in order. In S108, the reference pixel values is compared to the temporary threshold value a _0, the pixel value S110 proceeds if it is temporary threshold a ₀ or is executed. Incidentally, error processing may be applied when the reference edge point cannot be detected even when reaching the upper side of the region of interest, that is, the end line. Examples of such error processing include a method of determining a reference edge point on the search line by interpolation using a reference edge point detected on the adjacent search line.

  In S110, the reference edge point, that is, the first section point is specified. In S112, the second section point is specified based on the reference edge point, and in S114, the third section point is specified based on the reference edge point. As a result, three section points are determined on the search line currently being processed. In S116, it is determined whether there is an unprocessed search line, and if there is, the process from S106 is repeatedly executed. On the other hand, when it is determined in S116 that the process has progressed to the last search line, the steps after S118 and the steps after S130 described below are executed.

  A series of steps from S118 to S128 and a series of steps from S130 to S140 may be executed in order or may be executed in parallel. A series of steps from S118 to S128 corresponds to the tracing process for the inner boundary line, and a series of steps from S130 to S140 corresponds to the tracing process for the outer boundary line.

In S118, the first band region is referred to, and a first partial histogram is created based on the pixel group included therein. In S120, the threshold value a ₁ is determined based on the first portion histogram. In S122, by utilizing the threshold value a _1, which search is started on the search line, if found threshold a ₁ or more pixel values in S124, the pixel value is specified as the inner boundary point in S126. Until it is determined in S128 that there are no unprocessed search lines, the steps after S122 are repeated.

On the other hand, in S130, the second band region is referred to, and a second partial histogram is created based on the pixel group included therein. In S132 it is determined the threshold a ₂ based on the second portion histogram in S134, the search on the specified search line is started. If a pixel value equal to or greater than the threshold value a ₂ is found in S136, the point having the pixel value is identified as the outer boundary point in S138, and whether or not the process has progressed to the last search line in S140. To be judged. If the process has not reached the last search line, the processes after S134 are repeatedly executed.

  When a plurality of inner boundary points are detected in the first band region and a plurality of outer boundary lines are detected in the second band region, that is, when an inner trace line and an outer trace line are formed, in S142, IMT measurement is performed between the two trace lines. In this case, IMT measurement is performed at a plurality of locations in the x direction, and the maximum value, minimum value, average value, and the like are obtained from the measurement results.

(3) Specific Example of NT Measurement Next, a specific example of NT measurement will be described with reference to FIGS. 9 to 12.

FIG. 9 shows a region of interest 178 set on the tomographic image. The region of interest 178 includes a cross section of the fetal posterior cervical edema (NT) 170, and the region of interest 178 includes an upper boundary line 174 and a lower boundary line 176. More specifically, the region of interest 178 is divided into an upper sub-region of interest 180 and a lower sub-region of interest 182 with a base line 178A forming an intermediate line as a connecting line. 174 is included, and a lower boundary line 176 is included in the lower sub-region of interest 182.

  Within the region of interest 178, the baseline 178A functions as a common start line for the two sub-regions of interest 180,182. That is, in the upper sub-region of interest 180, the search line 100 is set in the y direction at each coordinate in the x direction, and the edge search is repeatedly executed on each search line 100 from the start point 100A on the base line 178A toward the upper side. The The threshold used in that case is a temporary threshold. When the pixel value exceeds the temporary threshold, the point is determined as the reference edge point (first section point) 102. Then, the second section point 104 is determined as a point separated by a predetermined distance W3 with respect to the reference edge point 102. As a result, the first segment point 102 and the second segment point 104 are determined on the search line 100. Similarly, also in the lower sub region of interest 182, the search line 106 is set in the y direction for each coordinate in the x direction, and edge detection is performed from the start point on the base line 178A toward the lower side that is the end line. It is executed repeatedly. At a point where the pixel value exceeds the provisional threshold value, it is determined as a reference edge (first interval point) 108, and the second interval point 110 is specified as a point separated by a predetermined distance W4 with reference to that. As a result, the first section point 108 and the second section point 110 are determined on each search line 106. Each first section in the upper sub region of interest 180 is set across the upper boundary line 174, and each second section in the lower sub region of interest 182 is set across the lower boundary line 176.

  As shown in FIG. 10, if the above processing is performed for each x coordinate (for each pixel arranged in the X direction), it is possible to define the band region 120 in the upper sub region of interest 180. That is, the band region 120 is defined as a region between the first section point line 112 and the second section point line 114, and here, the first section point line 112 is configured as an array of a plurality of first section points 102. The second section point line 114 is configured as an array of a plurality of second section points 104. Similarly, in the lower sub region of interest, a band region 122 is defined, that is, the band region 122 is an area sandwiched between the first section point line 116 and the second section point line 118. The first section point line 116 is configured as an array of a plurality of first section points 108, and the second section point line 118 is configured as an array of a plurality of second section points 110.

  When the band region 120 is determined, the pixels in the band region 120 are referred to, and a histogram is generated based on a plurality of pixel values. Based on the histogram, a threshold value (main threshold value) for detecting the upper boundary line is calculated. Similarly, the pixels in the band region 122 are referred to, a histogram is generated based on a plurality of pixel values, and a threshold value (main threshold value) for detecting the lower boundary line is calculated from the histogram. In the belt region 120, the upper boundary point 124 is detected on each search line 110 using the threshold value obtained as described above. As a result, an upper trace line 126 is formed as an array of a plurality of upper boundary points 124. On the other hand, in the band region 122, edge detection is performed on each search line using the threshold value determined as described above, and thereby a plurality of lower boundary points 128 are detected. A lower trace line 130 is formed as an arrangement of them. Of course, smoother trace lines 126 and 130 may be configured by applying interpolation processing and smoothing processing to the plurality of upper boundary points 124 and the plurality of lower boundary points 128. Good.

  In FIG. 11, the NT thickness 132 is measured between the upper trace line 126 and the lower trace line 130. It is desirable to measure the NT thickness 132 at a plurality of coordinates in the x direction. Although the thickness measurement direction is parallel to the y direction in the embodiment shown in FIG. 11, it is desirable to adaptively determine the distance measurement direction in an appropriate direction according to the form of the trace lines 126 and 130.

  According to the NT measurement method described above, there is an advantage that each boundary line can be accurately detected by setting a threshold value independently in the two sub-regions of interest. In addition, there is an advantage that the NT thickness can be measured in the entire region of interest. Also in the NT measurement method described above, a band region that is a local region is defined in detecting each boundary line, and a threshold value is determined based on a pixel value group referred to in the band region. Can be optimized. Moreover, since the boundary line is detected in the band region, there is an advantage that the influence of noise or the like can be eliminated as much as possible.

  FIG. 12 is a flowchart showing the NT measurement method described above. In S200, the combined region of interest is designated by the user on the tomographic image. In this case, the position and inclination of the region of interest are determined so that the boundary lines are included in the two sub regions of interest. When the region of interest is appropriately defined, a baseline that is an intermediate line is located between the two boundary lines. Next, the first trace line generation process S202 and the second trace line generation process S204 are executed. They may be executed in parallel or in order. In FIG. 12, the specific contents of the first trace line generation process S202 are shown. In the second trace line generation process S204, the same configuration as that of the first trace line generation process is adopted. The description of the second line trace generation process S204 is omitted.

  In S206, the pixel value group in the upper sub-region of interest, that is, in the half ROI is referred to, thereby creating a whole histogram. That is, the entire sub-region of interest is referred to as the local region, not the belt region.

In S208, the temporary threshold a ₀ is calculated based on the whole histogram generated in S206. In S210, edge detection is performed on the search lines designated in order. In S212, the reference pixel values if it is determined that the tentative threshold a ₀ above, in S214, the point is identified as the reference edge point (first interval point). In S216, the second segment point is specified based on the reference edge point, that is, the first segment point. Such a process is repeated until it is determined in S218 that the process for the last line has been completed.

In S220, a pixel value group is referred to in a band region composed of a plurality of first sections configured as described above, and thereby a partial histogram is created. In S222, the threshold value a ₁ is determined based on the partial histogram. In S224, the edge searching is started on the search line which is sequentially designated, in S226, if a reference pixel values is determined to be the threshold value a ₁ or more, when the point is a boundary point at S228 Identified. Such a process is repeated until the final search line.

  With the first trace line generation process S202 as described above, it is possible to generate the first trace line with respect to the upper boundary line. On the other hand, the second trace line generation process S204 is performed using the same method as described above. A second trace line can be generated for the lower boundary line. In S232, the NT thickness is measured between the upper trace line and the lower trace line formed as described above. In that case, the NT thickness is measured at one or a plurality of positions in the x direction, and the maximum value, the minimum value, the average value, etc. are calculated from the plurality of NT thicknesses as necessary.

(4) Setting Method of Distance Measurement Direction Next, an adaptive setting method of the distance measurement direction based on two trace lines will be described using FIG. 13 to FIG.

  FIG. 13 shows a first trace line 200 and a second trace line 202. In FIG. 13, the first trace line 200 is represented as a straight line for convenience. The first trace line 200 corresponds to an outer trace line in IMT measurement, and corresponds to a lower trace line in NT measurement. On the other hand, the second trace line 202 corresponds to an inner trace line in IMT measurement, and corresponds to an upper trace line in NT measurement. In the present embodiment, as a rule of thumb, the flatter first trace line 200 is defined as the reference trace line.

When distance measurement is performed on the attention point P _i existing on the first trace line 200, a composite range 204 centered on the attention point P _i is determined. One end of the synthetic range 204 is represented by P _in, the other end is represented by P _{i + n.} Incidentally, n is, for example, 100, that is, 100 points are referenced on each of the right side and the left side with the attention point as the center. The reference range in the first trace line 200 is the first trace line portion 200A.

On the other hand, in the second trace line 202, the second trace line portion 202A is referred to. The second trace line portion 202 </ b> A is a line portion within a range corresponding to the synthesis range 204 described above. That is, in the x direction, the first trace line portion 200A and the second trace line portion 202A are extracted from the same range. One end of the second trace line portions 202A are represented by Q _in, the other end is represented by Q _{i + n.} A point corresponding to the attention point P _i is a corresponding point Q _i . The x-direction coordinate of the point of interest P _{i and} the x-direction coordinate of the corresponding point Q _i are the same. Incidentally, the x direction is the horizontal direction of the region of interest, and the y direction is the vertical direction of the region of interest. The region of interest is a region designated by the user while looking at the form of the target tissue, and the designation is respected when cutting out the two trace lines.

In the case where the distance measurement direction is determined for P _i (or the address x _{i in the} x direction) for the attention point, in this embodiment, the first trace line portion 200A and the second trace line portion 202A are weighted and combined. Then, an approximate straight line is generated from the result of the synthesis process.

  More specifically, as indicated by reference numeral 206, the first trace line portion 202A is shifted in the y direction (downward) and overlapped with the first trace line portion 200A. The second trace line portion after the shift is indicated by reference numeral 202B. The second trace line portion 202B coincides with one end of the first trace line portion 200A at one end (left end) thereof. However, this is not an essential condition but for convenience. After such superposition (or simultaneously with superposition), an approximate straight line (primary approximate straight line) L is generated using a known method based on the two trace line portions. In the calculation, all the pixel values constituting the first trace line portion 200A are referred to. On the other hand, the second trace line portion 202B is thinned out at a certain ratio and then a part of pixel values is referred to. Has been. Specifically, only the pixels 206 indicated by white circles in the figure are referred to in the synthesis process. In FIG. 13, every second pixel is referred to, but this is an example. In the calculation example described later, every other pixel is referred to. In the illustrated example, the weight of the first trace line portion 200A is 1.0, whereas the weight of the second trace line portion 202B is 0.33 (0.5 in the calculation example described later). That is, all the points are sample points for the former, but only one of the three pixels is referenced for the latter (only two of the two pixels are referenced in the calculation example described later).

  By applying a known primary approximate straight line generation process (interpolation process) based on the data sequence generated by the weighted synthesis process as described above, an approximate straight line L can be obtained as shown in the figure. The approximate line L is based on both of the two trace line portions 200A and 202B (has an inclination reflecting both), and more specifically, is greatly influenced by the form of the first trace line portion 200A. However, the form of the second trace line portion 202B is considered at a constant rate.

Thus, in this embodiment, passes through the point of interest P _i, and in the direction perpendicular to the approximate line L, perpendicular line M is drawn, the direction is defined as the distance measurement direction. However, since the pixel on the second trace lines 202 on the orthogonal line M is sometimes not the case, in the present embodiment, the pixels closest to the perpendicular line M is defined as the measurement point R _i. Direction connecting the point of interest P _i and the measurement point R _i is measured direction line R in the strict sense.

In determining the measurement point R _i , for example, using a distance Z between the point of interest P _i and the corresponding point Q _i , a virtual point separated from the point of interest P _i by a distance Z on the orthogonal line M. an agreement, may be determined measurement points R _i as the second trace line points closest to the virtual point. Further, when an appropriate measurement point cannot be specified, error processing may be applied. For example without determining the measurement points for the point of interest P _i, may be compensated measurement points by interpolation from a plurality of measurement points obtained in the vicinity.

  By performing the above processing with each point on the first trace line 200 as a point of interest, it is possible to determine the distance measurement direction in an appropriate direction at each coordinate in x. Of course, attention points may be determined at appropriate intervals in the x direction. It is desirable that a plurality of distance measurement directions measured at a plurality of points are displayed as lines on the display screen together with two trace lines. According to this configuration, the calculation result in the distance measurement direction can be confirmed by the user, so that the measurement reliability can be improved. In that case, it is desirable to display not all distance measuring directions but thinned out at a constant rate.

FIG. 14 shows a modification. When the second trace line portion 202A is overlaid on the first trace line portion 200A, as shown by reference numeral 208, the synthesis process may be performed so that the corresponding point Q _i overlaps the point of interest P _i. Good. The second trace line portion so shifted is indicated at 202C. In such a case, a straight line indicated by a symbol L <b> 1 is defined when a straight line approximation operation is performed after performing weighting synthesis processing. The orthogonal line M1 is determined using such an approximate straight line L1. Alternatively, the second trace line portion 202A may be used as it is without performing the superposition as described above, and the first trace line portion 202A may be weighted and synthesized. An approximate straight line generated by such processing is indicated by L2 in the figure. It may be determined orthogonal direction for the target point P _i by utilizing such approximation line L2.

  FIG. 15 is a conceptual diagram showing a specific data calculation method in the weighting synthesis process. Reference numeral 210 denotes a data string constituting the first trace line portion. Each data element is specified by an X coordinate and a Y coordinate. That is, here, the two-dimensional coordinates of each data element are specified not by the x coordinate and y coordinate based on the region of interest but by the X coordinate and Y coordinate according to the display coordinate system. The data string 210 includes data elements a1 to a8. On the other hand, reference numeral 212 indicates a data string constituting the second trace line portion. Specifically, it is composed of data elements b1 to b8. Circle symbols denoted by reference numerals 216 and 218 represent data elements employed (utilized) in the weighting synthesis process. In the data string 210, all data elements are employed, whereas in the data string 212, only every other data element is employed.

  Reference numeral 214 indicates a composite data string. In the generation of the composite data string 214, that is, the weighting synthesis process, the data elements a1 to a8 constituting the data string 210 are incorporated in the composite data string 214 as they are. On the other hand, with respect to the data string 212, only every other data element is sampled as described above, and b1, b3, b5, and b7 are extracted here. ΔX is added to the X coordinate of each data element, and ΔY is added to the Y coordinate. Incidentally, in this example, ΔX is −10.618 and ΔY is −46.726. ΔX and ΔY correspond to the shift amount in the above-described overlay synthesis. The combined data string 214 is configured by the weighted combining process as described above. Reference numeral 220 denotes a data element extracted from the data string 212 constituting the second trace line portion. A linear approximation straight line is generated based on the composite data string 214 by a known method, thereby defining a straight line serving as a reference for determining the distance calculation direction. The calculation method shown in FIG. 15 is an example, and other methods can of course be adopted.

  FIG. 16 is a flowchart showing a method for determining the distance measurement direction. First, in S700, a point of interest is specified on the first trace line. In S702, the second trace line portion included in the second trace line is synthesized with the first trace line portion included in the first trace line. Preferably, both are weighted and combined. Of course, the synthesis process may be performed on a one-to-one basis, or a large weight may be given to either. In S704, a straight line approximation calculation is executed based on the data string after the weighted synthesis process, and as a result, an approximate straight line is derived.

  In S706, an orthogonal line is calculated based on the approximate straight line. In S708, a measurement point is specified as a point on the orthogonal line or nearest to the orthogonal line. Such a measurement point is any point on the second trace line. In S710, the distance between the attention point and the measurement point is calculated. In S712, it is determined whether or not the process has been performed up to the last point on the first trace line. If the process has not been reached, the count value for specifying the point of interest is incremented in S714, and then S700. The subsequent steps are repeatedly executed. In S716, a drawing process is executed. That is, a plurality of distances measured as described above are displayed as numerical values or graphs, and a plurality of representative distance measurement lines are displayed along with two trace lines on the tomographic image.

  FIG. 17 shows an example of IMT measurement. Region of interest 216 includes inner trace line 218 and outer trace line 220. By applying the above-described method, the distance measurement direction can be set in an appropriate direction at each position in the x direction according to the form of the two trace lines 218 and 220. Reference numeral 222 indicates such a distance measuring direction.

  FIG. 18 shows an example of NT measurement (NT thickness measurement). Within the region of interest 224, an upper trace line 230 and a lower trace line 232 are included. Reference numeral 224A represents an intermediate line. By applying the method described above, it is possible to set the distance measurement direction in an appropriate direction at each coordinate in the x direction. Reference numeral 234 represents such a distance measurement direction. According to the embodiment described above, there is an advantage that the distance measurement direction can be accurately determined based on the two approximate lines defined according to the form of the two trace lines. Therefore, reproducibility can be improved and the reliability of the distance measurement result can be greatly improved. In this embodiment, since weighted synthesis is used to synthesize two trace lines, the distance measurement direction can be determined in a way that takes into account the reference trace line, that is, a trace line that is nearly flat, and thus meets the rule of thumb. It is possible to set the direction without feeling uncomfortable. Of course, the weight distribution for weighted synthesis may be set so as to be variably set by the user, or may be determined adaptively according to the curvature and the degree of curvature of each trace line. In NT measurement, when it is considered that both the upper trace line and the lower trace line are curved to the same extent, synthesis is performed at a normal one-to-one ratio instead of weighted synthesis. desirable.

  The calculation of the distance histogram will be described with reference to FIGS. Although it is possible to calculate the distance at each coordinate in the x direction by the method as described above, it is desired to express information on a number of distances obtained by them in a format that is easy for the user to understand. For this reason, in the present embodiment, a distance histogram based on relative frequency is created. In FIG. 19, reference numeral 236 indicates the distance, that is, the thickness measured on each x coordinate. The arrangement of the data corresponds to the x direction. By applying histogram processing to this data string as indicated by reference numeral 238, a distance histogram can be generated as indicated by reference numeral 240. That is, it is possible to generate a count result of the number of data for each thickness, that is, each distance. However, when such a raw distance histogram is displayed, it is expected that it will be difficult to compare with other distance histograms. Therefore, in this embodiment, the relative frequency is increased as indicated by reference numeral 242. The conversion is done. That is, as indicated by reference numeral 244, each frequency value is normalized and converted into a numerical value as a relative frequency. Here, the peak number of data is 100% relative frequency.

  FIG. 20 shows an example of a distance histogram 246 expressed as a relative frequency. The horizontal axis represents the thickness, that is, the distance, and the vertical axis represents the relative frequency. The peak corresponds to 100% or 1.0. By displaying such a graph on the screen, there is an advantage that the user can intuitively and easily grasp what distance is dominant and how the distance is distributed. Therefore, there is an advantage that new information can be provided for disease diagnosis.

  DESCRIPTION OF SYMBOLS 10 Probe, 12 Transmission part, 14 Reception part, 16 Signal processing part, 17 Image formation part, 18 Display processing part, 22 Measurement part, 30 Front wall, 32 Rear wall, 34 Blood flow part, 56,60 Region of interest, 170 Fetal cervical edema (NT), 178 Complex region of interest.

Claims (13)

Based on the tomographic image obtained by transmitting and receiving ultrasonic waves, a first trace line representing a first target boundary line in the target tissue and a second trace line representing a second target boundary line in the target tissue are generated. Boundary detection means;
On the tomographic image, an approximate straight line generating means for generating an approximate straight line based on the first trace line and the second trace line;
A distance measuring means for determining a distance measuring direction with reference to the approximate straight line, and measuring a distance between the first trace line and the second trace line;
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 1.
A region of interest setting means for setting a region of interest including the first target boundary line and the second target boundary line on the tomographic image;
At each position in the reference direction defined by the region of interest, a first line portion is referenced from among the first trace lines, and a second line portion is referenced from among the second trace lines;
The approximate line generation means sequentially generates the approximate line based on the first line portion and the second line portion at each position in the reference direction.
An ultrasonic diagnostic apparatus. The apparatus of claim 2.
The first line portion is a portion extending on both sides of the target position in the reference direction,
The second line portion is a portion corresponding to the first line portion.
An ultrasonic diagnostic apparatus. The apparatus according to claim 2 or 3,
The approximate straight line generating means includes:
Combining processing means for performing weighted combining processing based on the first line portion and the second line portion;
A computing means for computing the approximate straight line based on the result of the weighted synthesis process;
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 4.
The first trace line has a form closer to a straight line than the second trace line;
The synthesis processing unit gives a large weight to the first line portion and gives a small weight to the second line portion;
An ultrasonic diagnostic apparatus. The apparatus of claim 5.
The synthesis processing means increases the reference density for the first line portion higher than the reference density for the second line portion;
An ultrasonic diagnostic apparatus. The device according to any one of claims 1 to 6,
The distance measurement direction is an orthogonal direction orthogonal to the approximate straight line or an approximate orthogonal method approximating the orthogonal direction.
An ultrasonic diagnostic apparatus. The device according to any one of claims 2 to 7,
Display processing means for displaying a plurality of lines representing a plurality of distance measurement directions obtained for a plurality of positions in the reference direction together with the first trace line and the second trace line on the tomographic image;
An ultrasonic diagnostic apparatus. The device according to any one of claims 2 to 8,
Means for generating a distance histogram based on a plurality of distances determined for a plurality of positions in the reference direction;
The ultrasonic diagnostic apparatus, wherein the distance histogram is displayed. The apparatus of claim 9.
2. The ultrasonic diagnostic apparatus according to claim 1, wherein a horizontal axis of the distance histogram indicates a distance magnitude, and a vertical axis of the distance histogram indicates a relative frequency. Boundary detection means for generating a first trace line representing an outer boundary line in a blood vessel wall and a second trace line representing an inner boundary line in the blood vessel wall based on a tomographic image obtained by transmitting and receiving ultrasonic waves; ,
On the tomographic image, an approximate straight line generating means for generating an approximate straight line based on the first trace line and the second trace line;
A distance measuring unit that determines a distance measuring direction with reference to the approximate straight line, and measures a distance as a thickness of the blood vessel wall between the first trace line and the second trace line;
An ultrasonic diagnostic apparatus comprising: Based on tomographic images obtained by ultrasound transmission / reception, a first trace line representing the lower boundary line of fetal posterior cervical edema and a second trace line representing the upper boundary line of posterior cervical edema are generated. Boundary detection means for
On the tomographic image, an approximate straight line generating means for generating an approximate straight line based on the first trace line and the second trace line;
A distance measuring means for determining a distance measuring direction with reference to the approximate straight line, and measuring a distance as a thickness of the posterior cervical edema between the first trace line and the second trace line;
An ultrasonic diagnostic apparatus comprising: A program executed in an ultrasonic diagnostic apparatus or an information processing apparatus that processes an ultrasonic image,
A function of generating a first trace line representing a first target boundary line in the target tissue and a second trace line representing a second target boundary line in the target tissue based on the tomographic image;
On the tomographic image, a function of generating an approximate straight line based on the first trace line and the second trace line;
A function of measuring a distance between the first trace line and the second trace line by determining a distance measurement direction based on the approximate straight line;
The program characterized by including.

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