JP5660849B2 - Image processing apparatus, program, and image diagnostic apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus suitable for the left ventricular asynchronous evaluation of the heart, a program therefor, and an image diagnostic apparatus.

If there is an abnormality in the transmission of the electrical stimulation of the heart, the phenomenon that the contraction timing (timing) does not match well in at least a part of the left ventricle (asynchronous with the left ventricle) may occur, and the pump function of the heart may not be fulfilled sufficiently is there. In such a case, cardiac resynchronization therapy (CRT; Cardiac) that improves symptoms by applying electrical stimulation to the abnormal part of the heart at an appropriate timing from the outside.
Resynchronization Therapy) is known.

  However, a significant proportion of ineffective cases (non-responders) in which the effects of cardiac resynchronization therapy are not recognized have been reported. Prediction has become an important issue in cardiac resynchronization therapy.

Conventionally, as a typical method for predicting such an effective case, echocardiography, that is, tissue Doppler method or speckle tracking (speckle) using an ultrasonic diagnostic apparatus.
A method for evaluating the left ventricular asynchrony of the heart by a tracking method is known (see, for example, Patent Document 1).

Special table 2007-500550 gazette

  However, in the echocardiographic method, the accuracy of information obtained depends on the skill level of the operator, and reproducibility and objectivity are not high.

  Under such circumstances, an image processing apparatus capable of stably evaluating left ventricular asynchrony of the heart, a program therefor, and an image diagnostic apparatus are desired.

  The invention of the first aspect includes means for obtaining temporal changes in the myocardial wall thickness in a plurality of local regions of the heart based on a time-series image representing the internal structure of the heart of the subject, Image processing comprising: means for calculating an index value that reflects the degree of cardiac phase variation in which the magnitude or rate of change of the myocardial wall thickness in the plurality of local regions is a predetermined condition based on temporal changes Providing equipment.

  The invention according to a second aspect provides the image processing apparatus according to the first aspect, wherein the index value is a degree of variation in cardiac phase at which the myocardial wall thickness is maximized in the plurality of local regions.

  The invention according to a third aspect is the image processing apparatus according to the first aspect, wherein the index value is a degree of variation in cardiac phase at which a change rate in the increasing direction of the myocardial wall thickness in the plurality of local regions is maximized. provide.

  The invention according to a fourth aspect provides the image processing device according to the first aspect, wherein the index value is a degree of variation in cardiac phase at which a change rate in the decreasing direction of the myocardial wall thickness in the plurality of local regions is maximized. provide.

  According to a fifth aspect of the invention, the index value includes a degree of variation in cardiac phase at which the myocardial wall thickness is maximized in the plurality of local regions, and a rate of change in the increasing direction of the myocardial wall thickness in the plurality of local regions. At least two addition values, an average value, and a square addition value among the maximum cardiac phase variation degree and the cardiac phase variation degree in which the change rate in the decreasing direction of the myocardial wall thickness in the plurality of local regions is maximum. Or the image processing apparatus of the said 1st viewpoint which is a root mean square value is provided.

  The invention of a sixth aspect provides the image processing apparatus according to any one of the second to fifth aspects, wherein the degree of variation is a standard deviation.

  According to a seventh aspect of the invention, the plurality of local regions are at least two segments of a segment model proposed by the American Heart Association (AHA). An image processing apparatus according to any one of the above aspects is provided.

  The invention of the eighth aspect is any one of the first to seventh aspects, further comprising generating means for generating a graph representing a temporal change of the myocardial wall thickness in the plurality of local regions. An image processing apparatus according to one aspect is provided.

  The invention of the ninth aspect provides a program for causing a computer to function as the image processing apparatus according to any one of the first to eighth aspects.

  An invention of a tenth aspect includes: an imaging unit that images the subject to obtain the time-series image; and the image processing device according to any one of the first to eighth aspects. A diagnostic imaging apparatus is provided.

  The eleventh aspect of the invention provides the diagnostic imaging apparatus according to the tenth aspect, wherein the imaging means images the subject by X-ray CT (Computed tomography).

The invention according to a twelfth aspect provides the diagnostic imaging apparatus according to the tenth aspect, wherein the imaging means performs MR imaging of the subject.

  According to the invention of the above aspect, since temporal changes in the myocardial wall thickness in a plurality of local regions of the heart are obtained from time-series images, information regarding the contraction motion of the heart is accurately determined without depending on the skill level of the operator. In addition, it can be obtained with high reproducibility and objectivity. In addition, using the fact that the cardiac phase at which the myocardial wall thickness is maximum corresponds to the end systole, an index value that represents the degree of variation in the contraction timing in multiple local regions based on the temporal change in the calculated myocardial wall thickness Can be calculated. As a result, the left ventricular asynchrony of the heart can be evaluated stably.

It is a block diagram of the X-ray CT apparatus of this embodiment. It is a functional block diagram of the part which concerns on the left ventricle asynchronous evaluation process in the X-ray CT apparatus of this embodiment. It is a flowchart (flowchart) which shows the flow of the left ventricle asynchronous evaluation process by the X-ray CT apparatus of this embodiment. It is a figure which shows the 17 segment model as a some local area | region which calculates myocardial wall thickness. It is a figure which shows the example of calculation of myocardial wall thickness. It is a figure which shows the production | generation example of a time-wall thickness curve and its primary differential curve. It is a figure which shows the example of the time-wall thickness curve after an interpolation process, and the primary differential curve after an interpolation process. It is a figure explaining the definition of maximum ejection speed arrival time (TPE), end systole arrival time (TES), and maximum filling speed arrival time (TPF). It is a figure which shows the example of the display result of the graph of a time-wall thickness curve, and a left ventricular asynchronous index value.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a configuration block diagram of the X-ray CT apparatus of the present embodiment. The X-ray CT apparatus 100 includes an operation console 1, an imaging table 10, and a scanning gantry 20.

  The operation console 1 includes an input device 2 that receives input from an operator, a central processing unit 3 that executes image reconstruction processing, a data collection buffer (buffer) 5 that collects projection data acquired by the scanning gantry 20, A monitor 6 for displaying a CT image or the like reconstructed from projection data, and a storage device 7 for storing programs, data, CT images, and the like are provided.

  The imaging table 10 includes a cradle 12 on which a subject is placed and carried into and out of a bore of the scanning gantry 20. The cradle 12 is moved up and down and horizontally moved by a motor built in the imaging table 10.

The scanning gantry 20 includes an X-ray tube 21, an X-ray controller 22, a collimator 23, an X-ray detector 24, and a data acquisition unit DAS (Data
Acquisition System) 25, a rotation unit controller 26 that rotates the X-ray tube 21 and the like around the body axis of the subject, and a control controller 29 that exchanges control signals and the like with the operation console 1 and the imaging table 10. Yes.

  The configuration of the X-ray CT apparatus in this embodiment is generally as described above. In the X-ray CT apparatus having this configuration, the collection of projection data is performed as follows, for example.

  First, the position in the z direction is fixed in a state where the subject is positioned in the cavity of the rotating portion 15 of the scanning gantry 20, and the subject is irradiated with an X-ray beam from the X-ray tube 21 (X-rays). The transmitted X-rays are detected by the X-ray detector 24. Then, the transmission X-ray is detected by rotating the X-ray tube 21 and the X-ray detector 24 around the subject and collecting projection data while changing the projection angle, that is, the view angle.

Each detected transmission X-ray is converted into a digital value by the DAS 25 and transferred to the operation console 1 through the data collection buffer 5 as projection data. As a scan method, conventional scan (conventional scan)
scan), that is, an axial scan or a helical scan.

The operation console 1 stores the projection data transferred from the scanning gantry 20 in a fixed disk HDD of the central processing unit 3 and performs, for example, a predetermined reconstruction function and a superimposition operation, and performs a tomography by back projection processing. Reconstruct the image. Here, the operation console 1 receives real time (real) from the projection data sequentially transferred from the scanning gantry 20 during the scanning process.
It is possible to reconstruct a tomogram at time) and always display the latest tomogram on the monitor 6. Furthermore, it is possible to call up the projection data stored in the fixed disk HDD and to perform image reconstruction again.

  Hereinafter, the left ventricle asynchronous evaluation process in the X-ray CT apparatus of the present embodiment will be described.

  FIG. 2 is a functional block diagram of a portion related to the left ventricle asynchronous evaluation process in the X-ray CT apparatus of the present embodiment.

  The X-ray CT apparatus of the present embodiment includes a projection data collection unit 301, an image reconstruction unit 302, a myocardial contour detection unit 303, a myocardial wall thickness calculation unit 304, a graph generation unit 305, as portions related to the left ventricular asynchronous evaluation process. A specific cardiac phase detection unit 306, a local region selection unit 307, an asynchronous index calculation unit 308, and a display control unit 309 are included.

  FIG. 3 is a flowchart showing the flow of the left ventricular asynchronous evaluation process by the X-ray CT apparatus of the present embodiment. The program corresponding to this flowchart is included in the image processing program installed in the storage device 7 composed of a fixed disk (hard disk) HDD or the like, and is executed by the central processing unit 3.

  In step S1, the projection data collection unit 301 controls the scanning gantry 20 to collect projection data for the heart of the subject. In this example, a scan based on heartbeat synchronization is performed, and projection data of a plurality of views of the heart 41h is collected for about one heartbeat. The scanning method may be any method such as an axial scan or a helical scan. In the case of an axial scan, if the heart does not fit within the detector width in the z direction, the projection data of the entire heart is collected by dividing the scan range and performing a plurality of scans.

  In step S2, the image reconstruction unit 302 performs image reconstruction at a predetermined cardiac phase interval based on the projection data collected in step S1. In this example, image reconstruction of each slice of the heart 41h is performed for a total of 20 cardiac phases at intervals of 5% cardiac phase. For example, the image reconstruction is repeated while shifting the view range of the projection data to be back-projected in the view direction (time axis direction) by 5% of the cardiac phase. As a result, a total of 20 time-series three-dimensional images of the heart 41h are obtained. In general, the smaller the interval between the cardiac phases at which image reconstruction is performed, the better the accuracy of calculating the left ventricular asynchronous index value described later. However, if the interval between the cardiac phases is small, the amount of calculation becomes enormous. Therefore, considering the performance of the current computer, it is appropriate to perform image reconstruction at intervals of about 3 to 10%, for example.

  In step S3, the myocardial contour detection unit 303 detects the contour (boundary) of the myocardium for each three-dimensional image of each cardiac phase obtained in step S2. In this example, the inner wall and the outer wall of the myocardium of the heart 41h are detected as outlines for a total of 20 three-dimensional images reconstructed at intervals of 5% of the cardiac phase. As the contour detection method, a known method, for example, a method disclosed in Japanese Patent Application Laid-Open No. 08-279033 or Japanese Patent Application Laid-Open No. 06-189937 can be used.

  In step S4, the myocardial wall thickness calculation unit 304 calculates the myocardial wall thickness in a plurality of local regions of the heart for each three-dimensional image of each cardiac phase based on the myocardial contour detected in step S3. The plurality of local regions can be, for example, each segment (local region) in a 17-segment model or a 20-segment model proposed by the American Heart Association (AHA).

  In this example, the myocardial wall thickness is calculated for each local region for a total of 20 three-dimensional images reconstructed at intervals of the cardiac phase of 5%. The local region is assumed to be each segment seg1 to seg17 in the 17 segment model as shown in FIG. FIG. 4A is a polar map PM of a 17 segment model. FIG. 4B is a perspective view of the heart 41h having the long axis in the hz direction, and shows a state in which the heart 41h is divided into a plurality of segments using a 17-segment model. The first to sixth segments seg1 to seg6 correspond to the base portion side, and the seventeenth segment seg17 corresponds to the apex side. FIG. 5 shows an example of calculating the myocardial wall thickness. In this example, based on a short axis image of the heart 41h obtained from a three-dimensional image of a certain cardiac phase, the myocardial wall thicknesses WT1 to WT6 in the first to sixth segments seg1 to seg6 of the heart 41h in the cardiac phase are calculated. It shows how it is done. In FIG. 5, RV indicates the right ventricle and LV indicates the left ventricle.

  In step S5, the graph generation unit 505 generates a time-wall thickness curve and its first derivative curve for each local region based on the myocardial wall thickness of each local region in each cardiac phase obtained in step S4. . FIG. 6 shows an example of generating a time-wall thickness curve and its first derivative curve. In this example, each curve for the first to third segments seg1 is shown, but in the case of the present embodiment, each curve is actually generated for all the first to seventeenth segments.

  In step S6, the graph generation unit 505 performs interpolation processing in the time axis direction on the time-wall thickness curve generated in step S5 and its first derivative curve. The temporal change data for one heartbeat of the myocardial wall thickness calculated at intervals of about 3 to 10% of the cardiac phase is composed of ten to several tens plots. In this case, as can be seen from the example in FIG. 6, the curve is often not smooth and the time resolution is often insufficient. If this is the case, there is a possibility that a problem may occur in the calculation accuracy in the subsequent steps. Here, the continuity of data and the effective time resolution are improved by interpolation processing. The interpolation processing method may be a known interpolation method, but a non-linear interpolation method such as higher-order spline interpolation or bezier interpolation is desirable. FIG. 7 shows an example of a time-wall thickness curve after interpolation processing and a primary differential curve after interpolation processing. In FIG. 7, the data of the interval of 5% of the cardiac phase for the first to third segments seg1 are interpolated so that the number of data points, that is, the number of sampling is 20 times, and the cardiac phase is effectively 0.25. It corresponds to the data of the interval of%.

In step S7, the specific cardiac phase detection unit 506 performs the interpolated time-wall thickness curve and its first derivative curve obtained in step S6 for each of the first to seventeenth segments seg1 to seg17. Based on the maximum ejection speed arrival time (TPE; Time to peak Ejections), end-systolic arrival time (TES; Time to peak Systoles), maximum filling speed arrival time (TPF; Time
to peak Fillings). As shown in FIG. 8, TPE is the time (time phase) at which the change rate in the increasing direction of the myocardial wall thickness is maximum, that is, the time for giving the maximum peak in the first-order differential curve. TES is the time (time phase) at which the myocardial wall thickness is maximized, that is, the time for giving the maximum peak in the time-wall thickness curve. TPF is a time (time phase) at which the rate of change in the decreasing direction of the myocardial wall thickness is minimum, that is, a time for giving the minimum peak in the first-order differential curve.

  In step S8, the local region selection unit 507 selects an arbitrary segment designated by the operator as a segment for which an index value (left ventricular asynchronous index value) for evaluating left ventricular asynchrony is to be calculated as necessary. To do. However, at least two or more segments are selected. At this time, all 17 segments may be selected, or only a specific region such as a region excluding the 17th segment of the apex of the 17 segments or a so-called anterior region may be selected. As described above, by setting only a specific region as an index value calculation target, it is possible to evaluate the asynchrony of an arbitrary myocardium.

  In step S9, the asynchronous index calculation unit 308 calculates a left ventricular asynchronous index value using the segment selected in step S8 as a calculation target. Specifically, as shown in the following equations 1 to 3, a value obtained by normalizing the degree of variation between segments of TPE, TES, and TPF, for example, the standard deviation, by the RR interval (time) is calculated. By normalizing at the RR interval, an objective comparison can be made regardless of the heart rate.

  Index_TPE, Index_TES, and Index_TPF can each be independently used as a left ventricular asynchronous index value, but at least two of them, an average value, a square addition, a square average, etc., may be used as the left ventricular asynchronous index value.

  In step S10, the display control unit 309 displays on the monitor 6 the graph generated in step S6, the positions of TPE, TES, and TPF specified in step S7, and the left ventricular asynchronous index value calculated in step S9. To do.

  FIG. 9 shows an example of a display result of a time-wall thickness curve graph and a left ventricular asynchronous index value. The broken line in the figure indicates the position of TES in the time-wall thickness curve of each segment. In the example of FIG. 9, Index_TES is displayed as the left ventricular asynchronous index. Index_TES in the example of FIG. 9A is 3.3, and it is considered that the severity of left ventricular asynchronous is low. On the other hand, Index_TES in the example of FIG. 9B is 18.9, and it is considered that the severity of left ventricular asynchronous is high. Generally, if the severity of asynchronous left ventricle is low, it is likely to be an effective case with the effect of cardiac resynchronization therapy, and if the severity is high, it may be invalid to the therapy Is said to be expensive. Therefore, it is considered that whether or not the target case is an effective case can be accurately and stably predicted by referring to the left ventricular asynchronous index value calculated by the present embodiment.

  As described above, according to the present embodiment, the temporal change of the myocardial wall thickness in a plurality of local regions of the heart is obtained from the time-series images, so that information on the contraction motion of the heart can be accurately determined without depending on the skill level of the operator. In addition, it can be obtained with high reproducibility and objectivity. In addition, using the fact that the cardiac phase at which the myocardial wall thickness is maximum corresponds to the end systole, an index value that represents the degree of variation in the contraction timing in multiple local regions based on the temporal change in the calculated myocardial wall thickness Can be calculated. As a result, the left ventricular asynchrony of the heart can be evaluated stably.

  In general, as a method for knowing the contraction timing in each local region of the heart, a method for obtaining the distance from the cardiac axis to the myocardial wall can be considered. In this case, not only the myocardial wall but also the cardiac axis is detected, but it is expected that the detection accuracy is worse than that of the myocardial wall because the cardiac axis is not substantial. On the other hand, in the present embodiment, the method for obtaining the myocardial wall thickness is adopted as a method for knowing the contraction timing in each local region of the heart, so that the method for obtaining the distance from the cardiac axis to the myocardial wall is more suitable. Since the detection accuracy is good, the contraction timing can be known more accurately.

Further, as a conventional method for evaluating the left ventricular asynchrony, a method of evaluating the left ventricular asynchrony based on the temporal change of the local volume from the SPECT image of the heart is known in addition to the echocardiographic method ( For example, non-patent literature Quantification of left ventricular regional using ECG-gated
myocardial perfusion SPECT. See Ann Nucl Med 2006; 20 (7): 449-456). However, in the method using the SPECT image, the spatial resolution is low, the inspection cost by the SPECT apparatus is expensive, and the inspection facility is limited. In this embodiment, an attempt is made to evaluate left ventricular asynchrony using an X-ray CT apparatus. Considering the widespread use of X-ray CT apparatuses and cardiac CT examinations, evaluation can be performed in many facilities compared to the method using SPECT images. is there.

  In this embodiment, the left ventricular asynchronous index value is simple in both theory and calculation formula, and has high reproducibility and repeatability.

  The embodiments of the invention are not limited to the above-described embodiments, and various modifications and additions can be made without departing from the spirit of the invention.

  For example, the present embodiment is an example in which the invention is applied to an X-ray CT apparatus, but the invention can also be applied to an MR apparatus. In this case, a time-series image of the heart is acquired by MR imaging. Considering the widespread use of MR examinations and cardiac examinations using MR equipment, it is possible to evaluate in more facilities than conventional methods using SPECT images, as with X-ray CT equipment.

  Further, for example, the present embodiment is an image diagnostic apparatus including an imaging unit that obtains a time-series image of the heart, but does not include the imaging unit, and includes X-ray projection data of the heart, MR data of the heart, or heart An image processing apparatus that reads the image and calculates the left ventricular asynchronous index value by performing the above-described processing based on the data is also an embodiment of the invention. Furthermore, a program for causing a computer to function as such an image processing apparatus is also an embodiment of the invention.

DESCRIPTION OF SYMBOLS 1 ... Operation console 2 ... Input device 3 ... Central processing unit 5 ... Data collection buffer 6 ... Monitor 7 ... Storage device 10 ... Imaging table 12 ... Cradle 15 ... Rotating part 20 ... Scanning gantry 21 ... X-ray tube 22 ... X-ray controller 23 ... Collimator 24 ... X-ray detector 25 ... Data collection unit DAS
26: Rotation unit controller 29 ... Control controller 30 ... Slip ring 301 ... Projection data collection unit 302 ... Image reconstruction unit 303 ... Myocardial contour detection unit 304 ... Myocardial wall thickness calculation unit 305 ... Graph generation unit 306 ... Specific cardiac phase detection unit 307 ... Local region selection unit 308 ... Asynchronous index calculation unit 309 ... Display control unit

Claims (12)

Means for determining temporal changes in myocardial wall thickness in a plurality of local regions of the heart based on a time-series image representing the internal structure of the heart of the subject;
Means for calculating an index value representing the degree of variation in cardiac phase when the magnitude or rate of change of the myocardial wall thickness between the plurality of local regions is a predetermined condition based on the temporal change of the myocardial wall thickness An image processing apparatus.   The image processing apparatus according to claim 1, wherein the index value is a degree of variation in cardiac phase at which the myocardial wall thickness is maximized in the plurality of local regions.   The image processing apparatus according to claim 1, wherein the index value is a variation degree of a cardiac phase at which a change rate in the increasing direction of the myocardial wall thickness in the plurality of local regions is maximized.   The image processing apparatus according to claim 1, wherein the index value is a variation degree of a cardiac phase at which a change speed in a decreasing direction of the myocardial wall thickness in the plurality of local regions is maximized.   The index value is a degree of variation in cardiac phase at which the myocardial wall thickness is maximized in the plurality of local regions, and a degree of variation in cardiac phase at which the rate of change in the increasing direction of the myocardial wall thickness is maximized in the plurality of local regions. And at least two addition values, an average value, a square addition value, or a mean square value of the degree of variation in cardiac phase at which the rate of change in the decreasing direction of the myocardial wall thickness in the plurality of local regions is maximized. The image processing apparatus according to 1. The image processing apparatus according to claim 1, further comprising means for displaying the calculated index value .   The image processing apparatus according to any one of claims 1 to 6, wherein the plurality of local regions are at least two segments of a segment model proposed by the American Heart Association (AHA).   The image processing apparatus according to any one of claims 1 to 7, further comprising a generation unit configured to generate a graph representing a temporal change in myocardial wall thickness in the plurality of local regions.   The program for functioning a computer as an image processing apparatus as described in any one of Claims 1-8. Imaging means for imaging the subject to obtain the time-series image;
An image diagnostic apparatus comprising the image processing apparatus according to claim 1.   The diagnostic imaging apparatus according to claim 10, wherein the imaging unit performs X-ray CT imaging of the subject.   The diagnostic imaging apparatus according to claim 10, wherein the imaging unit performs MR imaging of the subject.

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