JP2015217113A - Blood vessel analysis device, medical image diagnostic device, blood vessel analysis method, and blood vessel analysis program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a blood vessel state in a predetermined place of a subject without invading the subject or while reducing the invasion.SOLUTION: A blood vessel analysis device includes a setting part, a first supply part, a second supply part, a calculation part, and an estimation part. The setting part sets a shape model and a load condition for a blood vessel. The first supply part supplies material dynamic information for the blood vessel. The second supply part supplies hydrodynamic information on blood flowing in the blood vessel. The calculation part extracts a first cross-sectional shape of the blood vessel from image data indicating the blood vessel of a subject, and calculates a second cross-sectional shape of the blood vessel based on the shape model, the load condition, and the material dynamic information. The estimation part estimates an index related to stenosis of the blood vessel based on the first cross-sectional shape and the hydrodynamic information when consistency between the first cross-sectional shape and the second cross-sectional shape is a predetermined threshold or more.

Description

  Embodiments described herein relate generally to a blood vessel analysis device, a medical image diagnostic device, a blood vessel analysis method, and a blood vessel analysis program.

  Conventionally, coronary artery stenosis, which is one of the three major diseases, has been diagnosed by coronary angiography (CAG) using a catheter. In addition, as a diagnostic index of an organic lesion in the coronary artery, there is a myocardial blood flow reserve ratio (FFR: Fractional Flow Reserve). FFR is defined as the ratio of the maximum coronary blood flow in the presence of stenosis to the maximum coronary blood flow in the absence of stenosis.

JP 2009-195586 A

  However, when measuring FFR using a pressure sensor provided at the catheter tip, catheter surgery is required. That is, invasion to the subject is necessary, and a burden is imposed on the subject. In addition, there is a problem that only an index based on the size of a stenosis region (for example, a plaque region or a thrombus region) can be measured from a conventional CT image of the heart. The problem to be solved by the present invention is to provide a blood vessel analyzing apparatus and a medical image diagnostic apparatus capable of estimating a state of a blood vessel in a predetermined place of a subject without invading the subject or reducing invasion. Another object is to provide a blood vessel analysis method and a blood vessel analysis program.

  The blood vessel analysis device according to the embodiment includes a setting unit, a first supply unit, a second supply unit, a calculation unit, and an estimation unit. The setting unit sets a shape model and a load condition for the blood vessel. The first supply unit supplies material mechanics information for the blood vessel. The second supply unit supplies hydrodynamic information of blood flowing in the blood vessel. The calculation unit extracts the first cross-sectional shape of the blood vessel from the image data indicating the blood vessel of the subject, and calculates the second cross-sectional shape of the blood vessel based on the shape model, the load condition, and the material dynamics information. When the consistency between the first cross-sectional shape and the second cross-sectional shape is equal to or greater than a predetermined threshold, the estimation unit estimates an index related to the stenosis of the blood vessel based on the first cross-sectional shape and the hydrodynamic information. Further, when the consistency between the first cross-sectional shape and the second cross-sectional shape is less than a predetermined threshold, the setting unit changes the setting for at least one of the shape model and the load condition to another setting.

1 is a block diagram illustrating an outline of a medical image diagnostic apparatus according to an embodiment. The functional block diagram which shows the function which the blood vessel analyzer concerning embodiment has. The flowchart which shows the operation example of the blood vessel analyzer concerning embodiment. The functional block diagram which shows the function of the modification of the blood vessel analyzer concerning embodiment. The flowchart which shows the operation example of the modification of the blood vessel analyzer concerning embodiment. The flowchart which shows the outline of the construction method of a dynamic database. The flowchart which shows the construction method of a specific mechanical database. The figure which illustrates the blood vessel which carried out circular approximation of the outer wall and the inner wall, respectively. The figure which illustrates the blood vessel which approximated the outer wall to the circle, and approximated the inner wall to the ellipse. The figure which illustrates the blood vessel which approximated the outer wall to the circle and approximated the inner wall to the polygon. The figure which illustrates the analysis screen which the medical image diagnostic apparatus concerning embodiment displays. A graph displayed by the display device to indicate the magnitude of stress at the hazardous location.

  First, the background that led to the present invention will be described. A technique for preventing or diagnosing the above-described stenosis of a coronary artery, a cerebral aneurysm, or a stenosis caused by a carotid artery plaque, which is a precursor thereof, without invading or reducing the invasion is desired.

  Coronary stenosis is a critical lesion leading to ischemic heart disease. The above-mentioned FFR substantially corresponds to the ratio of the stenosis distal coronary pressure to the stenosis proximal coronary pressure. In addition, if coronary artery stenosis analysis is possible with cardiac CT, it is possible to reduce the invasion, reduce the burden on the patient, and save medical costs, compared to FFR measurement by catheter surgery. In other words, if the pressure difference before and after stenosis can be measured by structural fluid analysis based on the CT image, the effect of stenosis can be quantified.

  Clinical evaluation of coronary circulation dynamics includes ultrafast CT, cineangiogram, ultrasound, nuclear medical imaging including SPECT (single photon emission tomography) and PET (positron emission tomography), MRI (nuclear magnetic resonance) Imaging method) has been developed and introduced, which is useful for diagnosis and evaluation of treatment methods.

  However, it is difficult to accurately capture coronary microvessels with a medical image diagnostic apparatus. Further, even if the blood vessel shape is clear, there are many cases where the medical image includes noise or there is ambiguity in the threshold setting of the boundary of the living tissue. Thus, the blood vessel shape obtained from the medical image diagnostic apparatus has uncertainty.

  When CT images are used in clinical applications, analysis is often performed only on a thick area of the coronary artery from the aortic root upstream of the coronary microvessel. Since coronary blood flow also greatly affects coronary microvascular tonicity (tonus), it is possible to appropriately set boundary conditions for fluid analysis such as flow rate, pressure, or rate of change of these at the outlet of the coronary artery in a thick region It becomes a problem.

  The blood flow in the coronary arteries is subjected to mechanical factors (total movement due to pulsation, local expansion / contraction, torsion, forced displacement or external force due to shear deformation) due to the pulsation of the heart. The fluid analysis alone cannot take into account the influence of mechanical factors such as the pulsation of the heart, and therefore cannot accurately measure the blood flow distribution and internal pressure distribution.

  On the other hand, a structure-fluid coupled analysis is also performed on the heart and vascular system captured by an image in consideration of the influence of mechanical factors. However, even when a structure-fluid coupled analysis is performed, it is often difficult to correctly set the boundary condition of the blood vessel inlet and outlet and the blood vessel and plaque material model in the blood (including the contrast medium) fluid analysis. .

  In addition, when there are micro blood vessels that are not depicted in the image, the influence of the micro blood vessels on the blood flow may not be considered. For this reason, the analysis result of the structure-fluid coupling analysis may not reproduce the actual blood flow and blood vessel deformation. In addition, when boundary conditions, load conditions, and material models are not appropriate, or when a blood vessel is accompanied by a large movement, there may be a problem in convergence and analysis stability.

  As described above, the conventional structural fluid analysis of blood vessels may require a lot of analysis resources and analysis time, and the error of the analysis result may increase. Problems may arise.

(Embodiment)
A medical image diagnostic apparatus according to an embodiment will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating an outline of a medical image diagnostic apparatus 10 according to the embodiment. The medical image diagnostic apparatus 10 is, for example, an X-ray computed tomography apparatus (X-ray CT apparatus) having a CT mount 20 and a console 30. The medical diagnostic imaging apparatus 10 may include an imaging apparatus such as a magnetic resonance diagnostic apparatus, an ultrasonic diagnostic apparatus, a SPECT apparatus, a PET apparatus, and a radiotherapy apparatus for scanning a subject.

  The CT gantry 20 includes an X-ray tube 200, an X-ray detector 202, and a data acquisition device 204. In accordance with control from the console 30, the CT gantry 20 scans the imaging region of the subject with X-rays and outputs a medical image. The imaging region is, for example, the heart and its surroundings.

  The X-ray tube 200 irradiates a subject into which a contrast medium has been injected with X-rays. The X-ray detector 202 detects X-rays irradiated by the X-ray tube 200 and transmitted through the subject, and generates an electrical signal corresponding to the detected X-ray intensity. The X-ray tube 200 and the X-ray detector 202 are mounted on the CT mount 20 so as to be rotatable around the rotation axis Z.

  The data collection device 204 reads the electrical signal generated by the X-ray detector 202 and converts it into digital data. Here, the set of digital data for each view is called a raw data set. Then, the CT gantry 20 transmits time-series raw data sets relating to a plurality of scan times to the console 30 by, for example, a non-contact data transmission device (not shown).

  The console 30 includes a gantry control unit 300, a reconstruction device 302, and a blood vessel analysis device 40. The gantry control unit 300 controls each device in the CT gantry 20 in accordance with the scanning conditions set by the user via the blood vessel analysis device 40.

  The reconstruction device 302 generates CT image data related to the subject based on the raw data set. Specifically, the reconstruction device 302 first performs preprocessing on the raw data set to generate a projection data set. The preprocessing includes logarithmic conversion, nonuniformity correction, calibration correction, and the like. Next, the reconstruction device 302 performs image reconstruction processing on the projection data set to generate CT image data. Image reconstruction algorithms include analytical image reconstruction methods such as FBP (filtered back projection) method, ML-EM (maximum likelihood expectation maximization) method, and OS-EM (ordered subset expectation maximization) method. An image reconstruction algorithm or the like is used.

  Then, the reconstruction device 302 generates time-series CT image data based on the time-series projection data set. The CT image includes a pixel region related to a blood vessel contrasted with a contrast agent (hereinafter referred to as a blood vessel region). Note that the CT image may be slice data representing a two-dimensional spatial distribution of CT values, or volume data representing a three-dimensional spatial distribution of CT values. Hereinafter, it is assumed that the CT image is volume data.

  The blood vessel analysis device 40 includes a system control unit 400, an image processing device 402, an input device 404, a display device 406, and a storage device 408. The blood vessel analysis device 40 is a computer device that performs blood vessel stenosis analysis on a blood vessel region included in a medical image output from the CT mount 20. The blood vessel analysis device 40 is not limited to being incorporated in the medical image diagnostic apparatus 10, and may be a computer device such as a workstation separate from the medical image diagnostic apparatus 10. When the blood vessel analyzing apparatus 40 is separate from the medical image diagnostic apparatus 10, the blood vessel analyzing apparatus 40 collects medical data such as time-series CT images from the medical image diagnostic apparatus 10 or PACS (picture archiving and communication systems) via a network. .

  The system control unit 400 includes a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM) (not shown). The system control unit 400 executes a blood vessel stenosis analysis process by executing a blood vessel analysis program stored in a ROM or RAM, and controls each part of the medical image diagnostic apparatus 10.

  The image processing apparatus 402 performs a blood vessel stenosis analysis described later together with the system control unit 400 based on the time-series CT images. The input device 404 is, for example, a keyboard, a mouse, a switch, and the like, and accepts various instructions and information input from the user. The display device 406 is, for example, a CRT display, a liquid crystal display, an organic EL display, or a plasma display, and displays various information such as a CT image and a structural fluid analysis result described later.

  The storage device 408 includes various storage media such as a hard disk device. The storage device 408 stores various data such as time-series projection data and time-series CT image data. For example, the storage device 408 stores time-series CT image data in a medical image file format conforming to the DICOM (digital imaging and communications in medicine) standard. The storage device 408 may store the medical data collected by the external device in association with the time-series CT image data in the medical image file.

  Next, functions of the blood vessel analysis device 40 will be described. FIG. 2 is a functional block diagram illustrating functions of the blood vessel analysis device 40. As shown in FIG. 2, the blood vessel analysis device 40 includes an acquisition unit 50, a calculation unit 51, a setting unit 52, a first database (DB) 53, a shape determination unit (first determination unit) 54, a stenosis analysis unit (estimation unit). ) 55, second database (DB) 56, and display control unit (output unit) 57. Note that part or all of the functions of the blood vessel analysis device 40 shown in FIG. 2 may be configured by hardware, or may be configured by software as a blood vessel analysis program. The blood vessel analysis program executed by the blood vessel analysis device 40 is a computer program written in a computer-readable storage medium such as a CD-ROM or a DVD in a file in an installable or executable format. -It may be provided as a product.

  The acquisition unit 50 acquires, for example, 4D image data of blood vessels (data indicating volume data expressing a three-dimensional spatial distribution of CT values in time series) from the storage device 408. The acquisition unit 50 may have a function of generating 4D image data that can be subjected to blood vessel analysis.

  First, the calculation unit 51 extracts the cross-sectional shape (first cross-sectional shape) of the blood vessel based on the 4D image data of the blood vessel acquired by the acquisition unit 50. For example, based on the 4D image data of the blood vessel, the calculation unit 51 is a cross-sectional index (predetermined from the coronary artery starting portion) that indicates a change in the cross-sectional shape of the blood vessel from the time of expansion of the coronary artery to the time of contraction or from the time of contraction to the time of expansion. The aortic blood vessel cross-section at the distance position and the blood vessel cross-sectional index around the coronary artery analysis target outlet are extracted.

  As a specific example, the cross-sectional index indicating the change in the cross-sectional shape of the coronary artery includes, for example, the coefficient of variation (standard deviation as an average value) of the vascular lumen cross-sectional area from the time of coronary vasodilation to the time of contraction (cardiac phase 70 to 100%). Divided value). Here, the cardiac phase is assumed to be in the range of 0 to 100%. In addition, the cross-sectional index indicating the change in the cross-sectional shape of the aorta includes the temporal change rate and amount of change in the cross-sectional area average of a plurality of cross-sections slightly above the origin of the coronary artery (about several centimeters), and the time from vasodilation to contraction The coefficient of variation of (cardiac phase 70 to 100%) can be mentioned. The calculation unit 51 is not the cross-sectional area, but the temporal change rate or amount of change in the volume of the blood vessel lumen in consideration of the change in the cross-sectional area of the blood vessel in the core line direction, or the time from vascular dilation to contraction (cardiac phase 70 to 100%) ) May be used as an index.

  Next, the calculation unit 51 accepts values set by the setting unit 52 (cross-sectional shape model and load conditions, which will be described later), and collates the material dynamics information supplied by the first DB 53 to thereby determine the blood vessels under the set load conditions. The cross-sectional shape (second cross-sectional shape) is calculated.

  The setting unit 52 sets, for the calculation unit 51, a cross-sectional shape model of a blood vessel in a stress-free state, a load condition on the blood vessel, and the like according to information input by the user via the input device 404.

  The first DB 53 supplies (provides) material dynamics information for a blood vessel (for example, a coronary artery) to the calculation unit 51 in response to a request from the calculation unit 51. For example, the first DB 53 is a pre-built material mechanical database of blood vessels. Material mechanics information for blood vessels is derived from, for example, a cross-sectional shape model of a blood vessel in an unstressed state, a blood vessel material model (anisotropic hyperelastic material, etc.), a load pressure on the blood vessel, and a relational model of the cross-sectional shape when the blood pressure is applied Composed.

  The first DB 53 only needs to have a function as a first supply unit that supplies (provides) blood vessel material dynamics information to the calculation unit 51 in response to a request from the calculation unit 51. For example, the first DB 53 is not limited to being a database, and may be configured to calculate material mechanics information and supply the calculation unit 51 by calculation based on a predetermined model.

  The shape determination unit 54 has consistency between the cross-sectional shape of the blood vessel (first cross-sectional shape) based on the 4D image data acquired by the acquisition unit 50 and the cross-sectional shape of the blood vessel under the set load condition (second cross-sectional shape). The quality is determined using, for example, a predetermined threshold value. Then, when the consistency between the first cross-sectional shape and the second cross-sectional shape is not good (when the consistency is less than the threshold value), the shape determining unit 54 sends the cross-sectional shape model of the blood vessel in a stress-free state to the setting unit 52. And reset the loading condition on the blood vessel.

  On the other hand, when the consistency between the first cross-sectional shape and the second cross-sectional shape is good (when the consistency is equal to or greater than a threshold value), the shape determining unit 54 determines, for example, the first cross-sectional shape, the second cross-sectional shape, and the load condition. Based on the stenosis analysis (estimation of an index related to stenosis), the stenosis analysis unit 55 is caused to execute.

  The stenosis analyzing unit 55 supplies the first cross-sectional shape and the second cross-sectional shape determined by the shape determining unit 54 that the consistency is good, the cross-sectional shape model of the blood vessel without stress, the load condition on the blood vessel, and the second DB 56 supplies By collating with the hydrodynamic information, for example, the blood flow rate is calculated, and stenosis analysis (estimation) is performed.

  More specifically, the stenosis analysis unit 55 uses, for example, blood flowing in the blood vessel as a fluid, and extracts an index (blood flow index) indicating blood flow resistance such as a relationship between the pressure loss and the flow rate of the coronary artery, for example. The stenosis is analyzed and, for example, FFR is estimated. Here, the stenosis analysis unit 55 performs a coupled analysis based on material dynamics information and fluid dynamics information. Further, the stenosis analysis unit 55 may estimate a pressure distribution indicating a degree of stenosis (degree of blood flow inhibition), a flow rate distribution, and the like. The stenosis analysis unit 55 estimates the stenosis as follows: blood flow changes and pressure changes during dilation and contraction, pressure loss before and after stenosis, pressure loss between the aorta and coronary artery, each coronary artery (coronary artery with stenosis) And the flow rate ratio of the coronary artery without stenosis). Here, the stenosis analysis unit 55 may be configured to determine each state in the blood vessel based on, for example, whether or not the index exceeds a predetermined threshold.

  In response to a request from the stenosis analysis unit 55, the second DB 56 supplies (provides) hydrodynamic information regarding blood flowing in a blood vessel (for example, a coronary artery) to the stenosis analysis unit 55. For example, the second DB 56 is a pre-built hydrodynamic database of blood. The hydrodynamic information for blood flowing through a blood vessel is composed of, for example, a blood vessel shape model (including a stenosis) and a relationship model between pressure loss and flow rate before and after stenosis.

  The second DB 56 only needs to have a function as a second supply unit that supplies (provides) blood hydrodynamic information to the stenosis analysis unit 55 in response to a request from the stenosis analysis unit 55. For example, the second DB 56 is not limited to being a database, and may be configured to calculate hydrodynamic information and supply it to the stenosis analysis unit 55 by calculation based on a predetermined model.

  The display control unit 57 causes the display device 406 to display the result estimated by the stenosis analysis unit 55. That is, the display control unit 57 is an output unit that outputs the result estimated by the stenosis analysis unit 55.

  Next, an operation example of the blood vessel analysis device 40 will be described. The medical image diagnostic apparatus 10 can analyze blood vessels of a subject such as a human body, and blood vessels of all parts such as a carotid artery and a cerebral artery. Is a blood vessel around the heart.

  Examples of blood vessels around the heart include coronary arteries and aorta. The coronary artery starts from the coronary artery origin of the aorta, travels on the myocardial surface, and enters the intima side from the epicardium side. The coronary arteries branch into myriad capillaries in the intima of the myocardium. The myriad of branched capillaries reintegrate to form the great cardiac vein and are connected to the coronary sinus. Unlike other organs, the coronary vasculature is unique in that perfusion must be guaranteed in the course of mechanical changes such as myocardial contraction and relaxation.

  A feature of coronary blood flow is that it flows more when the perfusion pressure decreases in the left ventricular diastole than in the systole where the internal pressure at the coronary artery origin increases due to the mechanical blood flow inhibition effect due to myocardial contraction. Therefore, the normal coronary blood flow velocity waveform has a bimodality that peaks in the systole and the diastole, and the diastolic blood flow is dominant. In addition, it is known that retrograde waves are observed during systole in hypertrophic cardiomyopathy and aortic stenosis, and that systolic antegrade waves increase in aortic regurgitation. Yes. In addition, the antegrade waveform in the diastole is closely related to the left ventricular dilation function, particularly the left ventricular relaxation. In the left ventricular relaxation delay example, the peak of the diastolic waveform shifts backward, and the deceleration leg tends to be gradual. In such cases, the coronary blood flow during diastole cannot be increased sufficiently during tachycardia, which is thought to promote myocardial ischemia.

  Anatomically, coronary blood flow is generated by applying coronary perfusion pressure equal to the aortic pressure (that is, the pressure of the aortic root where the coronary artery branches) to the left and right coronary arteries that branch from the aortic root. Coronary blood flow resistance as well as driving pressure, which is aortic pressure, is important for determining coronary blood flow. A thick coronary vessel of 140 to 180 μm or more has about 20% of the resistance to coronary vessels, whereas a microvessel of 100 to 150 μm or less is said to have a lot of remaining resistance components. Therefore, in the case where there is no so-called coronary stenosis, the resistance value depends on the tonicity of coronary microvessels.

  Vascular resistance factors include vascular properties, arteriosclerosis, vascular stenosis, blood viscosity, and mechanical factors. Coronary microvessel tonus is defined by vascular properties, myocardial metabolism (myocardial oxygen consumption), neurohumoral factors, mechanical factors, various vasoactive substances as humoral factors, blood viscosity, cardiac hypertrophy, coronary artery Coronary circulatory disturbance is caused by various lesions including sclerosis.

  Coronary blood flow pulsation is affected by the pulsation pattern of coronary blood flow, the control of intramyocardial blood flow by myocardial contraction, and the intramyocardial vascular response to mechanical stimulation. The mechanism by which myocardial contraction inhibits blood flow includes an increase in intramyocardial pressure, changes in intramyocardial vascular volume, and compression of intramyocardial blood vessels. The blood flow regulating factor in the myocardial diastole includes diastole coronary artery pressure, diastole extravascular force, heart rate, ratio of diastole to cardiac cycle, and myocardial relaxation.

  FIG. 3 is a flowchart showing an operation example of the blood vessel analysis device 40. As shown in FIG. 3, in step 100 (S100), the acquisition unit 50 acquires blood vessel medical image information (blood vessel 4D image data).

  In step 102 (S102), the calculation unit 51 extracts the cross-sectional shape (first cross-sectional shape) of the blood vessel based on the 4D image data of the blood vessel acquired by the acquisition unit 50.

  In step 104 (S104), the setting unit 52 sets the cross-sectional shape model of the blood vessel in a stress-free state in the calculation unit 51.

  In step 106 (S106), the setting unit 52 sets a load condition for the blood vessel in the calculation unit 51.

  In step 108 (S108), the calculation unit 51 calculates the cross-sectional shape (second cross-sectional shape) of the blood vessel under the set load condition by collating the material dynamics information supplied by the first DB 53.

  In step 110 (S110), the shape determination unit 54 determines whether or not the consistency between the first cross-sectional shape and the second cross-sectional shape is good. If the consistency between the first cross-sectional shape and the second cross-sectional shape is not good (S110: No), the shape determining unit 54 returns to the process of S104. In addition, when the consistency between the first cross-sectional shape and the second cross-sectional shape is good (S110: Yes), the shape determination unit 54 proceeds to the process of S112.

  In step 112 (S112), the stenosis analysis unit 55 calculates the blood flow rate.

  In step 114 (S114), the stenosis analysis unit 55 performs stenosis index derivation (stenosis analysis) based on the calculated blood flow rate.

(Modification)
FIG. 4 is a functional block diagram illustrating functions of a modification of the blood vessel analysis device 40. As shown in FIG. 4, the modified example of the blood vessel analysis device 40 includes an acquisition unit 50, a calculation unit 51, a setting unit 52, a first database (DB) 53, a shape determination unit (first determination unit) 54, and a stenosis analysis unit. (Estimation unit) 55a, second database (DB) 56, display control unit (output unit) 57, and third database (DB) 58. 4 that are substantially the same as the constituent parts of the blood vessel analysis device 40 shown in FIG. 2 among the constituent parts of the modified example of the blood vessel analysis device 40 shown in FIG.

  The stenosis analysis unit (estimation unit) 55a includes a flow rate determination unit (second determination unit) 550, and performs contrast analysis (estimation) by collating contrast agent concentration information (concentration relation information) supplied by the third DB 58. Do. The flow rate determination unit 550 includes the blood flow rate and flow rate ratio (first flow rate information) based on the 4D image data acquired by the acquisition unit 50, and the blood flow rate and flow rate ratio (second flow rate information) under the set load conditions. Is determined using, for example, a predetermined threshold value.

  Then, when the consistency between the first flow rate information and the second flow rate information is not good (when the consistency is less than the threshold value), the flow rate determination unit 550 causes the setting unit 52 to display a cross-sectional shape model in a stress-free state of the blood vessel. And reset the loading condition on the blood vessel. When the flow rate determination unit 550 determines that the consistency between the first flow rate information and the second flow rate information is good (consistency is equal to or greater than a threshold value), the stenosis analysis unit 55a, for example, includes the first flow rate information and the second flow rate information. Perform stenosis analysis (estimation) based on flow rate information and load conditions.

  In response to a request from the stenosis analysis unit 55a, the third DB 58 supplies (provides) contrast medium concentration information (concentration relationship information) in the blood vessel to the stenosis analysis unit 55a. For example, the third DB 58 is a contrast agent concentration information (concentration relationship information) database constructed in advance. The contrast agent concentration information is composed of, for example, a relational model of CT value temporal and spatial changes (concentration changes), flow rate and flow velocity, blood vessel shape, and contrast agent concentration.

  Note that the third DB 58 may have a function as a third supply unit that supplies (provides) contrast medium concentration information to the stenosis analysis unit 55a in response to a request from the stenosis analysis unit 55a. For example, the third DB 58 is not limited to being a database, and may be configured to calculate contrast medium concentration information and supply it to the stenosis analysis unit 55a by a calculation based on a predetermined model.

  FIG. 5 is a flowchart showing an operation example of a modified example of the blood vessel analysis device 40. Of the operations of the modified example of the blood vessel analysis device 40 shown in FIG. 5, substantially the same operations as those of the blood vessel analysis device 40 shown in FIG. 3 are denoted by the same reference numerals.

  In step 116 (S116), the flow rate determination unit 550 determines whether or not the consistency between the first flow rate information and the second flow rate information is good. When the consistency between the first flow rate information and the second flow rate information is not good (S116: No), the flow rate determination unit 550 returns to the process of S104. Moreover, the flow volume determination part 550 advances to the process of S118, when the consistency of 1st flow volume information and 2nd flow volume information is good (S116: Yes).

  In step 118 (S118), the stenosis analysis unit 55a performs stenosis index derivation (stenosis analysis) based on the calculated blood flow rate. That is, the stenosis analysis unit 55a can reduce the uncertainty of the blood flow rate by using the contrast medium concentration information even when the uncertainty of the blood flow rate calculated in the process of S112 is high.

  Next, a method for constructing the above-described mechanical database will be described. FIG. 6 is a flowchart showing an outline of a method for constructing a mechanical database. When constructing a mechanical database, first, a mechanical analysis model of blood vessels is constructed (S200).

  Then, an analysis condition parameter is set (S202), and a mechanical analysis model in which the analysis condition parameter is set is analyzed (S204).

  Further, the analysis result is extracted (S206), and it is determined whether or not there is a satisfactory number of analysis results as a database (S208). If there is no satisfactory number of analysis results as a database (S208: No), the process returns to S200. If there is a satisfactory number of analysis results as a database (S208: Yes), the process proceeds to S210.

  Then, a statistical model, mathematical model, and probability model are constructed using a sufficient number of analysis results (S210).

  Next, a specific method for constructing a dynamic database will be described using an example. FIG. 7 is a flowchart showing a specific method for constructing a dynamic database. FIG. 8 is a diagram illustrating blood vessels in which the outer wall and the inner wall are approximated by circles, respectively.

In the blood vessel shown in FIG. 8, R ₀ , x ₀ , y ₀ and r ₀ are set as shape parameters. R ₀ indicates the radius of the blood vessel outer wall in an unstressed state. x ₀ indicates the x coordinate of the center of the circle. y ₀ indicates the y coordinate of the circle center. R ₀ represents the radius of the inner wall of the blood vessel in the unstressed state.

Here, in order to construct a mechanical analysis model of a blood vessel, first, the radius R ₀ of the outer wall of the blood vessel is set, and the center coordinates (x ₀ , y ₀ ) of the inner wall are set so as to satisfy the following expression 1.

Thereafter, the inner wall radius r ₀ is set so as to satisfy the following expression 3 using the following expression 2 indicating the distance between the centers of the circles.

As material parameters, E (Young's modulus) and ν (Poisson's ratio) are determined in the case of a linear material, and anisotropic superelastic material parameters C _{1 to} C _n are set in the case of an anisotropic superelastic material. Yes. Also, as the boundary and load condition parameters, p _in , p _out , F _z , M ₁ , and M ₂ are set. p _in shows the internal pressure. p _out indicates an external pressure. F _z indicates the load of the core wire direction. M ₁ represents a load in the direction of bending the core wire. M ₂ represents a load in the direction of twisting the cylinder.

  When constructing a mechanical database, first, as shown in FIG. 7, the blood vessel shape parameters are set (S300). Next, a mechanical analysis model for blood vessels is constructed (S302).

Further, the blood vessel material parameters (E, ν, or C _{1 to} C _n ) are set (S304), and the boundary and load condition parameters (p _in , p _out , F _z , M ₁ , M ₂ ) are set (S306). ).

Then, the mechanical analysis model in which the analysis condition parameter is set is analyzed (S308). Further, the analysis result (ε _r ) is extracted (S310), and it is determined whether or not there is a satisfactory number of analysis results as a database (S312). If there is not a sufficient number of analysis results as a database (S312: No), the process returns to S300. When there are a sufficient number of analysis results as a database (S312: Yes), a sufficient number of analysis results are used to construct a statistical model, a mathematical model, and a probability model (S314).

  In order to repeat a series of analysis, it is efficient to prepare an analysis that uses each parameter as an analysis parameter, and a script that can extract the result without user operation. Statistical models, mathematical models, and probabilistic models can be constructed.

Note that the method of approximating the shape of the blood vessel is not limited to the circle approximation shown in FIG. FIG. 9 is a diagram illustrating a blood vessel in which the outer wall is approximated by a circle and the inner wall is approximated by an ellipse. In the blood vessel shown in FIG. 9, R ₀ , x ₀ , y ₀ , a ₀ and b ₀ are set as shape parameters. R ₀ indicates the radius of the blood vessel outer wall in an unstressed state. x ₀ denotes the x-coordinate of the ellipse center. y ₀ represents the y coordinate of the ellipse center. a ₀ represents the short radius of the inner wall of the blood vessel in the unstressed state. b ₀ indicates the long radius of the inner wall of the blood vessel in the unstressed state. The material parameters, boundaries, and load condition parameters are the same as in the example shown in FIG.

Here, assuming that the equation of the circle with the radius R ₀ centered at the origin is the following equation 4, the equation of the ellipse with the short radius a ₀ and the major radius b ₀ centered on (x ₀ , y ₀ ) is As shown.

  The elliptic equation is also expressed by the following equations 6 and 7 using the elliptical parameter θ.

  Therefore, in order for an ellipse indicating the inner wall to be included in a circle indicating the outer wall, the following equation 8 may be established for an arbitrary θ.

That is, the radius R ₀ of the outer wall of the blood vessel is set, the center coordinates (x ₀ , y ₀ ) of the inner wall are set so as to satisfy the following equation 9, and the elliptical shape is satisfied so as to satisfy the following equation 10 for an arbitrary θ. A short radius a ₀ and a long radius b ₀ are set. As described above, the material parameters, boundaries, and load condition parameters are the same as those in the example shown in FIG.

FIG. 10 is a diagram illustrating a blood vessel in which the outer wall is approximated by a circle and the inner wall is approximated by a polygon. In the blood vessel shown in FIG. 10, R ₀ , x ₀ , y ₀ , and b _{1 to} b _n are set as shape parameters. R ₀ indicates the radius of the blood vessel outer wall in an unstressed state. x ₀ indicates the x coordinate of the starting point of the polygon. y ₀ indicates the y coordinate of the starting point of the polygon. b _{1 to} b _n are vectors connecting from the starting point of the polygon to each vertex. The material parameters, boundaries, and load condition parameters are the same as in the example shown in FIG.

Here, the radius R ₀ of the outer wall of the blood vessel is set, and the coordinates (x ₀ , y ₀ ) of the starting point of the polygon of the inner wall are set so as to satisfy the following expression 11.

When the vectors b _{1 to} b _n from the polygon starting point to the polygon vertex are components b ₁ = (x ₁ , y ₁ ),..., B _n = (x _n , y _n ), respectively. The vector components from the origin to the vertex of the polygon are shown as (x ₀ + x ₁ , y ₀ + y ₁ ) to (x ₀ + x _n , y ₀ + y _n ), respectively.

Therefore, the lengths of the vectors from the origin to the vertexes of the polygon are respectively expressed by the following expressions 12 to 13, and (x ₁ , y ₁ ) to (x _n , y _n ) so that all vectors are smaller than R _0. ) Is set. As described above, the material parameters, boundaries, and load condition parameters are the same as those in the example shown in FIG.

  Next, an operation example of the input device (input unit) 404 and the display device 406 in the medical image diagnostic apparatus 10 will be described. FIG. 11 is a diagram illustrating an analysis screen 60 displayed on the display device 406 after the medical image diagnostic apparatus 10 performs the stenosis analysis of the blood vessel. The display device 406 displays the analysis screen 60 as shown in FIG. 11 after the medical image diagnostic apparatus 10 performs the stenosis analysis of the blood vessel.

  The analysis screen 60 includes a position display unit 62, a parameter display unit 64, a first analysis output unit 66, and a second analysis output unit 68. The position display unit 62 moves the cross-section position display 622 in accordance with drag and drop using the cursor 620 by the user's operation input via the input device 404, thereby analyzing the analysis position in the blood vessel (for example, coronary artery). Display to identify (cross-sectional position).

  The parameter display unit 64 displays an indeterminate range of each parameter (stressless shape, material physical property, inlet boundary condition, outlet boundary condition, load condition) for the blood vessel as a bar. The bar indicating each parameter is provided with a level display 640 indicating the set level. When any one of the level displays 640 is moved by the cursor 642 in response to a user operation input via the input device 404, the parameter display unit 64 also interlocks with the level display 640 of other correlated parameters. To move.

  The parameter display unit 64 may display all parameter bars, or may display only the bars required by the user. Further, the parameter display unit 64 may be configured such that parameters are input as numerical values via a keyboard or the like and numerical values are displayed. The name of the bar may be a specialized expression or an expression that is easy for the user to understand. For example, the name of the bar may collectively represent Young's modulus, Poisson's ratio, and unstressed shape parameters as “blood vessel stiffness”.

  The first analysis output unit 66 displays a contour diagram (estimated stress or the like) of the cross section of the blood vessel at the position specified by the position display unit 62 according to the parameter before the cursor 640 is moved (one time before). For example, the first analysis output unit 66 displays a region a where the stress is normal, a region b where the stress is strong, a dangerous location c, and the like. Further, in the first analysis output unit 66, for example, when the dangerous part c is clicked, a graph indicating the magnitude of stress at the dangerous part shown in FIG. A cursor 660 is also provided.

  The second analysis output unit 68 generates a contour diagram (estimated stress or the like) of the cross section of the blood vessel at the position specified by the position display unit 62 according to the parameter after the parameter cursor 640 in the parameter display unit 64 is moved. indicate. For example, the second analysis output unit 68 displays a region a where the stress is normal, a region b where the stress is strong, a dangerous location c, and the like in the setting after the parameter change. The second analysis output unit 68 also has a cursor 680 for causing the display device 406 to display a graph indicating the magnitude of stress at the dangerous location (stress exceeding the critical threshold) when the dangerous location c is clicked, for example. Is also provided.

  The analysis screen 60 is not limited to displaying all of the position display unit 62, the parameter display unit 64, the first analysis output unit 66, and the second analysis output unit 68, but displays a part thereof. There may be. Further, the analysis screen 60 may be used for a simulation when a blood vessel is treated with, for example, a balloon or a stent, or a simulation of the progression of arteriosclerosis.

  As described above, the blood vessel analysis device 40 extracts the first cross-sectional shape of the blood vessel from the image data indicating the blood vessel of the subject, and calculates the second cross-sectional shape of the blood vessel based on the shape model, the load condition, and the material dynamics information. When the consistency between the first cross-sectional shape and the second cross-sectional shape is equal to or greater than a predetermined threshold value, the index regarding the stenosis of the blood vessel is estimated based on the first cross-sectional shape and the hydrodynamic information. The state of the blood vessel at a predetermined location of the subject can be estimated without doing this or while reducing the invasion.

  The blood vessel analysis device 40 is also provided with the following input / output device.

  Input of information indicating position information for identifying a position in an analysis object whose shape changes while flowing a fluid therein, material dynamics information for the analysis object, and parameters for at least one of fluid dynamics information for the fluid And an output unit that outputs a result of estimating an index indicating the state of the analysis object by the estimation unit based on the material dynamics information, the fluid dynamics information, and the information received by the input unit. And an input / output device.

  Moreover, although several embodiment of this invention was described by several combination, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Medical diagnostic imaging apparatus 20 CT mount 200 X-ray tube 202 X-ray detector 204 Data acquisition apparatus 30 Console 300 Mount control part 302 Reconstruction apparatus 40 Blood vessel analysis apparatus 400 System control part 402 Image processing apparatus 404 Input apparatus 406 Display apparatus 408 Storage device 50 Acquisition unit 51 Calculation unit 52 Setting unit 53 First DB
54 Shape determination unit 55, 55a Stenosis analysis unit 56 2nd DB
57 display control unit 58 third DB
60 Analysis screen

Claims (10)

A setting unit for setting a shape model and a load condition for a blood vessel;
A first supply for supplying material mechanics information for the blood vessel;
A second supply for supplying hydrodynamic information of blood flowing in the blood vessel;
Extracting a first cross-sectional shape of a blood vessel from image data indicating a blood vessel of a subject, and calculating a second cross-sectional shape of the blood vessel based on the shape model, the load condition, and the material dynamics information;
An estimation unit that estimates an index related to stenosis of a blood vessel based on the first cross-sectional shape and the hydrodynamic information when the consistency between the first cross-sectional shape and the second cross-sectional shape is equal to or greater than a predetermined threshold; ,
Have
The setting unit
A blood vessel analyzer that changes a setting for at least one of the shape model and the load condition to another setting when the consistency between the first cross-sectional shape and the second cross-sectional shape is less than a predetermined threshold. The first supply unit includes:
Supplying the material mechanics information by a first database constructed in advance;
The second supply unit includes:
The blood vessel analysis device according to claim 1, wherein the hydrodynamic information is supplied by a second database that is built in advance. The first supply unit includes:
Calculate and supply the material mechanics information by an operation based on a predetermined first model,
The second supply unit includes:
The blood vessel analysis device according to claim 1, wherein the hydrodynamic information is calculated and supplied by a calculation based on a predetermined second model. The estimation unit includes
The blood vessel analysis device according to any one of claims 1 to 3, wherein an index related to stenosis of a blood vessel is estimated by performing a coupled analysis based on the material dynamics information and the fluid dynamics information. A third supply unit for supplying density relationship information indicating a relationship between the density of the image data and the cross-sectional shape of the blood vessel and the flow rate of blood flowing in the blood vessel;
The estimation unit includes
The blood vessel analyzer according to any one of claims 1 to 4, wherein an index related to stenosis of a blood vessel is estimated based on the concentration relationship information. The first supply unit includes:
Providing the material mechanics information for the coronary artery,
The second supply unit includes:
Providing the hydrodynamic information for the coronary artery,
The calculation unit includes:
Extracting the first cross-sectional shape for the aorta and coronary artery at a predetermined position from the coronary artery origin,
The estimation unit includes
The blood vessel analyzer according to any one of claims 1 to 5, wherein an index relating to stenosis of a coronary artery is estimated. Position information for specifying the position of a blood vessel to be analyzed with respect to the image data, and an input unit that receives input of information indicating a parameter for at least one of the material dynamics information and the fluid dynamics information;
An output unit that outputs a result estimated by the estimation unit based on information received by the input unit;
The blood vessel analyzer according to any one of claims 1 to 6, further comprising: An imaging device that generates the image data by imaging a blood vessel of a subject;
A medical image diagnostic apparatus comprising: the blood vessel analyzer according to any one of claims 1 to 7. Setting a shape model and load conditions for the blood vessel;
Extracting a first cross-sectional shape of a blood vessel from image data indicating a blood vessel of a subject, and calculating a second cross-sectional shape of the blood vessel based on the shape model, the load condition, and material dynamics information for the blood vessel;
When the consistency between the first cross-sectional shape and the second cross-sectional shape is less than a predetermined threshold, changing the setting for at least one of the shape model and the load condition to another setting;
When consistency between the first cross-sectional shape and the second cross-sectional shape is equal to or greater than a predetermined threshold, an index related to stenosis of the blood vessel is estimated based on the first cross-sectional shape and hydrodynamic information of blood flowing in the blood vessel. A blood vessel analysis method comprising the steps of: Setting a shape model and loading conditions for the blood vessel;
Extracting a first cross-sectional shape of a blood vessel from image data indicating a blood vessel of a subject, and calculating a second cross-sectional shape of the blood vessel based on the shape model, the load condition, and material dynamics information for the blood vessel;
When the consistency between the first cross-sectional shape and the second cross-sectional shape is less than a predetermined threshold, changing the setting for at least one of the shape model and the load condition to another setting;
When consistency between the first cross-sectional shape and the second cross-sectional shape is equal to or greater than a predetermined threshold, an index related to stenosis of the blood vessel is estimated based on the first cross-sectional shape and hydrodynamic information of blood flowing in the blood vessel. And steps to
Is a blood vessel analysis program for causing a computer to execute.

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