JP3449810B2 - Blood flow information display method - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] Field of the Invention The present invention is a blood vessel image search of three-dimensional bloodstream data for three orthogonal axial Diagnosis sites Oite subject to magnetic resonance imaging apparatus The present invention relates to a blood flow information display method to be displayed, and more particularly, to a blood flow information display method capable of displaying a continuous blood flow information together with a two-dimensional projected image of a diagnosis site. [0002] using the conventional magnetic resonance imaging apparatus to detect blood flow three orthogonal axial about a region to be diagnosed in the subject has been detected by the pulse sequence shown in FIG. 6 . FIG. 6 schematically shows this pulse sequence. In an actual operation, a positive flow encode pulse (hereinafter, referred to as a positive electrode) indicated by a solid line on each axis of the slide direction Gs, the phase encode direction Gp, and the frequency encode direction Gf. (Reference FE pulses) to which G.sub.p and G.sub.f have positive polarity FE pulses shown by solid lines, and G.sub.s a negative flow encode pulse (hereinafter called "negative FE pulses") shown by broken lines. The added sequence (S-axis flow encode) Gs, Gf is a positive FE pulse indicated by a solid line, and the Gp is a sequence (P-axis flow encode) Gs, Gp added a negative FE pulse indicated by a dashed line. The positive FE pulse shown is
Four types of sequences (F-axis flow encode) in which a negative FE pulse indicated by a two-dot chain line is added to Gf are sequentially repeated. At this time, when detecting the blood flow of only two axes or one axis, one or two of the above-mentioned sequences may not be operated. [0003] As described above, it is possible to detect each blood flow signal in the three orthogonal axes. However, considering the case of obtaining a three-dimensional blood vessel image, all blood flows flowing in an arbitrary direction are considered. Need to be displayed in one image. FIG. 7 shows this procedure. FIG. 7 shows a P axis (phase axis) flow encode image I ₁ and an F axis (frequency axis).
Shows the synthesis of two axial directions of the image flow encode image I _2, the same applies to the three axial directions. The vector synthesis (square root of the sum of squares) of the P- and F-axis absolute value image data obtained by the complex difference with the reference image I ₃ , that is, the P-axis difference image I ₄ and the F-axis difference image I _5. , The vector composite image I ₆ is a difference image of the PS (Phase sensitive) method or a blood vessel image corresponding to an elementary image of the TOF (Time of blight) method. Obtains the vector composite image I ₆ for a plurality of slices, the final two-dimensional projection blood vessel image is obtained by performing projection processing. On the other hand, data obtained by the above-described measurement procedure has phase information reflecting the blood flow velocity, and this phase is obtained by reconstructing a phase image instead of obtaining an absolute value image. Information can be extracted as a two-dimensional distribution. Phase indicated by the blood flow signal in the phase image is determined by the target flow velocity V _t and the blood flow velocity V _f set at the time the measurement, when the phase of the blood flow position and _{Φ f, Φ f = π ·} V f / V _t (1) Here, the target velocity V _t, when the PC measurement of blood flow signal is that the flow rate to be measured, so that the phase difference is π at the maximum between the positive and negative flow encode at that flow rate This means setting the application amount of the flow encode pulse. Generally, it is called VENC (abbreviation of Velocity Encode), and is inversely proportional to the flow encode gradient magnetic field application amount. Therefore, the flow encode gradient magnetic field application amount increases as the low-speed flow is measured. In other words, by setting a low target velocity V _t, so that the need to increase the application time or application intensity of the flow encoding gradient magnetic field occurs. [0005] Therefore, when deforming the above equation _{(1) V f = Φ f} · V t / π ... (2) next, by measuring the phase of any pixel in the phase image, the flow rate of the pixel is calculated it can. Therefore, the phase image can also be called a flow velocity image, and this is referred to as a flow velocity map (Ve
locity Map). On this flow velocity map, by setting an arbitrary region of interest (ROI), the average flow velocity and the like in the region of interest can be easily measured. Thus, PC
The information obtained by the measurement is a blood vessel image and a blood flow velocity in each phase direction. [0006] However, the blood vessel image and blood flow velocity information obtained in such a conventional technique are as follows.
Since the blood flow velocity information is only the flow velocity in the phase direction of the measured image, it can be obtained only as the flow velocity of the blood vessel in a portion flowing parallel to the phase direction. Was. However, as shown in FIG. 8, the actual blood vessel A is meandering, and the blood vessel A flowing parallel to the phase direction C is only a small part. In such a measurement image, the displayed blood vessel images are intermittent as A ₁ and A ₂ , and there is no continuity as a single blood vessel. It was confusing. Therefore, an arbitrary blood vessel cannot be designated and its flow velocity cannot be obtained accurately, and information on the blood flow velocity cannot be used effectively. Accordingly, the present invention addresses such a problem and obtains three-dimensional blood flow data in three orthogonal directions for a diagnostic part of a subject, and obtains continuity of the diagnostic part together with its two-dimensional projection image. An object of the present invention is to provide a blood flow information display method that can be displayed as a single piece of blood flow information. [0008] In order to achieve the above object, a blood flow information display method according to the present invention provides a magnetic resonance imaging method.
A three-dimensional blood flow data is obtained by measuring blood flow signals in three orthogonal directions with respect to a diagnostic part of a subject by a zing device, and a three-axis synthetic blood vessel image is created from the measured data, and the synthetic blood vessel image is sliced. By changing the position, preparing a plurality of slices and performing projection processing to create and display a two-dimensional projected image,
A slice line in an arbitrary direction is set for the displayed two-dimensional projection image, and MPR processing is performed to create and display a slice cross-sectional image in an arbitrary direction from the three-dimensional image data of the synthesized blood vessel image. An arbitrary region of interest is set on the slice cross-sectional image, and ROI processing is performed to calculate data of blood flow in the region of interest. The blood flow velocity of a blood vessel in a predetermined direction in the region of interest is calculated by the three-dimensional blood flow. It is obtained by vector synthesis from the data, and is displayed together with the two-dimensional projected image as one continuous blood flow information. The blood flow information display method configured as described above has a magnetic
Three-dimensional blood flow data is obtained by measuring blood flow signals in three orthogonal directions with respect to a diagnostic part of a subject using a qi resonance imaging apparatus, and a three-axis synthetic blood vessel image is created from these measured data. Is prepared for a plurality of slices by changing the slice position and projection processing is performed to create and display a two-dimensional projection image. MPR processing is performed on this display image to create and display a slice cross-sectional image in an arbitrary direction. , An arbitrary region of interest is set and ROI processing is performed to calculate blood flow parameters in the region of interest. Thus, the blood flow velocity of the blood vessel in the predetermined direction in the region of interest can be obtained by vector synthesis from the three-dimensional blood flow data and displayed as one continuous blood flow information together with the two-dimensional projection image. it can. Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 are flowcharts showing the procedure of the blood flow information display method according to the present invention. The blood flow information display method is for displaying a blood vessel image search of three-dimensional bloodstream data for three orthogonal axial Diagnosis sites Oite subject to magnetic resonance imaging apparatus, FIG. 1 to the specific procedures This will be described with reference to FIG. First, three-dimensional blood flow data is obtained by measuring blood flow signals in three orthogonal directions for a required diagnostic site of a subject using a magnetic resonance imaging apparatus (step A in FIG. 1). At this time, signal data reflecting only the flow in the orthogonal X-axis, Y-axis, and Z-axis directions and signal data independent of the flow are collected. Next, when the signal data reflecting only the collected flow is set as the X-axis direction phase data, the Y-axis direction phase data, and the Z-axis direction phase data, and the signal data independent of the flow is set as the reference data. Are subjected to a two-dimensional Fourier transform to create a complex image (step B). Next, among the images created as described above, a complex difference is performed between the image created from the reference data and the image created from the other three-axis direction phase data, and three types of blood vessel images are obtained. Create (Step C). That is, an X-axis direction difference image, a Y-axis direction difference image, and a Z-axis direction difference image are created. Next, in order to enhance the visualization ability of the blood vessel image, a composite image is created from the three types of blood vessel images obtained as described above (step D). That is, assuming that the image data in the X-axis direction is S _x , the image data in the Y-axis direction is S _y , and the image data in the Z-axis direction is S _z , the sum of the respective absolute values is given by I do. Synthesized image = √S _x ² + S _y ² + S _z ² Thereafter, the processing of the above steps A to D is slightly shifted from the measurement position to create a plurality of synthesized images. Then, an interpolation process is performed between the images to create a three-dimensional three-dimensional image (step E). Next, a phase difference image is created from the real part data and the imaginary part data using the four types of complex images obtained in step B (step F). In other words, three types of phase difference images are created by taking a difference between the phase image created from the above-described reference data and the phase image created from the other three-axis direction phase data. Next, the thus obtained phase difference image is multiplied by the target flow velocity set at the time of measurement, and each flow velocity image is calculated by the following equation (step G). Flow velocity image = differential phase image × target flow velocity / π Then, similarly to the above-described step E, a plurality of flow velocity images are created, and interpolation processing is performed between the images using the obtained plurality of flow velocity images to obtain a three-dimensional image. A three-dimensional image is created (step H). As described above, four data of three-dimensional image data based on a combined image of a blood vessel and three-dimensional image data based on flow velocity images in the X-axis direction, the Y-axis direction, and the Z-axis direction are created. Next, step J in FIG.
Then, projection processing is performed on the three-dimensional image created as described above to create and display a two-dimensional projected image. In this projection processing, as shown in FIG. 4, for example, three-dimensional three-dimensional data obtained by interpolating between slices of a plurality of blood vessel images at each slice position S ₁ , S ₂ , S ₃ ,. Locate and each slice position S _1, S _2, S _3, the pixel value d ₁ of ..., d _2, d _3, the total sum value of the pixel data d obtained by projecting ... the on a single two-dimensional plane P _t or This is the process of displaying the maximum value. Then, the two-dimensional projection image I ₇ obtained by subjecting such a projection process, for example, as shown in FIG. 3, is displayed on the first region E ₁ obtained by dividing a display screen into a plurality. Next, it is determined whether to change the projection position (step K). If it is to be changed, the process proceeds to the "YES" side and returns to step J, where a new projection position is set and the projection process is again performed on the new projection position to create and display a two-dimensional projected image. At this time, the projection position can be changed and designated by an input device such as a trackball. If the projection position is not changed, the process proceeds to the “NO” side and enters the next step L. [0015] In step L, MPR (Multi Planer to the two-dimensional projection image I _7, which is displayed as shown in FIG. 3
Reconstraction) processing. This MPR process is shown in FIG.
On the first region E 2-dimensional projection image I ₇ displayed on the _first,
For example, a horizontal slice line L ₁ and a vertical slice line L ₂ are displayed, and these slice lines L ₁ ,
The slice cross-sectional images I ₈ and I ₉ passing through L ₂ are obtained by calculation, and one slice cross-sectional image I ₈ is displayed in the second area E ₂ and the other slice cross-sectional image I ₉ is displayed in the third area E ₃ . Is what you do. At this time, the slice lines L _1, l ₂ of the is adapted to be moved by operating the track ball or arrow keys or the like to an arbitrary position on the two-dimensional projection image I _7. Next, it is determined whether or not to change the slice line (step M). In the case of changing, the process proceeds to the “YES” side and returns to step L, a new slice line is set, and the MPR process is performed again on the new slice line to create and display a slice cross-sectional image passing through the changed slice line.
If the slice line is not changed, the process proceeds to the “NO” side and enters the next step N. In step N, regions of interest ROI ₁ and ROI ₂ are set on slice sectional images I ₈ and I ₉ displayed as shown in FIG. 3, respectively, and ROI processing is performed.
In this ROI process, regions of interest ROI ₁ and ROI ₂ each having an arbitrary shape and size are arbitrarily set on the slice sectional images I ₈ and I ₉ displayed in the two regions E ₂ and E ₃ in FIG. It is set at the position and calculates and displays the blood flow parameters such as the area, mean value, and standard deviation in the regions of interest ROI ₁ and ROI ₂ . Next, it is determined whether or not to change the region of interest (step P). If it is to be changed, the process proceeds to the "YES" side and returns to step N, where a new region of interest is set and the ROI process is performed again. If the region of interest is not changed, the process proceeds to “NO” and enters the next step Q. In step Q, a flow velocity value process is performed on the blood vessels in each of the regions of interest ROI ₁ and ROI ₂ displayed as shown in FIG. That is, each of the regions of interest R
Arrows are displayed in the vicinity of OI ₁ and ROI ₂ as shown in FIG. 3, and the blood flow velocity in the direction in which the arrows point is obtained and displayed. At this time, the arrow can be set in any direction by operating a trackball, an arrow key, or the like. In the calculation of the flow velocity value in this case, the regions of interest ROI ₁ and ROI ₂ shown in FIG. 3 are set from the three-dimensional image data based on the flow velocity images in the X-axis direction, the Y-axis direction, and the Z-axis direction obtained in step H described above. The data of the position and the direction thus obtained is obtained by vector synthesis as shown in FIG. That is, when the flow velocity values on the X axis, the Y axis, and the Z axis are represented by V _x , V _y , and V _z , respectively, first, the magnitude V _xy of the combined vector of the X axis and the Y axis is V _xy = √V ² _x · cos ² θ + V ² _y · sin ² θ Next, the magnitude V _xyz of the combined vector of the X axis, the Y axis, and the Z axis is given by: V _xyz = √V ² _xy · cos ² φ + V ² _z · sin ² φ. Here, φ is an angle in an arbitrary direction. And
As shown in FIG. 3, the flow velocity values of the blood flow obtained in this manner are displayed on the fourth region E ₄ of the display screen in the respective regions of interest ROI ₁ , ROI ₁ ,
For each ROI _2, for example, v ₁ cm / s and v ₂ cm / s are displayed. At this time, on the display screen, along with the two-dimensional projection image I _7, the flow rate value of the blood flow is displayed as v _1, v ₂ as a single blood flow information of each of continuity. Next, it is determined whether or not all the processes have been completed (step R). If the processing is still in progress and the processing is not completed, the processing proceeds to “NO” and returns to step J, and the above-described processing of steps J → K → L → M → N → P → Q → R is repeated. When the processing is completed, the process proceeds to the “YES” side to end all the procedures. The present invention has been configured as described above.
A three-dimensional blood flow data is obtained by measuring blood flow signals in three orthogonal directions with respect to a diagnostic site of a subject by a magnetic resonance imaging apparatus, and a three-axis synthetic blood vessel image is created from these measured data. Is prepared for a plurality of slices by changing the slice position and projection processing is performed to create and display a two-dimensional projection image. MPR processing is performed on this display image to create and display a slice cross-sectional image in an arbitrary direction. , An arbitrary region of interest is set and ROI processing is performed to calculate blood flow parameters in the region of interest. Thus, the blood flow velocity of the blood vessel in the predetermined direction in the region of interest can be obtained by vector synthesis from the three-dimensional blood flow data, and displayed as one continuous blood flow information together with the two-dimensional projection image. it can. Therefore, the information on the blood flow, which has been obtained only partially in the past, can be easily obtained as continuous blood flow information of an arbitrary cross section and in any direction. Thereby, the information on the blood flow velocity can be used effectively.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a procedure before an intermediate connector in a blood flow information display method according to the present invention. FIG. 2 is a flowchart showing a procedure after an intermediate connector in the blood flow information display method according to the present invention. FIG. 3 is an explanatory diagram showing a display example of a screen according to the blood flow information display method of the present invention. FIG. 4 is an explanatory diagram showing an outline of an image projection process. FIG. 5 is an explanatory diagram showing vector synthesis for obtaining a blood flow velocity value. FIG. 6 is an explanatory diagram schematically showing a pulse sequence of the PC measurement method. FIG. 7 is an explanatory diagram schematically showing a blood vessel image creating procedure in the PC measurement method. FIG. 8 is an explanatory diagram showing a display example of a blood vessel image of a meandering blood vessel actually measured. [Description of Signs] E _{1 to} E ₄ Divided area I _{7 of} display screen I ₇ Two-dimensional projected image I ₈ slice sectional image I ₉ slice sectional image L ₁ slice line L ₂ slice line ROI ₁ region of interest ROI ₂ region of interest

Claims (1)

(57) [Claims] 1. A means for acquiring a blood flow signal from a subject is provided.
In the obtained magnetic resonance imaging apparatus, three-dimensional blood flow data is obtained based on the blood flow signals in three orthogonal directions obtained for the diagnostic site of the subject , and a three-dimensional synthetic blood vessel image is formed using these blood flow data. create a 3D velocity images together to create a synthetic blood vessel image of the three-dimensional created displaying a two-dimensional projection image by projecting the desired direction, the desired slice lines on the two-dimensional projection image Designation
Then, the slice cross-sectional image passing through this slice line
Create and display from the synthesized blood vessel image of this , specify the desired region of interest on this slice cross-sectional image , and specify the direction of the blood flow velocity to be found near this region of interest
And the blood flow velocity of the blood vessel in said region of interest in its designated direction.
Means for calculating the blood flow velocity from the three-dimensional flow velocity image and displaying the blood flow velocity close to the slice cross-sectional image.
A magnetic resonance imaging apparatus comprising: