JPH07254056A - Image diagnosis device - Google Patents

Abstract

PURPOSE:To more frequently change a projection direction by calculating the image information projected from a designated angle direction and displaying the calculated image information. CONSTITUTION:By driving the inclined magnetic field power source 10 of each coil in accordance with the instruction from a sequencer 7, the inclined magnetic fields Gx, Gy and Gz of the three axes directions of X, Y And Z are impressed on an examinee 1. By the adding ways of these inclined magnetic fields, the slice surface for the examinee 1 can be set. A signal processing system 6 is composed of a CPU 8, the recorder of a magnetic disk 18 and a magnetic tape 19, etc., and the display 20 of a CRT, etc. In the CPU 8, processings such as a Fourier transform, etc., are performed, proper calculations are performed for the signal intensity distribution of an arbitrary section or plural signals, the obtained distribution is visualized and the distribution is displayed as a tomographic image on a display 20. This device is provided with a track ball 30 and the tomographic image can be visualized by rotating the tomographic image in an arbitrary direction by the operation of the track ball 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image diagnostic apparatus,
For example, it relates to improvement of a magnetic resonance imaging apparatus and the like.

[0002]

2. Description of the Related Art For example, some magnetic resonance imaging apparatuses are capable of displaying a projected image of an object displayed on a monitor by changing it so that it can be observed from a direction different from the direction in which the projected image is observed. Are known.

Three-dimensional information consisting of information on each slice image of the subject, which is sequentially sliced, is stored in advance in a memory,
By designating the angle of the direction to be observed, the image information projected from the direction of the designated angle is calculated based on the three-dimensional information, and the calculated image information is displayed.

[0004]

However, the magnetic resonance imaging apparatus configured as described above specifies only an angle about one axis such as the caudal-caudal direction axis of the subject or the left-right axis, and the specified angle is set. Only the projected image from the angle was displayed, and it was impossible to obtain the projected image from other directions.

However, in order to further improve the efficiency of diagnosis, it has been desired to be able to display projected images from more directions.

The present invention has been made under such circumstances, and its object is to display a projected image that can be observed from a designated projection direction. An object of the present invention is to provide an image diagnostic apparatus capable of changing the number of times much more than before.

[0007]

In order to achieve such an object, the present invention basically provides a memory for storing three-dimensional information consisting of information of each sliced slice image of a subject. An angle designating means capable of designating an angle around the caudal-caudal direction axis and an angle of a left-right direction axis of the subject, and image information obtained by projecting the three-dimensional information stored in the memory from the designated angle direction by the angle designating means. And a display unit for displaying the image information calculated by the calculation unit.

[0008]

According to the image diagnostic apparatus having such a structure, in particular, it is provided with an angle designating unit capable of designating an angle around the caudal-caudal direction axis and an angle around the left-right direction axis of the subject. .

If the angle around the caudal-caudal direction axis and the angle of the left-right direction axis of the subject are designated by the angle designating means, the information of each sequentially sliced cross-sectional image of the subject stored in the memory in advance. The image information projected from the direction of the specified angle is calculated on the basis of the three-dimensional information constituted by, and the calculated image information is displayed.

Therefore, such a projection image is created on the basis of the angle designations of the subject about the caudal-caudal direction axis and the left-right direction axis, and the projection direction can be changed much more than before. It becomes possible to display it as a thing.

[0011]

2 is a block diagram showing the overall construction of a magnetic resonance imaging apparatus according to the present invention.

This magnetic resonance imaging apparatus obtains a tomographic image of a subject by utilizing a nuclear magnetic resonance (NMR) phenomenon, and includes a static magnetic field generating magnet 2, a magnetic field gradient generating system 3, and a transmitting system 4. , A reception system 5, a signal processing system 6, a sequencer 7, and a central processing unit (CPU) 8.

The static magnetic field generating magnet 2 generates a uniform static magnetic field around the subject 1 in the body axis direction or in a direction orthogonal to the body axis, and has a certain spread around the subject 1. A magnetic field generating means of permanent magnet type, normal conducting type or superconducting type is arranged in the open space.

The magnetic field gradient generation system 3 is composed of a gradient magnetic field coil 9 wound in three axial directions of X, Y and Z, and a gradient magnetic field power source 10 for driving each of the gradient magnetic field coils. The gradient magnetic field power supplies 10 of the respective coils are driven in accordance with the command 1 to apply the gradient magnetic fields Gx, Gy, Gz in the three axial directions of X, Y, Z to the subject 1. The slice plane for the subject 1 can be set by the method of applying this gradient magnetic field.

The sequencer 7 repeatedly applies a high frequency magnetic field pulse which causes nuclear magnetic resonance to the atomic nuclei of the atoms constituting the living tissue of the subject 1 in a predetermined pulse sequence, and operates under the control of the CPU 8. Various commands necessary for collecting data of a tomographic image of the subject 1 are sent to the transmission system 4, the magnetic field gradient generation system 3 and the reception system 5.

The transmission system 4 irradiates a high frequency magnetic field in order to cause nuclear magnetic resonance in the atomic nuclei of the atoms constituting the living tissue of the subject 1 by the high frequency pulse sent from the sequencer 7. The high frequency oscillator 11 And modulator 12
And a high-frequency amplifier 13 and a high-frequency coil 14a on the transmission side. The high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by a modulator 12 according to a command from the sequencer 7, and the amplitude-modulated high-frequency pulse is high-frequency. After being amplified by the amplifier 13, it is supplied to the high-frequency coil 14a arranged close to the subject 1, so that the subject 1 is irradiated with electromagnetic waves.

The receiving system 5 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of atomic nuclei of a living tissue of the subject 1, and includes a high frequency coil 14b on the receiving side, an amplifier 15 and a quadrature phase detector. 16 and A / D converter 17
The electromagnetic wave (NMR signal) of the response of the subject 1 due to the electromagnetic wave emitted from the high-frequency coil 14a on the transmitting side is placed in the high-frequency coil 14 close to the subject 1.
detected by b, input to the A / D converter 17 through the amplifier 15 and the quadrature detector 16, converted into a digital amount, and further sampled by the quadrature detector 16 at the timing according to the instruction from the sequencer 7. Two series of collected data are provided, and the signals thereof are sent to the signal processing system 6.

This signal processing system includes a CPU 8, a recording device such as a magnetic disk 18 and a magnetic tape 19, and a CRT.
The CPU 8 performs processing such as Fourier transform, correction coefficient calculation image reconstruction, etc., and performs image processing on the signal intensity distribution of an arbitrary section or the distribution obtained by performing appropriate calculation on a plurality of signals. Display 20
It is designed to be displayed as a tomographic image.

In the figure, the high frequency coils 14a and 14b on the transmitting side and the receiving side and the gradient magnetic field coil 9 are
It is installed in the magnetic field space of the static magnetic field generating magnet 2 arranged in the space around the subject 1.

In this embodiment, in particular, a trackball 30 is provided, and the trackball 30 will be described in detail later, but its operation rotates the tomographic image displayed on the display 20 in an arbitrary direction. By doing so, it is possible to visualize, and along with that, the part that was hidden by other organs until now can also be visualized.

FIG. 3 is a schematic explanatory view showing an embodiment of the pulse sequence incorporated in the sequencer 2.

The figure shows a pulse sequence of a typical spin echo method among so-called two-dimensional Fourier imaging methods. (A) shows the irradiation timing of the high-frequency magnetic field signal and the envelope for selectively exciting the slice position of the subject 1. (B)
Shows the application timing of the gradient magnetic field Gz in the slice direction, and (c) shows the application timing of the gradient magnetic field Gy in the phase encoding direction and the measurement while changing its amplitude. (D) shows the application timing of the gradient magnetic field Gx in the frequency encoding direction, and (e) shows the echo signal (NMR signal) to be measured.

In the figure, first, a 90 ° pulse is applied, and then a 180 ° pulse is applied at Te / 2 when the echo time is Te. After applying the 90 ° pulse, each spin starts rotating in the XY plane at its own velocity, and a phase difference occurs between the spins over time. Then, when the 180 ° pulse is applied, each spin is inverted symmetrically with respect to the X-axis, and thereafter, the spins are focused at time Te to continue to rotate at the same speed and form an echo signal.

In this process, by applying a gradient magnetic field Gy in the phase encoding direction and a gradient magnetic field Gx in the frequency encoding direction, spatially different magnetic field strengths are formed, and information on the spatial surface corresponding to the magnetic field strengths, that is, a tomographic image. I try to get information. This is because the frequency of spins on a space having a predetermined magnetic field strength is determined by the magnetic field strength.

Using such a pulse sequence as a basic unit, the intensity of the phase-encoding-direction gradient magnetic field Gy is changed every time, and is repeated a predetermined number of times, for example, 256 times, every constant repetition time Tr. After that, the spatial distribution of macroscopic magnetization is obtained by subjecting the measurement signal thus obtained to two-dimensional inverse Fourier transform.

Here, the three types of gradient magnetic fields may be any of X, Y, Z, or a combination thereof, as long as they do not overlap each other.

Therefore, it is possible to obtain a tomographic image of the surface of the subject 1 which is successively sliced at equal intervals along an arbitrary direction.

FIG. 4 shows tomographic image information of a plurality of slice planes orthogonal to the cranio-caudal direction (body axis direction; x-axis direction) of the subject 1, which are three-dimensional image information (three-dimensional blood vessel data in the figure). ) Is stored in the magnetic disk 18 (magnetic tape 19).

As is apparent from the figure, the three-dimensional image information is set by setting its projection direction (in the figure,
Two-dimensional image information observed from that direction (0 °, 45 °, 90 ° with respect to the x-axis) can be obtained by the method described later.

The two-dimensional image information shown in the figure can be grasped as an image obtained by rotating the x axis.

FIG. 1 shows the above-mentioned three-dimensional image information as x
Rotate α around the axis ((a) in the figure), then
It is rotated by β ° about the y ′ axis ((b) in the figure). FIG. 6C shows that the information of (α, β) causes the three-dimensional image information to be inclined at a predetermined angle. From this, by changing the value of the information (α, β), a two-dimensional image obtained by projecting the three-dimensional image information from almost all directions can be obtained.

FIG. 5 is an explanatory diagram for inputting the information (α, β), and as the means therefor, for example, the track ball 30 shown in FIG. 2 is used. FIG. 10A shows that by rotating the trackball 30 left and right, a projection image rotated around the caudal-caudal direction axis of the subject by an angle corresponding to the rotation angle can be created. Further, FIG. 2B shows that by rotating the trackball 30 up and down, the tomographic image of the subject can be rotated around its horizontal axis by an angle corresponding to the rotation angle.

FIG. 6 shows the trackball 30 shown in FIG.
3 is an explanatory diagram showing a calculation method performed by a CPU 8 shown in FIG. 2 based on information (α, β) obtained by the operation of FIG.

Here, FIG. 6 shows a memory space in which the three-dimensional information stored in the magnetic tape 19 (or the magnetic disk 18) is replaced by interpolation processing.

By setting the specified angles α and β,
From the three-dimensional information, the address increment amount for information reading is determined based on the equation (1).

[0036]

[Equation 1]

Here, the vector (Px '), the vector (Py'), and the vector (Pz '') are x'and
It is the increment amount along each axial direction of y ′ and z ″, and P represents the pixel pitch of the image acquired as the three-dimensional information.

In the calculation of the projection data, first, the origin (0,0,0) is set as the starting point, the voxel (cubic pixel in the three-dimensional space) data is read, and the vector (Pz '') is calculated. Compare with the voxel data at the incremented position and take the maximum value.

Next, this maximum value is compared with the voxel data at the position of 2 · vector (Pz ″) from the origin, and the larger value is set as the maximum value. In this way, all data on the same axis (black circles in the figure) are read sequentially while reading data in the z '' axis direction.
Is repeated until the reading is completed, and the maximum projection value in the z ″ -axis direction passing through the origin is obtained.

Next, the point moved by the vector (Py ') from the origin is set as the start point, and the vector (P
The maximum value in the z '') direction is obtained and used as the next projection data. When the imaging data passing through all the points of the vector (Py ′) pitch in the y-axis direction is obtained, the vector (Px ′) is moved and the same processing is continued.

In this way, one projection image is created by covering the projections of all points of the three-dimensional information.

Further, the three-dimensional data existing in the memory exists as discrete point values (white circles in the figure) and may not always exist on the x ', y', z '' axes. . However, {a vector (Px '), b vector (Py'), c vector (P
z ″)} point data is obtained by interpolation from the data around it. It goes without saying that the interpolation at this time may be linear interpolation or higher-order interpolation such as so-called spline interpolation.

In FIG. 7, when the x-axis is the head-to-tail axis and the y-axis is the left-right axis, α is 180 ° to the left (L = 180) to 179 ° to the right (R = 179), and β is Head direction 18
0 ° (H = 180) to 179 ° in the foot direction (F = 179)
It is a figure which shows the case where it sets in the range up to. In the figure,
Although the appearances of the subject 1 from the respective projection directions are shown, it goes without saying that they are for easy understanding and are actually the projection images shown in FIG. 4.

Further, FIG. 8 shows the relationship between the projection angle and the projection direction in an easy-to-understand manner.

According to the image diagnostic apparatus described above, in particular, it is provided with the angle designating means for designating the angle around the caudal-caudal direction axis and the angle around the left-right direction axis of the subject.

Then, if the angle around the caudal-caudal direction axis and the angle of the left-right direction axis of the subject are designated by the angle designating means, information of each sequentially sliced cross-sectional image of the subject stored in the memory in advance. The image information projected from the direction of the specified angle is calculated on the basis of the three-dimensional information constituted by, and the calculated image information is displayed.

Therefore, such a projection image is created based on the designation of the angles of the subject about the caudal-tail direction axis and the left-right direction axis, and the projection direction can be changed much more than before. It becomes possible to display it as a thing.

In the above-mentioned embodiment, the so-called maximum intensity projection method is basically used in the projection method, but it goes without saying that the so-called minimum intensity projection method may be used.
This minimum projection method is effective when the so-called Black-Blood method for extracting blood vessels as a low signal is used.

Although the above-described embodiment has been described with respect to the magnetic resonance imaging apparatus, it is needless to say that the present invention is not limited to this and may be applied to other image diagnostic apparatus.

[0050]

As is apparent from the above description,
According to the image diagnostic apparatus of the present invention, in the case of displaying a projected image that can be observed from a designated projection direction, the projection direction can be changed much more than before.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main part of an embodiment of an image diagnostic apparatus according to the present invention.

FIG. 2 is a block diagram showing an embodiment of an image diagnostic apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a sequence of the image diagnostic apparatus according to the present invention.

FIG. 4 is an explanatory diagram illustrating three-dimensional image information stored in a memory of the image diagnostic apparatus according to the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of an angle designating means provided in the image diagnostic apparatus according to the present invention.

FIG. 6 is an explanatory diagram showing an embodiment of a calculation method performed by the CPU of the image diagnostic apparatus according to the present invention.

FIG. 7 is an explanatory diagram showing a relationship between angle information input to the image diagnostic apparatus according to the present invention and a projection direction of a displayed tomographic image.

FIG. 8 is an explanatory diagram showing FIG. 7 in a more understandable manner.

[Explanation of symbols]

 8 CPU 18 magnetic disk 30 trackball

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G06T 15/00 G01N 24/02 520 Y 9365-5L G06F 15/72 450 K

Claims (2)

[Claims] 1. A memory for storing three-dimensional information consisting of information of each slice image of a subject sequentially sliced, and an angle designation capable of designating an angle around a caudal-caudal direction axis and an angle of a left-right direction axis of the subject. Means, computing means for computing image information obtained by projecting the three-dimensional information stored in the memory from the angle direction designated by the angle designating means, and display means for displaying the image information computed by the computing means. An image diagnostic apparatus characterized by being provided. 2. The invention according to claim 1, wherein the display means for displaying the image information is provided with a display means for displaying, together with the image information, an angle about the caudal-caudal direction axis of the subject and an angle of the left-right direction axis. An image diagnostic apparatus characterized by: