JP3198721B2 - MR imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MR (Magnetic Resonance) imaging apparatus for performing imaging using the phenomenon of nuclear magnetic resonance (NMR).

[0002]

2. Description of the Related Art An MR imaging apparatus uses the resonance phenomenon of nuclei to capture and image spin relaxation time differences in various tissues in a living body, and is capable of obtaining an image with excellent contrast representing the relaxation time differences. Has become an indispensable modality in the field of medical form diagnosis. Furthermore, since the change in relaxation time is also captured, properties are diagnosed.

On the other hand, in recent years, with the progress of a high-speed imaging method as an imaging pulse sequence in this MR imaging apparatus, MRI using a contrast agent and indirect dynamic studies have been performed, and the movement of the myocardium has been increasing. MR cine imaging that clearly captures images is also being performed.

[0004]

However, in spite of such progress, there is a problem that the MR imaging apparatus only captures the morphology of the tissue in the living body and cannot capture the hardness of the tissue. That is, according to the conventional MR imaging apparatus, tissue discrimination can be performed using a T1-weighted image, a T2-weighted image, or a contrast image, but information about the hardness of the tissue cannot be obtained. Therefore, the hardness of the tissue is an important finding for the diagnosis of the case where the disease is clearly hardened with the progression of the condition such as cirrhosis, but the MR imaging apparatus is not useful in this regard, and the traditional method, that is, the doctor However, there is no choice but to use the palpation method of touching the patient's body with the hand to determine the hardness of the organ from the outside. is there.

[0005] In view of the above, it is an object of the present invention to provide an MR imaging apparatus improved so that objective quantitative data on hardness of a target portion inside a subject can be obtained.

[0006]

In order to achieve the above object, an MR imaging apparatus according to the present invention comprises:
Collecting data before and after the morphological change of the target portion inside the subject, reconstructing at least two images before and after the morphological change of the target portion from the collected data,
It is characterized in that the edges of the target portion appearing in these two images are extracted, and an index indicating a change in the edges is calculated.

[0007]

For example, for a liver whose morphology changes due to respiration, two images before and after the morphological change are obtained, and the edges of the liver image appearing in these two images are extracted. An index representing a change, for example, a curvature function is calculated. In the case of a normal liver, the liver is greatly deformed by respiration, but the liver in which cirrhosis has progressed is hard and thus has a small degree of deformation, and moves only in parallel depending on respiration. Therefore, if a curvature function or the like representing a change in the edge of the liver image is obtained, the hardness of the liver can be objectively known, and the hardness of the liver does not depend on the personal subjectivity of a doctor or the like by palpation. Obtain objective data about

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a main magnet 11 is for generating a static magnetic field, and a gradient magnetic field is applied by a gradient coil 12 so as to overlap the static magnetic field. The gradient magnetic field coil 12 has X, Y, Z
Gradient magnetic field G whose magnetic field strengths incline in three axial directions
It is arranged to generate x, Gy, Gz. A subject (patient) not shown is placed in the space where the static magnetic field and the gradient magnetic field are applied, and the RF coil 13 is provided on the subject.
Is attached.

The gradient coil 12 has a gradient magnetic field power supply 21.
Are connected, and power for generating the respective gradient magnetic fields of Gx, Gy, and Gz is supplied. This gradient magnetic field power supply 21 has a waveform generator 2
2, the Gx, Gy, and Gz gradient magnetic field waveforms are controlled.

The RF coil 13 includes an RF power amplifier 33.
Supplies an RF signal, and the subject is irradiated with the RF signal. The RF signal is obtained by subjecting the RF signal generated by the RF signal generator 31 to AM modulation by the modulator 32 in accordance with the waveform sent from the waveform generator 22.

The NMR signal generated by the subject is received by the RF coil 13 and sent to the phase detector 42 via the preamplifier 41. In the phase detector 42, the received signal is phase-detected using the RF signal from the RF signal generator 31 as a reference signal, and the detection output is sent to the A / D converter 43.
The A / D converter 43 includes a sampling pulse generator 2
4, a sampling pulse is input, and the detection output is converted into digital data according to the sampling pulse. The digital data is taken into the host computer 51.

The host computer 51 processes the captured data to reconstruct an image, and determines the timing of the entire sequence via the timing generator 23. That is, the timing generator 23 sends a timing signal to the waveform generator 22, the RF signal generator 31, the sampling pulse generator 24, and the like under the control of the host computer 51, and the waveform generator 22 outputs each waveform signal. And the RF signal generator 3
1 is determined, and further, the sampling pulse generation timing from the sampling pulse generator 24 is determined. Also, the host computer 51
Sends waveform information to the waveform generator 22 and outputs Gx, Gy, G
Controls the waveform, intensity, etc. of each gradient magnetic field pulse of z, determines the envelope of the RF signal to be irradiated from the RF coil 13 to the subject, and sends a signal to the RF signal generator 31 to control the frequency of the RF signal. .

An image display device 52 connected to the host computer 51 displays a reconstructed MR image and the like. The input device 53 is a keyboard device, a mouse, or the like, and is used to make various settings relating to an imaging sequence and to set the angle and position of an imaging section. The recording device 55 records the reconstructed MR image and the like, and the arithmetic device 54 extracts an edge of the organ of interest image from the reconstructed image and calculates a curvature function (described later).
Perform

In this embodiment, information on the hardness of the liver is obtained. The liver moves and changes its shape in accordance with the movement of the lungs accompanying breathing. Therefore, it is necessary to obtain MR images at at least two timings of inspiration and expiration, and it is desirable to obtain a series of MR images of the liver that deforms during deep breathing. At this time, it is desirable to set a slice plane with less displacement due to respiratory motion as an imaging section. Here, a sagittal median section as shown in FIG. 2 is set as a slice plane.

While the subject is taking a deep breath, an imaging sequence is performed so as to obtain, for example, 16 images every second. If the most different one of the images is selected, one is obtained at the timing of inhalation and the other is obtained at the timing of expiration. Thus, the image of the exhalation is shown in FIG.
As shown in FIG. 2B, images as shown in FIG. 2B are obtained as the intake images. The example of this image shows a normal liver, but if it is normal, the edge of the liver image is greatly deformed. On the other hand, in the case of liver with advanced cirrhosis, there is little deformation of the periphery of such a liver image, and the entire liver image simply moves in parallel.

These images are stored in the recording device 55. These are read out, and the computing device 54 first extracts the edges of the target liver image. Thereafter, an index representing the degree of deformation of the edge of the liver image between the two images is calculated. Here, the curvature function of the edge of the liver image is determined. The curvature function is shown in FIG.
Is defined by

(Equation 1)

When the curvature function along the ABC of the periphery of the liver image shown in FIGS. 2 (a) and 2 (b) is obtained, the results are as shown in FIGS. 3 (a) and 3 (b). , B in the inspiratory image
It can be seen that the curvature at the point has increased. If the change in curvature at each point on the edge of the liver image is summed, it corresponds to the degree of deformation. The higher the degree of deformation, the softer the liver, and the lower the degree of deformation, the harder the liver. Therefore, the above-described sum of changes in curvature can be used as an objective index indicating the hardness of the liver. Therefore, it becomes possible to quantitatively evaluate the progress of cirrhosis based on this index, which is very useful in diagnosis.

In the above description, the arithmetic unit 54 is used to extract the edge of the target organ image and determine its curvature, but it is also possible to configure the host computer 51 to execute an algorithm for the calculation. Further, the degree of deformation is not limited to the one that focuses on the curvature function of the edge of the image, and it is also possible to use a cutoff related to deformation as an index. Also,
As the imaging section, in the case of the liver, the slice thickness is 80 m
A coronal cross section of m may be used. Although a two-dimensional image has been described above, the same can be applied to a three-dimensional image. Further, in this embodiment, it is grasped that the liver is deformed by respiratory movement. However, it is also possible to obtain information on hardness from the degree of deformation of an image of another organ for another organ.

[0019]

According to the MR imaging apparatus of the present invention, it is possible to obtain quantitative and objective information on the hardness of a target portion inside a subject. For this reason, for example, objective quantitative data can be obtained on the hardness of the liver of a patient with cirrhosis, so that the uncertainty in diagnosis can be improved and contribute to medical diagnosis.

[Brief description of the drawings]

FIG. 1 is a block diagram of an MR imaging apparatus according to one embodiment of the present invention.

FIG. 2 is a view showing an image obtained in the embodiment.

FIG. 3 is a diagram showing a curvature obtained in the example.

FIG. 4 is a diagram illustrating a curvature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Main magnet 12 Gradient magnetic field coil 13 RF coil 21 Gradient magnetic field power supply 22 Waveform generator 23 Timing generator 24 Sampling pulse generator 31 RF signal generator 32 Modulator 33 RF power amplifier 41 Preamplifier 42 Phase detector 43 A / D conversion Device 51 host computer 52 image display device 53 input device 54 arithmetic device 55 recording device

Claims (1)

(57) [Claims] 1. A means for generating a static magnetic field, a means for generating a gradient magnetic field, a means for irradiating an RF signal, a means for receiving an NMR signal, a means for collecting data from the received NMR signal, Means for acquiring an image before and after the morphological change of the target portion inside the subject by controlling the imaging sequence, and at least two images before and after the morphological change of the target portion from the collected data. An MR imaging apparatus comprising: reconstructing means; and calculating means for extracting an edge of the target portion appearing in the two images and calculating an index indicating a change in the edge.