JP2000139871A - Mri device and mr imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a pneumonic area into an image uninvasively without giving contrast media though it is difficult in a conventional manner by providing a moisture supply means for supplying atomized moisture, scanning the pneumonic area by means of a scanning means in a state where moisture is supplied to the area and magnetically collecting scan echo signals. SOLUTION: A breath holding method and an ECG gate method are commonly used in case of a first-time imaging scan and atomized moisture supply is started by an atomizer 20 by a proper timing after the end of the imaging scan. Then the second time imaging scan is executed in a way being the same as that of the first time one after a prescribed time elapses. That is, the pneumonic area is scanned in a state without moisture supply by the atomizer 20 to obtain a group of echo signals and also the area is scanned in a state where moisture is supplied by the atomizer 20 to obtain the group of echo signals. Each difference between the obtained two groups of echo signals at every pixel is obtained, MR image data concerning the differences are created and the MR image of the pneumonic area is displayed in display equipment 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic resonance (M) system for imaging the inside of a subject based on the magnetic resonance phenomenon of the subject.
R) For imaging. In particular, conventional various MR
The present invention relates to an MRI (Magnetic Resonance Imaging) apparatus and an MR imaging method capable of imaging a lung field of a living body that has been recognized as being impossible or difficult even with an imaging method.

[0002]

2. Description of the Related Art In magnetic resonance imaging, a nuclear spin of a subject placed in a static magnetic field is magnetically excited by a high frequency signal of the Larmor frequency, and an image is reconstructed from an MR signal generated by the excitation. This is an imaging method.

In the field of magnetic resonance imaging, three methods have been proposed as main imaging methods for imaging a lung field. They are hyper-polarized
(Xenon or helium) gas, contrast agent G
A perfusion method using d-DTPA (for example, the document "Hatabu H, et al., MRM 36: 503-508, 1996"), and a method by oxygen inhalation using molecular oxygen (for example, the document "Edelman RR, et al." ., Nature Medicine, 2,11,1236-12
39, 1996).

[0004] Among them, the first method using a hyper-polarized (xenon or helium) gas is a method in which the gas is inhaled into a lung field and an image is formed, for example, at the MR frequency of xenon (Xe) gas.

[0005] The second perfusion using the contrast agent Gd-DTPA is a method of observing the state of perfusion of Gd-DTPA in blood.

In the method of inhaling oxygen molecules on the third surface, the oxygen molecules are weakly paramagnetic.
It is based on the report that a sufficient signal change occurs in the water signal observable by MRI on the surface of the alveoli.

[0007]

However, the above-described imaging method has the following problems.

The first method using a hyper-polarized (xenon or helium) gas has a problem that the cost is high because normal xenon gas needs to be hyper-polarized.

[0009] In addition, the second perfusion using the contrast agent Gd-DTPA requires the administration of a contrast agent, which requires invasive treatment, and above all, the mental and physical abilities of the patient. Heavy burden. In addition, inspection costs are high. Further, depending on the patient's constitution, the contrast agent may not be administered in some cases.

[0010] Further, even with the third method of inhaling oxygen molecules, the change in signal is not sufficient on the image, and not only a satisfactory image that can be used for clinical and research purposes, but also its form can be taken. Absent. This is presumed by the present inventors for the following reasons.

The structure of the lung field is such that spongy alveoli, bronchi, pulmonary arteries, and pulmonary veins occupy most of its surface area,
There is air around it. Although the surface area of spongy alveoli is enormous, it does not have as much free water inside and outside cells as other organs (liver, kidney, etc.). Therefore, in the case of the lung field, the water signal to be detected by MRI is only detected from the vascular system, and the water signal value in the substantial part of the lung field is significantly short. It is estimated that the area around the alveoli is not reflected as an MR signal because the water molecules are smaller than the surface area. Therefore, the T2 value of the lung field = 80 ms (reference “JMRI, 2 (S): 13
-17, 1992 "), it is presumed that conventional MR imaging cannot render the parenchyma of the lung field, even though it is comparable to other organs.

SUMMARY OF THE INVENTION The present invention has been made in order to overcome the current state of the prior art, and has an object to perform imaging of a lung field, which has been considered difficult, without administering a contrast agent. To make it possible by invasion.

[0013]

SUMMARY OF THE INVENTION According to the present invention, water molecules are attached to the surface of a spongy alveoli by supplying a substantially insufficient (almost no) water to the lung parenchyma from the outside. MR imaging is performed by causing an MR phenomenon in water molecules. In other words, it occupies the surface area of the alveoli,
The purpose is to increase water molecules that contribute to the MR phenomenon.

Specifically, while the patient is lying on the bed of the MRI apparatus, the patient is inhaled by a nebulizer from a nebulizer (such as a nebulizer) through the bronchi, thereby supplying the water to the lung field. An essential requirement is to include a step of performing an MR scan in a supply state.

By this water supply, the signal value of the parenchyma of the lung field rises, and the morphological information can be imaged. Further, since it becomes possible to observe the difference between the signal value of the air and the signal value of the substantial part, it is possible to change the body position of the patient and take an image. For example,
When it is turned sideways, the lung parenchyma falls to one side due to gravity, and the difference between air and the parenchyma can be observed. Thus, for example, it is possible to determine whether a lesion such as a tumor has penetrated the pleura. Also, based on the difference in the degree of staining between the normal tissue and the tumor after the supply of the atomized water,
Tumor differentiation is also possible. Lung tumors are condensed lung tissue,
Since it is harder than normal tissue, it can be differentiated by improving the signal value of normal tissue.

Further, as one application of the present invention, a configuration in which dynamic perfusion imaging is performed in a state in which atomized water is supplied is also possible.

A specific configuration of the MRI apparatus of the present invention is an MRI apparatus for obtaining an MR image of a lung field of a patient as a subject, a water supply means for supplying atomized water to the lung field, Scanning means including means for magnetically scanning the lung field based on a pulse sequence to collect echo signals in a state in which water is supplied to the lung field by a supply means, and obtaining the echo signal from the echo signal collected by the scanning means. Image generating means for generating data of the MR image.

Various components may be added to this configuration.

[0019] For example, the scanning means may scan the lung field supplied with water by the water supply means a plurality of times over time.
Means for executing the scan to collect a plurality of sets of the echo signals, wherein the image generating means includes means for generating the MR image data from each set of the plurality of sets of echo signals collected by the scan means. Yes, it can be configured as follows.

Further, the scanning means may be means for executing scanning using a pulse sequence of an SE (spin echo) system as the pulse sequence. Further, a means for executing a scan using an FE (field echo) pulse sequence may be used. further,
The pulse sequence may be set to a pulse sequence to which an MT pulse is added.

Further, the apparatus further comprises time phase detecting means for detecting a signal representing the cardiac time phase of the patient, wherein the scanning means is adapted to apply a predetermined waveform to a reference waveform caused by a heartbeat contained in the signal representing the cardiac time phase. A scan start unit for starting the scan in synchronization with a delay time may be provided. In this case, as an example, the time phase detecting means may detect the EC of the patient.
This is a means for detecting a G signal as a signal representing the cardiac phase, and the reference waveform is an R wave included in the ECG signal.

The apparatus may further comprise breath-hold instruction means for giving a breath-hold instruction to the patient so as to hold a breath during scanning by the scanning means.

Further, as a preferred mode, the scanning means scans a lung field of the patient in a state where there is no water supply by the water supply means to obtain a set of echo signals, The lung field of the patient is scanned in a state where water is supplied by the water supply means, and 1
A second scan means for obtaining a set of echo signals, wherein the image generating means comprises: MR image data relating to a pixel-by-pixel difference between the two sets of echo signals obtained by the first and second scan means, respectively. Can be provided.

According to another aspect of the present invention, there is provided an MR imaging method for obtaining an MR image of a lung field of a patient as a subject. Supplying or supplying the atomized water, magnetically scans the imaging region including the lung field based on the pulse sequence, collects echo signals, and generates the MR image data from the echo signals. Features.

[0025]

Embodiments of the present invention will be described below.

First Embodiment A first embodiment will be described with reference to FIGS.

FIG. 1 shows a schematic configuration of an MRI (magnetic resonance imaging) apparatus according to this embodiment.

This MRI apparatus uses a patient P as a subject.
Bed, a static magnetic field generator for generating a static magnetic field, a gradient magnetic field generator for adding positional information to the static magnetic field, a transmitter / receiver for transmitting and receiving high-frequency signals, control of the entire system and image reconstruction A control / arithmetic unit responsible for
An electrocardiogram measurement unit for measuring an ECG signal as a signal representing the cardiac phase of the subject P, a breath-hold command unit for commanding the patient P to hold breath, and a supply of atomized water to the patient P Water supply unit.

The static magnetic field generating section includes, for example, a superconducting magnet 1 and a static magnetic field power supply 2 for supplying a current to the magnet 1, and has a cylindrical opening (diagnostic space) into which the subject P is loosely inserted. A static magnetic field H ₀ is generated in the axial direction (Z-axis direction).
Note that a shim coil 14 is provided in this magnet portion. The shim coil 14 is supplied with a current for homogenizing a static magnetic field from a shim coil power supply 15 under the control of a host computer described later. The couch part can retreatably insert the top plate on which the subject P is placed into the opening of the magnet 1.

The gradient magnetic field generator has a gradient magnetic field coil unit 3 incorporated in the magnet 1. The gradient magnetic field coil unit 3 includes three sets (types) of x, y, and z for generating gradient magnetic fields in X, Y, and Z axis directions orthogonal to each other.
The coils 3x to 3z are provided. The gradient magnetic field section also has x,
A gradient magnetic field power supply 4 for supplying a current to the y, z coils 3x to 3z is provided. The gradient magnetic field power supply 4 supplies a pulse current for generating a gradient magnetic field to the x, y, and z coils 3x to 3z under the control of a sequencer 5 described later.

The x, y, z coils 3x from the gradient magnetic field power supply 4
By controlling the pulse current supplied to ~ 3z,
The gradient magnetic fields in the three axes X, Y, and Z directions, which are physical axes, are synthesized, and the respective logics of a slice-direction gradient magnetic field Gs, a phase encoding direction gradient magnetic field Ge, and a readout direction (frequency encoding direction) gradient magnetic field Gr that are orthogonal to each other. The axial direction can be set and changed arbitrarily. Slice direction, phase encoding direction, and gradient magnetic fields in the readout direction are superimposed on the static magnetic field H _0.

The transmission / reception unit includes an RF coil 7 disposed near the subject P in the imaging space in the magnet 1,
And a transmitter 8T and a receiver 8R, which are connected to each other. The transmitter 8T and the receiver 8R are connected to a sequencer 5 described later.
It operates under the control of. The transmitter 8T supplies the RF coil 7 with an RF current pulse having a Larmor frequency for exciting nuclear magnetic resonance (NMR). The receiver 8R has R
The F coil 7 receives the received MR signal (high-frequency signal), performs various signal processing such as pre-amplification, intermediate frequency conversion, phase detection, low-frequency amplification, and filtering, and then performs A / D conversion. The digital quantity data (original data) of the MR signal is generated.

The control / arithmetic unit includes a sequencer (also called a sequence controller) 5, a host computer 6, an arithmetic unit 10, a storage unit 11, and a display unit 1.
2, an input device 13 and a sound generator 16. Among them, the host computer 6 has a function of instructing the sequencer 5 with pulse sequence information and controlling the operation of the entire apparatus by the stored software procedure.

This MRI apparatus is an apparatus for imaging a lung field of a patient as a subject P. In order to perform this, the atomized water is inhaled by using a water supply unit described later, and water molecules are attached to the surface of the alveoli. In this way, the density of water molecules that undergo magnetic resonance by receiving the energy of the RF signal on the alveoli surface is increased, and image data obtained by imaging the lung parenchyma in this state is handled.

Therefore, the host computer 6 performs a positioning scan (not shown) to perform the above-described imaging.
Subsequent to the preparation work such as input of the imaging conditions and the imaging conditions, the first and second imaging scans are performed at least twice as shown in FIG. Each of the two imaging scans is a two-dimensional or three-dimensional MR scan for acquiring a set of echo data required for image reconstruction. Each of these imaging scans is a breath hold method in which the patient holds his or her breath in or out,
It is desirable to use an ECG gate method based on an ECG signal in combination.

At the same time, the imaging method (nebulizer) according to the present invention for performing scanning while atomizing water is sucked is performed, for example, at the time of the second imaging scan. The second imaging scan is performed after waiting until the water molecules are appropriately attached to the alveoli surface by the suction.

The sequencer 5 has a CPU and a memory, stores pulse sequence information sent from the host computer 6, and controls the operations of the gradient magnetic field power supply 4, the transmitter 8T, and the receiver 8R according to the information. At the same time, the digital data of the MR signal output from the receiver 8R is input once and transferred to the arithmetic unit 10. Here, the pulse sequence information is
Gradient power supply 4, according to a series of pulse sequences,
All the information necessary to operate the transmitter 8T and the receiver 8R, for example, x, y, z coils 3x to 3z
And information on the intensity of the pulse current to be applied to the device, application time, application timing, and the like.

The pulse sequence may be a two-dimensional (2D) scan or a three-dimensional (3D) scan as long as the Fourier transform method is applied. The form of the pulse train is as follows. Fast SE method, Fa
The st ASE (Fast Asymmet-ric SE) method (ie,
Imaging method combining half-Fourier method with fast SE method), fast FE method, segmented fast FE method, EP
The I (echo planar imaging) method is suitable.

The arithmetic unit 10 inputs the digital data (original data) output from the receiver 8R through the sequencer 5, and stores the original data (raw data) in a Fourier space (also called k-space or frequency space) on its internal memory. Data (also referred to as data).
It is subjected to one-dimensional or three-dimensional Fourier transform to reconstruct image data in a real space. The arithmetic unit is also capable of performing data combining processing and difference arithmetic processing.

The synthesizing process includes a process of adding image data of a plurality of frames for each corresponding pixel, a maximum value projection (MIP) process of selecting a maximum value for each corresponding pixel among the image data of a plurality of frames, and the like. . As another example of the combining process, the axes of a plurality of frames may be matched in Fourier space to combine the original data with the original data of one frame. Note that the addition processing includes simple addition processing, averaging processing, weighted addition processing, and the like.

The storage unit 11 can store not only reconstructed image data but also image data that has been subjected to the above-described synthesizing processing and difference processing. The display 12 displays an image. Further, through the input device 13, information on an imaging condition, a pulse sequence, image synthesis, and difference calculation desired by the operator can be input to the host computer 6.

Further, a sound generator 16 is provided as an element of the breath-hold command unit and the water supply unit. This sound generator 1
When the host computer 6 issues a command, it can issue a breath-hold start and breath-hold end message as voice.

Further, the electrocardiogram measuring section is provided with an ECG sensor 17 for detecting an ECG signal as an electric signal by attaching the ECG signal to the body surface of the subject, and performing various processing including digitization processing on the sensor signal to obtain a host computer. 6 and an ECG unit 18 for outputting to the sequencer 5. The measurement signal from the electrocardiograph is used by the sequencer 5 when performing an imaging scan. This gives E
Synchronization timing by the CG gate method (cardiac synchronization method) can be set appropriately, and data can be collected by performing an imaging scan of the ECG gate method based on the synchronization timing.

Further, the water supply section comprises a sprayer 20. The atomizer 20 includes an atomizer body 21 that atomizes water to generate steam, and a hose 22 that leads the atomized water.
And a suction mask 23 attached to the end of the hose. Preferably, the sprayer main body 21 is placed outside the shield room SR, but the hose 22 and the suction mask 23 are formed of a non-magnetic material so that they can be inserted into the opening (diagnostic space) of the magnet 1. Has become. The patient P lying inside the magnet puts the suction mask 23 on the nose and mouth, and sucks the water to atomize the water (air). By forming the hose 22 and the suction mask 23 from a non-magnetic material in this way, various dynamic imaging can be performed while supplying atomized moisture to the patient.

Next, the operation of the imaging scan by the MRI apparatus of this embodiment will be described with reference to FIGS.

As shown in FIG. 2, the host computer 6 executes a predetermined main program (not shown) to
Two imaging scans, for example, three-dimensional Fa
This is performed by the stASE (Fast Asymmetric SE) method. First
The second imaging scan uses a combination of breath hold and ECG gating. At an appropriate timing after the end of the first imaging scan, the supply of the atomized water by the atomizer 20 is started. When the supply of the atomized water has elapsed for a predetermined time Tg, the second imaging scan is performed in the same manner as the first imaging scan. It is performed using both the breath hold method and the ECG gate method. The reason for waiting for the predetermined time Tg in the supply state of the atomized water is to wait for the water molecules to reliably adhere to the surface of the alveoli of the patient P.

First, the first imaging scan is executed as follows. While executing a predetermined main program (not shown), the host computer 6
The processing shown in FIG. 3 is executed in response to the operation information from.

More specifically, the host computer 6 first inputs the appropriately determined delay time TDL for the ECG gating method via the input device 13 (step S2).
0). Next, the host computer 6 determines the scanning conditions (the direction of phase encoding, the image size, the number of scans, the standby time between scans of each slice encode amount, the pulse sequence according to the scan region, etc.) specified by the operator from the input device 13 and Information of the image processing method (such as addition processing or maximum intensity projection (MIP) processing; in the case of addition processing, any of simple addition, averaging processing, and weighted addition processing) is input, and the delay time TDL is included. The information is processed into control data, and the control data is output to the sequencer 5 and the operation unit 10 (step S21).

Next, if it can be determined that the preparation completion notification before the scan has been received (step S22), step S2 is performed.
In step 3, a command to start breath holding is output to the voice generator 14 (step S23). As a result, the voice generator 14 emits a voice message such as "Please hold your breath after inhaling enough", and the patient who hears this will stop breathing with sufficient inhalation. (See the breath-hold start timing in FIG. 5).

Thereafter, the host computer 6 instructs the sequencer 5 to start an imaging scan (step S2).
4, see FIG. 4).

As shown in FIG. 4, the sequencer 5 receives an instruction to start an imaging scan (step S24).
-1), reading of the ECG signal is started (step S2).
4-2) The predetermined n-th occurrence of the peak value of the R wave (reference waveform) in the ECG signal is determined from the ECG trigger signal synchronized with the peak value (step S24-).
3). Here, the reason for waiting for the appearance of the R wave n times (for example, two times) is to surely estimate the time when the state has shifted to the breath holding state. Thereby, the adjustment time Tsp for waiting for the appearance of the n-th R wave is set.

When the predetermined n-th R wave appears, a process of waiting for a delay time TDL appropriately set in advance is performed (step S24-4). As described above, the delay time TDL has the highest echo signal intensity when imaging the target lung field tissue, and is optimized to a value that is excellent in the rendering ability of the entity.

The time point at which the optimum delay time TDL has elapsed is determined to be the optimum ECG synchronization timing, and the sequencer 5
Executes an imaging scan (step S24-
5). Specifically, the transmitter 8T and the gradient magnetic field power supply 4 are driven according to the pulse sequence information that has been stored, and the Fast Asymmetric SE method (high-speed S
The first scan based on the pulse sequence of the E method combined with the half Fourier method) is performed by the ECG gate method (electrocardiographic method) as shown in FIG. The echo interval in this pulse sequence is set to about 5 ms. As a result, an echo signal is acquired from the three-dimensional imaging region Rima including the lung field as shown in FIG. 7A with a scan time of about 600 ms under the initial slice encoding amount SE1.

When the first scan based on the one slice encode amount SE1 is completed, the sequencer 5 determines whether the scan based on the final slice encode amount SEn has been completed (step S4-6). In the case of NO (final scan has not been completed), while monitoring the ECG signal, for example, waits for 2 heartbeats (2R-R) from the R wave used for the imaging scan, for example, until a shorter set period elapses, The recovery of the longitudinal magnetization of the spin of the stationary substantial part is positively suppressed (step S
24-7). That is, this waiting period is the repetition time TR.

As described above, after waiting for a period corresponding to, for example, 2R-R, for example, when the third R wave appears (step S24-7, YES), the sequencer 5 executes the processing in step S24-4 described above. return. Thereby, at the time when the designated delay time TDL has elapsed from the ECG trigger signal synchronized with the third R-wave peak value, the second scan based on the slice encode amount SE2 is executed in the same manner as described above.
Echo signals are collected from the three-dimensional imaging region Rima (steps S24-4 and S24). Similarly, scanning is repeated until the final slice encoding amount SEn (for example, n = 8) to collect echo signals.

When the final scan based on the slice encoding amount SEn is completed, the determination in step S24-6 is YES, and a notification of the completion of the imaging scan is output from the sequencer 5 to the host computer 6 (step S24-8). Thereby, the processing is returned to the host computer 6.

Upon receiving the scan completion notification from the sequencer 5 (step S25), the host computer 6 outputs a command to release the breath holding to the voice generator 16 (step S2).
6). Then, the voice generator 16 issues a voice message, for example, “You can breathe” to the patient,
The breath holding period ends (see the breath holding end time in FIG. 5).

Therefore, as described in the sequence diagram of FIG. 5, scanning for each slice encoding amount is executed n times (for example, 8 times) based on the ECG gating method every 2R-R. The time required for the n scans, that is, the time for the patient to continue holding his / her breath, differs depending on the imaging conditions, but is, for example, about 20 to 25 seconds.

The eco signal generated from the patient P is received by the RF coil 7 for each scan and sent to the receiver 8R. The receiver 8R performs various pre-processing on the echo signal and converts it into a digital amount. This digital amount of echo data is sent to the arithmetic unit 10 through the sequencer 5 and arranged in a three-dimensional k-space formed by a memory. Since the half Fourier method is adopted, the data of the k-space that has not been collected is obtained by calculation and filled.
Thus, the echo data is arranged in the entire k space.

After that, the supply of the above-mentioned atomized water is started at an appropriate timing, and after a predetermined standby time Tg has elapsed, the second imaging scan is executed. This imaging scan is the same as the first scan except for the supply of atomized water as imaging conditions.

Since it is involved in the supply of the atomized water, FIG.
As shown in step S21a, the host computer 6 notifies the operator of the driving of the nebulizer 20 and the start of suction of the atomized water via the voice generator 16. For example, a message such as "drive the nebulizer and apply the suction mask to the patient" is suitable. Note that, in the second imaging scan, the information specified at the time of the first imaging scan is used for the delay time and the scan conditions of the ECG gate method.

Thereafter, the process shifts to step S22 to judge the completion of the scan preparation. At this time, the host computer 6 also determines whether or not a predetermined time Tg has elapsed after the generation of the message for driving the nebulizer. Then, steps S23 and S24 (the same processing as in FIG. 4 is executed),
After the steps S25 and S25, the second imaging scan is executed in the same manner as the first imaging scan (see FIG. 7B). Next, in step S26, together with the command to release the breath hold,
The operator is notified of the message "Remove the suction mask."

As a result, the echo data (original data) collected by the second imaging scan is also arranged in the k-space in the same manner as in the first imaging scan.

When the echo data has been collected by the two imaging scans, the host computer 6 instructs the arithmetic unit 10 to process and display the image data. This series of processing is shown in FIG.

First, the arithmetic unit 10 performs a three-dimensional Fourier transform on the echo data in the k space collected and arranged by the first imaging scan to reconstruct the image data IM1 in the real space (step 31). ). Similarly, the same reconstruction is executed for the second imaging scan to obtain the real-space image data IM.
2 is generated (step S32). As a result, the first image data IM1 is scanned in a state in which the atomized water is not supplied, as schematically shown in FIG. 9A in a two-dimensional manner. There is no adhesion of water molecules, and the signal value of the lung field LG is almost zero. On the other hand, since the second image data IM2 is scanned by supplying atomized water as schematically shown in two dimensions in FIG.
Are securely attached to the surface of the lung field, and the signal value indicating the contour of the lung field LG increases.

Therefore, the arithmetic unit 10 uses the appropriate coefficient α (0 <α ≦ 1) to obtain the two image data IM1, I2
The difference processing of IM1-α · IM2 is performed for each pixel for M2 (FIG. 8, step S33). As a result, as schematically shown in the image data IM3 of FIG. 9C (depicted in two dimensions for easy understanding), the lung field L
The signal values of the tissues other than G are canceled out due to the difference, while only the signal value of the lung field LG remains satisfactorily.

The maximum intensity projection (MIP) process is performed on the thus generated three-dimensional image data IM3 in the real space to create two-dimensional image data (FIG. 8, step S34). This image data is stored in the storage unit 11 while being displayed as an image on the display 12. The three-dimensional image data IM3 is also stored.

As described above, according to the MRI apparatus of the present embodiment, the second imaging scan is executed in the state of supply of the atomized water by the nebulizer (nebulizer). Is securely attached. For this reason,
The number of water molecules that cause magnetic resonance is remarkably increased, and image data representing the morphology of the alveolar surface, that is, the lung field surface is obtained from echo signals from the water molecules. In other words, the state is equivalent to a state where the alveoli can generate an echo signal. This has been extremely difficult with conventional lung field imaging techniques that do not use the supply of atomized water.

Therefore, the form and contour of the lung field can be visually recognized only by displaying the image data obtained by the imaging scan in the second supply state of the atomized water without performing the above-described difference processing.

In this embodiment, in addition to the supply of the atomized moisture, a weighted difference process is performed between when the atomized moisture is performed and when it is not. Therefore, it is possible to suitably extract and display an image of almost only the lung field.

In order to easily perform the difference processing, the difference processing may be performed without performing the weighting processing.

In addition, the repetition time TR and the echo interval can be set short, and the slice direction can be set, for example, in the direction of the front and back of the patient (running back from front to back). This reduces the overall scan time, and
Since the imaging length in the slice direction is shortened and the number of slice encodings can be reduced, the entire imaging time is shorter than the conventional T
It is greatly reduced compared to the OF method and the phase encoding method.
This reduces the burden on the patient and increases the patient throughput.

Along with this, the imaging of each of the two imaging scans (the imaging scan for collecting a target echo data group) can be completed within one breath-holding period. The burden is significantly reduced.

Furthermore, since it is not necessary to administer a contrast agent, imaging can be performed non-invasively, and the mental and physical burden on the patient is significantly reduced. At the same time, the inconvenience inherent in the contrast method, such as the need to measure the timing of the contrast effect, is released, and unlike the contrast method, repeated imaging can be performed as necessary.

Further, since the pulse sequence of the high-speed SE system is used, the superiority in terms of susceptibility and form distortion can be naturally enjoyed.

Further, in the case of the above-described embodiment, the entire imaging scan for acquiring a target echo data group is completed in each breath holding period. For this reason, the occurrence of body motion artifacts due to the periodic movement of the lungs and the like can be suppressed, and the occurrence of body motion artifacts due to positional displacement of the patient's body itself when performing breath-holding imaging multiple times can also be reduced. . Thereby, a high-quality image with less artifacts can be provided.

Further, since the ECG gating method is also used, it is possible to obtain image data in which body motion artifacts due to the movement of the heart are almost eliminated.

The pulse sequence employed in the first embodiment may be a simple high-speed SE method. Further, the electrocardiographic synchronization method according to this embodiment is configured to start scanning at a time phase delayed by the delay time T _DL from the R group, but the time phase of the scanning start is determined according to individual clinical requirements. Other timings may be set.

Second Embodiment A second embodiment of the present invention will be described with reference to FIG. In the following embodiments, the same or equivalent components as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted or simplified.

The MRI apparatus according to this embodiment is configured in the same manner as in the first embodiment in terms of hardware.
On the other hand, the host computer 6, the sequencer 5, and the arithmetic unit 10 cooperate to execute the imaging using the atomized moisture from the atomizer 20 using, for example, a two-dimensional segmented high-speed FE method. I do.

FIG. 10 shows a schematic flowchart of this imaging. Specifically, the first and second imaging scans are executed using a pulse train of a segmented high-speed FE method based on an ECG signal as a pulse sequence. At this time, in the first imaging scan, the breath holding method is used together, while in the second imaging scan, the atomized water is supplied from the nebulizer 20 in addition to the breath holding method.

ECG is performed by the segmented high-speed FE method.
A plurality of field echoes arranged on each line of the k space are collected in synchronization with each R wave of the signal (that is, for each segment) (steps S41a and 41b). For example, if the amount of phase encoding in k-space is 128 (ie, 12
8 lines), 1 for each R wave (for each segment)
Six field echoes are collected over a total of eight R waves (16 × 8 = 128). This total 128
The field echoes are arranged in the k space in an appropriate order.

The echo data of each set is thereafter subjected to two-dimensional Fourier transform by the arithmetic unit 10 and reconstructed into two-dimensional image data IM1 and IM2 in real space, respectively (steps (S42a, 42b). The reconstructed data IM1 and IM2 are then subjected to the same weighted difference processing as in the first embodiment, and the difference results are displayed and stored (steps S43 and S44).

Therefore, during the second imaging scan, atomized water is supplied, so that water molecules adhere to the surface of the alveoli as in the case of the first embodiment, and the magnetic resonance of the water molecules occurs. Dependent echo signals are collected. That is, a state equivalent to the state where an echo signal is generated from the surface of the alveoli having a sponge structure is generated. Therefore, the echo signals collected by the second imaging scan include the morphology / contour information of the alveoli. This form / contour information is suitably extracted by weighting difference processing for each case, and is displayed as an image of a lung field.

In the second embodiment, in particular, since the segmented high-speed FE method is used, it is possible to take an image in consideration of the influence of the movement accompanying the heartbeat.

The pulse sequence employed in the second embodiment may be a simple high-speed FE method or an FE-based EPI (Echo Planar Imaging) method. In addition, the segment high-speed F
In the E method, a fat saturation pulse (indicated by FatSat in FIG. 10) may be applied to each segment in advance.

Third Embodiment A third embodiment of the present invention will be described with reference to FIG.

The MRI apparatus according to this embodiment has the same hardware configuration as that of the first embodiment.
On the other hand, the host computer 6, the sequencer 5, and the arithmetic unit 10 cooperate to execute imaging using atomized moisture from the atomizer 20 using a pulse sequence including an MT pulse.

FIG. 11 shows a schematic flowchart of this imaging. Specifically, the first and second imaging scans are executed using a pulse train of the fast SE method to which the MT pulse is added as a pulse sequence. At this time, in each of the first and second imaging scans, in addition to the ECG gating method and the breath-holding method, the supply of atomized water from the nebulizer 20 is performed.

As shown in FIG. 11, the pulse sequence used for the first imaging scan includes a pulse train SQima composed of a high-speed SE method for imaging, an MT pulse PMT applied before the pulse train, a fat suppression pulse Pchess, and a pulse train SQima. Prior pulse train S of spoiler pulse SP
Qpre. The pulse sequence including the pre-pulse train SQpre and the imaging pulse train SQima is executed in synchronization with a certain time delayed from a certain R wave of the ECG signal.

The T pulse PMT is expressed by MT (magnetization tr
An RF pulse having a large flip angle (for example, 500 ° to 1000 °). This pulse is formed, for example, by modulating an RF signal having a desired frequency offset value with a sinc function. The MT pulse PMT is applied off-resonance together with the slice gradient magnetic field.

By this pulse application, the substantial portion of the imaging region and the moisture receive the MT effect, and the signal value of the substantial portion is reduced to a greater value than the moisture, thereby increasing the contrast between the two.

The fat suppression pulse Pchess is obtained by calculating M
CHESS (chem to suppress R signal collection (fat suppression)
ical shift selective) pulse. This pulse
This is a pulse obtained by modulating a sinc function in which the τ length is set to correspond to the chemical shift between the proton spin of water and the proton spin of fat with an RF signal of a predetermined frequency. By this application, only fat protons in the imaging region resonate and saturate.

After application of the fat suppression pulse Pchess,
As an example, the spoiler pulse SP is applied in the slice direction, the phase encode direction, and the readout direction, and the phase of the spin in each direction is dispersed (dephased).
The application direction of the spoiler pulse may be any one direction or only two directions.

At the time of the second imaging scan, the pre-pulse train SQpre includes only the fat suppression pulse Pchess and the spoiler pulse SP described above. That is, at this time, the MT pulse PMT is not applied.

In response to each of the two imaging scans, a plurality of spin echoes arranged on each line of the k space are collected (steps S51a and 51b).
This echo signal is processed into digital amount of echo data and arranged in the k space in an appropriate order.

The echo data of each set is thereafter subjected to, for example, two-dimensional Fourier transform by the arithmetic unit 10 and reconstructed into image data IM1 and IM2 in real space, respectively (steps (S52a, 52b). The configuration data IM1 and IM2 are then subjected to the same weighted difference processing as in the first embodiment, and the difference results are displayed and stored (steps S53 and S54).

Therefore, during the first imaging scan, the MT pulse is applied, but at the second time, the MT pulse is not applied, so that the contrast between the substantial part and the moisture is reduced. The lung field can be suitably imaged by calculating the difference between the lung field signals due to the MT effect in the above.

The imaging accompanying the application of the MT pulse may be based on a single imaging scan that does not execute the above-described difference processing. That is, FIG.
In the example described above, only the first imaging scan may be performed alone, and the echo signals collected by this may be reconstructed. Since the MR signal observed under the supply of atomized water is a water signal from inhaled water molecules, it is preferable to use the MT pulse in order to observe magnetic resonance with the lung parenchyma. is there.

In the present invention, a respiratory volume measurement value (cc) for one respiration is measured by using a well-known mouthpiece capable of measuring a respiratory volume, and the measured value or a state of change is measured. It is also possible to adopt a configuration of displaying a captured image. Thus, when diagnosing a patient with a pulmonary dysfunction such as pulmonary fiber, it is useful for comparative observation of both respiratory volume and morphological changes.

[0101]

As described above, according to the MRI apparatus and the MR imaging method of the present invention, atomized water is supplied to the lung field, and in this water supply state, the lung field is magnetically controlled based on the pulse sequence. , An echo signal is collected, and MR image data is generated from the echo signal. Therefore, the lung field, which has been considered difficult, can be easily imaged non-invasively without administering a contrast agent. .

Further, by using the breath-holding method and the ECG gating method together with this imaging, it is possible to provide a high-quality MR image with less body motion artifacts.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an example of a configuration of an MRI apparatus according to an embodiment of the present invention.

FIG. 2 is a view for explaining a temporal relationship between two imaging scans and a time zone of an imaging technique performed in parallel with each scan;

FIG. 3 is a schematic flowchart illustrating a procedure of a first imaging scan executed by a host computer;

FIG. 4 is a timing chart showing a flow of an imaging scan using the ECG gate method.

FIG. 5 is a schematic diagram showing a pulse sequence based on the ECG gating method in the first embodiment.

FIG. 6 is a schematic flowchart illustrating a procedure of a second imaging scan executed by the host computer.

FIG. 7 is a diagram illustrating a scan in which atomized moisture is not supplied and a scan in which it is supplied, together with an imaging area.

FIG. 8 is a schematic flowchart illustrating an example of image processing after echo collection.

FIG. 9 is a view for explaining a weighted difference process which is one process of image processing.

FIG. 10 is a diagram illustrating an overview of an imaging can according to the second embodiment.

FIG. 11 is a diagram illustrating an overview of an imaging can according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 1 magnet 2 static magnetic field power supply 3 gradient magnetic field coil unit 4 gradient magnetic field power supply 5 sequencer 6 host computer 7 RF coil 8T transmitter 8R receiver 10 arithmetic unit 11 storage unit 12 display 13 input device 16 sound generator 17 ECG sensor 18 ECG Unit 20 nebulizer (nebulizer) 21 nebulizer body 22 hose 23 suction mask

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Junichi Makita 2-16-4 Akabane, Kita-ku, Tokyo Toshiba Medical System Engineering Co., Ltd. F-term (reference) 4C096 AA07 AA18 AB01 AC04 AD27 BA04 DA18 DB06 FC14

Claims (10)

[Claims] 1. An MRI apparatus for obtaining an MR image of a lung field of a patient as a subject, comprising: a water supply means for supplying atomized water to the lung field; and a water supply to the lung field by the water supply means. Scanning means including means for magnetically scanning the lung field based on a pulse sequence in the state and collecting echo signals, and image generating means for generating data of the MR image from the echo signals collected by the scanning means An MRI apparatus comprising: 2. The invention according to claim 1, wherein the scanning means executes the scan a plurality of times over time in the lung field supplied with water by the water supply means to collect a plurality of sets of the echo signals. An MRI apparatus, wherein the image generating means is means for generating the MR image data from each of a plurality of sets of echo signals collected by the scanning means. 3. The invention according to claim 1, wherein said scanning means includes an SE as a pulse sequence.
An MRI apparatus, which is means for executing a scan using a (spin echo) system pulse sequence. 4. The invention according to claim 1, wherein said scanning means includes an FE as its pulse sequence.
An MRI apparatus, which is means for executing a scan using a (field echo) system pulse sequence. 5. The MRI apparatus according to claim 1, wherein the pulse sequence is a pulse sequence to which an MT pulse is added. 6. The invention according to claim 1, further comprising a time phase detecting means for detecting a signal representing the cardiac phase of the patient, wherein the scanning means comprises a heart beat included in the signal representing the cardiac time phase. An MRI apparatus, comprising: a scan start unit that starts the scan in synchronization with a reference waveform due to a predetermined delay time. 7. The invention according to claim 6, wherein the time phase detecting means is means for detecting an ECG signal of the patient as a signal representing the cardiac time phase, and the reference waveform is included in the ECG signal. An MRI apparatus, which is an R wave. 8. The MRI apparatus according to claim 1, further comprising breath-hold instruction means for giving a breath-hold instruction to the patient so as to hold a breath during scanning by the scanning means. 9. The first scanning unit according to claim 1, wherein the scanning unit scans a lung field of the patient without supplying water by the water supply unit to obtain a set of echo signals. And a second scanning unit that scans the lung field of the patient while supplying water by the water supply unit to obtain a set of echo signals. An MRI apparatus comprising means for generating MR image data relating to a pixel-by-pixel difference between two sets of echo signals obtained by each of the second scanning means. 10. An MR imaging method for obtaining an MR image of a lung field of a patient as a subject, wherein an imaging region including the lung field is supplied based on a pulse sequence while supplying or supplying atomized water to the lung field. An MR imaging method, comprising: magnetically scanning and collecting an echo signal; and generating data of the MR image from the echo signal.