JPS60222758A - Inspector employing nuclear magnetic resonance - Google Patents

Abstract

PURPOSE:To shorten the measuring time by measuring signals from a plurality of nuclides containing an object to be inspected within almost at the same time length as that when a signal is measured from a single nuclide. CONSTITUTION:When the imaging of <1>H and the chemical shift of <31>P are measured, <1>H is measured in the section A and <31>P in the section B. In the section A, upon the application of a 90 deg. high frequency magnetic field, an slant magnetic field Gz is applied to a slice vertical to the direction Z is selected. Subsequently, a 180 deg. high frequency magnetic field is applied to invert the magnetization and an echo signal generated at the time t0 is detected under a slant magnetic field Gxy. Since the frequency fn of the high frequency magnetic field applied in the section A differs from the resonance frequency fp measured in the section B, no interference is caused. Because the magnetization of <31>P is in the direction of magnetostatic fields, the effect of the slant magnetic field applied in the section A vanishes the moment the slant magnetic field is made OFF and thus, in noway causes such an effect as the high frequency magnetic field does.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to 1H23"P contained in a subject.

The present invention relates to an apparatus suitable for detecting nuclear magnetic resonance signals from 23Na or the like and measuring the internal structure of an object, relaxation time distribution, chemical shift distribution, etc. of the object.

[Background of the invention]

2. Description of the Related Art Conventionally, X-ray CT and ultrasonic imaging devices have been widely used as devices for non-destructively inspecting internal structures such as the head and head of a human body. In recent years, attempts to perform similar tests using the nuclear magnetic resonance (NMR) phenomenon have been successful, and it has become clear that information that cannot be obtained with X-ray CT or ultrasound imaging devices can be obtained.

Inspection device using NMR phenomenon (hereinafter simply referred to as “inspection device j”)
), it is necessary to separate and identify signals from an object to be inspected in correspondence with each part of the object. One method for this purpose is to apply a gradient magnetic field to the target object to vary the static magnetic field placed on each part of the target object, thereby varying the resonant frequency or phase shift of each part of the target object, thereby obtaining position information. There is a way to get it.

This method is described, for example, in Proc, IEEE, 71.33.
8 (1983°Proc, IEEE, 70.11
52 (1982), etc., so it is omitted here, but the signal from the object to be inspected is
For each measurement, it was limited to one type of nuclear spin.

Therefore, when performing 1H imaging and 31p imaging or localized measurements, it was customary to perform IP measurements (or vice versa) after 1H measurements were completed. Now, in the NMR phenomenon, after a measurement is completed, it is necessary to wait for the recovery of the nuclear spin to perform the next measurement, and this is actually a factor that determines the imaging time. The time required for recovery varies depending on the type of subject, but is usually about 1 second. Therefore, the time required for imaging is approximately several minutes, and 1H and 3H
Since it takes more time to measure jp, it has been desired to shorten the time.

[Purpose of the invention]

The present invention was developed in view of these drawbacks, and its purpose is to measure signals from multiple nuclides contained in an object to be inspected within approximately the same time as it would take to measure a signal from a single nuclide. An object of the present invention is to provide an inspection apparatus using NMR, which is suitable for significantly shortening measurement time.

[Summary of the invention]

In conventional imaging, for example, 1H
When targeting a target object, a tomographic image was constructed by applying a high-frequency magnetic field with a resonance frequency expressed by f=γH/2π to the target object, and detecting and processing the resulting signals. Here, γ is the nuclear gyromagnetic ratio, and H is the static magnetic field that the target nucleus receives. In order to perform imaging, gradient magnetic fields are also applied, but most of the measurement is spent waiting for the magnetization to recover, and during that period, neither the radio-frequency magnetic field nor the gradient magnetic field is applied at all. As a way to make use of this wasted time, we devised a method to measure multiple nuclides. In other words, since γ is a value unique to the nucleus, the same H
On the other hand, since different nuclides have different resonance frequencies f, this method utilizes the fact that even if other nuclides are measured during the wasted time, no interference will occur between the nuclides. As a result, when measuring multiple nuclides, the measurement time is determined by the nucleus that requires the longest measurement time, and is not the sum of the time required to measure each nucleus, making it possible to significantly shorten the measurement time. Become.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the configuration of an inspection device that is an embodiment of the present invention. □ In the figure, a control device 1 outputs various commands to each device at a constant timing. The output of the high frequency pulse generator 2 is amplified by an amplifier 3 and excites a coil 4. The coil 4 also serves as a receiving coil, and the received signal component passes through an amplifier 5, is detected by a detector 6, and then sent to a signal processing device 7.
is converted to an image. The output of the high frequency pulse generator 2 is
It is used as a reference signal when quadrature phase detection is performed by the wave detector 6. The generation of gradient magnetic fields in the Z direction and in the direction perpendicular thereto is carried out by coils 8, 9.10, respectively, which are driven by amplifiers 11, 12.13, respectively.

The static magnetic field is generated by a coil 14, and the coil 14 is driven by a power source 15. .

The coil 10 has the same shape as the coil 9, is rotated 90 degrees around the Z axis, and generates gradient magnetic fields orthogonal to each other. A human body 16 to be examined is placed on a bed 17, and a bed 17 is moved on a support stand 18. -λ FIG. 2 shows the pulse sequence ζ□ used in the present invention. This is a case where 1H imaging and 31p chemical shift are measured, and IH is measured in section A and 3''P is measured in section B.The imaging method and □' are projection reconstruction methods. In section A, a gradient #a field G2 is applied simultaneously with the application of a 90' high frequency magnetic field to select a slice perpendicular to the Z direction.Next, a 180' high frequency magnetic field is applied to reverse the magnetization, and at time t The echo signal generated at .G is detected under a gradient magnetic field Gxy.
xy is a magnetic field that is a composite of gradient magnetic fields Gx and Gy that are orthogonal to each other, and is a gradient magnetic field that changes the direction of the composite vector while keeping its magnitude constant depending on the projection angle. Frequency f1 of the high frequency magnetic field applied in section A. teeth,
If the static magnetic field H is 1.5 T, fh264 M +-
It becomes 1z. On the other hand, the resonance frequency fp of 31p measured in section B is fρ = 26 MHz with respect to the static magnetic field.
Therefore, the high frequency magnetic field applied to measure 1H has no effect on 3゛P. Therefore, the signal of 31p can be measured completely independently of section A. In addition, the influence of the gradient magnetic field applied in section A on 3"P is also 31
Since the magnetization of p is oriented in the direction of the static magnetic field, it disappears as soon as the gradient magnetic field is turned off, and has no effect at all like the high-frequency magnetic field.

FIG. 3 shows, as a second embodiment of the present invention, a case where a signal including the effect of the longitudinal relaxation time TI is observed after a td waiting time after reversing the 1H magnetization. Measurement of 21 P is also carried out during the td time. Of course, 31p can be measured even while waiting for recovery of 1H magnetization, as in the case shown in FIG. 2.

In the above embodiments, 1H is measured first and then 31p is measured, but the reverse is of course possible.

However, when measuring the chemical shift of 3+p, it is desirable to measure 1H first. Furthermore, measurement of 31p is not limited to chemical shifts at minute sites, but also density distribution.

This method can also be used when measuring chemical shift distribution. In that case, instead of the sequence of section B shown in FIG. 2, for example, 5ociety of
Magnetic Re5onance in Med
icine's 5econd Annual Meeti
ng, August16-19.1983゜San
Francisco, P in Ca1ifornj, a.
, A. Bottomley's report (P., 53
The sequence described in ~P54) may be used.

Note that multi-slice imaging has been proposed as one way to effectively utilize measurement time. This detects signals from other slice planes while waiting for magnetization to recover, but even in this case, it is sufficient to measure P using part of the time it takes to measure multiple slices, and the slice plane It only decreases by one.

Furthermore, as an extension of this, 31 p imaging can also be multi-sliced. In this case,
Measurements of 1H and 31p may be repeated alternately on a plurality of slices.

So far, we have only talked about the combination of 1H and 3IP, but this combination is not limited to 23N a.

It is clear from the above explanation that two or more types of nuclides such as 19F can be measured simultaneously.

Finally, although the embodiment shown here deals with two-dimensional imaging, the present invention is of course applicable not only to two-dimensional imaging but also to three-dimensional imaging.

〔Effect of the invention〕

According to the present invention, a plurality of nuclides can be measured within the time it takes to measure one type of nuclides, so the measurement time can be significantly reduced.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. Magnetic field generating means for a static magnetic field, a gradient magnetic field, and a high-frequency magnetic field, a signal detecting means for detecting a nuclear magnetic resonance signal from an object to be examined, and calculating a detection signal of the signal detecting means. What is claimed is: 1. An inspection device using nuclear magnetic resonance, which includes a computer and means for outputting calculation results from the computer, and is characterized in that it measures a plurality of nuclides in a time-sharing manner. 2. Nuclear magnetic resonance according to claim 1, characterized in that after excitation and signal detection of one nuclide are completed, excitation and signal detection of another nuclide are performed while waiting for recovery of nuclear magnetization. An inspection device using 3. Imaging of multiple sections for two nuclides, 1
Claim 1 characterized in that the imaging of the cross section is completed within approximately the same measurement time, and at the same time, the measurement of other nuclides is carried out within the time period for waiting for the recovery of the nuclear magnetization of the nuclide.
An inspection device using nuclear magnetic resonance as described in Section 1. 4. Using nuclear magnetic resonance according to claim 1, wherein the magnetization of one nuclide is reversed and the excitation and signal detection of other nuclides are performed even while waiting for its recovery. Inspection equipment.