JPH06237912A - Nuclear magnetic resonance device using grade magnetic field - Google Patents

Abstract

PURPOSE:To completely turn a grade magnetic field to '0' by automatically adjusting output offset by controlling signal strength so as to reproduce it in the state of disconnecting a power source by changing the output offset of the power source while monitoring the signal strength. CONSTITUTION:The measured nuclear magnetic resonance (NMR) signal strength is sent from a spectrometer 1 to a computer 3 and at certain timing corresponding to an adjustment sequence, the computer 3 sends the command signal of measurement start. A controller 4 for controlling a grade magnetic field power source 5 outputs the instruction of grade magnetic field OFF to the power source 5 and changes the output offset according to offset data. Namely, the computer 3 measures NMR, stores the signal strength and increases or decreases the offset data just for a suitable value. The NMR is measured again and the signal strength is compared with the stored signal strength. These operations are repeated and when the offset for the signal strength for reaching the target is found out, the adjustment is completed. The adjustment is performed by the computer 3, and the grade magnetic field is automatically controlled so as to be '0'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear magnetic resonance (NMR) device using a gradient magnetic field.

[0002]

2. Description of the Related Art Conventionally, in NMR imaging and field gradient NMR methods, a gradient magnetic field of an appropriate size is applied to a sample for a certain period of time for measurement. For example, as shown in FIG. 2, a sample is irradiated with a 90 ° pulse and G1 (positive gradient magnetic field) and G2 (negative gradient magnetic field) are applied in a state where a high frequency pulse is not irradiated, and a FID signal is given. Is detected, and a two-dimensional NMR spectrum can be obtained by detecting once by applying such a gradient magnetic field.

In the measurement using such a gradient magnetic field, the gradient magnetic field is completely reduced to 0 during a period in which the gradient magnetic field is not generated.
Otherwise, there is a problem that the magnetic field strength varies depending on the sample position, so that the spectrum spreads and the resolution decreases.

As shown in FIG. 3, the portion of the nuclear magnetic resonance apparatus using the gradient magnetic field that generates the gradient magnetic field has a gradient magnetic field coil 11 wound around the sample tube 10 and a current flowing through the gradient magnetic field coil 11. When a gradient magnetic field OFF command is issued from the controller 13, the gradient magnetic field does not become 0 completely if the power source 12 has an output offset. . Therefore, during the gradient magnetic field OFF period, it is necessary to adjust the power supply 12 in order to completely reduce the gradient magnetic field to 0. For this adjustment, the ammeter 14 is connected as shown in FIG.
The output offset of the power supply 12 is adjusted so that the reading of the ammeter 14 becomes 0 when the gradient magnetic field power is off.

[0005]

However, in such a conventional offset adjusting method of the gradient magnetic field power supply, when the ammeter 14 has an error, the current corresponding to the error flows to the gradient magnetic field coil 11. Gradient magnetic field is generated,
The gradient magnetic field cannot be completely zero.

The present invention is intended to solve the above problems, and provides a nuclear magnetic resonance apparatus using a gradient magnetic field capable of automatically adjusting the output offset of the gradient magnetic field power source to completely eliminate the gradient magnetic field. The purpose is to do.

[0007]

The present invention provides a high frequency coil for irradiating a sample with a high frequency, a gradient magnetic field coil for applying a gradient magnetic field to the sample, and a power supply for supplying power to the gradient magnetic field coil. In a nuclear magnetic resonance apparatus using a gradient magnetic field equipped with a detector for detecting a nuclear magnetic resonance signal from a sample, changing the output offset of the power source while monitoring the detection output from the detector, It is characterized in that it is provided with control means for changing the output offset so as to obtain the signal strength in the state where the coil is not supplied with power.

[0008]

According to the present invention, first, a sufficiently high resolution can be obtained without connecting the gradient magnetic field power source, and then the power source is connected. At this time, if the power source has an offset and the gradient magnetic field is generated, the resolution becomes high. Since the signal strength drops, the signal strength decreases, so that the output offset of the power supply is changed while monitoring this signal strength to reproduce the signal strength without the power supply connected. In the above, since it is directly confirmed whether or not an extra magnetic field is generated, accurate offset adjustment can be performed and a series of adjustment procedures can be automated.

[0009]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In the figure, 1 is a spectrometer, 2 is an RF coil, 3 is a computer, 4 is a controller, 5 is a power source, 6 is a sample tube, and 7 is a magnetic field gradient coil.

The spectrometer 1 sends the measured NMR signal intensity to the computer 3, and the computer 3 sends a command signal to start the measurement at a timing suitable for the adjustment procedure. The controller 4 for controlling the gradient magnetic field power supply 5 outputs an instruction to turn off the gradient magnetic field to the power supply 5. The power supply 5 changes the output offset according to the offset data received from the computer 3.

Next, the operation will be described. First, a sample from which a clear NMR signal is obtained without connecting the gradient magnetic field power source 5 or energizing the power source is set in the sample tube 6 and the high frequency magnetic field generated by the RF coil 2 is applied. The resolution of the signal obtained by application is increased. After the adjustment of the resolution is completed, NMR measurement is performed under appropriate conditions and the signal intensity is stored in the computer 3 as a target value. After that, the power source 5 is connected (or the power source is energized) and the computer 3 is instructed to start the adjustment.

That is, the computer 3 performs NMR measurement and stores the signal intensity. Increase or decrease the offset data by an appropriate value. The NMR measurement is again performed, and the signal intensity is compared with the stored signal intensity. As a result of the comparison, when the signal strength is strong, the offset data is changed in the same direction as, and when the signal strength is weak, the offset data is changed in the opposite direction. If the offset data that the signal strength reaches the target value is found by repeating the above steps, the adjustment ends. The offset output is adjusted by the computer 3 and can be automatically adjusted so that the gradient magnetic field becomes zero.

The present invention is not limited to the above embodiment, but when the nuclear magnetic resonance apparatus has an NMR lock function, the gradient magnetic field can be set to 0 in the same manner by referring to the lock signal strength. is there.

[0014]

As described above, according to the present invention, by referring to the MR signal itself, an accurate offset adjustment can be performed irrespective of the measurement error of an ammeter or the like, and a series of adjustment procedures can be automated. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating an NMR measurement using a gradient magnetic field.

FIG. 3 is a diagram illustrating NMR measurement using a gradient magnetic field.

FIG. 4 is a diagram for explaining output offset adjustment of NMR measurement using a conventional gradient magnetic field.

[Explanation of symbols]

1 ... Spectrometer, 2 ... RF coil, 3 ... Computer, 4 ...
Controller, 5 ... Power source, 6 ... Sample tube, 7 ... Coil for magnetic field gradient.

Claims (1)

[Claims] 1. A high frequency coil for irradiating a sample with a high frequency, a gradient magnetic field coil for applying a gradient magnetic field to the sample, and a power supply for supplying power to the gradient magnetic field coil.
In a nuclear magnetic resonance apparatus using a gradient magnetic field equipped with a detector for detecting a nuclear magnetic resonance signal from a sample, changing the output offset of the power source while monitoring the detection output from the detector, A nuclear magnetic resonance apparatus using a gradient magnetic field, comprising control means for changing an output offset so as to obtain a signal strength in a state where power is not supplied to a coil.