JPS60242845A - Processing of nuclear magnetic resonance data - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method for observing internal tissue using nuclear magnetic resonance. In particular, it relates to correction of image data in a nuclear magnetic resonance computer tomography apparatus.

[Conventional technology]

Data obtained by nuclear magnetic resonance computed tomography equipment contains various types of noise, so it cannot be reconstructed into an image as is. Many of these noises can be corrected by mathematically processing physical characteristics. However, device-specific noise cannot be corrected using general methods.

The reference values for correction of such noise are not clear, and therefore the parameters and image levels vary depending on the device. An example is that the DC level of the image data changes from view to view due to variations in amplifier gain or analog-to-digital converter offset.

As a method for correcting changes in the DC level, a method is known in which the average value of received data near the end of each view is used and this is used as the offset of each view. This is because nuclear magnetic resonance diagnostic equipment collects data for a sufficiently longer period of time than the time it takes to obtain a signal, so the data in the latter part of each view contains almost no signal components, and the This method takes advantage of the fact that the offset value is the DC component of .

By averaging this data over a suitable time interval and subtracting it from the data of that view as an offset value, it is possible to correct changes in offset that vary from view to view.

However, with this method, it is not possible to perform sufficient correction when the offset changes slowly within one view due to fluctuations in high-frequency pulses or gradient magnetic fields, that is, when the offset has a slope. There were drawbacks.

[Problems to be Solved by the Invention] An object of the present invention is to improve the quality of reconstructed diagnostic images by correcting the direct current component of observation data obtained by nuclear magnetic resonance.

[Means for solving problems]

In the nuclear magnetic resonance data processing method of the present invention, a static magnetic field, a high-frequency pulse that gives nuclear magnetic resonance, and a gradient that reflects position information in a signal are placed in a magnet assembly that can be inserted into the inside of the magnet assembly. In a nuclear magnetic resonance data processing method, a nuclear magnetic resonance signal is observed by applying a magnetic field, and a calculation is performed to construct a nuclear magnetic resonance image from the signal. The above calculation is performed for the case where the object is inserted and the case where the object is inserted, and the above calculation includes an operation for correcting the observation data when the object is inserted by the observation data when the specific object is inserted. shall be.

Here, as the specific object, a substance whose properties are known, such as air or water, is used.

[Effect]

The method of the present invention is characterized in that at least one of before and after collecting data on the subject, data on air without a subject is collected, and image data is corrected using this data.

〔Example〕

FIG. 1 is a block diagram of a nuclear magnetic resonance computer tomography apparatus according to an embodiment of the present invention.

The Macnet assembly 1 includes a static magnetic field coil 2 that applies a constant magnetic field to a subject, an excitation coil 3 that provides a high-frequency pulse to excite the spin of an atomic nucleus, and a coil that reflects information on the position of the subject in a signal. The present invention includes a gradient coil 4 that applies a gradient magnetic field, and a detection coil 5 that detects nuclear magnetic resonance signals from within the subject. FIG. 1 shows a portion of each of these coils.

The control computer 11 is connected to the sequence storage circuit 12. The sequence storage circuit 12 is connected to a gradient magnetic field drive circuit 13. The gradient magnetic field drive circuit 13 is connected to the gradient coil 4 . The static magnetic field power supply 14 is connected to the static magnetic field coil 2 . High frequency oscillator 15 is connected to gate modulation circuit 16 and phase detection circuit 19. The gate modulation circuit 16 is connected to a high frequency power amplifier 17 and a phase detection circuit 19. High frequency power amplifier 17 is connected to excitation coil 3 . The detection coil 5 is connected to a preamplifier 18. Preamplifier 18
is connected to the phase detection circuit 19. Phase detection circuit 19 is connected to data storage device 20 . data storage device 20
is connected to the ink face circuit 21. The ink face circuit 21 is connected to a data processing computer 22. The data processing computer 22 is connected to a display device 23 and a magnetic disk storage device 24 .

The control computer 11 controls the operation of the device of this embodiment. Furthermore, by rewriting the contents of the sequence storage circuit 12, various operation sequences can be realized.

The sequence storage circuit 12 generates a timing signal for collecting observation data of nuclear magnetic resonance signals, and controls the operation of the gradient magnetic field drive circuit 13 and the gate modulation circuit 16. Thereby, the sequence storage circuit I2 controls the generation sequence of gradient magnetic fields and high-frequency pulses.

The gradient magnetic field drive circuit 13 is connected to each of the X-axis, y-axis, and Z-axis gradient coils 4, and applies a gradient magnetic field within the magnet assembly.

The high-frequency oscillator 15, the gate modulation circuit 16, and the high-frequency power amplifier 17 apply high-frequency pulses to the air or the object in the magnet assembly 1 to excite atoms constituting the air or the object.

High frequency oscillator 15 generates a high frequency signal. The gate modulation circuit 16 modulates the high frequency signal output from the high frequency oscillator 15 using the timing signal from the sequence storage circuit 12 to form a high frequency pulse. High frequency power amplifier 17
power amplifies the high frequency pulse output from the gate modulation circuit 16 and supplies it to the excitation coil 3.

Preamplifier 1B and phase detection circuit 19 collect nuclear magnetic resonance signals. The preamplifier 18 amplifies the nuclear magnetic resonance signal detected by the detection coil 5. The phase detection circuit 19 refers to the output signal of the high frequency oscillation circuit 15 and performs phase detection on the output of the preamplifier 18 . Observation data obtained thereby is stored in the data storage device 20 and sent to the data processing computer 22 through the ink face circuit 21.

The feature of the present invention lies in the control sequence of this device. That is, the data processing computer 22 stores observation takes of the air and the object in the magnetic disk storage device 24, further corrects the observation data of the object using the air observation data as correction data, and uses this observation data. It is reconstructed into an image and displayed on the display device 23.

FIG. 2 is a flowchart showing the collection of correction data by the apparatus of this embodiment.

The correction data is collected for the air inside the magnet assembly 1 under the same conditions and with the same parameters as the actual data collection. Air observation data is collected and averaged for the required number of views, and the data obtained thereby is recorded in the correction file of the magnetic disk storage 1a device 24.

The correction data recorded in the correction file represents changes in the offset during one view of the amplifier and analog-to-digital converter provided in this device.

FIG. 3 is a flowchart showing correction of observation data of a subject by the apparatus of this embodiment.

Correction data is subtracted from the observation data of all views on a per-view basis, further image processing calculations are performed, and this data is stored in the magnetic disk storage device 24 again as image data. Thereby, images can be displayed on the display device 23 as needed.

In this embodiment, the observation data of the air of the magnet assembly I was used as the correction data, but the present invention can also be practiced using water or other specific substances.

As an application of the present invention, the object to be inspected is placed in the magnet assembly 1.
The present invention can also be carried out by a method in which data is collected by applying a gradient magnetic field without applying a high-frequency pulse, and this data is used as offset data on the receiving side.

In addition to subtraction, there are many correction methods such as division for normalization, multiplication and addition using reciprocals, and calculations after taking logarithms. The present invention can be implemented using these devices as well.

〔Effect of the invention〕

As explained above, by the data processing method using nuclear magnetic resonance of the present invention, it becomes possible to easily correct the offset amount that constantly changes during one view. As a result, clear diagnostic images can be obtained, which is highly effective in medical diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a nuclear magnetic resonance computer tomography apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart showing the collection of correction data. FIG. 3 is a flowchart showing correction of observation data of a subject. DESCRIPTION OF SYMBOLS 1... Magnet assembly, 2... Static magnetic field coil, 3... Excitation coil, 4... Gradient coil, 5...
Detection coil, 11... Control computer, 12... Sequence storage circuit, 13... Gradient magnetic field drive circuit, 14...
- Static magnetic field power supply, 15... High frequency oscillator, 16... Gate modulation circuit, 17... High frequency power amplifier, 18...
- Preamplifier, 19... Phase detection circuit, 20... Data storage device, 21... Ink face circuit, 22.
...Data processing computer, 23...Display device, 24...
・Magnetic disk storage device. Patent applicant Representative patent attorney Naotaka Ide N2 Figure No. 31

Claims (1)

[Scope of Claims] +l) A static magnetic field, a high-frequency pulse that gives nuclear magnetic resonance, and a gradient magnetic field that reflects position information in a signal are applied to a magnet assembly that has a shape that allows the subject to be inserted into the magnet assembly. In the method for processing nuclear magnetic resonance data, the observation is performed when a specific object is inserted into the magnet assembly. and the case where the object is inserted, and the above calculation includes an operation for correcting the observation data when the object is inserted by the observation data when the specific object is inserted. How to process resonance data. (2) Claim No. (1) in which the specific object is air
The method for processing nuclear magnetic resonance data described in Section 1. (3) Claim No. 11 in which the specific object is water
The method for processing nuclear magnetic resonance data described in Section 1.