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Magnetic body thermostatic control device and method for permanent-magnet magnetic resonance imaging systems

A magnetic resonance imaging and constant temperature control technology, applied in temperature control, magnetic resonance measurement, non-electrical variable control, etc. effect, reduce overshoot, improve image quality

Inactive Publication Date: 2007-07-04
NEUSOFT MEDICAL SYST CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If the parameter setting is not good, resulting in divergent oscillation or constant amplitude oscillation of the system, the center frequency of the magnet ω 0 (ω 0 =γB 0 , where γ is the magnetic spin ratio, hydrogen proton 1 The H magnetic gyration ratio is 42.56MHz / T) will also change continuously with the oscillation of the magnet temperature, which will affect the quality of the image
[0006] In order to improve the thermal stability of permanent magnets, this problem is usually solved by configuring the constant temperature control system of permanent magnets. In the prior art, AC heating is used. Although the permanent magnets can be guaranteed to work at a constant temperature, AC When heated, its alternating current generates an electromagnetic field, which also affects the magnetic resonance system. At the same time, because the controlled object is a permanent magnet with a weight of about 13 tons or 20 tons, the lag time is long, and the conventional self-tuning method cannot be used. Obtain the control parameter K of PID in the constant temperature control system p ,T i and T d range

Method used

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  • Magnetic body thermostatic control device and method for permanent-magnet magnetic resonance imaging systems
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  • Magnetic body thermostatic control device and method for permanent-magnet magnetic resonance imaging systems

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Embodiment 1

[0029] The present invention is designed to improve the thermal stability of the permanent magnetic field in the permanent magnetic resonance imaging system. The automatic control of its constant temperature is realized by a closed-loop method. The working principle is shown in Figure 1. The target set value r(t) decreases To measure the value y(t), get the deviation e(t), the deviation e(t) is the input quantity of the PID process regulator, and the control quantity u(t) of the PID process regulator is shown in formula (1):

[0030] u(t)=K p [e(t)+1 / T i ∫e(t)dt+T d ×de(t) / dt] (1)

[0031] Among them: K p is the proportional coefficient;

[0032] T i is the integral time constant;

[0033] T d is the differential time constant;

[0034] Choose the appropriate K p ,T i and T d The control quantity u(t) of the regulator controls the duty cycle of the solid state relay, thereby controlling the output power of the electric heating body, so that the control p...

Embodiment 2

[0068] The difference from Embodiment 1 is that in this embodiment, K in process S3-5 p , T i , T d The setting parameters are respectively 10, 100 seconds, and 100 seconds. After testing, the system has a shorter response time and better stability. After testing, the offset of the magnet center frequency of the first type of permanent magnetic resonance imaging system was reduced from the original ±1500Hz to ±700Hz; the offset of the magnet center frequency of the second type of permanent magnetic resonance imaging system Reduced from the original ±2200Hz to ±1100Hz.

[0069] In actual shimming, if the magnetic field strength value within the range of +Z6~+Z1 (relative physical position calibration in the magnetic field action area, there are thirteen areas from -Z6 to +Z6) is greater than the center frequency value of the magnet, then Increase the Mr value of the first temperature controller TC1 of the upper pole head; if the magnetic field strength value within the range...

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Abstract

The invention discloses a permanent magnetism magnetic resonance imaging system magnet thermostatic control device. It includes alternating current temperature control circuit, the signal input end of temperature controller is linked with temperature sensor, and the regulating output end of temperature controller is linked into the alternating current power supply circuit of alternating current heater through the alternating current performer; and includes the direct current temperature control circuit consists of temperature sensor, temperature controller, direct current source and direct current heater. Among them, said regulating output end of temperature controller is linked into the direct current power supply circuit of direct current heater through the direct current performer, the alarm output end of temperature controller is linked into the alternating current power supply circuit of alternating current heater through the alternating current performer; the signal output end of temperature sensor, direct current heater and the power receiving terminal of alternating current heater are equipped with filter respectively; said temperature controller stores temperature control programs. The invention improves the thermal stability of permanent magnet, and has high control accuracy and ratio of performance to price.

Description

technical field [0001] The invention relates to a large-scale medical imaging equipment, in particular to a permanent magnet magnetic resonance imaging system magnet constant temperature control device and method. Background technique [0002] Magnetic resonance imaging (MRI, Magnetic Resonance Imaging) is a high-tech imaging based on the performance characteristics of biological magnetic nuclei (hydrogen nuclei) in a magnetic field. It is widely used in the field of clinical medical imaging. It is currently the most advanced and One of the most expensive diagnostic equipment. [0003] The permanent magnet magnetic resonance imaging system is composed of a permanent magnet subsystem, a gradient subsystem, a radio frequency subsystem, a computer and an image processing subsystem, etc. Among them, the permanent magnet is the key component of the magnetic resonance imaging system, and its performance directly It is related to the signal-to-noise ratio of the system, and thus d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): A61B5/055G01R33/20G05D23/00
Inventor 张桂娟秦松茂施金泉郑友群李波郝敬
Owner NEUSOFT MEDICAL SYST CO LTD
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