JP6721465B2 - Magnetic resonance imaging apparatus and maintenance system using the magnetic resonance imaging apparatus - Google Patents

Description

The present invention relates to a superconducting magnet, a magnetic resonance imaging apparatus (hereinafter, referred to as an MRI apparatus), a maintenance system and a maintenance method using the MRI apparatus, and particularly to early occurrence of blockage in a pipe provided in the superconducting magnet. Regarding detection technology.

An MRI device that arranges a subject in a uniform magnetic field space and performs medical diagnosis from its nuclear magnetic resonance (hereinafter, referred to as NMR) signal is a conventional X-ray CT device or a nuclear medicine device (RI device). It is used in medical institutions like inspection. In particular, an examination using an MRI apparatus has excellent lesion detection ability because it is a variety of examinations that image morphological information and functional information such as metabolism.

In order to obtain an image with excellent lesion detection capability with this MRI device, it is necessary to place the examination site of the subject in a uniform static magnetic field space with high magnetic field strength and its deviation in the PPM order. It is known that the following problems occur when the magnet is composed of a superconducting magnet.

That is, in Patent Document 1, it is described that air flows in from the gap of the pipe of the superconducting magnet, the air is solidified, and clogging occurs, and in Patent Document 1, particularly, about detecting the position of the clogging. The technology is disclosed.

Specifically, in Patent Document 1, the measured value by the pressure sensor provided in the pipe is compared to determine whether it is larger or smaller than a predetermined value, and based on the comparison result, the closed position is exhausted from the position of the pressure sensor. It was determined whether it was closed at a portion near the valve or at a position closer to the refrigerant container than the pressure sensor.

Japanese Patent Laid-Open No. 2008-154677

However, the technique described in Patent Document 1 does not consider the occurrence of pipe blockage as early as possible and with high accuracy in time.

Conventionally, when inspecting a cryocooler attached to a pipe, the inside of the pipe was visually checked, and the amount of gas flow was checked by opening the atmosphere release valve.

Therefore, an object of the present invention is to provide a maintenance system and a maintenance method using a superconducting magnet, an MRI apparatus, and an MRI apparatus capable of early and accurately detecting the occurrence of blockage in a pipe provided in the superconducting magnet. To do.

In order to achieve the above object, according to the present invention, a superconducting coil for generating a static magnetic field in a desired space, a coil container for accommodating the superconducting coil together with liquid helium as a refrigerant, and surrounding the coil container. And, a vacuum container whose inside is kept vacuum, a pipe provided on the upper part of the coil container, and a pressure in the coil container, so as to keep the pressure in the coil container so as not to become a negative pressure, In a superconducting magnet composed of a heater 4 and its control line for vaporizing and adjusting the liquid helium, and a pressure gauge provided on the room temperature side of the pipe, blockage occurred on the coil container side of the pipe. A superconducting magnet is provided, which is provided with a discriminating unit for discriminating the above based on the variation of the fluctuation rate per unit time of the measurement value measured by the pressure gauge for a predetermined time.

According to the present invention, it is possible to provide a superconducting magnet, an MRI apparatus, and a maintenance system and a maintenance method using the MRI apparatus, which are capable of early detection of a blockage in a pipe provided in the superconducting magnet. ..

Sectional structure of superconducting magnet according to Example 1 of the present invention Diagram showing fluctuation of measured value when measuring pressure value by differential pressure method Diagram showing the fluctuation of pressure value with a histogram Block diagram of an MRI apparatus using a superconducting magnet according to Embodiment 1 of the present invention Operation flow of MRI apparatus using superconducting magnet according to Example 1 of the present invention Example 2 Cross-sectional structure of a superconducting magnet according to Example 2 of the present invention Operation flow of MRI apparatus using superconducting magnet in Example 2 of the present invention

Preferred embodiments of a superconducting magnet, an MRI apparatus, a maintenance system and a maintenance method using the MRI apparatus of the present invention will be described below with reference to the accompanying drawings. In all the drawings for explaining the embodiments of the invention, components having the same function are designated by the same reference numeral, and the repeated description thereof will be omitted.

First, FIG. 1 is a cross-sectional structure of a superconducting magnet 100 according to a first embodiment of the present invention. According to FIG. 1, the superconducting magnet 100 is a superconducting coil 101 for generating a magnetic field of 1.2T, 1.5T, 3T or the like by flowing electricity in a superconducting state, and the superconducting coil 101 is a liquid helium 102 as a refrigerant. A coil container 103 to be housed together, a vacuum container 104 that surrounds the coil container 103 and is maintained in a vacuum, and a refrigerator 105 connected to a refrigerator insertion hole provided in the upper portion of the coil container 103. A pipe (service port) 108 provided on the coil container 103 and connecting the low temperature side helium bath 106 of the coil container 103 and the coil container normal temperature side space 107, and provided on the coil container normal temperature side space 107 side of the pipe 108. It consists of a pressure gauge 109.

Further, a heater 110 is arranged inside the coil container 103, and is connected to an external control unit 12 via a control line 111. The control unit 12 keeps the pressure in the coil container 103 by energizing the heater 110 to vaporize the liquid helium 102 so that the pressure in the coil container 103 measured by the pressure gauge 109 does not become a negative pressure. ing.

Therefore, when the pressure gauge 109 measures the pressure by the differential pressure type with the atmospheric pressure, in the normal case, the measurement value by the pressure gauge 109 is controlled to a certain constant value so as not to be a negative pressure. ..

However, in the vicinity of the coil container 103 side of the pipe 108 due to the inflow of air into the pipe 108 (specifically, at a place deeper than the position where the radiation shield in the pipe is bonded from the outside to the coil container side: the pipe low temperature side 112). When the blockage occurs, the coil container room temperature side space 107 is separated from the low temperature side helium bath 106, and the measured value by the pressure gauge 109 energizes the heater 110 attached to the low temperature side to vaporize the liquid helium 102. Pressure will not change.

Specifically, the value measured by the pressure gauge 109 changes with atmospheric changes, while the blockage near the coil container 103 side of the pipe is not a complete block, a minute leak occurs, and a long time Then, the state shifts to the initial state of the pressure measurement value (the state in which the pressure in the space 107 on the pipe normal temperature side and the pressure in the low temperature side helium tank 106 become substantially the same).

Specifically, FIG. 2 is a diagram showing the fluctuation of the measured value when the pressure is measured by the differential pressure type, in which the horizontal axis is the time axis and the vertical axis is the pressure value. However, the broken line 201 is the fluctuation of the pressure value when the pipe 108 is not blocked, while the solid line 202 is the fluctuation of the pressure value when the pipe 108 is blocked. According to this, when there is no blockage in the pipe 108, the value of the pressure gauge 109 for measuring the pressure by the differential pressure formula is almost unchanged (broken line 201), whereas when there is a blockage in the pipe 108, It is shown that the value fluctuates positively and negatively (solid line 202).

Then, when this variation is represented by a histogram which is a frequency distribution of the time variation of the pressure value, it becomes as shown in FIG. FIG. 3(a) is a frequency distribution when there is no blockage in the pipe 108, and there is no variation in the fluctuation width (time change rate) of the differential pressure type pressure gauge 109 arranged in the pipe 108. (b) is the frequency distribution when the pipe 108 is blocked, and it can be seen that the fluctuation range (rate of change over time) of the differential pressure type pressure gauge 109 arranged in the pipe 108 varies.

Therefore, in the MRI apparatus using the superconducting magnet 100 according to the first embodiment of the present invention, it is detected that the inside of the pipe 108 is blocked by evaluating the variation in the fluctuation range (time change rate) of the measurement value by the pressure gauge 109. To do.

FIG. 4 is a block diagram of a part of the MRI apparatus using the superconducting magnet 100 according to the first embodiment of the present invention. According to FIG. 4, the pressure gauge 109 provided in the superconducting magnet 100 is connected to a control device such as a CPU in the MRI apparatus, for example.

In the control unit 12, connected to the pressure gauge 109, the pressure acquisition unit 12-1 for acquiring the pressure value measured by the pressure gauge 109, and the pressure acquisition unit 12-1, and the pressure acquisition unit 12-1. From the collected measured value data for a certain amount of time, connected to the fluctuation rate calculation unit 12-2 for calculating the fluctuation rate of the measurement value (differential pressure) per unit time, and the fluctuation rate calculation unit 12-2, Connected to the standard deviation calculation unit 12-3 and the standard deviation calculation unit 12-3, which calculates the value of standard deviation (σ), which is one of the fluctuations in the fluctuation ratio calculated by the fluctuation calculation unit 12-2, and is connected to the standard deviation calculation unit 12-3. A discriminating unit 12-4 for discriminating whether the value of the standard deviation calculated by the deviation calculating unit 12-3 is equal to or more than a threshold value is arranged.

Next, FIG. 5 is a diagram showing an operation flow of the MRI apparatus using the superconducting magnet 100 according to the first embodiment of the present invention. Each step of FIG. 5 will be described in order.

(Step S501)
The pressure acquisition unit 12-1 in the control unit 12 (for example, CPU) provided in the MRI apparatus or the maintenance system thereof using the superconducting magnet 100 according to the present invention acquires the pressure value measured by the pressure gauge 109. ..

(Step S502)
The fluctuation rate calculation unit 12-2 in the control unit 12 collects the measurement value data acquired by the pressure acquisition unit 12-1 for a certain period of time, excludes the measurement value data equal to or more than the specified value, and removes the remaining data. Calculate the fluctuation rate of the measured value (differential pressure) per unit time. Here, the reason for excluding the measured value data of the specified value or more is that when a power failure or an intentional stoppage of the refrigerator operation occurs in the superconducting magnet 100, the pressure in the coil container increases, so such an event is excluded. This is because

(Step S503)
The standard deviation calculation unit 12-3 in the control unit 12 calculates the standard deviation of the fluctuation rate from the fluctuation rate of the measurement value (differential pressure) per unit time calculated by the fluctuation rate calculation unit 12-2.

(Step S504)
The discriminating unit 12-4 in the control unit 12 discriminates whether the value of the standard deviation σ of the fluctuation rate calculated by the standard deviation calculating unit 12-3 is equal to or larger than a preset threshold value. When it is larger than the threshold value, the pipe 108 of the superconducting magnet 100 is blocked and abnormal. When it is less than the threshold value, it is judged that the pipe 108 of the superconducting magnet 100 is not blocked and is normal.

According to the MRI apparatus using the superconducting magnet 100 according to the first embodiment of the present invention, the statistic of the variation rate of the measurement value of the pressure gauge 109 arranged in the pipe 108 is evaluated, and the superconducting magnet 100 is based on the statistic. There is an advantage that the occurrence of blockage in the pipe 108 can be detected with high accuracy at an early stage, and there is also an advantage that it is convenient to detect the blockage because it is not necessary to visually check the inside of the pipe 108.

However, although the differential pressure type is used as the pressure gauge 109 in the first embodiment, an absolute pressure type may be used as the pressure gauge 109. When the absolute pressure type is used, a pressure gauge for measuring the atmospheric pressure is provided, the differential pressure is calculated by the difference between the pressure gauge 109 and the atmospheric pressure, and the energization amount of the heater 110 is controlled by the differential pressure. Needless to say, the occlusion should be detected in the same way as in 1.

Further, in the first embodiment, in the control unit 12, the standard deviation σ was used as a statistic representing the variation in the variation rate of the measurement value (differential pressure) per unit time calculated by the variation rate calculation section 12-2. However, it goes without saying that variance may be used and a variance calculator may be provided as one of the variance calculators instead of the standard deviation calculator.

Further, in step S502 of the first embodiment, in order to exclude an event such as a power failure or intentional chiller operation stop in the superconducting magnet 100, measurement value data of a specified value or more is excluded, but other methods are also possible. Needless to say. For example, if the superconducting magnet 100 is provided with a state monitoring device, it goes without saying that the power failure and the refrigerator stop period may be excluded by recording the state monitoring device.

Incidentally, as a specific value of the statistical calculation in the first embodiment, in the case of using a differential pressure type as the pressure gauge 109, about one month as the accumulation of the data of the pressure value for a certain time in step S502, fluctuation in step S502 The unit time of the rate calculation is 1 hour, the equilibrium value +2kPa, and the standard deviation σ is calculated in step S503 as a specified value for excluding events such as a power failure of the superconducting magnet 100 in step S502 and an intentional shutdown of the refrigerator. It is known that a value such as 15 kPa/day may be used as the threshold value in step S504 in such a case.

Further, in order to exclude an event such as a power failure or an intentional stoppage of the refrigerator in the superconducting magnet 100, a power reception signal of the magnet control device, a power reception signal of the magnet control device, an operation stop signal from the refrigerator, etc. may be used. it is conceivable that.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. However, in the second embodiment, when the control unit 12 of the superconducting magnet 200 is connected to the Internet or the telephone network and the pipe 108 of the superconducting magnet 200 is blocked, the fact is automatically transmitted to the remote serviceman 601 or the monitoring center 602. It is characterized by comprising a transmitting means for performing. This will be described below with reference to FIGS. 6 and 7.

FIG. 6 is a cross-sectional structure of the superconducting magnet 200 according to the second embodiment of the present invention. In this embodiment, the control unit 12 is connected to the Internet or the telephone network, and the Internet or the telephone network is connected to the service person 601 or the monitoring center 602 of the superconducting magnet 100.

Further, FIG. 7 is an operation flow example of the MRI apparatus using the superconducting magnet 200 and its maintenance system and maintenance method according to the second embodiment of the present invention. Since only the steps S705 and S706 are different from the flow of FIG. 4, only different steps will be described.

(Step S705)
The control unit 12 automatically sends information to the service person 601 at a remote place that the pipe 108 of the superconducting magnet 200 is blocked by means of electronic mail or the like.

(Step S706)
Upon receiving the information that the pipe 108 of the superconducting magnet 200 is blocked, the serviceman 601 is dispatched to the site where the superconducting magnet 200 is located.

According to the present embodiment, since the information is automatically transmitted to the service person 601 at a remote location, there is an advantage that it is possible to take an early countermeasure against the blockage of the pipe 108 of the superconducting magnet 200.

In the above-mentioned Example 1 and Example 2, the control unit 12 for calculating the statistic of the measurement value of the pressure gauge 109, the superconducting magnet (100, 200), when provided in the MRI apparatus using it However, the present invention is not limited to this.

For example, the pressure gauge 109 is directly connected to a remote server via the Internet or a telephone network, and the remote server is equipped with a pressure acquisition unit 12-1, a fluctuation rate calculation unit 12-2, etc., and an external server. It goes without saying that the maintenance system may be configured so as to determine that the blockage has occurred. At this time, it goes without saying that the remote server may be arranged at a place distant from the place where the MRI apparatus is arranged, for example, may be in another country.

100 superconducting magnet, 101 superconducting coil, 102 liquid helium, 103 coil container, 104 vacuum container, 105 refrigerator, 106 low temperature side helium tank, 107 coil container sound side space, 108 piping, 109 pressure gauge, 110 heater, 111 control line , 112 piping low temperature side, 12 control section

Claims (6)

A superconducting coil for generating a static magnetic field in a desired space, a coil container that accommodates the superconducting coil together with liquid helium as a refrigerant, a vacuum container that surrounds the coil container, and is held in a vacuum, and A pipe provided in the upper part of the coil container, a heater for vaporizing and adjusting the liquid helium and its control so as to keep the pressure in the coil container so that the pressure in the coil container does not become a negative pressure. A wire, and a superconducting magnet composed of a pressure gauge provided on the room temperature side of the pipe,
A determination unit that determines that blockage has occurred on the coil container side of the pipe based on the variation in the fluctuation rate per unit time of the measurement value measured for a predetermined time by the pressure gauge,
A pressure acquisition unit that is connected to the pressure gauge and acquires a pressure value measured by the pressure gauge, and is connected to the pressure acquisition unit and has a desired time of measurement value data acquired by the pressure acquisition unit, in units. A volatility calculation unit that calculates the volatility of the measured value per time, and a standard deviation calculation unit that is connected to the volatility calculation unit and that calculates the standard deviation of the volatility calculated by the volatility calculation unit,
The determination unit, a magnetic resonance imaging apparatus characterized by determining whether the obstruction has occurred by comparing the value of the standard deviation calculated by the standard deviation calculating unit with a threshold value. The pressure gauge measures pressure by a differential pressure formula with atmospheric pressure, and the determination unit determines that the blockage occurs based on the variation being larger than a predetermined threshold value. The magnetic resonance imaging apparatus according to claim 1 . The magnetic resonance imaging apparatus according to claim 1, wherein the variation rate calculation unit excludes a variation rate equal to or more than a predetermined specified value when calculating the variation rate from the measurement value data. The magnetic resonance imaging apparatus according to claim 1, wherein the variation is a standard deviation or a variance of the variation rate. 2. The magnetic resonance imaging apparatus according to claim 1, further comprising a transmission unit that is connected to the discrimination unit via the Internet or a telephone network and transmits the result of the discrimination to a remote serviceman. The pressure gauge is connected to a remote server via the Internet or a telephone network, the remote server is connected to the pressure acquisition unit that acquires the pressure value measured by the pressure gauge, and is connected to the pressure acquisition unit, and is acquired by the pressure acquisition unit. A fluctuation rate calculation unit that calculates a fluctuation rate of measured values per unit time from measured value data measured within a desired time, and a fluctuation rate calculated by the fluctuation rate calculation unit connected to the fluctuation rate calculation unit 2. A variation calculation unit that calculates a difference, and a determination unit that determines that a blockage has occurred on the coil container side of the pipe based on the variation calculated by the variation calculation unit. Maintenance system using the magnetic resonance imaging device.

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