JP2011045626A - X-ray ct apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus capable of predicting the residual life of an X-ray tube considering mechanical degradation caused by centrifugal force generated by the rotation of a gantry. <P>SOLUTION: The X-ray CT apparatus includes a means for computing the residual life of a rotating mechanism 150 of a target 130 based on the number of rotation of the rotating gantry. For example, the products of rotating speed ωi, the number of rotation r(ωi) of the gantry rotated at the rotating speed ωi, and a coefficient βBR depending on the rotating speed ωi, are computed every rotating speed ωi of the gantry, and the sum of these products is obtained as the use consumption BR of the rotating mechanism 150. The use consumption BR is subtracted from the predicted life (average life) BR0 of the rotating mechanism 150 to compute the residual life PBR. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray CT (Computed Tomography) apparatus, and more particularly to management of the life of an X-ray tube.

  An X-ray CT apparatus usually includes an X-ray tube for exposing X-rays. This X-ray tube is a consumable item with a long life, and is replaced periodically or as necessary.

  X-ray tubes are generally very expensive. Therefore, from an economic point of view, it is desirable to use the X-ray tube until its lifetime is completely exhausted and then replace it.

  However, if the X-ray tube continues to be used until the end of its life, the X-ray tube breaks during the operation of the X-ray CT apparatus, and imaging is interrupted. Especially in the medical field, patient safety And adversely affect hospital management.

  Therefore, it is most desirable to predict the remaining life of the X-ray tube from the usage conditions and so on, so that it can be replaced in advance immediately before the end of the life.

  Conventionally, in order to realize this, various proposals have been made on techniques for managing the replacement time by predicting the remaining life of the X-ray tube. For example, Patent Document 1 discloses that the number of X-ray exposures is counted and the replacement time of the X-ray tube is obtained and managed based on the number of exposures. Further, for example, Patent Document 2 discloses storing X-ray exposure dose and determining and managing the replacement time of the X-ray tube based on the integrated value of the exposure dose. Further, for example, in Patent Document 3, the remaining lifetime of an emitter is predicted based on the value of a current flowing through an emitter (also referred to as a filament) of an X-ray tube and an X-ray exposure time, and X-ray It is disclosed to seek and manage the time for tube replacement.

JP-A 63-147441 JP 05-062790 A JP 2006-1000017 A

  By the way, the applicant of the present invention states that, depending on the use conditions of the X-ray CT apparatus, the remaining life of the X-ray tube may be dominated by mechanical deterioration due to centrifugal force generated by rotation of the gantry. I have confirmed.

  However, in the conventional X-ray tube remaining life prediction, although deterioration due to the output load of the X-ray tube is considered, mechanical deterioration due to centrifugal force is not considered. For this reason, depending on the use conditions of the X-ray CT apparatus, the remaining life of the X-ray tube cannot be accurately predicted, and the replacement time may not be accurately managed.

  In view of the above circumstances, an object of the present invention is to provide an X-ray CT apparatus capable of predicting the remaining life of an X-ray tube in consideration of mechanical deterioration due to centrifugal force generated by rotation of a gantry.

  In a first aspect, the present invention is an X-ray CT apparatus comprising a gantry having a target that generates X-rays by collision of electrons and an X-ray tube that includes a rotation mechanism of the target. An X-ray CT apparatus provided with a rotation mechanism remaining life calculating means for calculating the remaining life of the rotation mechanism based on the number of rotations of the rotation mechanism is provided.

  In a second aspect, the present invention provides the first rotating mechanism remaining life calculating means for calculating the remaining life of the rotating mechanism based on a rotation speed of the gantry and a rotation speed at the rotation speed. An X-ray CT apparatus is provided.

  In a third aspect, the present invention provides the rotating mechanism remaining life calculating means based on a sum of products of the rotational speed at each rotational speed of the gantry, the rotational speed at the rotational speed, and a predetermined coefficient. An X-ray CT apparatus according to the second aspect for calculating the remaining life of the rotating mechanism is provided.

  In a fourth aspect, the present invention provides the X-ray CT apparatus according to the third aspect, wherein the predetermined coefficient is a value proportional to the square of the rotational speed.

  In a fifth aspect, the present invention is directed to the X-ray tube, wherein the X-ray tube has a filament that emits electrons that collide with the target, and the current value of the X-ray tube or the filament and the X-ray at the current value Provided is an X-ray CT apparatus according to any one of the first to fourth aspects, further comprising a filament remaining life calculating means for calculating a remaining life of the filament based on an exposure time. .

  In a sixth aspect, the present invention provides the first to fifth aspects according to the fifth aspect, further comprising first informing means for informing when the calculated remaining life is less than a predetermined value. An X-ray CT apparatus according to any one aspect is provided.

  In a seventh aspect, the present invention relates to the sixth aspect to the sixth aspect, further comprising an occurrence frequency calculating means for detecting an in-tube discharge of the X-ray tube and calculating an occurrence frequency of the in-tube discharge. An X-ray CT apparatus according to any one aspect is provided.

  In an eighth aspect, the present invention provides the X-ray CT apparatus according to the seventh aspect, further comprising second informing means for informing when the calculated occurrence frequency exceeds a predetermined value. provide.

  In a ninth aspect, the present invention provides the frequency component amount calculating means for detecting the vibration of the X-ray tube and calculating a component amount of a specific frequency included in the vibration. An X-ray CT apparatus according to eight aspects is provided.

  In a tenth aspect, the present invention provides the X-ray CT apparatus according to the ninth aspect, further comprising third informing means for informing when the calculated component amount exceeds a predetermined value. provide.

  According to the X-ray CT apparatus of the present invention, the rotation mechanism remaining life calculating means for calculating the remaining life of the target rotation mechanism is provided based on the number of rotations of the gantry. It is possible to predict the remaining life of the X-ray tube in consideration of mechanical degradation due to force.

It is a figure which shows schematically the structure of the X-ray CT apparatus by this embodiment. It is a figure which shows the structure of the X-ray tube with which the X-ray CT apparatus by this embodiment is provided. It is a flowchart (flow chart) which shows the flow of the process which concerns on the X-ray CT apparatus by this embodiment. It is a figure which shows an example of the relationship between the usage-amount of a bearing mechanism, and the usage time of a X-ray CT apparatus. An example of the relationship between the consumed amount of filament and the usage time of the X-ray CT apparatus is shown. It is a figure which shows an example of the vibration waveform of an X-ray tube. It is a figure which shows an example of the component amount of each frequency of the vibration waveform of an X-ray tube. It is a figure which shows an example of the relationship between the component amount of the specific frequency in the vibration waveform of an X-ray tube, and the usage time of an X-ray CT apparatus. It is a figure which shows an example of the time change of the set tube voltage and the measured tube voltage. It is a figure which shows an example of the relationship between the generation frequency of the in-tube discharge of an X-ray tube, and the usage time of an X-ray CT apparatus.

  Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited thereby.

FIG. 1 is a diagram schematically showing the configuration of the X-ray CT apparatus according to the present embodiment.
The X-ray CT apparatus mounts an X-ray tube 1 and an X-ray detector 2 across a cavity, and places a gantry 3 configured to be rotatable around the cavity and a subject. An imaging table (table) 4 is provided that is transported to the cavity of the gantry 3. The X-ray detector 2 is connected to a data collection device 5 for collecting data from the X-ray detector 2. The rotating part and the support part of the gantry 3 are electrically connected via a slip ring.

  In addition, the X-ray CT apparatus has a central processing unit 6 that performs image reconstruction based on data collected by the data collecting apparatus 5 and controls the entire apparatus, and an operator is required for a scan plan. An input device 7 for inputting various information, a storage device 8 for storing a program and various data, and a display device 9 for displaying an image obtained by image reconstruction and various information. ing.

  Connected to the central processing unit 6 is a table / gantry control device (hereinafter referred to as TGP) 10 for controlling the drive of the gantry 3 and the imaging table 4. A tube voltage supplied to the X-ray tube 1 is connected to the TGP 10. An X-ray controller 11 for controlling the tube current, X-ray exposure timing (timing), and the like is connected.

  Furthermore, the X-ray CT apparatus is connected via a network to a maintenance center server (server) 16 installed in a maintenance center (center) that performs services such as maintenance and inspection of the X-ray CT apparatus. ing. The X-ray CT apparatus sends data necessary for maintenance and inspection, such as information related to the life of the X-ray tube 1, to the maintenance center server 16.

  Note that here, the direction in which the subject is conveyed by the imaging table 4 (body axis direction) is the z direction, the vertical direction is the y direction, and the horizontal direction perpendicular to the z direction and the y direction is the x direction. Therefore, the gantry 3 rotates around an axis substantially parallel to the z direction.

  The TGP 10 controls the motor 12 and rotationally drives the gantry 3 via a drive mechanism 13 connected to the motor 12. An encoder 14 is connected to the drive mechanism 13 and its output signal is sent to the TGP 10.

  The TGP 10 controls the rotational speed ω of the gantry 3 based on the output signal of the encoder 14 while executing the scan.

  Further, the TGP 10 performs the rotation speed ω of the gantry 3 and the rotation speed r (ω), which is the number of times the gantry 3 has rotated at the rotation speed ω, based on the output signal of the encoder 14 during the scan. And the measurement data is stored in the storage device 8 via the central processing unit 6. This measurement data is used to calculate the remaining life of a bearing mechanism (target rotation mechanism) described later included in the X-ray tube 1.

  A vibration sensor (sensor) 15 is attached to the X-ray tube 1, and an output signal thereof is sent to the TGP 10. The TGP 10 measures the vibration waveform W of the X-ray tube 1 based on the output signal of the vibration sensor 15 and stores the measurement data in the storage device 8 via the central processing unit 6. This measurement data is used to calculate the component amount of the specific frequency in the vibration of the X-ray tube 1, and the component amount of the specific frequency is used to detect the end of life of the X-ray tube 1. When the X-ray tube 1 reaches the end of its life due to mechanical deterioration, the vibration of a specific frequency tends to increase rapidly. Therefore, the end-of-life state of the X-ray tube 1 can be detected by monitoring the component amount of the specific frequency in the vibration of the X-ray tube 1.

  On the other hand, while the X-ray controller 11 is executing the scan, the tube current γ of the X-ray tube 1 in the X-ray exposure operation and the time during which the X-ray tube 1 has irradiated the X-ray with the tube current γ. A certain X-ray exposure time T (γ) is measured, and the measurement data is stored in the storage device 8 via the TGP 10 and the central processing unit 6. This measurement data is used for calculating the remaining life of a filament, which will be described later, included in the X-ray tube 1.

  Further, the X-ray controller 11 measures the tube voltage in the X-ray exposure operation while executing the scan, and sets the measurement data representing the time change of the measured tube voltage Vm in the scan plan. The data is stored in the storage device 8 via the central processing unit 6 in association with the tube voltage Vs of the X-ray tube 1. This measurement data is used for detection of the in-tube discharge of the X-ray tube 1 and calculation of the occurrence frequency, and the occurrence frequency of the in-tube discharge is used for detection of the end of life of the X-ray tube 1. The in-tube discharge is a discharge that is generated in a single path along a path other than between the electrodes. When the X-ray tube 1 reaches the end of its life due to a decrease in the degree of vacuum in the tube or the incorporation of impurities into the tube, the frequency of occurrence of discharge in the tube tends to increase rapidly. Therefore, the end-of-life state of the X-ray tube 1 can be detected by monitoring the frequency of occurrence of in-tube discharge.

  FIG. 2 is a diagram showing the configuration of the X-ray tube. This figure is a cross-sectional view of the X-ray tube 1 as viewed from a direction orthogonal to the z direction. As shown in FIG. 2, the X-ray tube 1 includes a cathode 120, an anode (target) 130, and a rotor 140 integrated with the anode 130 in a vacuum vessel 110. And a bearing mechanism (target rotating mechanism) 150 that supports a shaft 142 of the rotor 140.

  The vacuum container 110 is made of an X-ray transmissive material such as glass and has a vacuum inside. Within the vacuum vessel 110, the cathode 120 and the anode 130 face each other. The cathode 120 includes a filament 121 that emits electrons. A high voltage as a tube voltage is applied between the cathode 120 and the anode 130. The electrons emitted from the filament 121 are accelerated by the applied high voltage and collide with the anode 130 to generate X-rays. This electron flow becomes a tube current.

  The anode 130 is generally disc-shaped. The anode 130 is integrated by a substantially cylindrical rotor 140 and a shaft 142. The rotor 140 is, for example, a rotor of an induction motor, and is excited by a stator coil (not shown) outside the vacuum vessel 100 and rotates integrally with the anode 130 around the shaft 142. The shaft 142 is supported in a cantilever manner by the bearing mechanism 150 inside the rotor 140.

  The bearing mechanism 150 has a generally cylindrical case 151, and the case 151 has a bottom 152.

  Inside the case 151, two rolling bearings 156 and 157 are provided at a predetermined interval, and the shaft 142 is rotatably supported by these rolling bearings 156 and 157. For example, ball bearings or the like are used as the rolling bearings 156 and 157. By using a rolling bearing, the mechanical strength of the shaft support can be increased.

  The central processing unit 6 is an example of a rotating mechanism remaining life calculating unit, a filament remaining life calculating unit, an occurrence frequency calculating unit, and a frequency component amount calculating unit in the present invention. The central processing unit 6 and the display device 9 are examples of first to third notification units in the present invention.

  From now on, the flow of the process which concerns on the X-ray CT apparatus by this embodiment is demonstrated.

  FIG. 3 is a flowchart showing a flow of processing according to the X-ray CT apparatus according to the present embodiment.

  In step S1, a scan is executed according to the input scan plan. During the execution of scanning, the TGP 10 and the X-ray controller 11 operate as follows.

  The TGP 10 controls the gantry 3 to rotate at the rotation speed ωs set in the scan plan based on the output signal of the encoder 14. The TGP 10 measures the rotational speed of the gantry 3 based on the output signal of the encoder 14, and measures the rotational speed r (ωm), which is the number of times the gantry 3 rotates at the measured rotational speed ωm. The measurement data is stored in the storage device 8. The rotational speed ωm may be estimated from a control signal for controlling the rotation of the gantry 3, or the rotational speed ωs set in the scan plan may be used as it is as the rotational speed ωm.

  The TGP 10 further measures the vibration waveform W of the X-ray tube 1 based on the output signal of the vibration sensor 15 and stores the measurement data in the storage device 8.

  On the other hand, the X-ray controller 11 controls the X-ray exposure by the X-ray tube 1 to be executed at the tube voltage Vs, tube current γs, and exposure timing set in the scan plan. Further, the X-ray controller 11 measures the tube current of the X-ray tube 1 and measures the X-ray exposure time T (γm) which is the time of X-ray exposure with the measured tube current γm. The measurement data is stored in the storage device 8. The tube current γm may be obtained from a current sensor or the like, or may be estimated from a control signal for controlling the tube current of the X-ray tube 1. Alternatively, the tube current γs set in the scan plan may be used as it is as the tube current γm. Further, the X-ray exposure time T (γm) may be estimated from a control signal for controlling the exposure timing of the X-ray tube 1, or the X-ray exposure time Ts set in the scan plan is used. The X-ray exposure time T (γm) may be used as it is.

  The X-ray controller 11 further measures the tube voltage in the X-ray exposure operation, and calculates the tube voltage Vs of the X-ray tube 1 set in the scan plan and the measured tube voltage Vm of the X-ray tube 1. Measurement data representing a change over time is stored in the storage device 8.

  Steps S <b> 2 to S <b> 17 are processes related to calculation of the remaining life of the X-ray tube 1 and detection of the end of life.

  Specifically, steps S <b> 2 to S <b> 5 are processing relating to calculation of the remaining life of the bearing mechanism 150 and detection of the end of life based on the remaining life. Steps S <b> 6 to S <b> 9 are processes related to calculation of the remaining life of the filament 121 and detection of the end of life based on the remaining life. Steps S <b> 10 to S <b> 13 are processes relating to the end of life detection based on the vibration waveform of the X-ray tube 1. Steps S <b> 14 to S <b> 17 are processes related to the end of life detection based on the in-tube discharge of the X-ray tube 1. These steps may be executed in any order as long as the time-series order indicated by the arrows in the flowchart of FIG. 3 is observed, and may be executed in parallel. Here, it is assumed that each step is executed in the order of the numbers.

  First, processing (S2 to S5) relating to calculation of the remaining life of the bearing mechanism 150 and detection of the end of life based on the remaining life will be described.

  In step S <b> 2, the central processing unit 6 reads all data including the rotational speed ωm and the rotational speed r (ωm) of the gantry 3 for each rotational speed from the storage device 8. In step S3, the remaining life PBR of the bearing mechanism 150 is calculated based on the read data. The remaining life PBR of the bearing mechanism 150 is calculated according to the following formula, for example.

  Here, BR0 is a predicted life (average life) of the bearing mechanism 150, BR is a consumption amount of the bearing mechanism 150, ωi is each rotational speed, r (ωi) is a rotational speed at which the gantry 3 is rotated at the rotational speed ωi, βBR Is a coefficient depending on the rotational speed ωi, and kBR is a predetermined constant.

  The consumption consumption BR of the bearing mechanism 150, particularly the consumption consumption of the rolling bearings 156 and 157 such as bearings, is subject to the centrifugal force of the target generated by the rotation of the gantry 3 in addition to the wear deterioration due to the normal rotation of the target. It is thought that it becomes larger due to deterioration due to. The deterioration due to the centrifugal force depends on the magnitude of the rotational speed ωi of the gantry 3 and the rotational speed r (ωi) at which the gantry 3 is rotated at the rotational speed ωi, and is particularly severe as the rotational speed ωi increases. It is thought to increase.

  The above mathematical formula reflects such characteristics relating to the deterioration of the bearing mechanism 150. The coefficient βBR is obtained empirically and is a value proportional to the square of the rotational speed ωi here. However, depending on the structure and type of the X-ray tube 1, the coefficient βBR may have a value that is proportional to the rotational speed ωi or a value that is proportional to the cube of the rotational speed ωi that matches the actual remaining life. .

  When the remaining life PBR is calculated, the central processing unit 6 displays the remaining life PBR on the screen of the display device 9. In addition to the remaining life PBR, (use consumption BR / predicted life BR0) × 100 may be further displayed as a usage rate (%).

  FIG. 4 is a diagram showing an example of the relationship between the consumption amount of the bearing mechanism and the usage time of the X-ray CT apparatus.

  The consumption consumption BR of the bearing mechanism 150 gradually increases with the use time T as shown in FIG. When the consumption amount BR exceeds the predetermined consumption amount BRth and the remaining life PBR falls below a predetermined value, it can be considered that the required replacement level has been reached.

  Therefore, in step S4, the central processing unit 6 determines whether or not the remaining life PBR <predetermined value, and if this condition is satisfied, in step S5, “replacement recommendation” of the X-ray tube 1 is displayed on the screen of the display device 9. To display.

  Next, processing (S6 to S9) relating to calculation of the remaining life of the filament 121 and detection of the end of life based on the remaining life will be described.

  In step S6, the central processing unit 6 reads all the tube current γm and the X-ray exposure time T (γm) of the X-ray tube 1 from the storage device 8 for each tube current. In step S7, the remaining life PFL of the filament 121 is calculated based on the read data. The remaining life PFL of the filament 121 is calculated according to the following formula, for example.

  Here, FL0 is the predicted life (average life) of the filament 121, FL is the consumed consumption amount of the filament 121, γj is each tube current, T (γj) is the X-ray exposure time at the tube current γj, βFL is a coefficient, kFL is a predetermined constant.

  The consumption consumption FL of the filament 121 is considered to increase due to deterioration due to the output load of the X-ray tube 1. The deterioration due to the output load depends on the magnitude of the tube current γ of the X-ray tube 1 and the X-ray exposure time T (γ) at the tube current γ, and is particularly severe as the tube current γ increases. Is thought to increase.

  The above mathematical formula reflects such characteristics relating to the deterioration of the filament 121. The coefficient βFL is obtained empirically, and is a value proportional to the tube current γj here. However, depending on the structure and type of the X-ray tube 1, the coefficient βFL may be a value that is proportional to the square of the tube current γj or a simple constant that matches the actual remaining life.

  When the remaining life PFL is calculated, the central processing unit 6 displays the remaining life PFL on the screen of the display device 9. In addition to the remaining life PFL, (usage consumption FL / predicted life FL0) × 100 may be further displayed as a usage rate (%).

  FIG. 5 shows an example of the relationship between the consumed amount of filament and the usage time of the X-ray CT apparatus.

  The used consumption amount FL of the filament 121 gradually increases with the use time T of the X-ray CT apparatus, for example, as shown in FIG. Then, it can be considered that the required replacement level has been reached when the usage consumption amount FL exceeds the predetermined usage consumption amount FLth and the remaining life PFL falls below a predetermined value.

  Therefore, in step S8, the central processing unit 6 determines whether or not the remaining life PFL <predetermined value. When this condition is satisfied, in step S9, “Replacement recommendation” of the X-ray tube 1 is displayed on the screen of the display device 9. To display.

  Next, processing (S10 to S13) relating to detection at the end of life based on the vibration waveform of the X-ray tube will be described.

  In step S <b> 10, the central processing unit 6 reads the measurement data of the vibration waveform W of the X-ray tube 1 from the storage device 8 for the latest predetermined time.

  FIG. 6 is a diagram showing an example of a vibration waveform of the X-ray tube. The vibration waveform W shown in FIG. 6 represents the vibration waveform of the X-ray tube 1 for a predetermined time Δt1, with the horizontal axis representing time t and the vertical axis representing the peak value h. As shown in FIG. 6, the vibration waveform W forms a complex waveform by overlapping a plurality of frequency components.

  In step S11, as shown in FIG. 7, the vibration waveform W is subjected to Fourier transform (FFT) to extract its component for each frequency, and the component amount Afa of the specific frequency fa is obtained.

  FIG. 8 is a diagram illustrating an example of the relationship between the component amount of the specific frequency in the vibration waveform of the X-ray tube and the usage time of the X-ray CT apparatus.

  The component amount Afa of the specific frequency fa in the vibration waveform W of the X-ray tube 1 hardly changes when the use time T of the X-ray CT apparatus is small, for example, as shown in FIG. However, when the use time T increases and mechanical deterioration of the X-ray tube 1 progresses, and the X-ray tube 1 approaches the end of its life, it rapidly increases. Therefore, the end of life of the X-ray tube 1 can be detected by confirming that the component amount Afa of the specific frequency fa exceeds the predetermined value Ath.

  Therefore, in step S12, the central processing unit 6 determines whether or not the component amount Afa of the specific frequency fa exceeds a predetermined value Ath. When this condition is satisfied, it is considered that the X-ray tube 1 has reached the end of its life, and “replacement recommendation” of the X-ray tube 1 is displayed on the screen of the display device 9 in step S13.

  Next, processing (S14 to S17) related to detection at the end of life based on in-tube discharge of the X-ray tube will be described.

  In step S <b> 14, the central processing unit 6 obtains the latest measurement data from the storage device 8 representing the time variation of the set tube voltage Vs and the measured tube voltage Vm in the X-ray exposure operation of the X-ray tube 1. Are read for a predetermined time.

  FIG. 9 is a diagram illustrating an example of a time change of the set tube voltage and the measured tube voltage. The time change of the tube voltages Vs and Vm shown in FIG. 9 represents the time change of the tube voltage for a predetermined time Δt2 with the time t on the horizontal axis and the tube voltage value V on the vertical axis.

  In step S15, the central processing unit 6 determines when the tube voltage Vm drops below the tube voltage Vs by a predetermined voltage ΔV in the time variation of the set tube voltage Vs and the measured Vm. This is detected as the time when the in-tube discharge sp is generated. For example, in the example of FIG. 9, the time indicated by sp1 to sp3 is the time when the in-tube discharge occurs. Then, a value obtained by dividing the number of occurrences Csp of the in-tube discharge within the predetermined time Δt2 by the time Δt2 is calculated as the occurrence frequency R.

  FIG. 10 is a diagram showing an example of the relationship between the frequency of occurrence of in-tube discharge of the X-ray tube and the usage time of the X-ray CT apparatus.

  The occurrence frequency R of the in-tube discharge of the X-ray tube 1 hardly changes when the use time T of the X-ray CT apparatus is small, for example, as shown in FIG. However, when the use time T increases and the degree of vacuum of the X-ray tube 1 decreases or impurities are mixed into the tube, the X-ray tube 1 rapidly increases as it approaches the end of its life. Therefore, the end of life of the X-ray tube 1 can be detected by confirming that the occurrence frequency R of the in-tube discharge exceeds the predetermined value Rth.

  Therefore, in step S16, the central processing unit 6 determines whether the occurrence frequency R of the in-tube discharge exceeds a predetermined value Rth. When this condition is satisfied, the X-ray tube 1 is considered to have reached the end of its life, and “Replacement Recommendation” for the X-ray tube 1 is displayed on the screen of the display device 9 in step S17.

  In step S18, the central processing unit 6 transmits various information related to the remaining life of the X-ray tube 1 obtained in steps S2 to S17 to the maintenance center server 16. For example, the remaining life PBR of the bearing mechanism 150, the remaining life PFL of the filament 121, the component amount Afa of the specific frequency in the vibration of the X-ray tube 1, the occurrence frequency R of the in-tube discharge of the X-ray tube 1, the X-ray tube replacement recommendation display Send information such as presence / absence. Thereby, the maintenance center can perform the life management of the X-ray tube in the customer's X-ray CT apparatus quickly and accurately, and can perform a quick and accurate maintenance service. This information may be transmitted every time a scan is performed, or may be periodically performed over a longer span.

  The life management of the X-ray tube 1 may be performed not by the central processing unit 6 but by the maintenance center server 16. For example, the maintenance center server 16 analyzes various information related to the remaining life of the X-ray tube 1 transmitted from the X-ray CT apparatus, and “replacement recommendation” is displayed on the screen of the display device 9 according to the result. May be transmitted to the X-ray CT apparatus or may be scheduled for dispatching maintenance service personnel to the site.

  In step S19, the next scan is executed according to the input scan plan (which may be a new scan plan or an already input scan plan).

  The X-ray CT apparatus performs life management of the X-ray tube 1 by repeating such steps.

  As described above, according to the present embodiment, since the remaining life of the bearing mechanism 150 is calculated based on the number of rotations of the gantry 3, the mechanical deterioration due to the centrifugal force generated by the rotation of the gantry 3 is taken into consideration. The remaining life of the X-ray tube 1 can be predicted.

  In the present embodiment, since the remaining life is calculated in consideration of not only the rotation speed of the gantry 3 but also the rotation speed of the gantry 3, it is possible to calculate a more accurate remaining life.

  In the present embodiment, not only the remaining life of the bearing mechanism 150 but also the remaining life of the filament 121 is calculated. Therefore, it is possible to cope with a case where it is unclear whether the element that governs the remaining life of the X-ray tube 1 is the deterioration of the bearing mechanism 150 or the deterioration of the filament 121 or changes depending on the use conditions.

  Then, by displaying the remaining life of the bearing mechanism 150 and the filament 121 calculated in this way, the operator can monitor the remaining life of the X-ray tube 1 and systematically operate the X-ray CT apparatus. be able to.

  Further, in the present embodiment, an increase in the component amount of the specific frequency in the vibration of the X-ray tube 1 or an increase in the frequency of occurrence of in-tube discharge of the X-ray tube 1 is detected, and the end of life of the X-ray tube 1 is detected. Since it is detected, it can be notified more reliably that the replacement time of the X-ray tube 1 has come. For example, even if the calculated remaining life of the bearing mechanism 150 or filament 121 deviates significantly from the actual remaining life for some reason, the end-of-life state of the X-ray tube 1 is detected and a warning is given. It is possible to back up the X-ray tube 1 so that the X-ray tube 1 is not damaged suddenly.

  In the present embodiment, a method of displaying on the screen of the display device 9 is used as a method for recommending replacement of the X-ray tube 1, but other methods such as voice, alarm sound, lamp ( lamp) or the like may be used.

  In the present embodiment, the remaining life of the bearing mechanism 150 is calculated, the remaining life of the filament 121 is calculated, the end of life is detected based on the vibration of the X-ray tube 1, and the end of life is determined based on the in-tube discharge of the X-ray tube 1. Detection is in progress. However, there is a modification in which at least one of calculation of the remaining life of the filament 121, detection of the end of life based on the vibration of the X-ray tube 1 and detection of the end of life based on the in-tube discharge of the X-ray tube 1 is not performed. Conceivable. In particular, when it is known that the factor that governs the remaining life of the X-ray tube 1 is deterioration of the bearing mechanism 150, only the remaining life of the bearing mechanism 150 may be calculated.

  In the present embodiment, the remaining life of the filament 121 is calculated based on the tube current γm and the X-ray exposure time T (γm). However, the remaining life of the filament 121 is calculated by, for example, measuring the filament current ηm flowing through the filament 121 and the X-ray exposure time T (ηm) in addition to or instead of these pieces of information. You may carry out based on these. Further, for example, the calculation may be performed in consideration of the tube voltage Vm.

  In the present embodiment, the occurrence of in-tube discharge is detected because the measured tube voltage Vm is significantly reduced from the set tube voltage Vs. However, the detection may be performed by other methods, for example, by detecting a significant decrease in the output level (level) of the reference channel or the like in the X-ray detector 2.

1 X-ray tube 2 X-ray detector 3 Gantry 4 Imaging table 5 Data collection device (DAS)
6 Central processing unit 7 Input device 8 Display device 9 Storage device 10 Table gantry control device (TGP)
11 X-ray controller 12 Motor 13 Drive mechanism 14 Encoder 15 Vibration sensor 16 Maintenance center server 110 Vacuum vessel 120 Cathode 121 Filament 130 Anode (target)
140 Rotor 142 Shaft 150 Bearing mechanism (target rotation mechanism)
151 Case 152 Bottom 156, 157 Rolling bearing

Claims (10)

An X-ray CT apparatus having a gantry having a target that generates X-rays by collision of electrons and an X-ray tube including a rotation mechanism of the target,
An X-ray CT apparatus comprising a rotation mechanism remaining life calculating means for calculating a remaining life of the rotation mechanism based on the number of rotations of the gantry.   The X-ray CT apparatus according to claim 1, wherein the rotation mechanism remaining life calculation unit calculates a remaining life of the rotation mechanism based on a rotation speed of the gantry and a rotation speed at the rotation speed.   The rotation mechanism remaining life calculating means calculates the remaining life of the rotation mechanism based on a sum of products of the rotation speed at each rotation speed of the gantry, a rotation speed at the rotation speed, and a predetermined coefficient. Item 3. The X-ray CT apparatus according to Item 2.   The X-ray CT apparatus according to claim 3, wherein the predetermined coefficient is a value proportional to a square of the rotation speed. The X-ray tube has a filament that emits electrons that collide with the target,
The filament remaining life calculating means for calculating the remaining life of the filament based on the current value of the X-ray tube or the filament and the X-ray exposure time at the current value. 5. The X-ray CT apparatus according to any one of 4 above.   The X-ray CT apparatus according to any one of claims 1 to 5, further comprising a first notifying unit that notifies that when the calculated remaining life falls below a predetermined value.   The X-ray CT apparatus according to any one of claims 1 to 6, further comprising an occurrence frequency calculating unit that detects an in-tube discharge of the X-ray tube and calculates an occurrence frequency of the in-tube discharge.   The X-ray CT apparatus according to claim 7, further comprising second notification means for notifying when the calculated occurrence frequency exceeds a predetermined value.   9. The X-ray CT apparatus according to claim 1, further comprising a frequency component amount calculation unit that detects vibration of the X-ray tube and calculates a component amount of a specific frequency included in the vibration.   The X-ray CT apparatus according to claim 9, further comprising third informing means for informing when the calculated component amount exceeds a predetermined value.

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