JP5314692B2 - X-ray CT system - Google Patents

Description

  The present invention relates to an X-ray CT apparatus, and more particularly to a technique suitable for an X-ray CT apparatus capable of high-speed scanning.

  The X-ray CT apparatus irradiates the subject with a fan-shaped, conical or pyramidal X-ray beam from various projection angles from the X-ray tube, and the X-ray transmitted through the subject is opposed to the X-ray tube. The detected X-ray detector is used for detection, and the detected data is subjected to reconstruction calculation to obtain a tomographic image of the subject.

  With this X-ray CT system, features such as “a wide range of scanning is possible in a short time” and “continuous data in the body axis direction can be obtained, which makes it possible to generate a three-dimensional image”. A helical scan method called helical scan or spiral scan is used. In this spiral scan, the X-ray tube and X-ray detector are rotated while rotating the scanner rotating part while radiating X-rays from the X-ray tube, and the table on which the subject is placed is moved in the body axis direction. Thus, the subject is scanned in a spiral shape.

  In this case, in order to perform a rotation scan, power transmission means for continuously transmitting power to the X-ray tube mounted on the scanner rotation unit, and control signals and X-ray detection of the system controller that controls the entire CT system As signal transmission means for exchanging signals such as data detected by the scanner between the scanner stationary part and the scanner rotation part, power transmission means and signal transmission means comprising a slip ring and a brush are used.

  However, such power transmission means and signal transmission means using the slip ring and the brush are means by mechanical sliding contact between the slip ring and the brush, and thus have the following problems. That is, in power transmission, when a large current flows between the slip ring and the brush, wear or corrosion occurs at the contact portion, and power transmission becomes unstable.

  On the other hand, in signal transmission, contact failure occurs due to wear or the like due to contact between the slip ring and the brush, resulting in loss of transmission data.

  For this reason, it is necessary to periodically perform maintenance and inspection work such as polishing of the slip ring and replacement of the brush.

  Therefore, as a method of coping with such a problem, a power transmission means using electromagnetic induction is provided between the scanner stationary part and the scanner rotating part, and the rotating part that scans power from the scanner stationary part side in a non-contact manner. Patent Document 1 discloses what transmits power to the side. In addition, as a means for transmitting signals and X-ray detection data in a non-contact manner between the scanner stationary part and the scanner rotating part, a signal transmission means using optical coupling combining a light emitting element and a light receiving element is used. It is disclosed in Patent Document 2 and Patent Document 3.

Japanese Patent No. 4008010 JP-A-2-239734 Japanese Patent Laid-Open No. 5-253217

  However, Patent Documents 1 to 3 only disclose the power transmission means and the signal transmission means between the scanner stationary part and the scanner rotating part. Therefore, in order to realize an X-ray CT system that eliminates the need for maintenance and inspection work of slip rings and brushes required by conventional devices by transmitting power and signals in a non-contact manner between the scanner stationary part and the scanner rotating part. Needs further ingenuity.

  In addition, in the X-ray CT apparatus, as with other modalities, there is a high demand for application to image diagnosis of a moving organ, and a high-speed scan is required.

  However, if the power transmission means and the signal transmission means are made contactless in order to achieve high scanning speed, a signal transmission time delay occurs due to the characteristics of the contactless signal transmission means, and the X-ray exposure timing delay, There is a concern about adverse effects on feedback control of a DC high voltage (hereinafter referred to as tube voltage) applied between the anode and cathode of the X-ray tube.

  That is, as an example, when the signal transmission means using optical coupling disclosed in Patent Document 2 is used for transmission of the tube voltage control signal, conversion from an electric signal to an optical signal, conversion from an optical signal to an electric signal There is also a time delay for. In particular, if the system controller is placed in the scan stationary part and the tube voltage control device is placed in the scan rotating part, the signal related to tube voltage control will reciprocate through the optical coupling, and the total delay time will exceed 100 μs. Is also envisaged.

  When the sum of the time delay of the PID (proportional integral derivative) control system and the time delay of tube voltage control signal transmission in the tube voltage feedback control system exceeds 50 μs, the inverter circuit Since the operation cycle is 50 μs, feedback control is performed with a delay of one cycle, making it difficult to stably control the tube voltage. In order to enable stable feedback control of the tube voltage even when the sum of the time delay of the PID control system and the time delay of the tube voltage control signal transmission exceeds 50 μs, the operating frequency of the inverter circuit is set to be higher than 20 kHz. You can lower it, but doing so will increase the ripple of the tube voltage. Therefore, the image quality of the CT image is degraded.

  The present invention has been made in view of the above-described problem, and is an X-ray in which transmission of power supplied to an X-ray tube and transmission of signals to be exchanged between a stationary part of a scanner and a scanner rotation part are made contactless. The purpose is to provide a CT device.

  In order to achieve the above object, the present invention provides a scanner stationary unit, a scanner rotating unit, a DC power source, an inverter circuit that converts DC power of the DC power source into high-frequency AC power, and output power of the inverter circuit as described above. Non-contact power transmission means by electromagnetic induction for non-contact power transmission to the scanner rotation unit, a high voltage generator for boosting and rectifying the output voltage of the non-contact power transmission means to generate a tube voltage, and applying the tube voltage X-ray tube for generating X-rays irradiated to the subject, an X-ray detector for detecting a transmitted X-ray dose transmitted through the subject, a tube voltage control device for controlling the tube voltage, and the X-ray Scanner rotation means for rotating the scanner rotation unit around the subject with the tube and the X-ray detector facing each other, and reconstructing a tomographic image of the subject from data detected by the X-ray detector With image processing equipment An X-ray CT apparatus comprising: a system controller that controls each device and each means based on a set scan condition, wherein the control relates to control of tube voltage and / or tube current for generating X-rays A signal, an anode drive control signal for controlling the rotation of the anode of the X-ray tube, and X-ray detection data detected by the X-ray detector are not transmitted between the scanner stationary unit and the scanner rotating unit. Non-contact signal transmission means for transmitting in contact is provided.

  The non-contact signal transmission means is preferably optical coupling in which the electrical / optical signal conversion element and the optical / electrical signal conversion element are opposed to each other.

  Also, tube voltage control signal output from the tube voltage control device to the inverter circuit, X-ray exposure output (start of tube voltage control) output from the system controller to the tube voltage control device, X-ray detector It is desirable to provide dedicated non-contact signal transmission means for transmitting the X-ray detection data of the subject detected by the above to the image processing apparatus.

  In the X-ray CT apparatus configured in this way, the transmission of power supplied from the power source to the X-ray tube and the signal transmission between the scanner stationary part and the scanner rotating part are made non-contact. The maintenance work of the slip ring like the X-ray CT apparatus becomes unnecessary.

  Further, the present invention provides an X-ray CT apparatus configured as described above, a tube voltage presetting means for applying a tube voltage not contributing to X-ray generation to the X-ray tube, and a state in which the tube voltage is preset. It is characterized by comprising tube voltage control starting means for starting tube voltage control.

  The tube voltage preset means and the tube voltage control start means include tube voltage switching means provided in the stationary part of the scanner, and the tube voltage preset means responds to the X-ray exposure start signal by the tube voltage switching means. A voltage preset signal is output as a drive signal for the inverter circuit, and the tube voltage control starting means sets the tube voltage from the tube voltage control device in place of the tube voltage preset signal when the tube voltage detection value reaches the preset value. It is desirable to be configured to output the signal as a drive signal for the inverter circuit.

  The X-ray CT apparatus configured as described above can reduce the time delay of the X-ray exposure timing because the X-ray tube voltage is controlled from the preset value that does not contribute to X-ray generation to the set tube voltage.

  According to the present invention, the transmission of power supplied to the X-ray tube and the signal transmission exchanged between the scanner stationary unit and the scanner rotating unit are made non-contact and a tube voltage that does not contribute to the generation of X-rays is applied. Since the tube voltage feedback control is started from the above, the time delay of the tube voltage control applied to the X-ray tube is shortened, and high-speed scanning becomes possible. In addition, the maintenance time for the power transmission means and the signal transmission means is shortened and the reliability is improved.

1 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to a first embodiment of the present invention. The circuit diagram which shows schematic structure of an inverter circuit. The timing chart of operation | movement description of an inverter circuit. The figure which shows the relationship between the output voltage of the inverter which generates the preset tube voltage which does not contribute to X-ray generation, and the conduction | electrical_connection ratio of a switching element. FIG. 2 is a block diagram showing a functional configuration of a tube voltage control unit of the X-ray CT apparatus shown in FIG. 3 is a flowchart for explaining the operation of the X-ray CT apparatus according to the first embodiment of the present invention. 3 is a flowchart for explaining the operation of tube voltage control in the first embodiment of the present invention. 3 is a timing chart for explaining the operation of tube voltage control in the first embodiment of the present invention. The block diagram which shows schematic structure of the X-ray CT apparatus of the 2nd Embodiment of this invention. The block diagram which shows the function structure of the tube voltage control part of the X-ray CT apparatus shown in FIG. 9 is a timing chart for explaining the operation of tube voltage control in the second embodiment of the present invention. FIG. 5 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to a third embodiment of the present invention. FIG. 13 is a block diagram showing a functional configuration of a tube voltage control unit of the X-ray CT apparatus shown in FIG. The figure which shows the whole structure of the X-ray CT apparatus of the 4th Embodiment of this invention.

Hereinafter, preferred embodiments of the X-ray CT apparatus of the present invention will be described in detail with reference to the accompanying drawings.
Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments of the present invention, and the repetitive description thereof will be omitted.

First Embodiment
FIG. 1 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to the first embodiment of the present invention. The X-ray CT apparatus according to the first embodiment of the present invention includes a scanner stationary unit 1 and a scanner rotating unit 2 as shown in FIG.

  The scanner stationary unit 1 is a power converter 11 that converts AC power supplied from a commercial power source 10 into AC power having a frequency higher than the frequency of the commercial power source 10, and an operation console 12 that is used to operate the CT system. A CT image is generated by using the system controller 13 for controlling the entire system based on the scanning conditions set by the operation console 12 and the X-ray transmission data of the subject detected by an X-ray detector described later. An image processing device 14 having an image reconstruction means, a display device 15 for displaying CT images and various information, a gantry (not shown) that rotatably supports the scanner rotation unit 2, and a rotation of the scanner rotation unit 2 And a scanner rotation driving unit (not shown) for driving. Note that an AND circuit 16 is provided between the power converter 11 and the system controller.

  The scanner rotating unit 2 includes a high voltage generator 30 that boosts the AC voltage output from the power converter 11 of the scanner stationary unit 1 and converts the boosted voltage into a DC voltage, and the DC voltage output from the high voltage generator 30. An X-ray tube 31 that emits X-rays when a high voltage is applied, a tube voltage detector 32 that detects a voltage (tube voltage) applied between the anode 31a and the cathode 31b of the X-ray tube 31, and a tube voltage A tube voltage control device 33 for controlling the tube current detector 34 for detecting a current (tube current) flowing in the filament of the cathode 31b of the X-ray tube 31, a tube current control device 35 for controlling the tube current, From the anode rotation driving device 36 for controlling the rotation of the anode of the X-ray tube 31, the X-ray detection unit 39 disposed opposite to the X-ray tube 31 with the subject P interposed therebetween, A collimator (not shown) that can variably set the irradiated X-ray field and a rotating frame (shown) Configured with a generally) and.

  Between the stationary scan unit 1 and the scan rotation unit 2, a non-contact power transmission unit 20 and a non-contact signal transmission unit 40 are disposed.

  Hereafter, the said structural requirement is demonstrated in detail. The power converter 11 includes a converter circuit 11a that converts AC power supplied from the commercial power supply 10 into DC power, and an inverter circuit 11b that converts this DC power into AC power having a frequency higher than the frequency of the commercial power supply 10. The inverter circuit 11b includes a plurality of power conversion semiconductor switching elements, for example, an inverter drive circuit 11c for switching and driving an IGBT (Insulated Gate Bipolar Transistor).

  FIG. 2 shows the configuration of the inverter circuit 11b. The inverter circuit 11b is configured as a full-wave bridge circuit by four power semiconductor switching elements IGBT1 to IGBT4.

  As shown in FIG. 3 (a), this full-wave bridge circuit operates at a predetermined inverter operating frequency (1 / 2T1), for example, 20 kHz, and as shown in FIGS. 3 (b) to (e) In the positive half cycle of the operating frequency, the conduction width T2 of the switching elements IGBT1 and IGBT4 is controlled, and in the negative half cycle of the inverter operating frequency, the conduction width T2 of the switching elements IGBT2 and IGBT3 is controlled. As a result, the DC voltage supplied from the converter circuit 11a is converted into an arbitrary high-frequency AC voltage and output from the inverter circuit 11b to the non-contact power transmission means 20.

  The conduction width T2 of the switching elements IGBT1 and IGBT4 and the conduction width T2 of the switching elements IGBT2 and IGBT3 are set to be the same.

  FIG. 4 shows the relationship between the conduction ratio T2 / T1 of the switching elements IGBT1 to IGBT4 and the output voltage (effective value) of the inverter circuit 11b. As shown in FIG. 4, the output voltage of the inverter circuit 11b can be controlled from 0 to the maximum Emax by changing the conduction ratio T2 / T1 from 0 to 1, but in this embodiment, the inverter circuit 11b The operation is started from the conduction ratio Ta that outputs the voltage Ea corresponding to the preset tube voltage value kVp set in advance.

  The output of the power conversion device 11 configured as described above is controlled by changing the conduction ratio of the power conversion semiconductor switching element IGBT of the inverter circuit 11b in accordance with a tube voltage control signal input to the inverter drive circuit 11c.

  The system controller 13 is detected by the scan start signal, projection angle signal, scan end signal, tube voltage setting signal, tube current setting signal, X-ray exposure preparation signal, X-ray exposure start signal, and X-ray detector 39. A signal for causing the image processing device 14 to capture X-ray transmission data of the subject, a signal to be displayed on the display device 15, and the like are generated, and the CT scan is controlled using these signals.

  The logical product circuit 16 outputs the tube voltage preset signal kVp or the tube voltage setting signal kVs to the inverter drive circuit 11c by the logical product of the X-ray exposure start signal Xrs output from the system controller 13 and the tube voltage control signal. It is.

  The non-contact power transmission means 20 is connected to the output side of the inverter circuit 11b, and is a ring-shaped first iron core disposed on the circumference of the scanner rotating part support frame (not shown) of the gantry of the scanner stationary part 2. Wound around a first winding 20a wound around (not shown) and a ring-shaped second iron core (not shown) formed on the circumference of a rotating frame (not shown) of the scanner rotating unit 2. And a second winding 20b disposed opposite to the first winding and connected to the input side of the high-voltage transformer 30a. The magnetic flux generated in the first winding 20a is configured to interlink with the second winding 20b via the iron cores. Thus, electromagnetic induction power transmission means is configured.

  The high voltage generator 30 boosts the output voltage of the power converter 11 transmitted from the non-contact power transmission means 20 with a high voltage transformer 30a, and the boosted AC voltage is converted into a direct current with a high voltage rectifier 30b. This is converted to a high voltage, and this high voltage is applied between the anode 31a and the cathode 31b of the X-ray tube 31.

  The tube voltage detector 32 (tube voltage detection means) detects the tube voltage applied to the X-ray tube 31, and the tube current detector 34 detects the tube current.

  The tube voltage control device 33 (tube voltage control means) is such that the actual tube voltage value kVd detected by the tube voltage detector 32 and the tube voltage set value kVs output from the system controller 13 match. This controls the conduction ratio of the plurality of power conversion semiconductor switching elements IGBT of the inverter circuit 11b.

  FIG. 5 is a block diagram showing a functional configuration of the tube voltage control device 33. As shown in FIG. This tube voltage control unit includes a tube voltage control unit 33A that combines proportional, integral, and differential control elements, and an A / D converter 33d.

  The tube voltage control unit 33A includes a controller (for example, composed of an MPU) 33a that controls tube voltage, a tube voltage feedback control unit 33b, and a switch 33c. The controller 33a inputs the tube voltage set value signal kVs of the scan condition output from the system controller 13, the X-ray exposure preparation signal Xrr, etc., and also provides a feedback (FB) control system reset signal kVfr to the tube voltage feedback control unit 33b. The tube voltage set value signal kVs is output to the switch 33c as an open / close signal kVsw. The FB control system reset signal kVfr is to reset the integral regulator and the differential regulator to 0 before the tube voltage feedback control is started.

  The tube voltage feedback control unit 33b includes a first adder circuit 33b1, an integral regulator 33b2, a proportional regulator 33b3, a differential regulator 33b4, and a second adder circuit 33b5, and constitutes a so-called PID control system.

  The switch 33c outputs the tube voltage control signal kVc to the inverter drive circuit 11c via the optical coupling 40a and the AND circuit 16.

  The A / D converter 33d converts the tube voltage detection value kVd output from the tube voltage detector 32 into a digital value.

  The tube current control device 35 is configured so that the actual tube current value detected by the tube current detector 34 matches the tube current setting value output from the system controller 13. The current flowing through the filament is controlled.

  This tube current control device 35 insulates the filament heating circuit 35a for generating an AC voltage for heating the filament of the cathode 31 of the X-ray tube 31, and the output AC voltage of the filament heating circuit 35a to insulate the X-ray tube 31. And a filament heating transformer 35b applied to the filament of the cathode 31b.

  The anode rotation drive device 36 supplies AC power to an anode rotation motor (not shown) for rotating the anode 31a of the X-ray tube 31, and the anode rotation drive device 36 is controlled by an anode rotation / stop signal output from the system controller 13. The rotation / stop of the anode 31a of the X-ray tube 31 is controlled.

  The high voltage transformer 30a, the high voltage rectifier 30b, the tube voltage detector 32, the tube current detector 34, and the filament heating transformer 35b are housed in a high voltage tank (not shown) and mounted on the scanner rotating unit 2. .

  The X-ray detector 39 includes an X-ray detector 39a for detecting X-rays transmitted through the subject P, a preamplifier 39b for amplifying the detection value of the X-ray detector 39a, and the output of the preamplifier 39b as digital data. And a data conversion unit 39c for converting the data into serial data for transmission to the image processing device 14. The X-ray detector 39a is formed by arranging a plurality of X-ray detection elements in a single row or a plurality of rows on an arc having a predetermined radius centered on the X-ray tube focal point. Since it is also publicly known, detailed description is omitted.

  The signal transmission means 40 (non-contact signal transmission means) by optical coupling includes an electrical / optical conversion unit that converts an electrical signal into an optical signal, and an optical / electrical conversion unit that converts an optical signal into an electrical signal. The electrical / optical conversion unit and the optical / electrical conversion unit are arranged between the scanner stationary unit 1 and the scanner rotating unit 2. In this embodiment, four sets of optical couplings are provided.

  The four sets of optical couplings are optical cups that transmit the tube voltage control signal kVc output from the tube voltage control device 33 to the inverter drive circuit 11c for switching and driving the power conversion semiconductor switching element IGBT of the inverter circuit 11b. Ring 40a, X-ray exposure preparation signal Xrr for preparing for X-ray exposure, tube voltage setting signal kVs, tube current setting signal, X-ray tube 31 anode rotation / stop signal, etc. Optical coupling 40c for transmitting a signal and a signal for instructing the X-ray detection unit 39 to take in X-ray detection data to the tube voltage control device 33, the tube current control device 35, the anode rotation drive device 36, and the X-ray detection unit 39 An optical coupling 40d for transmitting an X-ray detection data capturing end signal, a signal for monitoring the operation state of the tube voltage control device 33 and the tube current control device 35, etc. to the system controller 13, and an X-ray detection unit to be described later X-ray detection data detected by 39 It refers to an optical coupling 40e for transmitting data to the image processing apparatus 14.

  The tube voltage control signal kVc is also a feedback control signal for the inverter circuit and needs to be transmitted quickly. For this reason, the tube voltage control signal kVc is transmitted by the optical coupling 40a provided independently. Thereby, the time delay of tube voltage control can be reduced. This also makes it easy to synchronize the imaging of the moving organ of the subject with the biological signal.

  In addition, other X-ray control signals including the X-ray exposure preparation signal and X-ray detection data capture instruction signals are converted from parallel data to serial data by the system controller 13 and transmitted via the optical coupling 40c. It is transmitted to the scanner rotation unit 2. The transmitted serial data is converted into parallel data by the serial / parallel converter 37 and input to each device mounted on the scanner rotation unit 2.

  Further, the X-ray detection data capturing end signal, the monitor signal, and the like are converted into serial data by the parallel / serial converter 38 and transmitted to the system controller 13 through the optical coupling 40d.

  Further, the subject transmission data detected by the X-ray detector 39a and converted by the data converter 39c is transmitted to the image processing unit by the optical coupling 40e provided solely for exclusive use, similarly to the transmission of the tube voltage control signal. 14 is transmitted. In the present embodiment, one set of optical coupling for transmitting X-ray detection data to the image processing apparatus is shown, but the number of sets may be increased according to the amount of data to be transmitted or the transmission speed.

  The first embodiment of the present invention configured as described above uses non-contact power transmission means 20 by electromagnetic induction based on the principle of a rotary transformer for power transmission to the X-ray tube 31, and the tube voltage, tube current, etc. The power transmitted from the scanner stationary unit 1 to the scanner rotating unit 2 using the signal transmission means 40 by optical coupling for signal transmission of control signals related to X-ray control and X-ray detection data related to CT image generation, and Transmission of signals exchanged between the scanner stationary unit 1 and the scanner rotating unit 2 is made non-contact.

  In the signal transmission means 40 by the optical coupling, the tube voltage control signal that needs to be controlled in real time and the X-ray detection data that needs to be transmitted continuously are individually dedicated. The signal transmission means is provided, and is distinguished from other signal transmission means.

  Next, the operation of the X-ray CT apparatus of the present embodiment will be described with reference to FIGS.

(1) Setting scan conditions (Step S11)
The operator uses the operation console 12 to set the tube voltage and tube current, the scan speed (rotation speed of the scanner rotation unit), the X-ray collimation conditions, the scan start and end positions, and the bed on which the subject is placed. The scanning conditions such as the moving speed of the top plate (not shown) or the step feed pitch, the type of reconstruction filter function, and the field of view size (FOV) are set.

(2) Transmission of control signals and control parameters (step S12)
The scan conditions set in step S11 are input to the system controller 13, and control signals and control parameters generated from the system controller 13 based on the scan conditions are sent to the scanner stationary unit 1 and the scanner rotation unit 2 respectively. Is transmitted. This control signal includes a preset value of the tube voltage. That is, the control signal and the control parameter include the power conversion device 11 of the scanner stationary unit 1, the image processing device 14, the display device 15, a bed control device that moves and controls a bed on which a subject (not shown) is placed, and a scanner rotation unit. Is sent to a scanner rotation control device (not shown) that controls the rotation drive mechanism (not shown). Further, the control signal and the control parameter are the tube voltage control device 33, the tube current control device 35, the anode rotation drive device 36, and the anode rotation drive device 36, which are mounted on the scanner rotation unit 2 through the optical coupling 40c of the non-contact signal transmission means 40. It is transmitted to the X-ray detector 39.

(3) Preparation for X-ray exposure control (Step S13)
When the transmission of the control signal and the control parameter is completed, the power conversion device 11, the tube voltage control device 33, the tube current control device 35, the anode rotation drive device 36, etc. perform the preparation operation for the X-ray exposure control as shown below. Done.

(3-1) Determination of presence / absence of X-ray exposure preparation signal (step S131)
In order to irradiate X-rays from the X-ray tube 31, before applying a tube voltage to the X-ray tube 31, the filament of the cathode 31b of the X-ray tube is heated to a temperature corresponding to the set tube current. It is necessary to rotate the anode 31a. In order to perform these X-ray exposure preparation operations, the system controller 13 outputs an X-ray exposure preparation signal Xrr following transmission of the scan conditions.

  The X-ray exposure preparation signal Xrr output from the system controller 13 is transmitted to the tube voltage control device 33, the tube current control device 35, and the anode rotation drive device 36 via the optical coupling 40c and the serial / parallel converter 37. Is done. The presence or absence of the X-ray exposure preparation signal Xrr is determined by the CPU or MPU of the tube voltage control device 33, the tube current control device 35, and the anode rotation drive device 36. If the transmitted X-ray exposure preparation signal Xrr is present, the process proceeds to the next step S132. If the X-ray exposure preparation signal Xrr is “None”, the X-ray exposure preparation signal Xrr is “Yes”. Wait until

(3-2) Preparation for X-ray exposure (Step S132)
When the X-ray exposure preparation signal Xrr is input to the tube current control device 35, the X-ray tube filament heating circuit 35a is activated, the tube current set value is taken in from the system controller 13, and the X-ray tube 31 cathode 31b The filament is heated, and the anode 31a of the X-ray tube 31 is rotated at a predetermined rotational speed by an anode rotation signal.

(3-3) Preparation for tube voltage control (Step S133)
On the other hand, an X-ray exposure preparation signal Xrr is also input to the tube voltage control device 33 in order to prepare for tube voltage control. When the X-ray exposure preparation signal Xrr is input to the controller 33a of the tube voltage control device 33, the tube voltage preset signal kVp is output from the controller 33a via the switch 33c as the tube voltage control signal kVc.

(3-4) Setting tube voltage preset value (Step S134)
On the other hand, although the tube voltage preset kVp is input from the tube voltage control system 33A to the AND circuit 16, the tube voltage preset signal kVp is output to the inverter drive circuit 11c until the X-ray exposure start signal Xrs is generated. Therefore, the inverter circuit 11b does not start operation.

(4) Scan start preparation (step S14)
When a CT scan start command is input to the operation console 12 by the operator, the system controller 13 performs a scan start preparation operation.

  That is, a signal for rotating the rotating frame of the scanner rotating unit 2 is output from the system controller 13 to the scanner control device (not shown). Then, the rotation frame (not shown) of the scanner rotation unit 2 starts to rotate by a scanner rotation motor (not shown).

(5) X-ray exposure start position detection (S15)
The scanner rotation motor is connected to a rotary encoder (not shown) for detecting the rotation angle of the rotary frame, and an output pulse from the rotary encoder is measured by a scanner control device (not shown), This is input to the system controller 13. The system controller 13 indicates that the rotation speed of the scanner rotation frame has reached the set value, and the X-ray tube 31 on the rotation frame has reached a predetermined X-ray exposure start position (rotation frame angle). When X is detected, an X-ray exposure start signal Xrs is generated.

(6) X-ray exposure (step S16)
When this X-ray exposure start signal Xrs is input to the AND circuit 16, the tube voltage preset signal kVp output from the tube voltage control device 33 at this timing is input to the inverter drive circuit 11c. As a result, the inverter circuit 11b starts operating, and the preset tube voltage KVP that does not contribute to the generation of X-rays is applied to the X-ray tube 31.

  The tube voltage applied to the X-ray tube 31 is detected by the tube voltage detector 32, converted into a digital value by the A / D converter 33d, and input to the controller 33a. At this time, since the signal related to the target tube voltage is not input to the tube voltage feedback control unit 33b, the preset tube voltage KVP is not feedback-controlled, but the tube voltage preset value is supplied to the tube voltage control unit 33A as necessary. Feedback control may be performed by transmitting and storing in advance. The preset tube voltage value kVp that does not contribute to the generation of the X-ray is preferably set to about 1 kV when the maximum tube voltage is 150 kV, for example.

  When the detected tube voltage reaches the preset tube voltage KVP, the controller 33a outputs the FB control system reset signal kVfr, and resets the integral regulator 33b2 and the differential regulator 33b4 of the tube voltage feedback controller 33b to 0. To do. In addition, measurement of the tube voltage application time is started, and a switching signal kVsw for switching the connection of the switch 33c to the output line of the tube voltage feedback control unit 33b is also output. In this operation, since the time for the tube voltage to rise to the preset tube voltage KVP is about several μs, the X-ray exposure start signal Xrs is taken from the scanner stationary unit 2 through optical coupling and the tube voltage control signal is Compared with switching from the voltage preset signal kVp to the tube voltage set value signal kVs, the present embodiment can reduce the switching delay.

  As a result, the tube voltage feedback control unit 33b starts operating, and the tube voltage setting value signal kVs is output from the tube voltage control device 33. The tube voltage set value signal kVs is input to the inverter drive circuit 11c via the optical coupling 40a and the AND circuit 16.

  When the tube voltage set value signal kVs is input, the inverter drive circuit 11c causes the power semiconductor switching elements IGBT1 to IGBT4 of the inverter circuit 11b to output a voltage corresponding to the tube voltage set value KVS from the inverter circuit 11b. Control the phase angle. Then, the output voltage of the inverter circuit 11b is input to the high voltage transformer 30a of the high voltage generator 30 via the contactless power transmission means 20, boosted to the tube voltage set value KVS, and input to the high voltage rectifier 30b. Is converted into a DC voltage and applied to the X-ray tube 31. Then, the subject P is irradiated with X-rays from the X-ray tube 31.

  The tube voltage applied to the X-ray tube 31 is detected by the tube voltage detector 32, input to the tube voltage feedback control unit 33b via the A / D converter 33d of the tube voltage control device 33, and fed back by the PID control system. As a result, the tube voltage value is kept constant at the set value KVS.

(7) Collection of X-ray detection data (Step S17)
When the subject P is irradiated with the X-ray from the X-ray tube 31, the X-ray transmitted through the subject is detected by the X-ray detector 39a. This X-ray detection signal is amplified by a preamplifier 39b, and this amplified detection signal is converted into serial data by a data converter 39c, and image processing is performed via an optical coupling 40e provided exclusively for transmission of X-ray detection data. Is transmitted to the device 14.

  The system controller 13 continues to monitor the presence / absence of the scan end signal together with the collection status of the X-ray detection data, and continues the scan until the scan end signal is input.

(8) End of scanning (Step S18)
When the X-ray detection data for all views in the entire scan range is detected and transmitted to the image processing device 14 in step S17, a data collection end signal is sent from the image processing device 14 to the system controller 13, thereby the system A scan end signal is generated from the controller 13.

  This scan end signal is output to each control device (power conversion device 11, tube voltage control device 33, tube current control device 35, etc.), scanner control device, bed control device, etc., related to X-ray control. Then, the operation of each control device is stopped and the CT scan ends.

(9) CT image reconstruction (step S19)
In the image processing apparatus 14 to which the X-ray detection data is input, various correction processes are performed on the X-ray detection data to generate projection data. Then, an image reconstruction operation is performed using the projection data to generate reconstructed image data. Note that the reconstruction of the CT image is not started after the scan is completed, but the image reconstruction can be started as soon as X-ray detection data necessary for the image reconstruction is obtained even during the scan.

(10) Image display (Step S20)
A CT image obtained by performing image display control on the reconstructed image data is displayed on the display device 15 together with incidental information input by the operator from the operation console.

  According to the first embodiment of the present invention, an AND circuit is provided in the scanner stationary part, and an X-ray exposure start signal is input to the AND circuit, whereby the voltage applied to the X-ray tube is set from a preset value. Since switching is performed so that the set tube voltage is applied, there is no need to input an X-ray exposure start signal to the tube voltage control device of the scanner rotation unit via optical coupling, resulting in a delay in X-ray exposure timing. Absent.

<< Second Embodiment >>
FIG. 9 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to the second embodiment of the present invention. The difference between the second embodiment of the present invention and the first embodiment is that the scanner switch 1 is provided with a changeover switch circuit 17, and the changeover switch circuit 17 supplies the tube voltage to the inverter drive circuit 11c. The point at which the preset signal kVp and the tube voltage set value signal kVs are switched, and the tube voltage preset signal kVp is output from the system controller to the changeover switch circuit 17, and the tube voltage set value signal kVs is output from the tube voltage controller 33 to the changeover switch circuit 17 It is in the point that is output to.

  As shown in FIG. 9, the changeover switch circuit 17 includes a tube voltage preset switch 17a and a tube voltage setting switch 17b, and is connected and arranged between the system controller 13 of the scanner stationary unit 1 and the inverter drive circuit 11c. ing. The tube voltage preset signal kVp is input from the system controller 13 to the input terminal of the tube voltage preset switch 17a. On the other hand, the tube voltage control signal kVc output from the tube voltage control device 33 is input to the input terminal of the tube voltage setting switch 17b via the optical coupling 40a.

  These switches 17a and 17b are controlled to operate in reverse so that the switch 17b is turned off when the switch 17a is turned on and the switch 17b is turned off when the switch 17a is turned on.

  The control signal for turning on the tube voltage preset switch 17a and turning off the tube voltage setting switch 17b is synchronized with the X-ray exposure preparation signal Xrr, and the control signal for turning on the tube voltage setting switch 17b and turning off the tube voltage preset switch 17a. Are output from the system controller 13 in synchronism with the scan start signal SCs, and the switches 17a and 17b are turned off while there is no on signal.

  FIG. 10 is a block diagram showing a functional configuration of the tube voltage control device 33 in the present embodiment. As shown in the figure, the tube voltage control device 33 of this embodiment includes a tube voltage control unit 33B and an A / D converter 33d. The tube voltage control unit 33B includes a controller 33e and a tube voltage feedback control unit 33b. The controller 33e receives the X-ray exposure preparation signal Xrr, the tube voltage set value signal kVs, and the scan start signal SCs, and the tube voltage set value signal kVs is changed to the tube voltage feedback control unit 33b in response to the input of the scan start signal SCs. Is output to the first adder 33b1.

  The operation of the second embodiment will be described. As shown in the time chart of FIG. 11, the tube voltage preset switch 17a is turned on by the X-ray exposure preparation signal Xrr output from the system controller 13, and the tube voltage preset signal kVp is input to the inverter drive circuit 11c. As a result, the inverter circuit 11b starts operating, and the tube voltage preset value KVP is applied to the X-ray tube 31.

  Next, when the scan start signal SCs is output from the system controller 13, in the tube voltage control device 33, the controller 33e outputs the tube voltage set value signal kVs to the tube voltage feedback control unit 33b. As a result, the tube voltage control signal kVc, that is, the tube voltage set value signal kVs is output to the input terminal of the tube voltage setting switch 17b via the optical coupling 40a. However, since the tube voltage setting switch 17b is in the OFF state at this timing, the tube voltage setting value signal kVs is not output to the inverter drive circuit 11c.

  When the scanner rotation unit 2 starts rotating by the scan start signal SCs and the X-ray exposure start signal Xrs is input from the system controller 13 to the tube voltage setting switch 17b, the tube voltage setting switch 17b is turned on and the tube voltage preset switch 17a turns off. As a result, the input to the inverter drive circuit 11c is switched to the tube voltage set value signal kVs, a voltage corresponding to the set tube voltage is output from the inverter circuit 11b, and the tube voltage rapidly rises to the set value KVS.

  According to the second embodiment, since the signal for switching the tube voltage from the preset value KVP to the set value KVS is directly output from the system controller 13 to the changeover switch circuit 17 provided in the scanner stationary portion, the switching time loss is There is no.

<< Third Embodiment >>
FIG. 12 is a block diagram showing a schematic configuration of an X-ray CT apparatus according to the third embodiment of the present invention. In the third embodiment of the present invention, in order to perform tube voltage presetting and control for X-ray irradiation in the tube voltage control device 33 mounted on the scanner rotating unit 2, as shown in FIG. The tube voltage preset switch 17a and the tube voltage setting switch 17b of the second embodiment are provided in the tube voltage control unit 33C of the tube voltage control device 33, and as shown in FIG. 12, for X-ray exposure start signal Xrs transmission A non-contact transmission means (40b) is provided exclusively.

  FIG. 13 is a functional block diagram of the tube voltage control unit 33C of the tube voltage control device 33 of the present embodiment. The operation of the tube voltage control unit 33C is different from the operation of the tube voltage control unit 33A of the first embodiment.First, the tube voltage preset signal kVp is input to the controller 33f via the optical coupling 40c. This tube voltage preset signal kVp is output to the tube voltage preset switch 17a at the timing when the X-ray exposure preparation signal Xrr is input to the controller 33f, and passes through the tube voltage preset switch 17a which is turned on by the X-ray exposure preparation signal Xrr. This is the point that is output as the tube voltage control signal kVc.

  The tube voltage preset signal kVp is output to the inverter drive circuit 11c via the optical coupling 40a, and an AC voltage corresponding to the tube voltage preset value is supplied from the inverter circuit 11b to the non-contact power transmission means 20.

  The second difference between the operation of the tube voltage control unit 33C and the operation of the tube voltage control unit 33A of the first embodiment is that the X-ray exposure start signal Xrs from the system controller 13 is input to the controller 33f, and the tube voltage The setting signal kVs is output to the tube voltage setting switch 17b at the timing when the X-ray exposure start signal Xrs is input to the controller 33f, and is output via the tube voltage setting switch 17b turned on by the X-ray exposure start signal Xrs. It is a point.

  If the X-ray exposure start signal Xrs is transmitted from the scanner rotating unit 2 via the optical coupling 40c, it may interfere with the transmission of other signals, and the X-ray exposure start timing may not be controlled quickly. is assumed. Therefore, a dedicated optical coupling 40b for transmitting the X-ray exposure start signal Xrs from the system controller 13 to the high voltage control device is provided.

  In the third embodiment, when the tube voltage preset signal kVp is input from the system controller 13 together with the X-ray exposure preparation signal Xrr to the tube voltage control device 33 via the optical coupling 40c, the tube voltage preset value is set to the controller 33f. It is stored in the storage unit and output to the tube voltage preset switch 17a. Since the tube voltage preset switch 17a is turned on by the tube voltage preset switch on signal output at the timing when the X-ray exposure preparation signal Xrr is input to the controller 33f, the tube voltage preset signal kVp passes through the optical coupling 40a. And output to the inverter drive circuit 11c. As a result, the inverter circuit 11b is driven, and a voltage that does not contribute to X-ray exposure is applied to the X-ray tube 31.

  The tube voltage preset signal kVp is continuously output to the inverter drive circuit 11c until the X-ray exposure start signal Xrs is input from the system controller 13 and the tube voltage preset switch 17a is turned off.

  When the X-ray exposure start signal Xrs is input from the system controller 13 to the controller 33f via the optical coupling 40b, the controller 33f outputs a signal for turning off the tube voltage preset switch 17a and turning on the tube voltage setting switch 17b. Is output. At the same time, an FB control system reset signal kVfr is output from the controller 33f to the tube voltage feedback control unit 33b, and the FB control system is in a state where feedback control is possible. As a result, the tube voltage control signal kVc is switched from the tube voltage preset signal kVp to the tube voltage setting signal kVs.

  In the third embodiment, since the X-ray exposure start signal is transmitted from the system controller to the tube voltage control device via the optical coupling, the X-ray exposure is compared with the first embodiment and the second embodiment. If it is applied to an apparatus that has a slightly low responsiveness at the start of exposure but does not have a high scanning speed, the purpose of simplifying the maintenance and inspection work can be achieved.

<< Fourth Embodiment >>
Next, a fourth embodiment of the present invention will be described. FIG. 14 is a block diagram showing a schematic configuration of the X-ray CT apparatus according to the fourth embodiment. The fourth embodiment of the present invention is a modification of the third embodiment described above. The difference between the fourth embodiment is that the tube voltage control device 33 of the third embodiment is a scanner in the fourth embodiment. This is a point provided in the stationary part 1.

  Therefore, in the fourth embodiment, the optical coupling 40a is used to transmit the tube voltage detection value detected by the tube voltage detector 32 to the tube voltage control device 33 provided in the scanner stationary unit 1, and the third The optical coupling 40b provided in this embodiment is not necessary.

  The tube voltage preset operation and the tube voltage setting operation in the fourth embodiment are the same as those in the third embodiment, but the X-ray exposure start signal Xrs does not pass through optical coupling from the system controller to the scanner stationary unit. Is directly output to the tube voltage control device provided to the X-ray exposure start responsiveness is superior to that of the third embodiment, and is substantially equivalent to the first embodiment and the second embodiment. Responsiveness of starting X-ray exposure is obtained. In addition, since the tube voltage control device is provided in the scanner stationary part, the fourth embodiment can reduce the weight of the scanner rotating part (reducing the moment of inertia) and is suitable for speeding up the scanner.

  As described above, the X-ray CT apparatus according to the present invention has been described using the first to fourth embodiments. However, the present invention is not limited to these embodiments, and is the technical idea of the present invention. Control of tube voltage for scanning from the state in which tube voltage that does not contribute to generation of X-rays is applied and power transmission to the tube is made non-contact between transmission of power and signal transmission exchanged between the scanner stationary unit and scanner rotation unit Any form may be used as long as it starts.

  For example, the following modifications are possible.

  (1) In the above embodiment, an X-ray exposure preparation signal output from the system controller is provided separately from the scan conditions in order to perform an X-ray exposure preparation operation including a preset of the tube voltage. It may be replaced with a scan condition setting signal.

  (2) Although description of the control signal of the collimator that variably sets the X-ray irradiation field is omitted, it is preferable that the drive control signal of the collimator is also transmitted from the system controller of the scanning stationary unit by the non-contact signal transmission means. . In this case, the non-contact signal transmission means may share a signal transmission device such as a tube voltage and a tube current, or may be provided exclusively.

  (3) As the non-contact signal transmission means, other means such as an electric field, a magnetic field, an electromagnetic wave or the like may be used instead of the optical coupling.

  (4) The feedback control of the tube voltage is also possible by a method that starts by judging from the current or voltage of the high voltage generator 30 such as the output current or output voltage of the high voltage transformer 30a.

  (5) Although the tube voltage has been described with respect to an example in which the operating phase of the switching element of the inverter circuit is controlled, a method of controlling the operating frequency using a resonant inverter circuit, or a combination of the above phase and frequency is used. The converter circuit 11a can be configured to control its output DC voltage, and the converter circuit and inverter circuit can be used together to control the tube voltage.

  (6) Although the example in which the power of the DC power supply of the inverter circuit is supplied from a three-phase AC power supply has been described, if the power required for the X-ray tube is possible, supply it from a single-phase AC power supply or a battery. Also good.

  1 Scanner stationary part, 2 Scanner rotating part, 11b Inverter circuit, 11c Inverter drive circuit, 12 Operation console, 13 System controller, 14 Image processing device, 16 AND circuit, 17 Changeover switch circuit, 20 Non-contact power transmission means, 30a High voltage transformer, 30b High voltage rectifier, 31 X-ray tube, 32 tube voltage detector, 33 tube voltage control device, 34 tube current detector, 35 tube current control device, 36 anode rotation drive device, 39 X-ray detection unit 40 Non-contact signal transmission means, 40a-40e optical coupling

Claims (9)

Scanner stationary unit, scanner rotating unit, DC power source, inverter circuit for converting DC power of the DC power source into high frequency AC power, and electromagnetic induction for transmitting output power of the inverter circuit to the scanner rotating unit in a contactless manner Generates a tube voltage by boosting and rectifying the output voltage of the contactless power transmission means, and generating X-rays to which the tube voltage is applied to irradiate a subject An X-ray tube that detects a transmitted X-ray dose that has passed through the subject, a tube voltage detector that detects a tube voltage applied to the X-ray tube and outputs a tube voltage detection value; A tube voltage control device that controls the tube voltage according to the tube voltage detection value, and a scanner rotation that rotates the scanner rotation unit around the subject with the X-ray tube and the X-ray detector facing each other. Means and the X-ray detector A tomographic image of the subject from the detected data and the image processing apparatus for reconstructing, a system controller for controlling the respective devices and the respective units based on the set scanning conditions, the control of the tube voltage I a signal according and a non-contact signal transmission means for transmitting a non-contact between said scanner rotation unit and the scanner stationary portion,
The inverter circuit is a circuit that is provided in the scanner stationary portion and operates according to a control signal including a tube voltage control signal output from the tube voltage control device,
The control signal is changed from a zero signal to a tube voltage preset signal that is a signal corresponding to a tube voltage value that does not contribute to X-ray generation, and further from the tube voltage preset signal to a tube voltage value set by an operation console. An X-ray CT apparatus further comprising signal switching means for switching to a certain tube voltage setting signal at a timing determined based on at least one of an X-ray exposure preparation signal and an X-ray exposure start signal . The tube voltage control device is provided in the scanner rotation unit,
The non-contact signal transmission means transmits the tube voltage control signal as a signal related to the control of the tube voltage,
The signal switching means includes a switch of the tube voltage control device, and when the X-ray exposure start signal is issued, switches the control signal from a zero signal to the tube voltage preset signal, and the tube voltage detection value is the X voltage detection value. 2. The X-ray CT apparatus according to claim 1, wherein when a tube voltage value that does not contribute to line generation is reached, the control signal is switched from the tube voltage preset signal to the tube voltage setting signal. The tube voltage control device is provided in the scanner rotation unit,
The non-contact signal transmission means transmits the tube voltage control signal as a signal related to the control of the tube voltage,
The signal switching means is a switch provided in the scanner stationary unit, and when the switch receives the X-ray exposure preparation signal, the control signal is switched from a zero signal to the tube voltage preset signal, and the switch is the X 2. The X-ray CT apparatus according to claim 1, wherein when the radiation exposure start signal is received, the control signal is switched from the tube voltage preset signal to the tube voltage setting signal. The tube voltage control device is provided in the scanner rotation unit,
The non-contact signal transmission means transmits the tube voltage control signal as a signal related to the control of the tube voltage,
The signal switching means is a switch of the tube voltage control device, and when the switch receives the X-ray exposure preparation signal, the control signal is switched from a zero signal to the tube voltage preset signal, and the switch 2. The X-ray CT apparatus according to claim 1, wherein when the radiation exposure start signal is received, the control signal is switched from the tube voltage preset signal to the tube voltage setting signal. The tube voltage control device is provided in the scanner stationary part,
The non-contact signal transmission means transmits the tube voltage detection value as a signal related to the control of the tube voltage,
The signal switching means is a switch of the tube voltage control device, and when the switch receives the X-ray exposure preparation signal, the control signal is switched from a zero signal to the tube voltage preset signal, and the switch 2. The X-ray CT apparatus according to claim 1, wherein when the radiation exposure start signal is received, the control signal is switched from the tube voltage preset signal to the tube voltage setting signal. 6. The non-contact signal transmission means is an optical coupling formed by making an electrical / optical signal conversion element and an optical / electrical signal conversion element face each other. X-ray CT system. Signals according to the control of the tube voltage, X according to any one of claims 1 to 5, characterized in that the feed transfer through the non-contact signal transmission means provided in the transmission-only of the signal Line CT device. The X-ray exposure start signal is transmitted from the system controller to the tube voltage control device via non-contact signal transmission means provided exclusively for transmission of the X-ray exposure start signal. X-ray CT apparatus according to 4. A logical product circuit that outputs a logical product of the control signal output from the switch and the X-ray exposure start signal output from the system controller to the inverter circuit, and is provided in the stationary scanner unit; The X-ray CT apparatus according to claim 2, wherein:

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