JP2006051064A - Radiation therapy apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation therapy apparatus capable of controlling a dose rate of electron beams or radiations without changing a repetition frequency of high energy electron beams. <P>SOLUTION: The radiation therapy apparatus 1, which accelerates low energy electron beams from an electron gun 2 in an accelerating tube 3 and emits electron beams or radiations from an irradiation part 5 when the accelerated high energy electron beams are conveyed to the irradiation part 5, is equipped with a bending magnet 4 for switching whether or not to convey the high energy electron beams accelerated by the accelerating tube 3 to the irradiation part 5 and controls the switching to realize a desired dose rate of the electron beams or radiations to be emitted from the irradiation part 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiotherapy apparatus for performing radiation therapy by irradiating an affected area with an electron beam or radiation, and more particularly to a radiotherapy apparatus that irradiates an electron beam or radiation while controlling a dose rate to a desired level.

  Radiotherapy is a treatment method in which an electron beam or radiation is applied to a lesioned part of a patient. The more the electron beam or radiation is concentrated on the lesioned part while the exposure of the normal tissue around the lesioned part is kept low, the higher the antitumor effect treatment can be performed. One irradiation method for concentrating an electron beam or radiation on a lesion is rotational irradiation. This irradiation method is a method in which an electron beam or radiation irradiation source is circulated around a patient, radiation is irradiated from the irradiation source toward a lesioned portion, and an electron beam or radiation is irradiated from around the lesioned portion.

  As a radiotherapy apparatus for performing treatment by irradiating an electron beam or radiation by such an irradiation method, an electron gun and a low energy electron beam supplied from the electron gun are converted into a high energy electron beam of several MeV to several tens MeV. There is a configuration including an electron beam accelerator for output and an irradiation unit that converts a high-energy electron beam into an electron beam as it is or converts it into radiation and irradiates a lesioned part (for example, see Patent Document 1).

  In such a radiotherapy apparatus, the supply of the low energy electron beam from the electron gun to the electron beam accelerator generates a voltage pulse by a high voltage power source that receives the trigger pulse from the trigger pulse oscillator, and this voltage pulse is applied to the electron gun. Is done when. The electron beam accelerator is supplied with a microwave from a microwave generation source that has received a trigger pulse from the trigger pulse oscillator, and a low energy electron beam supplied from an electron gun during a period in which the microwave is supplied. Is accelerated by a microwave electric field and output as a high energy electron beam from an electron beam accelerator. The high-energy electron beam output from the electron beam accelerator is conveyed to the irradiation unit, and is irradiated as it is as an electron beam or converted into radiation from the irradiation unit.

  An irradiation unit for irradiating an affected part with an electron beam or radiation is housed in a gantry, and the electron beam or radiation is irradiated from the periphery of the lesioned part while irradiating the gantry around the patient with the irradiation part. Is irradiated.

  When rotating irradiation is performed with such a radiation therapy apparatus, it is necessary to make the dose of the electron beam or radiation per angle uniform in order to irradiate the electron beam or radiation uniformly. Here, the irradiation unit is a heavy object for shielding high-energy radiation, shaping an electron beam or radiation irradiation field, and adjusting a dose distribution in the irradiation field, and a gantry containing the irradiation unit. Is also heavy. Therefore, controlling the rotation speed of the gantry so that the dose per angle is uniform has a limit in response speed. For example, it is very difficult to rotate the gantry at a constant speed in order to make the dose per angle uniform immediately after the rotation irradiation is started.

For this reason, in order to make the dose of the electron beam or radiation per angle uniform, it is necessary to change the dose rate of the electron beam or radiation irradiated from the irradiation unit according to the rotation speed of the gantry. Therefore, in order to change the dose rate of the electron beam or radiation according to the rotation speed of the gantry, the repetition frequency of the pulsed high energy electron beam generated from the electron beam accelerator is changed by changing the repetition frequency of the trigger pulse. Thus, there is a radiotherapy device that controls the dose rate (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 2001-9050 JP-A-6-154349

  Here, the work rate of the microwave supplied to the electron beam accelerator is W, the heat loss at the electron beam accelerator is H, the current of the high energy electron beam is I, and the acceleration received by the electron beam incident on the electron beam accelerator is V. Then, from the law of energy conservation, W (microwave power) = H (heat loss) + IV (electron beam acceleration). By the way, when the repetition frequency of the high energy electron beam is increased, the temperature in the electron beam accelerator is increased, the resistance value of the inner surface of the acceleration tube constituting the electron beam accelerator is increased, and the heat loss H is further increased. According to the law of conservation of energy, the power I / V used for acceleration is reduced by the increase in the heat loss H. As the work power I · V used for acceleration decreases, the acceleration V received by the electron beam, that is, the energy of the high-energy electron beam to be output and the current value I decrease. Conversely, when the repetition frequency of the high-energy electron beam is lowered, the heat loss H decreases, and the energy (acceleration V received by the electron beam) or the current value I increases accordingly. That is, when the repetition frequency of the trigger pulse is changed as in the past to control the dose rate of the electron beam or radiation emitted from the irradiation unit, the energy of the high energy electron beam and its current value I change. Become.

  When the energy of the high-energy electron beam changes in this way, the dose distribution of the irradiated electron beam or radiation is not desired, and it is very difficult to perform effective treatment. Further, there is a problem that the dose rate changes when the current value I of the high energy electron beam changes.

  The objective of this invention is providing the radiotherapy apparatus which can control the dose rate of an electron beam or a radiation, without changing the repetition frequency of a high energy electron beam.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that the electron beam generated by the electron beam generating means is accelerated by the accelerating means and conveyed to the irradiation means, and from the irradiation means in the form of an electron beam or radiation A radiation therapy apparatus that performs irradiation, comprising: a deflecting unit that switches whether or not to transport an electron beam accelerated by the accelerating unit to the irradiating unit, wherein the deflecting unit is an electron beam irradiated from the irradiating unit or The switching control is performed so that the radiation dose rate becomes a desired one.

  In the invention according to the first aspect, when the electron beam generated by the electron beam generating unit is accelerated by the accelerating unit and the accelerated electron beam is conveyed to the irradiating unit, an electron beam or radiation is emitted from the irradiating unit. Irradiation takes place in the form of Whether the electron beam accelerated by the accelerating means is transferred to the irradiating means is switched by the deflecting means. The deflection unit performs switching control so that the dose rate of the electron beam or radiation irradiated from the irradiation unit becomes a desired one. Thereby, the electron beam or radiation of a desired dose rate is irradiated from an irradiation means.

  According to a second aspect of the present invention, the deflection unit according to the first aspect includes an electromagnet or a coil, and a pulse current having a repetition frequency corresponding to the desired dose rate is supplied to the electromagnet or the coil. The switching control is performed.

  In the invention according to claim 2, a pulse current having a repetition frequency corresponding to the desired dose rate is supplied to the electromagnet or the coil, and switching control is performed. A dose rate electron beam or radiation is applied.

  According to the first aspect of the present invention, the dose rate of the electron beam or radiation can be controlled without changing the repetition frequency of the high energy electron beam.

  According to the second aspect of the present invention, the direction of the electron beam accelerated by the accelerating means is switched by the electromagnet or the coil, whereby the dose rate of the electron beam or radiation can be controlled.

Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a first embodiment of the radiotherapy apparatus of the present invention, FIG. 2 is a diagram showing a radiation dose rate setting value set in a synchronous VF converter, and FIG. 3 is a radiotherapy shown in FIG. It is a pulse sequence figure in an apparatus.

  The radiotherapy apparatus 1 of this example includes an electron gun 2 constituting an electron beam generating means, an acceleration tube 3 as an accelerating means for accelerating a low energy electron beam supplied from the electron gun 2, a deflection electromagnet 4, and radiation. The irradiation part 5 which irradiates is provided. The electron gun 2, the acceleration tube 3, the bending electromagnet 4, and the irradiation unit 5 are housed in a gantry (not shown).

  The electron gun 2 is adapted to make a low energy electron beam incident on the acceleration tube 3. The electron gun 2 outputs a low energy electron beam when a voltage pulse is applied from the high voltage power source 6. When the high voltage power source 6 receives a trigger pulse (see FIG. 3) from the trigger pulse oscillator 7, the high voltage power source 6 generates a voltage pulse. When this voltage pulse is applied to the electron gun 2, the high voltage power source 6 is shown in FIG. Thus, a low energy electron beam is output in a pulse shape. That is, a low energy electron beam is output from the electron gun 2 in a pulsed manner in synchronization with the trigger pulse from the trigger pulse oscillator 7.

  A low energy electron beam incident on the acceleration tube 3 from the electron gun 2 is accelerated in the acceleration tube 3. Specifically, a pulsed microwave (see FIG. 3) is supplied to the acceleration tube 3 from the microwave oscillator 8, and the low energy electron beam is accelerated in the acceleration tube 3 by the microwave and accelerated. A high energy electron beam is output from the tube 3. The microwave oscillator 8 receives the trigger pulse from the trigger pulse oscillator 7 and oscillates the pulsed microwave.

  The deflection electromagnet 4 constitutes a deflection means for switching whether or not the high energy electron beam accelerated by the acceleration tube 3 is conveyed to the irradiation unit 5. The deflection electromagnet 4 performs switching control so that the dose rate of radiation irradiated from the irradiation unit 5 becomes a desired one.

  The switching control will be described in detail below. The deflection electromagnet 4 deflects the direction of the high-energy electron beam output from the acceleration tube 3 toward the irradiation unit 5 when it is energized by receiving a pulsed deflection current (pulse current) from the current source 9. It is like that. On the other hand, when the deflection electromagnet 4 is in a non-energized state, the direction of the high-energy electron beam output from the acceleration tube 3 is directed to the shielding material 10 provided at a position different from the irradiation unit 5 in the gantry. It is designed to deflect. That is, the high-energy electron beam output from the acceleration tube 3 is switched between the direction of the irradiation unit 5 and the direction of the shielding material 10 by the deflection electromagnet 4.

  The shielding material 10 decelerates and blocks the incident high-energy electron beam and shields the generated braking X-ray. When the high-energy electron beam is deflected to the shielding material 10 (when the deflection electromagnet 4 is not energized), the irradiation unit 5 is not irradiated with radiation and is deflected to the irradiation unit 5 ( Radiation is applied when the deflection electromagnet 4 is energized.

  The energization of the deflection electromagnet 4 will be described in detail. The deflection electromagnet 4 is energized by receiving a pulsed deflection current from the current source 9. When a deflection pulse (see FIG. 3) is output from the synchronous VF converter 11, the current source 9 receives the deflection pulse and outputs a pulsed deflection current.

  The synchronous VF converter 11 receives the trigger pulse from the trigger pulse oscillator 7 and outputs it to the current source 12 as a deflection pulse having a predetermined repetition frequency. This predetermined repetition frequency corresponds to a predetermined radiation dose rate setting value set in advance in the synchronous VF converter 11.

  Here, the radiation dose rate setting value set in the synchronous VF converter 11 will be described. This radiation dose rate setting value is a dose rate of desired radiation to be irradiated from the irradiation unit 5. In the synchronous VF converter 11, for example, a radiation dose rate setting value that changes with the passage of time is set as shown in FIG. This radiation dose rate set value is a set value such that the dose per angle in the irradiation target of radiation is uniform according to the rotational speed of the gantry. This setting value will be described in more detail. The rotation speed of the gantry gradually increases as the rotation starts, and eventually becomes constant. When the rotation is stopped, the rotation speed gradually decreases and stops. Therefore, the radiation dose rate set value becomes a set value that gradually increases after starting the gantry rotation and becomes constant according to the rotation speed of the gantry, and gradually decreases when the gantry stops rotating. ing.

  The synchronous VF converter 11 receives the trigger pulse from the trigger pulse oscillator 7 and outputs a deflection pulse having a repetition frequency according to the radiation dose rate setting value as described above. The repetition frequency of such a deflection pulse becomes constant after gradually increasing immediately after the start of rotation of the gantry according to the radiation dose rate setting value, and changes so as to gradually decrease when the rotation of the gantry stops.

  The deflection electromagnet 4 is inputted with a pulsed deflection current having the same repetition frequency as that of the deflection pulse. As a result, the high-energy electron beam output from the accelerating tube 3 is deflected in the direction of the irradiation unit 5 as described above, and the irradiation unit 5 emits radiation in a pulsed manner as shown in FIG. It is like that. The dose rate of the radiation irradiated from the irradiation unit 5 is proportional to the repetition frequency of the deflection pulse and is equal to the set value of the radiation dose rate. In other words, the synchronous VF converter 11 outputs a deflection pulse having a repetition frequency such that the dose rate of the radiation irradiated from the irradiation unit 5 becomes a desired one.

  Although not shown, the irradiation unit 5 includes a target, a flattening filter, an irradiation field limiter (collimator), and the like. When the irradiation unit 5 receives a high energy electron beam output from the accelerating tube 3 and deflected by the deflecting electromagnet 4, the irradiation unit 5 converts the high energy electron beam into an X-ray with a target of a high atomic number material, for example, A dose distribution is flattened by a flattening filter, and radiation is limited by an irradiation field limiter to output radiation. However, the irradiation part 5 may output the incident high energy electron beam as it is as an electron beam.

Next, the operation of the radiation therapy apparatus 1 configured as described above will be described.
In the radiotherapy apparatus 1 of this example, a low energy electron beam is output in a pulse form from the electron gun 2 in synchronization with the trigger pulse oscillated from the trigger pulse oscillator 7 and incident on the acceleration tube 3 and the acceleration tube 3. A pulsed microwave is input to the. The output of the low energy electron beam from the electron gun 2 is performed when the high voltage power supply 6 that has received the trigger pulse from the trigger pulse oscillator 7 generates a voltage pulse and this voltage pulse is applied to the electron gun 2. The microwave input to the accelerating tube 3 is oscillated from the microwave oscillator 8 that has received the trigger pulse from the trigger pulse oscillator 7.

  In the acceleration tube 3 on which the low energy electron beam is incident, the low energy electron beam is accelerated by the microwave, and the high energy electron beam is output from the acceleration tube 3. The high energy electron beam output from the accelerating tube 3 is directed toward either the irradiation unit 5 or the shielding material 10.

  The direction of the high energy electron beam is switched by the deflection electromagnet 4. Specifically, when a deflection pulse is output from the synchronous VF converter 11, a deflection current is output from a current source, and the deflection electromagnet 4 is energized, the high energy electron beam is directed to the irradiation unit 5. Is deflected. And radiation is irradiated from the irradiation part 5 in which the high energy electron beam was entered. On the other hand, when the deflection pulse is not output from the synchronous VF converter 11 and the deflection electromagnet 4 is in a non-energized state, the high energy electron beam is deflected to the shielding material 10. At this time, no radiation is irradiated from the irradiation unit 5. The deflection pulse is output at a repetition frequency corresponding to the radiation dose rate setting value, whereby the irradiation unit 5 emits radiation having a dose rate equal to the radiation dose rate setting value. That is, as shown in FIG. 2, the dose rate of the radiation irradiated from the irradiation unit 5 becomes constant after gradually increasing from the start of rotation of the gantry, and gradually decreases when the rotation of the gantry stops, The dose per angle in the irradiation target is uniform.

  The trigger pulse, low energy electron beam, microwave, deflection pulse, and radiation pulse sequence will be described with reference to FIG. FIG. 3 shows a pulse sequence of the trigger pulse, the low energy electron beam, the microwave, the deflection pulse, and the radiation from the start of rotation of the gantry to the constant rotation speed. In the figure, in synchronization with the trigger pulse oscillated from the trigger pulse oscillator 7, a high energy electron beam is output in a pulse shape, and a pulsed microwave is oscillated. In addition, a deflection pulse is also output in synchronization with the trigger pulse, but the repetition frequency of the deflection pulse changes corresponding to the radiation dose rate setting value set in the synchronous VF converter 11. In FIG. 3, the deflection pulse has a constant frequency after changing from a low frequency to a high frequency. When the trigger pulse, the low energy electron beam, the microwave, and the deflection pulse are all output from the irradiation unit 5, the radiation is irradiated in a pulse form from the irradiation unit 5. The dose rate of the irradiated radiation becomes constant after gradually increasing.

  According to the radiotherapy apparatus 1 of this example, the dose rate of the radiation irradiated from the irradiation unit 5 can be controlled by changing the repetition frequency of the deflection pulse and the deflection current. And the dose per angle in irradiation object can be made uniform by controlling the dose rate of the radiation irradiated from the irradiation part 5 according to the rotational speed of a gantry.

  And according to the radiotherapy apparatus 1 of this example, since the radiation dose rate can be controlled without changing the repetition frequency of the high energy electron beam as in the prior art, the energy of the high energy electron beam is reduced. There is no change, and a desired dose distribution can be obtained, whereby an effective treatment can be performed. In addition, since the current value of the high energy electron beam does not change, the dose rate does not change.

  In the present embodiment described above, the radiation dose rate set value set in the synchronous VF converter 11 is gradually increased and becomes constant in accordance with the rotational speed of the gantry as shown in FIG. Although it is designed to descend, it is not limited to this, for example, to avoid irradiating parts such as the patient's spinal cord where radiation should be kept as low as possible, according to the treatment plan, You may set so that the dose rate of the irradiated radiation may go up and down.

Next, a second embodiment of the radiotherapy apparatus according to the present invention will be described. FIG. 4 is a view showing a main part of the radiotherapy apparatus of the second embodiment.
The radiotherapy apparatus 20 of this example includes a microtron electron accelerator 21. When a high energy electron beam accelerated by the microtron electron accelerator 21 is conveyed to an irradiation unit (not shown), it is converted into radiation. Irradiated. As in the first embodiment, the irradiation unit includes a target, a flattening filter, an irradiation field limiter, and the like, and is housed in a gantry (not shown). However, the irradiation unit may irradiate an electron beam.

  The microtron electron accelerator 21 may be separated from the gantry or may be housed in the gantry. The configuration of the microtron electron accelerator 21 will be described in detail. The microtron electron accelerator 21 includes a uniform magnetic field coil 22 that generates a uniform magnetic field, and an acceleration cavity 23 is provided in the uniform magnetic field coil 22. . The acceleration cavity 23 is provided with electron beam transmitting holes 24 and 25 on opposite wall surfaces, and an electron gun 26.

  As in the first embodiment, the electron gun 26 pulses a low-energy electron beam when a voltage pulse generated by a high voltage power source (not shown) that has received a trigger pulse from a trigger pulse oscillator (not shown) is applied. It is designed to output in the form. When the low-energy electron beam output from the electron gun 26 is output from the acceleration cavity 23, the low-energy electron beam circulates by the uniform magnetic field generated by the uniform magnetic field coil 22 and returns to the acceleration cavity 23. As in the first embodiment, a pulsed microwave is supplied to the acceleration cavity 23 from a microwave oscillator 27 that has received a trigger pulse from a trigger pulse oscillator (not shown). The low energy electron beam is accelerated in

  Reference numeral 28 denotes a take-out pipe for taking out a high-energy electron beam accelerated in the uniform magnetic field coil 22. The extraction pipe 28 is configured to shield a uniform magnetic field. The high-energy electron beam taken out from the take-out pipe 28 is transported to the irradiation unit, and is converted into radiation from the irradiation unit to which the high-energy electron beam is transported.

  A correction coil 29 is provided around the acceleration cavity 23. The correction coil 29 constitutes a deflection means for switching whether or not the high energy electron beam is conveyed to the irradiation unit. With this correction coil 29, switching control is performed so that the dose rate of the radiation irradiated from the irradiation unit becomes a desired one.

  Such switching control is performed by a pulsed deflection current as in the first embodiment. Specifically, the correction coil 29 is supplied with a pulsed deflection current from the current source 30. When a pulsed deflection current is applied to the correction coil 29, the high-energy electron beam in the uniform magnetic field is taken out from the take-out pipe 28 as shown by the solid line in the figure, and radiation is emitted from the irradiation unit. Irradiated. On the other hand, when the correction coil 29 is not energized, the high-energy electron beam in the uniform magnetic field collides with the take-out pipe 28 as shown by a one-dot chain line in the figure, and is not taken out from the take-out pipe 28. Yes. Similar to the first embodiment, the current source 30 receives a deflection pulse from a synchronous VF converter (not shown) and outputs the deflection current. As in the first embodiment, the synchronous VF converter receives a trigger pulse from the trigger pulse oscillator, and outputs a deflection pulse having a predetermined repetition frequency corresponding to a predetermined radiation dose rate setting value set in advance. It is designed to output. This radiation dose rate setting value is, for example, as shown in FIG. 2, and also in this example, by changing the repetition frequency of the deflection pulse according to the radiation dose rate setting value as in the first embodiment, The deflection current having the same repetition frequency as the repetition frequency is output to switch between energization and non-energization of the correction coil 29, and the dose rate of radiation irradiated from the irradiation unit can be controlled. .

The operation of the radiotherapy apparatus 20 of this example having the microtron electron accelerator 21 configured as described above will be described.
In the microtron electron accelerator 21 in the radiotherapy apparatus 20 of this example, when a low energy electron beam is output in a pulse form from the electron gun in synchronization with the trigger pulse, the electron beam is guided into the acceleration cavity 23 and accelerated. A circular orbit is drawn in a uniform magnetic field generated by the magnetic field coil 22, and is incident again into the acceleration cavity 23 from the electron beam transmission hole 24. Here, the electrons are further accelerated, exit from the electron beam transmission hole 25 into a uniform magnetic field, draw a larger circular orbit, and enter the acceleration cavity 23 again. This operation is repeated and accelerated until the low energy electron beam reaches a predetermined energy.

  The trajectory of the electron beam in the uniform magnetic field in the uniform magnetic field coil 22 is indicated by a solid line in the figure when a pulsed deflection current is input to the correction coil 29, and is accelerated to a predetermined energy. Thereafter, the high-energy electron beam is taken out from the take-out pipe 28, and the high-energy electron beam is conveyed to the irradiation unit and irradiated with radiation from the irradiation unit. On the other hand, when the deflection current is not input to the acceleration cavity 23, the trajectory of the electron beam in the uniform magnetic field in the uniform magnetic field coil 22 becomes a trajectory indicated by a one-dot chain line in the figure, and the high-energy electron beam is extracted. It collides with the pipe 28 and is not taken out from the take-out pipe 28, and no radiation is emitted from the irradiation section. As in the first embodiment, the correction coil 29 receives a deflection current having a repetition frequency corresponding to the radiation dose rate setting value, whereby the irradiation unit 5 receives a dose rate equal to the radiation dose rate setting value. Of radiation.

  The trigger pulse, low energy electron beam, microwave, deflection pulse, and radiation pulse sequence are the same as those in the first embodiment, and a description thereof will be omitted.

  Also in the radiotherapy apparatus 20 of the present example, the dose rate of the radiation irradiated from the irradiation unit can be changed by changing the repetition frequency of the deflection pulse and the deflection current. Similar effects can be obtained.

The figure which shows 1st embodiment of the radiotherapy apparatus of this invention. The figure which shows the radiation dose rate setting value set to a synchronous VF converter. The pulse sequence figure in the radiotherapy apparatus shown in FIG. The figure which shows the principal part of 2nd embodiment of the radiotherapy apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiotherapy apparatus 2 Electron gun 3 Accelerating tube 4 Bending electromagnet 5 Irradiation part 6 High voltage power supply 7 Trigger pulse oscillator 8 Microwave oscillator 9 Current source 10 Shielding material 11 Synchronous VF converter 20 Radiation therapy apparatus 21 Microtron electron Accelerator 22 Uniform magnetic field coil 23 Acceleration cavity 24, 25 Electron beam transmission hole 26 Electron gun 27 Microwave oscillator 28 Extraction pipe 29 Correction coil 30 Current source

Claims (2)

A radiotherapy apparatus that accelerates an electron beam generated by an electron beam generating means with an accelerating means and conveys the electron beam to an irradiation means, and performs irradiation in the form of an electron beam or radiation from the irradiation means,
A deflecting means for switching whether or not to transport the electron beam accelerated by the accelerating means to the irradiating means;
A radiotherapy apparatus characterized in that the deflection means is switched and controlled so that the dose rate of the electron beam or radiation irradiated from the irradiation means becomes a desired one. The deflection unit includes an electromagnet or a coil, and a pulse current having a repetition frequency corresponding to the desired dose rate is supplied to the electromagnet or the coil to perform the switching control. The radiotherapy apparatus as described.

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