JP4112548B2 - Radiation therapy equipment - Google Patents

Description

  The present invention relates to a radiotherapy apparatus, and more particularly to a radiotherapy apparatus using a collimator as an irradiation field forming means.

The radiation therapy apparatus includes a radiation generation unit and a radiation transport unit, a radiation irradiation unit, an overall control unit, and the like. The radiation generating unit includes an accelerator, a vacuum duct, an electromagnet, a beam monitor, and the like. The radiation irradiating section is composed of an irradiation field expanding section and an irradiation field forming section.
A part of the irradiation field forming device forms a patient collimator for forming an opening corresponding to a different irradiation field for each patient, or an opening corresponding to a necessary irradiation field by controlling a large number of leaves. For this purpose, a multi-leaf collimator is used (for example, see Non-Patent Document 1 and Non-Patent Document 2).

Kazuhiro Ueda, 5 others, "HIMAC treatment and irradiation system", Mitsubishi Electric Technical Report, 1955, Vol. 69, no. 2, p. 34-39 Goshin Sakamoto, 5 others, “HIMAC heavy particle treatment and irradiation equipment”, Mitsubishi Electric Technical Report, 1955, Vol. 69, no. 2, p. 40-44

  The radiotherapy apparatus using the conventional irradiation field forming means as described above is difficult to cope with a large irradiation field. The reason is that it corresponds to an irradiation field having a length of 40 cm and a width of 30 cm. When a patient collimator is used, the size of the patient collimator becomes large, becomes heavy, and is difficult to attach and detach. When using a multi-leaf collimator, it is necessary to increase the number of leaves in order to obtain a sufficient opening, which complicates the drive mechanism, and the drive stroke of the leaf becomes long, making it difficult to control the drive mechanism. Therefore, there is a problem that the apparatus is large and expensive.

What this invention seeks to provide a radiotherapy apparatus that can be obtained with a relatively simple configuration sufficient opening has been made, which corresponds to a large irradiation field in order to solve the aforementioned problems It is.

In the radiotherapy apparatus according to the present invention, the radiation field forming means for setting an opening for forming an irradiation field to the treatment target with respect to radiation from the radiation generating unit is disposed so as to be movable in a predetermined direction. A plurality of irradiation field forming moving members that form a first opening region as a part of a part , and mounted according to a treatment target, adjacent to the first opening region, and used as a treatment target An irradiation field forming replacement member that forms a second opening region having a combined shape is provided, and the opening is formed by the first opening region and the second opening region .

  According to the present invention, it is possible to provide a radiotherapy apparatus capable of obtaining a sufficient opening corresponding to a large irradiation field with a relatively simple configuration.

Embodiment 1 FIG.
A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a plan view showing a configuration of an irradiation field forming unit in the first embodiment. FIG. 1A shows a state before the extension collimator is mounted on the collimator mounting portion, and FIG. 1B shows a state after the extension collimator is mounted on the collimator mounting portion.

The radiotherapy apparatus according to the embodiment of the present invention is composed of a radiation generation unit, a radiation transport unit, a radiation irradiation unit, an overall control unit, and the like as in the prior art as a whole.
The radiation generating unit includes an accelerator, a vacuum duct, an electromagnet, a beam monitor, and the like. The radiation irradiation unit includes an irradiation field expanding unit and an irradiation field forming unit.
In the irradiation field enlargement unit in the radiation irradiation unit, the direction perpendicular to the beam traveling direction and the beam traveling direction are parallel so that the radiation beam transported from the radiation generating unit has a uniform distribution in the affected part of the patient, that is, the target. Adjust the beam divergence angle and range in the direction.
In the irradiation field forming unit in the radiation irradiation unit, the radiation is prevented from reaching the outside of the target by blocking the radiation in the direction perpendicular to the beam.
A multi-leaf collimator is used for the irradiation field forming part. The leaf structure, drive means, and control means for leaf position may be known.

In FIG. 1 showing the planar configuration of the irradiation field forming unit in the first embodiment, the multi-leaf collimator MC that configures the irradiation field forming unit includes a housing frame 1 and an opening 2 and includes a plurality of leaves that shield radiation. The shape of the opening 2 is determined by each position of 3.
The multi-leaf collimator MC is configured by arranging a plurality of elongated strip-shaped leaves 3 having a width of about 1 cm or less, and controls the position of each leaf 3 using a driving device and a control device described in detail later. Thus, the shape of the opening 2 can be freely changed. The maximum aperture of the multileaf collimator is, for example, 15 cm × 15 cm or 20 cm × 15 cm.
If the multi-leaf collimator MC is used, the opening 2 can be matched to the shape of the affected part, so that a patient collimator manufactured for each patient is not necessary.
In the figure, the number of leaves 3 is shown as 20 arranged for convenience, but may actually be larger.

The multi-leaf collimator MC includes a drive unit DP that drives a plurality of leaves 3 and an overall control unit CP that remotely controls the positions of the plurality of leaves 3.
Each of the plurality of leaves 3 is controlled by the overall control unit CP and is individually driven by the drive unit DP. The power of the driving unit DP for driving the leaf 3 such servo motor 4 is used, by a rack and pinion mechanism 5 provided in the drive unit DP, the power of the servo motor 4 is respectively transmitted to the plurality of leaves 3 The

As described above, the servo motor 4 constituting the drive unit DP is controlled by the overall control unit CP through the rack and pinion mechanism 5 so that the plurality of leaves 3 form the opening region 2A.
In addition to controlling the drive unit DP, the overall control unit CP has a control function for the entire radiation therapy apparatus such as a radiation generation unit and a radiation transport unit. The overall control unit CP has an interlock unit IP for ensuring safety, and the generation and transportation of radiation are not permitted except that the position of the leaf 3 and other components of the irradiation device are in a predetermined state. It has the function to do.

Here, the plurality of leaves 3 forming the opening region 2A are driven along the longitudinal direction of the leaves 3 by remote control by the overall control unit CP as in the conventional case.
The plurality of leaves 3 are disposed so as to be movable in a plane orthogonal to the radiation beam emitted from the radiation generating unit radiated in the direction perpendicular to the paper surface in FIG. 2A is formed.

An enlarged portion of the housing frame 1 is provided in a direction perpendicular to the drive direction of the leaf 3, and a mounting portion 1 a for mounting the replaceable extension collimator 6 is provided there.
When a large irradiation field is required, the replaceable extension collimator 6 is manufactured and mounted so as to form an appropriate opening region 2B that can be irradiated with radiation according to the shape of a target as a treatment target such as an affected part. The opening 2 is formed by the opening 2 </ b> A formed by the leaf 3 and the opening 2 </ b> B formed by the exchangeable extension collimator 6.
In the case where the spread of the target to be irradiated is small, it is sufficient to attach a mekura plate instead of the replaceable extension collimator 6 and form the opening 2 only by the opening region 2A formed by the leaf 3.

The interchangeable extension collimator 6 and the housing frame 1 are manufactured with an appropriate material and sufficient thickness, such as iron, tungsten, or lead, in the same way as a multi-leaf collimator using a conventional leaf so as to shield radiation used for irradiation. Shall be.
Radiation leaks through the gap by applying known measures such as creating a step in the gap between the leaf 3 and the exchangeable extension collimator 6 or between the exchangeable extension collimator 6 and the housing frame 1. Provide a means not to
As a mounting method of the exchangeable extension collimator 6, a method of mounting by sliding from the side in the leaf plane and a method of mounting by pressing from a direction perpendicular to the leaf plane can be considered. In the case of the slide method, a rail may be provided on the housing frame 1. In either method, the exchangeable extension collimator 6 is fixed so as not to fall during treatment, such as screwing with a wing nut.

Then, a mounting state detection device including a limit switch LS for detecting a state where the replaceable extension collimator 6 is completely mounted is provided on the housing frame 1.
The output signal of the wearing state detection device by the discrimination operation of the limit switch LS is input to the interlock unit IP of the overall control unit CP provided in the radiotherapy apparatus, and the exchangeable extension collimator 6 is not in a completely worn state. Disallow radiation generation and transport.
As the mounting state detection device, in addition to the limit switch LS, a latch mechanism that operates only when the replaceable extension collimator 6 is completely inserted may be considered.

Further, the housing frame 1 as a housing of the multi-leaf collimator MC is provided with an extended collimator identifying device including an identification function part DA with a pin connector for identifying the replaceable extended collimator 6, and the replaceable type designated in the treatment plan. Confirm that the extension collimator 6 is attached. The exchangeable extension collimator 6 is provided with an identification function part DB with pin connector corresponding to the identification function part DA with pin connector.
As an example of the identification means in the identification function unit DA, it is possible to adopt a mechanism in which the housing side and the exchange collimator side are connected by a multi-pin connector in a state where the exchangeable extension collimator 6 is completely inserted. It is done. The extension collimator side is a male type, and can be identified by creating individual array patterns depending on the presence or absence of pins and detecting a voltage signal applied to the pins. For example, when a digital signal is used for 16 pin connectors and 1 bit is used as a parity bit, 32,768 types of identification numbers can be recognized.
The output signal of the extended collimator identification device by the identification operation executed by the connection of the identification function unit with pin connector DA and the identification function unit DB with pin connector is input to the interlock unit IP of the overall control unit CP provided in the radiation therapy apparatus. If the attached exchangeable extension collimator 6 is other than the desired exchangeable extension collimator 6, the generation and transportation of radiation is not permitted.
The extended collimator identification device is not limited to the above-described configuration, and any configuration can be adopted as long as it is possible to identify whether or not the mounted exchangeable extension collimator 6 is a desired exchangeable extension collimator 6. is there.

Next, the mounting operation of the exchangeable extension collimator 6 will be described.
When the exchangeable extension collimator 6 is mounted, a pair of exchangeable extension collimators 6 and 6 are arranged on the top and bottom of the drawing with an opening region 2A formed by the leaf 3 interposed therebetween in FIG. From the state shown, the replaceable extension collimators 6 and 6 are moved toward the mounting portion 1a provided on the housing frame 1 according to the direction of the arrows in the drawing, and are attached to the mounting portion 1a. When the replaceable extension collimators 6 and 6 are attached to the mounting portion 1a, the state shown in FIG.
In the state shown in FIG. 1B, the opening 2 is formed by the opening 2A formed by the leaf 3 and the opening 2B formed by the exchangeable extension collimator 6 as described above.
In this state, the mounting state detection device including the limit switch LS detects whether or not the replaceable extension collimator 6 is completely mounted.
Further, the extended collimator identification device including the identification function part DA with pin connector and the identification function part DB with pin connector executes an identification operation as to whether or not the attached exchangeable extension collimator 6 is a desired exchangeable extension collimator 6.

In Embodiment 1 according to the present invention, a radiation therapy apparatus with a wide opening can be realized without increasing the number of leaves 3 in the multi-leaf collimator MC, which is suitable for downsizing and cost reduction of the entire apparatus.
Moreover, since the exchange-type extension collimator 6 is lighter than the conventional patient collimator, the operation | work at the time of a treatment becomes easy. In a normal procedure, the patient collimator is mounted after the patient is on the treatment table, so that weight reduction of the parts is also desirable for safety reasons for the patient.
Usually, treatments that require a large irradiation field are mainly for vertically long regions such as the esophagus and spine. As in the configuration according to the present invention, it is desirable that the opening 2 can be wide in a vertically long direction, that is, a direction perpendicular to the leaf drive.
Further, in the first embodiment according to the present invention, a new device called a replaceable extension collimator 6 is required. However, since it may be used or not used by a patient, it can be replaced by adding the above-described wearing state detection function. It is possible to ensure safety against forgetting to remove or forget to attach the mold extension collimator 6.
Further, by adding an extension collimator identification function for identifying the exchangeable extension collimator 6, it is possible to ensure safety against erroneous use of the exchangeable extension collimator 6.

  According to Embodiment 1 of the present invention, there is provided an irradiation field forming means comprising a multileaf collimator MC for setting an opening 2 for forming an irradiation field to the treatment object with respect to radiation from the radiation generating section, The irradiation field forming means including the leaf collimator MC includes an irradiation field forming moving member including a plurality of leaves 3 each of which is movably disposed in a predetermined direction and forms a partial region 2A of the opening 2. And an exchange-type extension collimator 6 which is mounted with an exchange selectively according to the above and forms an opening region 2B adjacent to the opening region 2A formed by the irradiation field forming moving member composed of the plurality of leaves 3. Since the irradiation field forming replacement member is provided, it is possible to provide a radiotherapy apparatus that can obtain a sufficient opening corresponding to a large irradiation field with a relatively simple configuration.

  According to Embodiment 1 of the present invention, in the configuration of the preceding paragraph, the irradiation field forming moving member composed of the plurality of leaves 3 along the movement path of the irradiation field forming moving member composed of the plurality of leaves 3. Corresponding to the opening region 2A to be formed, there is provided a replacement member mounting portion consisting of a mounting portion 1a provided in a housing frame 1 for mounting a radiation field forming replacement member consisting of the extension collimator 6, and the replacement type extension collimator. Since the irradiation field forming replacement member made up of 6 is mounted on the replacement member mounting portion made up of the mounting member 1a from the direction perpendicular to the movement path of the irradiation field forming moving member made up of the plurality of leaves 3, the irradiation field With the irradiation field forming replacement member mounted from the direction perpendicular to the moving path of the forming moving member, a sufficient opening corresponding to a large irradiation field can be obtained with a relatively simple configuration. It is possible to provide a ray treatment apparatus.

  Furthermore, according to Embodiment 1 of the present invention, in any one of the configurations of the preceding two paragraphs, an irradiation field forming replacement member comprising the extended collimator 6 mounted on the replacement member mounting portion including the mounting member 1a is provided. An exchange member discriminating means constituted by an extended collimator identifying device comprising an identification function part DA with a pin connector for discriminating whether or not it is suitable for the treatment object, and an exchange member discriminating means constituted by the extended collimator identifying device When it is determined that the irradiation field forming replacement member composed of the replaceable extension collimator 6 is not suitable for the treatment target, the interlock provided in the overall control unit CP for blocking the irradiation of the treatment target is provided. Since the radiation blocking means comprising the part IP is provided, a sufficient opening corresponding to a large irradiation field can be obtained with a relatively simple configuration. Preparative it is, it is possible to provide a radiotherapy apparatus which can ensure preventing safety erroneous mounting of the irradiation field forming exchange member.

  And according to Embodiment 1 by this invention, the mounting state of the irradiation field formation exchange member which consists of the said extension collimator 6 in the exchange member mounting part which consists of the said attachment member 1a in the structure of any one of 3 preceding clauses The interchangeable extension collimator 6 is configured by a mounting state determination unit configured by a mounting state detection device including a limit switch LS that determines whether or not is appropriate, and a mounting state determination unit configured by the mounting state detection device. Since it is determined that the wearing state of the irradiation field forming replacement member is not appropriate, radiation blocking means including an interlock unit IP provided in the overall control unit CP for blocking irradiation of radiation to the treatment target is provided. A sufficient opening corresponding to a large irradiation field can be obtained with a relatively simple configuration, and the abnormal mounting state of the irradiation field forming replacement member Preventing it is possible to provide a radiotherapy apparatus which can ensure safety.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a perspective view showing a configuration in the second embodiment.
In the second embodiment, the configuration other than the specific configuration described here has the same configuration as the configuration in the first embodiment described above, and has the same function. In the drawings, the same reference numerals indicate the same or corresponding parts.

In FIG. 2 showing the configuration in the second embodiment, it is assumed that an auxiliary collimator 7 is provided upstream of the multi-leaf collimator CM in the first embodiment shown in FIG. 1, and the opening degree of the auxiliary collimator 7 can be remotely controlled.
The auxiliary collimator 7 is composed of two pairs of collimator members 7a, 7b and 7c, 7d, and these collimator members 7a, 7b and 7c, 7d are made of iron, tungsten, aluminum, lead, etc. in order to shield radiation used for irradiation. It shall be manufactured with appropriate materials and sufficient thickness.
Of the four collimator members 7a, 7b and 7c, 7d of the auxiliary collimator 7, one pair of collimator members 7c, 7d can be driven remotely from the overall control unit CP (FIG. 1), as shown in FIG. In a plane perpendicular to the radiation beam path BP from the beam light source BS constituting the radiation generating unit, the direction perpendicular to the driving direction of the leaf 3, that is, the direction in which the exchangeable extension collimator 6 is mounted on the mounting unit 1a, By enabling the collimator members 7c and 7d to be driven, the degree of opening at the opening 7A of the auxiliary collimator 7 can be adjusted in accordance with the exchangeable extension collimator 6.
That is, in the case where a Mekura plate is used instead of the exchangeable extension collimator 6, that is, when the size of the target as a treatment target is relatively small and is sufficient in the opening forming range by the movement of the leaf 3, the opening by the leaf 3 is used. The auxiliary collimator 7 is closed to an intermediate position so that no radiation is applied to areas other than the area.
When the target as a treatment target is large and the additional extension collimator 6 is used to form an additional opening, the collimator members 7c and 7d are moved to open the auxiliary collimator 7 to the maximum opening position.

  In the multi-leaf collimator MC in which the opening 2 (see FIG. 1) is formed by the leaf 3 and the exchangeable extension collimator 6, the same situation as when the opening 2 is completely blocked is created and the radiation does not reach the treatment target. If necessary, the collimator members 7c and 7d facing each other through the opening 7A are moved from the state shown in FIG. 2 toward each other to completely close the opening 7A. Radiation from the beam light source BS is completely blocked by the auxiliary collimator 7 composed of the collimator members 7a, 7b and 7c, 7d.

In general, in radiation therapy, it may be necessary to create a fully closed state in which radiation does not reach the patient, such as performing a final confirmation of the irradiation beam axis during the treatment procedure. In the conventional treatment apparatus using the multi-leaf collimator, the fully closed state can be created by closing the leaf 3 of the multi-leaf collimator. However, when the extended collimator 6 is used, the fully closed state can be created. Can not.
According to Embodiment 2 of the present invention, by closing the auxiliary collimator 7, the same fully closed state as that of closing the leaf of the conventional treatment apparatus using the multi-leaf collimator can be created. In addition, even when the leaf 3 of the multileaf collimator CM is installed at a treatment position that matches the target shape and the fully closed state is created after the opening shape is confirmed, the leaf 3 of the multileaf collimator CM is not moved. Since it can be made, the control procedure can be rationalized, and erroneous setting due to re-setting of the leaf 3 can be avoided, and the certainty of treatment can be improved.

In FIG. 2, the treatment beam is shown as a point light source BS for the sake of convenience, but the same principle can be applied even when the beam is not a point light source, for example, a parallel beam.
Here, as the auxiliary collimator 7, a configuration including two pairs of collimator members 7 a, 7 b and 7 c, 7 d is described for convenience, but the configuration of the auxiliary collimator 7 may be configured by a pair of collimator members 7 c, 7 d.
The pair of collimator members 7c and 7d of the auxiliary collimator 7 can be driven remotely, and the drive direction is the direction perpendicular to the drive direction of the leaf 3 of the multi-leaf collimator MC, but the drive direction of the collimator members 7c and 7d May be parallel to the drive direction of the leaf 3 of the multi-leaf collimator MC, or may not be a specific direction as long as it moves in a plane orthogonal to the radiation beam path BP from the beam light source BS.

  In the second embodiment, an auxiliary collimator 7 is provided upstream of the multi-leaf collimator MC in the first embodiment to shield radiation in the direction parallel to and perpendicular to the driving of the leaf 3, and the multi-leaf collimator MC. The area around the opening 2 is shielded and the opening 7A of the auxiliary collimator 7 is made variable by remote operation, so that the fully-closed state that blocks radiation can be remotely operated even when the exchangeable extension collimator 6 is not remotely driven. A radiotherapy apparatus characterized in that it can be made is configured.

  According to the second embodiment of the present invention, in the configuration in the first embodiment, the radiation shielding moving member including the collimator members 7c and 7d arranged to be movable in a predetermined direction is provided, and the radiation shielding movement is performed. Due to the movement of the member collimator members 7c and 7d in a predetermined direction, the multi-leaf collimator MC includes a plurality of irradiation field forming moving members including a plurality of leaves 3 and an irradiation field forming replacement member including a replaceable extension collimator. Since the radiation shielding means for stopping the radiation irradiation by the opening regions 2, 2 a, 2 b to be formed is provided, a sufficient opening corresponding to a large irradiation field can be obtained with a relatively simple structure, and the radiation irradiation It is possible to provide a radiotherapy apparatus that can appropriately perform restraint.

Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a side view showing the configuration of the third embodiment.
In the third embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configuration in the second embodiment described above, and exhibits the same operation. In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 3 showing the configuration in the third embodiment shows a configuration for selectively moving the collimator members 7c and 7d in the second embodiment shown in FIG. 2 to a predetermined position.
The collimator members 7c and 7d are configured to be selectively movable to the first predetermined position P1 and the second predetermined position P2.
When the collimator members 7c and 7d are located at the first predetermined position P1, the radiation emitted from the beam light source BS is shielded by the exchangeable extension collimator 6, and the radiation from the beam light source BS toward the plurality of leaves 3 is emitted. Is irradiated.
When the collimator members 7c and 7d are located at the second predetermined position P2, the radiation that is irradiated from the beam light source BS to the interchangeable extension collimator 6 is not shielded, and the plurality of leaves 3 and the interchangeable extension collimator 6 are directed to. Radiation is emitted from the beam light source BS.

Here, for a small irradiation field that does not require the replaceable extension collimator 6, as shown in FIG. 3, the collimator members 7c and 7d are moved to the first predetermined position P1, and the opening of the auxiliary collimator 7 is moved. By partially closing, the peripheral region can be shielded by the auxiliary collimator 7.
As a result, the mecha plate inserted into the place of the exchangeable extension collimator 6 can be omitted, and the exchangeable extension collimator 6 can be easily replaced.

  In the third embodiment, an auxiliary collimator 7 is provided upstream of the multi-leaf collimator MC shown in the second embodiment for shielding radiation in the direction parallel to and perpendicular to the driving of the leaf 3. By shielding the peripheral area of the opening 2 and making the opening 7A of the auxiliary collimator 7 variable by remote control, the auxiliary collimator 7 is partially closed in the case of a small irradiation field that does not use the replaceable extension collimator 6. The radiation reaching the part of the exchangeable extension collimator 6 can be blocked by this, and a mech plate or the like is not used at the opening of the exchangeable extension collimator 6, or a small area of the extension opening region 2B is partially removed. A radiotherapy apparatus characterized by shielding with a plate or the like is configured.

  According to the third embodiment of the present invention, in the configuration of the second embodiment, the radiation shielding moving member including the collimator members 7c and 7d arranged to be movable in a predetermined direction is provided, and the collimator member 7c, Radiation shielding comprising an auxiliary collimator 7 for stopping radiation irradiation by the opening region 2B formed by the irradiation field forming exchange member comprising the exchangeable extension collimator 6 by movement of the radiation shielding moving member comprising 7d in a predetermined direction. And a selection position for stopping the radiation irradiation by the opening region 2 </ b> B formed by the irradiation field forming exchange member made of the exchangeable extension collimator and the radiation shielding moving member made of the collimator members 7 c and 7 d. The first movement position indicated by P1 and a plurality of irradiation field forming transfers composed of the plurality of leaves 3 It is possible to selectively move to the second movement position indicated by the selection position P2 that enables radiation irradiation by the opening regions 2A and 2B formed by the irradiation field forming replacement member including the member and the exchangeable extension collimator 6. Since it did in this way, while being able to obtain sufficient opening corresponding to a large irradiation field with a comparatively simple structure, the radiotherapy apparatus which can control radiation irradiation appropriately and accurately can be provided.

It is a top view which shows the structure in Embodiment 1 by this invention. It is a perspective view which shows the structure in Embodiment 2 by this invention. It is a side view which shows the structure in Embodiment 3 by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case frame, 2 opening part, 3 leaf, 4 servo motor, 5 rack and pinion mechanism, 6 exchange type extension collimator, 7 auxiliary collimator, MC multileaf collimator, BS beam light source.

Claims (6)

Irradiation field forming means for setting an opening for forming an irradiation field to the treatment target with respect to radiation from the radiation generation unit is provided, and each of the irradiation field forming means is disposed so as to be movable in a predetermined direction. A plurality of irradiation field forming moving members that form a first opening region as a part of a part , and mounted according to a treatment target, adjacent to the first opening region, and used as a treatment target An irradiation field forming replacement member for forming a second opening region having a combined shape is provided, and the opening is formed by the first opening region and the second opening region. Radiotherapy device. Replacing member mounting for mounting the irradiation field forming replacement member corresponding to the first opening region formed by the plurality of irradiation field forming moving members along the movement path of the plurality of irradiation field forming moving members 2. The radiotherapy apparatus according to claim 1, wherein the radiation field forming replacement member is mounted on the replacement member mounting portion from a direction perpendicular to a movement path of the plurality of irradiation field forming moving members. . An exchange member discriminating means for discriminating whether or not the irradiation field forming exchange member attached to the exchange member attaching portion is suitable for the treatment target, and the irradiation field forming exchange member by the exchange member discriminating means. The radiotherapy apparatus according to claim 2 , further comprising: a radiation blocking unit configured to block irradiation of radiation to the treatment target when it is determined that is not suitable for the treatment target. A mounting state determining means for determining whether or not the mounting state of the irradiation field forming replacement member to the replacement member mounting portion is appropriate, and the mounting state of the irradiation field forming replacement member is appropriate by the mounting state determining means The radiotherapy apparatus according to claim 2 , further comprising: a radiation blocking unit that blocks radiation of the treatment target when it is determined that the target is not. A radiation shielding moving member arranged to be movable in a predetermined direction on a plane orthogonal to a radiation path from the radiation generating unit, and the plurality of irradiation fields by moving the radiation shielding moving member in the predetermined direction; claims, characterized in that a first radiation shielding means for restraining the radiation by the opening formed by the second opening region of the opening area and the irradiation replacement member forming the moving member The radiotherapy apparatus in any one of Claim 1 to 4. A radiation shielding moving member arranged to be movable in a predetermined direction on a plane orthogonal to the radiation path from the radiation generating unit, and for the irradiation field forming by moving the radiation shielding moving member in the predetermined direction; A radiation shielding means for stopping radiation irradiation by the second opening area formed by the exchange member is provided, and the radiation shielding moving member is formed by the second opening area formed by the irradiation field forming exchange member. first and movement position to restrain the irradiation by the opening formed by the second opening region of the first opening region and the irradiation replacement member of the plurality of irradiation field forming the moving member The radiotherapy apparatus according to any one of claims 1 to 5, wherein the radiotherapy apparatus can selectively move to a second movement position that enables irradiation by radiation.

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