Therapeutic device and a method of driving the therapeutic device

The present application is based on and claims priority to Japanese Patent Application No. JP 2016-175778, filed Sep. 8, 2016, the entire contents of which are incorporated herein by reference.

Embodiments relate to a particle beam therapy device with a gantry and methods of operating the device.

One of the ways to treat a patient's cancer is by irradiating an affected area including the cancer with a particle beam. Such treatment may be performed by a therapeutic device including a particle beam irradiation device. The therapeutic device includes a cylindrical gantry having a pedestal in its inner space and a particle beam irradiation device fixed in the inner wall of the gantry. The inside of the gantry includes a treatment room. A patient lies on the pedestal. The particle beam irradiation device moves around the patient by the gantry rotating and the patient's cancer is irradiated with the particle beam. The desired position and focus of the particle beam is adjusted by rotating the gantry and by moving the position of the pedestal.

It is desired that the floor of the treatment room should always remain flat in the cylindrical gantry so that the patient may remain calm, and so that health care workers can conveniently access the patient inside of the gantry.

Present embodiments disclose a therapeutic device including a cylindrical gantry having an inner space and an inner surface, a pedestal disposed in the inner space, a particle beam irradiation device disposed in the inner surface and being configured to emit a particle beam toward the pedestal, a first rail disposed in the gantry and comprising a first arc-shaped portion and a first straight portion, ends of the first arc-shaped portion being connected to respective ends of the first straight portion, a second rail disposed in the gantry and comprising a second arc shaped portion and a second straight portion, ends of the second arc-shaped portion being connected to respective ends of the second straight portion, the second arc-shaped portion extending along an inner periphery of the gantry, a rail motor attached to the second rail and being configured to rotate the second rail in a direction opposite to a rotation direction of the gantry, a first moving floor disposed on the first rail and on the second rail, and comprising a plurality of first floor panels rotatably connected to each other, and a second moving floor disposed on the first rail and on the second rail, and comprising a plurality of second floor panels rotatably connected to each other, wherein a first end panel of the first moving floor is detachably connected to the particle beam irradiation device, the second end panel of the first moving floor is detachably connected to a third end panel of the second moving floor, and a fourth end panel of the second moving floor is detachably connected to the particle beam irradiation device.

Present embodiments disclose a method of operating the therapeutic device including positioning the first moving floor and the second moving floor so as to not contact the particle beam irradiation device, rotating the gantry in the rotation direction, rotating the second rail in the direction opposite to the rotation direction of the gantry during the rotating of the gantry, moving at least one of the first moving floor and the second moving floor on the first rail while maintaining a predetermined distance from the particle beam irradiation device during or after the rotating of the gantry, and further moving at least one of the first moving floor and the second moving floor after the rotating of the gantry.

Present embodiments disclose a method of operating the therapeutic device including positioning the first moving floor and the second moving floor so as to not contact the particle beam irradiation device, rotating the gantry in the rotation direction, rotating the second rail in the direction opposite to the rotation direction of the gantry during the rotating of the gantry, moving at least one of the first moving floor and the second moving floor on the first rail while maintaining a predetermined distance from the particle beam irradiation device during or after the rotating of the gantry and further moving at least one of the first moving floor and the second moving floor after the rotating of the gantry, wherein the further moving of said at least one of the first moving floor and the second moving floor are controlled by the first detector and the second detector.

A more complete appreciation of the disclosed embodiments and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic sectional view of a therapeutic device according to an embodiment;

FIG. 2 is a perspective view of a portion of the therapeutic device of FIG. 1 , according to an embodiment;

FIG. 3 is a schematic sectional view of the therapeutic device of FIG. 1 , taken along line I-I and depicting a gantry rotation angle of 180°, according to an embodiment;

FIG. 4 is a schematic sectional view of the therapeutic device of FIG. 1 , taken along line I-I and depicting a gantry rotation angle of 135°, according to an embodiment;

FIG. 5 is a schematic sectional view of the therapeutic device of FIG. 1 , taken along line I-I and depicting a gantry rotation angle of 90°, according to an embodiment;

FIG. 6 is a schematic sectional view of the therapeutic device of FIG. 1 , taken along line I-I and depicting a gantry rotation angle of 0°, according to an embodiment; and

FIG. 7 is a schematic sectional view of the therapeutic device of FIG. 1 , taken along line I-I and depicting a gantry rotation angle of −180°, according to an embodiment.

Hereafter, embodiments are described with reference to the drawings. An overview of a particle beam therapy device is described with reference to FIGS. 1-7 . FIG. 2 is a perspective view of a portion of the therapeutic device of FIG. 1 , showing moving floors according to an embodiment. FIGS. 3-7 are schematic sectional views of the therapeutic device of FIG. 1 , taken along line I-I and depicting various gantry rotation angles, according to an embodiment.

The particle beam therapeutic device shown in FIGS. 1-7 may irradiate a portion of the patient on the pedestal with a particle beam oriented in any direction. The particle beam therapeutic device 10 includes a pedestal 12 , a gantry 11 , a particle beam irradiation device 13 , first and second rails 14 A, 14 B, and first and second moving floors 15 A, 15 B.

The gantry 11 is cylindrical and the central axis of the gantry 11 is horizontal relative to a floor of the room where the gantry 11 is disposed. End rings 18 are attached to both the ends of the gantry 11 . Supporting rollers 17 contact the end rings 18 . The gantry 11 is supported by supporting roller 17 through the end rings 18 . The supporting rollers 17 are derived by supporting roller motor 20 . The supporting roller motor 20 drives the supporting rollers 17 and the gantry 11 rotates around its central axis.

The pedestal 12 is fixed on a platform 19 holding the gantry 11 . The pedestal 12 does not rotate with the gantry 11 . Patient 1 can lie on the pedestal 12 . The pedestal 12 is movable in directions parallel to the central axis of the gantry 11 . For example, pedestal 12 may move into gantry 11 or out from gantry 11 .

The particle beam irradiation device 13 is provided on the inner wall of the gantry 11 . The particle beam irradiation device 13 rotates with the gantry 11 . The gantry 11 rotates from 180° to −180° around the central axis. The particle beam irradiation device 13 includes an irradiation opening 13 A. A particle beam may be emitted from the irradiation opening 13 A. Rotating the gantry 11 causes the particle beam irradiation device 13 to rotate around the patient 1 on the pedestal 12 , and a portion of the patient may be irradiated with the particle beam from any direction in 360° around the pedestal. As shown in FIGS. 3-7 , junction 13 B represents points where the particle beam irradiation device 13 is fixed on the inner wall of the gantry 11 .

The pedestal 12 is also in the treatment room 30 and is movable into and out of the gantry 11 . The treatment room 30 includes the first and the second moving floors 15 A, 15 B. The first and the second moving floors 15 A, 15 B each include a plurality of floor panels 25 connected each other. For example, the floor panels 25 are connected to each other with hinges. Each floor panel 25 can pivot at the hinge connecting it to another floor panel 25 . Each floor panel 25 is rectangular, with a long side thereof being oriented parallel to the central axis of the gantry 11 . The floor panels 25 are connected to each other along the long sides thereof. The first and the second moving floors 15 A, 15 B therefore behave as a single plate and can bend due to the connected floor panels 25 .

Each of the first moving floor 15 A and the second moving floor 15 B is provided on the first rail 14 A and on the second rail 14 B, and moves on the first rail 14 A and the second rail 14 B. The shape of the first rail 14 A includes an arc-shaped portion 21 and a straight portion 22 , ends of the arc-shaped portion being smoothly connected to respective ends of the straight portion. Similarly, the shape of the second rail 14 B includes an arc-shaped portion 21 and a straight portion 22 , ends of the arc-shaped portion being smoothly connected to respective ends of the straight portion.

The first rail 14 A is provided at an end of the gantry 11 . The first rail 14 A is fixed on the platform 19 holding the gantry 11 . The straight portion 22 of the first rail 14 A is horizontal relative to the floor of treatment room 30 and is located in a lower portion of the interior of the gantry 11 . The arc-shaped portion 21 is located along an inner periphery of the gantry 11 above the straight portion 22 . The first rail 14 A does not rotate.

The second rail 14 B is provided at the other end of the gantry 11 . The second rail 14 B is held in the gantry 11 by a rail supporting member 23 . The second rail 14 B is rotated by a rail rotating motor 24 . For example, the rail supporting member 23 and the rail rotating motor 24 are provided on the inner side of the gantry 11 . The rail rotating motor 24 rotates the second rail 14 B. The rotation of the second rail 14 B is synchronized with the rotation of gantry 11 and may be counterclockwise relative to the clockwise rotation of the gantry 11 . Such rotation of the second rail 14 B keeps the straight portion 22 of the second rail 14 B horizontal and at a lower position than the arc-shaped portion 21 . The first rail 14 A and the second rail 14 B are stationary regardless of the rotation of the gantry 11 .

A back panel 28 is provided on the second rail 14 B. The back panel 28 is disposed in a plane that is perpendicular to the central axis of the gantry 11 . On the first rail 14 A, a total length of the first moving floor 15 A and the second moving floor 15 B is longer than a length of the straight portion 22 . The particle beam irradiation device 13 is disposed between the first moving floor 15 A and the second moving floor 15 B. A total length of the first moving floor 15 A, the particle beam irradiation device 13 , and the second moving floor 15 B is shorter than a length of the circumference of the first rail 14 A.

In the treatment room 30 , the first moving floor 15 A, the second moving floor 15 B, a part of inner surface of the gantry 11 , and the back panel 28 are disposed. A cross section of the treatment room 30 perpendicular to the central axis of the gantry 11 consists of an arc-shaped part and a straight part connected smoothly at both ends thereof.

In the treatment room 30 , there is a flat and a horizontal floor composed by the first moving floor 15 A and/or the second moving floor 15 B. The flat part of the moving floors 15 A, 15 B in the treatment room 30 is called flat floor 27 . In the treatment room 30 , the arc-shaped part composed by the first and second moving floors 15 A, 15 B, or the first and second moving floors 15 A, 15 B, and the inner surface of the gantry is called arc wall 26 . The first moving floor 15 A and the second moving floor 15 B are rigid enough to support several people who may be, for example, a patient, an engineer of the therapeutic device, and a doctor.

The first and the second moving floors 15 A, 15 B move on the first and second rails 14 A, 14 B by floor motors 16 . For example, the floor motors 16 are provided on the both ends of each of the first and second moving floors 15 A, 15 B. More than two floor motors 16 may be provided on one of the moving floors.

Hereinafter, the operation of the therapeutic device 10 is described. As shown in FIG. 3 , for example, particle beam irradiation device 13 is movable by the gantry 11 rotating around the patient 1 on the pedestal 12 . Before the gantry rotates, people on the moving floor exit the treatment room 30 for safety. The patient 1 may remain on the pedestal 12 before and during the gantry rotating. Also, before the gantry rotating, the first moving floor 15 A and the second moving floor 15 B move to positions where the moving floors 15 A, 15 B do not contact the particle beam irradiation device 13 that is going to move. The first moving floor 15 A and the second moving floor 15 B are moved by the floor motors 16 .

During rotation of the gantry 11 , the moving floors 15 A, 14 B respectively maintain positions where the moving floors 15 A, 15 B do not contact the particle beam irradiation device 13 , which is also moving. Also, for example, during the rotation of the gantry, the moving floors 15 A, 15 B may move while maintaining a predetermined distance from the particle beam irradiation device 13 .

After the gantry 11 has stopped rotating, the first moving floor 15 A continues moving so as to contact its end with the particle beam irradiation device 13 . And, the second moving floor 14 B moves to contact its end with the particle beam irradiation device 13 , also after the gantry 11 has stopped rotating. Moving of the first moving floor 15 A and the second moving floor 15 B is controlled according to movement of the particle beam irradiation device 13 in a predetermined sequence. Or, moving of the first moving floor 15 A and the second moving floor 14 B is controlled by an operator observing positions of the moving floors 15 A, 15 B and of the particle beam irradiation device 13 .

As shown in FIG. 3 , the floor motors 16 may be attached on both ends of the first moving floor 15 A and on both ends of the second moving floor 15 B. The end floor panel 25 of the first moving floor 15 A that is closest to the particle beam irradiation device 13 is the first end panel 29 A. The end floor panel 25 of the first moving floor 15 A that is closest to the second moving floor 15 B is the second end panel 29 B. The end floor panel 25 of the second moving floor 15 B that is closest to the first moving floor 15 A is the third end panel 31 B. The end floor panel 25 of the second moving floor 15 B that is closest to the particle beam irradiation device 13 is the fourth end panel 31 A.

The operation of the each floor motor 16 is not limited. For example, when the moving floors 15 A, 15 B are moved upward, the floor motors 16 on the second end panel 29 B and on the third end panel 31 B are the main drivers of the movement of the moving floors 15 A, 15 B, and the floor motors 16 on the first end panel 29 A and the fourth end panel 31 A are the supplemental drivers. Or, when the moving floors are moved upward, the floor motors 16 on the first end panel 29 A and the fourth end panel 31 A are the main drivers, and the floor motors 16 on the second end panel 29 B and the third end panel 31 B are the supplemental drivers. Or, the driving power of the floor motors 16 on the second end panel 29 B, the third end panel 31 B, the first end panel 29 A, and the fourth end panel 31 A may be linked together.

When the moving floors 15 A, 15 B are moved in a direction such that the second end panel 29 B and the third end panel 31 B are moved downward, closer to the floor where the gantry 11 is disposed, the floor motors 16 on the first end panel 29 A and the fourth end panel 31 A are the main drivers, and the floor motors 16 on the second end panel 29 B and the third end panel 31 B are the supplemental drivers. Or, when the moving floors are moved downward, the floor motors 16 on the second end panel 29 B and the third end panel 31 B are the main drivers, and the floor motors 16 on the second end panel 29 B and the third end panel 31 B are the supplemental drivers. Or, the driving power of the floor motors 16 on the second end panel 29 B, the third end panel 31 B, the first end panel 29 A, and the fourth end panel 31 A may be linked together.

For reasons of safety, when a person, for example a health care worker, is in the treatment room 30 , the flat floor 27 is needed to be flat and have no clearance between it and the particular beam irradiation device 13 , regardless the position of the particle beam irradiation device 13 . And, when the particle beam irradiation device 13 is in the straight portion 22 of flat floor 27 , contact points of the irradiation device 13 and the moving floors 15 A, 15 B (i.e., the end of the first end panel 29 A, and of the fourth end panel 31 A) change according to the rotation angle of the gantry. The relationship between the rotation angle of the gantry 11 and the position of the particle beam irradiation device 13 is described below. Also, the operation of the particle beam irradiation device 13 (or the gantry 11 ) and the moving floors 15 A, 15 B are described below.

For example, as shown in FIG. 3 , the particle beam irradiation device 13 is in a position underneath the pedestal 12 , when the rotation angle of the gantry 11 is at +180°. The particle beam irradiation device 13 is in the flat floor 27 . The end of the first end panel 29 A and the end of the fourth end panel 31 A are in contact with the particle beam irradiation device 13 . In a moving direction of the moving floors 15 A, 15 B, there is no clearance in the flat floor 27 , such that it would not be possible to drop an object, such as a tool, or to allow passage of a person's hand or foot, under the moving floors 15 A, 15 B.

As shown in FIG. 4 , the particle beam irradiation device 13 is at a lower diagonal corner position of the pedestal 12 , when the rotation angle of the gantry 11 is at +135°. The particle beam irradiation device 13 is still in the flat floor 27 and the length of the flat floor to the left of the particle beam irradiation device 13 is longer than it was when the rotation angle of the gantry 11 is +180°. The position occupied by the particle beam irradiation device 13 and the contact points of the particle beam irradiation device 13 and the moving floors 15 A, 15 B have changed due to the rotation angle of the gantry 11 , but still there is no clearance in the flat floor 27 . This is because the moving floors move on the rails after the rotation of the gantry stops in order to contact the end the first end panel 29 A and the end the fourth end panel 31 A with the particle beam irradiation device 13 .

An example of the operation of the gantry rotating from +180° to +135° is described below. The gantry 11 is depicted as rotating in a counterclockwise direction from FIG. 3 to FIG. 4 . Before starting the rotation operation, the gantry is at +180° and the particle beam irradiation device 13 is positioned vertically under the pedestal 12 . The ends of the first end panel 29 A and of the fourth end panel 31 A are in contact with the particle beam irradiation device 13 . To begin the operation, the second moving floor 15 B first moves counterclockwise on the rails to where the end the fourth end panel 31 A does not contact the particle beam irradiation device 13 when the gantry is +135°. Second, the gantry rotates to +135°. Then, the first moving floor 15 A and the second moving floor 15 B move on the rails to contact the ends of the first end panel 29 A and of the fourth end panel 31 A with the particle beam irradiation device 13 .

In another example, the second moving floor 15 B moves counterclockwise on the rails to provide a predetermined distance separating the end of the fourth end panel 31 A and the particle beam irradiation device 13 . This distance may be shorter than the distance to which the particle beam irradiation device 13 will move by the gantry 11 rotating from +180° to +135°. Then, the particle beam irradiation device 13 and the second moving floor 15 B move at the same speed to maintain the predetermined distance until the gantry is at +135°. Finally, the first moving floor 15 A and the second moving floor 15 B move on the rails to contact the ends of the first end panel 29 A and of the fourth end panel 31 A with the particle beam irradiation device 13 .

As shown in FIG. 5 , the particle beam irradiation device 13 is at a position that is the same height as the pedestal 12 , when rotation angle of the gantry 11 is at +90°. The particle beam irradiation device 13 is now along the arc wall 26 . There is no clearance in the flat floor 27 because the particle beam irradiation device 13 is no longer disposed in a portion occupied by the flat floor 27 . The moving floors 15 A, 15 B move on the rails after the rotation of the gantry to cover the straight portion 22 with the first moving floor 15 A. When the particle beam irradiation device 13 is positioned along the arc wall 26 , the contact points 13 B of the particle beam irradiation device 13 and moving floors 15 A, 15 B are stable.

An example of an operation to move the particle beam irradiation device 13 from +135° to +90° is described below. The gantry 11 is depicted as rotating in a counterclockwise direction from FIG. 4 to FIG. 5 . Before starting the operation, the gantry is at +135°. The ends the first end panel 29 A and of the fourth end panel 31 A are in contact with the particle beam irradiation device 13 . First, the second moving floor 15 B moves counterclockwise on the rails to where the end of the fourth end panel 31 A does not contact the particle beam irradiation device 13 when the gantry is at +90°. Second, the gantry rotates to +90°. Then, the first moving floor 15 A moves on the rails to cover the straight portion 22 and to contact the end of the first end panel 29 A with the particle beam irradiation device 13 . At the same time, the second moving floor 15 B moves on the rail to contact the end of the fourth end panel 31 A with the particle beam irradiation device 13 . When the gantry is at +90°, there is no clearance in the flat floor 27 because the particle beam irradiation device 13 is no longer disposed in a portion occupied by the flat floor 27 . So, the ends of the first end panel 29 A and of the fourth end panel 31 A may or may not be in contact with the particle beam irradiation device 13 .

In FIG. 2 and in FIG. 6 , the particle beam irradiation device 13 is in a position directly above the pedestal 12 , when rotation angle of the gantry 11 is at 0°. The particle beam irradiation device 13 is positioned along the arc wall 26 . And, there is no clearance in the flat floor 27 because after the rotation of the gantry the moving floors 15 A, 15 B move on the rails 14 A, 14 B to cover the straight portion 22 with floor panels 25 . The end of the third end panel 31 B contacts the end of the second end panel 29 B in the straight portion 22 . There is a clearance between the end of the fourth end panel 31 A and the particle beam irradiation device 13 , and between the end of the first end panel 29 A and the particle beam irradiation device 13 .

An example of an operation to move the particle beam irradiation device 13 from +90° to 0° is described below. The gantry 11 is depicted as rotating in a counterclockwise direction from FIG. 5 to FIG. 6 . First, the second moving floor 15 B moves counterclockwise on the rails to provide a predetermined distance between the end of the fourth end panel 31 A and the particle beam irradiation device 13 . This distance may be shorter than the distance to which the particle beam irradiation device 13 will move by the gantry 11 rotating from +90° to 0°. Then, the particle beam irradiation device 13 , the second moving floor 15 B, and the first moving floor 15 A move at the same speed to maintain the predetermined distance until the gantry is at 0°. Finally, the first moving floor 15 A and the second moving floor 15 B move on the rails to contact the ends of the second end panel 29 B and of the third end panel 31 B in the straight portion to form flat floor 27 without clearance therebetween.

As described above, when the particle beam irradiation device 13 is positioned along the arc wall 26 , the moving floors 15 A, 15 B move on the rails 14 A, 15 B to cover the straight portion 22 without any clearance therebetween. When the particle beam irradiation device 13 is positioned in the flat floor 27 , the rotation angle of the gantry 11 is ˜+135° to ˜+180°, and the moving floors 15 A, 15 B move on the rails 14 A, 15 B to contact the first end panel 29 A and the third end panel 31 B with the particle beam irradiation device 13 , in order to not create any clearance in the flat floor 27 .

As described above, the relationships of rotation angle of the gantry 11 and position of the particle beam irradiation device 13 are examples. According to the lengths of the arc shaped portion 21 and of the straight portion 22 , the relationship of rotation angle of the gantry 11 and position of the particle beam irradiation device 13 is changed. As described above, the gantry 11 rotates from ˜+180° to ˜0°. But the gantry 11 may also rotate from ˜0° to ˜−180°. The ˜+180° and 0° positions of the gantry 11 and the particle beam irradiation device 13 appear the same. When the gantry 11 rotates from ˜0° to ˜−180°, there is no clearance in the flat floor 27 due to the contact between the ends of the fourth end panel 31 A and of the first end panel 29 A with the particle beam irradiation device 13 , or due to the contact between the end of the third end panel 31 B the end of the second end panel 29 B.

The therapeutic device 10 as described above is efficient. For safety reasons, the irradiation device 13 needs to be in contact with the flat floor 27 so as to have no clearance between the irradiation device 13 and the flat floor 27 . However, during the gantry 11 rotation from ˜+180° to ˜+135° (or from ˜−135° to ˜−180°, the angle of the irradiation device 13 against the straight portion 22 (of flat floor 27 ) changes according to the rotation angle of the gantry. So, the contact points of the irradiation device 13 and the moving floors 15 A, 15 B (i.e., the end of the first end panel 29 A, and of the fourth end panel 31 A) change according to the rotation angle of the gantry.

As shown in FIGS. 3-5 there is no connecting part that connects the irradiation device 13 and the moving floors 15 A, 15 B. And, the moving floors 15 A, 15 B can be operated separately from the rotation of the gantry 11 (and of the irradiation device 13 ). So, consistent with an embodiment, the flat floor 27 with no clearance can be formed regardless of the rotation angle of the gantry 11 . Due to the lack of clearance in the flat floor 27 , a person may safely and easily approach the pedestal 12 .

Ends of the moving floors 15 A, 15 B can contact the particle beam irradiation device 13 . But these ends are not connected with the particle beam irradiation device 13 . And, the moving floors 15 A, 15 B can be controlled independently from the gantry 11 and from the particle beam irradiation device 13 . Therefore, parts connecting the moving floors 15 A, 15 B and the particle beam irradiation device 13 are not necessary. So, the structure of the therapeutic device 10 is simplified. This simplified structure provides increased durability and reduces maintenance costs.

The moving floors 15 A, 15 B can provide clearance in the flat floor 27 or along arc wall 26 during maintenance of the gantry 11 or of the particle beam irradiation device 13 . In other words, the moving floors 15 A, 15 B being movable by the floor motors 16 makes it easier to access the gantry 11 or the particle beam irradiation device 13 for maintenance.

The moving floors 15 A, 15 B are independent from the particle beam irradiation device 13 . Therefore, there is no extra sound made by parts connecting the moving floors 15 A, 15 B and the particle beam irradiation device 13 . In other words, the therapeutic device 10 is quieter.

There is no need to connect the moving floors 15 A, 15 B and the particle beam irradiation device 13 . The shape of the particle beam irradiation device 13 is not limited by the connecting parts for the moving floors 15 A, 15 B. Various shapes of the particle beam irradiation device 13 may be considered. For example, a side of the particle beam irradiation device 13 may be tilted, the particle beam irradiation device 13 may be cylindrical, or the particle beam irradiation device 13 may be a relatively short compared to the height depicted in the drawings. Regardless of the shape of the particle beam irradiation device 13 , there is no clearance in the flat floor 27 with this therapeutic device 10 .

An embodiment of an arranged therapeutic device 10 A is described with reference to FIG. 7 below. It is noted that the same configurations as those described above are given the same reference symbols, thereby omitting overlapping description.

In the therapeutic device 10 A, sensors 16 A measure the distance between the moving floor 15 A, 15 B and the particle beam irradiation device 13 , and may be provided on the moving floors 15 A, 15 B. The sensors 16 A may be provided on the floor motor 16 on the ends of the first end panel 29 A and of the fourth end panel 31 A. The sensors 16 A may be provided on the floor motor 16 on the ends of the second end panel 29 B and of the third end panel 31 B. The sensors 16 A on the ends of the second end panel 29 B and of the third end panel 31 B measure the distance between the ends of the second end panel 29 B and of the third end panel 31 B.

The gantry 11 and the moving floors 15 A, 15 B can be controlled according to the distance measured by the sensors 16 A. The gantry 1 1 and the floors 15 A, 15 B can be controlled while maintaining a predetermined distance. In other words, the sensors 16 A simplify control of the movement of the gantry 11 and the moving floors 15 A, 15 B.

The sensors 16 A are not limited to be on the floor motors 16 . The sensors 16 A may be on the moving floors 15 A, 15 B directly. The sensors 16 A may be infrared sensors, which detect a distance between the moving floor 15 A and the moving floor 15 B, or between the moving floors 15 A, 15 B and the particle beam irradiation device 13 . Also, the sensors 16 A may be a detector, which can detect a position of the moving floors 15 A, 15 B, particularly a position of the ends of the moving floors 15 A, 15 B in the gantry 11 or along the rails 14 A, 14 B.

Obviously, numerous modifications and variations of the disclosed embodiments are possible in view of the above description. It is therefore to be understood that within the scope of the appended claims, the disclosed embodiments may be practiced otherwise than as specifically described herein.