Radiotherapy order and procedure for operating a radiotherapy order

Abstract

Radiotherapy order (1), comprising: a holding device (2), an X-ray source (3) to which an applicator (6) can be arranged, wherein the X-ray source (3) is arranged on the holding device (2) and is held in a positionable and orientable manner by means of the holding device (2), a sensor system (4) which is designed to detect, at least during irradiation, the position (10) and / or change in position (11) of the X-ray source (3) and / or the applicator (6), and a control device (5), wherein the control device (5) is configured to evaluate the detected position (10) and / or the detected change in position (11), and based on the detected position (10) and / or the detected and / or a specific change in position (11), to switch off or initiate the switching off of the X-ray source (3), wherein the radiotherapy arrangement (1) has an optical interlock system (8) with which the presence of an applicator (6) at the X-ray source (3) can be detected and checked, wherein the optical interlock system (8) is designed such that a position and / or a property of at least one mirror (8-5) in the optical signal path (15) can be controlled and changed so that the optical signal path (15) is interrupted, wherein the control device (5) is further configured to control the at least one mirror (8-5) to switch off the X-ray source (3) such that the optical signal path (15) is interrupted.

Description

[0001] The invention relates to a radiotherapy arrangement and a method for operating a radiotherapy arrangement.

[0002] In intraoperative radiotherapy (IORT), applicators are used to irradiate the tumor bed (e.g., in the INTRABEAM system from Carl Zeiss Meditec AG). These applicators provide access to the treatment site within the patient's body. They partially absorb the X-rays and can therefore influence the radiation delivery. This influence must be considered during treatment planning. The relevant applicator data (e.g., depth-dose curve) are typically stored on a computer for treatment planning purposes.

[0003] Each applicator allows for the insertion of a miniaturized, movable X-ray source such that an isocenter of the X-ray source, the origin of the X-ray radiation, is located in a defined position (e.g., at the center of the applicator's sphere). The X-ray source is typically controlled and / or regulated from a control panel. Part of the control panel is formed by the X-ray source's control unit, which is connected to the X-ray source via a power supply and control cable. During irradiation, it is common practice for the X-ray source and its attached applicator to be located in an operating or treatment room, while the control panel is operated separately.

[0004] The applicator and the X-ray source form a single unit for the duration of the irradiation and are held in position by the holding device. Such a holding device can be, for example, a tripod with multiple axes of movement or degrees of freedom. Normally, the operator, such as a surgeon or an assistant, moves the applicator into the tumor cavity using the holding device, which then holds the applicator in the desired position during the irradiation.

[0005] Due to regulatory requirements, shutdown devices for X-ray sources must be designed to be single-fault safe, meaning that safe operation must be possible even if a fault occurs. This can be achieved, for example, by ensuring that all necessary irradiation parameters are available in the control unit of the X-ray source from the start of the treatment, so that the treatment can be carried out in a controlled manner until completion even if the control panel fails. Thus, for example, a failure of the control panel's processing unit would not automatically stop the treatment. Furthermore, it is known to hardwire a "door switch" directly to the control unit of the X-ray source. If someone enters the treatment room during the treatment, opening the door activates the "door switch" and immediately shuts down the X-ray source automatically.

[0006] A method for validating a therapeutic radiation treatment is known from US Patent 2020 / 0038691A1. The method involves using an applicator balloon surrounding an X-ray source to carry a variety of X-ray radiation sensor elements (XRSEs). The XRSEs are distributed across the applicator balloon to detect the applied radiation from the source. At least one parameter of the applied radiation detected by the XRSE is compared to a corresponding parameter of a predetermined treatment plan. Based on this comparison, it is determined whether one or more requirements of the predetermined treatment plan have been met.

[0007] From US patent 2016 / 0029981A1, an interventional system is known with an insertion element, such as a catheter, for insertion into an object, for example, a person. A motion unit, such as a robot, moves the insertion element within the object, wherein a tracking image generation unit uses a beam of radiation to generate tracking images of the insertion element within the object, and wherein a controller controls the tracking image generation unit depending on motion parameters of the motion unit, which indicate the movement. The control operation of the controller enables a reduction of the radiation dose applied to the object.

[0008] A method for the intraoperative irradiation of breast cancer is known from US Patent 2004 / 0260142A1. In this method, breast cancer patients are irradiated intraoperatively shortly after tumor removal. The pathology of the tissue is determined using a near-immediate procedure, further excisions are performed if necessary, and the patient, still anesthetized and preferably immobilized, is then treated with radiation therapy. In one embodiment, an applicator is inserted into the excision cavity, the cavity is imaged three-dimensionally using radiation sources and a sensor, a radiation treatment plan is developed using a radiation protocol and the determined shape and location of the cavity and the treatment area, and the plan is executed while the patient remains under anesthesia.

[0009] US Patent 2014 / 0051904A1 discloses an energy delivery device for applying energy to an object, wherein the object comprises a location containing radioactive material, and wherein the energy delivery device includes a location detection unit usable for locating the location, and an X-ray unit for applying X-rays to the detected location of the object. Since the location to which energy is to be applied comprises radioactive material, this location can be accurately located using the location detection unit. Furthermore, since the application of the X-rays can be precisely controlled, for example, by controlling the intensity and energy spectrum of the X-rays, energy can be applied precisely to the accurately detected location.

[0010] US 2017 / 0239491A1 describes a real-time applicator position monitoring system (RAPS). This system measures the displacement of the brachytherapy applicator in real time by calculating the relative displacement between two infrared-reflecting targets, one attached to the applicator and the other to the patient's skin. In some respects, RAPS can be used in any brachytherapy application. RAPS measures applicator movement during HDR brachytherapy treatment as well as during patient transfer from the imaging room (where, for example, the CT and MR scanners are located) to the HDR BT operating / treatment room.

[0011] German patent DE 10 2020 200 400 A1 describes a device for irradiating an object. The device includes an applicator for irradiating the object and a detector system configured to detect light emanating from an irradiated area and generate a detector signal based on this detection. A processor unit is configured to determine a value for a property based on this signal and, based on this determined value, to calculate the irradiation dose.

[0012] The invention is based on the objective of improving a radiotherapy arrangement and a method for operating a radiotherapy arrangement, particularly with regard to operational safety.

[0013] The problem is solved according to the invention by a radiotherapy arrangement with the features of claim 1 and a method with the features of claim 9. Advantageous embodiments of the invention are set forth in the dependent claims.

[0014] One of the fundamental concepts of the invention is to detect the position and / or changes in position of the X-ray source and / or an applicator attached thereto, at least during irradiation. This is achieved by means of a dedicated sensor system. A control unit connected to the sensor system evaluates the detected position and / or changes in position. Based on the detected position and / or changes in position, the control unit switches off or initiates the shutdown of the X-ray source. It may be provided that the control unit determines the change in position from the detected position, for example, by calculating the difference between individual values ​​of the detected position.The rationale for this approach is that, compared to linear accelerators, the X-rays used in radiotherapy are very low-energy and therefore exhibit a very steeply declining depth-dose curve. This means that even very small positional deviations during irradiation have a significant impact on the applied dose distribution in the irradiated tissue. To avoid irradiating healthy tissue, the position and / or changes in position of the X-ray source and / or the applicator can be monitored using the radiotherapy setup and method described in this disclosure, and measures can be taken to switch off the X-ray source based on the position and / or changes in position.

[0015] The radiotherapy setup and procedure improve safety during irradiation, as position and / or changes in position can be monitored.

[0016] This can prevent unwanted and damaging radiation exposure to healthy tissue.

[0017] In particular, a radiotherapy arrangement is created, comprising a holding device and an X-ray source to which an applicator can be attached, wherein the X-ray source is arranged on the holding device and is positionable and orientable by means of the holding device, and a sensor system which is configured to detect the position and / or change of position of the X-ray source and / or the applicator at least during irradiation, and a control device, wherein the control device is configured to evaluate the detected position and / or change of position, and to switch off or initiate the switching off of the X-ray source based on the detected position and / or the detected and / or a specific change of position.

[0018] Furthermore, a method for operating a radiotherapy arrangement is provided in particular, wherein at least during irradiation a position and / or a change in position of an X-ray source and / or an applicator arranged thereon on a holding device is detected by means of a sensor, wherein the detected position and / or the detected change in position is evaluated by means of the control device, and wherein, starting from the detected position and / or the detected and / or a specific change in position, the X-ray source is switched off or initiated by means of the control device.

[0019] Parts of the control system can be implemented individually or collectively as a combination of hardware and software, for example, as program code executed on a microcontroller or microprocessor. However, it is also possible for parts to be implemented individually or collectively as an application-specific integrated circuit (ASIC) and / or a field-programmable gate array (FPGA).

[0020] The holding device can be, in particular, a tripod. Specifically, the tripod can be a multi-jointed tripod that can be moved about several axes or that can provide several degrees of freedom for the X-ray source and the applicator attached to it. The tripod can, in particular, be a 6-axis tripod. The tripod is, in particular, mechanically and / or motor-assisted, for example, by means of servo motors.

[0021] A sensor system can comprise one or more sensors. The sensors can be of the same or different types. In particular, the sensors can be position sensors and / or angle sensors (e.g., on rotary axes). The sensors can, for example, be potentiometers. Depending on the voltage values ​​of the potentiometer, an angular position can be determined.

[0022] The sensor system may include optical sensors. For example, it may be provided that the position and / or changes in position are detected using optical markers arranged on the holding device and / or the X-ray source and / or the applicator, and at least one camera.

[0023] In one embodiment, the control unit is further configured to compare the detected and / or determined change in position with a predetermined threshold and to initiate or trigger the shutdown if the comparison shows that the detected and / or determined change in position exceeds the predetermined threshold. This allows a threshold for a maximum change in position to be set, which should be adhered to during irradiation. If the maximum change in position is exceeded, the irradiation is terminated by switching off the X-ray source.

[0024] In one embodiment, the sensors are arranged in and / or on the holding device. This allows an X-ray source and an applicator to continue operating in the conventional manner without requiring any extensions or attachments. For example, one or more position sensors and / or angle sensors can be arranged in and / or on the holding device to detect movement of the holding device and thereby determine or estimate the position and / or change in position of the X-ray source and / or the applicator. The sensors detect a position and / or angle, etc., on the holding device. Through a mechanically fixed relationship to the X-ray source and the applicator attached to the holding device, the position and / or change in position of the X-ray source and / or the applicator can be determined and / or estimated.For example, a mathematical transformation of positions and / or angles or changes in position and / or angle of the holding device or parts of the holding device into a position and / or change in position of the X-ray source and / or the applicator can be determined and / or used for this purpose.

[0025] In one embodiment, the radiotherapy arrangement includes an interrupt switch that is, or can be, integrated into the signal chain of a safety door switch, with the control unit further configured to activate the interrupt switch to shut off the X-ray source. This allows an existing system to be easily expanded without requiring any changes to existing control and monitoring sequences. For example, the interrupt switch can be integrated into a signal connection to the safety door switch. This allows existing infrastructure to be reused. The control and monitoring functions and devices that cause the X-ray source to shut off when the door is opened can thus continue to be used. The interrupt switch specifically features an "active to" functionality (i.e.,a "normally off" characteristic) means that the interrupt switch must be actively closed, for example by a dedicated control voltage provided by the control unit. If this control voltage fails, for example because a change in position is detected or because the control unit's power supply fails, the interrupt switch opens automatically and a signal chain of the safety door switch is interrupted, causing the X-ray source to be switched off.

[0026] The radiotherapy setup is designed to include an optical interlock system for detecting and verifying the presence of an applicator at the X-ray source. This optical interlock system is configured to allow for the controlled modification of the position and / or property of at least one mirror in the optical signal path, thereby interrupting the optical signal path. Furthermore, the control unit is configured to actuate the at least one mirror to switch off the X-ray source, thus interrupting the optical signal path. This allows for the simple expansion of an existing optical interlock system without requiring modifications to the control and monitoring procedures. For example, it may be possible to incorporate or integrate the at least one mirror into an existing optical interlock system.This allows existing infrastructure to be reused. In a typical optical interlock system, a light beam is deflected multiple times to travel from a light source, such as a light-emitting diode or a laser diode, to a photodetector, such as a photodiode. When light is detected by the photodetector, the interlock system is closed and the X-ray source is enabled. Conversely, when no light is detected by the photodetector, the interlock system does not enable the X-ray source. This embodiment takes advantage of this by inserting at least one mirror at a suitable position in the light's signal path. This deflects the light appropriately to travel from the light source to the photodetector or to interrupt the signal path by changing the mirror's position and / or properties.

[0027] In a further developed embodiment, the optical interlock system is designed such that the angular position of at least one partial surface of the at least one mirror can be controlled and changed to interrupt the optical signal path. Control of the angular position can be achieved either motor-driven or magnetically. In particular, the at least one mirror is moved out of the signal path, especially by being folded out, thereby interrupting the signal path. A light beam used for the interlock system then no longer reaches the photodetector.

[0028] In a further refined embodiment, the optical interlock system is designed such that the reflectance of the at least one mirror can be controlled and varied to interrupt the optical signal path. For example, the at least one mirror can include micromirrors with which a reflection angle can be controlled. For example, the at least one mirror can include a micromirror actuator (Digital Micromirror Device (DMD), for example, from Texas Instruments, USA). Alternatively, a liquid crystal layer (e.g., a liquid crystal display, LCD) can be arranged on a mirror surface, which can control and vary the transmittance, thereby changing the reflectance of the at least one mirror to interrupt the signal path.

[0029] In one embodiment, the radiotherapy arrangement has a communication link to an operating device with which the radiotherapy arrangement can be operated. The control unit is configured to transmit the detected position and / or the detected and / or determined change in position and / or a shutdown signal to the operating device via the communication link. This allows an operator of the radiotherapy arrangement to receive information and / or feedback on the detected position and / or the determined and / or detected change in position at the operating device. Furthermore, controlled shutdown can then also be performed via the operating device, which typically supplies power to the X-ray source. It can also be provided that the position and / or the change in position can be recorded using the operating device.The communication link can be wired or wireless.

[0030] Furthermore, a radiotherapy system is also created, comprising an operating device and a radiotherapy arrangement according to one of the described embodiments.

[0031] Further features regarding the design of the procedure are derived from the description of the various configurations of the radiotherapy setup. The advantages of the procedure are the same in each case as in the configurations of the radiotherapy setup.

[0032] The invention is explained in more detail below with reference to preferred embodiments and the figures. These show: Fig. 1 a schematic representation of embodiments of the radiotherapy arrangement and the radiotherapy system; Fig. 2 A schematic representation to illustrate another embodiment of the radiotherapy arrangement.

[0033] The Fig. Figure 1 shows a schematic representation of an embodiment of the radiotherapy arrangement 1. The radiotherapy arrangement 1 comprises a holding device 2, an X-ray source 3, a sensor 4 and a control device 5.

[0034] The holding device 2 is designed, for example, as a multi-jointed stand with several degrees of freedom. The X-ray source 3 is arranged on the holding device 2 and can be positioned and oriented in these degrees of freedom by means of the holding device 2. An applicator 6 can be arranged on the X-ray source 3. Once the applicator 6 is arranged on the X-ray source 3, it can be positioned together with the X-ray source 3, in particular by means of the stand, for irradiation in a tumor cavity of a patient and held there in a predetermined position and orientation. The applicator 6 is, in particular, interchangeable and can be specifically selected for the respective irradiation task (e.g., area irradiation, irradiation of a tumor cavity with isotropic distribution of the radiation dose, etc.).

[0035] The sensor system 4 is configured to detect, at least during irradiation, a position 10 and / or a change in position 11 of the X-ray source 3 and / or the applicator 6. The sensor system 4 is, in particular, arranged in and / or on the holding device 2 and detects a position and / or a change in position of the holding device 2, which can then be converted into a position 10 and / or a change in position 11 of the X-ray source 3 and / or the applicator 6 via a transformation formula. This conversion can be performed by the sensor system 4 or in the control unit 5. The sensor system 4 can, for example, comprise position sensors 4-1 and / or angle sensors 4-2, with which the position and / or the change in position of the holding device 2 can be detected, in particular by detecting axis positions.

[0036] The control unit 5 includes, for example, a computing unit and a memory (both not shown) to perform calculations. The control unit 5 is configured to evaluate the detected position 10 and / or the detected change in position 11, and, based on the detected position 10 and / or the detected and / or a specific change in position 11, to switch off or initiate the switching off of the X-ray source 3. It may be provided that the control unit 5 determines the change in position 11 from the detected position 10, for example, by calculating the corresponding difference between detected positions 10 over the duration of the irradiation.

[0037] Together with an operating device 30, the radiotherapy arrangement 1 forms a radiotherapy system 100. The operating device 30 comprises a control unit 31 for the X-ray source 3, which also supplies the X-ray source 3 with energy. The control unit 31 and the X-ray source 3 are connected to each other via a supply and control line 34. Furthermore, the operating device 30 comprises a display and control unit 33 for displaying information and for operating the radiotherapy system 100.

[0038] In particular, the radiotherapy arrangement 1 may be provided with a communication link 9 to the operating device 30, wherein the control unit 5 is configured to transmit the detected position 10 and / or the detected and / or determined change in position 11 and / or a shutdown signal to the operating device 30 via the communication link 9. The position 10 and / or the change in position 11 can, for example, be displayed on the display and operating device 33 for informational purposes. The shutdown signal, on the other hand, serves to switch off the X-ray source 3 via the control unit 31, for example by interrupting the power supply to the X-ray source 3.

[0039] The control unit 5 may be further configured to compare the detected and / or determined change in position 11 with a predetermined threshold 12 and to shut down or initiate a shutdown if the comparison shows that the detected and / or determined change in position 11 is greater than the predetermined threshold 12. Such a threshold 12 is, in particular, a specification for a maximum change in position of the X-ray source 3 and / or the applicator 6 attached to it during irradiation. Such a threshold 12 may, for example, be a specification for a change in position in a dimension of a maximum of + / - 1 mm. The position 10 and / or change in position 11 are continuously compared with the predetermined threshold 12 during irradiation, and as soon as the predetermined threshold 12 is reached or exceeded, the shutdown is initiated or initiated.The threshold value 12 can be specified, for example, using the operating device 30 and is stored, for example, in the memory of the control unit 12.

[0040] The radiotherapy setup 1 may be provided with an interrupt switch 7, which is or can be integrated into a signal chain of a safety door switch 20, and the control unit 5 is further configured to actuate the interrupt switch 7 to switch off the X-ray source 3. The safety door switch 20 ensures that the X-ray source 3 is switched off if a door to the treatment room is opened during irradiation. By integrating the interrupt switch 7 into the signal chain of the safety door switch 20, the function of the safety door switch 20 can be used to switch off the X-ray source 3. The interrupt switch 7 has, in particular, an "actively closed" characteristic (or a "normally off" characteristic), meaning that a closed state must be actively brought about by a control voltage. If this control voltage is absent, the interrupt switch 7 opens.The control unit 5 is connected to the interrupt switch 7 via a control line 13.

[0041] It is provided that the radiotherapy arrangement 1 has an optical interlock system 8 with which the presence of an applicator 6 at the X-ray source 3 can be detected and checked, wherein the optical interlock system 8 is designed in such a way that a position and / or a property of at least one mirror in the optical signal path can be controlled and changed so that the optical signal path is interrupted.

[0042] This is schematically illustrated for one embodiment in the Fig. Figure 2 illustrates this. The optical interlock system 8 comprises a light source 8-1, for example a light-emitting diode or laser diode, a photodetector 8-2, for example a photodiode, on the side of the X-ray source 3, and two mirrors 8-3, 8-4 on the side of the applicator 6. Furthermore, the optical interlock system 8 on the side of the X-ray source 3 includes, in particular, a controllable mirror 8-5. The position of the controllable mirror 8-5 can be controlled to two angular positions 16-1, 16-2. This allows the optical signal path 15 to be selectively interrupted. The controllable mirror 8-5 may be spring-loaded in one of the angular positions 16-1, 16-2, particularly in the angular position 16-1. Normally, the optical interlock system 8 monitors the presence of an applicator 6 at the X-ray source 3.If an applicator 6 is present and correctly positioned at the X-ray source 3, light from the light source 8-1 can reach the photodetector 8-2 via signal path 15, and the presence of the applicator 6 can be detected therein. If no applicator 6 is positioned at the X-ray source 3, the light does not reach the photodetector 8-2 from the light source 8-1, and the absence of the applicator 6 can thus be detected. The controllable mirror 8-5 can also interrupt signal path 15 in the presence of the applicator 6, thereby preventing operation of the X-ray source 3. A signal from the optical interlock system 8 is transmitted via the supply and control line 34 (. Fig. 1) to the operating unit 30 ( Fig. 1) transmitted.

[0043] The control unit 5 is configured to control the controllable mirror 8-5 to switch off the X-ray source 3 in such a way that the optical signal path 15 is interrupted or is interrupted. The X-ray source 3 is then switched off via the operating device 30, using the same functionality that prevents the operation of the X-ray source 3 when the applicator 6 is absent.

[0044] As an alternative to a single large controllable mirror 8-5 with only a single reflective surface, a micromirror actuator (not shown, Digital Micromirror Device, DMD) can also be used, in which a plurality of mirror elements arranged in a two-dimensional grid can be controlled such that the angle at which light incident on the mirror elements is reflected is deflected in a controlled, predetermined direction. The control unit 5 then controls the micromirror actuator accordingly.

[0045] Alternatively or additionally, the optical interlock system 8 can be configured such that the reflectance of the controllable mirror 8-5 can be controlled and varied to interrupt the optical signal path 15. For example, a liquid crystal can be arranged in front of the mirror 8-5 (whose angular position cannot be changed), the transmittance of which can be controlled, and the reflectance of the mirror 8-5 controlled by this transmittance. The control device 5 then controls the liquid crystal accordingly. Reference symbol list 1. Radiotherapy order 2 Holding device 3 X-ray source 4 Sensors 4-1 Position sensor(s) 4-2 angle sensor(s) 5 Control unit 6 Applicator 7 circuit breakers 8 optical interlock system 8-1 Light source 8-2 Photodetector 8-3 mirrors 8-4 mirrors 8-5 adjustable mirror 9 Communication link 10 positions 11 Change of location 12 Threshold 15 optical signal path 16-1 Angle position (signal path closed) 16-2 angular position (signal path interrupted) 20 safety door switches 30 Operating device 31 Control unit 33 Display and control unit 34 Supply and control line 100 radiotherapy systems

Claims

Radiotherapy arrangement (1), comprising: a holding device (2), an X-ray source (3) to which an applicator (6) can be attached, wherein the X-ray source (3) is attached to the holding device (2) and is held in a positionable and orientable manner by means of the holding device (2), a sensor (4) configured to detect, at least during irradiation, a position (10) and / or a change in position (11) of the X-ray source (3) and / or the applicator (6), and a control device (5), wherein the control device (5) is configured to evaluate the detected position (10) and / or the detected change in position (11), and, based on the detected position (10) and / or the detected and / or a specific change in position (11), to switch off or initiate the switching off of the X-ray source (3), wherein the radiotherapy arrangement (1) has an optical interlock system (8).with which the presence of an applicator (6) at the X-ray source (3) can be detected and verified, wherein the optical interlock system (8) is configured such that a position and / or a property of at least one mirror (8-5) in the optical signal path (15) can be controlled and changed so that the optical signal path (15) is interrupted, wherein the control device (5) is further configured to control the at least one mirror (8-5) to switch off the X-ray source (3) such that the optical signal path (15) is interrupted. Radiotherapy arrangement (1) according to claim 1, characterized in that the control device (5) is further configured to compare the detected and / or determined change in position (11) with a predetermined threshold (12) and to perform or initiate the shutdown if a comparison result shows that the detected and / or determined change in position (11) is greater than the predetermined threshold (12). Radiotherapy arrangement (1) according to claim 1 or 2, characterized in that the sensor (4) is arranged in and / or on the holding device (2). Radiotherapy arrangement (1) according to one of the preceding claims, characterized by an interrupt switch (7) which is or can be integrated into a signal chain of a safety door switch (20), wherein the control device (5) is further configured to control the interrupt switch (7) to switch off the X-ray source (3). Radiotherapy arrangement (1) according to one of the preceding claims, characterized in that the optical interlock system (8) is designed such that an angular position (16-x) of at least one partial surface of the at least one mirror (8-5) can be controlled to change in order to interrupt the optical signal path (15). Radiotherapy arrangement (1) according to one of the preceding claims, characterized in that the optical interlock system (8) is designed such that a reflectance of the at least one mirror (8-5) can be controlled and changed in order to interrupt the optical signal path (15). Radiotherapy arrangement (1) according to one of the preceding claims, characterized by a communication connection (9) to an operating device (30) with which the radiotherapy arrangement (1) can be operated, wherein the control unit (5) is configured to transmit the detected position (10) and / or the detected and / or determined change in position (11) and / or a shutdown signal via the communication connection (9) to the operating device (30). Radiotherapy system (100) comprising an operating device (30) and a radiotherapy arrangement (1) according to one of the preceding claims. Method for operating a radiotherapy arrangement (1), wherein, at least during irradiation, the position (10) and / or a change in position (11) of an X-ray source (3) arranged on a holding device (2) and / or an applicator (6) arranged thereon is detected by means of a sensor (4), wherein the detected position (10) and / or the detected change in position (11) is evaluated by means of a control device (5), and wherein, based on the detected position (10) and / or the detected and / or a specific change in position (11), the X-ray source (3) is switched off or initiated by means of the control device (5), wherein the presence of an applicator (6) on the X-ray source (3) is detected and checked by means of an optical interlock system (8), wherein the optical interlock system (8) is designed such that a position and / or a property of at least one mirror (8-5) in the optical signal path (15) can be controlled and changed.so that the optical signal path (15) is interrupted, wherein the at least one mirror (8-5) for switching off the X-ray source (3) is controlled by the control device (5) in such a way that the optical signal path (15) is interrupted.

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