Applicator for a radiotherapy device

Abstract

Applicator (17; 17a; 17b) for protecting a medical radiotherapy device (2) when inserting the radiotherapy device (2) into a body to be treated, the applicator (17; 17a; 17b) comprising: an applicator body (19) which can be placed on the radiotherapy device (2) and mechanically connected to the radiotherapy device (2) and which has at least one X-ray-sensitive indicator (23 to 33), wherein the at least one indicator (23 to 33) is configured such that at least one optical property of the at least one indicator (23 to 33) in the visible spectral range changes permanently as a function of an X-ray radiation dose acting on the at least one indicator (23 to 33).

Description

The present invention relates to a medical radiation therapy device for local irradiation of a body to be treated with radiation, in particular X-ray radiation. In particular, the invention relates to an applicator for such a radiotherapy device, which is arranged between the radiotherapy device and the body when the radiotherapy device is introduced into the body to be treated.In the field of therapy using X-ray radiation, therapies exist in which X-ray radiation is to be generated in the interior of a human or animal body in the vicinity of tissue to be treated. Medical radiation therapy devices exist for this purpose. An exemplary radiation therapy device comprises a particle beam system which can generate a high-energy particle beam. The particle beam is directed through a tube of the radiation therapy device having a length of a few centimeters onto an X-ray material which is arranged at the end of the tube. By interaction of the particle beam with the X-ray material, this generates X-ray radiation which is provided for the therapy of tissue.In order that the X-ray generated by the X-ray material at the tip of the tube can be applied inside a body, the tube is introduced into the body. For this purpose, the tube is surrounded by an applicator which, on the one hand, constitutes a sterile barrier and, on the other hand, protects the tube.The applicator conventionally consists of a material which changes structurally by the X-ray radiation acting on the applicator. For example, the material of the applicator becomes brittle, which can lead to the breakage of the applicator. In addition, the absorption behavior of the applicator for x-ray radiation can change as a function of the x-ray radiation dose applied to the applicator, so that the x-ray radiation intensity transmitted through the applicator can change as the duration of use of the applicator progresses. These changes are not tolerable in medical applications and the applicator must be replaced. In some cases, an applicator may be used only for a single radiotherapy treatment and may be replaced after the radiotherapy treatment.There is therefore a need to know the duration of use of an applicator and the dose of X-ray radiation applied to the applicator in order to be able to determine whether or not the applicator can continue to be used for medical radiation therapy purposes.Applicators are conventionally provided with an identifier, for example a serial number, which allows the identification of the applicator. In a usage log, the usage parameters of the applicator are logged, for example the individual usage times and the x-ray radiation dose used. With the use protocol it is possible to determine whether an applicator has already been used and how high the X-ray dose already applied to the applicator is. However, this system for monitoring the use parameters of an applicator is cumbersome and prone to errors.U.S. Pat. No. 7,662,083 B2 discloses apparatuses and methods for carrying out a brahy therapy in the manner of "afterloading". In particular, a catheter is disclosed which comprises a cavity bounded by a wall. The cavity serves to receive radiation sources. The wall comprises light guides with scintillator material which emits light when the radiation source is placed in the cavity. The light emitted by the scintillator material is guided to a detector and detected by the light guides. A signal representing the detected light is used, for example, for monitoring and changing an irradiation plan.US 2011 / 0 105 822 A1 relates to a balloon catheter for an X-ray application.EP 1 251 778 B1 relates to a device for irradiating a human or animal body. The device comprises a catheter having a catheter head. The catheter head KK is stretchable in the manner of a balloon catheter. In order to keep undesired irradiation of a risk organ which, in the extended state of the catheter head, abuts the catheter as small as possible, it is proposed to determine the position of the catheter head on the risk organ in a time-dependent manner. For this purpose, a sensor unit is provided in the catheter head, which can measure the position and orientation of the catheter head. The acquired information (position and orientation) is transmitted to a receiving unit for further processing. Further, the device may further comprise a dosimeter unit disposed in the catheter head. The dosimeter unit measures the radiation dose. It can be checked with this whether the radiation dose at the risk organ is kept small as desired.U.S. Pat. No. 6,251,059 B1 relates to an inflatable catheter and a dosimetry indicator.DE 10 2016 104 322 A1 discloses an apparatus and a method for optimized radiotherapy of a tumor in one of the organs of the small pelvis or in the head-and-neck region with ultrasonic examination for determining the position of the organs and / or the tumor tissue. The device comprises a pin-shaped outer sheath of ultrasonic material tapering on an end face and an ultrasonic sensor located therein.DE 10 2005 056 080 A1 discloses an apparatus for X-ray brachytherapy and a method for positioning a probe introduced into the interior of a body for X-ray brachytherapy, said probe having an X-ray source at its distal end, said X-ray source emitting X-rays into an irradiation region outside the probe. A plurality of markers are provided which are recognizable in an image generated by an imaging device and which are arranged in or on the probe in a known spatial relationship to the irradiation region.In view of this, it is an object of the present invention to provide an efficient, simple and less error-prone possibility for monitoring the use of an applicator for a medical radiation therapy device and an improved radiation therapy system.The object is achieved by the invention according to the subject matter of the independent claims. Advantageous further developments of the invention are defined in the dependent claims.One aspect of the invention relates to an applicator which is suitable for protecting a medical radiation therapy device when the radiation therapy device is introduced into a body to be treated, wherein the applicator comprises an applicator body which can be placed on the radiation therapy device and can be mechanically connected to the radiation therapy device and has at least one X-ray radiation-sensitive indicator, wherein the at least one indicator is configured such that at least one optical property of the at least one indicator changes permanently in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator.A further aspect of the invention relates to an applicator for protecting a medical radiation therapy device when the radiation therapy device is introduced into a body to be treated, wherein the applicator comprises: an applicator body, which can be placed on the radiation therapy device and can be mechanically connected to the radiation therapy device and has at least one X-ray radiation-sensitive indicator, wherein the at least one indicator is configured such that at least one optical property of the at least one indicator changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator, wherein the at least one indicator comprises a radiochrome film.A further aspect of the invention relates to an applicator for protecting a medical radiation therapy device when inserting the radiation therapy device into a body to be treated, wherein the applicator comprises: an applicator body, which can be placed on the radiation therapy device and mechanically connected to the radiation therapy device and has at least one X-ray radiation-sensitive indicator, wherein the at least one indicator is configured such that at least one optical property of the at least one indicator changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator, wherein the at least one indicator has a writing which is visible to the naked eye if the X-ray radiation dose acting on the at least one indicator is greater than a limit value designed for the respective indicator and which is not visible to the naked eye, if the X-ray radiation dose applied to the at least one indicator is less than the limit value designed for the respective indicator.A further aspect of the invention relates to a radiation therapy system which comprises such an applicator and such a radiation therapy device.A further aspect of the invention relates to a radiotherapy system comprising: an applicator for protecting a medical radiotherapy device when the radiotherapy device is introduced into a body to be treated; and the radiotherapy device, which is configured to generate X-ray radiation for irradiating the body to be treated; wherein the applicator comprises: an applicator body, which can be placed on the radiotherapy device and can be mechanically connected to the radiotherapy device and has at least one X-ray radiation-sensitive indicator, wherein the at least one indicator is configured such that the absorption spectrum and / or the reflection spectrum of the at least one indicator changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator, wherein the at least one indicator lies on or below a surface of the applicator body, wherein the applicator body has a tubular, elongate shape; wherein the radiation therapy device comprises a main body with a tube extending away from the main body, wherein the tube is inserted into the body to be treated for irradiation of the body to be treated, and wherein the applicator body of the applicator is fittable onto the tube.The applicator can be used in cooperation with the medical radiation therapy device because the applicator body of the applicator can be placed on the radiation therapy device and mechanically connected to the latter.The applicator body has one or more X-ray radiation-sensitive indicators. One or more optical properties of each indicator in the visible spectral range change depending on the X-ray dose applied to the respective indicator up to now.Optical properties are, for example, the absorption spectrum and the reflection spectrum, and therefore the transparency, the color or the gray value with which the indicator can be perceived with the naked eye.The visible spectral range extends, for example, from 400 nm to 750 nm.If X-ray radiation acts on the indicator or indicators, at least one optical property of the respective indicator, for example the transparency, the color or the grayscale value of the respective indicator, changes as a result. In other words, the indicator changes color with increasing X-ray dose acting on the indicator.Since the change in the optical property or the optical properties of the respective indicator relates to the visible spectral range, the indicator or the change in the optical property can be perceived with the naked eye. This makes it easy to identify whether the applicator has already been exposed to X-ray radiation or has been used for radiation therapy with X-ray radiation. Based on the optical property(s) of the respective indicator or its change(s), the X-ray dose applied to the applicator can also be estimated.Each indicator can be configured such that its optical property(s) changes immediately after the respective indicator is exposed to an X-ray radiation. Accordingly, it is not necessary to "develop" the indicator, as is the case, for example, with other X-ray sensitive materials. The "development" in these cases is carried out, for example, by adding a chemical to the indicator, the chemical making the structural change of the indicator brought about by the X-ray radiation which is applied visible. Accordingly, in the applicator according to the present invention, the irradiation of the applicator with X-ray radiation can be detected directly, since the respective indicators react directly to the X-ray radiation acting as a result of a change in their optical properties which can be perceived by the naked eye.The at least one indicator may comprise or consist of a radiochrome film. A radiochrome film is a film made of a material or a material composition whose optical properties in the visible spectral range change directly under the action of X-rays. Examples of radiochromatic films are the GAFCHROMATIC films from ASHLAND.The at least one indicator can be arranged on the applicator body such that the at least one indicator is perceptible with the naked eye. This makes it possible to easily visually recognize the indicator and consequently to assess whether the applicator still has the desired properties.Some or all of the indicators may lie on the surface of the applicator body, for example by applying a radiochrome film to the surface of the applicator body. Alternatively, some or all of the indicators may be underlying the surface of the applicator body. As a result, the indicators can be protected from mechanical external influences.The indicators are sensitive to X-rays, i.e. one or more of their optical properties in the visible spectral range change under the action of X-rays having an energy of 10 keV to 250 keV.Preferably, the indicators are largely insensitive to light in the visible spectral range. This means that the at least one optical property in the visible spectral range, for which the indicators are sensitive to x-rays, changes at most slightly by illumination with light of the visible spectral range. Since the applicators are generally used in an environment met by visible light, it is thereby possible to prevent the optical properties of the indicators from changing as a result of the ambient light. This in turn facilitates the interpretation of the indicators, since changes in their optical properties thus relate substantially only to X-ray radiation which is acted upon.The applicator body may have a tubular, elongated shape.According to an exemplary embodiment, the at least one indicator is transparent in the visible spectral range when no X-ray radiation has acted on the at least one indicator, and the transparency of the at least one indicator decreases with increasing X-ray radiation dose acted on the at least one indicator.In this embodiment, the indicator is not perceptible to the naked eye if no X-ray radiation has previously acted on the indicator, whereby it can be easily established that the applicator has not yet been used for an X-ray therapy. Under the action of X-ray radiation on the indicator, for example by using the applicator in an X-ray therapy treatment, the transparency of the indicator decreases, which means that the indicator becomes visible with the naked eye. This makes it easy to establish that the applicator has already been used for X-ray radiation therapy.According to an exemplary embodiment, the indicator includes a font indicating the meaning of the indicator. The text specifies, for example, a limit value. The indicator may be configured such that the optical property of the indicator changes greatly when the X-ray dose applied to the indicator reaches or exceeds the threshold. In conjunction with the font indicating the threshold value and the indicator whose optical property greatly changes when the X-ray dose applied to the indicator reaches or exceeds the threshold value, the meaning of the indicator can be easily understood.According to a further embodiment, the writing itself can be the indicator. This means, for example, that the indicator has a writing which is visible with the naked eye when the X-ray dose applied to the indicator is greater than a limit value designed for the indicator and which is not visible with the naked eye (for example because it is transparent) when the X-ray dose applied to the indicator is less than the limit value. The text may indicate the threshold.In this embodiment, the writing indicating the threshold value is visible to the naked eye only when the X-ray dose applied to the writing exceeds the threshold value. As a result, the X-ray radiation dose applied to the applicator can be represented in a simple manner by the writing and can thus be perceived visually.An applicator may include a plurality of different indicators. The plurality of indicators may be differently sensitive to x-ray radiation. This means that, for example, the reflection spectrum of the individual indicators changes to different extents by X-ray radiation acting on the respective indicator.For example, the applicator body has a plurality of indicators which are different from one another and are configured such that an optical property of the indicators changes to different extents in the visible spectral range as a function of an X-ray radiation dose acting on the indicators.By means of several different indicators, the X-ray dose applied to the applicator can be detected more accurately. This makes it possible to better assess whether or not an applicator continues to have the desired properties, that is to say for example can still be used for medical radiation therapy applications.Embodiments of the invention are explained in more detail below with reference to figures. The following shows: FIG. 1 shows a schematic illustration of a radiation therapy system for local irradiation of a body with radiation and an applicator, FIG. 2 shows an example of an applicator with a radiation-sensitive indicator, FIG. 3 shows a further example of an applicator with a plurality of different radiation-sensitive indicators, and FIG. 4 shows further examples of applicators with a plurality of radiation-sensitive indicators, each of which has a letter for identifying the radiation dose applied to the applicator.FIG. 1 shows a schematic illustration of a radiation therapy system 1. the radiation therapy system 1 comprises a radiation therapy device 2 for therapy of a body by irradiation of the body with X-ray radiation. The radiation therapy device 2 comprises a main body 3 with a tube 5 extending away from the main body 3. At an end of the tube 5 remote from the main body 3 an X-ray material 7 can be arranged (in the interior of the tube 5) which is suitable for emitting X-ray radiation 9.The radiation therapy device 2 is configured to generate the X-ray radiation 9 by means of the X-ray material 7. For this purpose, the radiation therapy device 2 can comprise a particle beam system, not shown in the figures, arranged inside the main body 3, which directs a particle beam inside the tube 5 onto the X-ray material 7, which emits the X-ray radiation 9 by interaction with the particle beam.The main body 3 can be supported by a stand 11 as shown in FIG. 1. The stand 11 has joints 13 and links 15. The joints 13 each connect two of the links 15 together and provide one or more degrees of freedom of movement therebetween. The stand 11 supports the weight of the main body 3, thereby facilitating the handling of the main body 3 for a therapist.In order to be able to easily provide a sterile barrier between the radiation therapy device 2 and a body to be treated and to protect both the radiation therapy device 2 and the body to be treated, the radiation therapy system 1 further comprises an applicator 17 which can be placed on the part of the radiation therapy device 2 which is introduced into the body, for example the tube 5.The applicator 17 comprises an applicator body 19 which, in the example shown in FIG. 1, has a tubular, elongate shape. Other forms of the applicator body 19 are possible and depend on the shape of the medical radiation therapy device 2 or on the shape of the tube 5.FIG. 2 shows an example of the applicator 17. the applicator body 19 has an opening 21 which continues in the interior of the applicator body 19 so that the applicator 17 has a recess bounded by the opening 21. The applicator 17 can be placed on the radiation therapy device 2 and mechanically connected to the latter by the tube 5 of the radiation therapy device 2 being inserted into the opening 21 of the applicator 17.The applicator 17 shown in FIG. 2 has an X-ray radiation-sensitive indicator 23, which lies at the end of the applicator body 19 which is opposite the end of the applicator body 19 at which the opening 21 lies. When the applicator 17 is placed on the medical radiation therapy device 2 and the radiation therapy device 2 generates the X-ray radiation 9, the X-ray radiation 9 penetrates the part of the applicator 17 on which the indicator 23 lies. Thus, the X-ray 9 acts on the indicator 23.An optical property of the indicator 23, for example the transparency or the color of the indicator 23, changes due to the X-ray radiation 9, and thus the X-ray radiation dose acting on the indicator 23 and thus on the applicator 17 can be recognized and evaluated with the naked eye on the basis of the optical property in the visible spectral range. The indicator 23 can be arranged on the applicator body 19 such that the indicator 23 is located at a position at which the X-ray radiation 9 has the highest intensity when the radiation therapy device 2 is operated with the applicator 17 placed on the radiation therapy device 2. However, other positions of the indicator 23 on the applicator body 19 are also possible.Fig. 3 shows another example of an applicator 17a. The applicator 17a has a plurality of different radiation-sensitive indicators 24 and 25. The indicators 24 and 25 are configured such that their optical property, for example their transparency or color, changes to different extents depending on the X-ray dose which acts on the indicators 24 and 25. For example, the indicator 24 is transparent when the dose of radiation applied to the indicator 24 is less than 5 Gy. The indicator 24 becomes gray, i.e. its transparency decreases clearly perceptibly if the radiation dose applied to the indicator 24 is greater than 5 Gy. For example, the indicator 25 is transparent when the dose of radiation applied to the indicator 25 is less than 10 Gy. The indicator 25 becomes gray, i.e. its transparency decreases clearly perceptibly if the radiation dose applied to the indicator 25 is greater than 10 Gy.Thus, it can be easily recognized with the naked eye whether the dose of radiation applied to the applicator 17a is less than 5 Gy or between 5 Gy and 10 Gy or greater than 10 Gy.FIG. 4 shows further examples of applicators 17 bhaving a plurality of different radiation-sensitive indicators. The indicator 17 bhas an area 22 which comprises the indicators.An exemplary configuration of the region 22 is shown with the region 22 a. The area 22 aincludes four indicators 26, 27, 28 and 29. the indicators 26 to 29 are planar areas of the area 22 a. Next to each of the indicators 26 to 29, a writing which is permanently visible to the naked eye and characterizes the respective indicator is arranged. A letter "5 Gy" characterizes the indicator 26; a letter "10 Gy" characterizes the indicator 27; a letter "15 Gy" characterizes the indicator 28; and a letter "20 Gy" characterizes the indicator 29. However, when the dose of X-ray applied to the indicators 26 to 29 exceeds a limit value indicated by the respective font, the transparency of the respective indicator changes, which then changes in gray.In the example of the region 22 a, all indicators 26 to 29 are gray, but in different degrees of form. Since the indicator 29 which is in this state from an X-ray dose of 20 Gy is gray, it can be seen that an X-ray dose of 20 Gy has acted on the applicator 17 b. However, if the indicator 29 is still transparent, but the indicator 28 is gray, this means that an X-ray dose of at least 15 Gy but less than 20 Gy has acted on the applicator 17b. In this way, the X-ray dose applied to the applicator 17b can be detected and visually recognized with the naked eye.The area 22 bshows an alternative configuration of the area 22 with the indicators 26 to 29. the indicators 26 to 29 of the area 22 bcorrespond to the indicators 26 to 29 of the area 22 a, however, the writings characterizing the respective indicators are arranged within the flat areas of the respective indicators.The region 22 cis a further exemplary configuration of the region 22. the region 22 ccomprises four indicators 30, 31, 32 and 33 each with different sensitivity with respect to the applied X-ray radiation dose. The indicators 30 to 33 are in the form of a letter which indicates a limit value in each case. The indicators 30 to 33 are transparent, for example, if no x-ray radiation has acted on the indicators. In this state, it is easy to see that an X-ray dose of less than 5 Gy has acted on the applicator 17b. Once the X-ray dose applied to the indicator 30 reaches or exceeds the limit value of 5 Gy represented by the font, the indicator 30 changes color grayish. As a result, the writing becomes visible with the naked eye, and it can be seen that an X-ray dose greater than the limit value represented by the writing has acted on the applicator 17 b. The same applies to the indicators 31 to 33.In the situation of the area 22c shown in Figure 4, the writings 5 Gy, 10 Gy and 15 Gy are visible, i.e. the indicators 30, 31 and 32 have turned from transparent to grey. The indicator 33, which changes from the transparent to grey with a limit value of 20 Gy, is still transparent, which means that the radiation dose applied to the applicator 17 bis less than 20 Gy. Accordingly, it can be easily judged that the radiation dose applied to the applicator 17 bis between 15 Gy and 20 Gy.

Claims

Applicator (17; 17a; 17b) for protecting a medical radiation therapy device (2) when the radiation therapy device (2) is introduced into a body to be treated, wherein the applicator (17; 17a; 17b) comprises: an applicator body (19), which can be placed on the radiation therapy device (2) and can be mechanically connected to the radiation therapy device (2), having at least one X-ray radiation-sensitive indicator (23 to 33), wherein the at least one indicator (23 to 33) is configured such that at least one optical property of the at least one indicator (23 to 33) changes permanently in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator (23 to 33).Applicator (17; 17a; 17b) for protecting a medical radiation therapy device (2) when inserting the radiation therapy device (2) into a body to be treated, wherein the applicator (17; 17a; 17b) comprises: an applicator body (19), which can be placed on the radiation therapy device (2) and can be mechanically connected to the radiation therapy device (2), having at least one X-ray radiation-sensitive indicator (23 to 33), wherein the at least one indicator (23 to 33) is configured such that at least one optical property of the at least one indicator (23 to 33) changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator (23 to 33), wherein the at least one indicator (23 to 33) comprises a radiochrome film.Applicator (17; 17a; 17b) for protecting a medical radiation therapy device (2) when inserting the radiation therapy device (2) into a body to be treated, wherein the applicator (17; 17a; 17b) comprises: an applicator body (19), which can be placed on the radiation therapy device (2) and can be mechanically connected to the radiation therapy device (2), having at least one X-ray radiation-sensitive indicator (23 to 33), wherein the at least one indicator (23 to 33) is configured such that at least one optical property of the at least one indicator (23 to 33) changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator (23 to 33), wherein the at least one indicator (30 to 33) has a writing which is visible to the naked eye, if the X-ray radiation dose applied to the at least one indicator (30 to 33) is greater than a limit value designed for the respective indicator (30 to 33) and which is not visible to the naked eye if the X-ray radiation dose applied to the at least one indicator (30 to 33) is less than the limit value designed for the respective indicator (30 to 33).Applicator (17; 17a; 17b) according to one of Claims 1 to 3, wherein the at least one indicator (23 to 33) is configured such that the absorption spectrum and / or the reflection spectrum of the at least one indicator (23 to 33) changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator (23 to 33).Applicator according to one of Claims 1 to 4, wherein the at least one indicator (23 to 33) is arranged on the applicator body (19) such that the at least one indicator (23 to 33) is perceptible to the naked eye.The applicator according to any one of claims 1 to 5, wherein the at least one indicator (23 to 33) lies on or below a surface of the applicator body (19).Applicator according to one of Claims 1 to 6, wherein the at least one indicator (23 to 33) is sensitive to X-ray radiation in the energy range from 10 keV to 250 keV; and / or wherein the at least one indicator (23 to 33) is largely insensitive to light in the visible spectral range.Applicator according to one of Claims 1 to 7, wherein the applicator body (19) has a tubular, elongate shape.Applicator according to one of Claims 1 to 8, wherein the at least one indicator (30 to 33) is transparent in the visible spectral range if no X-ray radiation has acted on the at least one indicator (30 to 33), and the transparency of the at least one indicator (30 to 33) decreases with increasing radiation dose acted on the at least one indicator (30 to 33).The applicator according to any one of claims 1 to 9, wherein the at least one indicator (30 to 33) has a writing that is visible to the naked eye when the X-ray dose applied to the at least one indicator (30 to 33) is greater than a threshold value designed for the respective indicator (30 to 33), and that is not visible to the naked eye when the X-ray dose applied to the at least one indicator (30 to 33) is less than the threshold value designed for the respective indicator (30 to 33).Applicator according to one of Claims 1 to 10, wherein the applicator body (19) has a plurality of indicators (24 to 33) which differ from one another and are configured such that an optical property of the indicators (24 to 33) changes to different extents in the visible spectral range as a function of an X-ray radiation dose acting on the indicators (24 to 33).A radiotherapy system (1) comprising: an applicator (17; 17a; 17b) according to any one of claims 1 to 11; and the radiotherapy apparatus (2) configured to generate X-ray radiation (9) for irradiating a body to be treated.Radiation therapy system (1) according to claim 12, wherein the radiation therapy device (2) comprises a main body (3) with a tube (5) extending away from the main body (3), wherein the tube (5) is inserted into the body to be treated for irradiation of the body to be treated, and wherein the applicator body (19) of the applicator (17; 17a; 17b) is fittable onto the tube (5).The radiation therapy system (1) according to claim 12 or 13, further comprising: a stand (11) having at least one joint (13), wherein the stand (11) supports the main body (3) of the radiation therapy device (2).A radiation therapy system (1) comprising: an applicator (17; 17a; 17b) for protecting a medical radiation therapy device (2) upon insertion of the radiation therapy device (2) into a body to be treated; and the radiation therapy device (2) configured to generate X-ray radiation (9) for irradiation of the body to be treated; wherein the applicator (17; 17a; 17 b) comprises: an applicator body (19), which can be placed on the radiation therapy device (2) and mechanically connected to the radiation therapy device (2), having at least one X-ray radiation-sensitive indicator (23 to 33), wherein the at least one indicator (23 to 33) is configured such that the absorption spectrum and / or the reflection spectrum of the at least one indicator (23 to 33) changes in the visible spectral range as a function of an X-ray radiation dose acting on the at least one indicator (23 to 33), wherein the at least one indicator (23 to 33) lies on or below a surface of the applicator body (19), wherein the applicator body (19) has a tubular, elongate shape; wherein the radiation therapy device (2) comprises a main body (3) with a tube (5) extending away from the main body (3), wherein the tube (5) for irradiating the body to be treated is inserted into the body to be treated, and wherein the applicator body (19) of the applicator (17; 17a; 17b) can be placed on the tube (5).

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