Regulation device for dose limiting of radiation source

Abstract

The invention relates to a control device (7) for dose limiting of a radiation source (2) which generates radiation (R) by means of a radiation generator (5), comprising: a radiation sensor (8) which is designed to measure an intensity (D) of the radiation (R) of the radiation source (2); a control unit (9) which is designed to control the intensity (D) of the radiation (R) emitted by the radiation source (2), the control device (7) being designed to control the radiation (R) of the radiation source (2) in a defined time period shorter than 2 ms after the measurement on the basis of the measurement of the radiation sensor (8). The invention also relates to a medical system and a method.

Description

Technical Field

[0001] The present invention relates to a control device for dose limiting of a radiation source, a medical system for imaging and / or for radiotherapy, and a method for dose limiting of a radiation source in a medical system. Background Technology

[0002] In medical applications involving high-energy radiation such as X-rays, electrons, or protons, patients must not be exposed to excessively high doses. Generally, therefore, it is essential to systematically ensure, for example in X-ray radiography, that the maximum dose rate (locally defined) at a reference point is not exceeded, for example, the air kerma rate, or the dose, for example, the air kerma. Specific limits on air kerma currently do not exist due to technological limitations. This also results in extremely different dose benefits depending on the radiator's use and aging, making it impossible to simply infer the applied dose from the current of the radiation generator.

[0003] In X-ray systems, current methods rely on a dosimetry chamber (AEC chamber, AEC: "Automatic exposure control") to determine the detector input dose based on the patient and use the signal to cut off X-ray radiation. This method is highly error-prone due to technological limitations and mechanical factors, as the patient must be positioned very precisely. Furthermore, the sensitivity of the AEC chamber does not correspond to the sensitivity of the CsI plane detector, requiring the two measurement systems to be calibrated against each other.

[0004] Precise real-time measurement of dose or dose rate is currently technically impossible. To meet standards, a slow DFP chamber (DFP: dose-area product) is alternatively chosen. The system transmits values ​​using only small samples (approximately 5ms). Due to the additional varying telegraph run time of 5ms to 50ms in the system bus, adjustments or averaging must be performed over multiple measurement points in order to determine a reliable value for the dose rate. Summary of the Invention

[0005] The purpose of this invention is to provide a dose-limiting device for radiation sources, a medical system for imaging and / or radiotherapy, and a method for dose-limiting radiation sources in medical systems, thereby avoiding the aforementioned drawbacks and achieving real-time radiation regulation.

[0006] This objective is achieved by the control device according to the invention, the medical system according to the invention, and the method according to the invention.

[0007] The control device according to the present invention is used for dose limiting of a radiation source, the radiation source generating radiation by means of a radiation generator. The control device includes the following components:

[0008] - A radiation sensor designed to measure the intensity of radiation from a radiation source.

[0009] - A control unit, the control unit being designed to control the intensity of radiation emitted by a radiation source, wherein the control device is designed to control the radiation of the radiation source based on measurements by a radiation sensor for a defined time period of less than 2 ms following the measurement.

[0010] First, the term "dose limitation" refers to a limitation on dose and / or dose rate. "Dose rate" is a chosen value and physically corresponds to power (W = J / s). Typically, air kerma rate is used to describe dose rate. "Dose" is a value summarized over time and physically corresponds to energy (J = W / s). Typically, air kerma rate is used to describe dose. Dose is the integral of the dose rate or the sum of measured dose rates.

[0011] Intuitively, it can be assumed that X-rays should not be too dense (not exceeding a specific maximum dose rate), and the "total dose," i.e., the dose within the examination range, should not be excessive. In pulsed radiation, it should also be noted that the "pulse dose," i.e., the dose produced by a single pulse, should not exceed its maximum value.

[0012] The control device according to the invention is preferably used for dose limiting of X-ray radiation sources; however, the invention is also advantageous for particle radiation sources. In particular, it is advantageous for controlling radiation sources that generate radiation for medical purposes or for examining sensitive objects by means of a radiation generator. This is suitable not only for imaging but also for treatment.

[0013] The control device includes a radiation sensor designed to measure the intensity of radiation from a radiation source. This can be, for example, an X-ray sensor with a scintillator and a photodetector. Radiation sensors are well known in the prior art. Instead of using only a single sensor, such as a diode-scintillator combination, it is entirely possible to use multiple different radiation sensors to efficiently measure rays, especially their spectrum. Preferably, but also possible, different pre-filter materials can be placed on top of multiple identical radiation sensors.

[0014] Furthermore, the control device includes a control unit designed to control the intensity of radiation emitted by the radiation source. This could be a unit that outputs a control signal, which could be processed by a control device for the associated radiation source, but it could also be a unit that controls the radiation source itself. Alternatively, the control unit could be designed to move a non-transmissive enclosure in front of the X-ray source or to use a grid pulse. The control signal could be a signal indicating that the radiation intensity must be reduced; in a simple embodiment, the control signal could simply be an off signal.

[0015] Basically, the control unit only needs to be able to output a signal that can be used to reduce or shut down the radiation. Corresponding control units are known in the prior art.

[0016] An important requirement for the control device is that it can regulate the radiation from the radiation source within a defined time period of less than 2 ms. To this end, its control unit must regulate the radiation source based on measurements from radiation sensors and perform the regulation faster than 2 ms after the measurement. Regarding pulsed radiation, the invention should be able to prevent the emission of a next pulse that would exceed the total dose when the maximum dose is reached.

[0017] In other words, the control device is preferably designed for real-time adjustment. The term "real-time" in this invention means adjustment with a defined delay of less than 2 ms, preferably less than 1 ms, and especially less than 0.8 ms. "Delay" refers to the time period between measurement and adjustment. "Defined" in this invention means also adhering to a delay. While adjustment within a time period shorter than the maximum delay is permitted, a time period longer than the maximum delay is not allowed. This must be achieved through technical means. In cases where signals are measured and processed in the nanosecond or microsecond range, achieving the maximum delay of 2 ms may not be easy; however, the forwarding channel used for adjustment should not be neglected. If real-time communication via said channel cannot be guaranteed, then the control device should not be designed for signal lines such as Bluetooth or WLAN.

[0018] The requirement for regulation within a defined time period of less than 2 ms involves technical measures related to the selection of components and their combinations. The feature "wherein the regulation device is designed to regulate the radiation of a radiation source within a defined time period of less than 2 ms following a measurement by a radiation sensor" is therefore synonymous with: the radiation sensor and regulation unit are configured and connected to each other, and the regulation channel of the regulation device is additionally designed to follow a preset time.

[0019] On the one hand, this relates to the measurement time TM of the radiation sensor. The radiation sensor must be designed such that its measurement time TM is very short, preferably less than 0.01 ms, especially less than 0.001 ms, and particularly preferably less than 500 ns. This can be easily achieved with conventional semiconductor sensors, as these measure in the nanosecond range.

[0020] Furthermore, this involves the transmission time TU, which is required for the measurement to travel from the radiation sensor to the control unit. A wired path should be chosen, but a faster wireless channel is also feasible. Additionally, the time used to digitize the measurement can optionally be added to the TU. Conventional analog-to-digital converters have conversion times of less than 0.01 ms. The transmission channel from the radiation sensor to the control unit should be selected such that the transmission time is less than 0.1 ms. This can be achieved wired and wirelessly, however sometimes without the aid of non-real-time methods such as Bluetooth or WLAN. However, standard radio connections can achieve the required time.

[0021] Similarly, for signal transmission, the output time TA of the control unit is relevant. This output time should also be less than 0.1 ms. Wired or wireless output is possible; however, it should not be achieved using methods that are not real-time compatible, such as Bluetooth or WLAN. However, standard radio connections can achieve the required time.

[0022] Regarding the control unit, it must perform computational operations. The control time TR required to generate the control signal from one or more measurement signals should be less than 1.5 ms, preferably less than 1 ms. Microcontrollers or FPGAs with fixed preset workflows are very suitable. Conventional processors can also be used if real-time processing is guaranteed.

[0023] The time interval T (delay, less than 2ms) given above is the sum of the given times (T = TM + TU + TR + TA). That is, the individual components should correspond to the given time selection or be interconnected in terms of data.

[0024] The medical system according to the invention is particularly used for imaging and / or radiotherapy. The medical system includes the following components:

[0025] - A radiation source with a radiation generator, and

[0026] -According to the present invention, the control device is designed to control the intensity of radiation emitted by a radiation source.

[0027] The control device is designed to initiate the cutoff of the radiation source based on the measurement of the radiation sensor if the measurement is outside a preset value range.

[0028] Preferably, the radiation source is designed for pulsed radiation operation, and the control device is designed to control the radiation source so that it is cut off when the maximum dose is reached, especially before the next pulse is emitted.

[0029] Medical systems can be, for example, X-ray imaging systems, CT systems, mammography systems, fluoroscopy systems, or angiography systems. However, they can also be particle accelerators used for therapeutic purposes. The system must include a radiation source with a radiation generator. Such systems are well known.

[0030] The system is characterized by including a control device according to the invention, designed to control the intensity of radiation emitted by a radiation source. This can be control of the radiation generator, such as its energy supply. However, it can also include control of other components of the radiation source, such as radiation filters, collimators, apertures, or ray enclosures. In particle accelerators, controlling the magnetic field is also feasible.

[0031] The control device is designed to, based on the measured radiation sensor, begin reducing the radiation intensity or cutting off the radiation from the radiation source if the measurement is outside a preset value range. This can be achieved, for example, by reducing the radiation intensity, such as by reducing the tube current, cutting off the radiation generator, or interrupting the radiation.

[0032] Preferably, the radiation source is designed for pulsed radiation operation, and the control device is designed to control the radiation source so that it is cut off when the maximum dose is reached, especially before the next pulse is emitted.

[0033] In one exemplary case, there exists a total limit value for the total dose to be checked, but there are also pulse limits for the maximum pulse dose per radiation pulse and power limits for the maximum radiation power. These limits are designed so that they can be directly applied to the measurements of the radiation sensor. It is also clearly feasible to convert each measurement of the radiation sensor into a dose rate, such as air kerma rate. However, in this case, the limits are converted to measurements based on the maximum values ​​for dose or dose rate, respectively, to save computational costs.

[0034] The radiation sensor now measures values ​​(power values) at different times, i.e., multiple times per pulse and for all pulses. The measured values ​​within a pulse are summed to form a "pulse value," and all values ​​are summed to form a "total value." The individually measured values ​​are then compared to the power limit, and if a measured value exceeds the power limit, the radiation is cut off or its power is reduced. Furthermore, the pulse value is compared to the pulse limit, and if the pulse value exceeds the pulse limit, the radiation for the current pulse is cut off. Similarly, the total value is compared to the total limit, and if the total value exceeds the total limit, the radiation for the current inspection is cut off. It should be emphasized that real-time cutoff is performed, i.e., at least 2 ms after measurement. This allows for very rapid cutoff (or modulation).

[0035] The method according to the invention is used for dose limiting of a radiation source in a medical system for examination according to the invention. The method includes the following steps:

[0036] - The intensity of radiation from a radiation source is measured using a radiation sensor in the control equipment of a medical system, preferably wherein measurements are performed using a radiation sensor for different radiation pulses.

[0037] - Compare the measured strength and / or the integral or sum of the measured strengths with a certain number of preset limit values.

[0038] - If the preset limit value is exceeded: then the intensity of the radiation emitted by the radiation source is adjusted by the control unit of the medical system's control device, preferably, wherein the signal of the control unit is directly (within a reliable delay) transmitted to the radiation source.

[0039] Preferably, it is determined here:

[0040] - Whether the measurement exceeds a preset limit for the dose rate, and / or - whether the integral or sum of multiple measurements exceeds a preset limit for the total dose, and / or

[0041] - Whether the integral or sum of multiple measured values ​​during the radiation pulse exceeds a preset limit value for the pulse dose.

[0042] As described above in the embodiments, the intensity of radiation from the radiation source is measured using a radiation sensor of the medical system's control device. This is preferably performed multiple times at different time points. In pulsed radiation operation, multiple measurements should be performed within the pulse. That is, preferably, measurements (preferably multiple) are performed using a radiation sensor for different radiation pulses.

[0043] Then, the measured intensity (corresponding to dose rate) and / or the integral or sum of the measured intensity (corresponding to dose) are compared with a certain number of preset limit values. Here, it is possible to convert the measured value to dose or dose rate or to adapt the limit values ​​of dose or dose rate to the measured value.

[0044] If the preset limit value is exceeded, the radiation intensity is reduced or the radiation is cut off. This is done through the control unit of the control device. The control unit preferably sends a signal directly to the radiation source, for example, in the form of a cutoff command or as a numerical value for control purposes.

[0045] In this process, it is preferable to determine whether the measurement (corresponding to the power value) exceeds a preset limit value for the dose rate. Additionally or alternatively, it is preferable to determine whether the integral or sum (with respect to time) of the measurements of multiple measurements (corresponding to the dose) exceeds a preset limit value for the total dose. Additionally or alternatively, it is preferable to determine whether the integral or sum (with respect to time) of the measurements of multiple measurements during the radiation pulse (corresponding to the dose) exceeds a preset limit value for the pulse dose.

[0046] For example, in a collimator or at a ray generator, air kerma rate can be measured in real time using scintillators, such as scintillator ceramics like UFCs, as well as photodiodes and amplifier circuits (e.g., transimpedance amplifiers) and digital circuits. Measurements are preferably performed using time intervals of less than milliseconds (sub-millisecond sampling). This allows for direct limitation of air kerma rate.

[0047] By performing multiple measurements over a short period, the air kerma rate for each pulse in a series of recordings or fluoroscopic sequences can be determined directly by integrating or summing the air kerma rate with respect to the acquisition time, enabling reliable verification without lengthy X-ray conditioning processes. It is also possible to calculate the air kerma rate for individual X-ray pulses in X-ray radiographic applications. Therefore, it is feasible to shift from indirect measurements of air kerma rate (via a kW bypass) to direct measurement, offering advantages in accuracy and also taking into account radiator aging.

[0048] Based on the comparison of measurements (multiple checks) over a long period of time, the present invention can also be used to detect the aging process of a radiation-generating system and compensate for it by appropriate adjustments when operating the radiator, thereby causing an extended lifespan of X-rays.

[0049] Furthermore, it is also possible to use measurements to diagnose future radiation aging processes and predict failure times.

[0050] Similarly, the present invention can be used to detect arcings in radiators and other adverse interruptions in X-ray radiation, and can also be used for lifetime prediction or to describe radiation quality.

[0051] This invention can be implemented, in particular, in the form of a computing unit with suitable software. For this purpose, the computing unit can, for example, have one or more cooperating microprocessors. In particular, the microprocessor can be implemented in the computing unit as a suitable software program portion. The large-scale software implementation has the advantage that existing computing units can be easily added via software or firmware updates to operate according to the invention. In this regard, the objective is also achieved by a corresponding computer program product having a computer program that can be directly loaded into the storage device of the computing unit, the computer program having program segments to perform all the steps of the method according to the invention when the program is executed in the computing unit. In addition to the computer program, such a computer program product can optionally include additional components, such as document assemblies and / or additional parts, and hardware components, such as hardware keys (dongles, etc.) for using the software.

[0052] Computer-readable media, such as memory sticks, hard disks, or other transportable or fixed-mount data carriers, can be used to transport to and / or store at or within a computing unit a program segment of a computer program that can be read and executed by the computing unit.

[0053] Other particularly advantageous designs and improvements of the invention are derived in the following description, wherein the implementation of the method type can also be improved in a similar manner to the implementation of the device and the description portion, and the various features of different embodiments or variations can in particular be combined to form new embodiments or variations.

[0054] The preferred control device is designed to control the intensity of radiation emitted by the radiation source during a time period (delay) of less than 1 ms, preferably less than 0.8 ms, and preferably less than 0.5 ms after the measurement, based on a radiation sensor measurement. That is, the radiation must be cut off, for example, less than 0.8 ms after a limit value is exceeded. Preferably, in the case of pulsed radiation emission, the control device is designed to perform control during the measurement pulse, before emitting a predetermined number of N pulses after the measurement, preferably where N < 3. Preferably, the emission of the next radiation pulse is cut off after a limit value with respect to dose is determined to be exceeded.

[0055] The preferred control device is designed to store and evaluate multiple measurements of the intensity of radiation from a radiation source taken at different time points by a radiation sensor. Preferably, measurements are taken at time intervals shorter than 1 ms, particularly preferably shorter than 0.1 ms. Preferably, in the case of pulsed radiation, the pulses are measured multiple times at different time points. Alternatively or additionally, it is preferred to measure or determine multiple pulses in the case of pulsed radiation. Alternatively or additionally, it is preferred to perform measurements (for determining aging phenomena) during different inspections.

[0056] Preferably, the control unit is designed to control the intensity of radiation emitted by the radiation source based on the integral, sum, and / or time-varying curves of the measurements. Preferably, multiple measurements and control based on the measurements are performed within a defined time period for the delay (e.g., 2 ms).

[0057] Preferred control devices are designed to calculate dose rate, particularly air kerma rate, and / or to calculate dose, particularly air kerma, from values ​​measured by radiation sensors and determined calibration functions. The measured values ​​are preferably converted and adapted to dose values. The limiting values ​​can then be directly dose values, preferably the maximum total dose and / or the maximum pulse dose and / or the maximum dose rate.

[0058] Preferably, the control device is designed to first convert the value using a calibration function and then integrate it over a preset time period, or to first integrate and then apply the calibration function to the integration.

[0059] The preferred control device is designed to calculate the limit values ​​for the measured values ​​based on the dose rate, particularly the air kerma rate, and / or the dose, particularly the air kerma, and based on a determined calibration function. The limit values ​​are preferably converted and adapted to the measured values. The limit values ​​can then be directly the most reliable measured values ​​or the maximum sum or (with respect to time) integral of the measured values.

[0060] The preferred control device is characterized in that it is designed to extrapolate the intensity and / or dose of radiation from the radiation source based on the measured time-varying curve at later time points. In this regard, it is possible, for example, to consider increases in multiple measurements over a certain period and determine when a limit value is reached through the final, calculated increase. However, it is also possible to determine the aging of the radiation source by checking the increase.

[0061] Preferably, the control device is designed to perform multiple measurements over a time period. In this case, the control device is preferably additionally designed to check and determine the expected cutoff time of the radiation generator of the radiation source at a future time point. In particular, the timing of reaching the dose limit is determined based on the differences in successive measurement values.

[0062] Preferably, the control device is designed to perform multiple measurements during different inspections. In this case, the control device is preferably additionally designed to determine the aging of the radiation generator of the radiation source at future points in time. This can be derived from the continuous decrease in radiation intensity. However, it is also possible to identify arcings in the radiator and other interruptions in X-ray radiation, and the same knowledge is used for lifetime prediction.

[0063] The preferred control device is characterized in that the radiation sensor includes an ionization chamber (e.g., a semiconductor ionization chamber or an air ionization chamber). Alternatively or additionally, the radiation sensor includes a photoelectric sensor, such as a photomultiplier or photodiode, and optionally includes suitable amplification and digitization circuitry, preferably together with a scintillator. Preferably, the radiation sensor includes multiple photoelectric sensors, particularly multiple photoelectric sensors with different pre-filters. Preferably, the radiation sensor includes a dose sensor or a direct conversion sensor.

[0064] The preferred control device is designed for real-time wireless or wired communication between the radiation sensor and the control unit, and / or real-time wireless or wired communication to the component to be controlled via the control device. Transmissions must occur within a defined timeframe to adhere to defined delays. Since measurement and comparison also consume slightly more time, communication should be performed within less than 0.5 ms.

[0065] A preferred medical system is characterized in that the radiation sensor measures radiation either in or at the radiation generator, or in or at a collimator connected downstream of the radiation generator. The control device can be integrated into the collimator, at the output of the X-ray radiator, or even already integrated into the X-ray radiator.

[0066] Preferably, the radiation sensor measures the radiation at the edge of the radiation cone or measures the scattered radiation. The control device is then designed to control based on the measured radiation.

[0067] Particularly preferably, the control device is designed to cut off the radiation source if the measured dose rate exceeds a preset limit, and / or the integral or sum of the values ​​of multiple measurements exceeds a preset limit of the total dose, and / or the integral or sum of the values ​​of multiple measurements during the radiation pulse exceeds a preset limit of the pulse dose.

[0068] Preferably, the control device is designed to calculate a future time point for pulsed radiation where a preset limit for the dose or dose rate is exceeded, and to initiate the interruption of radiation from the radiation source before that limit is exceeded. Preferably, the control device is designed to interrupt radiation from the radiation source if a preset limit for the dose rate and / or total dose and / or pulsed dose is calculated to be exceeded.

[0069] Preferred medical systems include image detectors designed to detect radiation emitted by a radiation source for image recording, wherein the image detector is preferably used as a radiation sensor for a control device or for calibrating a radiation sensor. Preferably, the control device is designed to evaluate the detector grayscale values ​​of the image detector to control the radiation emitted by the radiation source or to calibrate the radiation sensor, preferably based on the average and / or median and / or other statistical measures of pixel values ​​in a predetermined or dynamically determined area of ​​the image detector.

[0070] The preferred method operates on pulsed rays from a radiation source. The method includes the following steps: - Measuring the intensity of the first N ray pulses from the radiation source using a radiation sensor and an image detector, particularly as the ray intensity gradually increases, wherein preferably N < 3, and preferably additionally measuring the current and / or voltage of the radiation generator.

[0071] - Determine a certain number of limit values ​​corresponding to the maximum dose rate and / or maximum total dose and / or maximum pulse dose used for the corresponding examination.

[0072] - The calibration and control equipment enables the comparison of radiation sensor measurements with a certain number of limit values.

[0073] -The intensity of the additional pulses was measured using a radiation sensor.

[0074] -Based at least on the measurement, determine whether one of a number of limit values ​​has been exceeded, and if so, then cut off the radiation.

[0075] The intensity of the first ray pulse from the radiation source can be used, for example, when setting up the radiation source. This pulse often does not have a final intensity, but this can be compensated for in calculations. Measurements of the current and / or voltage of the radiation generator can improve calibration.

[0076] The limiting values ​​can correspond to the maximum dose rate and / or the maximum total dose and / or the maximum pulse dose as described above, but these limiting values ​​can also be converted so that they can be directly compared with measured values ​​or the sum of measured values. The latter can save computation time.

[0077] In other words, the calibration of the control equipment can be performed to correspondingly calibrate the limit values ​​or calibrate the measured values. It should be noted that calibration is not only related to the system used, but also to the patient being examined. Limit values ​​can also be patient-related, which makes calibration very important.

[0078] For example, an X-ray system outputs a first pulse with a small dose. The detector value obtained by an image detector (e.g., a planar detector) at this dose is evaluated and correlated with a target detector grayscale value. The pulse dose of the pulse (in the absence of a patient) is known by a predicted amount. The relationship between the dose of the first pulse and the dose of a standard pulse is also known. A limiting value can then be determined using the measured detector grayscale value, for example, based on the radiation absorption through the patient or based on the patient's age (e.g., determining a smaller limiting value in the case of a child).

[0079] Now, assuming that the measured value of the radiation sensor of the control device according to the invention is in a fixed relationship with the detector gray value of the image detector (e.g., linear or according to a preset function), a calibration function can be determined, for example, illustrating how the measured value is related to the current dose rate.

[0080] In practice, the patient's maximum total dose, maximum dose rate, and maximum pulse dose may be related to general presets. Then, power limits and pulse limits can be determined based on these presets, and the total limit can be determined using measurements from an image detector. The limits can then be calculated overall to be comparable to the measured values, and with calibration using the image detector, adjustments can be made if the radiation exceeds the maximum dose rate or has reached the maximum pulse dose or maximum total dose.

[0081] Intensity measurements are, of course, performed via a general check to determine when the limit has been exceeded or is about to be exceeded. If the limit is exceeded or an assessment is made that the limit will be exceeded with the next pulse, then radiation is cut off.

[0082] Preferably, calibration is performed using a determined formula. For example, it can be determined that the dose rate in subsequent pulses is x times that of N radiation pulses. A fixed function can also be used to scale the measured values ​​in a matching manner according to the measured current or voltage of the radiation source.

[0083] Preferably, calibration is performed iteratively by measuring multiple pulses. Because the image detector operates in the image recording, its information can also be used continuously for calibration.

[0084] Preferably, calibration is calculated based on the measured radiant flux and / or radiant energy. Here, a fixed function can be used in relation to the corresponding variables, especially with information from the image detector. In particular, the image detector can provide information about the radiant flux and / or about the radiant energy.

[0085] Preferably, an AI-based method (AI: "artificial intelligence") is used in the method according to the invention. Artificial intelligence is based on the principles of machine learning and is typically performed using algorithms that have been trained and are capable of learning. The term "Machine Learning" is commonly used for machine learning, which also includes the principles of "Deep Learning." Trained machine learning models are particularly advantageous for predicting values ​​that are about to exceed limits. Even when training lasts for a considerable period, the trained model can still provide results very quickly (within the corresponding adjustment time TR). Attached Figure Description

[0086] The invention will now be described in detail again with reference to the accompanying drawings and embodiments. Here, in different drawings, the same parts are given the same reference numerals. The drawings are generally not to scale. The drawings show:

[0087] Figure 1 A rough schematic diagram of an X-ray imaging system is shown.

[0088] Figure 2 A radiation source having a control device according to the invention is shown.

[0089] Figure 3 A block diagram showing the method flow is provided.

[0090] Figure 4 A simplified diagram illustrating the process and function of the method is provided.

[0091] Figure 5 A simplified diagram showing the adjustment of the radiation pulse is shown. Detailed Implementation

[0092] In the following description, the X-ray imaging system 1 is considered to be a conventional X-ray device. However, in principle, the method can also be used in other medical systems 1 that record images or treat patients P by means of radiation R.

[0093] Figure 1 A rough schematic illustration shows an X-ray imaging system 1 as an example of a medical system 1, including an X-ray source 2 as an example of a radiation source 2 and an image detector 3. During X-ray recording, X-rays R pass through the patient P, such that radiation R is directed onto the opposing image detector 3.

[0094] Figure 2A radiation source 2 with a control device 7 according to the invention is shown. The radiation source includes a radiation generator 5 (here, an X-ray tube) and a collimator. The radiation generator 5 is disposed at the top and generates X-rays R during operation, which exit from above through an exit window 6. The range of the X-rays R is limited by a collimator plate 4, which is typically adjustable.

[0095] The control device 7 includes a radiation sensor 8, which in this example is positioned above the collimator plate 4 and measures the intensity D of the radiation R from the radiation source 2 in the portion of the X-ray cone that is to be recorded. The total intensity of the X-ray R can be inferred from the measured intensity, at least after calibration.

[0096] Furthermore, the control device 7 includes a control unit 9, which is designed to control the intensity D of the radiation R emitted by the radiation source 2. A radiation sensor 8 measures the radiation R of the radiation source 2, forwards the measurement to the control unit 9 (arrow below), and the control unit 9 directly controls the radiation generator 5 (arrow on the right) for a defined time period of less than 2 ms after the measurement.

[0097] Figure 3 Showing information about, for example, in Figure 1 The diagram shows a flowchart of a method for dose limiting of a radiation source 2 in a medical system 1.

[0098] In step I, the intensity D of the radiation R from radiation source 2 is measured using the radiation sensor 8 of control device 7 (see...). Figure 2 Here, measurements are performed for different radiation pulses using radiation sensor 8. The measured values ​​can be plotted as shown in the simplified diagram.

[0099] In step II, the recordings of image detector 3 are evaluated, particularly the detector grayscale values, and a calibration function K is calculated from them for the measured values ​​or for the limiting values. In the example shown here, a value for the air kerma rate should be determined from the measured values.

[0100] In step III, the measured value is converted together with the calibration function into a value for the air kerma rate. Then, the air kerma value L is determined, which may include the air kerma rate and / or air kerma.

[0101] In step VI, at least when the limit value has been exceeded, the intensity of radiation R emitted by radiation source 2 is adjusted by the adjustment unit 9 of adjustment device 7.

[0102] The following figures illustrate exactly how this works.

[0103] Figure 4A simplified diagram illustrating the flow and function of a method for dose limiting of a radiation source 2 in a medical system 1 is shown. In this example, the method operates using pulsed radiation R, which is depicted here as a pulse.

[0104] On the far left, radiation with a decreasing pulse is emitted. A calibration function K is determined from this pulse using an image detector (and its grayscale values), and the measurements of the radiation sensor 8 are calibrated using this calibration function K. Since the performance of the radiation at higher intensities is known, the calibration function can be scaled up to even higher intensities. If this is not feasible, calibration can be performed based on a standard pulse or the standard pulse can be used additionally for calibration.

[0105] The radiation sensor 8 now measures the intensity of a standard pulse during image recording or treatment and calculates the air kerma value L, such as the sum of multiple air kerma rates during a single pulse.

[0106] The air kerma value L is measured for each pulse and summed to form the air kerma (i.e., the total value).

[0107] After a certain number of pulses, it is determined that the total dose limit G has now been exceeded (represented by lightning). The control unit now shuts off the radiation source so that no further pulses are emitted (the dotted pulses should indicate the absence of additional pulses).

[0108] Figure 5 A simplified diagram of modulating radiation pulses is shown. Here, another feasibility of modulation is demonstrated. If in Figure 4 Examples of performance at the presence of a maximum total dose have already been shown; here, the feasibility of interrupting radiation R when the maximum pulse dose (the shaded area in the middle) or the maximum dose rate (above the dashed line on the right) is shown.

[0109] If multiple measurements are performed within a single pulse, it can be determined that the maximum pulse dose has been exceeded and the radiation source 2 (middle) for the pulse is cut off. It can also be determined that the maximum dose rate has been exceeded and the radiation source 2 (right) for the pulse is similarly cut off.

[0110] Finally, it should be pointed out again that the methods described in detail above are merely embodiments, and these embodiments can be modified by those skilled in the art in entirely different ways without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "one" does not exclude the possibility that the features involved may exist in multiple forms. Similarly, the term "unit" does not exclude the possibility that the component involved may be composed of multiple interacting sub-components that are optionally also spatially distributed. The term "multiple" should be interpreted as "at least one." Regardless of the grammatical gender of a particular term, persons of either male or female gender are included.

Claims

1. A control device (7) for dose limiting of a radiation source (2), the radiation source (2) generating radiation (R) by means of a radiation generator (5), the control device (7) comprising: - A radiation sensor (8), which is designed to measure the intensity (D) of the radiation (R) from the radiation source (2). - A control unit (9), which is designed to control the intensity (D) of the radiation (R) emitted by the radiation source (2). The control device (7) is designed to control the radiation (R) of the radiation source (2) for a defined time period of less than 2 ms after the measurement, based on the measurement of the radiation sensor (8).

2. The control device (7) according to claim 1, wherein the control device (7) is designed to control the intensity (D) of the radiation (R) emitted by the radiation source (2) in a time period of less than 1 ms, preferably less than 0.8 ms, and preferably less than 0.5 ms after the measurement by the radiation sensor (8). Preferably, the control device (7) is designed to perform the control when measuring the pulse in the case of pulsed emission of rays, before emitting a certain number of N pulses after the measurement, preferably where N < 3.

3. The control device (7) according to any one of the preceding claims, said control device (7) being designed to store and evaluate multiple measurements of the intensity (D) of the radiation (R) of the radiation source (2) taken by the radiation sensor (8) at different time points, preferably wherein: - Measure the pulse multiple times at different time points under pulsed radiation (R), and / or - To measure or determine multiple pulses in the case of pulsed radiation (R), and / or - Perform measurements during different inspections. Preferably, the control unit (9) is designed to control the intensity (D) of the radiation (R) emitted by the radiation source (2) based on the integral and / or time-varying curve of the measurement.

4. The control device (7) according to claim 3, wherein the control device (7) is designed to calculate the dose rate, especially the air kerma rate, and / or the dose, especially the air kerma, from the value measured by the radiation sensor (8) and the determined calibration function (K), or the control device (7) is designed to calculate the limit value (G) of the measured value based on the dose rate, especially the air kerma rate and / or the dose, especially the air kerma, and the determined calibration function (K). Preferably, the control device (7) is designed to first convert the value using the calibration function (K) and then integrate it over a preset time period, or to first integrate it and then apply the calibration function (K) to the integration.

5. The control device (7) according to claim 3 or 4, wherein the control device (7) is designed to extrapolate the intensity (D) of the radiation (R) of the radiation source (2) and / or the dose based on the measured time-varying curve at a later time point. Preferably, the control device (7) is designed for use with respect to the control device (7). - Perform multiple measurements during the inspection period and use them to determine the desired cut-off time point and / or - Perform multiple measurements in different inspections and use them to determine the aging of the radiation generator (5) of the radiation source (2) at future points in time.

6. The control device (7) according to any one of the preceding claims, wherein the radiation sensor (8) comprises an ionization chamber or an ionization chamber and / or comprises a photoelectric sensor, preferably together with a scintillator, preferably wherein the radiation sensor (8) comprises a plurality of photoelectric sensors, particularly a plurality of photoelectric sensors having different pre-filters.

7. The control device (7) according to any one of the preceding claims, the control device (7) being designed for wireless or wired real-time communication between the radiation sensor (8) and the control unit (9) and / or wireless or wired real-time communication to the component to be controlled via the control device (7).

8. A medical system, particularly a medical system for imaging and / or radiotherapy, comprising: - A radiation source (2) with a radiation generator (5), and - The control device (7) according to any one of the preceding claims, the control device (7) being designed to control the intensity (D) of the radiation (R) emitted by the radiation source (2), The control device (7) is designed to, based on the measurement of the radiation sensor (8), initiate a reduction in the intensity of the radiation source (2) or a cutoff of the radiation (R) if the measurement is outside a preset value range. Preferably, the radiation source (2) is designed for pulsed ray operation, and the control device (7) is designed to control the radiation source (2) such that the radiation source (2) is cut off when the maximum dose is reached, especially before the next pulse is emitted.

9. The medical system (1) according to claim 8, wherein the radiation sensor (8) measures radiation (R) in or at the radiation generator (5) or in or at the collimator (4) connected downstream of the radiation generator (5). Preferably, the radiation sensor (8) measures the radiation (R) or scattered radiation at the edge of the radiation cone (R), and the control device (7) is designed to perform the control based on the measured radiation (R). Particularly preferably, the control device (7) is designed to, if - Measure the dose rate exceeding a preset limit (G), and / or - The integral or sum of multiple measured values ​​exceeds the preset limit (G) of the total dose, and / or - The integral or sum of multiple measurements during a radiation pulse (R) exceeds a preset limit (G) for the pulse dose. Then cut off the rays from radiation source (2).

10. The medical system (1) according to claim 8 or 9, wherein the control device (7) is designed to calculate a future time point for pulsed radiation where a preset limit (G) of dose or dose rate is exceeded, and to initiate the cutting off of radiation from the radiation source (2) before the exceedance, preferably wherein the control device (7) is designed to cut off radiation from the radiation source (2) if the calculation results in exceeding a preset limit (G) of dose rate and / or total dose and / or pulse dose.

11. The medical system (1) according to any one of claims 8 to 10, comprising an image detector (3) designed for detecting radiation (R) emitted by the radiation source (2) for image recording, wherein the image detector (3) is preferably used as a radiation sensor (8) of the control device (7) or for calibrating the radiation sensor (8), Preferably, the control device (7) is designed to evaluate the detector grayscale value of the image detector (3) to control the radiation (R) emitted by the radiation source (2) or to calibrate the radiation sensor (8), preferably based on the average and / or median and / or other statistical measures of pixel values ​​in a predetermined or dynamically determined area of ​​the image detector (3).

12. A method for dose limiting of a radiation source (2) of a medical system (1) according to any one of claims 8 to 11 for examination, comprising the following steps: - The intensity (D) of the radiation (R) of the radiation source (2) is measured by means of the radiation sensor (8) of the control device (7) of the medical system (1), preferably wherein the measurement is performed by means of the radiation sensor (8) for different radiation pulses (R). - Compare the measured strength (D) and / or the integral or sum of the measured strength (D) with a certain number of preset limit values ​​(G). - If the preset limit value (G) is exceeded: then the intensity (D) of the radiation (R) emitted by the radiation source (2) is adjusted by the control unit (9) of the control device (7) of the medical system. Preferably, the signal of the control unit (9) is directly transmitted to the radiation source (2). Preferably, wherein: - Measure whether the dose rate exceeds the preset limit (G), and / or - Whether the integral or sum of the measurements from multiple measurements exceeds the preset limit (G) of the total dose, and / or - Whether the integral or sum of the measurements of multiple measurements during the radiation pulse (R) exceeds the preset limit (G) of the pulse dose.

13. The method according to claim 12, wherein the pulsed radiation operation of the radiation source (2) comprises the following steps: - The intensity (D) of the first N ray pulses of the radiation source (2) is measured using the radiation sensor (8) and the image detector (3), wherein preferably N < 3, and preferably additionally the current and / or voltage of the radiation generator (5) is also measured. - Determine a certain number of limit values ​​(G) corresponding to the maximum dose rate and / or maximum total dose and / or maximum pulse dose used for the corresponding examination. - Calibrate the control device (7) so that the measurements of the radiation sensor (8) can be compared with the certain number of limit values ​​(G). -The intensity (D) of another pulse is measured using the radiation sensor (8). -Based at least on the measurement, determine whether one of the given number of limit values ​​(G) has been exceeded, and if so, then cut off the radiation (R). Preferably, wherein - The calibration is performed using a defined formula, and / or - The calibration is performed iteratively using measurements of multiple pulses, and / or - The calibration is calculated based on the measured radiant flux and / or radiant energy.

14. A computer program product comprising instructions that, when executed by a computer, cause the computer to perform the steps of the method according to claim 12 or 13.

15. A computer-readable storage medium comprising instructions that, when executed by a computer, cause the computer to perform the steps of the method according to claim 12 or 13.

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