DE102013225581A1 - Method and device for individual adaptation of parameters of an X-ray flat detector - Google Patents

Abstract

The invention relates to a method for imaging by means of an X-ray device and an X-ray device. The X-ray device has an X-ray source and a spatially resolving X-ray detector with a location-dependent adjustable sensitivity. The method comprises the steps of: detecting a first set of location-dependent detection values by means of the spatially-resolving X-ray detector with a low radiation quantity; Determining a second set of expected location-dependent detection values upon irradiation with a higher amount of radiation by means of the first amount; Adjusting the location-dependent sensitivity of the spatially resolving X-ray detector as a function of the expected detection values of the second set, such that upon irradiation of the spatially resolving X-ray detector with the higher radiation amount the detection values occupy a value range between a predetermined lower limit and a predetermined upper limit and detecting a third amount spatially resolved detection values by means of the spatially resolving X-ray detector with the higher radiation quantity.

Description

The invention relates to a method for imaging by means of an X-ray source and a spatially resolving X-ray detector, wherein a set of spatially resolved detection values is detected by means of the spatially resolving X-ray detector with a predetermined radiation dose. The invention further relates to a spatially resolving X-ray detector and an X-ray device having an X-ray source, the spatially resolving X-ray detector and a controller for carrying out the method.

X-ray devices for examining the human body have been known for a long time. Due to the harmful effect of X-radiation, it has also been tried for a long time to minimize the radiation dose during an examination.

This request is opposed by the fact that with decreasing radiation dose, the signal-to-noise ratio of an image detected by a detector decreases. This is particularly hindering when a high contrast ratio is required in order to be able to detect changes in areas of different radiation quantity with only slightly different absorption behavior. This is particularly important in mammography since, due to the different thickness of the transilluminated tissue layer, the basic weakening in central regions is greatly different in comparison to edge regions.

In order to increase the contrast, grids have been used in the past to absorb scattered radiation, which in turn also absorbs some of the imaging radiation and requires a higher dose of radiation during imaging. Alternatively, it was attempted to compensate for the scattered radiation in the evaluation of the detector signals and the image formation. However, this requires a particularly high dynamic range of the detector signals, which has been improved in the prior art by adapting the overall sensitivity of the detector or the downstream signal processing to the radiation dose and the expected mean weakening of the tissue.

The object of the present invention is thus to improve the image quality of an X-ray device with the lowest possible radiation dose.

The object of the invention is achieved by an inventive method for imaging by means of an X-ray source according to claim 1, a spatially resolved X-ray detector according to the invention according to claim 7 and an X-ray device according to the invention for carrying out the method according to claim 10.

The method according to the invention for imaging an examination subject is carried out by means of an X-ray source, a spatially resolving X-ray detector with a location-dependent adjustable sensitivity and a control. In the method according to the invention, the examination object is arranged between the X-ray source and the X-ray detector. In a step of the method, a first set of location-dependent detection values is detected by means of the spatially-resolved low-dose X-ray detector. As a low radiation amount, a radiation amount is considered, which generates a signal over the entire surface in the X-ray detector under the recording conditions, which is detectably above a noise signal of the detector, but clearly, that is for example by a factor of 2, 5 or 10 under a saturated signal of the X-ray detector lies. 5 mAs are a typical value for the tube current-time product that produces such a radiation dose.

In a further step, a second set of expected location-dependent detection values is determined upon irradiation of the examination subject with a higher radiation quantity by means of the first set. This can be done for example by a predetermined formula or extrapolation.

In one step, the location-dependent sensitivity of the spatially resolving X-ray detector is adjusted as a function of the expected detection values of the second set such that upon irradiation of the spatially resolving X-ray detector with the higher radiation quantity, the detection values assume a value range between a predetermined lower limit value and a predetermined upper limit value. Preferably, the lower limit value is determined by a signal value of a dark noise of the X-ray sensor plus a dynamic reserve. Preferably, the upper limit value is determined by a saturation value of the X-ray sensor minus a dynamic reserve. For example, the dynamic reserve is 1, 5, 10 or 20 percent of a dynamic range between saturation and dark noise. The higher radiation quantity is an amount of radiation which is a multiple of the low radiation quantity and does not exceed the legal limit values for an X-ray examination. For example, the higher amount of radiation is 10, 20 or 50 times the low amount of radiation.

The method further comprises the step of detecting a third set of location-dependent detection values by means of the spatially-resolving X-ray detector with the higher radiation quantity.

The method according to the invention advantageously makes it possible to adjust the sensitivity of the spatially resolving X-ray detector location-dependent in such a way that the largest possible dynamic range of the output signal is achieved and in this way an advantageous high image quality can be achieved in the subsequent image processing, without a higher amount of radiation being required.

The object of the invention is also achieved by the spatially resolving X-ray detector of claim 7. The spatially resolving X-ray detector according to the invention has a multiplicity of detector elements. The detector elements are associated with a plurality of detector areas. The detector areas may have a few or even hundreds or thousands of detector elements. It is also conceivable for the detector areas to divide the radiation-sensitive area of the X-ray detector into geometric areas, for example squares, quadrilaterals, polygons, concentric rings, circle segments or similar shapes. In particular, it may be that the regions simulate the geometry of a cross section of an examination object. The spatially resolving X-ray detector according to the invention furthermore has means for setting a first sensitivity of detector elements in a first detector area independently of a second sensitivity in a second detector area.

Advantageously, in the spatially resolving X-ray detector according to the invention, it is possible to adapt the sensitivity to the radiation dose to be expected and thus to achieve the greatest possible dynamic range of the measured values and an improved useful signal-to-noise ratio.

Finally, the object according to the invention is achieved by the X-ray device of claim 10, which has the required features and is designed to carry out the method according to the invention of claim 1. The X-ray device according to the invention therefore also shares the advantages of the method.

Advantageous developments of the invention are specified in the subclaims.

In one possible embodiment of the method according to the invention, a segmentation of the first quantity takes place for determining the second quantity.

A segmentation makes it possible to incorporate knowledge of the geometry of the object to be examined, for example, in mammography, knowledge of the shape and physicochemical properties of the breast, in determining the second set of the expected detection values. Thus, advantageously even with a first set of detection values having a high noise due to a small amount of radiation used for recording, it is possible to make a reliable prediction of the expected detection values of the second set and thus the sensitivity of the X-ray detector optimally adjust the actual examination.

In a conceivable embodiment of the method according to the invention, the step of determining a second set of expected location-dependent detection values by means of extrapolation in dependence on a ratio of the higher radiation quantity to the lower radiation quantity.

Advantageously, an extrapolation of the expected measured values as a function of the ratio of the radiation quantities is easy to implement, requires little computational effort and simply models the physical causes.

In one possible embodiment of the method according to the invention, the step of determining a second set of expected location-dependent detection values comprises a local filtering of the first set of spatially resolved detection values and / or location-dependent derived values thereof. Local filtering can be done, for example, by linear filters such as Gaussian filters or non-linear filters such as bilateral filters or median filters.

The local filtering of the first set or values derived therefrom advantageously forms the continuous change in absorption due to the large-scale geometric properties of the object to be examined and makes it possible to advantageously reduce small-scale disturbances such as detector noise by filtering over locally adjacent values.

In one conceivable embodiment of the method according to the invention, a fourth set of calibration values for detector elements of the spatially resolving X-ray detector is determined for a first predetermined radiation dose and calibration values of the third set are calibrated by means of the calibration values of the fourth set.

Advantageously, the inclusion of calibration values for individual detector elements allows for their individual characteristics and deviations to be taken into account when determining the second quantity and thus to achieve better results in the imaging.

In one possible embodiment of the method according to the invention, a fourth set of spatially resolved detection values for a first predetermined radiation dose and a fifth set of spatially resolved detection values for a second predetermined radiation dose are detected. From this, a sixth set of spatially resolved detection values for a third predetermined dose of radiation is interpolated from the fourth set and the fifth set, and the detection values are calibrated using the sixth set.

The inclusion of two calibration values at different radiation levels allows not only a zero offset for each detector element, but also a different sensitivity in the determination of the expected detection values to take into account and thus make the setting of the spatially resolved sensitivity of the X-ray detector even more accurate.

In a conceivable embodiment of the spatially resolving X-ray detector according to the invention, the means for the spatially resolving setting of a sensitivity of the spatially resolving X-ray detector are adjustable capacitances on detector elements of the spatially resolving X-ray detector.

Adjustable capacitances advantageously enable an averaging of the signal and thus a reduction of the noise component.

In a conceivable embodiment of the spatially resolving X-ray detector according to the invention, it is also conceivable that each detector area has separate read-out means for the detection values of the detector elements and the sensitivity of the detector elements of the detector area can be controlled via the read-out means.

By means of the read-out means, the sensitivity for the detector elements of a detector area can advantageously be adjusted jointly.

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they will be achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be described in detail in conjunction with the drawings.

Show it:

1 a schematic representation of an X-ray device according to the invention;

2 a schematic flow diagram of a method according to the invention for imaging;

3 a schematic representation of a spatially resolving X-ray detector according to the invention;

4 a schematic representation of a spatially resolving X-ray detector according to the invention;

5 a schematic representation of an exemplary means for adjusting a sensitivity of a detector element and

6 a schematic representation of an exemplary read-out means for adjusting a sensitivity of a detector element.

The 1 shows an X-ray device according to the invention 1 for imaging in a schematic representation. The X-ray device according to the invention 1 has an X-ray source 10 , as a spatially resolving X-ray detector, an X-ray flat detector 20 as well as a power supply 30 and a controller 40 on. The X-ray source 10 and the X-ray flat detector 20 are arranged relative to each other so that in the inventive operation of the X-ray source 10 X-radiation on the X-ray flat detector 20 falls. Between the X-ray source 10 and the X-ray flat detector 20 is a research object 50 in close proximity to the X-ray flat detector 20 can be arranged, so that the X-ray radiation through the examination subject 50 on the X-ray flat detector 20 falls and produces a sharp image there.

The X-ray flat detector 20 is designed by means of areal distributed detector elements 22 two-dimensional spatially resolved to provide values for a received radiation amount of X-radiation. Furthermore, the X-ray flat detector 20 designed so that the sensitivity of individual or groups of detector elements 22 is adjustable. Thus, the size of a signal is variable, the X-ray compartment detector 20 for a detector element 22 for a predetermined amount of X-ray radiation. In this way it is possible to increase the dynamics of the detector element 22 adapt, ie the range of radiation quantities is variable, for which the detector element 22 provides a minimal signal over a noise floor and for which it provides a maximum signal that goes into saturation.

The groups of detector elements 22 are detector areas 21 of the spatially resolving X-ray detector 20 preferably associated with a contiguous area on a radiation-sensitive surface of the X-ray detector 20 form. In 3 and 4 examples of spatially resolving X-ray detectors according to the invention are shown schematically. Such areas 21 may have a square shape or a rectangular shape. It is also conceivable that the detector areas 21 emulate the geometry of an object to be examined. Thus, an inventive X-ray detector 20 for example, detector areas 21 in the form of concentric semicircles corresponding to the attenuation behavior of an examined breast, which is lowest in a nearly semicircular zone at the edge.

The sensitivity can be achieved, for example, by a variable capacitance on a detector element 22 be set as it is in 5 is shown. It is conceivable that this capacitance integrates the detector signal and thus the capacitance influences the signal level for a certain amount of radiation.

But it is also possible that the sensitivity via readout means 23 for the detector elements 22 is set. In this sense, the sensitivity of a detector element 22 also as the ratio of the output signal of a detector area 21 for a detector element 22 to the output of a detector area 21 for the respective detector element 22 understand in which the detector element 22 is arranged.

Are the detector elements 22 a detector area 21 arranged in rows and columns, these columns and rows are not necessarily arranged at right angles and / or parallel in a rectangle, the sensitivity can be adjusted for example by a readout amplifier for a line or the whole area. The number of rows by columns may be 256 × 256 or 32 × 32 detector elements, for example. With the gain set high, even weak signals from a high-attenuation range for X-ray radiation are scaled to larger amplitude values, making full use of a subsequent ADC in its dynamic range. It is also conceivable that in the read-out means 23 already a threshold or offset is subtracted, for example, to compensate for dark noise.

6 shows an exemplary circuit for a read-out means 23 , The detector elements 22 a detector area 21 are connected via a multiplexer MUX and a resistor R to an inverting input of an amplifier OP. In a negative feedback branch from an output of the amplifier OP to the inverting input of the amplifier OP, a variable resistor is a digital-to-analog converter DA whose resistance value is controllable via a signal input and thus the total gain of the read-out means 23 changed. This is also the sensitivity of the detector elements 22 controllable with the readout means 23 are connected.

It is also possible that a detector element 22 or the read-out means 23 Having means over which the period of time over which integrates the detector signal from the X-ray radiation, in other words, the exposure time of each pixel or a detector area 21 can be adjusted. However, it would also be conceivable that the integration time is controlled from the outside, for example by individual detector elements or detector areas 21 be read out after different integration times.

In one embodiment of the flat-panel x-ray detector, the area of a detector element could also be 22 be variable by the detector element 22 for example, is divided into individual subpixels and adjustable different to the signal of the detector element 22 contribute.

The X-ray device 1 also has a controller 40 on that in first signal connection 46 with a high voltage source 30 stands, in turn, the X-ray source 10 over the supply line 31 energized and controlled. The control 40 This way it is able to get one from the X-ray source 10 emitted X-ray source in a radiation duration and radiation intensity control, so the controller 40 one from the X-ray source 10 can affect emitted radiation.

Furthermore, the controller is 40 with an X-ray flat detector 20 in second signal connection 45 , Via the second signal connection 45 is the controller 40 capable of location-dependent detection values for radiation quantities from the X-ray flat detector 20 to receive and, as to the X-ray flat detector 20 described the sensitivity for individual detector elements 22 or detector areas 21 of the X-ray flat detector 20 to be set depending on location. The location dependence of the detection values will be described below by way of example by x and y coordinates of a respective detector element in the area of the x-ray area detector 20 described.

The control 40 has a processor 41 and a program memory 42 and a data store 43 on. The processor 41 executes the instructions in the program memory 42 from which the controller is designed, the X-ray device 1 according to the method described below. The data store 43 Among other things, it is designed to have a plurality of location-dependent detection values of the flat-panel X-ray detector 20 to save the control 40 via the signal connection 45 receives. Furthermore, the controller 40 able to be in the data store 43 stored values for the location-dependent sensitivity via the signal connection 45 in the X-ray flat detector 20 adjust.

2 is a schematic flow diagram of the inventive method again, as for example by the controller 40 is performed in the X-ray device. It is also conceivable that the method is performed by another technical device.

In a step S10, at one between the X-ray source 10 and the X-ray detector 20 in the beam path inventively arranged examination object 50 a first set of location-dependent detection values by means of the spatially resolving X-ray detector 20 detected with a low amount of radiation. The controller controls this 40 the high voltage source 30 via the signal connection 46 such that the x-ray source 10 emits a low amount of radiation.

As a low radiation amount in the context of the invention, a radiation amount is referred to in the X-ray surface detector 20 generates a signal that is above a dark noise of the X-ray area detector 20 lies. As dark noise here is a signal level called the X-ray surface detector 20 produced without irradiation by X-radiation under the same conditions (eg same exposure time, temperature). With the low radiation quantity, the X-ray surface detector delivers 20 a location-dependent detector signal, which already has an imaging of the examination subject 50 allowed. The low radiation quantity is assumed to be an amount of radiation which is a fraction of the radiation quantity which is usually used during an imaging examination of the examination subject 50 is used, for example 1, 5, 10 or 20 percent. Also, the low radiation level is a fraction of a legal legal limit for investigation. For example, a numerical value for the tube current-time product may be given as 5 mAs.

In a step S20, the control determines a second set of expected location-dependent detection values during irradiation of the examination subject 50 and the X-ray flat detector 20 with a higher amount of radiation by means of the first amount. As a higher amount of radiation is here a radiation amount referred to, as is customary in the prior art for such investigations. However, it is also conceivable that the higher radiation quantity is clearly, for example one third or one half lower than the usual amount of radiation, since the method according to the invention makes it possible in particular to reduce the radiation quantity with an equivalent examination result.

In one possible embodiment, the controller determines the amount of second expected detection values by extrapolation using the first set of location-dependent detection values at a low radiation level. For this purpose, for example, a location-dependent detection value of the first quantity may simply be multiplied by a factor which results from the ratio of the amount of the higher radiation quantity divided by the amount of the low radiation quantity. In other embodiments, other extrapolations are also conceivable, for example by higher-order polynomials or other analytical or numerical functions. The functions used preferably model the characteristic curve of the X-ray area detector 20 ,

In one embodiment of the invention uses the controller 40 Information about the geometry of the examination object 50 , The location-dependent detection values have a high noise component with the low radiation quantity. Their influence can be reduced by segmenting the first location-dependent detection values. In this case, for example, a parameterized model of the examination object 50 are adapted to the first detection values and then the second set of the expected detection values are determined by means of the parameterized model by means of the higher radiation quantity and the absorption values to be expected in the model. Parameters can be, for example, the position in the x and y coordinates, the radius, the maximum thickness and the density with regard to the x-ray absorption. Since the parameters represent an average over a plurality of location-dependent detection values of the first set, the signal-to-noise ratio is substantially improved.

In one possible embodiment of the method according to the invention, it is also conceivable that in step S20 first the detection values of the first set are spatially filtered. This can be done, for example, by bilinear filtering with respect to the x and y coordinates of the location-dependent detection values of the first set. However, other two-dimensional filter functions are also conceivable, such as e.g. Gaussian filter or bilateral or median filter.

In a step S30, the location-dependent sensitivities of the X-ray area detector become 20 depending on the expected detection values of the second set from the controller 40 customized. If a determined expected detection value of the second quantity for a detector element is small, then the controller sets 40 about the signal connection 45 a higher sensitivity for the detector element. On the other hand, if a determined, expected detection value of the second quantity for a detector element is large, then the controller sets 40 via the signal connection 45 a lower sensitivity for the detector element. In the foregoing description of the X-ray area detector 20 are options for changing the sensitivity specified.

In this case, the sensitivity is set in such a way that, upon irradiation of the spatially resolving X-ray detector 20 with the higher radiation amount, the detection values occupy a range of values between a predetermined lower limit value and a predetermined upper limit value. In principle, the detection values can be between a minimum value for a dark noise and a saturation value for the detector element, in which the detection value no longer increases with the radiation quantity. In order to achieve maximum dynamics and resolution, the sensitivity is set so that expected detection values occupy the largest possible area between these two extremes. It is advantageous if a certain dynamic reserve is provided, ie the expected detection values are between the dark noise plus the dynamic reserve and the saturation value minus the dynamic reserve, in order to avoid overdriving and resulting artifacts. For example, the dynamic reserve may be 5, 10 or 20 percent of the difference of saturation and dark noise detection values. When adjusting the sensitivity, empirical values continue to be obtained about small-scale absorption differences in the examination subject to be reproduced by the examination in the pictorial representation 50 one. The sensitivity is being set up so that these detection values are just distributed over the range between the upper and lower limits.

In a step S40, a third set of spatially resolved detection values is then obtained by means of the spatially resolving X-ray detector with the higher radiation quantity with the set location-dependent sensitivity in the X-ray area detector 20 detected.

The detected spatially resolved detection values are corrected to a pictorial representation according to the set sensitivities in the further processing, so that the brightness values of a pixel essentially correspond to a number of detected X-ray quanta. For example, the detection value may be multiplied by a reciprocal of the sensitivity set for each detector element in step S30.

Furthermore, corrections according to individual tolerances of individual detector elements are conceivable, for example an offset caused by dark noise or a production-related deviation in a basic sensitivity, ie a sensitivity of the detector element with an identical setting of the location-dependent sensitivity. Such tolerances can be obtained by determining a fourth set of location-dependent detection values, for example, in the dark or by irradiation with a predetermined, over the area of the X-ray flat detector 20 detected with a constant or at least known radiation intensity and used to correct the third set of location-dependent detection values by subtracting an offset or multiplying a correction factor.

In one embodiment of the method according to the invention, it is also conceivable that, furthermore, a fifth quantity of location-dependent detection values is detected under changed conditions compared to the fourth quantity. For example, the fourth set of location-dependent detection values may be detected in the dark, while the fifth set when irradiated at a predetermined, across the area of the X-ray flat detector 20 known radiation intensity is detected. In this way, the basic sensitivity of each detector element can be approximated, for example, by a linear function.

This individual sensitivity function of each detector element can then be used, for example, in step S20 for a more accurate determination of an expected location-dependent detection value, and thus more precisely adapted to the location-dependent sensitivity in step S30. It is also conceivable that the sensitivity function is used directly in step S30 for adjusting the location-dependent sensitivity for an expected detection value. Finally, the sensitivity function can also be used to correct the detected third set of spatially resolved detection values.

It is also possible to apply other image processing techniques to the detected detection values, such as filtering, logarithmic, contrast enhancement or image enhancement algorithms.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (11)

Method for imaging an examination subject ( 50 ) by means of an X-ray source ( 10 ) and a spatially resolving X-ray detector ( 20 ) with a location-dependent adjustable sensitivity, wherein the examination subject ( 50 ) between the X-ray source ( 10 ) and X-ray detector ( 20 ), the method comprising the steps of: (S10) detecting a first set of location-dependent detection values by means of the spatially resolving X-ray detector ( 20 ) with a low amount of radiation; (S20) determining a second set of expected location-dependent detection values during irradiation of the examination subject ( 50 ) with a higher amount of radiation by means of the first amount; (S30) Adjusting the location-dependent sensitivity of the spatially resolving X-ray detector ( 20 ) as a function of the expected detection values of the second quantity, such that upon irradiation of the spatially resolving X-ray detector (FIG. 20 ) with the higher radiation amount, the detection values occupy a range of values between a predetermined lower limit value and a predetermined upper limit value; (S40) detecting a third set of spatially resolved detection values by means of the spatially resolving X-ray detector ( 20 ) with the higher amount of radiation.  The method of claim 1 wherein segmenting of the first set occurs to determine the second set.  Method according to one of the preceding claims, wherein the step of determining a second set of expected location-dependent detection values by means of extrapolation in dependence on a ratio of the higher radiation amount to the lower radiation amount.  Method according to one of the preceding claims, wherein the step of determining a second set of expected location-dependent detection values comprises a local filtering of the first set of spatially resolved detection values and / or location-dependent values derived therefrom. Method according to one of the preceding claims, wherein the method further comprises the step of: detecting a fourth set of calibration values for detector elements of the spatially resolving X-ray detector ( 20 ) for a first predetermined radiation dose and correcting the detection values of the third set by means of the calibration values of the fourth set.  A method according to any one of claims 1 to 4, wherein a fourth set of spatially resolved detection values for a first predetermined radiation dose and a fifth set of spatially resolved detection values for a second predetermined radiation dose is detected therefrom, from which a sixth set of spatially resolved detection values for a third predetermined radiation dose from the fourth set and the fifth set are interpolated and the detection values are calibrated using the sixth set. Spatial resolution x-ray detector ( 20 ) with a plurality of detector elements ( 22 ), wherein the detector elements ( 22 ) a plurality of detector areas ( 21 ) and the spatially resolving X-ray detector ( 20 ) Means, a first sensitivity of the detector elements ( 22 ) of the X-ray detector ( 20 ) in a first detector area independent of a second sensitivity of detector elements ( 22 ) in a second detector area. Spatial resolution x-ray detector ( 20 ) according to claim 7, wherein the sensitivity of detector elements ( 22 ) of an area by means of adjustable capacitances at the detector elements ( 22 ) is controllable. Spatial resolution x-ray detector ( 20 ) according to claim 7 or 8, wherein each detector area ( 21 ) separate readout means ( 23 ) for the detector elements ( 22 ) and the sensitivity of the detector elements ( 22 ) via the read-out means ( 23 ) is controllable. X-ray device ( 1 ) for imaging an examination subject ( 50 ), wherein the X-ray device ( 1 ) an X-ray source ( 10 ), a spatially resolving X-ray detector ( 20 ) according to one of claims 7 to 9 and a controller ( 40 ), wherein the X-ray device ( 1 ) is designed for imaging the object to be examined ( 50 ) between the X-ray source ( 10 ) and X-ray detector ( 20 ) to arrange; where the controller ( 40 ), a first set of spatially resolved detection values by means of the spatially resolved X-ray detector ( 20 ) to detect with a low amount of radiation; where the controller ( 40 ) is adapted to determine a second set of expected spatially resolved detection values upon irradiation with a higher amount of radiation by means of the first set; where the controller ( 40 ), a location-dependent sensitivity of the spatially resolving X-ray detector ( 20 ) as a function of the expected detection values of the second set, such that upon irradiation of the spatially resolving X-ray detector (FIG. 20 ) with the higher radiation amount the detection values between a predetermined lower limit and a predetermined upper limit. X-ray device ( 1 ) according to claim 10, wherein the controller ( 40 ) of the X-ray device ( 1 ) is designed, by means of the X-ray device ( 1 ) a fourth set of calibration values for detector elements ( 22 ) of the spatially resolving X-ray detector ( 20 ) for a first predetermined amount of radiation and to calibrate the detection values of the third quantity by means of the calibration values of the fourth quantity.

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