DE102014202950A1 - Readout electronics for a flat detector of an X-ray system - Google Patents

Abstract

The invention relates to a control method, a readout electronics unit (AE), an X-ray machine (100) and a control computer (20) for reading out a digital flat detector (D). For this purpose, it is provided based on a pre-recording (V) to carry out a saturation analysis in order to dissect the detector surface into two disjoint regions (1, 2). A first X-ray pulse (P1) is applied to the examination object (O) and then a region-specific partial readout (11) of the detector takes place only in the first region to produce a first image. Then a second pulse (P2) is applied to the object (O). In the next step, a readout (13) of the detector in the first area (1) and in the second area (2) to produce a second image (I2). This is followed by summing the first and second images (I1, I2).

Description

TECHNICAL AREA

The present invention is in the field of electronic controls for X-ray devices, and more particularly to a technique for reading a flat detector of an X-ray machine and controlling the X-ray machine.

The present solution can be used both in different flat panel detectors and in control units for X-ray systems.

BACKGROUND OF THE INVENTION

For several years, a trend has been observed in radiology, which is moving away from classical, analogue radiography and towards digital radiography. Different digital technologies can be used, based on flat detectors with integrated or external readout electronics. The flat panel detectors can be based on different technologies, in particular a direct and an indirect conversion of the X-rays. In the latter technique, indirect solid-state detectors convert incoming X-ray radiation into visible light using a scintillator, which in turn is converted from a layer of photodiodes to electrons. A capacitor stores the resulting charge. The capacitor can store the X-radiation converted into electrical charge in a spatially resolved manner and with the aid of an electronic circuit, each pixel can then be read out individually.

In direct flat-panel detectors, by contrast, the incident X-ray radiation which has been attenuated by the object to be examined is converted directly into electrical charge via a photoconductor (for example amorphous selenium), which can then be read out again by a corresponding read-out electronics. In both cases, an active matrix of readout elements (for example, thin-film transistors / TFT and photodiodes / TFD) is provided so that each pixel can be read out.

The photodiodes used can be manufactured in different ways, for example made of amorphous silicon or based on a CMOS technology.

In clinical X-ray applications (for example in mammography), a specific dynamic range of the detector is required. The range must be selected to cover the x-ray intensity detected at the detector, which is associated with a high attenuation of x-ray radiation (ie, "thick" or highly absorbing specimen areas) and those associated with low attenuation (ie "Thin" or little absorbing object areas). In mammography, depending on the thickness of the breast to be examined, fluctuations in intensity or in the intensity range occur in a photograph over 2 to 3 orders of magnitude. The lower bound of the dynamic range is limited by ensuring a sufficient SNR ratio. As an upper bound of the dynamic range, saturation effects that affect image quality are critical.

In particular, in diagnostic applications, it is essential to provide a high image quality. For this purpose, the generated useful signal must stand out clearly from the background noise (sufficient signal-to-noise ratio / SNR) and the detector must be operated above a lower saturation limit.

In the current in-use flat panel detectors, it proves to be problematic that only a limited dynamic range can be made available, especially in the case of highly voluminous examination objects.

GENERAL DESCRIPTION OF THE INVENTION

It is therefore an object of the present invention to provide a technical solution with which it is possible to increase the dynamic range of flat-panel detectors in order in particular to allow the examination of sufficiently different-absorbing examination object segments of sufficient quality. It should be possible to dispense with scattered grids. Furthermore, a sensitivity should also be adaptable for differently configured detector modes.

• – Erstellen einer Voraufnahme eines Objektes
• – Auf Basis einer Sättigungsanalyse der Voraufnahme: Zerlegen einer Detektorfläche hinsichtlich einer erwarteten Sättigung in zumindest zwei disjunkte Bereiche, umfassend einen ersten Bereich, der einen niedrigen Sättigungserwartungswert hat und einen zweiten Bereich, der einen hohen Sättigungserwartungswert hat
• – Ausführen einer Röntgenpuls-/Auslesesequenz, zumindest umfassend die Schritte:
• – Applizieren eines ersten Pulses einer Röntgenstrahlung auf das Objekt
• – Bereichsspezifisches Teil-Auslesen des Detektor nur im ersten Bereich zur Erstellung eines ersten Bildes
• – Applizieren eines zweiten Pulses der Röntgenstrahlung auf das Objekt
• – Auslesen des Detektors im ersten und im zweiten Bereich
• – Summieren des ersten und des zweiten Bildes.

The present invention is achieved by a control method for an X-ray machine for reading out a digital flat detector of the X-ray apparatus for scanning an object, comprising the following method steps:

• - Create a preview of an object
• Based on a saturation analysis of the pre-acquisition: decomposing a detector surface in terms of expected saturation into at least two disjoint regions, comprising a first region having a low saturation expectation value and a second region having a high saturation expectation value
• Performing an X-ray pulse / read-out sequence, at least comprising the steps:
• Applying a first pulse of X-radiation to the object
• - Area-specific partial readout of the detector only in the first area to produce a first image
• Applying a second pulse of X-radiation to the object
• - Reading the detector in the first and in the second area
• - summing the first and second images.

Furthermore, the invention is achieved by a readout electronics unit for reading out a flat detector of an X-ray machine for measuring an object according to the appended claims.

• – Einen Speicher zur Speicherung einer Voraufnahme eines Objektes
• – Eine Zerlegeeinheit, die dazu bestimmt ist auf Basis einer Sättigungsanalyse der Voraufnahme eine Detektorfläche hinsichtlich einer erwarteten Sättigung in zumindest zwei disjunkte Bereiche zu zerlegen, umfassend einen ersten Bereich, der einen niedrigen Sättigungserwartungswert hat und einen zweiten Bereich, der einen hohen Sättigungserwartungswert hat
• – Eine Schaltungseinheit zum Ausführen einer Röntgenpuls-/Auslesesequenz, zumindest umfassend eine Steuerungseinheit, die bestimmt ist zum: – Applizieren eines ersten Pulses einer Röntgenstrahlung auf das Objekt, – Zum bereichsspezifischen Teil-Auslesen des Detektors nur im ersten Bereich zur Erstellung eines ersten Bildes – Zum Applizieren eines zweiten Pulses der Röntgenstrahlung auf das Objekt – Zum Auslesen des Detektors im ersten und im zweiten Bereich
• – Einen Bildgenerator, der dazu bestimmt ist, ein Bild zu generieren durch Summieren des ersten und des zweiten Bildes der Schaltungseinheit.

According to one aspect of the invention, the readout electronics unit comprises:

• - A memory for storing a pre-recording of an object
• A decomposing unit intended to decompose a detector surface in terms of expected saturation into at least two disjoint regions based on a saturation analysis of the pre-recording, comprising a first region having a low saturation expectation value and a second region having a high saturation expectation value
• A circuit unit for executing an x-ray pulse / read-out sequence, at least comprising a control unit which is intended for: applying a first pulse of x-ray radiation to the object, for area-specific partial readout of the detector only in the first area for producing a first image, For applying a second pulse of the X-ray radiation to the object - For reading out the detector in the first and in the second area
• An image generator intended to generate an image by summing the first and second images of the circuit unit.

Furthermore, the object is achieved by an X-ray device with a flat detector and a readout electronics unit, as described above.

Furthermore, the invention is achieved with a control computer for an X-ray machine for controlling an X-ray source and a read-out process for a detector with a read-out electronics unit, as described above.

An important aspect of this invention is that the number of reads per pixel is minimized. The amount of electronic noise in the final pixel value increases with the number of reads and subsequent summation. In order to minimize the electronic noise, therefore, only pixels are to be read out, in which a saturation effect is to be expected.

The terms of this application are explained in more detail below.

The digital flat-panel detector can be designed differently and based on both a direct conversion technique and an indirect conversion technique. A flat detector is known, for example from the DE 10 2005 017 944 ,

The term "object" refers to tissues to be examined. In a preferred embodiment of mammography, the object is the female breast. Other embodiments relate to other body parts of a patient to be examined.

The pre-recording is a role model, which is analyzed for the purposes of the "actual" main recording in order to control the readout process.

According to a first variant of the invention, the pre-recording can be a pre-shot, which is used to determine the dose of the main image and which is usually carried out with a lower radiation dose than the actual X-ray image or the actual X-ray images. An example of a method in which a pre-shot image is also used to determine the dose for generating an X-ray image can be found in US Pat DE 10 2005 036 514 , According to a variant of the pre-shot is generated by all the pixels of the detector are read, but in which each adjacent blocks of, for example, 128 × 128 pixels are averaged. A mammography detector basically has a very high resolution of about 3500 × 2500 pixels. Due to the averaging (binning), a preshot image has a resolution of about 28 × 22 pixels in the above example. The averaging results in an acceptable SNR ratio, but also a poor spatial resolution. Pixel binning is a technique whereby each adjacent pixel or pixel area is combined for readout. It is used in the prior art flat panel detectors to improve the SNR ratio and increase the frame rate.

According to a second variant of the invention, only every xth pixel can be read out. Which and / or how many pixels are read out is configurable. Overall, only about (1 / x) ^ 2 pixels are read out. However, there is no averaging. In the example above, x = 10 results in: 350 × 200 pixels. The spatial resolution is clear higher than the pre-shot, but also clearly below the original image. The reading out of every xth pixel should basically not be applied to the pre-shot, but should be applied after the first field. The pre-shot, however, should be read completely, with finer Binnings than 128x128 are useful, eg 64 × 64, 32 × 32, ....

Combinations of the two variants may also be applicable.

The term "saturation analysis" is to be understood as meaning an analysis of the anticipated saturation with respect to the pixels of the pixel matrix. In a preferred embodiment, the respectively expected saturation (for a respective particular pixel point) is determined on the basis of radiation intensity values from the preliminary recording. Preferably, it is provided that, depending on the value of the expected saturation, the respective pixel point is assigned to one of two regions. The detector surface is thus decomposed into at least two disjoint regions, a first region and a second region, depending on an expected saturation. The first range is characterized by having a low saturation expectation value. A saturation expectation value is preferably determined to be low if the expected pixel value is in the range of 0% to 95% of the maximum pixel value. The second area is determined by including pixel points having a high saturation expectation value. A high saturation expect value is preferably when the expected pixel value is greater than 95% of the maximum pixel value. The saturation (expectation) value indicates two states: Either the detector is in saturation or not at the pixel. The saturation (expectation) value can therefore be called a discrete value.

Analyzing the pre-scan is preferably designed to measure when or how fast a particular pixel point of the detector is in saturation. Preferably, the saturation analysis comprises a determination in which area the detector is operated at the applied radiation dose above a saturation threshold. The saturation threshold can be uniformly configured in advance for each detector. Alternatively, it may even be configured on a per-pixel basis (for example, by means of a gain calibration card). Preferably, the subsequent X-ray pulse read-out sequence and the summation of the first and second images are performed only for the range operated above a saturation threshold. The saturation limit value is dependent on a radiation dose (measured in the detector recording plane). The radiation dose is recorded from a tube current time product, the so-called mAs value. The decomposition of the detector surface into two disjoint regions has the advantage that the subsequent readout of the detector after application of X-ray radiation can now be carried out in a region-specific manner.

The X-ray pulse / read-out sequence comprises steps for controlling and executing the X-ray process and steps for reading out the detector after applied radiation of the object located in the beam path.

The X-ray radiation to be applied for examination of the object can be split in a first pulse and in a second pulse. According to one aspect, the sum of the dose of the first pulse and the second pulse is identical to a total radiation dose to be applied. The division into the radiation to be applied can be configurable for the first pulse and for the second pulse. It is thus not absolutely necessary that the first pulse with 50% total radiation dose and the second pulse are also operated with 50% of the total radiation dose. Accordingly, another division, for example 70%, 30% or otherwise, may be possible. Furthermore, more than two pulses can be applied. The number of pulses correlates with the number of read-outs.

According to one embodiment of the invention, the decomposition is provided in two disjoint regions of the detector surface. Alternatively, in the case of more complex or larger organs, several areas can also be defined, of which at least one area-specific part is read out.

• 1. Ein bereichsspezifisches Detailauslesen und
• 2. Ein Auslesen des Detektors.

The process of reading out involves two processes:

• 1. A domain-specific detail readout and
• 2. Reading the detector.

In the first case, the detector is not completely read out (thus not over the entire irradiated or active detector surface), but only over a partial area. The subregion is in particular the first region in which a low saturation value is expected and in which a high radiation dose is detected. Basically, the saturation value or saturation expectation value is firmly correlated with a dose. In the case of a mammographic examination, the first region will coincide with an edge region of the breast to be examined, while the second region is characterized by the middle region of the breast and has a low radiation intensity value.

As mentioned above, the decomposition of the detector surface in the first and second regions is performed on the basis of the saturation analysis of the pre-recording. Alternatively or cumulatively, a can stored object model are accessed in order to specify based on the held object data, the decomposition of the detector surface or even further restrict (in the event that in addition a saturation analysis is to be performed). This proves to be particularly advantageous if the pre-shot has a low spatial resolution (what he has in reality today, since the image 128 × 128 is binned), the object model, for example, ensure that the breast outer edges smooth and not "pixelated "Can be visualized.

According to an advantageous development of the invention, it is provided that the sensitivity of the detector during the first area-specific partial readout and / or the second readout can be configured. The limitations of sensitivity require that even lower sensitivity must be set so as not to saturate when reading out. Basically, a low sensitivity causes only a low signal strength can be detected at a low radiation intensity, which is also disturbed by the electronic noise.

According to one embodiment of the invention, it is provided that its sensitivity can be set or adjusted before the first partial readout and / or before the second readout of the detector. It is usually preset that the detector has a low standard sensitivity. For example, if the first image has been applied after application of the first pulse of the total dose (for example, 50%), the first image is captured with this low sensitivity. In this case, none of the pixels will be in the saturation region. From this picture, the first area can be read out. Before reading the second area, the sensitivity of the detector can be increased by a factor to bring the detector in a high sensitivity mode. The factor is determined by measuring the pixel values of the object after the first pulse or on the first image or the pre-recording and comparing them with target pixel values or reference pixel values for agreement. The target pixel value is a setpoint that should be achieved to render an image of sufficient quality. The factor can then be determined accordingly so that the measured pixel value multiplied by the respective factor gives the target pixel value. The second pulse (for example 50%) is applied before the second readout. Now, the low saturation regions, ie, the first region (for example, the breast edge) will be in the saturation region, while the second region (eg, the breast center) having a high saturation value will have an increased signal-to-noise ratio. The increased signal-to-noise ratio is due to the increased sensitivity. Therefore, it is sufficient if only the second area is read out. However, it is also conceivable that the range of low sensitivity is also read out after the second pulse, as long as it is still below saturation. In order to achieve this, a spread of the sensitivity in the second pulse can be performed. In the subsequent summation process, the first image and the second image can be summed to produce a final clinical image.

According to a preferred embodiment, the summing may be weighted. Possibly. For example, the dose ratio (e.g., 70%: 30%) may be the basis for the weighting (ie, factor 70% / 50%: 30% / 50%).

The sensitivity of the detector can thus be set differently within an irradiation, so that the first pulse is read out with a different detector sensitivity than after the application of the second pulse. Thus, the generation of the image information can be performed even more flexible and accurate.

The first and second area does not necessarily have to be a contiguous organ section, but rather can also be composed of several partial areas.

The functional features, advantages or alternative embodiments mentioned in connection with the method are likewise to be transferred to the other claimed objects and vice versa. In other words, the subject claims (which are directed, for example, to a readout electronics unit and an X-ray machine) may also be developed with the features described or claimed in connection with the method. The corresponding functional features of the method are formed by corresponding physical modules, in particular by hardware modules, which are intended to perform the respective function.

The above-described embodiments of the method according to the invention can also be embodied as a computer program product with a computer program, wherein the computer is made to carry out the inventive method described above when the computer program is executed on the computer or on a processor of the computer.

An alternative task solution also exists in a computer program with computer program code for carrying out all method steps of the claimed or above-described method, when the computer program is stored on the computer program Computer is running. In this case, the computer program can also be stored on a machine-readable storage medium.

An alternative task solution provides a storage medium which is intended to store the computer-implemented method described above and is readable by a computer.

It is within the scope of the invention that not all steps of the method necessarily have to be performed on one and the same computer instance, but they can also be performed on different computer instances, e.g. on a readout electronics unit and / or on a control unit. The sequence of the method steps can also be varied if necessary.

In addition, it is possible that individual sections of the method described above in a salable unit and the remaining components in another salable unit - as a distributed system - can be performed.

DESCRIPTION OF THE FIGURES

In the following detailed description of the figures, non-limiting exemplary embodiments with their features and further advantages will be discussed with reference to the drawing. In this show:

1 a schematic overview of an X-ray device with a flat detector and a corresponding read-out electronics unit and a control unit according to a preferred embodiment of the invention,

2 FIG. 2 is a schematic overview of a sequence of an irradiation / readout process according to a preferred embodiment of the invention, FIG.

3 a schematic overview of a detector according to a preferred embodiment of the invention,

4 an overview-like constructive representation of a control unit according to an embodiment of the invention,

5 a schematic overview of a Ausleseelektronikeinheit according to an embodiment of the invention, and

6 a flowchart of the control method according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

With reference to 1 The following is a possible application of a control method for an X-ray machine 100 explained in more detail. The X-ray machine can be designed for a variety of uses, such as for mammography or other applications. Furthermore, the X-ray machine 100 be structured differently. In 1 is a C-arm X-ray machine shown. However, it is also within the scope of the invention to provide other X-ray device designs here. The X-ray device comprises at least one X-ray source Q, which is intended for the transillumination of an object O. Furthermore, the x-ray device comprises 100 a detector D with a corresponding read-out electronics unit AE. The X-ray system is powered by a control unit 20 controlled. The control unit 20 can work as a workstation in close proximity to the x-ray machine 100 be positioned and via a corresponding cable connection or via wireless interfaces with the X-ray machine 100 in the data exchange. The control unit 20 serves to control the X-ray machine 100 and in particular for reading out the X-ray radiation detected on the detector after transillumination of the patient or of an organ. Furthermore, the control unit 20 Take over further functionalities, in particular a control of a read operation of the detected signals of the detector D.

According to one embodiment of the invention, the readout electronics unit AE is integrated in the detector D or connected to the detector D via corresponding interfaces. In particular, a lowermost level of the read-out electronics, which responds to the respective pixels, is implemented on or at the detector D. A higher level, eg the disjoint areas 1 . 2 can fix on the control computer 20 to run. The latter is the preferred embodiment.

The detector D is a digital flat detector, preferably of amorphous silicon, and may comprise an active matrix of, for example, 40 × 40 cm with 3000 × 3000 pixels. Depending on the size and structure, different spatial resolutions can be achieved. The term "pixel" or "pixel" is understood as a combination of electronic components in the detector, in particular of photodiode and transistor with appropriate connections. The digital data acquired as a measurement signal from the detector D are then processed and usually stored in DICOM format (DICOM: Digital Imaging and Communications in Medicine) and forwarded to other computer-based instances (for example for post-processing, archiving and / or reporting ).

The invention proposes to increase the dynamic range of the detector D by detecting two X-ray images of the examination object O, in which the detector D does not reach its saturation limit and in which subsequently these acquired images are summed to form an overall image. In this case, not always the entire detector D or an entire detector surface DF of the detector D is read, but there is a region-specific partial read-out 11 of the detector D.

The following is with reference to 2 a possible procedure for a control method for controlling an X-ray pulse / read-out sequence is described.

In 2 is plotted on the abscissa of the time course. The detector D comprises a detector surface DF, which is intended to detect the X-radiation weakened by the object O. In 2 the control method is shown using the example of a mammographic examination. However, it is also within the scope of the invention to apply the control method also for other investigations. First, a pre-shot V of the object O is created. The pre-recording V is analyzed with regard to the detected saturation signals. In particular, a saturation analysis is performed to detect which detector areas are rapidly saturating and which detector areas are slower or out of saturation. The saturation analysis serves to separate the detector surface DF into at least two disjoint regions on the basis of the respective expected saturation (for the respective pixels) 1 . 2 relocate. The first area 1 is an area with a low saturation expectation value, and thus with a high radiation expectation intensity, and the second area 2 has a high saturation expectation value and thus a low radiation intensity value. After disassembling the detector surface DF in the first area 1 and the second area 2 an x-ray pulse / readout sequence is performed. For this purpose, a first pulse P1 of the X-radiation is applied. This is followed by a sector-specific partial readout 11 of the detector D only in the first area 1 to create a first image I1. This is followed by the application of a second X-ray pulse P2 in order subsequently to read out the detector D in order to produce a second image I2. After the generation of the two images I1, I2, the first image I1 and the second image I2 are summed to produce an overall image, which can then be further processed.

As in 2 In this example, the control method comprises two pulses P1, P2 and two read-outs, a region-specific partial read-out process 11 and another read-out process 13 , The second read-out process can preferably be carried out in the entire active image region of the detector surface DF. With this process, the dynamic range of the detector can be increased by detecting an intermediate image I1 having a low sensitivity value and detecting the second image I2 having a high sensitivity value.

The control method is thus based on a pulse mode for triggering the X-radiation. In this mode, the detector D is exposed to a series of different intensity x-ray pulses of short duration (for example in the range of 5-20 ms).

In a preferred embodiment, two pulses P1, P2 are provided and correspondingly two read operations of the detector D: A region-specific partial read-out process 11 and a readout process 13 in particular comprising the entire actively irradiated detector surface. However, it is also within the scope of the invention to provide more than two pulses and more than two application / read-out sequences. Thus, for example, it is possible to distribute the total radiation dose to three pulses and to trigger a region-specific partial readout of the detector D after the first and / or second pulse. The corresponding overall picture is then executed again by summing the respective sub-pictures. In this context, it should be pointed out that the first, second, n-th images do not relate to subareas of an examination subject, ie are not image sections, but are related to the detector surface DF of the detector D. In the first image I1, other detector regions (in particular only a part of the detector) are thus read out than in the second image I2. Furthermore, the first image I1 and the second image I2 may differ in that they have been read out with a different detector sensitivity. For this purpose, it may be provided that the sensitivity of the detector or detector area is changed before the read-out process. In particular, the sensitivity for area-specific partial readout 11 and sensitivity for reading 13 be different.

In the following, a possible sequence according to a preferred embodiment of the invention with respect to 6 explained in more detail.

In step 1000 For example, a pre-recording V of the female breast O is created. This is done in step 2000 a saturation analysis of the pre-recording V. The saturation analysis detects saturation expectation values for the different pixels of the detector D from the pre-recording V.

This is done in step 3000 a decomposition of the detector surface DF in the disjoint areas, in particular in the first area 1 and in the second area 2 , The first two, second areas 1 . 2 differ in their saturation values.

In step 4000 the first pulse P1 is applied in step 5000 a domain-specific partial readout 11 of the detector D only in the first area 1 with low sensitivity to create the first image I1.

Thereupon, in step 6000 the second pulse P2 is applied to the object O, and then in step 7000 the detector or the first area 1 and the second area 2 of the detector. This is preferably done in high sensitivity.

Thereupon can conclude in step 8000 the first image I1 and the second image I2 are summed to produce an overall image.

As in 3 As shown, the read-out electronics unit AE can be integrated directly in the detector D.

Likewise, it is possible for the readout electronics unit AE as a module in the control unit 20 to integrate. This is in 4 shown.

In alternative embodiments of the invention, mixed forms between the in 3 and 4 be provided variants shown. For example, it may be possible to provide part of the readout electronics unit AE in the detector D and another part of the readout electronics unit AE in the control unit 20 , Furthermore, it is possible, the Ausleseelektronikeinheit AE as a separate module the X-ray system 100 to join.

5 schematically shows the structure of a readout electronics unit AE. The readout electronics unit AE comprises a memory S, which is intended to store the captured images and in particular the pre-recording V. Furthermore, it includes a dismantling unit 12 which is intended to decompose the detector surface into the at least two disjoint regions. The decomposition is based on the saturation analysis of the useful signals of the Voraufnahme V.

Furthermore, the unit AE comprises a circuit unit 15 , which is intended to carry out the X-ray pulse / read-out sequence. The circuit unit 14 Applies the first pulse P1, controls the area-specific partial readout 11 of the detector D and controls the application of the second pulse P2 and the read-out process 13 , Furthermore, the read-out electronics unit AE comprises an image generator 16 which is intended to generate an overall image in which the first image I1 and the second image I2 of the circuit unit 14 be summed up.

In a preferred embodiment, the first pulse P1 and the second pulse P2 each carry 50% of the total radiation dose.

Alternatively, other ratios between first and second pulses P1, P2 can be set here.

In a preferred embodiment of the invention, it is provided to dispense with the pre-recording in order to keep the radiation dose for the patient as low as possible. In this case, a first image is generated with a first pulse, which is carried out with an estimated dose on the basis of the measured breast thickness. For this, the patent DE 10 2005 036 514 directed.

It is also within the scope of the invention to generate a first image I1 with low resolution by reading only a portion of the image after the first pulse P1. For example, it is possible to generate a low-resolution image by reading only every xth, eg, every tenth pixel in a pixel row and column from the detector D. This has the consequence that, for example, only 1% of the total image is read. The image thus generated then has a low resolution but a higher signal-to-noise ratio than a pre-pickup V and can also be used to image the detector surface DF into the at least two disjoint regions 1 . 2 to segment. Subsequently, as described above, the X-ray pulse / read-out sequence can then be carried out.

In summary, the present invention relates to a technique for increasing the dynamic range of the detector D by performing area-specific sub-readout 11 of the detector D is executed before the detector runs in these areas in a saturation. Thus, it can be avoided to read detector areas that are below a saturation threshold. The associated additional electronic noise can be avoided by a frame summing method. Furthermore, the sensitivity of the detector can be configured pulse-specifically. In other words, the first pulse P1 can be operated with a different sensitivity than the second pulse P2. 20

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005017944 [0017]
• DE 102005036514 [0020, 0071]

Claims (15)

Control method for an X-ray machine ( 100 ) for reading out a digital flat detector (FD) of the X-ray apparatus ( 100 ) for measuring an object (O), comprising the following method steps: - producing a preliminary image (V) of an object (O) - based on a saturation analysis of the preliminary image (V): decomposing a detector surface (DF) with respect to an expected saturation into at least two disjoint ones Areas comprising a first area ( 1 ), which has a low saturation expectation value and a second region ( 2 ), which has a high saturation expectation value - performing an X-ray pulse / read-out sequence, comprising at least the steps: - applying a first pulse (P1) of X-radiation to the object (O) - region-specific partial readout of the detector (D) only in the first region ( 1 ) for producing a first image (I1) - applying a second pulse of the X-ray radiation to the object (O) - reading out the detector in the first (I1) 1 ) and in the second area ( 2 ) - summing the first (I1) and the second image (I2).  A control method according to claim 1, wherein, based on the saturation analysis of the pre-scan (V), it is measured in which region the detector (D) is operated above a saturation threshold at the applied radiation dose, the subsequent steps of performing the x-ray pulse / read sequence and summing only be executed for this area.  A control method according to claim 1, wherein the area-specific partial readout is performed with a low sensitivity value and the readout with a high sensitivity value.  Control method according to one of the preceding claims, in which the method accesses a stored object model in order to limit the decomposition of the detector surface on the basis of the retained object data. The control method of claim 1, wherein the pre-recording (V) is detected as a pre-shot with a pre-shot dose that is less than a total dose.  A control method according to claim 5, wherein the pre-shot is generated by reading all the pixels of the detector and averaging respectively adjacent blocks of configurable edge length pixels from an image thus formed.  Control method according to Claim 1, in which, after a first partial image, not every pixel of the detector (D) but every x-th pixel is read out.  Control method according to one of the preceding method claims, in which the sum of the first pulse (P1) and the second pulse (P2) corresponds to the total radiation dose. Control method according to one of the preceding method claims, wherein the ratio of the applied radiation dose of the first and second pulses (P2) is configurable. Control method according to one of the preceding method claims, wherein a sensitivity of the detector (D) is configurable and in particular in selectable portions of the detector (D) is differently configurable, so that in particular increases a partial sensitivity, and a different partial sensitivity are lowered.  Control method according to one of the preceding method claims, in which a sensitivity of the detector (D) for applying the first pulse (P1) and / or for applying the second pulse (P2) and / or for carrying out a pre-recording is also each differently configurable , Control method according to one of the preceding method claims, in which the summing ( 8000 ) is weighted. Read-out electronics unit (AE) for reading out a flat detector (D) of an X-ray machine ( 100 ) for measuring an object (O), comprising: - a memory (S) for storing a preliminary image of an object (O) - a decomposing unit ( 12 ), which is intended, on the basis of a saturation analysis of the pre-recording, to decompose a detector surface with regard to an expected saturation into at least two disjoint regions, comprising a first region ( 1 ), which has a low saturation expectation value and a second region ( 2 ), which has a high saturation expectation value - A circuit unit ( 14 ) for executing an X-ray pulse / read-out sequence, at least comprising a control unit ( 20 ), which is intended for: - application of a first pulse (P1) of X-radiation to the object (O), - for area-specific partial readout of the detector (D) only in the first region to produce a first image (I1) - for application a second pulse (P2) of the X-ray radiation on the object (O) - For reading the detector (D) in the first and in the second region - an image generator ( 16 ), which is intended to generate an image by summing ( 8000 ) of the first and the second image (I1, I2) of the circuit unit ( 14 ). X-ray machine ( 100 ) with a flat detector (D) and a readout electronics unit (AE) according to claim 11. Control computer ( 20 ) for an X-ray machine ( 100 ) for controlling an X-ray source (Q) and a read-out process for a detector (D) with a read-out electronics unit (AE) according to claim 11.

Images