DE102012202608B4 - Method for performing an x-ray examination on an x-ray machine - Google Patents

Abstract

wobei UF ein Umrechnungsfaktor ist, der zu jeder Anoden/Filter-Kombination zum Aufnehmen (S503) des ersten Bildes für eine Anoden/Filter-Kombination des zweiten Röntgenbildes ermittelt wird, und wobei mAs HE bzw. mAs LE das Röhrenstromzeitprodukt für eine Hochenergieaufnahme bzw. Niedrigenergieaufnahme bezeichnen;
- Aufnehmen (S507) eines zweiten Röntgenbildes oder eines Tomographiescans mit einer zweiten Energie, d.h. als Hochenergieaufnahme, in Abhängigkeit des zweiten Einstellungsparameters.

A method for performing an X-ray examination with a dual-energy technique on an X-ray machine (100), which has an AEC detector, which is arranged between an object to be examined and an X-ray detector, with the following steps:
- determining (S501) a first setting parameter by means of a pre-recording, wherein the pre-recording is performed by means of an AEC method;
- recording (S503) a first X-ray image or a tomographic scan with a first energy, ie as a low-energy intake, in dependence on the first adjustment parameter;
Determining (S505) a second adjustment parameter by means of the first X-ray image or tomography scan by evaluating the X-ray image obtained during the acquisition (S503) of the first X-ray image in the form of a low energy acquisition, the second adjustment parameter being a difference value between a desired value of a blackening and an actual value of the Blackening of the first X-ray image is determined; and wherein a correction factor (KF) is determined by evaluating the first X-ray image so that the second adjustment parameter for recording (S507) of a second X-ray image results from $$\text{mAs\_HE}=\text{UF * * KF mAs\_LE}\text{.}$$

wherein UF is a conversion factor determined for each anode / filter combination for capturing (S503) the first image for an anode / filter combination of the second X-ray image, and wherein mAs HE and mAs LE are the tube current time product for a high energy intake or low energy intake;
- recording (S507) a second X-ray image or a tomography scan with a second energy, ie as a high-energy intake, as a function of the second adjustment parameter.

Description

The present invention relates to a method for performing an X-ray examination on an X-ray apparatus, a corresponding X-ray apparatus and a computer program for a computer for carrying out the method.

In today's x-ray devices, a calibration measurement is carried out before an x-ray image for calibrating the x-ray device, by means of which a setting parameter for the subsequent x-ray exposure can be determined. If two x-rays are taken, a calibration is performed for each of these x-rays. Therefore, in an X-ray study with two images of different energy, such as in a dual-energy tomosynthesis, two calibration measurements are performed. If, in addition, a determination of the contrast agent kinetics, a further calibration measurement is necessary. The high number of calibration measurements expose the patient to increased radiation exposure.

The US 2010/0232669 shows an approach to optimize settings in a dual-energy imaging based on a pre-recording, but without the use of Automatic Exposure Control (AEC) technology.

The US Pat. No. 7,826,587 B1 also relates to a dual-energy method, wherein by means of a pre-recording, the signal-to-noise ratios for the subsequent recordings in several iterations can be optimized.

The US 7,657,000 B2 shows an approach with which a conventional CT device can be operated as a dual-energy device.

The US 2002/0075997 A1 discloses an optimized dual energy imaging using the AEC technique and the evaluation of a pre-recording in order to keep the dose burden as low as possible for subsequent recordings.

It is the object underlying the invention to reduce the radiation exposure during an X-ray examination.

This object is achieved by objects according to the independent claims. Advantageous developments of the invention are specified in the description, the figures and the subclaims.

According to a first aspect, the object according to the invention is achieved by a method for carrying out an X-ray examination on an X-ray apparatus, comprising the steps of determining a first adjustment parameter by means of a pre-acquisition, taking a first X-ray image or a tomography scan with a first energy as a function of the first adjustment parameter; and recording a second x-ray image or tomography scan with a second energy in response to the first adjustment parameter. As a result, not only the technical advantage is achieved, for example, that the radiation exposure is reduced, but also that the examination time is shortened and work processes are simplified.

The X-ray machine is a device for examining tissue or an object by means of X-rays.

The step of determining a setting parameter is a technical determination of the setting parameter, for example based on a measurement performed by the X-ray machine.

The adjustment parameter is a parameter used to set the device during X-ray exposure. In general, the adjustment parameter may be a mAs value, a tube current value, a tube voltage value, a recording time value, or any other technical parameter that may be used to set an X-ray.

A photograph is an examination of the tissue or the object by X-rays. A pre-acquisition may include determining a radiation intensity after passing through the tissue or the article (transmission) by means of a sensor.

An X-ray image is the imaging of the tissue or the object by means of X-rays on an image surface. The image surface may be formed by an X-ray film or an X-ray detector.

A tomographic scan is an imaging method for the examination of the tissue or the object by means of X-rays, in which sectional images or tomograms are used, by means of which the internal spatial structure of the object can be determined and displayed in the form of sectional images, slice images or tomograms. Such methods are referred to, for example, as computed tomography or X-ray tomography.

An energy refers to the energy under which the X-ray image is taken.

In one embodiment, the method of the first aspect includes the steps of determining a second adjustment parameter using the first x-ray image or tomography scan and taking the second x-ray image with a second energy in response to the first and second adjustment parameters. As a result, for example, the technical advantage is achieved that a particularly accurate value can be determined for the second image, which is based on a broader starting data base. This will improve the quality of the second shot.

According to a second aspect, the object according to the invention is achieved by a method for carrying out an x-ray examination on an x-ray device, comprising the steps of determining a first adjustment parameter by means of a pre-acquisition, taking a first x-ray image or a tomography scan with a first energy as a function of the first adjustment parameter, determining a second adjustment parameter using the first X-ray image or tomography scan and taking a second X-ray image or a tomography scan with a second energy as a function of the second adjustment parameter. As a result, for example, the technical advantage is achieved that can be determined with simple steps, a setting parameters for the second shot.

According to the invention, the second energy is higher than the first energy. As a result, for example, the technical advantage is achieved that first the patient is charged with a low radiation dose, based on the then a setting parameter for a recording with a high energy is determined. This improves the safety of the process.

In a non-inventive embodiment according to the first or the second aspect, the second energy is lower than the first energy. By taking a picture with a high energy image, for example, the technical advantage is achieved that a setting parameter can be determined very accurately.

In an advantageous embodiment of the invention according to the first or the second aspect, the method further comprises the step of setting a mAs value for the acquisition of the first and / or second X-ray image as a function of the first and / or second adjustment parameter. As a result, for example, the technical advantage is achieved that an easy-to-influence and to-change value of the X-ray machine is used as a setting parameter.

The mAs value is the product of X-ray tube current in milliamps (mA) and the time taken to record in seconds (s).

According to the invention, the method further comprises the step of calculating the mAs value for the acquisition of the second X-ray image by multiplying the mAs value for the first X-ray image by a factor. As a result, for example, the technical advantage is achieved that the adjustment parameter can be determined in a particularly simple manner.

In a further advantageous embodiment of the invention according to the first or the second aspect, the factor depends on a filter used in the recording. As a result, the technical advantage is achieved, for example, that the adjustment parameter can be determined particularly precisely taking into account certain examination conditions.

An X-ray filter or pre-filter may be, for example, a metal plate attached to the X-ray examination between the X-ray tube and the object, which absorbs certain parts of the spectrum emitted by the X-ray tube.

In a further advantageous embodiment of the invention according to the first or the second aspect, the factor depends on an anode used in the recording. As a result, for example, the technical advantage is also achieved that the adjustment parameters can be determined particularly precisely taking into account certain examination conditions.

An x-ray anode is part of the x-ray tube. From the X-ray cathode electrons are emitted (emitted) and accelerated by a high voltage (25-150 kV) to the anode. There, the electrons penetrate into the anode material and are decelerated. Depending on the anode material used, the spectrum of the X-ray radiation changes.

In a further advantageous embodiment of the invention according to the first or the second aspect, the factor depends on a dose value applied during the recording. As a result, for example, the technical advantage is achieved that the accuracy of the adjustment parameter improves even further.

The dose is the energy absorbed per unit mass.

In a further advantageous embodiment of the invention according to the first or the second aspect, the factors for filters, anodes and / or dose values are stored in a non-volatile memory. As a result, for example, the technical advantage is achieved that once stored values can serve as the basis for a setting parameter determination in a multiplicity of different measurements.

A nonvolatile memory (non-volatile, for persistent data storage) is a memory (or a semiconductor device, such as an EPROM) that can store data for an extended period of time without data loss.

According to a third aspect, the object according to the invention is achieved by an X-ray machine which is set up to carry out the method according to the first or second aspect. The X-ray device comprises an AEC detector and an X-ray detector 103 , This achieves the same technical advantages as the method according to the first or second aspect.

According to a fourth aspect, the object according to the invention is achieved by a computer program which is stored on a data carrier or on a memory of a computer and which comprises computer-readable instructions which are intended for carrying out the method according to the first or the second aspect, if the commands are executed on the computer. This also achieves the same technical advantages as with the method according to the first or second aspect.

Embodiments of the invention are illustrated in the drawings and will be described in more detail below.

• 1 eine schematische Darstellung des erfindungsgemäßen Verfahrens;
• 2 ein Diagramm für eine Röhrenausbeute bei einer niedrigen und einer hohen Energie bei unterschiedlichen Filtern;
• 3 ein Blockdiagramm einer ersten Ausführungsform mit Teilaspekten des erfindungsgemäßen Verfahrens;
• 4 ein Blockdiagramm einer zweiten Ausführungsform mit Teilaspekten des erfindungsgemäßen Verfahrens; und
• 5 ein Blockdiagramm einer dritten Ausführungsform mit Teilaspekten des erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic representation of the method according to the invention;
• 2 a diagram for a tube yield at a low and a high energy with different filters;
• 3 a block diagram of a first embodiment with partial aspects of the method according to the invention;
• 4 a block diagram of a second embodiment with partial aspects of the method according to the invention; and
• 5 a block diagram of a third embodiment with partial aspects of the method according to the invention.

Representing any X-ray device, the present invention is illustrated by means of an X-ray machine for examining a breast (mammography).

1 shows a schematic representation of the method according to the invention on the X-ray machine for examining the breast.

The X-ray machine 100 includes an x-ray tube 101 and a projection screen 103 , Between the x-ray tube 101 and the projection screen 103 is a research object 105 arranged. At a Mammography examination is the examination object 105 a breast. On a control console, the high voltage values (kV) and the current values (mA) for the operation of the X-ray tube can be regulated.

The x-ray tube 101 is a special electron tube for generating X-rays. It consists in its simplest form of a cathode and an anode, which are sealed in a vacuum within a sealed glass body.

The beam quality or energy of the primary radiation emerging from the x-ray tube is given over the set high voltage value. The radiation intensity can be varied via the tube current (mA). The product of tube current (mA) and time (s) mAs is an approximate measure of the applied dose for imaging.

The projection screen 103 includes a detector or film for detecting the incident X-rays.

In the first step S101 The method is pre-recorded in the AEC (Automatic Exposure Control) technique to calibrate the X-ray machine. The pre-recording is done by activating the X-ray tube 101 performed with low energy, for example, using a mAs value of 5 mAs. The X-radiation emitted during this activation is from behind the object 105 detected sensor.

The AEC technique uses as a sensor a thin radiation ionization detector (AEC detector) formed, for example, by a gas-filled ionization chamber. The radiation ionization detector becomes between the object 105 ie, the patient, and the X-ray detector arranged to detect the X-rays. The from the x-ray tube 101 emitted X-rays hit the radiation ionization detector. The ionization chambers of the radiation ionization detector are thus used as sensor element for a post-connected X-ray exposure machine.

The radiation ionization detector may comprise a plurality of measuring fields. The ionization chambers may be constructed as air-filled flat-panel detectors with one or more measuring fields (e.g., 3 or 5) and provided with an amplifier and field selection. A small overall thickness of this arrangement allows use in many X-ray systems.

The ionization chambers are supplied with miniaturized electronics that amplify the generated ionization current, digitized and processed according to the selected field combination. The amplifier electronics also includes the generation of the ionization chamber voltage, so that no high voltage is supplied to the outside of the chamber. In another embodiment, the electronics may also be located remotely from the ionization chamber.

In order to obtain appropriate blackening or contrast of the images, the radiation ionization detector is set in a region corresponding to the most dense region of the breast. This is in most cases the outer part of the breast.

The charge generated by the X-radiation in the ionization chamber is digitized in the amplifier and transmitted to the exposure machine, which generates a shutdown signal for the X-ray generator. Regardless of certain properties, such as the emitted beam quality or the object thickness, this ensures optimal and reproducible film blackening.

For example, in the AEC technique, the mAs value of the X-ray tube 101 are gradually increased until the signal value output from the radiation ionization detector exceeds a predetermined threshold. On the basis of the signal value measured by the radiation ionization detector and a known target gray value in a clinically relevant image region, also called region of interest, a setting parameter for the subsequent images is determined.

With the AEC system, it is thus possible to produce X-ray images with a reliable intensity and quality by determining a setting parameter before the actual X-ray recordings.

In the dual-energy technique (dual energy technique) two X-ray images or tomography sequences with different energy are generated in chronological order. The dual-energy technique makes it possible to improve the visibility of pathological tissue changes and may result in injection of a Contrast also serve to represent the contrast agent course (tissue-specific contrast agent kinetics). The sensitivity of the examination is increased by superimposing or subtracting a low energy image and a high energy image.

According to the invention, in the dual-energy technique, the first mAs value for the first low-energy X-ray image is determined during the step S103 calculated based on the adjustment parameter previously determined by the AEC method, for example, by multiplying the adjustment parameter by a first factor.

In addition, the second mAs value for the subsequent high energy pickup during the step S105 also calculated on the basis of the adjustment parameter, for example by multiplying the adjustment parameter by a second factor. The pulse length is kept as low as possible.

Therefore, for the high-energy recording, no second AEC-acquired preliminary image is needed and the number of calibration measurements decreases.

• - der Voraufnahme;
• - der Voraufnahme und einer vorangehenden Hauptaufnahme; oder
• - einer vorangegangenen Hauptaufnahme, deren Einstellungsparameter auf der Voraufnahme beruht.

The mAs value for high and low energy main scans, such as 2D projection images or tomography synthesis scans, is thus derived from the pre-scan previously generated, namely:

• - the preview;
• - the pre-recording and a previous main recording; or
• - A previous main recording whose setting parameters based on the pre-recording.

In general, the image can consist of an X-ray image or a tomography image. In addition, several setting parameters can be determined by the pre-recording instead of one, which serve in combination as a basis for the setting of the X-ray machine for further recordings.

2 shows a diagram for a tube yield at a low and a high energy at different anode / filter combinations.

For each used anode / filter combination in the high energy consumption of the dual-energy technology, a conversion factor UF is determined to an anode / filter combination of the previous low-energy intake. For example, conversion factors can be used for the following combinations of anode / filter: High energy absorption → Low power consumption (Anode / filter) (Anode / filter) W / Ti → W / Rh W / Cu → W / Rh W / Ti → Mo / Rh W / Cu → Mo / Rh W / Ti → Mo / Mo W / Cu → Mo / Mo

The mAs value for the high-energy consumption mAs_HE is then calculated from the product of the conversion factor UF with the mAs value for the low-energy consumption mAs LE according to the formula: $$\text{mAs\_HE}=\text{UF * mAs\_LE}$$

The low power mAs mAs LE is previously determined by the AEC technique.

The above-explained conversion factors can also be transferred to other anodes / filter combinations. If the high-energy and low-energy intake are reversed in the order, the reciprocal values of the conversion factor UF can be used.

To determine the conversion factors UF, look-up tables can be used that are obtained from a previously determined or stored tube yield (tube yield) at different tube voltages.

The conversion factors can be determined by measurement, coupled to a constant contrast-to-noise ratio CNR of a contrast agent, for example for the entire breast thickness range of typically 2 cm-12 cm, and then stored in the look-up table.

The conversion factor may also be coupled to the parenchyma dose of low energy intake that is known. Based on known tube yields, it can then be determined to which parenchymal dose the high energy intake leads.

Furthermore, based on the applied dose of the low-energy intake, a quality assurance can be implemented as an additional step in the admission parameter release, so that the user is informed in this case.

All conversion factors are stored in the X-ray machine and are modifiable and selectable by a user via a suitable interface.

In a further embodiment, the conversion factors UF for a particular anode / filter combination are distinguishable and selectable depending on a desired dose and / or a contrast value, for example in FIG W / Ti - high dose; W / Ti - high contrast W / Ti - normal dose; W / Ti - normal contrast W / Ti - low dose; W / Ti - low contrast

As a result, depending on the desired contrast, a conversion factor UF can be selected which serves to calculate the mAs value for the high-energy absorption by multiplying the mAs value for the low-energy absorption.

For high-energy recordings, the conversion factor is used to determine the mAs value as the adjustment parameter, while the high-voltage value is kept constant at the highest energy value, for example in a mammography at 49keV.

By using the described conversion factors, the mAs value for high energy uptake can be obtained by simple multiplication from the mAs value for the low energy uptake previously obtained via the AEC technique.

In an alternative embodiment, however, the image obtained during the low-energy absorption can be evaluated, for example as part of a gray value comparison, in order to obtain an additional second adjustment parameter. The subsequent high-energy absorption is then recorded as a function of this second adjustment parameter.

bestimmt. Nicht erfindungsgemäß können jedoch auch andere funktionale Zusammenhänge verwendet werden.In yet another embodiment, the subsequent high energy intake may be obtained both in dependence on the first adjustment parameter and the second adjustment parameter. According to the invention, a correction factor KF is determined on the basis of the low-energy absorption by image evaluation so that the mAs value for the second recording is determined by the formula: $$\text{mAs\_HE}=\text{UF * * KF mAs\_LE}$$

certainly. Not according to the invention, however, other functional relationships can be used.

3 shows a block diagram of a first embodiment with partial aspects of the method according to the invention.

In step S301 the setting parameter is determined by means of a pre-recording, for example by means of the AEC method. After that, in step S303 an x-ray image or a tomography scan with a mAs value calculated from the measured adjustment parameter, for example by multiplying the adjustment parameter by a first factor. The following will be in step S305 taken another X-ray image with a further mAs value, which is also calculated from the measured adjustment parameter, for example by multiplying the adjustment parameter with a second factor.

4 shows a block diagram of a second embodiment with partial aspects of the method according to the invention.

In step S401 a first setting parameter is determined by means of a pre-recording, for example by means of the AEC method. After that, in step S403 an X-ray image or a tomography scan is recorded with a mAs value which is calculated from the measured, first adjustment parameter, for example by multiplying the first adjustment parameter by a factor.

In step S405 an additional second adjustment parameter is determined on the basis of the acquired x-ray image or tomography scan. For example, a correction factor for the previously determined, first adjustment parameter can be obtained by a gray scale comparison of the X-ray image or the tomographic scan with a reference scale or another image evaluation.

In step S407 another X-ray image is recorded with a further mAs value which results from both determined adjustment parameters, for example by multiplying the first adjustment parameter by the correction factor.

5 shows a block diagram of a third embodiment with partial aspects of the method according to the invention.

In step S501 the first setting parameter is determined by means of a pre-recording, for example by means of the AEC method. After that, in step S503 recorded an x-ray image or tomography scan with a mAs value calculated from the measured first adjustment parameter, for example by multiplying the first adjustment parameter by a first factor.

In step S505 a second adjustment parameter is determined on the basis of the acquired X-ray image or tomography scan. For example, a difference value between a target value of a blackening and an actual value of the blackening can be determined on the basis of the X-ray image or tomographic scan. In step S507 another X-ray image is recorded with a further mAs value which results from the second adjustment parameter, for example by a correction of the mAs value by the determined difference value.

The advantage of the method according to the invention for AEC determination of setting parameters for dual-energy recordings is that part of the preliminary recordings are omitted, the examination time is shortened, the workflow is optimized, a simple AEC parameterization for dual-energy recordings is generated and safeguards are implemented to prevent overdose application.

Claims (9)

A method of performing an X-ray examination with a dual-energy technique on an X-ray apparatus (100) having an AEC detector disposed between an object to be examined and an X-ray detector, comprising the steps of: - determining (S501) a first adjustment parameter by means of a pre-recording, wherein the pre-recording is carried out by means of an AEC method; - recording (S503) a first X-ray image or a tomographic scan with a first energy, ie as a low-energy intake, in dependence on the first adjustment parameter; Determining (S505) a second adjustment parameter by means of the first X-ray image or tomography scan by evaluating the X-ray image obtained during the acquisition (S503) of the first X-ray image in the form of a low-energy acquisition, the second adjustment parameter being used as the difference value between a target value of a blackening and an actual value of the blackening of the first X-ray image is determined; and wherein a correction factor (KF) is determined by evaluating the first X-ray image so that the second adjustment parameter for recording (S507) of a second X-ray image results from $$\text{mAs\_HE}=\text{UF * * KF mAs\_LE}\text{.}$$

wherein UF is a conversion factor determined for each anode / filter combination for capturing (S503) the first image for an anode / filter combination of the second X-ray image, and wherein mAs HE and mAs LE respectively are the tube current time product for high energy uptake Designate low-energy intake; - recording (S507) a second X-ray image or a tomography scan with a second energy, ie as a high-energy intake, as a function of the second adjustment parameter. Method according to Claim 1 comprising the step of setting a mAs value for the acquisition of the first and / or second X-ray image as a function of the first and / or second adjustment parameter. Method according to Claim 2 comprising the step of calculating the mAs value for the acquisition of the second X-ray image by multiplying the mAs value for the first X-ray image by a factor (UF). Method according to Claim 3 , where the factor (UF) depends on a filter used in the recording. Method according to one of Claims 2 or 3 , where the factor (UF) depends on an anode used in the recording. Method according to one of Claims 3 . 4 or 5 , where the factor (UF) depends on a dose value applied during the recording. Method according to one of Claims 3 to 6 in which the factors (UF, KF) for filter, anode (s) and / or dose values are stored in a non-volatile memory. X-ray apparatus (100), wherein the X-ray apparatus (100) comprises an AEC detector and an X-ray detector and is arranged, a method according to one of Claims 1 to 7 perform. A computer program stored on a data carrier or on a memory of a computer and comprising computer readable instructions for carrying out the method according to one of the above methods claims 1 to 7 are determined when the commands are executed on the computer.

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