阅读说明：本技术 用于显示具有精细结构的检查区域的方法 (Method for displaying an examination region having a fine structure ) 是由 P·休伯 A·哈通 S·克普勒 B·克劳斯 B·施密特 S·施密特 于 2019-06-25 设计创作，主要内容包括：本发明涉及一种用于显示用于规划和/或控制植入物的检查区域的方法,该检查区域具有检查对象的与高对比度结构相邻的精细结构,其中高对比度结构包括骨骼和/或植入物。该方法具有以下步骤：-利用计算机断层扫描系统记录投影测量数据,该计算机断层扫描系统具有计数能量选择性X射线探测器,该探测器具有能通过能障集设定的一定数量的能量阈值,其中,根据能量阈值将第一投影测量数据分成多个光谱投影测量数据,每个光谱投影测量数据被分别分配给不同的X射线能量区域；-基于多个光谱投影测量数据的加权组合第一次重建第一图像数据集,其中第一图像数据集包含光谱信息,-基于第一图像数据集确定高对比度结构的至少一个位置信息和/或轮廓信息,-基于投影测量数据第二次重建第二图像数据集,其中高对比度结构的至少一个位置信息和/或轮廓信息被作为参数包括在重建中,并且其中以比第一图像数据集更高的图像位置分辨率重建第二图像数据集,-基于第二图像数据集显示具有精细结构的检查区域。(The invention relates to a method for displaying an examination region for planning and/or controlling an implant, which examination region has a fine structure of an examination object adjacent to a high-contrast structure, wherein the high-contrast structure comprises a bone and/or an implant. The method comprises the following steps: -recording projection measurement data with a computed tomography system having a counting energy-selective X-ray detector with a number of energy thresholds settable by an energy barrier set, wherein a first projection measurement data is divided into a plurality of spectral projection measurement data according to the energy thresholds, each spectral projection measurement data being respectively assigned to a different X-ray energy region; -reconstructing a first image dataset based on a weighted combination of a plurality of spectral projection measurement data, wherein the first image dataset contains spectral information, -determining at least one position information and/or contour information of a high contrast structure based on the first image dataset, -reconstructing a second image dataset based on the projection measurement data, wherein the at least one position information and/or contour information of the high contrast structure is included as a parameter in the reconstruction, and wherein the second image dataset is reconstructed at a higher image position resolution than the first image dataset, -displaying the examination region with fine structures based on the second image dataset.)

1. A method (S) for displaying an examination region for planning and/or controlling an implant (12, 13), the examination region having a fine structure (14) of an examination object adjacent to a high contrast structure (12, 13, 18), wherein the high contrast structure (12, 13, 18) comprises a plurality of bones (18) and/or the implant (12, 13), the method comprising the steps of:

-recording (S1) projection measurement data (PM) with a computed tomography system (31) having an energy selective X-ray detector (29) with a number of energy thresholds settable by an energy barrier set (ES), wherein the projection measurement data (PM) are divided into a plurality of spectral projection measurement data (SP) in accordance with the energy thresholds₁，...，SP_i) Each of the spectral projection measurement data being respectively assigned to a different X-ray energy region,

-projecting measurement data (SP) based on a plurality of said spectra₁，...，SP_i) The weighted combination of (S2) a first image data set (B1), wherein the first image data set (B1) contains spectral information,

determining (S3) at least one position information and/or contour information of the high contrast structure (12, 13, 18) based on the first image dataset (B1),

-reconstructing (S4) a second image data set (B2) a second time based on the projection measurement data (PM), wherein position information and/or contour information of the high contrast structure (12, 13, 18) is included as a parameter in the reconstruction, and wherein the second image data set (B2) is reconstructed at a higher image position resolution than the first image data set (B1),

displaying (S5) the examination region with the fine structure (14) based on the second image data set (B2).

2. Method (S) according to claim 1, wherein a maximum spatial resolution determined by the X-ray detector (29) is selected as a recording parameter when recording the projection measurement data (PM) with the computed tomography system (31).

3. The method (S) according to any one of claims 1-2, wherein the high contrast structures (12, 13, 18) are suppressed when displaying the examination region.

4. The method (S) according to any one of claims 1 to 3, wherein spectral information of the first image data set (B1) and the second image data set (B2) are shown combined.

5. The method (S) according to any claim from 1 to 4, further comprising the step of:

-segmenting (S6) the fine structure (14) based on the second image dataset (B2).

6. The method (S) according to any claim from 1 to 5, further comprising the step of:

-determining (S7) the size (AB) of the fine structure (14).

7. The method (S) according to claim 6, further comprising the steps of:

-visualizing (S8) the determined size (AB).

8. The method (S) according to any one of claims 1 to 7, wherein the fine structure (14) comprises soft tissue.

9. The method (S) according to any one of claims 1 to 8, wherein the fine structure (14) includes a cochlea (14).

10. A computer tomography system (31) for performing the method (S) according to any one of the preceding claims, having:

an energy-selective X-ray detector (29) having a number of energy thresholds which can be set by an energy barrier set (ES), the energy being selectedThe selective X-ray detector is designed to record projection measurement data (PM) of an examination region, wherein the projection measurement data (PM) are divided into a plurality of spectral projection measurement data (SP) according to the energy threshold value₁，...，SP_i) Each of the spectral projection measurement data being respectively assigned to a different X-ray energy region,

a data processing unit (45) which is designed for

a. Receiving the projection measurement data (PM) of the examination region from the energy-selective X-ray detector (29),

b. projecting measurement data (SP) based on a plurality of said spectra₁，...，SP_i) Wherein the first image data set (B1) contains spectral information,

c. determining position information and/or contour information of high contrast structures (12, 13, 18) based on the first image data set (B1),

d. reconstructing a second image data set (B2) on the basis of the projection measurement data (PM), wherein the position information and/or the contour information of the high-contrast structures (12, 13, 18) are included as parameters in the reconstruction and the second image data set (B2) is reconstructed with a higher image position resolution than the first image data set (B1),

-an output unit (49) which is designed to display the examination region on the basis of the second image data set (B2).

11. A computer program product having: a computer program directly loadable into a memory means (51) of a data processing unit (45); and a program section for performing all the steps of the method (S) according to any one of claims 1 to 9 when the computer program is executed in the data processing unit (45).

12. A computer-readable medium, on which program segments are stored which are readable and executable by a data-processing unit (45), such that all the steps of the method (S) according to any one of claims 1 to 9 are performed when the program segments are executed by the data-processing unit (45).

Technical Field

The invention relates to a method, a computed tomography system, a computer program product and a computer-readable medium for displaying an examination region having fine structures which are adjoined by high-contrast structures.

Background

Computed Tomography (CT) is an imaging method mainly used for medical diagnosis. In computed tomography, a radiation source, for example an X-ray source and an X-ray detector cooperating therewith, are rotated around an object to be examined in order to record spatial three-dimensional image data. During the rotational movement, measurement data are recorded in angular sectors. The projection measurement data is a projection or projections which contain information about the attenuation of radiation passing through the examination object from different projection angles. From these projections, a two-dimensional slice image or a three-dimensional volume image of the examination object can be calculated. The projection measurement data is also referred to as raw data or the projection measurement data may have been pre-processed such that detector-related intensity differences, e.g. attenuation, are reduced. From these projection measurement data, image data can then be reconstructed, for example by means of so-called filtered back-projection or by means of an iterative reconstruction method.

Various methods are known for scanning an examination object with a computer tomography system. For example, circular scanning is used, sequential circular scanning using feed or helical scanning. In addition, other types of scanning that are not based on circular motion are also possible, for example, scanning with linear segments. By means of at least one X-ray source and at least one opposing X-ray detector, absorption data of the examination object from different recording angles are recorded, and from these absorption data or projections collected, sectional images through the examination object are calculated by means of a corresponding reconstruction method.

In computed tomography, photon counting direct conversion X-ray detectors may be used. X-rays or photons can be converted into electrical pulses in a direct conversion X-ray detector by means of a suitable converter material. For example CdTe, CZT, CdZnTeSe, CdTeSe, CdMnTe, InP, TlBr2, HgI2, GaAs or others may be used as the converter material. The electrical pulses are evaluated by evaluation electronics, for example an integrated circuit (application specific integrated circuit, ASIC). In counting X-ray detectors, X-ray radiation is measured by counting electrical pulses triggered by the absorption of X-ray photons in the converter material. The magnitude of the electrical pulse is generally proportional to the energy of the absorbed X-ray photon. Thereby, spectral information can be extracted by comparing the magnitude of the electrical pulse with a threshold value. The use of energy-resolving or energy-selective counting X-ray detectors, for example direct conversion X-ray detectors, allows the material to be decomposed into two or three materials, such as bone and soft tissue, based on the measured data.

Furthermore, with energy selective counting X-ray detectors a significantly improved detector spatial resolution can be achieved, which is approximately 2 to 5 times the resolution of conventional CT detectors.

Computed tomography is also used for implant planning and control, where very fine structures surrounded by high contrast structures, e.g. bones, must sometimes be displayed. One example is the use of cochlear implants. Here, the electrode is placed in the Cochlea (Cochlea) of a human and surrounded by the skull bone, the electrode comprising only a total length of about 30-40 mm in the "let-down" state and a diameter of 3 mm at the base, or 1.5 mm at the tip. For planning cochlear implants, the relevant region is recorded by computer tomography and, for example, the size of the cochlea is determined so that a suitable implant, in particular a suitably designed electrode, can be determined. For control, the position of the implant is determined and performed correctly after the implant is fitted, in particular in the cochlea. Another example is the incorporation of implants in the form of screws, for example for fixing tears or fractures in bones.

Disclosure of Invention

The invention relates to a method for the improved display of an examination region having a fine structure for planning and/or controlling an implant, in particular if the fine structure is adjacent to a high-contrast structure.

According to the invention, this object is achieved by a method according to claim 1, a computed tomography system according to claim 10, a computer program product according to claim 11 and a computer readable medium according to claim 12.

The invention relates to a method for displaying an examination region for planning and/or controlling an implant, which examination region has a fine structure of an examination object adjacent to a high-contrast structure, wherein the high-contrast structure comprises a bone and/or an implant. In the context of the method according to the invention, projection measurement data are recorded with a computed tomography system having a counting energy-selective X-ray detector with a number of energy thresholds which can be set by an energy barrier set. The projection measurement data is divided into a plurality of spectral projection measurement data according to an energy threshold, which are respectively assigned to different x-ray energy regions. Furthermore, a first image data set is reconstructed based on a weighted combination of the plurality of spectral projection measurement data, wherein the first image data set contains spectral information. Furthermore, at least one position information and/or contour information of the high-contrast structure is determined on the basis of the first image data set. Furthermore, a second image data set is reconstructed on the basis of the projection measurement data, wherein at least one position information and/or contour information of the high-contrast structures is included as a parameter in the reconstruction, and wherein the second image data set is reconstructed with a higher image position resolution than the first image data set. Furthermore, an examination region with a fine structure is displayed on the basis of the second image data set.

The invention is based on the idea that a very detailed display of the relevant structures is advantageous for judgment, planning and control in order to ensure optimal conditions and a high quality of treatment of the patient in the case of an implant. Accurate display of fine structures, such as the cochlea, may also become more difficult, since adjacent high contrast structures, such as bones or implants comprising e.g. metal, may themselves cause image artifacts. For example, hardening artifacts and/or metal artifacts may occur, which are caused by strong absorption by high-contrast structures in the low-energy components of the X-ray spectrum, in particular more strongly than the high-energy components, or when only a very small fraction of the X-rays reaches the X-ray detector after passing through these objects. These artifacts can severely affect the visualization and/or recognizability and delimitation of fine structures relative to surrounding tissue.

The inventors have realized that the advantages of counting energy-sensitive X-ray detectors in the context of the method according to the invention, i.e. the access to spectral information and thus the accessible higher spatial resolution of the detectors, may be used for an improved display of an examination region of a fine structure adjacent to a high-contrast structure, thereby ensuring optimal conditions for planning and/or controlling the implant.

The high contrast structure comprises bone and/or an implant or a part of an implant. In particular, the high contrast structure may comprise an implant if the high contrast structure has a material with a high linear absorption coefficient, such as a metallic material. For example, in the planning of an implant, the high contrast structure may comprise only bone, and in the control and/or planning of subsequent operations, the high contrast structure may then comprise the bone and the implant or part of the implant in the examination object. A fine structure in the sense of the present invention is a structure which is generally characterized by smaller dimensions than a high-contrast structure, or for which a higher image position resolution is advantageous or necessary than a high-contrast structure for diagnostic evaluation. A fine structure is then to be understood as a structure which is to be recognizable at least in a dimension with a minimum dimension, which is only a few millimeters, for example less than 10 millimeters, in particular less than 5 millimeters, in order to be reliably evaluated in the image data set and to be delimited from the surrounding tissue. For example, the delicate structure may be a cavity surrounded by bone structures or a gap between bone structures, such as in the case of a joint. The delicate structure may also be a crack in a skeletal structure, a fracture or a similar defective structure. The fine structure itself may comprise bone. However, the fine structure may also include soft tissue, such as muscle, fat, cartilage, tissue membranes, nerves or other soft tissue. The fine structure may for example be filled with a liquid.

The X-ray detector used in the present invention may be referred to as an energy selective, (photon) counting or direct conversion X-ray detector. The X-ray detector has a plurality of detection elements. The plurality of detection elements may be arranged, for example, in a matrix, such that different detection elements have spatially different positions within the X-ray detector. The detection elements each have an energy barrier with an assigned energy threshold. Each detection element preferably has a plurality of energy barriers, each energy barrier having a respective assigned energy threshold. The energy threshold may preferably be assigned to photon energies in keV. The energy threshold may be set, for example, to photon energy, voltage, or current. The number of energy thresholds, in particular with regard to the detection elements, may be an integer K, for example K4 or K5 or another K. The set of energy barriers then comprises, for example, at least one energy threshold. In particular, the first set of energy barriers includes a plurality of energy thresholds. The energy barrier set may be assigned to a plurality of detection elements. However, there may also be a plurality of different sets of energy barriers which are respectively assigned to a subset of the plurality of detection elements.

The setting of the energy threshold may comprise setting a value of a load, for example setting a current or a voltage of a digital-to-analog converter. Thereby setting the energy threshold. The setting of the set of energy barriers may comprise setting of a plurality of energy thresholds.

In the recording of projection measurement data with a computer tomography system, the projection measurement data can be divided into a plurality of spectral projection measurement data on the basis of an energy threshold value, which are respectively assigned to different X-ray energy regions, i.e. sub X-ray energy regions. For example, the projection measurement data may thus be divided into at least two sets of spectral projection measurement data, which may be assigned to higher-energy and lower-energy X-ray energy regions. However, it is also possible to divide into more X-ray energy regions, for example four or five, and thus collect more spectral information. Here, the X-ray energy region may be described by an upper and/or a lower energy threshold.

During a first reconstruction, a first image data set is generated by spectral application based on the spectral projection measurement data. By applying a spectroscopic method, a first image data set may be reconstructed, which substantially contains high contrast structures, such as bone and/or metal. At least a first image data set can be reconstructed, which is contrast-enhanced and/or which is a high-contrast structure that is better delimited from other tissue. In particular, by applying the spectroscopic method, artifacts in the first image data set, such as hardening artifacts and/or metal artifacts of high contrast structures, may be avoided or reduced. Thus, high contrast structures can be particularly advantageously identified in the first image data set on the basis of the first image data set. The high contrast structure may be segmented in a particularly advantageous manner based on the first image dataset and the spectral information.

The spectral application may be applied to the level of the raw data or also to the level of the image data. In particular, the spectral application is based on spectral projection measurement data or a weighted combination of image data based on spectral projection measurement data. A weighted combination may be applied individually to each pixel of the examination region. For example, the spectral application comprises combining the spectral projection measurement data into a virtual auxiliary projection measurement data combination, i.e. a weighted combination may be performed at the raw data level. This may be done, for example, by a linear combination of spectral projection measurement data and definable weighting coefficients. The combination may correspond to, for example, a weighted sum or difference of the spectral projection measurement data. For example, the weighting coefficients may be selected such that a material or materials of high contrast structures, such as bone and/or metal, in the imaging examination region are displayed, preferably by weighting a portion of the X-ray spectrum and another region of lower X-ray energy. The weighting factors can also be selected such that a particularly advantageous X-ray energy region is included in each case only in the first image data set. However, the auxiliary image data assigned to the X-ray energy regions can also be reconstructed from the spectral projection measurement data assigned to each X-ray energy region, for example. Based on the weighted combination, the auxiliary image data may be combined to form the first image data set, e.g. by weighted summation. That is, weighted combination may also be performed at the image data level. Also, a first image data set may be generated which allows for a better identification of image areas containing high contrast structures. Based on a weighted combination of the plurality of spectral projection measurement data, further methods of material splitting may also be performed, for example separating bone and/or metal from other tissue, and from which a first image data set may be generated which contains spectral information and is suitable for better identifying image regions containing high contrast structures.

The first image data set may be reconstructed by an iterative method or a filtered back-projection method. For the reconstruction of the first image data set, only a part of the projection measurement data, for example only a part of the projections, may be used.

From the first image data set, high-contrast structures, for example position information and/or contour information of bones and/or metals, can be determined in a particularly simple manner. The position information and/or contour information to be determined may comprise identifying image regions in the first image data set containing high-contrast structures on the basis of contours, for example by edge detection, and/or on the basis of image values, for example by comparison with an intensity threshold. Based on the position information and/or contour information, the illumination thickness may also be determined along the recorded projections of the high contrast structure. Determining the position information and/or the contour information may comprise segmenting the high contrast structure.

According to the invention, a second reconstruction of the second image data set is performed on the basis of the first projection measurement data, wherein at least one position information and/or contour information of the high-contrast structures is included as a parameter in the reconstruction.

In particular, the second reconstruction may be performed based on the first projection measurement data having a smaller subdivision or without subdividing the projection measurement data into spectral projection measurement data. Thus, a larger or full available amount of projection measurement data may be used as a basis for the second reconstruction. The second reconstruction may be based on an iterative or filtered back-projection method.

The information about the high contrast structures may be used together with a suitable correction algorithm to obtain a second image data set with reduced artifacts. Advantageously, hardening artifacts in the second image data set may be reduced. Advantageously, metal artifacts in the second image data set may be reduced. Thus, an improved and clearer display of a fine structure can be achieved.

For example, position and/or contour information in the form of segmented high-contrast structures may be obtained from the first image data set, or the high-contrast structures may be segmented in a simplified manner in a preliminary version of the second image data set by means of position and/or contour information from the first image data set. The segmented high contrast structure may then be used, for example, to generate new virtual raw data by forward projection, which substantially contains the high contrast structure. These can then be used for an iterative reconstruction and correction process to obtain a second image data set with reduced artifacts. Other correction algorithms may be used which may be used by the spectral information from the first image dataset. The material information as well as the position and/or contour information of the high-contrast structure or, for example, the thickness of the high-contrast structure determined therefrom can be improved. For example, from the information in the projection measurement data, the section of the measurement data containing high-contrast structures can be identified in each case and information, such as the thickness of the material and the illumination, can be corrected accordingly and improved by this section.

According to the invention, the second image data set is reconstructed at a higher image position resolution than the first image data set containing the spectral information.

For example, the first image data set is reconstructed with a substantially reduced image position resolution. This means in particular that the resolution of the projection measurement data during the reconstruction recording of the first image data set or during the reconstruction is actually and subsequently reduced. By reducing the resolution of at least one of the following directions relative to the X-ray detector, a substantially reduced resolution of the projection measurement data may be produced: in the channel direction, the row direction, the projection direction. The detector row direction is typically in the z-direction, i.e. towards the system axis of the computer tomography system about which the X-ray detector rotates. The channel direction is orthogonal to the row direction and tangential to the detector surface. Instead, the projection direction is orthogonal to the detector surface and thus also to the row direction and the channel direction. For example, the data of multiple probe elements ("binning") may be combined. Also, during reconstruction, reconstruction parameters may be selected that achieve reduced noise when the image position resolution is reduced, e.g., soft filter kernels.

In particular, the actually reduced resolution advantageously compensates for the increased noise and degraded signal-to-noise ratio introduced by using the spectroscopic method in the first image data set, either fully or partially. Advantageously, a spectroscopic method can thereby be successfully applied and at the same time the projection measurement data can be maintained at high resolution, so that a high-resolution representation of the fine structure and the examination region can be achieved on the basis of the same projection measurement data.

Thus, in the step of reconstructing the second image data set a second time, information is transferred from the lower resolution image data set (first image data set) to the higher resolution image data set (second image data set). As a result, artifacts in the second image data set cannot be completely corrected and/or suppressed. However, by applying the spectral information to the higher resolution second image data set, at least a sufficiently high display enhancement can be achieved while maintaining a high image position resolution to allow an improved display of the examination region, as opposed to the conventional acquisition of conventional computed tomography systems.

According to the invention, an examination region with a fine structure is displayed on the basis of the second image data set. Advantageously, the fine structure can be displayed with high resolution. Advantageously, artifacts, such as hardening artifacts and/or metal artifacts, generated by high contrast structures may be compensated for or reduced. Advantageously, an accurate and unambiguous display of the fine structure is possible, i.e. a detailed and sufficient display, wherein the fine structure can be easily distinguished from the surrounding tissue and/or surrounding high contrast structures. This means that, for example, the outline of the fine structure can be recognized more easily. Advantageously, an improved, high resolution and artifact reduced display may be used for implant planning and control. It is thus advantageously possible to improve the evaluation of the examination region, improved fine structure measurement and improved control, for example of the position of the implant.

In an advantageous variant of the method, the maximum spatial resolution determined by the X-ray detector is selected as a recording parameter when recording the first projection measurement data with the computer tomography system.

The spatial resolution determined by an X-ray detector depends to a large extent on the size or edge length of the detector elements. In addition, the spatial resolution of the detector is determined, for example, by the material and thickness of the sensor layers used. The spatial resolution provided by an energy selective counting X-ray detector may be about two to five times the resolution of a conventional CT detector. Advantageously, a second image data set with a maximum achievable image position resolution can be reconstructed which is at a sufficiently high applied radiation dose, i.e. each detection element counts a sufficiently large number of photons, mainly determined by the spatial resolution of the detector. Advantageously, the fine structure can thus be displayed in detail with high resolution.

In particular, the minimum layer thickness of the reconstructed layer image, i.e. the sectional image, can be selected such that a high image position resolution is achieved in the layer direction in the second image data set. The minimum layer thickness depends on the size of the detection element.

A variant of the method according to the invention comprises suppressing high-contrast structures when displaying the examination area.

The spectral information and/or the positional information and/or the contour information of the high-contrast structures from the first image data set thus determined can be used to suppress or at least partially suppress high-contrast structures, such as bones, in the second image data set by means of a suitable algorithm. For example, voxels in the second image dataset containing high contrast structures may be identified based on spectral information of the first image dataset and then edited and/or removed. For example, a subtraction algorithm may be used which suppresses high contrast structures in the second image data set.

By transferring information from the lower resolution image data set to the higher resolution image data set, bone structures in the second image data set may not be completely suppressed. However, at least contrast-enhanced display of fine structures can be achieved.

Advantageously, a particularly advantageous display for planning and/or controlling the fine structure of the implant can thus be achieved without or with reduced disturbing visual effects of high-contrast structures. Advantageously, planning and/or control of the implant may be facilitated.

It is conceivable that high-contrast structures can be selectively displayed or suppressed in the display of the examination region.

In a variant of the method according to the invention, the spectral information of the first image data set and the second image data set are displayed combined.

The first image data set can be superimposed on the second image data set. Only spectral information from the first image data set can be transmitted to the corresponding image area of the second image data set. For example, the spectral information may be displayed superimposed in color. For example, different materials that may be identified based on spectral information may be highlighted in color. The first image data set may also be superimposed on the second image data set, for example partially transparent and colored.

Advantageously, a simple display of the spectral information obtained from the first image dataset is possible. Advantageously, a visual separation between the high contrast structure and the fine structure can be achieved in an improved manner.

For example, implementation of the consolidated representation may include only selectively superimposing spectral information.

In an advantageous variant of the method, the method further has the step of segmenting the fine structure on the basis of the second image data set.

The segmentation may be performed automatically by the data processing unit. Segmentation may be performed, for example, pixel-based, voxel-based, edge-based, region-based, and/or region-based. The segmentation may also be based on a model-based approach, where assumptions on the object to be segmented are allowed. The segmentation may be hierarchical, that is to say starting from a two-dimensional layer image, or a three-dimensional segmentation method may also be used. The segmentation step may also be performed semi-automatically. For example, starting points for segmentation or embryonic cells or rough contour information may be set manually.

The inventors have realized that by means of the method of the invention a more detailed and clearer and possibly higher contrast display of the examination region and the fine structure can be achieved, so that an automatic or semi-automatic segmentation can advantageously be achieved in an improved manner, since the separation between the fine structure and the surrounding tissue can be achieved simply. Automatic or semi-automatic segmentation may advantageously facilitate more efficient workflow. In addition, a purely manual segmentation of the clinical staff, for example by contours or contours of fine-contrast structures being manually tracked, can be achieved with an improved and more detailed display.

Segmentation may advantageously ease the measurement of fine structures. Also, it is conceivable to display a three-dimensional display of a fine structure without surrounding tissues based on the segmented fine structure. On the basis of the segmented fine structure, a model of the fine structure can also be formed.

Further, in a variant, the method according to the invention comprises a step of determining the size of the fine structure based on the second image data set.

The dimension may be, for example, length, diameter or circumference. For example, it may be a length that is the length of the center line of the fine structure ("Centerline"). For example, the dimension is also the surface or cross-sectional area or volume occupied by the fine structure. Several dimensions of the fine structure can also be determined.

The size can be determined from the display of the examination region with the fine structure on the basis of the second image data set. However, the size may also be determined based on the segmented fine structure (if any) or a model of the fine structure generated from the segmented fine structure.

Due to the improved display of the fine structure and the examination area, the dimensions can be determined more easily and in particular more accurately.

The size may also be determined automatically. The inventors have realized that the improved display of fine structures provided by the method according to the invention may advantageously facilitate and improve the automated or at least partially automated determination of dimensions. An efficient workflow can advantageously be achieved by automatically dimensioning.

It is also conceivable that the determined dimensions are automatically transferred into the document of the examination result. For example, to plan an implant, a particular determined fine structure may be automatically entered into the table. This allows for an efficient workflow.

Furthermore, the method according to the invention comprises in a variant a visualization of the determined dimensions.

For example, the specific size, i.e. for example the start and end points and/or the dimensioning processes and/or the surface or volume are visualized in a superimposed color representation in the display of the examination region. For example, the central axis of the fine structure may be displayed in color superposition, e.g. from which the length is derived. For this purpose, relevant quantitative results can be displayed, for example in μm or mm.

The display of the dimensions and/or the indication of the quantitative result may also be additionally displayed in a different view than the display of the examination region. For example, the size is visualized according to the segmented fine structure or highlighted, for example in color, in the thus generated model of the fine structure, which for example starts and ends and/or the process of dimensioning and/or the surface or volume is highlighted in color.

Advantageously, the clinical personnel may simply track certain sizes based on the display, or may make corrections.

In a variation of the method, the fine structure comprises soft tissue and/or liquid.

The soft tissue may include muscle, fat, cartilage, tissue membranes, nerves or other soft tissue. The fine structure may also be filled with a liquid. Advantageously, by means of the method according to the invention, it is possible to distinguish between the material of the high-contrast structure and the fine structure. This makes it easier to distinguish between fine structures and high contrast structures.

In a variation of the method, the fine structure comprises a cochlea.

The cochlea is a spirally wound cavity surrounded by skeletal structures, which is filled with fluid (perilymph and endolymphatic). In addition, the cochlea includes tissue membranes and neural or auditory cells. Surrounding the cochlea is the very calcium and strongly absorbed skull bone (rock bone).

Advantageously, the advantages of the method according to the invention may be used particularly advantageously in the display of the cochlea and in the planning and/or control of cochlear implants: the higher spatial resolution of energy-selective counting X-ray detectors can be utilized particularly well here, since, due to the smaller associated volume to be examined, even at higher radiation doses, only very low effective total body doses are applied and radiation-sensitive regions can be bypassed well. Thus, in this application, unlike in other regions, there is no limitation of the radiation dose in the image position resolution, but rather the spatial resolution provided by the X-ray detector, which is mainly determined by the size of the detection elements, and is clearly superior to conventional detectors in energy selective counting X-ray detectors. Artifacts which occur due to strongly absorbing skull bones or already implanted implants and the metals contained therein, in particular the electrodes, can be advantageously reduced or avoided by means of the spectral information.

Advantageously, the method according to the invention allows a detailed and unambiguous display of the cochlea, so that the planning and/or control of a cochlear implant can be improved.

Similar advantages are given in the planning and control of other implants, such as fixation devices for fractures, dental implants, joint replacements, etc.

The invention further relates to a computer tomography system for performing the method according to the invention, comprising an energy selective X-ray detector, an output unit and a data processing unit.

The energy selective X-ray detector has an adjustable energy threshold. In particular, the X-ray detector has a plurality of adjustable energy thresholds per detection element or sub-pixel. The X-ray detector thus makes it possible to record projection measurement data with the computer tomography system, wherein the projection measurement data can be subdivided into a plurality of spectral projection measurement data on the basis of an energy threshold, which data are each assigned to different X-ray energy regions.

The output unit is at least configured to display an examination region of the examination object based on the second image data set reconstructed by the data processing unit and/or the reconstructed first image data set.

The data processing unit is designed in particular for receiving projection measurement data which have been recorded by an energy-sensitive X-ray detector.

The data processing unit is further designed to reconstruct the first image data set on the basis of the projection measurement data. The first image data set is based on a weighted combination of the plurality of spectral projection measurement data. Thus, the first image dataset comprises spectral information.

The data processing unit is further designed to determine at least one position information and/or contour information of the high-contrast structure on the basis of the first image data set.

The data processing unit is further designed to reconstruct the second image data set on the basis of the projection measurement data, wherein at least one position information and/or contour information of the high-contrast structures is included as a parameter in the reconstruction, and wherein the second image data set is reconstructed with a higher image position resolution than the first image data set.

The computer tomography system is therefore designed in particular for carrying out the method according to the invention. Corresponding parts of the description of the method according to the invention and advantages of the method according to the invention may also be transferred to the computer tomography system according to the invention.

In a further advantageous embodiment the data processing unit is further designed to perform further steps, wherein the steps may comprise an advantageous embodiment of the method according to the present invention.

The invention further relates to a computer program product with a computer program which can be loaded directly into a memory means of a data processing unit of a computed tomography system, wherein the program segments are adapted to carry out all the steps of the method according to the invention when the computer program is executed in the data processing unit of the computed tomography system.

The computer program of the computer program product may be directly loadable into a memory unit of the data-processing unit. The computer program product may comprise a computer-readable medium on which program sections of a computer program are stored, wherein the program sections may be read and executed by a data-processing unit to perform all method steps of the method and aspects thereof.

The computer program product may comprise other elements than a computer program. These other elements may be hardware, such as a memory unit (USB memory unit, memory card, hard disk memory, etc.) storing a computer program, a hardware key, etc. to use the computer program and/or software, such as a document or a software key using the computer program.

The configuration as a computer program product has the following advantages: an already existing data processing unit can be easily adapted by a software update for use according to the invention.

The data processing unit may comprise a PC (personal computer), a PC workstation, a virtual machine running on host hardware, a microcontroller or an integrated circuit. Alternatively, the data processing units may also comprise real groups of computers ("clusters") or virtual groups of computers ("clouds").

The invention also relates to a computer-readable medium, on which program sections are stored which are readable and executable by a data processing unit in order to perform all the steps of the inventive method when the program sections are executed by the data processing unit.

Drawings

Embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Shown here are:

fig. 1 schematically shows a diagram of a method according to the invention according to a first embodiment;

fig. 2 schematically shows a diagram of a method according to the invention according to a second embodiment;

FIG. 3 shows a schematic diagram of an application of the method according to the invention;

fig. 4 schematically shows a diagram of a computer tomography system according to the invention.

Detailed Description

Fig. 1 schematically shows the flow of a method S according to the invention for displaying an examination region for planning and/or controlling an implant 12, 13 with a fine structure 14 of an examination object 39 adjacent to a high-contrast structure 12, 13, 18 in a first embodiment. Method S includes the steps of recording S1, first reconstructing S2, determining S3, second reconstructing S4, and displaying S5.

The high contrast structure 12, 13, 18 comprises bone 18 and/or an implant 12, 13 or part thereof. In particular, the high contrast structure may comprise a metal-containing portion of the implant. The implants 12, 13 may be, for example, a cochlear implant 13 with an electrode 12 as shown in fig. 3, where the electrode is placed within the cochlea. The high contrast structure 12, 13, 18 then comprises a rock bone 18 and/or a cochlear implant 13, and in particular the electrode 12 which in this example comprises the cochlear implant 13. The fine structure 14 may be a cavity surrounded by bone structure. The fine structure 14 may be a gap or a crack surrounded by bone structures. The fine structure 14 may itself comprise bone, but may also comprise soft tissue or a filler fluid. As a fine structure, for example, a structure can be understood which, in a dimension having a minimum dimension, is represented by identifiable methods, of only a few millimeters, for example less than 10 millimeters, in particular less than 5 millimeters. In an exemplary application of cochlear implant 13, fine structure 14 comprises cochlea 14, which has a diameter (represented by length 28 in fig. 3) of only about 2-4mm at the base and a diameter in the range of only 1-2mm at the top. The examination region then corresponds, for example, to a head region of the patient 39.

In a recording step S1, projection measurement data PM are acquired from the examination region by the computed tomography system 31. In this case, the computed tomography system 31 has energy selectivityAn X-ray detector 29 with an energy threshold value of K, for example K4 or K5 or another K, which can be set by the energy barrier set ES. Based on the energy threshold, the projection measurement data PM can be divided into a plurality of spectral projection measurement data SP₁，...，SP_i(i∈[1；N]Where N is an integer), these spectral projection measurement data are respectively assigned to different X-ray energy regions, i.e. to sub-X-ray spectra. The number N of spectral projection measurement data may correspond to the number K of thresholds, either K +1 or less than K. At least 2 spectral projection measurements are distinguished.

In a variant of the method, the maximum resolution determined by the X-ray detector 29 can be selected for the step of recording S1. The spatial resolution provided by the energy selective counting X-ray detector 29 may be about two to five times the resolution of a conventional CT detector. Advantageously, it can be used to achieve a high resolution display of the examination area and the fine structure 14, since raw data of as high a resolution as possible can be obtained.

In the step of first reconstructing S2, the measured data SP are reconstructed on the basis of a plurality of spectral projections₁，...，SP_iThe first time, wherein the first image data set B1 contains spectral information, the first image data set B1 is reconstructed by weighted combination. By a suitable choice of the weighting factors, the high-contrast structures 12, 13, 18 can be displayed substantially in the first image data set and/or in a contrast-enhanced form. The weighted combination can be carried out individually at the raw data level or at the image data level, or else for each pixel of the examination region. In this case, the spectral projection measurement data SP₁，...，SP_iAt least one virtual auxiliary projection measurement data can be combined, for example by weighted sums or differences. From the auxiliary projection measurement data set, the first image data set B1 may be reconstructed by known methods. However, the measurement data SP can also be determined from spectral projections which are correspondingly assigned to the X-ray energy regions₁，...，SP_iAuxiliary image data of the respective assigned X-ray energy regions are reconstructed, which auxiliary image data are combined to form a first image data set. For example, the weighting coefficients may be selected such that they are preferably determined by fitting one of the X-ray spectraThe portions are weighted higher or lower to preferentially display certain materials, such as bone and/or metal, in the imaged examination region. At the same time, artifacts such as hardening artifacts and/or metal artifacts can advantageously be avoided or reduced.

Based on a plurality of spectral projection measurement data SP₁，...，SP_iOther material decomposition methods may also be performed, for example, separating bone and/or metal from other tissue and generating a first image dataset comprising spectral information.

In particular, a first image data set B1 may be reconstructed which is suitable for easily identifying an image region or image regions and/or image region-based data, the image region or regions containing high-contrast structures 12, 13, 18.

In the step of determining S3, at least one position information and/or contour information of the high-contrast structure 12, 13, 18 is determined based on the first image data set B1. The high-contrast structures 12, 13, 18 can be identified particularly advantageously on the basis of the spectral information or on the basis of the first image data set B1 containing spectral information. The high-contrast structures 12, 13, 18 may be segmented in a particularly advantageous manner on the basis of the spectral information or on the basis of the first image data set B1. This information may be used together with suitable correction algorithms to reconstruct the artifact reduced second image data set B2.

In a second reconstruction S4, a second image data set B2 is reconstructed based on the projection measurement data PM. Here, position information and/or contour information of the high-contrast structures 12, 13, 18 are included as parameters in the reconstruction. The position information determined from the first image data set B1 and/or the contour information and/or the thickness of the high-contrast structures 12, 13, 18 determined therefrom can be transmitted back to the projection measurement data PM, i.e. proportions in the data containing the high-contrast structures 12, 13, 18 can be identified in the projection measurement data PM and artifacts corrected accordingly. For example, the high contrast structure 12, 13, 18 may be segmented based on the first image data set B1 and new virtual raw data may be generated from the forward projection, which may be used in an iterative image reconstruction process to obtain an artifact reduced image data set B2. For example, metal artifacts and/or hardening artifacts may thus be reduced. Therefore, an improvement in a fine structure and clearer display can be achieved.

According to the invention, the second image data set B2 is reconstructed at a higher image position resolution than the first image data set B1 containing spectral information. The first image data set B1 may be reconstructed with a substantially reduced image position resolution. This means in particular that the resolution of the projection measurement data PM after recording during the reconstruction or reconstruction of the first image data set B1 is actually and subsequently reduced. For example, the data of a plurality of detection elements of the X-ray detector 29 (referred to as "binning") and/or the data of a plurality of projection slices may be combined. Furthermore, during the first reconstruction S2, reconstruction parameters may be selected which achieve reduced noise when the image position resolution is reduced, such as soft filter kernels, e.g. B50 or Q40 filter kernels. In particular, with a practically reduced resolution, the increased noise and degraded signal-to-noise ratio in the first image data set B1 can be fully or partially compensated by using a spectroscopic method.

For example, according to one aspect of the invention, the second image data set B2 is reconstructed with a maximum image position resolution which is determined by the spatial resolution predetermined by the X-ray detector if a sufficient radiation dose is used for the recording, as a result of which the fine structures are advantageously displayed with a particularly high resolution and can be measured, for example, precisely.

In particular, the minimum layer thickness of the reconstructed layer image, i.e. the sectional image, is selected such that a high image position resolution is also achieved in the layer direction in the second image data set B2. The minimum layer thickness depends on the dimensions of the detection elements of the X-ray detector. For example, the edge length of the detector element may be less than 0.3 mm. For example, the edge length of the detecting element in a specific embodiment is 0.25 mm. For example, a layer thickness of less than 0.3 mm may be selected. For example, the layer thickness in a particular embodiment is 0.2 mm.

Advantageously, although information is transferred from the lower resolution first image data set B1 to the higher resolution second image data set B2 by using spectral information, a sufficiently high improvement of the image data, e.g. reduction of artifacts, can be achieved while maintaining a high image position resolution. This allows an improved and more accurate display of the fine structure 14 and an optimal resolution of the structure details compared to conventional recordings of conventional computer tomography systems.

In the step of displaying S5, the inspection region having the fine structure 14 is displayed based on the second image data set B2. Advantageously, an exact and unambiguous display of the fine structure 14 is possible, that is to say a detailed display in which the fine structure 14 can be distinguished simply from the surrounding tissue and/or the surrounding high-contrast structures 12, 13, 18. Advantageously, an improved, high resolution and artifact reduced display may be used for planning and control of the implants 12, 13. An accurate assessment for planning the examination region of the implant 12, 13 is advantageous. Advantageously, the position and location of the implant 12, 13 or parts of the implant relative to the fine structure 14 can be controlled in an improved manner.

In one embodiment of the present invention, when displaying S5 of the inspection region, the high-contrast structures 12, 13, 18 may be suppressed completely or partially in the display of the inspection region. The position information and/or contour information of the high-contrast structures 12, 13, 18 from the first image data set B1 may be used to at least partially suppress the high-contrast structures 12, 13, 18 in the second image data set B2 or to increase the contrast in the second image data set B2. Advantageously, a better identifiability of the fine structure 14 can thus be achieved.

Further, according to an aspect of the present invention, in displaying S5, display of a merged image in which spectral information of the first image data set B1 is superimposed on the second image data set B2 is conceivable. For example, the spectral information may be displayed in color superposition, so that different materials are displayed in color. Advantageously, an improved visual separation between, for example, bone structures and/or implants and delicate structures can be achieved.

Fig. 2 schematically shows the inventive method S in a second embodiment. The illustrated method S further comprises the step of determining S7. The method may further comprise the steps of segmenting S6 and visualizing S8.

In the step of determination S7, the size AB of the fine structure 14 is determined. Dimension AB may be, for example, a length, a diameter, or a circumference. For example, the length of the fine structure 14 may be the length of the center line. For example, dimension AB is also the surface or cross-sectional area or volume occupied by the fine structure 14. Several dimensions of the fine structure 14 can also be determined. Due to the improved display of the fine structure 14 and the examination area, the dimensions can be determined more accurately. Advantageously, the dimension AB associated with the planning of the implants 12, 13 can be determined accurately. The improved display may also facilitate automatic or semi-automatic determination of the dimension AB. By automatically determining the size AB, an efficient workflow can advantageously be achieved. However, for example, the beginning and end of the fine structure 14 or contours in the image data set can also be marked manually.

In an exemplary application of the method S, the dimension AB is, for example, the length of the cochlea 14 in the context of planning and/or examining the cochlear implant 13.

In the step of segmenting S6, the fine structure 14 is segmented based on the second image data set B2. Segmentation may be performed, for example, pixel-based, voxel-based, edge-based, region-based, and/or region-based. The segmentation may also be based on a model-based approach, where assumptions are allowed for the object to be segmented. The segmentation may be hierarchical, that is to say starting from a two-dimensional layer image, or a three-dimensional segmentation method may also be used. The segmentation step may also be performed semi-automatically. For example, starting points for segmentation or embryonic cells or rough contour information may be set manually.

Advantageously, the segmentation of the fine structure 14, which is automatically performed by the data processing unit, may be made possible by an improved and more detailed display. Automatic or semi-automatic segmentation may advantageously facilitate more efficient workflow. In addition, a purely manual segmentation of the clinical staff, for example by the contours or contours of the fine-contrast structures 14 being manually tracked, can be achieved with an improved and more detailed display. Segmentation may also allow for improved determination of the dimension AB.

Further, method S may include visualizing S8 the determined dimension AB. For example, the determined size AB, i.e. for example the starting and ending points and/or the course of the determination of the size AB and/or the surface or volume are visualized in color superimposition in the display of the examination region shown in the display step S5. The display of the dimension AB may additionally also be displayed in a different view than the representation of the examination area. For example, the dimension AB may be based on a display of a segmentation of the fine structure 14 or visualized in a model of the fine structure 14 resulting therefrom. The visualization may also include a display of the quantitative results for the dimension AB.

The use of the method S according to the invention is schematically shown in fig. 3. The sketch is a cochlea 14 of a person with a cochlear implant 13. Cochlea 14 is a portion of the inner ear and is a spiral filled by a tissue membrane, fluid filling and separating into a passage cavity surrounded by a rock 18, which rock 18 is a human skull of extra-calcium. The Corti device is located in one of the channels along with the auditory cells (hair cells), which convert the mechanical excitation of the sound waves into nerve impulses of the auditory nerve 26. For example, when hair cells damage nerve impulses, cochlear implant 13 is used. Cochlear implant 13 includes an electrode carrier 16 on which is mounted electrode 12 inserted into cochlea 14. At the other end of the cochlear implant 13, a receiving coil 10 is provided, which is arranged between the skin 22 and the outer surface of the skull 20. The receiver coil 10 is used to receive signals from an external microphone (not shown) and an external transmitter coil and convert them into electrical pulses, which may be further conducted to electrodes 12 in the cochlea 14. By means of the electrodes 12, the auditory nerve 26 can be stimulated, which forwards the electrical signal to the auditory center of the brain. Different stimulation locations in the cochlea 14 produce different frequency perceptions.

The overall "let-down" or "expanded" cochlea 14 is typically only about 35mm in length, with a base diameter of about 2-4mm (represented by length 28 in fig. 3) or 1 millimeter in the range of the apex. The cochlea 14 is surrounded by a very stiff calcareous skull (rock bone) 18, which makes it difficult to view the cochlea 14, since the bone 18 greatly attenuates the low energy component of the X-ray spectrum and thus leads to spectral changes and to hardening artifacts. Likewise, the inserted cochlear implant 13 or the metal contained therein, particularly the electrode 12 of the cochlear implant 13, may cause difficult visualization of the cochlea 14 by hardening and metal artifacts.

For the use of cochlear implants 13, an accurate display and possibly accurate measurements are required, for example, to determine the appropriate length of the electrode carrier 16 that supports the electrode 12 within the cochlea 14 (referred to as "electrode length") or to control the position of the electrode 12 or cochlear implant 13 relative to the cochlear fine structure 14. To determine the electrode length, a "centerline," the central axis of the cochlea 14, is often used herein.

The method S according to the invention may advantageously allow an improved display of the cochlea 14. Artifacts caused by absorption in the bone 18 or the metal in the cochlear implant 13, in particular in the electrode 12, can be advantageously reduced and at the same time a high resolution and a clear mind can be achieved. Advantageously, suppression of the display of the surrounding bone 18 may be achieved.

Advantageously, more accurate measurements of the cochlea 14 can be achieved, or the position of the cochlear implant 13 relative to the cochlea 14 can be controlled in an improved manner, if desired. For example, a dimension AB may be determined that includes a length of cochlea 14 from a base (indicated by length 28 in fig. 3) to a tip of cochlea 14.

Advantageously, an automatic or semi-automatic segmentation of the cochlea 14 and/or an automatic or semi-automatic measurement of the cochlea 14, which is not possible or only conditional or has a high uncertainty in conventional computed tomography images, may thereby be improved. Advantageously, this ensures a more efficient workflow.

For example, on the basis of the segmented cochlea 14, a model may also be generated that allows the cochlea 14 to be displayed in different ways. The spiral wound structure of cochlea 14 can be displayed in an "unwound" or "expanded" state, respectively. That is, cochlea 14 may be represented as a tapered linear tube or channel. Thereby, for example, the position of the cochlear implant 13 in the cochlea 14, such as the arrangement of the electrodes 12, may be simulated and simplified, or the dimension AB may be easily determined.

The application of the cochlear implant 13 shown in fig. 3 represents a particularly advantageous variant of the method S according to the invention, since the advantages of the method S according to the invention are used in the display of the cochlea 14 and in the planning and/or control of the cochlear implant 13: the higher resolution of the energy-selective counting X-ray detector 29 can be used very well here, since even at higher radiation doses a smaller relevant volume is examined, only a very low effective whole-body dose is applied and radiation-sensitive regions can be easily avoided. Thus, in the present application, unlike in other regions, there is no limitation on the radiation dose in the image position resolution, but rather on the spatial resolution provided by the X-ray detector 29, which is mainly determined by the size of the detection elements, and is clearly superior to conventional detectors in energy selective counting X-ray detectors 29. At the same time, artifacts caused by the, in particular calcium-rich and strongly absorbing, skull 18 surrounding the cochlea 14 and/or by the metal of the cochlear implant 13, in particular by the electrode 12, are advantageously reduced or avoided by means of the spectral information.

Fig. 4 shows an exemplary embodiment of a computer tomography system 31 according to the present invention for performing the method S according to the present invention and variants thereof. The computer tomography system 31 comprises a projection measurement data recording unit 33 with a rotor 35. The rotor 35 comprises an X-ray source 37 and an energy sensitive X-ray detector 29. The energy-selective X-ray detector 29 has a number of energy thresholds which can be set by the energy barrier set ES and is designed to record projection measurement data PM of the examination region, wherein the projection measurement data PM is divided into a plurality of spectral projection measurement data SP on the basis of the energy thresholds₁，...，SP_iWhich are respectively assigned to the X-ray energy regions. The examination subject 39 lies on a patient couch 41 and can be moved along a rotational axis 43 through a projection measurement data recording unit 33 for recording projection measurement data PM of the examination region. For reconstructing and analyzing the sectional images, a data processing unit 45 is used. The data processing unit 45 is configured to receive projection measurement data PM of the examination region from the energy-selective X-ray detector 29 and to project the measurement data SP on the basis of a plurality of spectra₁，...，SP_iTo reconstruct a first image data set B1, wherein the first image data set isB1 contains spectral information. Furthermore, the data processing unit 45 is designed to determine position information and/or contour information of the high-contrast structures 18, 12, 13 on the basis of the first image data set B1 and to reconstruct the second image data set B2 on the basis of the projection measurement data PM, the position information and/or the contour information. The high contrast structures 18, 12, 13 are included as parameters in the reconstruction. An input device 47 and an output unit 49 are connected to the data processing unit 45. The output unit 49 is configured to display the examination region based on the second image data set B2.

The data processing unit 45 may also comprise a control system which is designed to adapt system settings of the computer tomography system 31, for example recording parameters of the X-ray detector 29. For example, the control system may output or set the energy barrier set ES or the energy threshold of the X-ray detector 29.

The computer program product comprises a computer program which can be loaded directly into the memory means 51 of the data processing unit 45 of the computed tomography system 31, having program sections for performing all the steps of the method according to the invention when the computer program is executed in the data processing unit 45 of the computed tomography system 31. The program segments, which are readable and executable by the data processing unit 45, are stored on a computer readable medium in order to perform all the steps of the inventive method when the program segments are executed by the data processing unit 45.

The X-ray detector 29 has an adjustable energy threshold. In particular, the X-ray detector 29 has a plurality of adjustable energy thresholds per detection element or sub-pixel. For example, the edge length of the detector element may be less than 0.3 mm. For example, the side length is 0.25 mm. In particular, the spatial resolution provided by the quantum-counting X-ray detector 29 may be about two to five times that of a conventional CT detector.

Although the present invention has been described in detail through preferred embodiments, the present invention is not limited to the disclosed examples, and other modifications may be derived therefrom by those skilled in the art without departing from the scope of the present invention.