DE102013220018A1 - Method for calculating inspection parameter for determining examination regions e.g. liver, involves determining examination area in second image through projection of segmented examination area or information derived from first image - Google Patents

Abstract

The method involves receiving (S-A) two medical images that are detected in an identical examination region, determining (S-BS) an examination zone in the first image by segmenting the first image, and spatially registering (S-rR) the first and the second images. An examination area in the second image is determined (S-BP) through a projection of the segmented examination area or information derived from the first image into the second image. A study parameter (UP) is calculated (S-BA) by analyzing the study area in the second image. Independent claims are included for the following: (1) a computer program product for calculating inspection parameter; (2) a computer-readable medium storing program for calculating inspection parameter; and (3) a system for calculating inspection parameter.

Description

The invention relates to a method and a system for calculating an examination parameter.

Medical images are mainly taken for diagnosis by imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). For the purpose of diagnosis, an examination parameter is often calculated on the basis of medical images. Such an examination parameter typically refers to a certain area of examination, such as an examination area. an organ, a joint structure or a tumor. Such an examination parameter may be both a purely spatial value, such as the extent of a tumor, but also a spatio-temporal value, such as the rate of blood flow. In any case, it is important for the diagnosis and thus for the correct calculation of the examination parameter that the examination area is correctly determined and thus delimited from the surrounding tissue. Such a determination is made either automatically by computer-aided segmentation or manually by an operator narrowing the examination area (also known as ROI for "region of interest") using a graphical user interface. Automatic and manual determination can also be combined. However, the contrast of a particular imaging mode of an imaging procedure is often insufficient to correctly confine the examination region.

Out US 2012/0087561 A1 For example, a method for determining an ROI within a time series of images is known. In this case, a time series of images, comprising several individual images, is recorded. Each frame of the time series of images is segmented to segment the ROI. Furthermore, manual changes to the ROI are included within one or more of the frames. The manual changes are propagated to other frames, with the extent to which the manual changes are propagated depending on the time interval between the other frames and the manually changed frame.

It is an object of the invention to increase the reliability of the calculation of an examination parameter based on the determination of an examination area.

The object is achieved by a method according to claim 1, by a computer program product according to claim 9 and by a system according to claim 11. Advantageous embodiments of the invention are specified in the respectively dependent subclaims.

The solution according to the invention will be described below with reference to the claimed system as well as with reference to the claimed method. Features, advantages or alternative embodiments mentioned herein are also to be applied to the other claimed subject matter and vice versa. In other words, the subject claims (which are directed, for example, to a system) may also be developed with the features described or claimed in connection with a method. The corresponding functional features of the method are formed by corresponding physical modules.

The method according to the claimed invention comprises taking a first and a second medical image, wherein the images each capture an identical examination area, and determining the examination area in the first image by segmenting the first image. The invention is based on the idea of spatially registering the first and the second image so as to determine the examination region in the second image by projecting the segmented examination region from the first image into the second image. With a successful segmentation of the examination region in the first image and a lower image quality of the second image compared to the first image, the reliability of the determination of the examination region in the second image is increased. Therefore, the reliability of calculating an examination parameter is also increased by analyzing the examination area in the second image.

If the first and the second image are each a contrast medium-based image, certain areas of investigation of humans and animals can be represented in a particularly high-contrast manner and thus particularly easily determinable.

If a perfusion parameter is calculated as the examination parameter, particularly meaningful conclusions can be drawn on the blood flow in the examination area.

If the first and the second image are respectively recorded in different phases of the contrast agent infiltration, this makes it possible to characterize the dynamics of the blood flow in the examination region.

In a further embodiment, the examination area is a tumor. This embodiment is of particular importance because of the successful treatment of cancer Knowledge about size and stage of a tumor is of paramount importance.

If the first and the second image are each a tomographic, three-dimensional image, then the examination parameter can also capture particularly relevant (temporal) spatial relationships.

In a further embodiment, the first and the second image are recorded simultaneously or directly in succession by a CT device at different x-ray energies. By such a "dual-energy" recording complementary image information can be obtained.

If the first and the second image are recorded by different modalities, complementary image information can also be obtained.

Another embodiment includes a computer program product having a computer program invokable in the internal memory of a computer for performing the method of calculating an examination parameter so that the steps of the method can be performed quickly, identically repeatably, and robustly.

Another embodiment includes a computer-readable medium on which the computer program product is executively stored.

• – eine Aufnahmeeinheit, umfassend einen Strahlungsemitter sowie einen Strahlungsdetektor, ausgelegt zur Aufnahme eines ersten sowie eines zweiten medizinischen Bildes,
• – eine Steuerungseinheit, die ausgelegt ist die Aufnahmeeinheit zu steuern,
• – eine Segmentierungseinheit, die ausgelegt ist, das erste Bild zu segmentieren und dadurch einen Untersuchungsbereich in dem Bild zu bestimmen,
• – eine Registrierungseinheit, die dazu ausgelegt ist, das erste sowie das zweite Bild räumlich zu registrieren,
• – eine Projektionseinheit, die dazu ausgelegt ist, einen segmentierten Untersuchungsbereich in dem ersten Bild in das zweite Bild zu projizieren, sowie, anhand der Projektion in dem zweiten Bild einen Untersuchungsbereich zu bestimmen,
• – eine Berechnungseinheit, ausgelegt zur Berechnung eines Untersuchungsparameters durch Analysieren eines Untersuchungsbereichs in dem zweiten Bild.

Furthermore, the invention comprises a system for calculating an examination parameter, comprising the following units:

• A recording unit comprising a radiation emitter and a radiation detector adapted to receive a first and a second medical image,
• A control unit which is designed to control the recording unit,
• A segmentation unit configured to segment the first image and thereby determine an examination area in the image,
• A registration unit, which is designed to spatially register the first and the second image,
• A projection unit which is designed to project a segmented examination region in the first image into the second image as well as to determine an examination region on the basis of the projection in the second image,
• A calculation unit configured to calculate an examination parameter by analyzing an examination area in the second image.

In a further embodiment of the system, the radiation emitter in the form of an X-ray emitter and the radiation detector in the form of an X-ray detector are formed.

In a further embodiment of the system, the radiation emitter and the radiation detector are each in the form of an RF coil. As a result, the usual recording modes for MRI devices can be used, in particular T1 and T2 weighting. These offer advantages such as a high contrast especially in the presentation of soft tissues.

Furthermore, the system and its training are designed to perform the above methods in an advantageous manner.

The invention will be described and explained in more detail below with reference to the embodiments illustrated in the figures.

Show it:

1 a flow chart of a method for calculating an examination parameter,

2 a system for calculating an examination parameter,

3 the determination of an examination area by projection using the example of a tumor, and

4 an extended system for calculating an examination parameter.

1 shows a flowchart of a method for calculating an examination parameter. In step SA, a first and a second medical image are recorded, wherein the images each capture an identical examination area. The examination area is, for example, the body region of a patient 5 eg an organ 3 , a joint structure or a tumor. "Identical" here means that the same examination area in the sense of a medical-functional unit, eg an organ 3 in the same patient 5 is shown. "Identical" in the sense of the application also includes examination areas that are influenced in their function between the recording of the first image and the second image, for example by a drug.

A medical image is an image taken by an imaging technique such as MRI or CT for medical purposes, primarily for diagnosis. In the following, the terms "medical image" and "image" are used interchangeably. Such a picture can represent both an area and a volume. It can thus be formed two-dimensionally and constructed of so-called pixels, or it can be formed in three dimensions and constructed of so-called voxels. In addition, an image within the meaning of the present application may not only spatially, but also temporally extend. An image can therefore comprise a temporal series of individual recordings, each recorded at different times. This is particularly important if conclusions are to be drawn from the temporal change of a graphically detectable process, for example the inundation of a contrast agent. Furthermore, for the purposes of the present application, images can be, in particular, preprocessed images, that is to say filtered or reconstructed into sectional images.

The image data Bd comprising the first and / or the second image are processed further after the recording as follows:
In step S-BS, the examination area in the first image is determined by segmenting the first image. For example, the segmentation is carried out by a threshold value method or by a region-oriented method such as the so-called region growing or the so-called region splitting or by means of edge extraction. The result of step S-BS is the segmented image data sBd. Such image data may be binary, such that the value 0 is assigned to the pixels or voxels within the segmented region and the value 1 to the pixels or voxels outside the segmented region.

Furthermore, in step S-rR, the first and second images are spatially registered. Registration of the first and second images involves computing a transformation that best matches the first and second images. For example, registration may be by a feature-based method or a correlation method. In a feature method, features such as lines or edges but also points in the two images are extracted and pairwise correspondences of the features are calculated. The result of the registration is the registered image data rBd of the two images. The image data rBd can be present, for example, in the form of the original image data Bd and a rule for the transformation.

The segmented as well as the registered image data are now used to project the segmented examination region of the first image into the second image in step S-BP and thereby determine the examination region in the second image. A projection is an illustration. The term projection is not strictly mathematical. For the purposes of the present application, non-linear images may also represent projections. The projection in step S-PB is based on the transformation between the two images calculated in step S-rR. By the projection of the examination area is meant that the information about the extent of the examination area, e.g. the two-dimensional contour in the form of a closed area covering the examination area, e.g. limited to a tumor, is imaged from the first into the second image. The result of the step S-BP is the projected image data pBd comprising the second image with the information about a defined examination area in the second image.

In step S-BA, an examination parameter UP is calculated by analyzing the examination area in the second image and in the projected image data pBd, respectively. The analysis of the examination area in the second image may include known steps of image processing, e.g. further filtering or segmentation, and also a statistical analysis, e.g. the calculation of a histogram of intensity values.

The examination parameter UP can be, for example, the extent of a tumor or a perfusion parameter, e.g. the volume of blood flow per unit time, act. Such a perfusion parameter can be calculated, in particular, if the first and second image were each taken with the aid of a contrast agent in different phases of the contrast agent soak. Contrast agents are generally defined as agents which improve the representation of structures and functions of the body in imaging processes. For example, you do not see any blood vessels on an X-ray. For example, when injecting an iodine-containing solution as a contrast agent, the vessels into which the solution enters will cast X-ray shadows and make them visible. Usually, contrast media are distinguished from so-called tracers. This is an artificial, often radiolabeled endogenous or exogenous substance, which participates in the metabolism after introduction into the living body and enables or facilitates a variety of examinations. In the context of the present application, contrast agents are to be understood as meaning both conventional contrast agents and tracers.

2 this shows the scheme of a system for calculating an examination parameter UP. The illustrated system is particularly suitable for carrying out the in 1 formed method described. So the control unit is StE together with the recording unit 19 designed to carry out the step SA. The control unit StE transfers control values StW to the receiving unit 19 , for example, the X-ray tube voltage in the case of an X-ray tube as a radiation source 8th specify. The segmentation unit SE is adapted to perform the step S-BS, and the registration unit RE is adapted to execute the step S-rR. Furthermore, the projection unit PE is designed to execute the step S-BP and the calculation unit BE to execute the step S-BA. The segmentation unit SE, the registration unit RE, the projection unit PE and the calculation unit BE are to an image processing unit 14 summarized. The image processing unit 14 as well as their individual units can be designed both as hardware and as software. At the interfaces 11 These are generally known hardware or software interfaces, eg the hardware interfaces PCI bus, USB or Firewire.

3 shows the determination of an examination area by projection. In this case, a tumor is the examination area. He is in an organ 3 , eg the liver, and has both a tumor nucleus 1 as well as a tumor margin 2 as shown in the schematic diagram a).

In b) a first picture with good contrast can be seen. Without the bold inner line, it corresponds to the image data Bd of the first image. The image in b) is a contrast-enhanced image of the arterial phase in which the tumor margin 2 easy to recognize. The arterial (venous) phase is the period during which the injected contrast agent reaches the arteries (veins) of the examination area for the first time. The tumor-limiting layer is shown here in bold. Thus, a segmentation is possible and the volume of the tumor can from the rest of the organ 3 be demarcated. Image b) corresponds with the bold inner line to a segmented first image or the segmented image data sBd, wherein the bold inner line contains the information of the segmentation step. Of course, the segmented image data sBd can also be a plurality of images which, for example, depict a coherent volume. Segmentation can be automatic or manual. For example, an operator at an output unit 14 with the help of an input unit 4 and a graphical user interface to draw the bold inner line in the original first image. The image would then be segmented along the fat inner line.

For the evaluation of perfusion parameters, however, the venous phase shown in c) is interesting. However, the image shown in c) has a weak contrast, in which only the necrosis tumor center 1 can be seen. This image corresponds to the second image and is thus also a part of the image data Bd. Again, it is true that several images of the venous phase can be present, which depict a coherent volume.

Now, by projecting the segmented region of the first image into b) onto the second image in c), the relevant examination region, namely the volume of the tumor, can also be determined in this second image. In d) the projected image data pBd are shown. The dashed line now indicates the layer bounding the tumor, which has been created by projection from the first image into the second image. Now, the relevant perfusion parameters can be easily and reliably calculated from the venous phase within the volume of the tumor. Of course, the application is not limited to tumors or contrast-enhanced images.

In principle, the method is always useful when two images of an examination area are recorded with different recording conditions, one of these conditions being better for the subsequent segmentation of the examination area. The method is of particularly great use if the examination parameter UP can only be calculated from the image that is less suitable for segmentation, e.g. because it has a lower contrast.

The recording conditions may include: different times of recording (in particular of the contrast medium), different radiation energies, different modalities (eg CT and MRI), different weighting of the images in an MRI scan such as T1 weighting and T2 weighting etc ,

4 shows an extended system for calculating an examination parameter. The medical device 17 in the form of a CT device has a recording unit 19 comprising a radiation emitter 8th and comprising a radiation detector 9 , At the radiation emitter 8th for a CT device 17 it is typically an X-ray tube. At the radiation detector 9 A CT device is typically a line or flat detector, but it may also be a scintillator counter or CCD camera. When taking a medical picture, the patient lies 5 on a patient couch 6 that way with a lying base 16 connected is that he is the patient bed 6 with the patient 5 wearing. The patient bed 6 moves the patient 5 along a take-up direction through the opening 18 the recording unit 19 , During this movement, a picture of the examination area of the patient 5 created.

It can be at the medical device 17 for example, to act an MRI device. For an MRI device, the acquisition unit is 19 formed in the form of at least one RF coil. A single RF coil can be both as radiation emitter 8th as well as a radiation detector 9 be educated. In particular, the RF coil can be a local coil, for example a head coil or a knee coil.

The recordings of the CT device 17 are for processing and / or presentation to a computer 15 Posted. In the embodiment shown here, the computer has 15 both a control unit StE for controlling the recording unit 19 as well as an image processing unit 14 on that closer in 2 is described. Continue to point the computer 15 as well as the recording unit 19 interfaces 11 so that data such as the image data Bd, the control values StW and the calculated examination parameter UP can be transmitted to other units. The control unit StE and the image processing unit 14 can be designed in the form of both hardware and software.

Both the control unit StE and the image processing unit 14 or individual units of the image processing unit 14 can be implemented on different devices. For example, the image processing unit 14 be formed as part of a server, while the control unit StE as part of the medical device 17 is trained.

Furthermore, the invention comprises a computer program product for implementing the in 1 described method steps, wherein the computer program product using a computer-readable medium 21 in the memory of the computer 15 been loaded. In the computer readable medium 21 it can also be, for example, a DVD, a USB stick, a hard disk or a floppy disk.

The data processing unit 15 is with an output unit 13 and an input unit 4 connected. At the output unit 13 For example, it is one (or more) LCD, plasma, or OLED screen (s). The edition 23 on the output unit 13 For example, it may include a graphical user interface for manual segmentation and also serves to display the original image data Bd as well as all processed data. At the input unit 4 For example, it is a keyboard, a mouse, a so-called touch screen or even a microphone for voice input.

While the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. In particular, method steps can be carried out in a sequence other than that indicated.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• US 2012/0087561 A1 [0003]

Claims (14)

Method for calculating an examination parameter, comprising the following steps: Recording a first and a second medical image, wherein the images respectively capture at least one identical examination area (S-A), Determining the examination region in the first image by segmenting the first image (S-BS), Spatially registering the first and the second image (S-rR), Determining the examination region in the second image by a projection of the segmented examination region or information derived therefrom from the first image into the second image (S-BP), - Calculation of an examination parameter (UP) by analyzing the examination area in the second image (S-BA).  The method of claim 1, wherein each of the first and second images is a contrast agent-enhanced image.  The method of claim 1 or 2, wherein the examination parameter (UP) is a perfusion parameter.  Method according to one of claims 1 to 3, wherein the first and the second image are respectively recorded in different phases of the contrast agent flooding.  A method according to any one of claims 1 to 4, wherein the examination area is a tumor.  Method according to one of claims 1 to 5, wherein the first and the second image are each a tomographic, three-dimensional image. Method according to one of claims 1 to 6, wherein the first and the second image simultaneously or directly in succession by a CT device ( 17 ) are recorded at different X-ray energies.  Method according to one of claims 1 to 6, wherein the first and the second image are recorded by different modalities. Computer program product, accessible in the internal memory of a computer ( 15 ) comprising a computer program for carrying out the steps of a method according to claims 1 to 8.  Computer-readable medium on which the computer program product according to claim 9 is executively stored. System for calculating an examination parameter, comprising the following units: - a recording unit ( 19 ) comprising a radiation emitter ( 8th ) and a radiation detector ( 9 ) configured to receive a first and a second medical image, a control unit (StE) adapted to control the capture unit, a segmentation unit (SE) adapted to segment the first image and thereby an examination area in the Image to be determined, - a registration unit (RE) designed to spatially register the first and the second image, - a projection unit (PE), which is adapted to a segmented examination area in the first image in the second image projecting, as well as, based on the projection in the second image to determine an examination area, - a calculation unit (BE), designed to calculate an examination parameter (UP) by analyzing an examination area in the second image. The system of claim 11, wherein the radiation emitter ( 8th ) in the form of an X-ray emitter ( 9 ) and the radiation detector are designed in the form of an X-ray detector. The system of claim 11, wherein the radiation emitter ( 8th ) and the radiation detector ( 9 ) are each formed in the form of an RF coil. System according to one of claims 11 to 13, designed for carrying out a method according to one of claims 1 to

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