EP1617763A1

EP1617763A1 - Apparatus for angiographic x-ray photography

Info

Publication number: EP1617763A1
Application number: EP04728619A
Authority: EP
Inventors: Holger c/o Philips Int. Pty. & St. GmbH SCHMITT; Michael c/o Philips Int. Pty. & St. GmbH GRASS; Volker c/o Philips Int. Pty. & St. GmbH RASCHE
Original assignee: Philips Intellectual Property and Standards GmbH; Koninklijke Philips Electronics NV
Current assignee: Philips Intellectual Property and Standards GmbH; Koninklijke Philips NV
Priority date: 2003-04-22
Filing date: 2004-04-21
Publication date: 2006-01-25
Also published as: JP2006524087A; WO2004093684A8; US7539529B2; US20060293579A1; WO2004093684A1

Abstract

The invention relates to an X-ray photographic apparatus for imaging the blood flow in the coronary vessel tree of a patient. According to the invention, a first series (1) of X-ray projection images of the coronary tree in various phases of the heart cycle is recorded, at the same time as the ECG (2) of the patient is taken. The three-dimensional structure of the vessel tree in the various phases of the heart cycle is then reconstructed by means of suitable programming means of the computerised portion (17) of the claimed apparatus. A second series (6) of X-ray projection images is recorded while a contrast agent is administered, again at the same time as the ECG (7) is taken. In order to determine the time-dependent contrast agent concentration within the reconstructed three-dimensional structure of the vessel tree, the invention proposes locating local image regions which correspond to individual vessel segments (5, 8) within the X-ray projection images in the second series (6), according to the positions in space of the vessel segments (5, 8) in the relevant phase of the heart cycle. The contrast agent concentration in the area of the vessel segments (5, 8) is then determined by evaluation of X-ray absorption in the thus located local image regions.

Description

Device for angiographic x-ray imaging

The invention relates to an X-ray imaging device with computer means which are set up to visualize the blood flow in a coronary vascular tree of a patient.

Furthermore, the invention relates to a corresponding computer program and an X-ray imaging method that can be carried out on the device according to the invention.

In the field of angiography, three-dimensional medical imaging methods such as B. three-dimensional rotary X-ray imaging (3D-RX) is becoming increasingly important. The image data obtained with such methods contain interesting information for the diagnosis of vascular diseases, such as. B. stenoses. The visualization of the vascular structures is crucial so that a treating doctor can quickly and reliably identify potential sources of danger.

Techniques are known in the prior art which make it possible to reconstruct the three-dimensional structure of the vascular tree to be examined from the plurality of two-dimensional projection images recorded by means of 3D-RX using special modeling or back-projection techniques on a suitable computer. The computer-aided three-dimensional reconstruction of the patient's vascular tree from the recorded image data thus makes it possible to visualize the course of the blood vessels with a high degree of reproduction accuracy, wherein anatomical structures not belonging to the vascular system of interest can be hidden if necessary. The three-dimensional reconstruction of the vascular structures is also a particularly useful tool when planning interventions, such as left heart catheterization (PTCA). In the techniques known to date, however, no information regarding the blood flow through the examined vascular tree is disadvantageously obtained. The flow behavior and in particular the flow rate of the blood can provide important information for the examining doctor, for example in relation to the severity of an existing stenosis. In the known methods, the doctor can only assess the condition of a stenosis on the basis of the reconstructed geometry of the vessels. However, with the known methods, which can only provide static images of the vascular tree, it is not possible to assess the threat of a stenosis on the basis of the effects of the stenosis on the blood flow, ie the flow velocity of the blood in the area of the stenosis.

The object of the invention is therefore to provide an X-ray imaging device which enables the flow behavior of the blood in the coronary vascular tree to be examined. The invention solves this problem by a device according to claim

1.

The invention is based on the use of a suitable computer of an X-ray imaging device for visualizing the blood flow in a coronary vascular tree. In the sense of the invention, the claimed X-ray imaging device can be a complete X-ray device with corresponding

Imaging means or a single workstation for processing medical image data.

The invention proposes to start with a visualization of a data set consisting of x-ray projection images and EKG data (electrocardiogram) of the examined patient obtained in parallel therewith. These data can be recorded in advance of the visualization and then fed to the computer via a corresponding data input or via temporary storage in a database. This procedure is appropriate if the technology according to the invention is used on a medical workstation separate from the device used for the actual image recording. Alternatively, the data can already are processed during the image recording according to the invention if the computer means used for this purpose are directly assigned to the X-ray device equipped with corresponding image recording means.

Accordingly, a first set of x-ray projection images of the vascular tree is recorded in different phases of the cardiac cycle, preferably from different projection directions. A suitable contrast medium is administered to the patient to make the vascular tree visible in the X-ray projection images. During the acquisition of the first set of x-ray projection images, the patient's EKG is also continuously recorded so that each of the images acquired can be assigned to a specific phase of the cardiac cycle.

On the basis of the first set of x-ray projection images, the three-dimensional structure of the vascular tree is reconstructed in the various phases of the cardiac cycle by a suitable program control of the computer means in accordance with a method known per se. The reconstructed structure is then divided into a plurality of vessel segments, for each of which the flow behavior of the blood is to be examined individually.

During or immediately after the administration of a contrast medium, a second set of x-ray projection images of the vascular tree is taken - again with the patient's ECG being recorded at the same time. For the

The second set of x-ray projection images is expediently given only a short contrast medium bolus, which is advantageous for the examination of the flow behavior of the blood in accordance with the further method steps described below. In contrast, the first set of x-ray projection images is preferably recorded with a longer contrast agent bolus so that the three-dimensional structure of the vascular tree can be examined as precisely as possible. The flow behavior of the blood in the vascular tree can be examined on the basis of the two sets of x-ray projection images by determining the time-dependent contrast agent concentration within the reconstructed three-dimensional structure of the vascular tree. This is done according to the Invention first assigning the x-ray projection images of the second set to a phase of the cardiac cycle on the basis of the recorded EKG. Local image areas within the x-ray projection images of the second set are then found for the vascular segments of the reconstructed structure of the vascular tree, specifically according to the spatial positions of these vascular segments in the relevant phase of the cardiac cycle. For this purpose, the image areas on which the respective vessel segments are imaged in the respective projection images can be calculated, for example, according to the projection angles at which the x-ray projection images of the second set were taken. By evaluating the X-ray absorption within those found in this way

Image areas are then determined as to how the contrast medium concentration within the individual vascular segments changes over time, thus how the vascular tree fills with contrast medium. This allows direct conclusions to be drawn about the flow behavior of the blood within the vascular tree. Finally, the contrast medium flow determined with the device according to the invention must be visualized in a suitable manner for the examining doctor. For this purpose, it is conceivable, for example, that the time-dependent contrast agent concentration is displayed as a brightness or color value in a three-dimensional view of the reconstructed three-dimensional structure of the vascular tree.

The basic idea of the invention is, on the one hand, to take into account the movements of the blood vessels during the heartbeat when reconstructing the three-dimensional structure of the vascular tree. Not only is the structure itself reconstructed, but also its temporal change caused by the movement of the heart. The individual stages of movement of the vascular tree are assigned to the respective phases of the cardiac cycle on the basis of the ECG recorded parallel to the image recording. On the other hand, the idea of the invention is also to record the patient's EKG when the second set of x-ray projection images is recorded, so that the reconstructed three-dimensional structure of the vascular tree with the image features of the patient is related to the respective phase of the cardiac cycle X-ray projection images of the second set can be matched. This results in comprehensive three-dimensional data about how the blood flows through the vascular tree.

It is possible in a particularly advantageous manner that during or after the administration of the contrast medium, the second set of x-ray projection images is first recorded while the vascular tree is filled with contrast medium, and only then is the first set of x-ray projection images recorded after the vascular tree has been completely filled with contrast media is filled. In this way, only a single dose of contrast medium is required. The evaluation of the x-ray projection images outlined above for determining and visualizing the time-dependent contrast agent concentration within the vascular tree then takes place with the computer means of the x-ray imaging device only after the image acquisition of the first and second set of x-ray projection images has been completed.

If parts of the vascular tree run in the direction of projection when the x-ray projection images are taken or parts of the vascular tree overlap in the direction of projection, it is not readily possible to clearly assign the relevant vascular segments to the corresponding image areas. It is therefore expedient for the first and / or second set of x-ray projection images to be recorded by means of continuous rotary x-ray imaging at a plurality of projection angles.

It should be noted that the first set of x-ray projection images should be recorded from as many projection directions as possible so that the three-dimensional spatial structure of the vascular tree can be reconstructed as precisely as possible. The reconstruction can in particular also take place on the basis of a large number of projection images, which are recorded during several successive cardiac cycles. In contrast, when taking the second set of x-ray projection images, special attention must be paid to the temporal resolution so that the inflow of the contrast agent into the vascular tree can be precisely tracked in time. It therefore makes sense that the The second set of x-ray projection images is recorded under only a few different or even under a fixed projection angle.

The first set of x-ray projection images is expediently taken with continuous rotary x-ray imaging during several successive cardiac cycles, and the second set is recorded with only a few, possibly fixed projection angles with the highest possible temporal resolution while the vascular tree fills with contrast agent.

In addition to the vascular tree, the reconstructed three-dimensional image derived from the first set of x-ray projection images also shows anatomical structures, for example bones, which can represent a disruptive factor in the further evaluation. It therefore makes sense for the three-dimensional structure of the vascular tree to be reconstructed using computer-aided modeling of the vascular tree while eliminating the other anatomical structures contained in the first set of x-ray projection images.

A computer program according to claim 7 is suitable for implementing the visualization technology according to the invention on an X-ray imaging device equipped with a suitable computer means. The corresponding software can advantageously be used by users of suitable imaging devices on a data medium, such as a floppy disk or CD-Rom, or for downloading a data network (Internet) is made available.

An X-ray imaging method that can be carried out on the device according to the invention is the subject of claims 8 to 12.

Exemplary embodiments of the invention are explained below with reference to the figures. Show it:

FIG. 1 flow diagram of the visualization technology according to the invention; Figure 2 X-ray imaging device according to the invention. The method shown schematically in FIG. 1 serves to visualize the blood flow in a patient's coronary vascular tree. The method begins with the acquisition of a first set 1 of x-ray projection images in different phases of the cardiac cycle. A first EKG 2 of the patient is recorded parallel to the recording of the x-ray projection images. The three-dimensional structure of the vascular tree is then reconstructed from the first set 1 of x-ray projection images, specifically in the different phases of the cardiac cycle, so that a set 3 of three-dimensional data sets of the coronary vascular structure is then available for the different heartbeat phases. Computer-aided modeling of the vascular tree is carried out, anatomical structures contained in the x-ray projection images that do not belong to the examined vascular tree being eliminated. In a data set 4, the three-dimensional structure of the vascular tree is divided into a plurality of vascular segments 5. The data record 4 contains information about the spatial position of each vascular segment 5 in every phase of the cardiac cycle, so that the structure and movement of the vascular tree is completely modeled by the data record 4.

In the further course of the method, a second set 6 of X-ray projection images of the vascular tree are recorded during or after the administration of a contrast agent. A second EKG 7 of the patient is also recorded here. The X-ray projection images of the second set 6 are each assigned to a phase of the cardiac cycle on the basis of the EKG 7.

For a vascular segment 8 for which the time dependence of the contrast agent concentration is to be determined, local image areas within the x-ray projection images of the second set 6 are found in accordance with the spatial position of the vascular segment 8 in a specific phase of the cardiac cycle. The time-dependent position data of data record 4 are used for this. The contrast medium concentration within the vascular segment 8 is then determined by evaluating the X-ray absorption within the local image areas found. The time course of the contrast agent concentration in the range of Vessel segment 8 can be shown as diagram 9 for the purpose of visualization. Such diagrams can be generated for all vascular segments, so that overall there is a comprehensive picture of the blood flow within the vascular tree. The imaging device shown in FIG. 2 is a

C-arm X-ray device which has a C-arm 10 which is suspended from a ceiling (not shown in more detail) by means of a holder 11. An X-ray radiation source 12 and an X-ray image converter 13 are movably guided on the C-arm 10, so that a plurality of X-ray projection images of a patient 15 lying in the center of the C-arm 10 on a patient table 14 can be recorded at different projection angles. The synchronous movement of the x-ray radiation source 12 and the x-ray image converter 13 are controlled by a control unit 16. When imaging, the x-ray radiation source 12 and the x-ray image converter 13 run synchronously around the patient 15. The image signals generated by the X-ray image converter 13 are transmitted to a computer-controlled image processing unit 17. The heartbeat of the patient is monitored by means of an EKG device 18, and the EKG is transmitted to the image processing unit 17. The image processing unit 17 has a program control, by means of which the x-ray projection images are processed in accordance with the previously described method. A monitor 19 connected to the image processing unit 17 is used for visualization.

Claims

CLAIMS:

1. X-ray imaging device with computer means (17), which are set up to visualize the blood flow in a coronary vascular tree of a patient such that the visualization takes place on the basis of data that a first set (1) of X-ray projection images of the vascular tree in different phases of the cardiac cycle, a first ECG (2) of the patient (15) recorded simultaneously with the first set (1), a second set (6) of X-ray projection images taken during or after the administration of a contrast medium, and one simultaneously with the second set (6) Record the recorded second EKG (7) of the patient (15), the computer means (17) having a program control which works to determine the time-dependent contrast agent concentration within the three-dimensional structure of the vascular tree according to the following method steps:

Reconstruction of the three-dimensional structure of the vascular tree in the different phases of the cardiac cycle from the first set (1) of x-ray projection images and division of the structure into a plurality of vascular segments (5, 8);

Determining the time-dependent contrast agent concentration (9) within the reconstructed three-dimensional structure of the vascular tree by aa) assigning the x-ray projection images of the second set (6) to a phase of the cardiac cycle on the basis of the recorded second ECG (7); bb) Finding local image areas assigned to the individual vascular segments (8) within the x-ray projection images of the second set (6) corresponding to the spatial positions of the vascular segments (8) in the relevant phase of the cardiac cycle according to the reconstructed three-dimensional structure of the vascular tree: cc) determining the contrast medium concentration within the vascular segments (8) by evaluating the X-ray absorption within the local image areas found in method step bb);

Visualization of the contrast medium flow through the three-dimensional structure of the vascular tree according to the determined time-dependent contrast medium distribution (9).

2. X-ray imaging device according to claim 1, with means (10, 11, 12, 13) for generating the first and the second set of x-ray projection images of the coronary artery tree of the patient (15) under different

Projection directions, and with means (18) for recording the patient's ECG (15) during the recording of the first and second set of x-ray projection images.

3. X-ray imaging apparatus according to claim 2, wherein the computer means

(17) are set up in such a way that during or after the administration of the contrast medium, the second set (6) of x-ray projection images is first recorded while the vascular tree fills with contrast medium, and then the first set (1) of x-ray projection images is recorded after the Vascular tree is completely filled with contrast medium.

4. X-ray imaging device according to claim 2 or 3, wherein the computer means (17) are further set up such that the recording of the first and / or second set of x-ray projection images takes place by means of continuous rotary x-ray imaging at a plurality of projection angles.

5. X-ray imaging device according to one of claims 2 to 4, wherein the computer means (17) are further set up such that the recording of the second set (6) of x-ray projection images takes place at least at a fixed projection angle.

6. X-ray imaging device according to one of claims 1 to 5, wherein the computer means (17) are set up in such a way that a computer-assisted modeling of the vascular tree for the reconstruction of the three-dimensional structure while eliminating the other anatomical structures contained in the first set (1) of x-ray projection images he follows.

7. Computer program for an X-ray imaging device, for visualizing the blood flow in a coronary vascular tree of a patient, the computer program receiving as input data which contain a first set (1) of

X-ray projection images of the vascular tree in different phases of the cardiac cycle, a first ECG (2) of the patient (15) recorded simultaneously with the first set (1), a second set (6) of X-ray projection images taken during or after the administration of a contrast medium and a simultaneously with the second set (6) recorded second EKG (7) of the patient (15), whereby by the

A program control is implemented on computer means (17) of the X-ray imaging device, which works to determine the time-dependent contrast agent concentration within the three-dimensional structure of the vascular tree according to the following process steps: - Reconstruction of the three-dimensional structure of the vascular tree in the different phases of the cardiac cycle from the first sentence (1) X-ray projection images and division of the structure into a plurality of vascular segments (5, 8);

Determining the time-dependent contrast agent concentration (9) within the reconstructed three-dimensional structure of the vascular tree by aa) assigning the x-ray projection images of the second set (6) to a phase of the cardiac cycle on the basis of the recorded second ECG (7); bb) locating local image areas assigned to the individual vessel segments (8) within the x-ray projection images of the second set (6) corresponding to the spatial positions of the vessel segments (8) in the relevant one Phase of the cardiac cycle according to the reconstructed three-dimensional structure of the vascular tree; cc) determining the contrast medium concentration within the vascular segments (8) by evaluating the X-ray absorption within the local image areas found in method step bb);

8. X-ray imaging method for visualizing the blood flow in a patient's coronary vascular tree with the following method steps: 22); b) reconstruction of the three-dimensional structure of the vascular tree in the different phases of the cardiac cycle from the first set (1) of x-ray projection images and division of the structure into a plurality of vascular segments (5, 8); c) recording a second set (6) of x-ray projection images of the vascular tree during or after the administration of a contrast medium while simultaneously recording a second EKG (7) of the patient; d) determining the time-dependent contrast agent concentration (9) within the three-dimensional structure of the vascular tree reconstructed in method step b) by aa) assigning the x-ray projection images of the second set (6) to a phase of the cardiac cycle on the basis of the recorded second ECG (7); bb) locating local image areas assigned to the individual vessel segments (8) within the x-ray projection images of the second set (6) corresponding to the spatial positions of the vessel segments (8) in the relevant one Phase of the cardiac cycle according to the three-dimensional structure of the vascular tree reconstructed in method step b); cc) determining the contrast medium concentration within the vascular segments (8) by evaluating the X-ray absorption within the local image areas found in method step bb); e) Visualization of the contrast medium flow through the three-dimensional structure of the vascular tree according to the time-dependent contrast medium distribution determined in method step d) (9).

9. X-ray imaging method according to claim 8, wherein during or after the administration of the contrast medium, the second set (6) of x-ray projection images is first recorded while the vascular tree fills with contrast medium, and then the first set (1) of x-ray projection images is recorded, after the vascular tree is completely filled with contrast medium.

10. X-ray imaging method according to claim 8 or 9, wherein the recording of the first and / or second set of x-ray projection images takes place by means of continuous rotary x-ray imaging at a plurality of projection angles.

11. X-ray imaging method according to one of claims 8 to 10, wherein the recording of the second set (6) of X-ray projection images takes place under at least one fixed projection angle.

12. X-ray imaging method according to one of claims 8 to 11, wherein for the reconstruction of the three-dimensional structure in method step b), a computer-assisted modeling of the vascular tree takes place while eliminating the other anatomical structures contained in the first set of x-ray projection images.