DE102011083674A1 - Angiographic examination method for three-dimensional color-coded representation of flow properties of blood vessels i.e. cerebral vessels of patient, involves computing curve parameters from time curves, and visualizing curve parameters - Google Patents

Abstract

The method involves detecting a rotation picture without contrast agents (S1) with a normal angular range for reconstruction of a mask volume. Filling rotation picture is detected (S2) with a contrast agent in an enlarged angular range, and the filling rotation picture with filling volumes is reconstructed (S3). The filling volumes are subtracted (S4) from the mask volume for generating a set of vessel volumes. Time curves are generated (S5) from intensity of individual voxels of the vessel volumes over time, and curve parameters are computed (S6) from the curves and visualized (S7).

Description

The invention relates to an angiographic examination method for the representation of flow properties of vessels of an examination subject, in particular for the color-coded representation of 3-D angiographies of cerebral vessels. Such an examination method can be used, for example, when performing a digital subtraction angiography (DSA) and is known from the US 7,500,784 B2 known, the below with reference to the 1 is explained.

The 1 shows an exemplified monoplanes X-ray system with one of a stand 1 in the form of a six-axis industrial or articulated robot held C-arm 2 at the ends of which is an X-ray source, for example an X-ray source 3 with X-ray tube and collimator, and an X-ray image detector 4 are mounted as an image recording unit.

By means of the example of the US 7,500,784 B2 Known articulated robot, which preferably has six axes of rotation and thus six degrees of freedom, the C-arm 2 be spatially adjusted, for example, by turning around a center of rotation between the X-ray source 3 and the X-ray image detector 4 is turned. The angiographic X-ray system according to the invention 1 to 4 is in particular about centers of rotation and axes of rotation in the C-arm plane of the X-ray image detector 4 rotatable, preferably around the center of the X-ray image detector 4 and around the center of the X-ray image detector 4 cutting axes of rotation.

The known articulated robot has a base frame which is fixedly mounted, for example, on a floor. It is rotatably mounted about a first axis of rotation a carousel. On the carousel is pivotally mounted about a second axis of rotation a rocker arm, on which is rotatably mounted about a third axis of rotation, a robot arm. At the end of the robot arm, a robot hand is rotatably mounted about a fourth axis of rotation. The robot hand has a fastener for the C-arm 2 which is pivotable about a fifth axis of rotation and about a perpendicular thereto extending sixth axis of rotation rotatable.

The realization of the X-ray diagnostic device is not dependent on the industrial robot. It can also find common C-arm devices use.

The X-ray image detector 4 may be a rectangular or square semiconductor flat detector, preferably made of amorphous silicon (a-Si). However, integrating and possibly counting CMOS detectors may also be used.

In the beam path of the X-ray source 3 is on a tabletop 5 a patient table a patient to be examined 6 as a research object. At the X-ray diagnostic facility is a system control unit 7 with an image system 8th connected to the image signals of the X-ray image detector 4 receives and processes (controls are not shown, for example). The X-ray images can then be displayed on a monitor 9 to be viewed as.

Instead of in 1 For example, illustrated X-ray system with the stand 1 in the form of the six-axis industrial or articulated robot can, as in 2 simplified, the angiographic X-ray system also a normal ceiling or floor mounted bracket for the C-arm 2 exhibit.

Instead of the example illustrated C-arm 2 For example, the angiographic x-ray system may also include separate ceiling and / or floor mount brackets for the x-ray source 3 and the X-ray image detector 4 have, for example, are electronically rigidly coupled.

In the diagnosis of vascular disease, three-dimensional imaging in the field of interventional neuroradiology is a standard tool. For image acquisition in the angiographic laboratory are in a circular motion of the C-arm 2 Approx. 150 projection images were taken from different projection angles and reconstructed into a 3-D volume data set. In order to be able to reconstruct a complete 3-D volume, an angle range of> 180 ° must be covered during the rotation. Two consecutive rotation acquisitions, one with and one without contrast enhancement, followed by subtraction of the two reconstructed data sets yield a 3-D reconstruction of contrast-filled blood vessels.

When diagnosing flow-reducing vascular diseases, such as stenoses, it may be helpful to have information about the time course of the contrast agent in the vessel, such as from Charles M. Strother et al. in "Parametric Color Coding of Digital Subtraction Angiography" AJNR Am J Neuroradiol, 2010 , www.ajnr.org, pages 1 to 6 is described. For example, this could be achieved by appropriate color coding of the 3-D vascular tree. In today's method of 3-D image reconstruction, however, such information can not be generated because it is a static uptake of the blood vessels.

Today available products for the color representation of flow characteristics of cerebral vessels are based exclusively on two-dimensional image sequences. Here, 2-D DSA sequences are recorded with a high frame rate and the contrast agent course is analyzed pixel by pixel. From the resulting time-contrast curve suitable parameters are calculated and displayed in color. The software syngo iFlow from Siemens AG, Sector Healthcare, follows this principle and encodes the time-to-peak parameter of the contrast agent for color representation, as in the brochure "syngo iFlow / Dynamic Flow Evaluation / Answers for life", Order no. A91AX-20902-11C1-7600, printed CC AX WS 12081.5, 12.2008 , Siemens AG, Medical Solutions, Angiography, Fluoroscopic and Radiographic Systems, and the result 2 and 3 can be seen as black and white representations of monitor images.

The 2 Represents an AP projection 11 and the 3 a lateral projection 12 a filled with contrast cerebral vascular tree 13 The usual color display changes from magenta or red for short times, for example, from one second to reaching the contrast medium maximum over green and yellow to blue or violet for long periods of, for example, ten seconds until reaching the maximum contrast, as for example on the pages 6 and 8th the above brochure. An encoding color stripe 14 indicates in a known manner which color is associated with which time of arrival. In the black and white representation, the blue or violet vessels are bright and the red vessels are rendered dark.

However, since the images thus generated are accumulated projection images, it is difficult to make exact diagnoses due to vessel overlaps. Therefore, research is currently being carried out on different approaches in order to be able to display the flow information in three-dimensional space.

The invention is based on the object of enabling a visualization of different parameters of the contrast medium course of cerebral vessels as a color-coded 3-D vessel volume in a simple manner.

The object is achieved for an investigation method of the type mentioned by the features specified in claim 1. Advantageous embodiments are specified in the dependent claims.

The task is solved for an angiographic examination procedure with the following steps.
S1) Acquisition of a rotation recording without contrast agent with a normal angle range as a mask run for the reconstruction of a mask volume ( 20 )
S2) Acquisition of a filling rotational recording ( 22 ) with contrast agent in an enlarged angular range as a filling run,
S3) reconstruction from the filling rotational recording ( 22 ) a plurality of filling volumes offset from each other by an angle α,
S4) Subtraction of the filling volumes with the mask volume ( 20 ) for generating a plurality of vessel volumes,
S5) generating time curves from the intensity of each voxel of all vessel volumes over time,
S6) Calculation of curve parameters from the time curves and
S7) Visualization of the curve parameters.

As a result, color-coded visualization of different parameters of the contrast agent course of cerebral vessels is possible only from two rotational runs.

Advantageously, the normal angular range according to step S1 has a value of 200 ° for the reconstruction of 200 ° filling volumes.

It has proved to be advantageous if the enlarged angular range according to step S2 for the acquisition of a filling rotational recording has a value of ≥ 360 °.

According to the invention, the acquisition of a filling rotational recording with contrast agent according to step S2 can be carried out with a shortened contrast agent injection.

It has proved to be advantageous if the reconstruction of a plurality of filling volumes according to step S3 is carried out as a nested reconstruction (interleaved reconstruction).

• – das erste 200°-Füllungsvolumen aus den Projektionen der Angulationen 0°–200°,
• – das zweite 200°-Füllungsvolumen aus den Projektionen der Angulationen α – 200° + α,
• – ein drittes 200°-Füllungsvolumen aus den Projektionen der Angulationen 2α – 200° + 2α, usw. bis
• – das letzte 200°-Füllungsvolumen aus den Projektionen der Angulationen nα – 200° + nα gebildet werden.

Advantageously, the Reconstruction from the 360 ° fill rotation recording

• The first 200 ° filling volume from the projections of the angulations 0 ° -200 °,
• The second 200 ° filling volume from the projections of the angulations α - 200 ° + α,
• - a third 200 ° filling volume from the projections of the angulations 2α - 200 ° + 2α, etc. to
• - The last 200 ° filling volume from the projections of the angulations nα - 200 ° + nα are formed.

• – das erste 200°-Füllungsvolumen aus den Projektionen der Angulationen 0°–200°,
• – das zweite 200°-Füllungsvolumen aus den Projektionen der Angulationen 10°–210°,
• – ein drittes 200°-Füllungsvolumen aus den Projektionen der Angulationen 20°–220°, usw. bis
• – das letzte 200°-Füllungsvolumen aus den Projektionen der Angulationen 160°–360° gebildet werden kann.

According to the invention, the angle α may have a value of 10 ° in accordance with step S3, so that for the reconstruction from the 360 ° -fill rotation recording

• The first 200 ° filling volume from the projections of the angulations 0 ° -200 °,
• The second 200 ° filling volume from the projections of the angulations 10 ° -210 °,
• - a third 200 ° filling volume from the projections of the angulations 20 ° -220 °, etc. to
• - The last 200 ° filling volume can be formed from the projections of the angulations 160 ° -360 °.

According to the invention, the time curves according to step S5 can be time-intensity curves and / or time-contrast curves, wherein the parameter time-to-peak can be used as the curve parameter according to step S5.

In an advantageous manner, the curve parameters for visualization according to step S7 can be displayed in the colors corresponding to the values and / or assigned.

The invention is explained in more detail with reference to embodiments shown in the drawing. Show it:

1 a known C-arm angiography system with an industrial robot as a carrying device,

2 a black and white reproduction of a color AP projection of the time-to-peak of the contrast agent,

3 a black-and-white reproduction of a colored lateral projection of a contrast-filled cerebral vascular tree,

4 a DSA method according to the invention,

5 a 3-D DSA image,

6 a representation for explaining the so-called Interleaved Reconstruction,

7 Process steps of an angiographic examination method according to the invention and

8th an encoded according to the invention 3-D-DSA recording.

For example, in 2 DSA method according to the invention shown is a rotation recording without contrast agent with an angular range of 200 ° as a mask run for the reconstruction of a mask volume 20 (only anatomy with, for example, a skull 21 ) generated. The following is a filling rotation recording 22 with an angular range of ≥ 360 ° from the entire filling phase, in which a vascular tree 23 filled with contrast agent, acquired. From this filling rotation recording 22 will now be several filling volumes 24 (1 to n) reconstructed with an angular range of 200 °.

The filling volumes 24 ₁ to 24 _n , where the skull 21 and the contrast agent filled vascular tree 23 can be seen, and the mask volume 20 be in a subtraction stage 25 deducted from each other. Other image processing steps, such as contrast adjustment, edge enhancement, etc., may follow until vessel volumes 26 ₁ to 26 _n receives, in which only the vascular tree 23 ₁ to 23 _n is clearly visible in different filling phases, wherein the representation usually takes place in such a way that the vessel tree 23 bright against a dark background appears.

Subsequently, for every single voxel of all vessel volumes 26 ₁ to 26 _n Generate contrast intensity curves from varying intensity over time, from which curve parameters such as time-to-peak can be calculated. These curve parameters can then be displayed on a monitor on the monitor 9 Visualize in a known manner.

In the 5 is now a real view of a 3-D DSA recording 18 a real vascular tree 23 as an example of the filling volumes 24 ₁ to 24 _n shown.

Based on 6 Below is the division of the filling rotation recording according to the invention 22 with an angular range of ≥ 360 ° in the filling volumes 24 ₁ to 24 _n explained in more detail for their reconstruction. From the entire coverage area 30 the filling rotation recording 22 becomes a starting angle 31 set the first filling volume, usually with the starting angle of the filling rotation recording 22 matches. The detection area shown in dashed lines 32 of the first filling volume 24 ₁ ends after 200 ° at the end angle 33 of the first filling volume 24 ₁ . Offset by an angle α, a starting angle begins 34 a second filling volume 24 ₂ , its coverage 35 dotted and after 200 ° at the end angle 36 of the second filling volume 24 ₂ ends. At an angle of 2α with respect to the first starting angle 31 offset, starts a starting angle 37 of the third filling volume 24 ₃ , to which the dash-dotted detection area 38 of the third filling volume 24 ₃ to the third end angle 39 followed.

Offset by a further angle α, begins a detection area shown with large lines 41 the fourth filling volume 24 ₄ from a starting angle 40 to the end angle 42 the fourth filling volume 24 ₄ .

Based on 7 the method steps of an angiographic examination method according to the invention are explained in more detail.

In a first step S1, an acquisition of a mask volume takes place 20 in that a rotation recording without contrast agent with an angle range of 200 ° is detected as a mask run, from which the mask volume 20 is reconstructed.

Subsequently, according to a second step S2, an acquisition of a filling rotational recording 22 performed with contrast agent in an angular range of ≥ 360 ° and a shortened contrast agent injection as a filling run. Such contrast agents have a typical length or duration of 1 to 2 seconds. On the other hand, in a 3-D scan contrast agent typically needs to be injected over the entire time of 3-D acquisition (+1 to 4 sec. X-Ray Delay) for a total of approximately 10 seconds on average.

• – das erste 200°-Füllungsvolumen 24 ₁ aus den Projektionen der Angulationen 0°–200°,
• – das zweite 200°-Füllungsvolumen 24 ₂ aus den Projektionen der Angulationen 10°–210°,
• – ein drittes 200°-Füllungsvolumen 24 ₃ aus den Projektionen der Angulationen 20°–220°, usw. bis
• – das letzte 200°-Füllungsvolumen 24 _n aus den Projektionen der Angulationen 160°–360°

gebildet werden.According to a third step S3, reconstructions are made from the filling rotational recording 22 a plurality of 200 ° filling volumes offset from one another by an angle α with a value of, for example, 10 ° 24 ₁ to 24 _n according to the principle of nested reconstruction (Interleaved Reconstruction). For reconstruction from the 360 ° -fill rotation recording 22 for example

• - the first 200 ° filling volume 24 ₁ from the projections of the angulations 0 ° -200 °,
• - the second 200 ° filling volume 24 ₂ from the projections of the angulations 10 ° -210 °,
• - a third 200 ° filling volume 24 ₃ from the projections of the angulations 20 ° -220 °, etc. to
• - the last 200 ° filling volume 24 _n from the projections of the angulations 160 ° -360 °

be formed.

In a fourth step S4, subtractions of the filling volumes take place 24 ₁ to 24 _n , where the skull 21 and the contrast agent filled vascular tree 23 can be seen with the mask volume 20 in the subtraction stage 25 for generating a plurality of vessel volumes 26 ₁ to 26 _n , in which only the vascular tree 23 ₁ to 23 _n can be recognized in different filling phases.

According to a fifth step S5, time curves, for example time-intensity curves and / or time-contrast curves, are generated from the intensity of each individual voxel of all vessel volumes over time.

From these time curves, for example the contrast intensity curves, curve parameters such as time-to-peak, the elapsed time until reaching the contrast medium maximum, are calculated as the sixth step S6.

In a seventh and last step S7, a color-coded visualization of the curve parameters takes place.

In the 8th is such a color-coded 3-D DSA vascular tree 50 shown in black and white, wherein progressive curve parameters such as time-to-peak, the elapsed time to reach the maximum contrast, are color coded accordingly. However, instead of colored coding, the curve parameters can also be distinguished by different black-and-white patterns of the 3-D DSA vascular tree 50 to be marked.

The usual color display changes from magenta or red for a short time, for example one second, until reaching the contrast agent peak over green and yellow to blue or violet for long times, for example ten seconds, until the contrast agent peak is reached. For example, there is a magenta colored area 51 for short times of, for example, one second until reaching the maximum contrast level. The times until the peak of the contrast agent reach the red-colored area are longer 52 , the yellow colored area 53 , over the green colored area 54 to the blue or violet colored area 55 ,

The method according to the invention makes it possible to visualize different parameters of the contrast medium course of cerebral vessels as a color-coded 3-D vessel volume.

The approach is based on an interleaved reconstruction protocol and a new C-arm technology based on the 1 has been described and which makes it possible to perform C-arm rotations of 360 ° and more.

In a first phase, the so-called mask run, a standard 200 ° rotation recording is performed, which is the three-dimensional mask volume 20 is reconstructed. This mask volume 20 should later serve to remove bones and tissue from the shots of the filling run. In a normal 3-D DSA, the normal filling run would now follow, in which another 200 ° rotation shot would be performed with contrast agent delivery. For the color-coded method, the filling run should now be adapted. Instead of a rotational recording at 200 ° according to the invention, the filling rotation recording 22 performed with an angle of ≥ 360 ° and a shortened contrast agent injection. From this filling rotation recording 22 Now several 3-D volumes are reconstructed. The first 200 ° of the 360 ° recording will be for a first 3-D reconstruction of a first 200 ° fill volume 24 ₁ used. A second reconstruction of a second 200 ° filling volume 24 ₂ takes place, for example, from the projections of the angulations 10 ° -210 °, a third reconstruction of a third 200 ° filling volume 24 ₃ from the projections 20 ° -220 °, etc.

The last reconstruction of the 200 ° filling volume 24 _n is based on the 160 ° -360 ° projections (Interleaved Reconstruction, as used for example by the 6 was explained). Subtract each individual volume with the previously prepared mask volume 20 , you get a number n of different 3-D vessel volumes 26 ₁ to 26 _n . In these n vessel volumes 26 ₁ to 26 _n corresponding voxels are contrasted in different degrees, since the reconstructions reflect different phases of the contrast medium course from arterial to venous phase. By considering the intensity of a single voxel over all n vial volumes 26 ₁ to 26 _n , ie over time, one can generate a time-intensity curve, or time-contrast curve. Similar to the two-dimensional case, curve parameters such as time-to-peak can be calculated from this curve and displayed in color (see 8th ).

By this method, a color-coded representation of flow characteristics of cerebral vessels in three-dimensional space by a single 360 ° rotational recording in angiography is possible.

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 7500784 B2 [0001, 0003]

Cited non-patent literature

• Charles M. Strother et al. in "Parametric Color Coding of Digital Subtraction Angiography" AJNR Am J Neuroradiol, 2010 [0011]
• "syngo iFlow / Dynamic Flow Evaluation / Answers for life", Order no. A91AX-20902-11C1-7600, printed CC AX WS 12081.5, 12.2008 [0012]

Claims (11)

Angiographic examination method for the representation of flow characteristics of vessels ( 13 . 23 ) of an examination object ( 6 . 21 ) comprising the following steps: S1 acquisition of a contrast-free rotation image with a normal angle range as a mask run to reconstruct a mask volume ( 20 ), S2 acquisition of a filling rotational recording ( 22 ) with contrast agent in an enlarged angle range as a filling run, S3 reconstruction from the filling rotation recording (FIG. 22 ) a plurality of filling volumes offset from each other by an angle α ( 24 ₁ to 24 _n ), S4 subtraction of the filling volumes ( 24 ₁ to 24 _n ) with the mask volume ( 20 ) for generating a plurality of vessel volumes ( 26 ₁ to 26 _n ), S5 Generation of time curves from the intensity of each voxel of all vessel volumes ( 26 ₁ to 26 _n ) over time, S6 Calculation of curve parameters from the time curves and S7 visualization of the curve parameters. An angiographic examination method according to claim 1, characterized in that the normal angular range according to step S1 has a value of 200 ° for the reconstruction of 200 ° filling volumes ( 24 ₁ to 24 _n ). Angiographic examination method according to claim 1 or 2, characterized in that the enlarged angular range according to step S2 for the acquisition of a filling rotational recording ( 22 ) has a value of ≥ 360 °. Angiographic examination method according to one of claims 1 to 3, characterized in that the acquisition of a filling rotational recording ( 22 ) is performed with contrast agent according to step S2 with a shortened contrast agent injection. Angiographic examination method according to one of claims 1 to 4, characterized in that the reconstruction of multiple filling volumes ( 24 ₁ to 24 _n ) is performed as a nested reconstruction according to step S3. Angiographic examination method according to one of claims 1 to 5, characterized in that for the reconstruction of the 360 ° -filling rotation recording ( 22 ) - the first 200 ° filling volume from the projections of the angulations 0 ° -200 °, - the second 200 ° filling volume from the projections of the angulations α - 200 ° + α, - a third 200 ° filling volume from the projections of the angulations 2α - 200 ° + 2α, etc. until - the last 200 ° filling volume is formed from the projections of the angulations nα - 200 ° + nα. Angiographic examination method according to one of claims 1 to 6, characterized in that the angle α according to step S3 has a value of 10 °. Angiographic examination method according to one of claims 1 to 7, characterized in that for the reconstruction of the 360 ° -filling rotation recording ( 22 ) - the first 200 ° filling volume from the projections of the angulations 0 ° -200 °, - the second 200 ° filling volume from the projections of the angulations 10 ° -210 °, - a third 200 ° filling volume from the projections of the angulations 20 ° -220 °, etc. until - the last 200 ° filling volume is formed from the projections of the angulations 160 ° -360 °. An angiographic examination method according to any one of claims 1 to 8, characterized in that the time curves according to step S5 are time-intensity curves and / or time-contrast curves. Angiographic examination method according to one of claims 1 to 9, characterized in that as a curve parameter according to step S5, the parameter time-to-peak is used. Angiographic examination method according to one of claims 1 to 10, characterized in that the curve parameters for visualization according to step S7 in the values corresponding and / or associated colors are displayed.

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