Angiographic method for examining a vascular system
View Patent ↗An angiographic method is provided. The method includes: identification of a relevant part in acquired angiography 4D sequences which exhibit a vascular disorder or change; determination of a centerline for the part; ascertainment of lines parallel and surrounding the centerline; specification of perpendicular cross-sections; determination of voxels; ascertainment of bolus curves as a function of time for each voxel; which intersects one of the cross-sections; determination of a time for each voxel; measurement of the true Euclidean distance between voxels at the positions along the centerline and the parallel lines; division of the measured distance by the time difference; determination of second speed components, running transversely, proportional to the relative change in mass for each voxel; and calculation of the blood flow in the relevant part of the vascular system on the basis of the speed components.
1. An angiographic method for examining a vascular system of an object under examination in order to determine flow characteristics inside vessels, comprising:
S 1 ) acquiring 4D angiography sequences;
S 2 ) identifying a relevant part of the vascular system in the 4D angiography sequences which could exhibit a vascular disorder or vascular change;
S 3 ) determining a centerline for the identified relevant part;
S 4 ) ascertaining of parallel lines which run parallel to the centerline and surround the centerline;
S 5 ) specifying perpendicular cross-sections at least at positions which can be determined or chosen along the centerline;
S 6 ) determining voxels lying on the perpendicular cross-sections;
S 7 ) ascertaining bolus curves as a function of time for each voxel which intersects one of the cross-sections;
S 8 ) determining a time for each of said voxels;
S 9 ) measuring of the true Euclidean distance between voxels at the positions along the centerline and the parallel lines;
S 10 ) dividing said measured distance by the time difference in order to obtain the amplitude of a first speed component of the blood flow speed in each of said voxels;
S 11 ) determining second speed components, running transversely, proportional to the relative change in mass of the blood in the voxels, for each of said voxels and
S 12 ) calculation of the blood flow in the relevant part of the vascular system on the basis of the speed components.
2. The angiographic examination method as claimed in claim 1 ,
wherein the acquisition of the 4D angiography sequences takes place in accordance with step S 1 ) from rotational angiography projections which are superimposed by means of perspective back projection in a static 3D image of the vascular tree.
3. The angiographic examination method as claimed in claim 1 ,
wherein the calculation of the second speed components, running transversely occurs in accordance with S 11 ) according to the formula:
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4. The angiographic examination method as claimed in claim 2 ,
wherein the calculation of the second speed components, running transversely occurs in accordance with S 11 ) according to the formula:
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5. The angiographic examination method as claimed in claim 1 ,
wherein accordance with S 8 ) the time is the maximum time, rise time of the wash-in phase and/or fall time of the wash-out phase of the bolus curve.
6. The angiographic examination method as claimed in claim 2 ,
wherein accordance with S 8 ) the time is the maximum time, rise time of the wash-in phase and/or fall time of the wash-out phase of the bolus curve.
7. The angiographic examination method as claimed in claim 3 ,
wherein accordance with S 8 ) the time is the maximum time, rise time of the wash-in phase and/or fall time of the wash-out phase of the bolus curve.
8. The angiographic examination method as claimed in claim 1 ,
wherein after calculation of the first speed component for each voxel in accordance with S 10 ) all adjacent voxels are examined as to whether relative changes exist in the masses m(i+1, k+) to m(i, k+), and only then is the transversely running speed component, which exhibits a value proportional to the relative change in mass, determined in order to determine second speed components in accordance with S 11 ) for a voxel.
9. The angiographic examination method as claimed in claim 2 ,
wherein after calculation of the first speed component for each voxel in accordance with S 10 ) all adjacent voxels are examined as to whether relative changes exist in the masses m(i+1, k+) to m(i, k+), and only then is the transversely running speed component , which exhibits a value proportional to the relative change in mass, determined in order to determine second speed components in accordance with S 11 ) for a voxel.
10. The angiographic examination method as claimed in claim 3 ,
wherein after calculation of the first speed component for each voxel in accordance with S 10 ) all adjacent voxels are examined as to whether relative changes exist in the masses m(i+1, k+) to m(i, k+), and only then is the transversely running speed component , which exhibits a value proportional to the relative change in mass, determined in order to determine second speed components in accordance with S 11 ) for a voxel.