EXAMINING BLOOD FLOW PATTERNS IN THE BLOOD VESSELS OF A PATIENT USING PHASE CONTRAST MRI

Abstract

The invention relates to a technique for examining blood flow patterns in the blood vessels of a patient (1), the technique having the following features: collecting raw data from a time- and space-resolved MRI phase contrast measurement of the cardiovascular system of a patient or parts thereof (1), or reading such data or data determined therefrom via an input interface (3), and calculating at least one primary variable which quantifies the blood flow pattern; carrying out multi-plane reconstructions on the basis of at least one calculated primary variable along a defined path (9) which reproduces the course of a blood vessel of the patient (1) to obtain a local distribution of the at least one primary variable in the vessel cross-section; and calculating and outputting at least one secondary variable which quantifies the blood flow pattern as a function of the position along the course of the vessel on the basis of the at least one primary variable after carrying out the multi-plane reconstructions.

Claims

1. A method for examining blood flow patterns in a blood vessel of a patient, comprising: a) capturing raw data of a time- and space-resolved MRI phase-contrast measurement of a cardiovascular system of a patient or parts thereof, or reading the raw data and/or data determined therefrom by way of an input interface, and calculating at least one primary quantity that quantifies a the blood flow pattern; b) performing multiplanar reconstructions along a set path on a basis of the at least one primary quantity calculated in method step (a), said set path reproducing a course of a blood vessel of the patient, to obtain a spatial distribution of the at least one primary quantity in a vessel cross section of the blood vessel; c) calculating and outputting at least one secondary quantity which quantifies the blood flow pattern as a function of position along the course of the blood vessel on the basis of the at least one primary quantity following the performance of the multiplanar reconstructions.

2. The method as claimed in claim 1, wherein the at least one secondary quantity includes a plurality of secondary quantities each of which are output as a function of time and position along the course of the blood vessel.

3. The method as claimed in claim 1 wherein the multiplanar reconstructions are performed continuously along the set path.

4. The method as claimed in claim 1 wherein the at least one primary quantity includes a plurality of primary quantities, and wherein one of the primary quantities is vorticity () or turbulent kinetic energy density (TKE).

5. The method as claimed in claim 1 further comprising determining one or more secondary complex quantities which quantify the blood flow pattern as a function of the position along the course of the blood vessel on a basis of the at least one primary quantity following the performance of the multiplanar reconstruction and outputting the one or more secondary complex quantities, wherein the one or more secondary complex quantities are selected from the group consisting of turbulent kinetic energy density related to the vessel cross section or a corresponding layer, turbulent kinetic energy, root mean square turbulent kinetic energy, helicity density, helicity, and relative helicity density.

6. The method as claimed in claim 1 wherein the multiplanar reconstructions of at least two primary quantities are performed once for all primary quantities in a multidimensional space.

7. The method as claimed in claim 1 wherein at least two of the following secondary quantities are determined, to be precise in parallel, on the basis of the at least one primary quantity following the performance of the multiplanar reconstruction and where at least one of the at least two secondary quantities is selected from the group consisting of turbulent kinetic energy density related to the vessel cross section or a corresponding layer, turbulent kinetic energy, root mean square turbulent kinetic energy density, helicity density, helicity, relative helicity density, circulation rate, mean vorticity, mean flow velocity, maximum flow velocity, blood flow (volume per unit time), eccentricity, and, where at least one of the at least two secondary quantities is selected from a relation to the position along the course of the blood vessel, a local radii of curvature of the course of the blood vessel, local torsion of the course of the blood vessel, and size of the vessel cross section.

8. The method as claimed in claim 1 wherein the course of the blood vessel in the body of the patient is represented by a central line which is determined by either a) manually set position marks in a the-center of the respective vessel cross section being interconnected by a smooth curve or b) semiautomatic or automatic processes of central line detection.

9. The method as claimed in claim 8, wherein a plane of capture of three-dimensional raw data by MRI measurements is defined at each point of the central line, said plane of capture being disposed in orthogonal fashion on the central line in each case.

10. The method as claimed in claim 1 wherein the vessel is selected by an automatic or semiautomatic segmentation technique and the calculation in method step (c) is restricted to a corresponding selection.

11. A computer program product comprising computer executable instructions encoded on a non-transient medium, wherein said instructions, when executed by a computer configured to perform the method as claimed in claim 1.

12. A device for determining complex quantities, and quantifying a blood flow pattern of blood flowing in a vessel of a patient, comprising: a) an input interface configured to read raw data of a time- and space-resolved MRI phase-contrast measurement of a cardiovascular system of the patient or parts thereof, or data determined therefrom, b) a computing unit configured to carry out the method as claimed in claim 1, c) an output interface configured to output at least one complex quantity, quantifying the blood flow pattern, of the blood flow through the vessel on the basis of results of the continuously performed multiplanar reconstructions.

13. The device as claimed in claim 12, wherein the device comprises an MRI measuring device coupled to the input interface

Description

[0040] The invention is explained in more detail below on the basis of exemplary embodiments, with use being made of the drawings.

[0041] In the drawings:

[0042] FIG. 1 shows a device for determining complex fluid dynamic flow variables;

[0043] FIG. 2 shows a schematic illustration of a blood vessel with geometric and fluid dynamic peculiarities;

[0044] FIG. 3 shows the schematic illustration of four secondary quantities obtained from FIG. 2; and

[0045] FIG. 4 shows further graphical representations of secondary quantities.

[0046] The device for determining complex fluid dynamic flow quantities, represented in a schematic illustration in FIG. 1, comprises a computer device 4 with a computing unit 7 (processor unit). The computer device 4 further comprises a memory or is connected to a memory, in which a computer program for executing the method according to the invention is stored. The method is executed by the computing unit 7. The computing device 4 comprises an input interface 3, by means of which the computing device 4 is coupled to an MRI installation or, at least, to an MRI measuring device 2. By means of the MRI measuring device 2, it is possible to capture body-internal data of a patient 1 by way of magnetic resonance imaging, for example the vessels of said patient and fluids flowing therein. The computing device 4 further comprises an output interface 5, to which further appliances can be connected. What is illustrated in exemplary fashion is that a display device 6, for example in the form of an image display device, is connected to the output interface 5. The complex fluid dynamic flow quantities ascertained by the computing device 4 and further quantities can be visually output, for example in the form of diagrams, on the display unit 6. Examples of image representations on the image display appliance 6 are shown in FIGS. 2 to 4.

[0047] For elucidation purposes, a vessel portion of the patient 1 is schematically illustrated in FIG. 2, said vessel portion extending from point A to point E. The dotted line 9 is the central line of the vessel. As an example of the continuously performed multiplanar reconstructions, a plane aligned orthogonal to the central line 9 is illustrated. The vessel course is curved in the surroundings of the position B. The vessel is constricted at position C and dilated at position D. The blood flow exhibits a helical pattern at position B. The blood flow exhibits turbulences at position D.

[0048] FIG. 3 schematically illustrates, by way of example, selected results of fluid dynamic and geometric quantities, which can be collected by the computing device for the case illustrated in FIG. 2 by means of the method according to the invention. The longitudinal vessel position is plotted along the abscissa. The cross-sectional area is plotted on the ordinate in diagram (a) and the turbulent kinetic energy density (TKE) is plotted on the ordinate in diagram (b). High turbulent energy means a loss of kinetic flow energy. The effective torsion (product of curvature and torsion) is plotted on the ordinate in diagram (c) and the helicity is plotted in diagram (d). A high helicity describes flow patterns with great rotation and forward motion. The helicity illustrated in diagram (d) is positive, i.e., the helical flow pattern corresponds to the winding of a right-handed screw. The classification of process and presentation of the results allows statistically evaluable relationships between vessel geometry and flow dynamics to be uncovered and quantified.

[0049] A plurality of quantities determined from the MRI data can also be output simultaneously by the computing unit 4, as shown in FIG. 4. There, the circulation of the blood flow in the vessel is illustrated in diagram (a), the helicity of the blood flow is illustrated in diagram (b), the relative helicity density of the blood flow is illustrated in diagram (c), the speed of the blood flow is illustrated in diagram (d), the flow rate of the blood flow is illustrated in diagram (e), the vessel diameter is illustrated in diagram (f), the torsion of the vessel is illustrated in diagram (g) and the turbulent kinetic energy of the blood flow is illustrated in diagram (h), in each case over the spatial coordinate in the vessel 8, which has already been mentioned with reference to FIG. 3. Each of the flow quantities was measured in 24 equidistant phases within the cardiac cycle. Each of the diagrams plots the curves of all phases in distinguishable fashion. The described invention supplies, with a few user specifications, clinically relevant, highly resolved information for the comprehensive and, at the same time, simple and systematic examination of the blood flow.

[0050] [1] Lorenz, R. [et al]: 4D flow magnetic resonance imaging in bicuspid aortic valve disease demonstrates altered distribution of aortic blood flow helicity. In: Magnetic resonance in medicine, vol. 71, 2014, no. 4, pp. 1542-1553

TABLE-US-00001 TABLE 1 Variables and formulas i = 1, . . . , n Pixels of the vessel cross section j = 1, . . . , 3 Spatial directions r.sub.i Position vectors of the pixels v Velocity Speed .sup.1 Orthogonal velocity component A Cross-sectional area Density of the fluid .sub.enc.sup.j Velocity encoding in direction j |S| Signal magnitude without first-order velocity encoding |S.sub.j| Signal magnitude with velocity encoding in direction j = v Vorticity [00001]$={}_A.Math..Math..Math..Math.\mathrm{dA}$ Circulation rate [00002]$=\frac{{}_A.Math..Math..Math.d.Math..Math.A.Math.}{A}$ Mean vorticity H.sub.d = v .Math. Helicity density H [00003]$={}_A.Math..Math.v.Math..Math..Math.\mathrm{dA}$ Helicity H.sub.r [00004]$=\frac{v.Math.}{.Math.v.Math..Math..Math..Math.}$ Relative helicity density E [00005]$=\frac{{.Math.}_i.Math.r_i.Math..Math.v_i.Math.}{{.Math.}_i.Math..Math.v_i.Math.}-\frac{{.Math.}_i.Math.r_i}{n}$ Eccentricity TKE [00006]$=.Math.\underset{\mathrm{ji}=1}{\overset{a}{.Math.}}.Math.v_{\mathrm{enc}}^{\mathrm{ij}}.Math.\ln \left(\frac{.Math.S.Math.}{.Math.S_i.Math.}\right)$ Turbulent kinetic energy density [1] [1] Dyverfeldt, P., Sigfridsson, A., Kvitting, J.-P. E. and Ebbers, T. (2006), Quantification of intravoxel velocity standard deviation and turbulence intensity by generalizing phase-contrast MRI. Magn. Reson. Med., 56: 850-858. doi:10.1002/mrm.21022