HEMODYNAMIC PARAMETERS FOR CO-REGISTRATION

Abstract

An apparatus for analyzing a vasculature of a patient and a corresponding method are provided in which a plurality of simulated hemodynamic parameter values obtained from (non-invasively) acquired diagnostic images are compared to at least one intravascular hemodynamic parameter value acquired during an invasive measurement in a vessel of interest in the vasculature. The comparison allows to uniquely determine the vessel of interest. Based on this information, the assessment of the disease and the potential treatment planning may be improved.

Claims

1. An apparatus for analyzing a vasculature of a patient, comprising an input unit configured to receive a plurality of simulated parameter values determined on the basis of a physiological model derived from diagnostic image data of the vasculature for a plurality of vessels of the vasculature; and at least one intravascular parameter value acquired by an intravascular measurement device from a vessel of interest in the vasculature; and a comparing unit configured to compare each of the plurality of simulated parameter values to the at least one intravascular parameter value; and identify, based on the comparing, the vessel of interest in a reconstruction derived from the diagnostic image data.

2. Apparatus according to claim 1, wherein the diagnostic image data comprises computed tomography (CT) projection data; and the reconstruction comprises volumetric data reconstructed from the computed tomography projection data.

3. Apparatus according to claim 1, wherein the at least one intravascular parameter value is acquired using the intravascular measurement device for pullback recording.

4. Apparatus according to claim 1, further comprising a modeling unit configured to generate the physiological model based on the diagnostic image data of the vasculature, the physiological model representing the fluid dynamics through the plurality of vessels; and a determination unit configured to determine the plurality of simulated parameter values on the basis of the physiological model.

5. Apparatus according to claim 4, wherein the determining the plurality of simulated parameter values comprises determining, for each of the vessels, a respective simulated parameter value; and the identifying the vessel of interest comprises identifying the vessel for which the respective simulated parameter value exhibits the best agreement with the at least one intravascular parameter value.

6. Apparatus according to claim 1, wherein the input unit is further configured to receive at least one additional information indicative of the vessel of interest; wherein the comparing each of the plurality of simulated parameter values to the at least one intravascular parameter value comprises co-registering the at least one intravascular parameter value to the reconstruction of the diagnostic image data based on the at least one additional information; and a deriving, based on the co-registering, the plurality of vessels.

7. Apparatus according to claim 1, wherein the input unit is further configured to receive at least one tracking image of the measurement device; and wherein the comparing each of the plurality of simulated parameter values to the at least one intravascular parameter value comprises a co-registering the at least one tracking image to the reconstruction of the diagnostic image data; and a deriving, based on the co-registering, the plurality of vessels.

8. Apparatus according to claim 7, wherein the measurement device is configured to acquire the at least one parameter value at a particular intravascular position in the vessel of interest; the deriving the plurality of candidate vessels comprises identifying, for each of the vessels, a respective position corresponding to the intravascular position; the determining the simulated parameter values comprises determining, for each of the vessels, a respective simulated parameter value at the respective position; the comparing comprises comparing the at least one intravascular parameter value acquired at the intravascular position to each of the simulated parameter values determined at the respective positions; and the identifying the vessel of interest comprises identifying the position for which the respective simulated parameter value exhibits the best agreement with the at least one intravascular parameter value.

9. Apparatus according to claim 1, further comprising a calculation unit configured to calculate a graphical representation of the at least one intravascular parameter value and a second graphical representation of the reconstruction of the diagnostic image data; and a display unit configured to jointly display the first and second representation.

10. Apparatus according to claim 9, wherein the jointly displaying the first graphical representation and the second graphical representation comprises an annotating the first graphical representation to the second graphical representation.

11. A method for analyzing a vasculature of a patient, the method comprising the steps of: receiving a plurality of simulated parameter values determined on the basis of a physiological model derived from diagnostic image data of the vasculature for a plurality of vessels of the vasculature; receiving at least one intravascular parameter value acquired by an intravascular measurement device from a vessel of interest in the vasculature; comparing each of the plurality of simulated parameter values to the at least one intravascular parameter value; and identifying, based on the comparing, the vessel of interest in a reconstruction derived from the diagnostic image data.

12. Method according to claim 11, further comprising the steps of: receiving at least one tracking image of the measurement device; co-registering the at least one tracking image to the reconstruction of the diagnostic image data; and deriving, based on the co-registering, the plurality of vessels.

13. Method according to claim 11, further comprising the steps of: calculating a graphical representation of the at least one intravascular parameter value and a second graphical representation of the reconstruction of the diagnostic image data; and jointly displaying the first and second representation.

14. A non-transitory computer-readable medium, having program code recorded thereon, the program code comprising: code for causing an apparatus to receive a plurality of simulated parameter values determined on the basis of a physiological model derived from diagnostic image data of the vasculature for a plurality of vessels of the vasculature; code for causing the apparatus to receive at least one intravascular parameter value acquired by an intravascular measurement device from a vessel of interest in the vasculature; code for causing the apparatus to compare each of the plurality of simulated parameter values to the at least one intravascular parameter value; and code for causing the apparatus to identify, based on the comparing, the vessel of interest in a reconstruction derived from the diagnostic image data.

15. Non-transitory computer-readable medium according to claim 14, further comprising: code for causing the apparatus to receive at least one tracking image of the measurement device; code for causing the apparatus to co-register the at least one tracking image to the reconstruction of the diagnostic image data; and code for causing the apparatus to derive, based on the co-registering, the plurality of vessels.

16. Non-transitory computer-readable medium according to claim 14, further comprising: code for causing the apparatus to calculate a graphical representation of the at least one intravascular parameter value and a second graphical representation of the reconstruction of the diagnostic image data; and code for causing the apparatus to jointly display the first and second representation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In the following drawings:

[0072] FIG. 1 shows a diagnostic imaging modality for obtaining diagnostic image data according to an embodiment.

[0073] FIG. 2 schematically illustrates the ambiguity in the co-registration using a back projection of a tracking image to the reconstruction of the vasculature from the prior art.

[0074] FIG. 3 schematically illustrates an apparatus for analyzing a patient's vasculature according to an embodiment.

[0075] FIG. 4 represents a flow chart for a method for analyzing coronary vessels according to an embodiment.

[0076] FIG. 5 schematically illustrates a conclusive determination of a vessel of interest in the reconstruction according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0077] The illustration in the drawings is schematically. In different drawings, similar or identical elements are provided with the same reference numerals.

[0078] FIG. 1 shows a diagnostic imaging modality for obtaining diagnostic image data. In this particular embodiment, the diagnostic imaging modality corresponds to a computed tomography system 1. The computed tomography system 1 comprises an X-ray source 2, such as an X-ray tube, and an X-ray detector 3, which are mounted opposite to each other on a rotatable gantry 4. The gantry 4 may be configured as annular device, a C-arm, or it may be realized by two robotic arms, for example.

[0079] By means of rotating the gantry 4, the X-ray source 2 and the X-ray detector 3 are rotated around an object of interest to be imaged. Hereby, the object of interest is positioned in a measurement region 5 located between the X-ray source 2 and the X-ray detector 3. In the present embodiment, the object of interest is a patient which is assumed to suffer from a coronary artery disease. The computed tomography system 1 is therefore used to image the coronary vasculature of this patient. The computed tomography system 1 is used to obtain diagnostic image data comprising a plurality of diagnostic projection images for different projection angles while rotating the gantry 4 around the patient.

[0080] Hereby, the components of the computed tomography system 1 are controlled by means of a control unit 6, which may be configured as a computer-implemented unit comprising a computer program which includes procedures for controlling the components of the computed tomography system 1 and which is executed in a computer device connected to the components of the computed tomography system 1 in a suitable manner.

[0081] In order to provide a reconstruction from the diagnostic image data comprising the diagnostic projection images, computed tomography system 1 comprises a reconstruction unit 7. The reconstruction unit 7 may likewise be a computer-implemented unit which comprises a computer program that provides procedures for providing a volumetric reconstruction, i.e. volumetric data, from the diagnostic image data.

[0082] In accordance with the invention, the volumetric reconstruction and the diagnostic image data are then provided to an apparatus for analyzing the coronary vasculature by co-registering the volumetric reconstruction to at least one intravascular hemodynamic parameter value that has been acquired in-situ using an intravascular measurement device.

[0083] In that respect, FIG. 2 schematically illustrates the ambiguity in the co-registration of the intravascular measurement and a volumetric reconstruction 30 of the vasculature, when the co-registration is based on a back projection of a tracking image 40 to the volumetric reconstruction 30 as known from the prior art.

[0084] In the exemplary embodiment of FIG. 2, tracking image 40 has been obtained using X-ray fluoroscopy. The tracking image 40 represents a vessel of interest 41, in which an intravascular measurement device has been introduced to acquire at least one intravascular hemodynamic parameter value.

[0085] The tracking image 40 is correlated to the volumetric reconstruction 30 by means of a back projection 51. Thus, the representation of an intravascular measurement position is projected onto a corresponding position in the volumetric reconstruction 30. The back-projection renders two possible candidate positions 32 and 32 in two candidate vessels 31 and 31 in the volumetric reconstruction 30 of the vasculature which may correspond to the intravascular position 42 in the vessel of interest 41 represented in the tracking image 40. From the information provided in FIG. 2, it is not possible to identify which one of the candidate positions 32, 32 is the correct position. Thus, it is not possible to uniquely assign one of the candidate vessels 31, 31 as the vessel of interest in the volumetric reconstruction.

[0086] In order to solve this problem, an improved apparatus 8 for analyzing a patient's vasculature according to an exemplary embodiment is illustrated in FIG. 3. Apparatus 8 comprises a modeling unit 100, a determination unit 200, an input unit 300, a comparing unit 400, a calculation unit 500 and a display unit 600.

[0087] The modeling unit 100 receives diagnostic image data 10 comprising a plurality of diagnostic projection images. The modeling unit 100 may segment the imaged vessels and generate a physiological model on the basis of this segmentation. The physiological model hereby represents the fluid dynamics through each of the modeled vessels. The modeling unit 100 then provides the physiological model to determination unit 200.

[0088] The determination unit 200 receives the physiological model generated based on diagnostic image data 10. Further, the determination unit 200 may optionally receive information regarding a plurality of candidate positions from the input unit 300. The determination unit 200 then uses the physiological model to determine, for each of the candidate vessels 31, 31, at least one respective simulated hemodynamic parameter value. In this particular example, the determination unit 200 uses the physiological model to determine, for each of the candidate vessels 31, 31 a respective simulated hemodynamic parameter value at a respective candidate position 32, 32 in the candidate vessel 31, 31.

[0089] In this exemplary embodiment, these candidate vessels 31, 31 and their candidate positions 32, 32 have been determined by the input unit 300 based on the tracking image 40. More specifically, the input unit 300 receives the tracking image 40 from a fluoroscopic imaging modality and the volumetric reconstruction 30 from the reconstruction unit 7 of computed tomography system 1. Furthermore, the input unit 300 received an intravascular hemodynamic parameter value 20 from an intravascular measurement device which has been acquired in-situ at a specific intravascular position.

[0090] Based on the tracking image 40, the input unit 300 may derive a plurality of candidate vessels 31, 31 in the volumetric reconstruction 30 by co-registering the tracking image 40 and the volumetric reconstruction 30. In the example according to FIG. 3, this is achieved by correlating the two imaging modalities by determining, for each candidate vessel 31, 31 in the volumetric reconstruction 30, a candidate position 32, 32 that may correspond to the intravascular position in the vessel of interest at which the intravascular hemodynamic parameter value 20 has been obtained. This intravascular position is hereby derived from the tracking image 40.

[0091] The input unit 300 then provides respective information about the plurality of candidate positions 32, 32 to the determination unit 200, upon which the determination unit 200 determines the plurality of simulated hemodynamic parameter values. In the exemplary embodiment, the determination unit 200 particularly determines a simulated hemodynamic parameter value for each one of the candidate positions 32, 32 as described above and then provides the plurality of simulated hemodynamic parameter values to the input unit 300.

[0092] The input unit 300 then provides the plurality of simulated hemodynamic parameters, optionally along with their respective candidate positions 32, 32, as well as the intravascular hemodynamic parameter value 20 and the volumetric reconstruction 30 to the comparing unit 400.

[0093] The comparing unit 400 compares each of the simulated hemodynamic parameter values to the intravascular hemodynamic parameter value 20 and identifies the simulated hemodynamic parameter value that shows the highest agreement with the intravascular hemodynamic parameter value 20.

[0094] In this manner, the comparing unit 400 identifies the candidate vessel 31, 31 for which the simulated hemodynamic parameter value shows the best agreement to intravascular hemodynamic parameter value 20, which has been obtained in situ in the vessel of interest. Thereby, the comparing unit 400 identifies the vessel of interest in volumetric reconstruction 30. Comparing unit 400 then provides the information about the identified vessel of interest in the volumetric reconstruction 30 along with the volumetric reconstruction 30 and the intravascular hemodynamic parameter value 20 to the calculation unit 500.

[0095] Calculation unit 500 calculates a first representation of the intravascular hemodynamic parameter value 20 and a second representation of the volumetric reconstruction 30. Calculation unit 500 then provides the first and second representation to the display unit 600.

[0096] Based on the identification of the vessel of interest in the volumetric reconstruction 30 and the intravascular hemodynamic parameter value 20 the display unit 600 then jointly displays the first and the second representation. In the exemplary embodiment according to FIG. 3, the joint display is performed by annotating the first representation to a specific position in the second representation. This specific position may correspond or be proximate to the position indicating the intravascular position in the volumetric reconstruction 30. The annotation may hereby particularly performed by inserting the first representation into the second representation and further inserting a graphical illustration of an indicator, such as an arrow, to indicate the identified position.

[0097] FIG. 4 schematically illustrates a flow chart for a method for analyzing the coronary vasculature according to an embodiment. In the exemplary embodiment of FIG. 4, the diagnostic image data 10 is received, in step S101, at the modeling unit 100 and segmented to generate the physiological model. In step S102, the modeling unit 100 generates the physiological model and provides the physiological model to the determination unit 200.

[0098] In the exemplary embodiment of FIG. 4, information regarding the candidate positions 32, 32 is provided to the determination unit 200. This information is determined by the input unit 300. Therefore, in this particular example, a subset of the steps performed by the input unit 300 are performed at the same time as the steps performed by the modeling unit 100. More particularly, in step S301, the input unit 300 receives the intravascular hemodynamic parameter value 20, the volumetric reconstruction 30 and the tracking image 40. In step S302, the input unit determines, based on a co-registration of the tracking image 40 and the volumetric reconstruction 30, the plurality of the candidate positions 32, 32 and provides them to the determination unit 200 in step S303.

[0099] In step S201, the physiological model is received at the determination unit 200 from the modeling unit 100. Optionally, in step S201, further the information regarding the candidate positions 32, 32 is received from the input unit 300. Subsequently, in step S202, the determination unit 200 determines a plurality of simulated hemodynamic parameter values. In the specific example of FIG. 4, where the determination unit 200 has received information regarding the candidate positions 32, 32, the determination unit 200 determines a simulated hemodynamic parameter value for each candidate position 32, 32. The plurality of the thus determined simulated hemodynamic parameter values is then, in this example along with the respective information about the corresponding candidate positions 32, 32, provided to the input unit 300.

[0100] In step S304, the input unit 300 receives the plurality of simulated hemodynamic parameters. In the exemplary embodiment according to FIG. 4, each of the simulated hemodynamic parameter values is received along with its respective candidate position 32, 32. In step S305, the input unit 300 provides the plurality of simulated hemodynamic parameters, optionally along with their respective candidate positions 32, 32, as well as the intravascular hemodynamic parameter value 20 and the volumetric reconstruction 30 to the comparing unit 400.

[0101] Comparing unit 400 compares, in step S401, each of the simulated hemodynamic parameter values to the intravascular hemodynamic parameter value 20. In step S402, the comparing unit 400 identifies the simulated hemodynamic parameter value that matches the intravascular hemodynamic parameter value 20 the best, thereby identifying the vessel of interest in the volumetric reconstruction 30. According to the exemplary embodiment of FIG. 4, the comparing unit 400 then provides an identification of the vessel of interest in the volumetric reconstruction 30 together with the volumetric reconstruction 30 and the intravascular hemodynamic parameter value 20 to the calculation unit 500 in step S403.

[0102] In step S501, the calculation unit 500 calculates a first representation of the intravascular hemodynamic parameter value 20. In step S502, the calculation unit 500 calculates a second representation of the volumetric reconstruction 30. In step S503, the calculation unit 500 provides first and second representation to the display unit 600. In step S601, the display unit 600 annotates the first graphical representation to the second graphical representation. In step S602, the display unit jointly displays the first and second graphical representation.

[0103] FIG. 5 schematically illustrates the principle of an identification of the vessel of interest in a volumetric reconstruction from two candidate vessels 31, 31 by comparing the simulated hemodynamic parameter value calculated for two candidate positions 32, 32 to an intravascular hemodynamic parameter value 20.

[0104] In the exemplary embodiment of FIG. 5, the hemodynamic parameter value corresponds to a value of the fractional flow reserve (FFR). As such, the simulated hemodynamic parameter value corresponds to a simulated FFR value and the intravascular hemodynamic parameter value 20 corresponds to an FFR value that has been acquired in-situ from the vessel of interest.

[0105] In FIG. 5, the first simulated hemodynamic parameter value at first candidate position 32 in first candidate vessel 31 has been calculated as 0.58. The second simulated hemodynamic parameter value at second candidate position 32 in second candidate vessel 31 has been calculated as 0.88. The intravascular hemodynamic parameter value 20 has been determined as 0.58. Thus, a comparison between first and second simulated hemodynamic parameter value with the intravascular hemodynamic parameter value 20, respectively, shows a higher agreement between first simulated hemodynamic parameter value with the intravascular hemodynamic parameter value 20. Thus, first candidate vessel 31 is determined to be the vessel of interest 31 in the volumetric reconstruction 30 and candidate position 32 in vessel of interest 31 is considered as corresponding to the intravascular position at which the in-situ acquisition of intravascular hemodynamic parameter value 20 has been performed.

[0106] Thus, in the exemplary embodiment, the co-registration of the invasive FFR measurement with the non-invasively acquired volumetric reconstruction may be improved such that the vessel of interest may be uniquely identified in the volumetric reconstruction of the vasculature.

[0107] Although in above described embodiments, the diagnostic image data has been obtained using computed tomography, it shall be understood that in other embodiments, the diagnostic image data may likewise be retrieved by other imaging methods, such as position emission tomography, single positron emission computed tomography, magnetic resonance imaging, X-ray scanning or the like.

[0108] Further, it shall be understood that, although in the above embodiments the values have been determined for a single hemodynamic parameter, the method may also be performed by determining the values for more than one hemodynamic parameter in measurement and by simulation, respectively. To that end, it may be understood that the hemodynamic parameter regarded may be a hemodynamic parameter other than blood pressure, such as blood resistance or blood viscosity or the like.

[0109] Further, while in the above embodiments, the analyzing has been performed on the coronary vasculature, in other embodiments, the analysis may likewise be performed on the vasculature in other parts of the human body, such as the peripheral vasculature.

[0110] It shall be understood that, while in the above embodiments the physiological model is representative of the fluid dynamics, i.e. comprises a fluid dynamics model, the physiological model may further be representative of the geometry of the vasculature, i.e. may further comprise a geometric model of the vasculature.

[0111] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0112] In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality.

[0113] A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0114] Procedures like the segmenting of the diagnostic image data, the generating of a physiological model, the determination of the simulated hemodynamic parameter values, the comparing of the simulated and intravascular hemodynamic parameter values, the identifying of the vessel of interest, the calculation of a graphical representation, et cetera performed by one or several units or devices can be performed by any other number of units or devices. These procedures in accordance with the invention can hereby be implemented as program code means of a computer program and/or as dedicated hardware.

[0115] A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0116] Any reference signs in the claims should not be construed as limiting the scope.

[0117] The invention relates to an apparatus for analyzing a vasculature of a patient, comprising an input unit configured to receive a plurality of simulated hemodynamic parameters determined on the basis of a physiological model derived from diagnostic image data of the vasculature for a plurality of candidate vessels of the vasculature and at least one intravascular hemodynamic parameter acquired in-situ by an intravascular measurement device from a vessel of interest in the vasculature. The apparatus further comprises a comparing unit configured to compare each of the plurality of simulated hemodynamic parameters to the at least one intravascular hemodynamic parameter and to identify, based on the comparing, the vessel of interest in a reconstruction derived from the diagnostic image data.

[0118] By means of this apparatus, the ambiguity in the co-registration of the imaging modality with the intravascular measurement modality may be avoided.