Measurement Guidelines for Coronary Flow Estimation Based on Bernoulli's Principle

Abstract

A device and a corresponding method for evaluating hemodynamic properties in a coronary vasculature are provided, wherein diagnostic data of a vessel of interest are used to identify first and second measurement locations at which first and second values ​​for a first hemodynamic property can be obtained, whereby these first and second values ​​are suitable for deriving at least one diagnostic parameter indicative of a second hemodynamic property that cannot or should not be directly measured.

Description

Technical Field

[0001] The present invention relates to an apparatus for assessing hemodynamic properties in the coronary vasculature, a corresponding method and a corresponding computer program. In particular, the present invention relates to an improved measurement guidance for performing the measurement of hemodynamic parameters by deriving an optimal measurement position for the intravascular measurement from diagnostic data of the vasculature. Background Art

[0002] The severity of a functional stenosis in a coronary artery can usually be assessed by means of intravascular pressure measurements. In this respect, it is possible to assess the severity of a functional stenosis in a coronary artery by taking into account the pressure distal to the stenosis (P d ) and the pressure in the aorta (P a ). Therefore, this ratio can be taken into account using indicators such as the fractional flow reserve (FFR) or the instantaneous wave-free ratio (iFR), both of which are determined based on the pressure ratio. The FFR measurement uses the entire cardiac cycle pressure curve and must be performed in a hyperemic state, which is usually caused by the use of vasodilating agents. In contrast, the iFR measurement is performed at rest during a specific period of the cardiac cycle, namely the diastole, which is also called the wave-free period.

[0003] While pressure-based indices allow for a sufficient understanding of coronary artery lesions, additional measurements of flow properties of blood may provide additional insights, enabling a more thorough understanding of the diagnosis of the coronary vasculature and, therefore, enabling improved treatment planning for coronary artery lesions present therein. In this regard, measurements of flow velocity and / or volume flow rate through vessels of interest in the vasculature may be particularly suitable for improving the understanding of coronary artery lesions.

[0004] Another important indicator for the correct assessment of lesions in the coronary arteries is the so-called coronary flow reserve (CFR), which defines the maximum increase in blood flow through the vasculature above the normal resting volume. The CFR can be obtained by measuring the ratio between hyperemic flow and resting flow.

[0005] Despite these benefits, routine flow measurement for the purpose of assessing additional hemodynamic properties has not entered clinical practice due to increased complexity and lack of robustness of any measurement techniques that can be used to measure flow-related parameters.

[0006] EP 2633815 A1 discloses a scheme for evaluating hemodynamic properties for an organ of interest. In one implementation, a fluid dynamics model may be provided with data derived from an anatomical imaging modality and blood flow information derived by ultrasound to derive desired hemodynamic properties. In one such implementation, a blood flow reserve fraction is estimated.

[0007] WO 2017 / 021201 A1 discloses an auxiliary device, an auxiliary system and an auxiliary method for assisting a practitioner in performing interventional hemodynamic (e.g., fractional flow reserve (FFR)) measurements on a subject. FFR pressure measurement is combined with an angiography-based assessment of the coronary vessel geometry. Advanced computational fluid dynamics models can be used to add flow and myocardial resistance data based on interventional pressure values ​​and based on a vascular model generated before the intervention. If these data are available before the intervention, the location of the optimal position for pressure measurement can be calculated in advance, and by overlaying the vascular tree, for example on an X-ray projection, advice can be given to the interventional cardiologist during the intervention. Summary of the invention

[0008] Rather than directly measuring flow properties such as flow velocity and volume flow rate, these properties can be approximated from pressure measurements according to Bernoulli's principle. However, to obtain a sufficiently accurate approximation, the pressure measurements must be performed at a suitable measurement location inside a vessel of interest in the vasculature.

[0009] It is therefore an object of the present invention to provide an improved device which allows the assessment of hemodynamic properties, such as flow properties, inside a vessel of interest in the vasculature of a patient.

[0010] A further object of the invention is to provide an improved method for deriving diagnostic parameters indicative of hemodynamic properties such as flow properties from measurements of other hemodynamic properties such as pressure measurements. Even more specifically, it is an object of the invention to provide an apparatus for assessing and modeling coronary physiology based on diagnostic data of the vasculature, with which apparatus diagnostic parameters such as CFR can be determined with a high degree of accuracy.

[0011] Therefore, an apparatus for evaluating a coronary vasculature is provided, the apparatus comprising: an input unit for receiving diagnostic data of a vessel of interest in the vasculature; and an identification unit for using the diagnostic data to identify a first intravascular measurement location at which a first hemodynamic value of a first hemodynamic property is derived and a second intravascular measurement location at which a second hemodynamic value of the first hemodynamic property is derived. The apparatus further comprises: a calculation unit for calculating at least one diagnostic parameter representing a second hemodynamic property in the vessel of interest based on the first hemodynamic value and the second hemodynamic value.

[0012] Thus, the term "vessel of interest" may specifically refer to a vessel or vascular tree in the coronary vasculature of a patient. Even more specifically, the term "vessel of interest" may refer to one or more vessel segments of a vessel of interest in the vasculature of a patient. Likewise, it should be understood that the term "(first or second) hemodynamic property" may generally refer to any property representative of hemodynamics inside the vasculature of a patient. Furthermore, the term "hemodynamic value" may refer to a measured value of a hemodynamic property of the vasculature, whereby the hemodynamic value is obtained by measurement at a specific intravascular location along the longitudinal axis of the vessel of interest.

[0013] In some embodiments, the hemodynamic properties may relate to properties such as vessel wall friction, vessel wall elasticity, vessel impedance, blood viscosity, blood pressure, flow velocity, volume flow rate, volume outflow rate through a vessel bifurcation, etc. In this context, the first and second hemodynamic values ​​may be derived specifically for a first hemodynamic property, such as pressure inside a vessel of interest, and subsequently used to calculate a diagnostic parameter representative of a second hemodynamic property, such as volume flow rate. Thus, a first hemodynamic property may be used to derive a second hemodynamic property that is different from the first hemodynamic property.

[0014] The term "diagnostic data" may refer to any kind of measurement data representing the vasculature including the vessel of interest. More specifically, the diagnostic data may include diagnostic image data acquired by imaging modalities such as X-ray scanning, computed tomography (CT), X-ray angiography, positron emission tomography (PET), single photon emission computed tomography (SPECT), ultrasound imaging, etc. The diagnostic image data may thus include a single two-dimensional or three-dimensional diagnostic image or a time series of diagnostic images collected over a specific time span. The diagnostic image data may relate to perfusion data obtained using magnetic resonance imaging (MRI), CT and / or PET.

[0015] The diagnostic data may also include measurement data acquired by intravascular measurements that have been performed in situ (i.e., from inside the vessel of interest). In this regard, the diagnostic data may include intravascular image data that has been acquired using an intravascular imaging modality (such as intravascular ultrasound (IVUS) and / or optical coherence tomography (OCT)), which has been obtained by a measurement device attached to a catheter introduced into the vessel of interest. The intravascular image data may include a single intravascular image or a time series of intravascular images collected over time for the same intravascular measurement location. Additionally or alternatively, intravascular image data may also be collected by slowly pulling back the catheter through the vessel and by obtaining multiple intravascular images at multiple intravascular measurement locations.

[0016] The diagnostic data may also include intravascular measurement data acquired during the intravascular measurement. The intravascular measurement data may specifically refer to pullback data. The term "pullback data" generally relates to a plurality of hemodynamic values ​​determined at a plurality of intravascular positions along the longitudinal axis of the vessel of interest. The pullback data is obtained for a specific pullback length, which is defined as the distance between the determined starting position of the plurality of hemodynamic values ​​and the determined ending position. The pullback data may, for example, be used to determine a pressure gradient along the vessel of interest, i.e., may be used to determine a plurality of pressure values ​​for a plurality of intravascular positions, generally starting at a distal position and ending at a proximal position. In this context, the terms "proximal" and "distal" should be understood within their conventional meanings, i.e., defined as a position close to and a position far from the main part of the body, respectively. With respect to coronary vessels, when viewed along the longitudinal axis of the coronary vessels, the proximal position is a position closer to the heart, while the distal position relates to a position further away from the heart than the proximal position.

[0017] The term "measurement location" may generally refer to an intravascular location at which a hemodynamic value of a first hemodynamic property may be measured. It will be appreciated that this measurement of the first hemodynamic property may be performed as part of the acquisition of diagnostic data, for example, where the diagnostic data comprises (pressure) pullback data. Alternatively or additionally, the measurement of the first hemodynamic property may be performed in a further measurement step after identifying the first and second measurement locations using the diagnostic data.

[0018] Thus, in the first case, deriving the first and second hemodynamic values ​​at the first and second measurement locations specifically refers to determining the first and second hemodynamic values ​​measured at the identified first and second measurement locations based on the already acquired diagnostic data. In contrast, in the second case, deriving the first and second hemodynamic values ​​refers to a situation in which the first and second measurement locations are identified based on the diagnostic data, and then a (intravascular) measurement of the first hemodynamic property is performed at the first and second measurement locations to measure the first and second hemodynamic values. The details of these different scenarios will be described herein below with respect to various embodiments.

[0019] Using the diagnostic data to identify first and second measurement locations allows determining optimal measurement locations for acquiring measurement values ​​of the first hemodynamic property, whereby the values ​​acquired at these locations allow an improved approximation, ie calculation, of the second hemodynamic property.

[0020] In some embodiments, the first hemodynamic property comprises a pressure in a vessel of interest. Therefore, the hemodynamic value derived for the first hemodynamic property is an intravascular pressure value. As described above, pressure values ​​are particularly suitable for deriving additional hemodynamic properties, such as flow properties. More specifically, blood flow properties can be derived from the measured pressure values ​​according to the Bernoulli principle.

[0021] Bernoulli's principle relates pressure to flow velocity in particular, and is defined as the simultaneous increase in flow velocity and decrease in pressure of an incompressible fluid (such as human or animal blood). If friction losses and changes in the potential energy of the fluid are neglected, the local change in flow velocity v between a first measurement location (1) and a second measurement location (2) is defined as the change in pressure p between these locations:

[0022]

[0023] where ρ is the density of the fluid.

[0024] Furthermore, the volume flow rate Q in the vessel of interest can generally be determined as:

[0025] Q=vA,

[0026] Where A is the cross-sectional (vessel) area at a specific location of the vessel of interest (i.e., in a specific vessel segment), and v is the flow velocity through the vessel of interest. In the case of lesions and / or stenosis in the vessel, the cross-sectional area A changes. If it is assumed that the volume flow rate Q is constant along the length of the vessel segment to be considered due to the absence of bifurcations through which outflow from the vessel of interest may occur in the respective vessel segment, a change in the cross-sectional area A results in a change in the local flow velocity along the vessel segment considered. Therefore, at the first measurement location (1) and the second measurement location (2) in the vessel segment, the volume flow rate Q can be assumed to be equal to:

[0027] Q=v1A1=v2A2.

[0028] Thus, by measuring the pressure difference Δp=p1-p2 between the first measuring position (1) and the second measuring position (2) and determining the local cross-sectional areas A1 and A2, the volume flow rate can be calculated using a calculation according to the following formula:

[0029]

[0030] Therefore, a flow ratio similar to the coronary flow reserve (CFR) can be derived according to the following formula, which corresponds to the flow ratio in hyperemia (Q H ) and rest (Q R ) conditions.

[0031]

[0032] It will be appreciated that in this case, pressure values ​​have to be obtained at the first and second measuring positions for both the hyperemic state and the resting state, respectively.

[0033] Thus, flow-related hemodynamic properties can potentially be derived from pressure measurements performed at at least two measurement locations. However, in order to derive accurate parameters for flow-related hemodynamic properties, it may not be possible to perform pressure measurements at two arbitrary locations. Instead, it must be ensured that the flow velocity and therefore the pressure values ​​at the first and second measurement locations differ significantly from each other, so that the pressure difference Δp=p1-p2 can be adequately measured, even in the case of limited accuracy of the pressure probe used to measure the pressure values.

[0034] In this regard, in some embodiments, identifying a first intravascular measurement location and a second intravascular measurement location includes: predicting a local change in a second hemodynamic property in a vessel of interest at at least one candidate location, identifying the at least one candidate location as a first intravascular measurement location, and identifying an intravascular location other than the at least one candidate location as a second intravascular measurement location.

[0035] As noted herein above, flow properties can be derived from pressure values ​​obtained at first and second measurement locations where the pressures show significant differences. Although these first and second measurement locations can typically be found in a specific vessel or segment of a specific vessel, their identification is not straightforward. Therefore, in some embodiments, the first and second measurement locations are identified based on diagnostic data.

[0036] This can be achieved in particular by predicting a local change of a second hemodynamic property based on the diagnostic data. In some embodiments, the second hemodynamic property can be particularly related to flow velocity, and the diagnostic data can be used to predict an increase or decrease in the local flow velocity at a specific location along the longitudinal axis in the vessel of interest.

[0037] Depending on the kind of diagnostic data used, the prediction can be performed in various ways. In case diagnostic image data and / or intravascular image data are obtained by means of the respective imaging modality, the prediction can in particular be performed by detecting in the image data local changes in the cross-sectional area of ​​the vessel of interest, the local changes being for example due to lesions and / or stenosis in the vessel of interest. As previously mentioned, since the volume flow rate in the entire vessel should be constant, changes in the cross-sectional area of ​​the vessel indicate changes in the flow velocity when any outflow from the vessel is not taken into account, since the same volume of blood has to pass through different cross-sectional areas. Therefore, based on the image data, it can be predicted that at the location of the lesion and / or stenosis, the flow velocity as the second hemodynamic property will show a local change, i.e. an increase or decrease in value.

[0038] In case the pullback data comprises a plurality of hemodynamic values ​​for a first hemodynamic property, said hemodynamic values ​​may be used to predict changes in the values ​​of said second hemodynamic property. As previously mentioned, different hemodynamic properties are related to each other according to the laws of fluid dynamics. Thus, at least one diagnostic parameter indicative of a second hemodynamic property can be derived from the pullback data providing a plurality of values ​​for the first hemodynamic property.

[0039] In some embodiments, the pullback data may specifically include a plurality of pressure values ​​acquired at a plurality of positions along the longitudinal axis of the vessel of interest, starting at a distal position and ending at a proximal position. Thus, the first hemodynamic property may be related to the pressure inside the vessel of interest. In this case, the second hemodynamic property may specifically be flow rate. As noted above in this document, pressure and flow rate are related via Bernoulli's theorem, and therefore, changes in local flow rate will also result in changes in pressure. Therefore, by considering a pressure pullback curve comprising a plurality of pressure values, local pressure changes, in particular local pressure reductions, may be identified. At the location of such a local pressure change, changes in flow rate may be predicted.

[0040] Thus, in both cases, the image data as well as the pullback data can be predicted and ultimately the flow velocity changes at a specific location can be predicted.

[0041] The location of the change in flow velocity can then be identified as a candidate location for the first measurement location, i.e., a location at which a first hemodynamic value significantly differs from a second hemodynamic value measured at the second measurement location can be determined. In order to ensure such a difference, the second measurement location is usually identified as a further intravascular location that is assumed to be unaffected by the stenosis and / or lesion. Thus, the further intravascular location should be far enough from the stenosis and / or lesion that turbulence caused by the stenosis and / or lesion does not remain, while at the same time not being so far from the stenosis and / or lesion that side effects such as friction losses and outflow to small vessels become too significant to be ignored in the approximation.

[0042] Thus, the additional intravascular position may be considered as an additional position inside the vessel where the measurement of the second hemodynamic value may be performed, such that the second hemodynamic value is significantly different from the first hemodynamic value. Thus, the additional intravascular position may be located proximal or distal to the candidate position.

[0043] In some embodiments, both the first and second measurement positions may be specifically defined by a stenosis and / or a lesion, wherein the candidate position identified as the first measurement position is located at the position of the stenosis and / or the lesion, i.e. inside the stenosis and / or the lesion, and the further intravascular position designated as the second measurement position is located away therefrom along the longitudinal axis of the vessel of interest. In some embodiments, in order to qualify as a suitable second measurement position, the further intravascular position may be specifically about 0.5 to 2 cm, more specifically 1 cm, away from the candidate position identified as the first measurement position along the longitudinal axis of the vessel of interest. Even more specifically, the further intravascular position may be located 1 cm close to the stenosis and / or the lesion and thus proximal or distal to the candidate position designated as the first measurement position.

[0044] Alternatively or additionally, the identification of the second measurement position may also be performed using additional and / or different criteria. In some embodiments, a healthy-looking vessel segment of the vessel of interest may be identified using the respective diagnostic image data and / or intravascular image data. In this context, the term "healthy" specifically refers to a vessel segment that does not exhibit any stenosis and / or lesions. The additional intravascular measurement position may be located in this healthy-looking vessel segment and, because of being located there, is identified as the second measurement position.

[0045] In some embodiments where the diagnostic data includes pullback data, a pullback curve derived from the pullback data may be considered. If the pullback curve exhibits a constituent slope along a plurality of intravascular locations, it may be assumed that this indicates a healthy vessel segment. The intravascular location located in the vessel segment may then be identified as a second measurement location.

[0046] Alternatively and / or additionally, identification of the second measurement location may be performed based at least in part on the presence and / or absence of a bifurcation between the candidate location and the additional intravascular location. More specifically, if there is no bifurcation between the candidate location identified as the first measurement location and itself, the additional intravascular location may be identified as the second measurement location, and if there is a bifurcation between the candidate location and the additional intravascular measurement location, the additional intravascular location may not be identified as the second measurement location.

[0047] By identifying the first and second measurement locations in this way, it can be ensured that the first and second hemodynamic values ​​obtained at these locations are significantly different from each other. More specifically, choosing the first and second measurement locations in this way can allow approximating a diagnostic parameter indicative of the second hemodynamic property, regardless of the possible measurement accuracy.

[0048] In some embodiments, the diagnostic data includes at least one diagnostic image of the vessel of interest. Thus, identifying the first intravascular measurement location and the second intravascular measurement location includes segmenting the vessel of interest into a plurality of segments, deriving a plurality of geometric parameter values ​​of the vessel of interest at a plurality of intravascular locations along the longitudinal axis of the vessel of interest for each of the segments; identifying at least one geometric parameter value from the plurality of geometric parameter values ​​at the plurality of intravascular locations, the at least one geometric parameter value indicating stenosis of the vessel of interest at at least one candidate location from the plurality of intravascular locations; wherein the at least one candidate location of the stenosis is identified as the first intravascular measurement location, and another intravascular location other than the at least one candidate location is identified as the second intravascular measurement location.

[0049] In some embodiments, the identification of the first and second measurement locations may be performed using at least one diagnostic image of a vascular system including a vessel of interest that has been acquired by a respective imaging modality, such as X-ray scanning, computed tomography (CT), X-ray angiography, positron emission tomography (PET), single photon emission computed tomography (SPECT), ultrasound imaging, etc. In some particular embodiments, the at least one diagnostic image may specifically represent a single two-dimensional X-ray angiography image.

[0050] According to these embodiments, firstly a first and a second measurement location are identified by taking into account the at least one diagnostic image. Subsequently, a measurement of a hemodynamic value, such as a pressure value, is performed at the first and second measurement locations thus identified.

[0051] For this purpose, the vessel of interest imaged in the at least one diagnostic image is segmented into a plurality of segments. It should be understood that segmenting the vessel of interest corresponds to segmenting the vessel of interest represented in the diagnostic image into respective vessel segments.

[0052] For each of the segments, a plurality of geometric parameter values ​​for the vessel of interest may be derived at a plurality of intravascular locations. In this context, the term "geometric parameter" may refer to any parameter representing the geometry of the vessel of interest. In some embodiments, the geometric parameter may specifically refer to the cross-sectional area of ​​the vessel of interest. In some embodiments, the geometric parameter may also refer to the internal shape of the vessel or a similar geometric measurement. Thus, a value for at least one geometric parameter, such as a value for the cross-sectional area, may be determined for a plurality of intravascular locations along the longitudinal axis of the vessel of interest. Thus, the plurality of geometric parameter values ​​refer to values ​​determined for each intravascular location, respectively, along the longitudinal axis of the vessel of interest.

[0053] In some embodiments, the geometric parameter values ​​are used to identify lesions and / or stenosis of a vessel of interest at at least one intravascular location. The intravascular location where the lesion and / or stenosis has been identified is then designated as a candidate location, i.e., a potential candidate for the first measurement location. If lesions and / or stenosis have been identified at multiple intravascular locations, one of these intravascular locations can be selected as a candidate location. More specifically, multiple values ​​of geometric parameters indicating the geometry of a vessel are focused on, and changes in the values ​​are determined, which indicate lesions and / or stenosis of the vessel of interest. In a specific embodiment, the cross-sectional area is considered a geometric parameter, and changes in the cross-sectional area are considered to indicate lesions and / or stenosis.

[0054] As previously mentioned, at such locations where the cross-sectional area changes, the local flow velocity may vary significantly if a constant volume flow rate is assumed. Therefore, the intravascular location of the lesion and / or stenosis identified from at least one diagnostic image may be considered as a possible candidate for the first measurement location. Subsequently, an additional intravascular location located proximal or distal to the candidate location thus identified may be considered and designated as a second measurement location. In a next step, the derivation of first and second hemodynamic values ​​of the first hemodynamic property is performed by measuring the respective first hemodynamic property at the first and second measurement locations and obtaining the respective first and second values.

[0055] In some embodiments, the device further comprises: a modeling unit for generating a physiological model of the blood vessel of interest based on at least one diagnostic image, the physiological model comprising a fluid dynamics model; wherein at least one diagnostic parameter representing a second hemodynamic property is calculated based on the fluid dynamics model.

[0056] In some embodiments, a physiological model including a fluid dynamics model is used to calculate the diagnostic parameters. Thereby, the physiological model can be obtained from at least one diagnostic image of the vessel of interest. In some embodiments, the physiological model can be obtained in particular from a single diagnostic image of the vessel of interest. The diagnostic image can thereby be used by the modeling unit to generate the physiological model from the diagnostic image. The generation of the physiological model can in particular include a segmentation of the imaged vessel of interest. For the purpose of generating the physiological model, the segmentation can be performed by the modeling unit. Alternatively, a vessel segmentation performed by the recognition unit for identifying the first and second measurement positions can be used.

[0057] Based on the segmentation, a physiological model representing one or more vessel segments of the vessel of interest can be generated. To this end, the physiological model can include a fluid dynamics model to simulate the fluid dynamics of the various segments of the vessel of interest, especially the fluid dynamics of the blood. To this end, the fluid dynamics model can be generated by performing calculations that simulate the interaction of blood with the vessel wall (i.e., the inner surface of the vessel through which the blood flows). These interactions can be defined by respective boundary conditions that take into account specific hemodynamic properties of the vessel, such as vessel wall composition, vessel wall elasticity and vessel impedance, bifurcations in the vessel, and blood viscosity. For this purpose, general boundary conditions that are similar for all patients or for a specific group of patients (differentiated by age, sex, physiological condition, etc.) can be used. Alternatively or additionally, patient-specific boundary conditions that have been derived for a specific patient can be used for the calculation of the fluid dynamics model.

[0058] In an embodiment, the fluid dynamics model may specifically refer to a lumped parameter model. In such a lumped parameter model, the fluid dynamics of the blood vessel is approximated by the topology of discrete entities. More specifically, in the lumped parameter model, the blood vessel impedance is approximated by a series of resistor elements, and the terminals of the blood vessels are represented by elements representing grounding. Therefore, the blood vessel tree can be represented by a topology of resistors each having a specific resistance, where the representation of the blood vessel tree is terminated by respective grounding elements. Compared with other schemes such as Navier-Stokes, these lumped parameter models reduce the dimensionality. Therefore, the use of lumped parameter models can allow simplified calculation of the fluid dynamics inside the blood vessel, and ultimately can reduce the processing time.

[0059] In addition or in lieu of the fluid dynamics model, the physiological model may also include a geometric model representing the geometry of the vessel of interest. The geometric model may thus be a two-dimensional (2D) or three-dimensional (3D) geometric representation of the vessel of interest or a segment thereof. In a particular embodiment of the invention, the geometric model may be a 2D model derived from 2D angiographic image data for which the third dimension is approximated by assuming a circular shape of the vessel.

[0060] In some embodiments, the geometrical model and the fluid dynamics model included in the physiological model can be used to simulate the geometrical structure and the fluid dynamics through each blood vessel (segment), respectively. Accordingly, the calculation of the diagnostic parameter representing the second hemodynamic property is performed using the fluid dynamics model by simulating the second hemodynamic parameter in the blood vessel of interest based on respective boundary conditions derived, for example, from the diagnostic data and / or the first and second hemodynamic values.

[0061] In some embodiments, identifying the first intravascular measurement location and the second intravascular measurement location also includes: determining the location of a bifurcation in the vessel of interest based on the diagnostic image; and when the bifurcation is determined to be located at a position close to another intravascular location along the longitudinal axis of the vessel of interest, excluding the other intravascular location.

[0062] The above scheme for calculating the diagnostic parameters uses the following approximation: In the segment including the first and second measurement positions, no outflow of blood from the vessel of interest occurs. In practice, the lesion and / or stenosis may be located in the vicinity of a bifurcation, i.e. a branch may be identified proximal and / or distal to the lesion and / or stenosis. Through such a bifurcation, part of the blood may outflow to (and inflow from) small vessels, thereby resulting in a non-constant volume flow rate between the first measurement position and one or more intravascular positions that may be selected as the second measurement position.

[0063] In this case, the selection must include excluding such intravascular locations in order to still obtain an accurate approximation of the second hemodynamic property. In other words: the first and second measurement locations should be selected such that no outflow to small vessels occurs between the first and second measurement locations. In this context, it should be understood that the requirement that no outflow occurs should also be understood to also include the situation in which small vessels (and corresponding bifurcations) are small enough to be negligible from the point of view of accuracy. Furthermore, the term "approximately" may in particular refer to a bifurcation being located at a location between a candidate location selected as the first measurement location and a further intravascular location considered as a potential second measurement location.

[0064] To achieve this object, in some embodiments, the at least one diagnostic image is used to identify a vessel bifurcation along the vessel or vessel segment considered for evaluation. If the bifurcation is directly visible in the diagnostic image, the bifurcation can be identified in particular by deriving the bifurcation directly from the diagnostic image manually or by image processing.

[0065] Alternatively or additionally, as described above, bifurcations may also be identified based on one or more geometrical parameters that have been determined from the diagnostic images for each vessel of interest. Specifically, the identification may be performed by considering geometrical parameter values ​​for a plurality of intravascular locations in each vessel (segment) to detect local changes (i.e., increases or decreases) in the geometrical parameter values, which may be considered as an indication for a vessel bifurcation. In some embodiments, the geometrical parameter values ​​may be derived specifically using an estimation based on a geometrical model included in the physiological model.

[0066] Thus, once a bifurcation has been identified between a candidate location designated as a first measurement location and at least one further intravascular location other than the candidate location, the at least one intravascular location may be excluded as a potential second measurement location. That is, because the bifurcation is proximal to a particular intravascular location, the intravascular location is found to be unsuitable as a second measurement location, and a different second measurement location may be identified. If no suitable second measurement location is found, the apparatus may then attempt to identify a different first measurement location. Alternatively or additionally, outflow correction may be performed to correct for approximations of outflow through the bifurcation.

[0067] Therefore, in some embodiments, identifying the first intravascular measurement location and the second intravascular measurement location also includes: determining the location of a bifurcation in the vessel of interest close to another intravascular location based on the diagnostic image; and calculating at least one diagnostic parameter based on the fluid dynamics model includes: correcting the at least one diagnostic parameter by using the fluid dynamics model to simulate outflow through the bifurcation.

[0068] In some embodiments, in case a bifurcation exists between the first and second measurement locations, no exclusion of the second measurement location is performed. Instead, a scheme is followed in which the calculation of the second hemodynamic property is corrected in order to account for outflow through the bifurcation.

[0069] As indicated herein above, in the case of a vessel bifurcation between the first and second measuring position, the volume flow rate Q is not constant for these two positions. Instead, the volume flow rate Q2 at the second measuring position differs from the volume flow rate Q1 at the first measuring position by the local outflow rate ΔQ:

[0070] Q2=Q1-ΔQ.

[0071] The local outflow rate ΔQ can be specifically modeled using a fluid dynamics model included in the physiological model. More specifically, the size and location of the bifurcations can be used as additional boundary conditions in the fluid dynamics model to simulate the outflow rate from each bifurcation.

[0072] In some embodiments, Murray's law can be used to determine the outflow through each bifurcation. According to Murray's law, the following relationship holds:

[0073] Q=k*D 3 .

[0074] Thus, Q corresponds to the volume flow rate, D is the vessel diameter, and k is a proportionality constant. It should be understood that although in the exemplary embodiment, Murray's law is used to determine the volume flow rate Q, other correlations Q(D) may also be used to describe the relationship between the volume flow rate and the vessel diameter, particularly for other parts of the vascular system.

[0075] As mentioned before, the outflow rate can be expressed by the difference between the volume flow rate at the first measurement location where the bifurcation is located and the volume flow rate at the second measurement location:

[0076] ΔQ=Q1-Q2

[0077] Therefore, by estimating the proportionality constant in the vessel and modeling the vessel diameters D1, D2 at the first and second measurement locations based on the diagnostic image data, the physiological model including the fluid dynamics model can model the local outflow rate using Murray's law. This allows the volume flow rate at the first and second measurement locations to be determined using Murray's law:

[0078]

[0079] The local outflow rate ΔQ can be modeled as the difference between the values ​​Q1 , Q2 determined thereby.

[0080] In some embodiments, wherein the fluid dynamics model may be a lumped parameter model, the outflow through the bifurcation may be estimated by means of respective resistor elements whose outlet impedance depends on the size of the bifurcation derived from the diagnostic image.

[0081] In some further embodiments, calculating at least one diagnostic parameter based on the fluid dynamics model includes correcting the at least one diagnostic parameter by simulating vascular friction between the first intravascular measurement location and the second intravascular measurement location using the fluid dynamics model.

[0082] In some embodiments, the pressure loss between the first and second measurement locations due to friction may be taken into account in the calculation of the second hemodynamic property. This may be performed in particular when the pressure loss due to friction is too large to be ignored in accurately approximating the diagnostic parameter representing the second hemodynamic property. In this case, the relationship between the pressure values ​​at the first and second measurement locations becomes:

[0083]

[0084] Among them, Δp F Corresponds to the pressure loss due to friction.

[0085] Therefore, the pressure loss Δp must be estimated F In particular, this may be performed by including respective boundary conditions in a fluid dynamics model simulating the pressure losses along the vessel of interest, including the pressure losses between the first and second measurement locations. In some embodiments, friction may be simulated by means of respective resistor elements in case the fluid dynamics model is implemented as a lumped parameter model. In some embodiments, a finite element method may alternatively be used.

[0086] In some embodiments, the diagnostic data includes intravascular pullback data, the intravascular pullback data including a plurality of hemodynamic values ​​of a first hemodynamic property acquired in situ by means of pullback recordings at a plurality of intravascular locations along a longitudinal axis of the vessel of interest. In addition, identifying the first intravascular measurement location and the second intravascular measurement location includes: from the plurality of hemodynamic values ​​acquired at the plurality of intravascular locations, identifying at least one hemodynamic value that exhibits a local variation at at least one candidate location from the plurality of intravascular locations; wherein the at least one candidate location is identified as the first intravascular measurement location, and an additional intravascular location other than the at least one candidate location is identified as the second intravascular measurement location.

[0087] In some embodiments, the diagnostic data may include pullback data that has been obtained in situ from the vessel of interest. In some embodiments, the pullback data may specifically refer to pressure pullback data. As previously described, the pullback data is acquired by pulling a measuring line through the vessel of interest to a specific pullback length and acquiring multiple measurement values ​​for multiple intravascular locations along the pullback length. In the case of acquiring pressure pullback data, the measuring device used may typically be a wire including a pressure probe. The pressure probe is then used to collect multiple pressure values ​​at multiple intravascular locations, thereby generating respective pressure pullback curves, i.e., curves representing pressure values ​​according to intravascular locations.

[0088] The pressure curve thus obtained can show local changes, that is, local increases or decreases in the pressure values ​​at one or more specific intravascular positions. As previously indicated herein, according to Bernoulli's principle, changes in pressure (values) also indicate changes in flow rate. More specifically, a decrease in pressure values ​​leads to an increase in flow rate, and vice versa. Accordingly, the local changes in the pressure values ​​indicate suitable candidate positions for the first measurement position. Therefore, each intravascular position where a local change is detected can be used as a candidate position for the first measurement position. Subsequently, another intravascular measurement position at the proximal or distal end of the candidate position (i.e., the first measurement position) is identified as a second measurement position.

[0089] Using the pressure pullback data to identify the first and second measurement locations avoids the necessity to perform two measurements, one for identifying the measurement locations and one for deriving the first and second hemodynamic values. Rather, in this approach, the derivation of the first and second hemodynamic values ​​can be performed directly on the already acquired pullback curves by selecting respective values ​​of said curves for the first and second measurement locations.

[0090] It should be understood that this approach does not allow the cross-sectional area of ​​the vessel to be derived. Therefore, it may not be possible to determine the volume flow rate based solely on the pullback data. However, since coronary flow reserve (CFR) is a clinically relevant metric, it can be approximated without knowing the volume flow rate according to the following formula:

[0091]

[0092] CFR as a diagnostic parameter indicative of flow can still be obtained directly from the pressure pullback data.Thus, this embodiment may represent a simple approach for determining clinically relevant diagnostic parameters that does not require knowledge of the vessel geometry to be determined.

[0093] In one or more additional embodiments, the diagnostic data further comprises at least one diagnostic image of the vessel of interest. In addition, identifying the first intravascular measurement location and the second intravascular measurement location further comprises: co-registering the at least one diagnostic image with the intravascular pressure data; and indicating the first intravascular measurement location and the second intravascular measurement location in the at least one diagnostic image.

[0094] In some embodiments, the pressure pullback data may also be used to obtain diagnostic parameters that require the determination of geometric parameters, such as cross-sectional area. For this purpose, the diagnostic data may also include at least one diagnostic image. The diagnostic image and the pullback data may be co-registered. Co-registering the diagnostic image and the pullback data refers to the process of determining, for each or some intravascular locations of the pullback data, a corresponding vessel location in the diagnostic image of the vessel of interest. Thus, the two measurement modalities are related to each other.

[0095] Such co-registration allows determining vessel locations in the diagnostic image corresponding to the first and second measurement locations identified from the pullback data. These vessel locations may then be indicated in the diagnostic image.

[0096] In this regard, the term "indication" may have a reference to a process inside the device, wherein the device is provided with information which position in the imaged vessel corresponds to the first and second measurement positions. Based on the indication, the device may then perform a plurality of image processing steps, etc., to obtain information about the vessel geometry and, therefore, about the volume flow rate. In some embodiments, the device may derive the cross-sectional area at the first and second measurement positions, in particular from the diagnostic image. In this regard, the device may employ a modeling unit to generate a physiological model for the vessel segment comprising the first and second measurement positions. The physiological model may comprise a fluid dynamics model and / or a geometric model. The device may use the geometric model to derive values ​​of geometric parameters, such as the cross-sectional area, at least at the first and second measurement positions.

[0097] Furthermore, the apparatus may use the indication to generate a graphical representation of the imaged blood vessel comprising a first and / or second indicator (such as an arrow or a circle) that highlights the first and second measurement locations in the diagnostic image. The apparatus may then cause the display unit to display such a graphical representation. This may allow a user (particularly a physician) to visually confirm an appropriate selection of the first and second measurement locations.

[0098] In this context, it should be understood that the case where the diagnostic image is used to generate a graphical representation of the vessel of interest is not limited to the case where the diagnostic data comprises pullback data. Similarly, in the case where the diagnostic data comprises image data, the device is able to generate a graphical representation of the imaged vessel. In this case, upon identification of the first and second measurement positions, the device may directly use this identification to insert the respective indicator into the graphical representation and provide the graphical representation thus generated to the respective display unit. The display unit may in particular comprise a computer screen, an LCD display or the like.

[0099] In some embodiments, calculating at least one diagnostic parameter comprises determining a coronary flow reserve and / or a volumetric flow rate and / or a flow velocity of blood flow in the vessel of interest.

[0100] The first and second hemodynamic values ​​obtained at the first and second measurement positions can in particular be used to calculate a diagnostic parameter representing the coronary flow reserve (CFR), the volume flow rate Q, the flow velocity v or similar hemodynamic properties. In this context, the calculation can be performed particularly well in case the first hemodynamic property measured at the first and second measurement positions is related to the pressure inside the vessel of interest. As described above in this article, the pressure value allows to calculate the flow-related properties according to the respective fluid dynamics laws (such as Bernoulli's law, Murray's law, etc.).

[0101] According to a further aspect, a method for evaluating a coronary vasculature is provided. The method comprises the steps of: receiving diagnostic data of a vessel of interest in the vasculature for identifying a first intravascular measurement location and a second intravascular measurement location using the diagnostic data, wherein a first hemodynamic value of a first hemodynamic property is derived at the first intravascular measurement location and a second hemodynamic value of the first hemodynamic property is derived at the second intravascular measurement location; and calculating at least one diagnostic parameter representing the second hemodynamic property in the vessel of interest based on the first hemodynamic value and the second hemodynamic value.

[0102] In some embodiments, the method may further include identifying the first intravascular measurement location and the second intravascular measurement location including indicating the first and second intravascular measurement locations to a user.

[0103] In some embodiments, the method further comprises a step wherein the identified first and second measurement positions are presented to the user by means of respective indications. The indication may in particular be associated to a visual indication by means of a graphical representation of the vessel of interest and respective indicators for the first and second measurement positions. Alternatively or additionally, the indication may also be audible or visual in the sense that the position relative to the longitudinal axis of the vessel of interest is indicated in verbal or written form.

[0104] In response to the indication, the user can then position the intravascular measurement device accordingly so as to obtain a first hemodynamic value at a first measurement position and a second hemodynamic value at a second measurement position. That is, the user introduces the intravascular measurement device into the vessel of interest and adjusts the position so that the measurement probe (such as a pressure probe in the case of a pressure measurement) is located at the first measurement position and then at the second measurement position. It should be understood that the intravascular measurement device can similarly be first positioned at the second measurement position and then moved to the first measurement position.

[0105] The instructions to the user may also include other instructions. In some embodiments, these instructions may specifically relate to additional information of the vessel of interest and / or the procedure performed to evaluate it. In this regard, the instructions may include: providing information about the diagnostic measurement modality used to obtain the diagnostic data, providing information about the patient's health status and / or comorbidities, etc. In some embodiments, the instructions may specifically include an indication that the first and / or second measurement position could not be identified for a specific vessel (segment) of interest.

[0106] In a further aspect, a computer program for controlling an apparatus according to any of the above embodiments is provided, the computer program being adapted to perform a method according to one or more of its embodiments when run by a processing unit. In yet another aspect, a computer readable medium having the computer program stored thereon is provided.

[0107] It shall be understood that the apparatus according to claim 1, the method according to claim 12, the computer program according to claim 14 and the computer readable medium according to claim 15 have similar and / or identical preferred embodiments, in particular as defined in the dependent claims.

[0108] It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or the above embodiments with the respective independent claim.

[0109] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0110] In the following figures:

[0111] Figure 1 schematically illustrates an apparatus for assessing the coronary vasculature according to a first exemplary embodiment;

[0112] Figure 2 a flow chart showing a method for assessing the coronary vasculature according to a first exemplary embodiment;

[0113] Figure 3 schematically illustrates an apparatus for assessing the coronary vasculature according to a second exemplary embodiment; and

[0114] Figure 4 A flow chart showing a method for assessing the coronary vasculature according to a second exemplary embodiment. DETAILED DESCRIPTION

[0115] The illustrations in the drawings are schematic. In different drawings, similar or identical elements are provided with the same reference signs.

[0116] Figure 1 An exemplary embodiment of an apparatus 1 for assessing hemodynamic properties is schematically represented. The apparatus 1 comprises an input unit 100, a recognition unit 200, a calculation unit 300, a modeling unit 400 and a display unit 500.

[0117] The input unit 100 receives a diagnostic image 10 of a blood vessel of interest. Figure 1 In the exemplary embodiment of FIG. 1 , the diagnostic image 10 is a two-dimensional image acquired using X-ray angiography. The input unit 100 provides the diagnostic image 10 to the recognition unit 200 .

[0118] The recognition unit 200 is configured to receive the diagnostic image 10 and to perform a vessel segmentation of the vessel of interest represented in the diagnostic image 10, i.e., the recognition unit 200 segments the (image of) the vessel of interest into a plurality of segments along the longitudinal axis of the vessel of interest. The recognition unit 200 considers these segments and derives the value of one or more geometric parameters for each intravascular position in each vessel segment. Figure 1 In an exemplary embodiment of , one geometric parameter derived by the identification unit 200 is the cross-sectional area of ​​the vessel. The identification unit 200 thus derives a corresponding cross-sectional area of ​​the vessel for each intravascular position in the respective vessel segment.

[0119] Based on the cross-sectional area, the identification unit 200 can then determine the location within the blood vessel where the change in cross-sectional area is observed. Figure 1 In an exemplary embodiment of the present invention, the recognition unit specifically determines the intravascular position where the vascular stenosis is located. For this purpose, the recognition unit 200 can compare the cross-sectional areas determined for each intravascular position in each segment, and determine where the cross-sectional area at a specific intravascular position in a specific segment is smaller than the remaining intravascular positions. Then, the intravascular position exhibiting the smaller cross-sectional area is designated as a candidate for the first measurement position. Subsequently, the candidate position is designated as the first measurement position.

[0120] Then, the recognition unit 200 pays attention to another intravascular position other than the candidate position designated as the first measurement position, and recognizes the other intravascular position as the second measurement position. Figure 1 In an exemplary embodiment of , the additional intravascular position corresponds to a position about 1 cm from the candidate position when viewed along the longitudinal axis of the vessel of interest. Then, the recognition unit 200 provides information about the first and second measurement positions to the input unit 100.

[0121] In response to receiving the information about the first and second measurement locations identified by the identification unit 200, the input unit 100 is configured to receive hemodynamic measurement data 20 representing the first hemodynamic property. The hemodynamic measurement data 20 therefore includes a first hemodynamic value of the first hemodynamic property measured at the first measurement location and a second hemodynamic value of the first hemodynamic property measured at the second measurement location.

[0122] The input unit 100 can specifically receive the hemodynamic measurement data 20 including the first and second hemodynamic values ​​in the following manner: obtaining the first and second hemodynamic values ​​at the first and second measurement positions by means of in situ measurement to provide instructions to an intravascular measurement device installed for obtaining hemodynamic measurement data; or, for example, indicating the first and second measurement positions to the user via a graphical user interface, so that the user can perform respective measurements at the indicated first and second measurement positions.

[0123] In accordance with Figure 1 In the exemplary embodiment of , the hemodynamic measurement data 20 correspond to pressure measurements taken when the patient is at rest. Thus, the first and second hemodynamic values ​​taken at the first and second measurement locations correspond to a first pressure value p1 and a second pressure value p2.

[0124] When the input unit 100 receives the first pressure value p1 and the second pressure value p2, the input unit 100 is configured to provide the pressure values ​​p1, p2 to the calculation unit 300. The calculation unit 300 is configured to calculate at least one diagnostic parameter indicating the hemodynamic properties of the blood vessel of interest according to the pressure values.

[0125] In accordance with Figure 1 In an exemplary embodiment of the present invention, the calculation unit 300 specifically calculates the volume flow rate through each segment of the blood vessel of interest, and outputs information about the calculated volume flow rate and information about the measurement location, and optionally, outputs additional information about the pressure value used for the calculation to the modeling unit 400.

[0126] Furthermore, the modeling unit 400 is configured to receive from the recognition unit 200 an indication that there is a bifurcation between the first and second measurement positions indicated by the input unit 100. To this end, the recognition unit 200 is specifically configured to detect the presence of such a bifurcation by a respective image processing algorithm based on the diagnostic image 10. In some embodiments, the detection may also be performed based on at least one geometric parameter value derived for a blood vessel (segment).

[0127] The modeling unit 400 receives the calculated volume flow rate from the calculation unit 300. This approximated volume flow rate does not yet take into account the bifurcation that exists between the two measurement locations. Therefore, the approximated flow rate does not take into account the outflow rate from the vessel of interest between the measurement locations.

[0128] The modeling unit 400 also receives the diagnostic image 10 and / or the segmentation of the vessel of interest via the identification unit 200. Furthermore, the modeling unit 400 receives information about the identified bifurcations.

[0129] Depending on the received information, the modeling unit 400 then segments the vessel of interest in the diagnostic image, or generates a physiological model of the vessel of interest, which includes a fluid dynamics model representing the fluid dynamics through the vessel of interest (or its segment), using the vessel segmentation received from the recognition unit 200. Optionally, the modeling unit 400 also includes a geometric model of the geometric structure of the vessel of interest into the physiological model.

[0130] Using the fluid dynamics model included in the physiological model, the modeling unit 400 models the outflow through the bifurcation indicated by the identification unit 200 and the pressure loss due to friction between the first and second measurement locations and corrects the calculated volume blood flow accordingly.

[0131] The modeling unit 400 then provides the corrected volume flow rate to the calculation unit 300, which can use the corrected volume flow rate to calculate at least one diagnostic parameter representing it. In this regard, the diagnostic parameter can specifically correspond to the value of the volumetric flow at a specific location inside the blood vessel. Alternatively, the calculated diagnostic parameter can involve an indicator derived from the volume flow rate.

[0132] The computing unit 300 then provides the diagnostic parameters and optionally the diagnostic image 10 to the display unit 500. The display unit 500 generates a graphical representation of at least one diagnostic parameter based on the information provided by the computing unit 300. Optionally, the display unit 500 may also generate a graphical representation of the diagnostic image and display the graphical representation together with the graphical representation of the diagnostic parameter. In some embodiments, the diagnostic parameter may in particular be displayed as part of the graphical representation of the image, specifically placed at a position in the image corresponding to the intravascular position for which the diagnostic parameter was derived. The graphical representation may then be provided to the user for further information, for example, regarding the hemodynamic value for the first hemodynamic attribute and / or the diagnostic parameter indicating the second hemodynamic attribute.

[0133] Figure 2 The diagram shows that the Figure 1 A flowchart of a method executed by an apparatus of the first embodiment.

[0134] In step S101 , the input unit 100 receives a diagnostic image 10 of a blood vessel of interest and provides the diagnostic image 10 to the recognition unit 200 .

[0135] In step S201, the recognition unit 200 receives the diagnostic image 10 and in step S202 performs vessel segmentation of the vessels of interest represented in the diagnostic image 10. In step S203, the recognition unit 200 derives values ​​of one or more geometric parameters for each intravascular position in each vessel segment, which values ​​correspond to the cross-sectional area of ​​the vessel in this particular embodiment.

[0136] In step S204, the identification unit 200 compares the cross-sectional areas determined for each intravascular position in each segment with each other, and determines an intravascular position whose cross-sectional area is significantly different from the remaining cross-sectional areas at the remaining intravascular positions. Figure 2 In an exemplary embodiment of the invention, the identification unit specifically determines at least one intravascular location at which the cross-section shows a local reduction.

[0137] In step S205, the intravascular position where the local reduction in cross-sectional area is determined is designated as the first measurement position. In addition, another intravascular position other than the first measurement position is identified as the second measurement position. Then, in step S206, the identification unit 200 provides information about the first and second measurement positions to the input unit 100, and provides the geometric parameters derived at the first and second measurement positions to the calculation unit 300.

[0138] Furthermore, in step S207 , the recognition unit 200 determines whether there is a bifurcation between the first and second measurement positions and provides this information together with the diagnostic image and optional segmentation to the modeling unit 400 .

[0139] In step S102, the input unit 100 receives the hemodynamic measurement data 20 in response to receiving the information about the first and second measurement positions, the hemodynamic measurement data 20 including a first hemodynamic value of a first hemodynamic property measured at the first measurement position and a second hemodynamic value of the first hemodynamic property measured at the second measurement position. Figure 2 In the exemplary embodiment of , the first and second hemodynamic values ​​specifically correspond to a first pressure value p1 and a second pressure value p2. In step S103, the input unit 100 provides the pressure values ​​p1, p2 to the calculation unit 300.

[0140] In step S301, the calculation unit 300 receives the pressure value from the input unit 100 and receives the geometric parameter value from the identification unit 200. In step S302, the calculation unit 300 uses the pressure value and the optional geometric parameter value to calculate at least one diagnostic parameter indicating the hemodynamic property of the blood vessel of interest. Figure 2 In an exemplary embodiment of the present invention, the calculation unit 300 specifically calculates the volume flow rate through each segment of the blood vessel of interest, and outputs information about the calculated volume flow rate and information about the measurement location, and optionally, in step S303, outputs additional information about the pressure value used for the calculation to the modeling unit 400.

[0141] In step S401, the modeling unit 400 receives an indication of the presence of a bifurcation between the first and second measurement positions and a segmentation of the diagnostic image 10 and / or the vessel of interest from the recognition unit 200. Also in step S401, the modeling unit 400 receives from the calculation unit 300 the calculated volume flow rate and information about the measurement positions and optionally further information about the pressure values ​​used for the calculation.

[0142] In step S402, the modeling unit 400 segments the vessel of interest in the diagnostic image, or uses the vessel segmentation received from the identification unit 200 to generate a physiological model of the vessel of interest, wherein the physiological model includes a fluid dynamics model representing the fluid dynamics through the vessel of interest, and optionally includes a geometric model of the vessel of interest into the physiological model.

[0143] Based on the fluid dynamics model, the modeling unit 400 models the outflow through the bifurcation and the pressure loss due to friction between the first and second measurement locations in step S403 and corrects the calculated volume blood flow accordingly. In step S404, the modeling unit 400 provides the corrected volume flow rate to the calculation unit 300.

[0144] In step S304 , the calculation unit 300 uses the received corrected volume flow rate to calculate at least one diagnostic parameter representative thereof, and in step S305 , provides the diagnostic parameter and optionally a diagnostic image 10 to the display unit 500 .

[0145] In step S501, the display unit 500 receives diagnostic parameters and at least one diagnostic image and generates a graphical representation of at least one diagnostic parameter and optionally a graphical representation of the diagnostic image based thereon. In step S502, the display unit then displays the graphical representation to a user.

[0146] Figure 3A device 2 for assessing the coronary vasculature according to a second exemplary embodiment is schematically illustrated. The device 2 comprises an input unit 100, an identification unit 200', a calculation unit 300 and a display unit 500. The input unit 100 is configured to receive diagnostic data including intravascular pullback data 30. Figure 3 In a specific embodiment of the present invention, the intravascular pullback data 30 corresponds to pressure pullback data, which includes a plurality of pressure values ​​obtained at a plurality of intravascular locations along the longitudinal axis of the vessel of interest. Furthermore, the input unit 100 receives at least one diagnostic image 10 .

[0147] The input unit 100 provides the pressure pullback data to the recognition unit 200'. The recognition unit 200' focuses on the pressure pullback curve (ie, a curve representing a plurality of pressure values) according to the intravascular position and determines the local change of the pressure value. Figure 3 In an exemplary embodiment of the present invention, the recognition unit 200' determines the intravascular position where the local minimum appears in the pullback curve. The intravascular position corresponding to the local minimum in the pullback curve is considered as a candidate for the first measurement position. In this regard, the recognition unit 200' is particularly configured to derive one or more intravascular positions as candidate positions, each intravascular position corresponding to the local minimum of the pullback curve, and then identify one of the candidate positions as the first measurement position. Subsequently, the recognition unit 200' determines another intravascular position other than the candidate position selected as the first measurement position as the second measurement position.

[0148] The recognition unit 200' then co-registers the pullback data with the diagnostic image 10 received from the input unit 100. Thus, the recognition unit 200' will determine which intravascular position in the pressure pullback data corresponds to which position in the vessel of interest represented by the diagnostic image. Based on this co-registration, the recognition unit 200' can specifically determine whether there is any bifurcation between the first and second measurement positions, and in the case of determining that there is a bifurcation, the selected second measurement position can be ignored and a new position can be selected, or the selected first and second measurement positions can be ignored and a new first measurement position and a corresponding new second measurement position can be selected from a plurality of candidate positions. Alternatively, the recognition unit 200' can also decide to ignore the bifurcation, in particular in the case where the recognition unit determines that the bifurcation is negligible for a very small blood vessel whose outflow rate is negligible. In this context, it should be understood that the co-registration and subsequent bifurcation identification can also be performed before selecting the first measurement position from a plurality of candidate positions.

[0149] Since the pressure values ​​have been collected during the pullback recording of the pullback data, the identification unit 200 ′ can determine the first and second hemodynamic values, ie the first and second pressure values, at the first and second measurement locations directly from the pressure pullback curve.

[0150] The recognition unit 200 ′ then supplies the determined pressure values ​​p1 , p2 and optionally the co-registered diagnostic image and possible further information about bifurcations etc. to the calculation unit 300 .

[0151] The calculation unit 300 can use the pressure values ​​p1, p2 received from the input unit to determine diagnostic parameters. Since the calculation unit 300 in this embodiment does not have knowledge of any geometric parameters related to the vessel of interest, the calculation is limited to diagnostic parameters that do not require such knowledge. Figure 3 In a specific embodiment of the present invention, the pressure values ​​p1, p2 are used to calculate the coronary flow reserve (CFR). To this end, pressure values ​​must be derived from two sets of pressure pullback data, one set recorded in the resting state and the other set recorded in the hyperemic state.

[0152] The calculation unit 300 then provides the calculated diagnostic parameters and optionally the diagnostic image 10 and the first and second measurement positions co-registered therewith to the display unit 500. The display unit 500 then generates a graphical representation of the diagnostic parameters and, optionally, of the diagnostic image 10. Figure 3 In the exemplary embodiment of , the graphical representation generated by the display unit 500 corresponds to a graphical representation of the diagnostic image 10 , wherein the first and second measurement positions are visually indicated and the calculated diagnostic parameters are presented.

[0153] Figure 4 A flow chart of a method for assessing the coronary vasculature according to a second exemplary embodiment is shown.

[0154] In step S101, the input unit 100 receives diagnostic data including intravascular pullback data 30. More specifically, according to Figure 4 In an exemplary embodiment of the present invention, the input unit 100 receives pressure pullback data including a plurality of pressure values ​​obtained at a plurality of intravascular locations. In addition, in step S101, the input unit 100 receives at least one diagnostic image 10. In step S102, the input unit 100 provides the pressure pullback data to the recognition unit 200'.

[0155] In step S201', the pressure pullback data 30 are received at the recognition unit 200'. The recognition unit 200' derives a corresponding pressure pullback curve from the pressure pullback data in step S202' and uses the pressure pullback curve to determine local changes in pressure values ​​obtained during pullback recordings at a plurality of intravascular locations. Figure 4In an exemplary embodiment of the present invention, the identification unit 200' specifically identifies the local minimum and / or maximum in the pullback curve. In step S203', the identification unit 200' designates the intravascular positions corresponding to the local minimum and maximum as potential candidate positions, and in step S204' selects a specific candidate position as the first measurement position and another intravascular position generally located at the distal end or the proximal end of the candidate position as the second measurement position.

[0156] In step S205 ′, the recognition unit 200 ′ co-registers the diagnostic image 10 to the pressure pullback data 30 , and in step S206 ′, uses the co-registration to determine whether there is a bifurcation between the first and second measurement positions.

[0157] If there is no bifurcation between the first and second measurement positions, the recognition unit proceeds directly to step S208', in which it derives the pressure values ​​p1, p2 from the pressure pullback data. In case a bifurcation is detected, the recognition unit 200' first reselects the first and / or second measurement position as described above in step S207', or alternatively ignores the bifurcation. Only after the reselection (or decision to ignore) does the recognition unit 200' proceed to step S208'.

[0158] Once the pressure values ​​p1 , p2 have been obtained in step S208 ′, the recognition unit 200 provides these pressure values ​​p1 , p2 together with the optionally co-registered diagnostic image and possible further information to the calculation unit 300 in step S209 ′.

[0159] In step S301, the calculation unit 300 receives the pressure values ​​p1, p2, and in step S302 calculates the diagnostic parameter based on the pressure values. Figure 4 In a specific embodiment of the present invention, the calculation unit 300 specifically uses the received pressure values ​​p1, p2 to calculate the CFR. As described above, the calculation unit 300 must receive the pressure values ​​p1, p2 for both the resting state and the hyperemic state for calculating the coronary flow reserve (CFR).

[0160] In step S302 , the calculation unit 300 then provides the calculated diagnostic parameters and optionally the diagnostic image 10 together with information about the first and second measurement positions which have been co-registered to the diagnostic image 10 to the display unit 500 .

[0161] In step S501, the display unit 500 receives diagnostic parameters and optionally a diagnostic image 10 and further information. In step S502, the display unit generates a graphical representation of the diagnostic parameters and optionally a graphical representation of the diagnostic image 10 and presents the graphical representation to a user.

[0162] Although in the above-mentioned embodiments, diagnostic images have been obtained using X-ray angiography, it should be understood that in other embodiments, diagnostic images can be obtained by other imaging methods, such as spiral computed tomography or sequential computed tomography, magnetic resonance imaging, ultrasound imaging, etc.

[0163] In addition, it should be understood that although in the above embodiments, the recognition unit and the modeling unit are implemented as two separate entities, the recognition unit and the modeling unit may also correspond to the same entity. More specifically, they may be implemented as individual modules and / or computer programs to be executed by a processing device.

[0164] Furthermore, although in the above embodiments, coronary physiology has been evaluated, in other embodiments, other physiology of the human body may be modeled as well. For example, the method may be applied to evaluate peripheral arteries of the human body.

[0165] It will also be appreciated that, although in the above-described embodiments the cross-sectional area of ​​the blood vessels and the respective blood vessel diameters have been used as geometrical parameters, other geometrical parameters may likewise be derived.

[0166] Although in the above embodiments, the diagnostic parameters indicative of hemodynamic properties are related to volumetric blood flow and / or coronary blood flow reserve, it should be understood that other diagnostic parameters may also be derived, such as blood flow velocity, blood pressure, blood viscosity, vessel wall friction, etc.

[0167] Furthermore, it should be understood that, in the above embodiments, the fluid outflowing from the blood vessel of interest through each blood vessel branch has been evaluated and modeled, and the above principles can also be used to evaluate and model the fluid flowing into the blood vessel of interest.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] The procedures performed by one or several units or devices, such as receiving diagnostic data, identifying the first and second measurement locations, generating a physiological model, calculating diagnostic parameters, etc., may be performed by any other number of units or devices. Therefore, these procedures according to the invention may be implemented as program code units of a computer program and / or as dedicated hardware.

[0172] The computer program may be stored / distributed on an appropriate medium, such as an optical storage medium or a solid-state medium, which is provided 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.

[0173] Any reference signs in the claims should not be construed as limiting the scope.

[0174] The invention relates to an apparatus for assessing a hemodynamic property in a coronary vasculature, comprising: an input unit for receiving diagnostic data of a vessel of interest in the vasculature, and an identification unit for identifying a first measurement location at which a first hemodynamic value of a first hemodynamic property is derived and a second measurement location at which a second hemodynamic value of the first hemodynamic property is derived using the diagnostic data. The apparatus further comprises a calculation unit for calculating at least one diagnostic parameter representing a second hemodynamic property in the vessel of interest based on the first hemodynamic value and the second hemodynamic value.

[0175] By means of the device, suitable measurement locations for in situ measurement of a first hemodynamic property can be identified, thereby allowing approximation of diagnostic parameters regarding a second hemodynamic property different from the first hemodynamic property without having to directly measure said second hemodynamic property.

Claims

1. An apparatus for assessing coronary vasculature, comprising: an input unit configured to receive diagnostic data of a vessel of interest in the vascular system, the diagnostic data comprising one of pressure pullback data and a diagnostic image; an identification unit configured to use the diagnostic data to identify: a first intravascular measurement location, wherein a first hemodynamic value of a first hemodynamic property is derived at the first intravascular measurement location, wherein the identification of the first intravascular measurement location comprises determining a location exhibiting one of: a local pressure change in the pressure pullback data and a stenosis in the diagnostic image, and a second intravascular measurement location, wherein a second hemodynamic value of the first hemodynamic property is derived at the second intravascular measurement location, wherein the identification of the second intravascular measurement location comprises identifying a segment of the blood vessel that exhibits a constituent slope in a pullback curve derived from the pressure pullback data or that does not exhibit any stenosis in the diagnostic image, and identifying a further intravascular location as the second intravascular measurement location such that the second intravascular measurement location is located in the identified segment and such that the second intravascular measurement location is not affected by stenosis; and a calculation unit configured to calculate at least one diagnostic parameter representing a second hemodynamic property in the vessel of interest based on the first hemodynamic value and the second hemodynamic value; wherein the input unit is configured to: receive the first hemodynamic value of the first hemodynamic property derived at the measurement position within the first blood vessel, and receive the second hemodynamic value of the first hemodynamic property derived at the measurement position within the second blood vessel; wherein the first hemodynamic property comprises the pressure in the vessel of interest; and Therein, the calculation of the at least one diagnostic parameter comprises: determining the coronary flow reserve and / or the volume flow rate and / or the flow velocity of the blood flow in the vessel of interest.

2. The apparatus according to claim 1, further comprising: a modeling unit configured to generate a physiological model of the blood vessel of interest based on the diagnostic image, wherein the physiological model includes a fluid dynamics model; wherein The calculation of the at least one diagnostic parameter representative of the second hemodynamic property is performed based on the fluid dynamics model.

3. The device according to claim 1, wherein: The identifying of the first intravascular measurement position and the second intravascular measurement position further includes: determining a location of a bifurcation in the vessel of interest based on the diagnostic image; and When the bifurcation is determined to be located at a position along the longitudinal axis of the vessel of interest that is proximal to the additional intravascular location, the additional intravascular location is excluded.

4. The device according to claim 2, wherein: The identifying of the first intravascular measurement position and the second intravascular measurement position further includes: determining a location of a bifurcation in the vessel of interest proximate to the additional intravascular location based on the diagnostic image; and The calculating of the at least one diagnostic parameter based on the fluid dynamics model comprises correcting the at least one diagnostic parameter by simulating outflow through the bifurcation using the fluid dynamics model.

5. The device according to claim 2, wherein: The calculating of the at least one diagnostic parameter based on the fluid dynamics model comprises: simulating a correction of the at least one diagnostic parameter by using the fluid dynamics model to simulate a vascular friction between the first intravascular measurement location and the second intravascular measurement location.

6. The device according to claim 1, wherein: When the diagnostic data includes the pressure pullback data, The identifying of the first intravascular measurement position and the second intravascular measurement position further includes: Co-registration of the diagnostic image with the pressure pullback data; and The first intravascular measurement position and the second intravascular measurement position are indicated in the diagnostic image.

7. A method for assessing coronary vasculature, comprising: receiving diagnostic data of a vessel of interest in the vasculature, the diagnostic data comprising one of pressure pullback data and a diagnostic image; Use the diagnostic data to identify: a first intravascular measurement location, wherein a first hemodynamic value of a first hemodynamic property is derived at the first intravascular measurement location, wherein the identification of the first intravascular measurement location comprises determining a location exhibiting one of: a local pressure change in the pressure pullback data and a stenosis in the diagnostic image, and a second intravascular measurement location, wherein a second hemodynamic value of the first hemodynamic property is derived at the second intravascular measurement location, wherein the identification of the second intravascular measurement location comprises identifying a segment of the blood vessel that exhibits a constituent slope in a pullback curve derived from the pressure pullback data or that does not exhibit any stenosis in the diagnostic image, and identifying a further intravascular location as the second intravascular measurement location such that the second intravascular measurement location is located in the identified segment and such that the second intravascular measurement location is not affected by stenosis; receiving the first hemodynamic value of the first hemodynamic property derived at the first intravascular measurement location, and receiving the second hemodynamic value of the first hemodynamic property derived at the second intravascular measurement location; wherein the first hemodynamic property comprises the pressure in the vessel of interest; and calculating at least one diagnostic parameter representing a second hemodynamic property in the vessel of interest based on the first hemodynamic value and the second hemodynamic value; Therein, the calculation of the at least one diagnostic parameter comprises: determining the coronary flow reserve and / or the volume flow rate and / or the flow velocity of the blood flow in the vessel of interest.

8. The method according to claim 7, wherein: The identifying of the first intravascular measurement location and the second intravascular measurement location includes indicating the first intravascular measurement location and the second intravascular measurement location to a user.

9. A computer program product comprising a computer program for controlling an apparatus according to any one of claims 1 to 6, the computer program being adapted to perform a method according to any one of claims 7 or 8 when run by a processing unit.

10. A computer readable medium having stored thereon a computer program according to claim 9.

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