WO2022022994A1

WO2022022994A1 - Modelling vascular prosthesis rotation

Info

Publication number: WO2022022994A1
Application number: PCT/EP2021/069198
Authority: WO
Inventors: Andreas HOLZAMER; Michael HILKER
Original assignee: Universitätsklinikum Regensburg
Priority date: 2020-07-27
Filing date: 2021-07-09
Publication date: 2022-02-03

Abstract

A computer implemented method for preoperative modelling of a rotational orientation of a reference point on an intervention device, relative to a modelled vascular feature of a patient, is described. The method comprises obtaining 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the intervention device, obtaining a first rotational orientation of a reference point on the intervention device at a first location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data, and generating a second rotational orientation of the reference point at a second location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data.

Description

MODELLING VASCULAR PROSTHESIS ROTATION

Technical Field

This disclosure relates to a computer-implemented method for preoperative modelling of a rotational orientation of a reference point on an intervention device, relative to a modelled vascular feature of a patient, and an associated apparatus, system, computer program element, and computer readable medium.

Background

Traditional approaches for cardiac valve replacement require direct surgical access to a patient’s heart via a sternotomy or a thoracotomy. These protocols may require that a patient’s heart is stopped, and that a cardiopulmonary bypass is installed for the duration of the intervention. In recent years, less invasive transcatheter cardiac valve replacement procedures (for example, Transcatheter Aortic Valve Implantation (TAVI)) have grown more significant. These therapies are generally referred to as percutaneous heart valve replacement therapies.

Percutaneous heart valve replacement therapies are gaining wider acceptance as a method of treating cardiac conditions such as aortic valve stenosis, for example. However, the surgical procedure implied by percutaneous heart valve replacement therapies remains invasive and complicated. Accordingly, tools that may be used for the pre-operative planning of percutaneous heart valve replacement therapies may still be improved with the aim of improving patient outcomes.

Summary

According to a first aspect, there is provided a computer implemented method for preoperative modelling of a rotational orientation of a reference point on an intervention device, relative to a modelled vascular feature of a patient. The method comprises: obtaining 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the intervention device; obtaining a first rotational orientation of a reference point on the intervention device at a first location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data; and generating a second rotational orientation of the reference point at a second location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data. An effect is that by computing first and second rotational orientations at two different locations on a route representing a vasculature, the incremental rotation of a device along a step of the route caused by the variation in direction of the route along the step may be computed. Accurate knowledge of the rotation of a device when advanced along the route may enable improvements in the final positioning of the device to be obtained based on the introduction location, for example.

In a particular embodiment of the first aspect, the computer implemented method comprises receiving input data comprising an intended rotational orientation of the reference point, the intervention device, or of the prosthesis, at a modelled deployment location of a prosthesis, and calculates output data comprising a first introduction lead angle of the prosthesis when mounted on the intervention device at the modelled introduction location. The calculation of the first introduction lead angle is based on a first modelled rotation difference of the intervention device between the modelled introduction location and the modelled deployment location.

A specific improvement according to the aforementioned embodiment is that commissural posts of a prosthesis, such as a transcatheter aortic valve prosthesis, can be more closely aligned with the native commissural points of an aortic root by an in particular preoperative step of calculating an introduction lead angle of a device. The final rotational placement of the prosthesis optionally also accounts for the position of the native ostia in the right and left aortic sinuses. Such a calculated implantation might ease, or in a worst case scenario even allow future interventional coronary access in percutaneous coronaiy interventions. Commissural aligned implantation of the prosthesis is also important for the possibility of future redo-transcatheter valve implantation in combination with bioprosthetic or native aortic scallop intentional laceration (BASILICA) after deterioration of biologic transcatheter valves. Furthermore, commissural malalignment seems to be associated with central regurgitation by dysfunctional leaflet coaptation. Next to the direct haemodynamic disadvantage, this effect is suspected to cause accelerated prosthesis degeneration.

Therefore, techniques to achieve an intended rotational orientation of transcatheter aortic valve prosthesis might significantly improve the procedure’s outcome. The introduction lead angle may be calculated to enable placement of a prosthesis at a deployment location, wherein the rotational alignment of the prosthesis at the deployment location provides a maximum alignment difference of the commissural posts of the prosthesis to the native valve commissures to a rotational accuracy of plus or minus 25⁰, 20°, 15⁰, io°, or 5°. (Where the highest rotational accuracy is a rotational alignment of the commissures of the prosthesis that exactly matches the alignment of the native commissures of the patient).

According to a second aspect, there is provided an apparatus configured to preoperatively model a rotational orientation of a reference point on an intervention device, relative to a modelled vascular feature of a patient. The apparatus comprises: an input data interface; a data memory; a processor; and an output data interface.

The input data interface is configured to obtain 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the intervention device. The 3D anatomical model data is stored in the data memory. The processor is configured to load the 3D anatomical model data from the data memory, and to obtain a first rotational orientation of the reference point on the intervention device at a first location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data.

The processor is configured to generate a second rotational orientation of the reference point at a second location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memory.

According to a third aspect, there is provided a computer program element for controlling an apparatus according to the second aspect which, when executed by a processor, is configured to carry out the method of the first aspect.

According to a fourth aspect, there is provided a non-transitory computer readable medium having stored the computer program element according to the third aspect. According to a fifth aspect, there is provided an introducer apparatus. The introducer apparatus comprises: a distal tube portion capable of introduction into the vasculature of a patient; and a proximal aperture portion.

The distal tube portion and the proximal aperture portion form a lumen for introduction of an interventional device. A proximal end of the proximal aperture portion is further provided with an introducer alignment reference configured to display an introduction lead angle of an interventional device, when an interventional device is introduced into the lumen of the proximal aperture portion.

According to an sixth aspect, there is provided a method for implanting a transcatheter prosthesis into a patient, comprising: calculating an introduction lead angle of an undeployed transcatheter prosthesis according to the first aspect or its embodiments, and arranging the undeployed transcatheter prosthesis relative to a reference point on an intervention device; inserting the intervention device comprising the undeployed transcatheter prosthesis into an introducer, wherein the undeployed transcatheter prosthesis is introduced at the introduction lead angle; delivering the undeployed transcatheter prosthesis to an implantation location; and deploying the transcatheter prosthesis at the implantation location; and withdrawing the intervention device from the patient.

Subsidiary embodiments of the aspects disclosed above are defined in the dependent claims, to which the reader should now refer.

In the following specification, the term “distal” and “proximal” are used in the sense of describing the relative position of a reference point of an interventional device on a modelled route between an introduction location and to an implantation location of a prosthesis in 3D anatomical model data representing the anatomy of a patient. The term “distal” refers to a reference point on an intervention device, delivery system, or the modelled route that is closer, in use, to an implantation location than a feature referred to as “proximal”. For example, a delivery system may comprise a handle at its proximal end (close to, or held by, an interventional cardiologist), and an intervention device at its distal end (close to, or at, an implantation location). In the following specification, a “prosthesis” is an artificial element intended to be introduced into a vasculature of a human patient. The prosthesis is collapsible, to enable trans-vascular delivery via a delivery catheter. The prosthesis may be deployed by balloon inflation, or may be self-expandable when a sheath constraining the prosthesis is withdrawn. For example, the prosthesis may comprise a self-expanding nitinol (TM) frame. Although the present specification focuses on transcatheter heart valve replacement using transcatheter aortic bio prostheses, for example, the techniques outlined herein are applicable to other forms of transcatheter vascular approach that require a form of rotational tracking.

The term “3D anatomical model data” refers to a data structure comprising, for example, a voxel intensity map representative of the interior anatomy of a patient, optionally a patient vasculature. It is not essential that the “3D anatomical model data” provides information about all anatomical features of a patient, provided at least one vascular route of the patient is present. The 3D anatomical model data may be acquired from a multi-slice computed tomography scan, or MRI scan. The 3D anatomical model data may have pre-processing operations applied such as filtering, and segmentation, to extract at least one vascular route. The 3D anatomical model data may be registered by rigid, or elastic, registration to other 2D or 3D samples of patient anatomical data. The 3D anatomical model data may be obtained from a PACS system and be in DICOM format, for example.

The term “preoperative modelling”, as used in the following specification, means that no part of the technique discussed in the following specification requires a surgically invasive step to occur involving human patient. The technique discussed in the following specification is based on 3D anatomical model data of patient that may be acquired, for example, in a pre-operative CT or MRI scan. In an embodiment, the output of the technique is the preoperative generation of an introduction lead angle informing an interventional cardiologist of the optimal introduction angle of the prosthesis into a patient. Graphical user interface aspects of the technique are discussed, but these are also generated preoperatively and require no feedback from a surgical environment.

The term “intervention device” defines an object that is introduced into a patient’s vasculature, and advanced along it to a deployment location of a prosthesis. The object is and subsequently removed from the patient, following a deployment of the prosthesis. Optionally, the intervention device supports a deployable prosthesis. However, the use of a deployable prosthesis is not essential because the rotation of other types of intervention devices that are not capable of deploying prostheses may be calculated according to techniques of this specification.

For example, the rotation along a vascular approach during deployment of an electrified wire catheter used in the BASILICA procedure (“bioprosthetic or native aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction”) may be modelled according to the technique of this specification.

The term “reference point on the intervention device” defines an arbitrary reference location on the intervention device that does not move, relative to the rest of intervention device, as a delivery catheter supporting the intervention device is advanced along a patient vasculature. A structural feature is not specially provided to serve as the reference point - it is an arbitrary designation of an existing feature of the intervention device and used only for the purpose of simulating (tracking) the rotation of the intervention device along the modelled route as it is simulated preoperatively in simulation software.

For example, the “reference point” may be a coupling means, such as stent holder, of a collapsed stent mounted on the intervention device. The “reference point” maybe a radiopaque marker on a portion of the intervention device, and or a prosthesis mounted to the intervention device, that does not move relative to the frame of reference of the intervention device from the introduction of the intervention device until a time instant immediately before deployment. Alternatively, the reference point is a reference portion of the intervention device. The reference point is a static feature of the intervention device or prosthesis during insertion and positioning of the intervention device. A reference point may be designated on a constraining sheath member, provided this designation is only valid in the simulation prior to linear translation of the constraining sheath member with respect to the intervention device.

The term “rotational orientation” refers, in broad terms, to the tendency of a reference point on the intervention device to twist around the centreline of the vasculature as it is advanced towards deployment location.

In more formal terms, given an arbitrary modelled route through 3D space, as a reference point moves along the modelled route, a tangent vector, a normal vector, and a binormal vector are defined. The orientation of the tangent vector, the normal vector, and the binormal vector change in response to curves or tortuosities at each location on the modelled route. At each location along the modelled route a 2D plane is defined by the normal vector and the binormal vector. As the reference point of the intervention device progresses from a first location to a second location along the modelled route, the 2D plane defined by a plane orthogonal to the normal vector and the binormal vector will rotate, unless the modelled route is a perfectly straight line. The degree of rotation of the 2D plane defined by the normal vector and the binormal vector may, in example, represent the changing “rotational orientation” of the prosthesis at a given location on the modelled route.

As used herein, the terms “comprises”, “comprising”, “includes”, “including”, “has”, “having”, or any other variation thereof, are intended to cover a non-exclusive inclusion.

Description of the Drawings

FIG. la schematically illustrates optional transcatheter aortic valve replacement access routes.

FIG. lb schematically illustrates the aortic root, ascending aorta and descending aorta of an aortic access route.

FIG. lc schematically illustrates the aortic valve region of an aortic root.

FIG. id schematically illustrates a native aortic valve viewed from the ascending aorta towards the left ventricle along the line of the ascending aorta during diastole.

FIG. 2a schematically illustrates a side view of an exemplary prosthesis when expanded (a valve stent) comprising pericardium valve material.

FIG. 2b schematically illustrates a side view of an exemplary prosthesis (a valve stent) omitting the pericardium valve material.

FIG. 3a schematically illustrates an example of a cross section of a distal end of an intervention device (mounted on a delivery catheter) in a non-deployed configuration.

FIG. 3b schematically illustrates an example of the external surface marking of an intervention device (mounted on a delivery catheter) in a non-deployed configuration.

FIG. 4 schematically illustrates a plan view of a delivery system comprising a proximal portion, a delivery catheter, and an intervention device, as assembled prior to introduction into a patient.

FIG. 5 schematically illustrates an introducer for use with the deliveiy system according to a fifth aspect.

FIG. 6 schematically illustrates a geometrical simplification of the rotation problem when introducing an intervention device into a patient. FIG. 7 schematically represents a computer-implemented method according to the first aspect

FIG. 8a shows a graphical representation of a prosthesis at a deployment location, with the rotational position in the implantation plane calculated according to the technique of the first aspect.

FIG. 8b shows an enlarged version of a modelled deployment region in FIG. 8a. FIGS. 9a-f show a graphical representation of a modelled approach of a prosthesis on a deployment location as modelled according to the technique of the first aspect

FIG. io schematically represents an example of a graphical user interface in accordance with embodiments.

FIG. li schematically represents a further example of a graphical user interface in accordance with embodiments.

FIG. 12 schematically represents an apparatus according to a second aspect.

Note: The figures are not drawn to scale, are provided as illustration only and serve only for better understanding but not for defining the scope of the invention. Where possible, the same logical entities share the same reference numeral. No limitations of any features of the aspects or embodiments should be inferred from these figures.

FIGS. 2a and 2b are side views of the “Acurate” (TM) aortic bio prosthesis offered by Boston Scientific Corporation (TM).

Detailed Description

Percutaneous heart valve replacement therapies, of which transcatheter aortic valve implantation (TAVI) is an example, involve the introduction of a collapsed prosthesis via a vasculature of a patient to an implantation site. Typically, the function of the leaflets (cusps) of a diseased native valve are replaced by cusps in the replacement prosthesis.

For example, an aortic valve maybe replaced by delivering a collapsed prosthesis to an aortic root 17 via a patient’s femoral artery tod. This requires the introduction of an intervention device carrying a undeployed prosthesis (valve stent) into a vascular pathway of the patient.

During the approach of the undeployed prosthesis to the aortic valve via the ascending aorta 16, and when the undeployed prosthesis arrives at the implantation position (for example, at a point between the aortic annulus and the ascending aorta 16), the interventional cardiologist monitors the undeployed prosthesis carried upon the intervention device prior to deployment to ensure correct positioning of the prosthesis following deployment.

Typically, the monitoring of the undeployed prosthesis and intervention device is performed using 2D X-ray fluoroscopy. A prosthesis is identifiable in a 2D X-ray fluoroscopy image sequence because it is made of metallic substance. In addition, many prostheses carry radiopaque markers for improved visibility. Typically, a fluoroscopic view perpendicular to the native aortic valve (the “coplanar” view) is preferred to facilitate a high quality deployment. The minimally invasive advantages of percutaneous heart valve replacement procedures are progressively being indicated for younger patients. Therefore, a durable and high quality prosthesis placement is becoming more important.

For the purposes of TAVI, what maybe considered a high quality prosthesis deployment varies based on the type of prosthesis used and the anatomy presented by a patient. Typical prosthesis deployment aims, inter-alia, to secure anchoring of the prosthesis in the aortic root 17, to enable appropriate haemodynamic function, for low pressure gradients, for absence of obstruction of the coronary ostia, for absence of interference of the prosthesis with cardiac conduction tissue proximate to the native leaflets, for an improved valve surface area, and for a low degree of para-valvular leakage (PVL).

Improved prosthesis deployment can be provided by improved preoperative planning. Improved preoperative planning does not require surgical intervention on a patient but at least the provision of imaging data of the patient acquired prior to an intervention on that patient.

One aspect of improving the positioning of prostheses in TAVI concerns how to provide an optimal rotational orientation of the prosthesis immediately prior to the expansion of the prosthesis into the native anatomy. Conventionally, the practice has been to insert and advance an undeployed prosthesis into a patient with no account being taken of the variation in prosthesis rotation along the approach route, until the prosthesis had approached the field of view of the 2D fluoroscopy in the ascending aorta 16. Typically, the field of view of the 2D fluoroscopy displays a very limited section of the aortic arch.

However, by the time that a undeployed prosthesis has reached the ascending aorta 16, significant adjustment to the rotational position of the undeployed prostheses are more difficult to apply using the delivery catheter of the intervention device. It would, therefore, be desirable to improve the accuracy of the post operative rotational alignment of a deployed prosthesis using preoperative planning procedures.

FIGS, la and lb schematically illustrate some transcatheter aortic valve replacement access routes. For example, transcatheter aortic access may be obtained using a trans carotid route loa, a transcaval route tob, a transiliac route toe, a transfemoral route tod, a transaortic route toe, or a subclavian route tog.

This specification focuses on the transfemoral route tod as an example. During a transfemoral approach, an introducer is positioned in at least one of the right or left transfemoral artery. The intervention device (delivery system) is advanced via the introducer into the right or left transfemoral artery, along the iliac artery, along the descending aorta n, around the aortic arch 12 (past the left subclavian artery 13, the left common carotid artery 14, and the brachiocephalic artery 14), and into the ascending aorta 16.

At the end of the ascending aorta 16, the intervention device arrives at the aortic root 17 that is a broadening of the ascending aorta 16 to into the right, left, and non coronary aortic sinuses 20a-c. The left aortic sinus 20a connects to the left coronary artery 19 via the left coronary ostium 19a. The right aortic sinus 20b connects to the right coronary artery 18 via the right coronary ostium 18a. The aortic root 17 also connects the ascending aorta 16 to the left ventricle. The passage of the intervention device around the aortic arch with its relatively high anatomical variability is responsible for a substantial degree of rotational change of a reference point on the interventional device.

FIG. lc schematically illustrates the aortic root 17 located in between the ascending aorta 16 and the upper part 20 of the left ventricle of the heart prior to the introduction of a prosthesis (valve stent). A skilled reader will appreciate that the aortic root 17 region illustrated in FIG. lc is not illustrated to anatomical levels of detail, but is intended to show the significant portions of the aortic root 17 relevant during a TAVI procedure in a schematic manner.

During deployment, the undeployed prosthesis is advanced along the aortic centre-line 27. Typically, the tip of an intervention device extends into the left ventricle LVOT whilst the intervention cardiologist aligns the intervention device with respect to the anatomy of the native leaflets 23, the aortic sinuses 2oa-c and/or ascending aorta 16. Some important aspects of the alignment will be discussed subsequently. Dimensions and locations of the aortic root 17 that may be significant during deployment are, for example, the aortic root diameter 21, left coronary height 22, native leaflets 23, LVOT diameter 24, annulus diameter 25, and the Sinus Tube Joint (STJ) 26.

FIG. id schematically illustrates a native aortic valve viewed from the ascending aorta 16 towards the left ventricle LVOT along the line of the ascending aorta 16, during diastole.

The Right Coronary Cusp (RCC) 29b and the Left Coronary Cusp (LCC) 29a abut at the commissure 28b. The Left Coronary Cusp (LCC) 29a and the Non Coronary Cusp (NCC) 29c abut at the commissure 28c. The Right Coronary Cusp (RCC) 29b and the Non Coronary Cusp (NCC) 29c abut at the commissure 28b.

Therefore, each of the three native commissures 28a-c are separated by approximately 120° in the plane orthogonal to the centreline 27 passing through the aortic valve 17 (in a tricuspid aortic valve case, corresponding to the majority of patients).

The left coronary artery 19 connects to the left aortic sinus 20a via the left coronary ostium 19a. The right coronary artery 18 connects to the right aortic sinus 20b via the right coronary ostium 18a. A significant degree of variation between patients is observed in the positioning of the coronary ostia 18a 19a. Careful alignment of the prosthesis with the anatomical features of the native commissures 28a-c or the left 19a and/or right 18b coronary ostia leads to improved clinical outcomes.

In particular, the illustrated prosthesis is an “Acurate” (TM) transcatheter aortic bio prosthesis as manufactured by Boston Scientific Corporation (TM). However, a skilled person will appreciate that the technique for calculating the rotational alignment of a prosthesis as it is advanced through a vasculature is not limited to the illustrated valve. The rotation calculation detailed in this specification may be applied to any other type of prosthesis that needs to be aligned in a vascular route, and other deployable prostheses, or intra-vascular intervention devices.

The prosthesis 30 comprises a collapsible frame made of an alloy such as nitinol. A replacement valve made from bovine or porcine pericardium, for example, is stitched to the frame. The pericardium 30a may extend over the commissural posts 35a-c. The pericardium 30a may also act as a seal between the aortic root and the aortic annulus

Three stabilization arches 3ia-c at a proximal end of the prosthesis 30 are engaged with an upper anchor crown 32. The upper anchor crown 32 is connected to the lower anchor crown 33. The lower anchor crown 33 comprises three attachment elements 34a-c at a distal end of the prosthesis 30. Typically, three leaflets of a replacement heart valve are attached to commissural posts 35a-c of the prosthesis 30. Optionally, the commissural posts 35a-c may incorporate radiopaque markers.

The stabilization arches 3ia-c serve to stabilize the prosthesis 30 in a blood vessel, such as the aorta, during deployment. The upper anchor crown 32 attaches the prosthesis 30 to the aortic side of the native aortic valve, and the lower anchor crown 33 attaches the prosthesis 30 to the ventricular side of the native aortic valve.

In use, the prosthesis 30 is, prior to introduction into a patient, attached to an intervention device (delivery device) by the three attachment elements 34a-c, for example. At this stage, the prosthesis 30 is compacted underneath first and second introducer sheath members (not illustrated) enabling independently controllable expansion, for example, of the stabilization arches 3ia-c as compared to the lower anchor crown 33.

The “Acurate” (TM) is configured to deploy in several phases. For example, in a first deployment step Si stabilization arches 3ia-c are released first, from underneath a proximal sheath. Secondly, the upper anchor crown 32 is released from underneath the proximal sheath. A second deployment step S2 comprises release of the lower anchor crown 33. A third deployment step S3 involves the release of the attachment elements 34a-c from underneath a distal sheath of the deployment system. When the third deployment step S3 has been completed, the stent valve 30 is released from contact with the intervention device (delivery device). When the prosthesis (stent valve) 30 is deployed, its average diameter increases as the deployment proximal and distal sheaths are successively withdrawn. Preferably, an arbitrary reference point on the prosthesis 30 comprises a constant axial expansion characteristic. In other words, as the deployment sheaths are withdrawn and the diameter of the stent valve 30 increases, a given point on the stent valve 30 (for example, commissural post 35b) progressively moves away from the central longitudinal axis of the stent valve 30, but the given point on stent valve 30 does not move at an angle around the central longitudinal axis of the stent valve 30.

In other words, in a prosthesis 30 exhibiting a constant radial expansion characteristic, if the commissural posts 35a-c are aligned with the native commissures 28a-c when the prosthesis 30 is undeployed, the commissural posts 35a-c will remain in alignment with the native commissures 28a-c (and eventually abut the native commissures 28a-c) when the prosthesis (stent valve) 30 is fully expanded. In other words, a constant radial expansion characteristic means that during expansion of the prosthesis, an arbitrary point on the prosthesis ideally exhibits a rotary motion component of substantially zero degrees relative to the longitudinal axis of the intervention device 36.

After expansion of the prosthesis 30, the commissural posts 35a-c are substantially in alignment with respective native commissures 28a-c. For example, such positioning may reduce or remove paravalvular leakage. Furthermore, if the commissural posts 35a-c are substantially in alignment with respective native commissures 28a-c, then there is a lowered risk that one or more of the commissural posts 35a-c could block either of the left 19a or right 18a coronary ostia.

Although the foregoing example of a prosthesis has been in terms of the “Acurate (TM)”, it will be appreciated that the discussion is applicable to many other types of expandable prosthesis.

FIG. 3a schematically illustrates an example of a cross section of a distal end of an intervention device 36 (mounted on a delivery catheter) in a non-deployed configuration, albeit without a prosthesis mounted, for ease of comprehension.

In particular, the intervention device 36 comprises a tube member T enclosing a guide wire 42, around which are mounted a tip element 38, mounting portions, (for example stent mounting portions 4a, 39b), an outer tube 40, an annular spacer member 41, and a sheath (constraining member) 43 that encloses the stent containing region 45. Optionally, one or more of the elements such as the tip element 38, the outer tube 40, and/or the annular spacer member 41 of the intervention device 36 may comprise one or more radiopaque markers 37a, 378a to enable identification and localisation of the intervention device 36 in a fluoroscopy image during implantation.

In use, the prosthesis 30 is collapsed, and mounted (crimped) onto stent mounting portions 39a, 39b prior to introduction. The intervention device 36 is introduced into the vasculature of a patient via an introducer 47a. The intervention device 36 is navigated through the vasculature to a deployment region, usually using 2D fluoroscopy in combination with radiopaque markers 37a, 38a to ensure that the intervention device 36 and stent carried upon it are aligned correctly prior to deployment. Deployment of the prosthesis 30 is effected by linearly translating the sheath 43, for example along in a direction indicated by arrow A, usually via the application of a rotary force to a first 49a or second 49b rotary member of a proximal portion 48 of a delivery system (handle).

Some delivery systems may only require the linear translation of one sheath, and thus may only have one rotary member or other sheath translation means. Stent mounting portions 39a, 39b hold the prosthesis 30 in a rotationally invariant position relative to the axis of the guide wire 42. Accordingly, the angle at which a prosthesis 30 is crimped (attached) to the intervention device 36, and the angle at which the intervention device 36 is introduced to the patient relative to the vasculature, has a significant impact on the final rotational orientation of the prosthesis relative to the native commissures 28a, 28b, 28c of the aortic root 17.

Owing to the rotational invariance of the prosthesis 30 relative to the intervention device 36 during deployment, the relative rotational stiffness of the deliveiy system 44, and owing to the fact that the commissural posts 35a, 35b, 35c of the prosthesis 30 exhibit a constant radial position during expansion of the prosthesis 30, the final rotational orientation of the prosthesis

30 relative to the native commissures 28a, 28b, 28c can be accurately predicted according to the technique of the first aspect, provided the specific anatomy of the route between the introduction location and the deployment location is known. Although not illustrated, a prosthesis 30 may, alternatively, be deployed using an expanding balloon. The rotational alignment calculation technique detailed herein is also applicable to balloon expansion prostheses.

FIG. 3b schematically illustrates an example of the external surface marking of an intervention device 36 (mounted on a delivery catheter) in a non-deployed configuration relative to an introducer 47a that has been inserted into the transfemoral access route of a patient 55. The intervention device 36 comprises at least one rotation marker 54. For example, the at least one rotation marker 54 may be a line printed on a tip element 38 of the intervention device 36, for example. The rotation marker 54 is aligned to the stent mounting portions 39a, 39b of the intervention device 36.

Optionally, the rotation marker 54 may comprise three markings, such as lines, that are visible to an operator and each aligned with commissural posts 35a-c of a prosthesis 30 when the prosthesis 30 is collapsed inside the intervention device. This facilitates the alignment of the intervention device 36 prior to insertion.

FIG. 4 schematically illustrates a plan view of a delivery system 44 comprising a proximal portion 48, a delivery catheter 46, and intervention device 36 as assembled prior to introduction into a patient. In an example, a collapsed prosthesis may be deployed by withdrawing a sheath towards the proximal direction. In an example, a collapsed prosthesis may be deployed in phases, with a proximal portion of a split sheath advanced in the proximal direction, and a distal portion of a split sheath advanced in a distal direction of the delivery catheter.

A typical delivery system comprises a proximal portion 48 having one or more adjustable portions 49b, 49c used by an intervention cardiologist to control the deployment of a prosthesis from the intervention device 36. A mechanism in the proximal portion 48 translates rotary motions of each adjustable portion 49b, 49c into linear motion of respective portions of the constraining split sheath 43 of the intervention device 36.

For example, the adjustable portions 49b, 49c are adjustable knobs. The first adjustable portion 49b maybe turned counter-clockwise with respect to a proximal-distal direction along the proximal portion 48 (in the direction of the arrow on adjustable portion 49b). When the first adjustable portion 49b is rotated, a proximal portion of the constraining sheath may be linearly translated in a proximal direction of the delivery system 44 (towards the operator) to enable the deployment of a plurality of stabilization arches 3ia-c of a prosthesis 30.

The second adjustable portion 49c may be turned counter-clockwise with respect to a proximal-distal direction along the proximal portion 48 of the delivery system (in the direction of the arrow on adjustable portion 49b). When the second adjustable portion 49c is rotated, a distal portion of the constraining sheath 43 may be linearly translated in a distal direction of the delivery system 44 (away from the operator) to enable the deployment of the upper anchor crown 32. Further rotation of the second adjustable portion 49c causes the deployment of the lower anchor crown 33 of the prosthesis 30. A skilled person will appreciate that the deployment of a multi-phase stent is not essential, and the technique detailed herein may be applied to many types of stent delivery sequence.

Optionally, the proximal portion 48 comprises a Luer valve 53 to enable the introduction of contrast medium into the delivery system 44.

The proximal portion 48 may comprise a fixed body portion 49a that is not configured to rotate in the manner of the first 49b and/or second 49c adjustable portions. In other words, fixed body portion 49a may be a part of a rigid chassis of the proximal portion 48 to which other elements are mounted. An interventional cardiologist may use the fixed body portion 49a as a rigid handle when advancing the intervention device to the deployment location, for example.

The fixed body portion 49a may comprise a rotational indicator 51. Optionally, the rotational indicator 51 is a line printed on the casing of the fixed body portion 49a proximal to an introducer abutment portion 52. Analogously to the intervention device rotation marker 54, the rotational indicator 51 enables an intervention cardiologist to assess the rotation of the intervention device 36 of the delivery system relative to the introducer 47a, when the delivery system 44 has been advanced a significant distance inside a patient.

Optionally, the proximal portion 48 comprises a safety stop 50a. The safety stop may be in the form of a pin, or a mushroom-shaped projection. The safety stop prevents one or more of the first 49b and second 49c adjustable portions of the proximal portion 48 from being inadvertently rotated at an inopportune moment, such as when the intervention device 36 is not at the deployment location. The rotation of the safety stop 50a relative to the introducer can serve as another indication of the introduction lead angle F₁₁ into the introducer, because the safety stop 50a is located on a fixed portion (safety stop body portion) 50b of the proximal device 48. The magnitude of rotations of the delivery catheter 46, and hence the intervention device 36, can be tracked with reference to the degree of rotation of the safety stop 50a relative to the introducer, for example.

Optionally, the proximal portion 44 may comprise a turnable ring 50c, optionally in proximity to the safety stop 50a or another indicator for the valve orientation in relation to the delivery system. The turnable ring may comprise a plurality of visual indicia at thirty degree increments, for example. This provides the user with another orientation reference of the orientation of the delivery system relative to the introducer or the patient anatomy when it is introduced into a patient.

The preceding discussion of a delivery system 44 is illustrative in nature, and a skilled person will appreciate that many types of intervention delivery system may be used to apply a lead angle to a prosthesis 30 according to the techniques described in this specification.

FIG. 5 schematically illustrates an introducer 47a for use with the delivery system according to a fifth aspect.

The introducer 47a comprises a distal tube portion 47c capable of introduction into the vasculature of a patient. The distal tube portion 47c of the introducer is sealably coupled to a proximal aperture portion 47d of the introducer 47a. The distal tube portion 47c and the proximal aperture portion 47d form a lumen for introducing an interventional device 36.

The proximal end of the proximal aperture portion 47d is further provided with an introducer alignment reference 47b that displays an introduction lead angle F₁₁ of an interventional device 36, when introduced into the lumen of the proximal aperture portion 47d. For example, the introducer alignment reference 47b may be a projecting plastic tab with an angular reference in the manner of a protractor integrally formed with, and configured to project from, the proximal aperture portion 47d.

Optionally, the introducer 47a comprises an introducer alignment reference 47b. The introducer alignment reference 47b enables the intervention device rotation marker 54 to be more accurately aligned to the patient’s 55 anatomy immediately prior to introduction. The introducer alignment reference 47b may, for example, be a single line on the introducer 47a. Alternatively, the introducer alignment reference 47b may be a protractor-like indicator to enable an intervention cardiologist to more accurately pre-set the introduction lead angle F₁₁ of the intervention device 36 upon introduction. Therefore, an observed rotational motion of the rotation marker 54 of the intervention device 36 provides an intervention cardiologist with feedback about the introduction lead angle F₁₁ of the prosthesis 30, when the intervention device 36 is inserted into the introducer 47a.

Optionally, the introducer alignment reference 47b and an intervention device rotation marker 54 provided on the external surface of an intervention device 36 are co-designed to facilitate the accurate provision of an introduction lead angle F₁₁ by an interventional cardiologist.

Optionally, one or more rotational visual markers may be provided along the distal tube portion 47c of the delivery system. In comparison to markers on the introducer sheath, unintentional rotation of the delivery system during advancement into the sheath may be visualized. This torque of the catheter might affect the precalculated rotational orientation of the prosthesis in the target zone and can be avoided by this feature.

Optionally, the indicia is provided on a sliding portion of the introducer 47a that is rotatable around the proximal end of the proximal aperture portion 47d, to facilitate alignment of the indicia 47b with the vertical direction, for example, following placement of the introducer 47a into the patient.

In use, an interventional cardiologist may introduce the distal tube portion 47c of the introducer into the vasculature of the patient, and confirm that the introducer alignment reference 47b is aligned in a reference direction with respect to the patient, such as the vertical direction. The interventional cardiologist may position an intervention device 36 at the entry to the lumen of the proximal aperture portion 47d of the introducer 47a. The interventional cardiologist initially aligns the rotation marker 54 if the intervention device 36 with the “zero degrees” marking of the introducer alignment reference 47b, for example.

Having already computed an introduction lead angle F₁₁ using a computer implemented method according to the first aspect or its embodiments, the interventional cardiologist applies the introduction lead angle F₁₁ to the intervention device 36 immediately prior to introduction into the lumen of the proximal aperture portion 47d of the introducer 47a. This ensures that the corresponding portions of the prosthesis 30 (valve stent) are introduced into the patient at the introduction lead angle F_ΐi, thus improving the alignment of, for example, the commissural posts 35a-c with respective native commissures 28a-c.

Accordingly, a fifth aspect comprises an introducer apparatus 47a. The introducer apparatus 47 comprises: a distal tube portion 47c capable of introduction into the vasculature of a patient; and a proximal aperture portion 47d.

The distal tube portion 47c and the proximal aperture portion 47d form a lumen for introduction of an interventional device 36. A proximal end of the proximal aperture portion 47d is further provided with an introducer alignment reference 47b configured to display an introduction lead angle n of an interventional device 36, when an interventional device is introduced into the lumen of the proximal aperture portion 47d.

Use of the aforementioned introducer 47a is not essential to the techniques describe herein, because other ways of measuring the introduction lead angle are detailed, but its use may improve the accuracy of the introduction of the interventional device 36, for example.

FIG. 6 schematically illustrates a geometrical definition of the rotation problem when introducing an intervention device into a patient.

In particular, FIG. 6 shows a route 59 of an intervention device through the vasculature of a patient. In other words, the route 59 is that enclosed by a vascular feature, such as an artery of a patient. Such a route may be obtained by segmenting pre-operative multi-slice CT data, as one example. In this case, the route 59 resembles a right transfemoral approach in 3D space, with the relevant portions of the transfemoral entry tod, the descending aorta 11, the ascending aorta 16, and the aortic root 17 indicated for reference. The transfemoral approach is used as an example, and a skilled person will appreciate that the discussion applies to any approach route through a patient’s vasculature.

The route 59 is, for example, a centre line of the vasculature obtained by image processing of the segmented pre-operative multi-slice CT data.

At the location in the 3D anatomical model data representing the transfemoral entry tod (referred to subsequently as “transfemoral entry tod”, an introduction plane 60 is, for example, orthogonal to the longitudinal axis of an introducer of the intervention device 36 at the introduction location - in other words, the proximal portion of route 59.

At the transfemoral entry tod, an arbitrary model of the intervention device 36 and/ or the prosthesis 30 is aligned at a first rotational orientation q_i in the introduction plane 60.

As the arbitrary model of the intervention device 36 and/ or the prosthesis 30 is moved to an arbitrary location along the route 59, its rotational orientation changes relative to any of the frames of reference at the introduction location 56, the frame of reference at the deployment location 57, or the frame of reference of the 3D anatomical model data 58.

The main contribution to the rotation difference is provided by the aortic arch 12, although patient-specific tortuosity along other portions of the route 59 also influence the change in rotational orientation along the route.

At the location in the 3D anatomical model data representing the aortic root 17 (referred to subsequently as “aortic root 17”), the deployment plane 61 is a plane that is aligned with the patient’s targeted anatomical structure at the distal end of the route of the interventional device.

At the aortic root 17, an arbitrary model of the intervention device 36 and/or the prosthesis 30 is aligned at a second rotational orientation q₂ in the deployment plane 61.

The relationship between the first rotational orientation q_i and the second rotational orientation q₂ may be modelled using a mathematical framework such as Euler angles, quaternion calculation of the reference point on the intervention device 36 and/or the prosthesis 30, or a Bezier curve model of the route.

Given an intended rotational orientation of a reference point of the intervention device 36 (such as a stent mounting portion), or of the prosthesis 30, at the modelled deployment location 17, an optimal introduction lead angle n of the intervention device 36 or the prosthesis 30 may be calculated at the modelled introduction location tod, based on the framework discussed in FIG. 6. Optionally, the calculation of the first introduction lead angle F₁₁ is based on a first modelled rotation difference q₂ - q_i of the intervention device between the modelled introduction location and the modelled deployment location. In one example, the optimal orientation of the prosthesis 30, at the modelled deployment location 17, is the orientation where, in the deployment plane 61, the three commissural posts 35a-c of the prosthesis 30 are substantially aligned with the respective native commissures 28a-c. Such an orientation is set as q₂.

The problem to be solved, in the terms of the example of FIG. 6, is to find the value of the rotational orientation that must be applied to the prosthesis 30, using the intervention device 36 in the introduction plane 60 q_i that will enable the prosthesis 30 to be deployed in the deployment plane 61 with the rotational orientation q₂. q_i is otherwise referred to in this specification as the introduction lead angle n of the prosthesis 30, or interventional device 36.

For percutaneous approach routes, the rotation of an intervention device 36 at an introduction plane 60 in the introduction location tod of the intervention device 36, versus at a deployment plane 61 at the deployment location of the interventional device, is different relative to a fixed frame of reference. The rotation difference is caused by the tortuosity of the route followed by the interventional device. The rotation difference is patient specific.

According to a first aspect, there is provided a computer implemented method 62 for preoperative modelling of a rotational orientation of a reference point (such as a stent mounting portion) of an interventional device, relative to a modelled vascular feature 59 of a patient. The method comprises: obtaining 63 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route 59 of the interventional device; obtaining 64 a first rotational orientation q_i of the reference point of the interventional device 36 at a first location of the intervention device 36 on the route 59 inside the vascular feature of the 3D anatomical model data; and generating 65 a second rotational orientation q₂ of the reference point at a second location of the intervention device 36 on the route 59 inside the vascular feature of the 3D anatomical model data.

FIG. 7 schematically represents the computer implemented method according to the first aspect. In an example, the computer implemented method 62 may be performed using a computer program executed on a general purpose computer, optionally supplemented with a graphics accelerator, as known to a person skilled in the art.

The 3D anatomical model data is optionally obtained from pre-operative CT volume data of a patient to be operated on. Alternatively, MRI volume data may be used as a pre-operative volume data source. Optionally, the 3D anatomical model data is obtained from a hospital PACS server (Picture Archiving and Communication System), optionally in the DICOM format (Digital Imaging and Communication In Medicine).

The volume data obtained via CT, MRI, or DICOM format is applied to an image processing pipeline. The volume data is segmented to extract vascular features from the volume data. Therefore, the 3D anatomical model data originates from a segmentation of the patient vasculature from 3D volume data. The step of image segmentation, and/ or other standard CT or MRI image processing, is not essential to the technique, however, because image segmentation to obtain the vasculature can be performed offline, or at a different time or location and stored on a hospital PACS server, for example.

A variety of image segmentation approaches may be applied to extract the patient vasculature from the preoperative volume data to obtain the 3D anatomical model data.

Optionally, a route 59 is obtained in the 3D anatomical model data. For example, a user may provide markers between two locations in a route 59, or highlight segments of a segmented vasculature between a first location tod and the second location 17 that form the route 59.

Optionally, a centre line of the vascular route between the first location tod and the second location 17 is generated, using algorithms such as inverse modified distance from edge (MDFE), centre of mass (COM), binary-thinned MDFE (BTMDFE) or the like. Optionally, the centre line may be input directly from a medical professional using vascular planning software, for example. Optionally, an automatically generated centre line may be partially edited based on user interaction with the vascular planning software.

In embodiments, the rotational orientation difference between the first and second locations is calculated as a vector integral of the route between the first and second locations, and/or based on a quaternion representation of the first and second locations, or using one or more Bezier curves between the first and second locations. Optionally, the centre line may be described by a plurality of straight line vectors, and/ or Bezier curves, for example. Optionally, the open source SimVascular toolkit (TM) may be used to extract the centre line. The input to the SimVascular toolkit (TM) is CT volume data, and the output is a machine readable list of a plurality of coordinates of a vascular centre line.

A skilled person will appreciate that many other geometrical techniques may be used to compute the modelled rotations.

In an embodiment, obtaining 64 a first rotational orientation qi of the reference point of the interventional device 36 at a first location on the route of the intervention device 36 inside the vascular feature of the 3D anatomical model data may comprise the provision of an intended deployment angle at a distal portion of the modelled route, for example. In this option, the first step does not require the calculation of the first rotational orientation, but may obtain it externally.

In an embodiment, obtaining 64 a first rotational orientation qi of the reference point of the interventional device 36 at a first location of the intervention device 36 on the route of the interventional device 36 inside the vascular feature of the 3D anatomical model data may comprise generating (calculating) the first rotational orientation qi of the reference point at a first location of the intervention device 36 on the route of the interventional device inside the vascular feature of the 3D anatomical model data. The calculation method may use Euler angles, quaternion representations, and the like.

In other words, the first rotational orientation qi of the reference point of the interventional device 36 is optionally obtained externally, or calculated from the 3D anatomical patient data.

Therefore, it is not essential that two calculations of the rotational orientation at each point on the modelled route are made.

In particular, in an iterative approach, as the location on the modelled route 59 moves piece- wise along the modelled route 59, the generated second rotational orientation Q2 from an immediately previous step may be used as the obtained first rotational orientation qi of a current step. Optionally, the first rotational orientation of the reference point of the intervention is obtained as the previously generated second rotational orientation of the preceding iteration of the calculation.

Optionally, the first rotational orientation of the reference point of the intervention is generated at the first location of the route without reference to a previous iteration.

Optionally, the rotation vector of a reference point (portion) on the intervention device 36 at a first location (first modelled location) on the route (modelled route) is calculated. The rotation vector is generated relative to a common datum.

The rotation of the intervention device 36 is described by a vector between two locations on the modelled route 59. In an example, it can be calculated by rotation matrices. Therefore, to model a change from a first rotational orientation q_i to a second rotational orientation q₂, a step A(x,y,z) along the route 59 from a first location to a second location is modelled.

In a third step of the specific example, the rotation vector of a reference point on the intervention device 36 at a second location on the route is calculated.

Optionally, the calculation of the rotation along centreline P may follow the following pseudocode, where the centreline is stored as a vector of coordinates in 3D space P_I,N. The first location on the route is P_LI. The second location on the route is P_L2. The function “rotation” generically obtains the rotation of a prosthesis at a point P on the modelled route, for example by monitoring a change in Euler angle, using a quaternion approach, and the like. load(P ,_N); / /load the route in 3D anatomical data load(P_Li, P_1.2); / /load the first and second locations

/ /iterate in P between the first and second locations for x = Li + 1 to L2_: calculate rotation of reference point on intervention device along vector P_x ->

Px+i;

/ / accumulate calculated rotation: Rot = Rotation(P_x) + Rotation(P_x+0 translate valve model along vector P_x+i; end.

Output(Rot);

END.

The number of steps modelled, the location on the route 59 of the start or end locations of the steps, or the direction along the route at which the steps are computed is not essential.

For example, the rotation difference between a location lod and a location 17 (the entire route 59) may be computed. Alternatively, the rotation difference along a subset of the route can be computed. For example, the rotation difference caused by the ascending 16 and descending aorta 11 may be computed.

Optionally, a plurality of steps beginning at the transfemoral introduction location lod and ending at the aortic root 17 may be computed. This provides the rotation difference caused by moving an intervention device along the route 59.

Knowing that the rotation difference caused by moving an intervention device 36 along the route 59, and knowing the intended final position of the prosthesis 30 in the deployment plane 61, the introduction lead angle n may be computed by subtracting the rotation difference from the intended final position of the prosthesis 30, for example. Extending the pseudocode example above gives an example where the intended deployment rotation is provided, and the algorithm iterates in reverse along the modelled route 59 back to the introduction location, to provide the introduction lead angle. load(Pi,N); / /load the route in 3D anatomical data load(PLdist, PLint); / /load the first and second locations load(DeplEndRot) / /the intended deployment rotation

/ /iterate in P between the first and second locations for x = PL_dist - 1 to PLin_t: calculate rotation of reference point on intervention device along vector Px -> Px+i; / / accumulate calculated rotation Rot = Rotation(P_x) + Rotation(P_x+i)

/ / update the introduction angle IntroRot = DeplEndRot - Rot translate valve model along vector Px+i; end.

//provide the introduction lead angle: Output(IntroRot);

END.

Optionally, the desired implantation rotation at the deployment plane 6i can be chosen in a graphical user interface of a visual overlay of the CT scan of a patient’s aortic root, for example. The amount and direction of virtual rotation of the stent needed to obtain the desired position yields the introduction lead angle n for implantation.

The following paragraph is not part of the computer implemented preoperative method according to the first aspect, but is provided for illustrative purposes.

Following calculation of an introduction lead angle n according to an embodiment of the first aspect, the interventional cardiologist introduces the intervention device 36 into an introducer 47a at the intervention lead angle, optionally using rotational indicators on at least one of the introducer, interventional device 36, and/ or proximal device 48 to ensure that the intervention lead angle is optionally applied.

Pre- operatively obtained patient data is used to calculate the rotation transformation applied to the intervention device 36 as a result of translating between an introduction location and a deployment location alongside a route 59, the intervention device 36, and therefore the prosthesis 30 is more likely to be deployed in an orientation that is close to an ideal orientation. For example, the commissural posts 35a-c of a transcatheter aortic bio prosthesis are more likely to be closely aligned to the native commissures 28a-c of the native valve.

In an example, the method according to the first aspect is repeated a plurality of times, in order, between a first location to a second location of the route 59 (Alternatively, between a distal to proximal end of the route 59). A route 59 may have rotations computed too times, 1000 times, or 10,000 times, during the modelling of movement between the first and second locations, for example. An increase in the number of computations along the route 59 corresponds to a decrease in the step size A(x,y,z) discussed above. A decrease in the step size A(x,y,z) may improve the final accuracy of the computed rotational difference along an arbitrary section of the route 59.

Optionally, a smaller step size may be chosen along a portion of the route 59 with a higher tortuosity, or that modelling the aortic approach or ascending aorta.

FIG. 8b shows an enlarged version of a modelled deployment region in FIG. 8a showing the modelled route round the aortic arch.

In the enlarged graphical representation of FIG. 8b, the centreline 27 comprises a plurality of small points. These denote successive step locations A(x,y,z). At each step location A(x,y,z), the rotation of the prosthesis 30 is calculated. The incremental rotation of the prosthesis 30 is calculated based on the change in rotation of the prosthesis as it moves along the centreline 27

In FIG. 8b, the native commissures 28a-c are represented by the three ball-like marker traces proximal to the upper anchor crown 32 of the modelled prosthesis 30. The commissural posts 35a-c of the modelled prosthesis 30 are represented by the spike marker traces. It will be appreciated that the spike marker traces are not a part of the prosthesis 30 illustrated in FIG. 3, but are optionally included in the GUI representation to enhance the comprehension of the rotation of the modelled prosthesis 30 relative to the modelled native commissures 28a-c. In FIG. 8b, the modelled native commissures 28a-c are exactly aligned with the spike marker features. Therefore, FIG. 8b models a case of perfect alignment achieved by computation of the ideal introduction lead angle n from the 3D anatomical model data.

FIGS. 9a-f illustrate a graphical representation of the approach of a prosthesis 30 on a deployment location as calculated according to the technique of the first aspect. In the screen representations of FIGS. 8 and 9, the prosthesis 30 is shown as expanded at the first and second locations. In a practical situation the prosthesis 30 would be expanded only at the deployment location. However, for ease of intelligibility and illustrating the rotation of the features of the prosthesis model, the prosthesis 30 is displayed in FIGS. 8 and 9 at both the start and the end of the route 59. For example, the commissural post 35a is illustrated in FIGS. 8 and 9 with an emphasized triangular marker, and a rotation in its position between the start and end of the route 59 is evident.

In embodiments, the method comprises calculating a rotational orientation difference of the reference point between the first location of the prosthesis and the second location of the prosthesis.

For example, subtracting the first rotational orientation from the second rotational orientation provides the rotational orientation difference.

In embodiments, the rotational orientation difference between the first location of the reference point and the second location of the reference point is characterized by the precession of the reference point between the first and second locations of the intervention device.

In embodiments, the first location defines the rotational location of the reference point in a first plane orthogonal to a tangent of the route at the first location, and wherein the second rotational orientation defines the rotational location of the reference point in a second plane orthogonal to a tangent of the route at the second location.

In embodiments, the method further comprises obtaining a distal end location of the route in the 3D anatomical model data, wherein the second location is closer to the distal end location of the route, along the route, compared to the first location.

The term “closer to the distal end location of the route, along the route” means that the relevant distance when determining the condition is not the Euclidean distance in 3D space between the second location and the location of the distal end, but rather the integrated distance travelled along the modelled route 59 that passes through the distal and the second location.. In most cases, the integrated distance will be greater than the Euclidean distance, because in general, a patient vasculature is more tortuous than a line between two points. Accordingly, in one option, the computer implemented method may calculate the rotation of the interventional device 36 as it approaches the end location of the route 59.

In embodiments, the method further comprises obtaining a distal end location of the route, and wherein the second location is further away from the distal end location of the route, along the route, compared to the first location.

The term “further away from the distal end location of the route, along the route” means that the relevant distance when determining the condition is not the Euclidean distance in 3D space between the second location and the location of the distal end, but rather the integrated distance travelled along the modelled route 59 that passes through the distal and the second location.

Accordingly, in another option, the computer implemented method may calculate the rotation of the interventional device 36 as it moves away from the end location of the route 59. This enables direct calculation of the introduction lead angle starting from the preferred deployment location.

In embodiments, the distal end location of the route is a modelled deployment location of a prosthesis from the portion of the interventional device.

In embodiments, the route between the modelled introduction location and the modelled deployment location in the 3D anatomical model data models a transfemoral cardiac catheterization route.

For example, the distal end location may be a deployment position of a transcatheter aortic bio prosthesis, a transcatheter replacement mitral valve, a transcatheter replacement pulmonary valve, or a transcatheter replacement tricuspid valve.

In embodiments, the route within the 3D anatomical model data further comprises a proximal end location.

In embodiments, the proximal end location of the route within the 3D anatomical model data is a modelled introduction location, into a patient, of the interventional device into the vascular feature. Optionally, the proximal end location represents the insertion location of an introducer 47a into the patient anatomy.

In embodiments, the vascular feature represents a portion of a human or animal vasculature.

In embodiments, the second location is a representation of the aortic root 17 of the vasculature in the 3D anatomical model data.

In embodiments, the prosthesis is a self-expanding or balloon-expanding transcatheter valve.

In embodiments, the method further comprises receiving input data comprising an intended rotational orientation of the reference point of the interventional device 36, or of the prosthesis, at the modelled deployment location, and calculating output data comprising a first introduction lead angle n of the reference point, and/or the prosthesis when mounted on the intervention device at the modelled introduction location, wherein the calculation of the first introduction lead angle n is based on a first modelled rotation difference of the interventional device between the modelled introduction location and the modelled deployment location.

Accordingly, an interventional cardiologist may, in a preoperative planning stage, define an intended deployment angle of a prosthesis 30 that provides an improved alignment of commissures 35a-c with native commissures 28a-c. For example, the input data may comprise the coordinates in a deployment plane at the deployment location at the aortic root or sinuses.

In embodiments, the first introduction lead angle F₁₁ is the intended rotational orientation of the reference point, or of the prosthesis, at the modelled deployment location minus the rotation difference caused by the movement of the interventional device through the vascular feature in between the modelled introduction location and the modelled deployment location.

In embodiments, the first introduction lead angle F₁₁ is defined relative to a plane that is orthogonal to the longitudinal axis of an introducer of the interventional device, wherein the introducer is aligned with the route at the modelled introduction location in the 3D anatomical model data.

In embodiments, the intended rotational orientation is defined relative to a plane that is orthogonal to a tangent of the distal portion of the route of the interventional device, wherein the distal portion of the route is in between a modelled sinotubular junction and a modelled aortic annulus in the 3D anatomical model data.

In embodiments, the method further comprises modelling a deformation of a portion of the vascular feature in the 3D anatomical model data, caused by an insertion of an introduction device into the route at the modelled introduction location; and calculating a second introduction lead angle F₁₁ of the prosthesis at the modelled introduction location, wherein the calculation of the second introduction lead angle F₁₁ is based on a second modelled rotation difference of the reference point of the interventional device between the modelled deployment location and the modelled introduction location, accounting for the change in rotation of the interventional device caused by a deformation of the reference point of the vascular feature due to the presence of the introduction device.

A deformation of significant portion of a patient vasculature may result in variation to the rotation experienced by the interventional device 36 as it is advanced along the vasculature.

A significant source of patient vasculature deformation is the deformation caused by the introducer 47a. Accordingly, the geometry of a portion of the route 59 representing the introduction location and the subsequent section affected by the introduction of the introducer sheath may be distorted according to expected forces applied by a typical introducer 47a.

In one example, tortuosity may be defined by the arc-chord ratio. For example, a relatively tortuous right femoral arteiy may be flattened by reducing its arc-chord ratio in the 3D anatomical model data, thus modelling the effect of the insertion of an introducer 47a. The route 59 used to compute the rotational difference may comprise the flattened portion, enabling the second introduction lead angle F₁₂ to reflect a more accurate introduction lead angle accounting for deformations of the target anatomy.

In embodiments, the method further comprises calculating a third introduction lead angle Fi > of the prosthesis, wherein the calculation of the third introduction lead angle is based on a third modelled rotation difference of the reference point of the interventional device dependent on an approach via one or more of the left transfemoral artery, the right transfemoral artery, or trans carotid and transvenous access via the vena cava with crossing to the aorta or the transseptal atrial crossing. Accordingly, it is possible to account for the difference in rotational orientation of a prosthesis 30 caused by different tortuosities of the right, versus the left, transfemoral arteries, for example.

Optionally, the method comprises calculating a difference in rotational alignment of an interventional device 36 at a deployment location based on an approach via the left transfemoral artery, or via the right transfemoral artery. This enables an interventional cardiologist to choose an approach that applies the most appropriate rotational orientation at the deployment location to the intervention device 36.

In embodiments, the method further comprises displaying at least one of the first to third introduction lead angles to a user. For example, a graphical user interface (GUI) on a display of a connected computer or monitor may display the suggested introduction lead angle n in the text box.

FIG. 10 schematically represents an example of a graphical user interface in accordance with embodiments.

In embodiments, the method further comprises synthesizing a preoperative representation of the modelled deployment location in the patient using the 3D anatomical model data, or a further source of pre-operative 3D anatomical model data; displaying, via a user interface, the synthesized representation of the modelled deployment location to a user; and receiving, as input data, via the user interface, the intended rotational orientation of the interventional device at the modelled deployment location from the user based on the position of one, or more, visual markers arranged, by the user, in the visual representation of the modelled deployment location.

In embodiments, the method further comprises identifying, using automatic image recognition, at least one commissure location at the modelled deployment location in the 3D anatomical model data; and generating a first candidate rotational orientation of the prosthesis at the modelled deployment location based on the at least one commissure location.

In embodiments, the method further comprises calculating at least one of the first to third introduction lead angles of the prosthesis based on the first candidate rotational orientation of the prosthesis. In embodiments, the method comprises identifying the location of a coronary ostium at the modelled prosthesis deployment location in the 3D anatomical model data using automatic image recognition; and generating a second candidate rotational orientation of the prosthesis at the modelled deployment location based on the location of coronary ostia.

In embodiments, the method comprises calculating the first introduction lead angle F₁₁ of the prosthesis at the modelled introduction location based on the second candidate rotational orientation of the prosthesis.

In embodiments, the method further comprises comparing the first candidate rotational orientation of the prosthesis and the second candidate rotational orientation of the prosthesis; and acquiring a third candidate rotational orientation based on the comparison between the first candidate rotational orientation of the prosthesis and the second candidate rotational orientation of the prosthesis.

In embodiments, the method further comprises calculating the first introduction lead angle n of the prosthesis at the modelled introduction location based on the third candidate rotational orientation of the prosthesis.

One example of a graphical user interface (GUI) will now be described, although a skilled person will recognise that many variations of input interface design may be provided without departure from the embodiments discussed herein.

For example, the GUI 66 comprises a first window 67a enabling a user to denote at least an introduction location, a deployment location, and a route through the native vasculature on a graphical representation of the native vasculature. The graphical representation may be a 2D plane (for example, a transverse, coronal, sagittal, or oblique sagittal view). Alternatively, the graphical representation of patient vasculature maybe a 3D image capable of being reoriented and browsed by the user. The graphical representation in the first window 67a is, for example, registered to the 3D anatomical model data so that the provision of markers in the graphical representation can be resolved to realistic locations in the native anatomy.

In an example, the graphical representation in the first window 67a is generated from the same 3D anatomical model data that is used to model the rotational orientation of the intervention device. An introduction marker 68 maybe placed by user in the graphical representation of the patient vasculature to denote the introduction location.

The deployment marker 69 may be placed by user to represent a deployment location of a prosthesis 30.

Optionally, a route 59 between the introduction location in the deployment location may be automatically calculated from a generated centreline in the 3D anatomical model data, based on the location of the positioned markers 68 and 69. Therefore, a user may define the route 59 using the first window 67a.

The GUI 66 further comprises a second window 67b that a user may use to define the rotational orientation of the prosthesis 30 following introduction, and deployment.

Optionally, the second window 67b displays an optimised pre-operative view of the native valve viewed along a centreline between the ascending aorta 16 and the aortic root 17 showing the right, left, and non-coronary valve leaflets.

Optionally, the optimised pre-operative view of the native valve may be obtained from a multi slice CT image, for example. Optionally, the optimised pre-operative view of the native valve is registered (using rigid or elastic deformation, for example) to the 3D anatomical model data of the patient.

A user may optionally add one, or more, commissure markers at locations of the native commissures 28a-c to the pre-operative view of the native valve. The multi-slice CT image displayed in the second window 67b is registered to the 3D anatomical model data. Once placed, the spatial coordinates of the commissure markers are used to derive a rotational orientation of the prosthesis 30 at the deployment location based on registration between the multi-slice CT image and the 3D anatomical model data. Accordingly, the method according to embodiments of the first aspect may enable the user to plan the placement locations of commissures of the valve prosthesis 30, and to derive an introduction lead angle n of a prosthesis 30 based on the position of the commissure markers in the second window 67b of the GUI. In a similar way, a user may optionally add a marker at the position of the right ostium, or the left ostium displayed in the second window 67b of the GUI. Accordingly, the method according to embodiments of the first aspect may enable the user to plan the placement locations based on ostia locations of the native valve, and to derive an introduction lead angle F₁₁ of a prosthesis 30 based on the position of the ostium markers in the second window 67b of the GUI.

The native commissures 28a-c and/or the ostia 18a, 18b maybe detected in the multi-slice 2D CT image, or in the 3D anatomical model of the patient. For example, 2D or 3D image processing and filtering techniques are capable of recognising the distinctive appearance of the native commissures 28a-c and/or the ostia 18a, 18b. Accordingly, the GUI 66 may be configured to automatically detect suitable locations for the commissure and ostium markers and to suggest these to a user of the GUI.

Following placement of the commissure and ostium markers, the optimal introduction lead angle is computed according to an optimal implantation rotation calculated with reference to the location of the commissure and/or ostium markers in the representation of the implantation plane.

The GUI may comprise a third window 67c. The third window 67c may contain a display box 68 configured to report to a user of the GUI the preferred introduction lead angle n to be applied to an interventional device when introduced into a patient to obtain an optimal rotational position at the deployment location. Optionally, the GUI may frequently refresh the computation of the introduction lead angle F₁₁ based on the position at which the user places the trace markers on the trace of the aortic root 17 in the second window 67b. This affords a user a degree of interactive planning. Optionally, the third window 67c may comprise a selection dialog box 69 enabling selection of the computation of the introduction lead angle based on the ostia position, the commissure position, or both, for example.

Optionally, the GUI may comprise a dialog box displaying respective introduction angles based on the first, second, and third candidate rotational orientations discussed above, to enable easy comparisons between optimising the introduction angle for different considerations (the first candidate rotational orientation of the prosthesis 30 in its deployment location optimises for commissure location, the second candidate rotational orientation of the prosthesis 30 in its deployment location optimises for ostium location, and the third candidate rotational orientation of the prosthesis 30 in its deployment location attempts to find the best trade-off between the first candidate rotational orientation and the second candidate rotational orientation).

The third candidate rotational orientation may be computed using a heuristic search algorithm, for example, where the heuristic is designed to provide a compromise between a rotation to optimize suitability of the prosthesis placement for commissure and ostia locations for a specific patient anatomy in the 3D anatomical model.

It will be appreciated that the GUI 66 relies on pre-operative 3D anatomical model data and that it is not essential that surgical intervention is in progress for an introduction lead angle Onto be computed using the GUI.

In embodiments, the method further comprises displaying, via the display, at least one of the first, second, or third candidate rotational orientations of the prosthesis at the modelled deployment location in the modelled implantation plane to a user.

In embodiments, the route of the interventional device in the vascular feature is (i) the centre line of the vascular feature, or (ii) an interpolated route in the vascular feature in which the route deviates from the centre line of the vascular feature based on the radius of bends in the vascular feature.

Optionally, the variation in rotational orientation in the deployment plane may be more accurately calculated by accounting for the natural overshoot of the guide wire away from the centreline of a vessel around corners. For example, such overshoot may be observed around the aortic arch 12.

In embodiments, the method further comprises generating a simulated image and/or image sequence illustrating a simulated rotation of the prosthesis as it approaches the modelled prosthesis deployment location, wherein the simulated image and/or image sequence optionally provide a simulated representation of one or more radiopaque markers of the prosthesis and/ or intervention device.

FIG. 11 schematically represents a further example of a graphical user interface 80 in accordance with embodiments. Using the 3D anatomical model data, a rotation of a prosthesis 30 (valve stent) maybe obtained at an arbitrary location on the approach to an aortic root 17, for example. By tracking back from a preferred deployment position of the prosthesis 30 in the native anatomy, the optimal rotational orientation of the prosthesis 30 at each location in the approach to the aortic root 17 can be calculated according to the aspect and embodiments of the first method.

One or more radiopaque markers 37a, 38a may be provided on components of the delivery system 44 to enable portions of the delivery system 44 to be visible in a 2D fluoroscopic image. For example, portions of the intervention device 36, and/or portions of the prosthesis 30 such as the commissural posts 35a-c may be provided with a radiopaque ring or tab.

The graphical user interface 80 illustrated in FIG. 11 shows a radiopaque marker simulation environment. This may be used as a teaching, training, or preoperative preparation aid. This version of the GUI comprises a vascular route display 81 comprising a representation of the approach of the prosthesis 30 to the deployment location. Optionally, the representation may be segmented from 3D anatomical model data obtained from a patient. Optionally, a centreline, such as the centreline may be displayed.

The GUI further comprises an implantation plane display 82. This is a 2D simulation of the implantation plane of the aortic root 17, for example, as it might appear on a 2D fluoroscopy image. Such an image may be computed from the 3D anatomical model data, for example. The anatomical representation in the implantation plane display 82 is geometrically registered to the 3D anatomical model data used to generate the vascular route display 81.

Optionally, a modelled location of a prosthesis in the implantation plane display 82 may be input by moving a marker along the centreline 27 using a mouse pointer in the implantation plane display 82, for example.

In an embodiment, a GUI slider 84 maybe manipulated, with the markers in the vascular route display moving along the centreline 27 in proportion with the position of the GUI slider 84.

The representation of the 3D anatomical model data is shown in the vascular route display 80. Optionally, a user may select a known prosthesis type from a prosthesis menu 83. The GUI software is equipped with a model of each known prosthesis type which may also be registered to the common frame of reference of the 3D anatomical model data. Accordingly, the 3D location of the radiopaque markers of the prosthesis in the frame of reference of the 3D anatomical model data may be computed for different projected locations of the prosthesis during the approach on the vascular route.

Optionally, a ray-based projection algorithm may be used to generate a prediction 85 of the appearance of the traces of the radiopaque markers in the 2D fluoroscopy view of the implantation plane display 82 based on the projected location of the prosthesis in the 3D anatomical model data. The rotation of the prosthesis 30 relative to the 3D anatomical model may be generated using an algorithm according to the first aspect, with the prior knowledge of the desired optimal prosthesis rotation angle at the deployment location.

The prediction 85 of the appearance of the traces of the radiopaque markers may be superimposed on top of preoperative multi-slice CT data obtained from a patient to be operated on, for example. Alternatively, the prediction 85 of the appearance of the traces of the radiopaque markers may be superimposed on a neutral background to enhance clarity.

Optionally, the primary (a) and secondary (b) rotation angles of a notional C-arm may be adjusted by a user of the GUI 66 to enable the implantation plane display 82 to model an prediction 85 of the appearance of the traces of the radiopaque markers from a plurality of different C-arm angles.

In this way, the technique of this specification enables an interventional cardiologist to prepare for a surgical intervention by learning the predicted appearance of the traces of the radiopaque markers at different stages in an implantation in a specific patient, obtained using unique patient data of that specific patient, when the rotation applied is an optimal rotation following calculation of the introduction lead angle, for example.

In embodiments, a portion of the route inside the vascular feature in the 3D anatomical model data models one of: a transfemoral cardiac catheterization route, a trans carotid cardiac catheterization route, a trans subclavian cardiac catheterization route, or a venous trans clavial cardiac catheterization route.

In embodiments, the prosthesis comprises a structure that repeats three times around a circumference of the prosthesis such that the prosthesis has 3-fold symmetry in the circumferential direction. In embodiments, the rotational orientation is an orientation with respect to the 120 degree symmetry of the prosthesis.

Optionally, the introduction lead angle F₁₁ may be calculated to enable placement of a prosthesis 30 at a deployment location, wherein the rotational alignment of the prosthesis 30 at the deployment location provides a maximum alignment difference of a commissural post 35a-c of the prosthesis 30 to native commissure 28a-c to an accuracy of plus or minus 25⁰, 20⁰, 15⁰, 10°, 5⁰, or 1°.

In embodiments, the first introduction lead angle n is computed to improve the probability that a prosthesis is deployed at an optimal deployment rotation in the implantation plane.

FIG. 12 schematically represents an apparatus 72 according to a second aspect.

The apparatus 72 illustrated in FIG. 12 can be utilised to implement a computer implemented method for preoperative modelling of rotational orientation of a location on an intervention device, relative to modelled vascular feature of the patient.

According to a second aspect, there is provided an apparatus configured to preoperatively model a rotational orientation of a reference point on an interventional device, relative to a modelled vascular feature of a patient. The apparatus comprises an input data interface, a data memoiy, a processor, and an output data interface.

The input data interface is configured to obtain 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the interventional device, and to store the 3D anatomical model data in the data memoiy.

The processor is configured to load the 3D anatomical model data from the data memory, and to generate a first rotational orientation of the reference point of the interventional device at a first location of the intervention device 36 on the route of the interventional device inside the vascular feature of the 3D anatomical model data.

The processor is configured to generate a second rotational orientation of the reference point at a second location of the intervention device 36 on the route of the interventional device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memory. In embodiments, the processor is further configured to perform the steps of the method according to embodiments of the first aspect.

As an example, the apparatus 72 comprises a general-purpose personal computer (PC), upon which is executed by an operating system in the “Windows” (TM) series, “MacOS” (TM), or a Linux (TM) variant.

The input data interface 73 may comprise, for example, a network interface (such as an Ethernet interface), a universal serial bus (USB (TM)) interface, a wireless communications interface such as an 8o2.iixx series modem or a Bluetooth (TM) modem, and the like. Furthermore, the input data interface 73 may comprise an interface device facilitating use interaction capable of receiving user commands such as a mouse interface, a keyboard interface, a touchscreen interface, and the like. A skilled person will appreciate that wide range of data input techniques may be used according to the techniques of the present specification.

The processor 74 may comprise, a central processing unit of the personal computer such as an AMD “Ryzen” (TM), an Intel Core 15, 17, 19 (TM) or similar processor. A skilled person will appreciate that wide range of processors may be used according to the techniques of the present specification. Optionally, the processor 74 may be supplemented with a graphics processing unit (GPU) to accelerate the processing of graphical user interface elements.

The data memoiy 75 may comprise, for example, random access memory (RAM), read-only memory (ROM), and firmware memoiy utilised by the operating system of the apparatus 72 as appropriate. The data memory 75 may also be considered to comprise a mass storage device such as a hard disk drive or a solid state drive.

The output data interface 76 may comprise, for example, one or more of the interfaces listed above concerning the input data interface 73. Optionally, the input data interface 73 may be shared with the output data interface 73 to communicate data to other elements of the system or network.. Optionally, the output data interface may comprise a display interface (such as a monitor interface) for generating and transmitting elements for a graphical user interface to the user. Optionally, the output data interface may comprise an audio interface for generating and transmitting elements of an audio feedback to the user. According to a third aspect, there is provided a computer program element for controlling an apparatus according to the second aspect which, when executed by a processing unit, is configured to carry out the method of the first aspect or its embodiments.

According to a fourth aspect, there is provided a non-transitory computer readable medium having stored the computer program element according to the third aspect.

Therefore, according to the third and fourth aspects, a program is provided which, when running on a computer, configures the computer to perform one or more of the computer- permitted method steps discussed in this specification.

Computer program elements may be provided upon non-transitory computer readable media comprising computer-usable instructions (“code”) embodied in the computer readable medium in connection with an instruction executing system on the computer.

A computer maybe a conventional personal computer, or, for example, an embedded computer provided as part of the control system of a C-arm, for example.

The computer readable medium may be, for example, an electronic, electromagnetic, infrared, optical, or magnetic data storage means. The non-transitory computer readable medium is preferably a non-volatile data storage medium, such as a CD-ROM, a USB data memory stick, and the like.

In an example, the computer program element and/ or computer readable medium according to the third or fourth aspects may be accessible from, or a module of, a CT image analysis software program. For example, an introduction lead angle computation according to the first aspect and its embodiments may be provided as a plug-in software module, or menu option, of an existing preoperative CT image analysis software program.

In an example, the computer program element may be stored, and executed remotely, to the input and output means. For example, the computer program element may reside on a “cloud” server provided by, for example, the Amazon Cloud (TM) service or the Microsoft Azure (TM) service. In an example, a portion of 3D anatomical model data is transmitted to a cloud service at a remote location, where the method of the first aspect or its embodiments may be performed, and the introduction lead angle and other outputs of the first aspect or its embodiments detailed herein may be transmitted back to a user from the cloud service. A computer hosting the computer program element and/or computer readable medium according to the third or fourth aspects can operate in a networked environment using logical connections to other computers on the network (such as via a local area network connection, a wide area network connection, and the like). In particular, 3D anatomical model data may be accessed over a network from a hospital PACS system or other image storage server.

The computer program element of the third aspect, when loaded into a processor 74 and executed, can transform the processor 74 and the overall host computer (for example apparatus 72) from a general-purpose computer into a special-purpose computer customised to specifically facilitate the functionality presented in the aspects and embodiments of this specification. The processor 74 can operate as a finite state machine in response to executable instructions contained within the computer program element discussed herein. The computer program element can therefore transform the processor 74 by specifying how the processor 74 transitions between states, thereby transforming the processor or other hardware elements associated with the processor.

According to a further aspect, there is provided an apparatus configured to model a rotational orientation, relative to a modelled vascular feature of a patient, of a reference point on an interventional device, wherein the portion is configured to support a prosthesis, the apparatus comprising: an input means; a data memory means; a processor means; and - an output means; wherein the input means is configured to obtain 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the interventional device, and to store the 3D anatomical model data in the data memory means; wherein the processor means is configured to load the 3D anatomical model data from the data memory means, and to generate a first rotational orientation of the reference point of the interventional device at a first location of the intervention device on the route of the interventional device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memory means; and wherein the processor means is configured to generate a second rotational orientation of the reference point at a second location of the intervention device on the route of the interventional device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memoiy means.

Reference Numerals ioa Transcarotid entry 36 Intervention device 10b Transcaval entry 37 Tube member toe Transiliac entry 37a Radiopaque element on tube tod Transfemoral entry 40 38 Tip element toe Transaortic entry 38a Radiopaque element on tip tog Subclavian entry 39a-b Stent mounting portions

11 descending aorta 40 Outer tube

12 aortic arch 41 Annular spacer member

13 left subclavian artery 45 42 Guide wire

14 left common carotid artery 43 Sheath

15 brachiocephalic artery 44 Delivery system

16 ascending aorta 45 Stent containing region

17 aortic root 46 Delivery catheter

18 right coronary artery 50 47a Introducer

18a right coronary ostium 47b Introducer alignment reference

19 left coronary artery 47c Distal tube portion 19a left coronary ostium 47d Proximal aperture portion 2oa-c aortic sinuses 48 Proximal portion (handle)

21 aortic root diameter 55 49a Fixed handle portion

22 left coronary height 49b First adjustable portion

23 native leaflets 49c Second adjustable portion

24 LVOT diameter 50a Safety stop

25 Annulus diameter 50b Safety stop body portion

26 Sinus Tube Joint (STJ) 60 50c Turnable ring

27 Centreline 51 Rotational indicator

28a-c Native commissure 52 Introducer abutment portion 29a-c Native valve cusps 53 Luer valve 30 Prosthesis (valve stent) 54 Intervention device rotation

30a Pericardium valve 65 marker 3ia-c Stabilization arches 55 Patient

32 Upper anchor crown Fi Intervention device introduction

33 Lower anchor crown angle 34a-c Attachment elements 56 Frame of reference at the 35a-c Commissural posts 70 introduction location 57 Frame of reference at the 67 Vascular route display deployment location

67a First window

58 Frame of reference of 3D 67b Second window anatomical model data 67c Third window

59 Route of an interventional device 68 Introduction Marker

60 Introduction plane 69 Deployment Marker

61 Deployment plane

72 Apparatus

0 first rotational orientation 73 Input data interface q₂ second rotational orientation 74 Processor

62 A computer implemented method 75 Data memory for preoperative modelling 76 Output data interface

63 obtaining 3D anatomical model

80 Further GUI data 81 Vascular route display

64 obtaining a first rotational 82 Implantation plane display orientation 83 Prosthesis menu

65 generating a second rotational 84 GUI slider orientation

85 Radiopaque marker prediction

66 Graphical user interface

Claims

1. A computer implemented method (62) for preoperative modelling of a rotational orientation of a reference point on an intervention device, relative to a modelled vascular feature of a patient, wherein the method comprises: obtaining (63) 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the intervention device; obtaining (64) a first rotational orientation of the reference point on the intervention device at a first location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data; generating (65) a second rotational orientation of the reference point at a second location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data.

2. The computer implemented method (62) according to claim 1, further comprising: calculating a rotational orientation difference of the reference point between the first location of the intervention device and the second location of the intervention device.

3. The computer implemented method (62) according to claim 2, wherein the rotational orientation difference between the first and second locations is calculated as a vector integral of the route between the first and second locations, and / or based on a quaternion representation of the first and second locations, or using one or more Bezier curves between the first and second locations.

4. The computer implemented method (62) according to claim 3, wherein the rotational orientation difference between the first location of the intervention device and the second location of the intervention device is characterized by the precession of the reference point between the first and second locations.

5. The computer implemented method (62) according to one of claims 1 to 4, wherein the first location defines the rotational location of the reference point in a first plane orthogonal to a tangent of the route at the first location, and wherein the second rotational orientation defines the rotational location of the reference point in a second plane orthogonal to a tangent of the route at the second location.

6. The computer implemented method (62) according to one of claims 1 to 5, further comprising: obtaining a distal end location of the route in the 3D anatomical model data, and wherein the second location is closer to the distal end location of the route, along the route, compared to the first location.

7. The computer implemented method (62) according to one of claims 1 to 5, further comprising: obtaining a distal end location of the route in the 3D anatomical model data, and wherein the second location is further away from the distal end location of the route, along the route, compared to the first location.

8. The computer implemented method (62) according to claim 7, wherein the distal end location of the route in the 3D anatomical model data is a modelled deployment location of a prosthesis from the intervention device.

9. The computer implemented method (62) according to one of the preceding claims, wherein the route in the 3D anatomical model data further comprises a proximal end location.

10. The computer implemented method (62) according to claim 9, wherein the proximal end location of the route within the 3D anatomical model data is a modelled introduction location, into a patient, of the intervention device into the vascular feature.

11. The computer implemented method (62) according to one of the preceding claims, wherein the second location is a representation of the aortic root of the vasculature in the 3D anatomical model data.

12. The computer implemented method (62) according to one of claims 8 to 11, wherein the prosthesis is a self-expanding or balloon-expanding transcatheter valve.

13. The computer implemented method (62) according to one of claims 10 to 12, wherein the route between the modelled introduction location and the modelled deployment location in the 3D anatomical model data models a transfemoral cardiac catheterization route.

14. The computer implemented method (62) according to one of claims 10 to 13, further comprising: receiving input data comprising an intended rotational orientation of the reference point, and/or of the prosthesis, at the modelled deployment location, and calculating output data comprising a first introduction lead angle (FiO of the reference point, and/or the prosthesis, when mounted on the intervention device at the modelled introduction location, wherein the calculation of the first introduction lead angle is based on a first modelled rotation difference of the intervention device between the modelled introduction location and the modelled deployment location.

15. The computer implemented method (62) according to claim 14, wherein the first introduction lead angle (On) is the intended rotational orientation of the reference point, or of the prosthesis, at the modelled deployment location, minus the rotation difference caused by the movement of the intervention device through the vascular feature in between the modelled introduction location and the modelled deployment location.

16. The computer implemented method (62) according to claim 14 or 15, wherein the first introduction lead angle (FiO is defined relative to a plane that is orthogonal to the longitudinal axis of an introducer of the intervention device, wherein the introducer is aligned with the route at the modelled introduction location in the 3D anatomical model data.

17. The computer implemented method (62) according to one of claims 14 to 16, wherein the intended rotational orientation is defined relative to a plane that is orthogonal to a distal portion of the route of the intervention device, wherein the distal portion of the route is inbetween a modelled sinotubular junction and a modelled aortic annulus in the 3D anatomical model data.

18. The computer implemented method (62) according to one of claims 14 to 17, further comprising: modelling a deformation of a portion of the vascular feature in the 3D anatomical model data, caused by an insertion of an introduction device into the route at the modelled introduction location; and calculating a second introduction lead angle (F₁₂) of the prosthesis at the modelled introduction location, wherein the calculation of the second introduction lead angle is based on a second modelled rotation difference of the reference point on the intervention device between the modelled deployment location and the modelled introduction location, accounting for the change in rotation of the intervention device caused by a deformation of the deformed portion of the vascular feature due to the presence of the introduction device.

19. The computer implemented method (62) according to one of claims 14 to 18, further comprising: calculating a third introduction lead angle (F_¾) of the prosthesis, wherein the calculation of the third introduction lead angle is based on a third modelled rotation difference of the reference point on the intervention device dependent on an approach via (i) the left transfemoral artery, or (ii) via the right transfemoral artery, or a trans carotid cardiac catheterization route, a transubclavian cardiac catheterization route, or a venous transcaval cardiac catheterization route.

20. The computer implemented method (62) according to one of claims 14 to 19 further comprising: displaying at least one of the first to third introduction lead angles to a user.

21. The computer implemented method (62) according to claims 14 to 20, further comprising: synthesising a preoperative representation of the modelled deployment location in the patient using the 3D anatomical model data, or a further source of pre operative 3D anatomical model data; displaying, via a user interface, the synthesized representation of the modelled deployment location to a user; and receiving, as input data, via the user interface, the intended rotational orientation of the intervention device at the modelled deployment location from the user based on the position of one, or more, visual markers arranged, by the user, in the visual representation of the modelled deployment location.

22. The computer implemented method (62) according to one of claims 14 to 21, further comprising: identifying, using automatic image recognition, at least one commissure location at the modelled deployment location in the 3D anatomical model data; generating a first candidate rotational orientation of the prosthesis at the modelled deployment location based on the at least one commissure location, and optionally: calculating at least one of the first to third introduction lead angles of the prosthesis based on the first candidate rotational orientation of the prosthesis.

23. The computer implemented method (62) according to one of claims 14 to 22, further comprising: identifying the location of a coronary ostium at the modelled prosthesis deployment location in the 3D anatomical model data using automatic image recognition; generating a second candidate rotational orientation of the prosthesis at the modelled deployment location based on the location of coronary ostia, and optionally: calculating the first introduction lead angle (On) of the prosthesis at the modelled introduction location based on the second candidate rotational orientation of the prosthesis.

24. The computer implemented method (62) according to one of claims 22 or 23, comparing the first candidate rotational orientation of the prosthesis and the second candidate rotational orientation of the prosthesis; and acquiring a third candidate rotational orientation based on the comparison between the first candidate rotational orientation of the prosthesis and the second candidate rotational orientation of the prosthesis, and optionally: calculating the first introduction lead angle (FiO of the prosthesis at the modelled introduction location based on the third candidate rotational orientation of the prosthesis.

25. The computer implemented method (62) according to one of claims 22 to 24, further comprising: displaying, via the display, at least one of the first, second, or third candidate rotational orientations of the prosthesis at the modelled deployment location in the modelled implantation plane to a user.

26. The computer implemented method (62) according to one of the preceding claims, wherein the route of the intervention device in the vascular feature is (i) the centre line of the vascular feature, or (ii) an interpolated route in the vascular feature in which the route deviates from the centre line of the vascular feature based on the radius of bends in the vascular feature.

27. The computer implemented method (62) according to one of the preceding claims, further comprising: generating a simulated image and/or image sequence illustrating a simulated rotation of the prosthesis as it approaches the modelled prosthesis deployment location, wherein the simulated image and/or image sequence optionally provide a simulated representation of one or more radiopaque markers of the prosthesis and/ or intervention device.

28. The computer implemented method (62) according to one of the preceding claims, wherein a portion of the route inside the vascular feature in the 3D anatomical model data models one of: a transfemoral cardiac catheterization route, a trans carotid cardiac catheterization route, a transubclavian cardiac catheterization route, or a venous transclavial cardiac catheterization route.

29. The computer implemented method (62) according to one of the preceding claims, wherein the prosthesis comprises a structure that repeats three times around a circumference of the prosthesis such that the prosthesis has 3-fold symmetry in the circumferential direction, or wherein the rotational orientation is an orientation with respect to the 120 degree symmetry of the prosthesis.

30. The computer implemented method (62) according to one of claims 14 to 29, wherein the first introduction lead angle (On) is computed to improve the probability that the prosthesis is deployed at an optimal deployment rotation in the implantation plane.

31. An apparatus (72) configured to preoperatively model a rotational orientation of a reference point on an intervention device, relative to a modelled vascular feature of a patient, wherein the apparatus comprises: an input data interface (73); a data memory (75); a processor (74); and an output data interface (76); the input data interface (73) is configured to obtain 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the intervention device, and to store the 3D anatomical model data in the data memory; the processor (74) is configured to load the 3D anatomical model data from the data memory, and to obtain a first rotational orientation of the reference point on the intervention device at a first location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data; and the processor (74) is configured to generate a second rotational orientation of the mounting portion at a second location of the intervention device on the route of the intervention device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memoiy.

32. The apparatus (72) according to claim 31, wherein the processor (74) is further configured to perform the steps of the method according to one of claims 2 to 30.

33. A computer program element for controlling an apparatus according to one of claims 31 or 32 which, when executed by a processing unit, is configured to carry out the method of one of claims 1 to 30.

34. A non-transitory computer readable medium having stored the computer program element according to claim 33.

35. An apparatus configured to model a rotational orientation, relative to a modelled vascular feature of a patient, of a reference point on an interventional device, wherein the portion is configured to support a prosthesis, the apparatus comprising: an input means; a data memory means; a processor means; and an output means; wherein the input means is configured to obtain 3D anatomical model data describing at least a portion of a vascular feature of a patient, wherein the vascular feature encloses a route of the interventional device, and to store the 3D anatomical model data in the data memory means; wherein the processor means is configured to load the 3D anatomical model data from the data memory means, and to generate a first rotational orientation of the reference point of the interventional device at a first location of the intervention device on the route of the interventional device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memory means; and wherein the processor means is configured to generate a second rotational orientation of the reference point at a second location of the intervention device on the route of the interventional device inside the vascular feature of the 3D anatomical model data, and to store the first rotational orientation in the data memory means.