CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2016/071908, filed on Sep. 15, 2016, which claims the benefit of International European Application No. EP15185452.8, filed on Sep. 16, 2015. These applications are hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to an apparatus, a system and method for characterization of vessels and for vessel modeling.

BACKGROUND OF THE INVENTION

A typical technique for identifying stenotic regions in a blood vessel is using angiography, whereas the functional impact of the stenosis is quantified with the fractional flow reserve (FFR) method. FFR is calculated from the ratio of pressures at the distal and proximal ends of the stenosis, measured with a sensor positioned at the tip of a wire. According to the FFR value the severity of the stenosis is established, specifically whether the stenosis limits blood flow within the vessel to an extent that treatment is required. Common treatment options include angioplasty, stenting or bypass.

Angiography, a fluoroscopy imaging technique in conjunction with radio-opaque contrast agents, can be used to visualize the vasculature of a patient.

U.S. Pat. No. 4,875,165 A describes a method for determination of three-dimensional structure in biplane angiography, including determining the distances of perpendicular lines from the focal spots of respective x-ray sources to respective image planes and defining the origin of each biplane image as the point of intersection with the perpendicular line thereto, obtaining two biplane digital images at arbitrary orientations with respect to an object, identifying at least eight points in both images which correspond to respective points in the object, determining the image coordinates of the eight identified object points in the respective biplane unknowns based on the image coordinates of the object points and based on the known focal spot to image plane distances for the two biplane images; solving the linear equations to yield the eight unknowns, which represent the fundamental geometric parameters of the biplane imaging system; using the fundamental parameters to calculate the three-dimensional positions of the object points identified in the biplane images; and determination of the three-dimensional positions of the vessel segments between the object points.

WO 2013001388 A1 discloses a method, and system for providing a live 3D image of a body lumen. The 3D shape of a flexible surgical tool in the body lumen is determined using optical shape sensing. An x-ray image is taken of the body lumen, with at least one of the body lumen and the surgical tool being radiopaque. The determined 3D surgical tool shape is registered to the x-ray image.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an apparatus for a simpler and more intuitive characterization of vessels of living beings.

According to a first aspect of the invention, this object is realized by an apparatus for characterizing a vessel of a living being, the apparatus comprising:a processor for processing measurement information, wherein the apparatus is configured to be coupled to:a tracking unit for measuring temporal location information of a trackable instrument in a vessel,an imaging unit for generating morphological projection information of the vessel;the processor is configured to:derive a first diameter of the vessel from the morphological projection information corresponding to a first temporal location of a distal portion of the instrument,derive a second diameter of the vessel from the morphological projection information corresponding to a second temporal location of the distal portion of the instrument, andassign the first and second diameters of the vessel in a three-dimensional morphological model of the vessel at two locations defined by a relative position between the first and second temporal locations of the distal portion of the instrument.

Characterization of vessels is improved in that the diameter of the vessel is provided in a three-dimensional model of the vessel morphology, based on computation of the diameter from morphological projection information combined with the temporal location information of the tracked device. A major benefit is that a single angiographic projection is sufficient for construction of the three-dimensional morphological vessel model, and that the three-dimensional model is generated as the distal portion (e.g. tip or a radiopaque marker) of the instrument moves within the vessel lumen. The three-dimensional model is augmented with the withdrawal of the instrument, therefore a three-dimensional model is presented to the user only for the relevant segment of the vessel through which the distal portion of the instrument has been maneuvered, making the information presented to the user simpler and the interpretation of the information more intuitive. In an embodiment of the apparatus, the temporal location information of the instrument processed by the processor is derived from electromagnetic signals. Electromagnetic tracking of instruments is one of the typical localization techniques, whereby an electromagnetic field is detected by an electromagnetic sensor integrated into the instrument, and the temporal location of the senor in the electromagnetic field is derived from the strength of the signal.

In an embodiment of the apparatus, the temporal location information of the instrument processed by the processor is derived from laser radiation. Optical shape sensing is a technology that uses reflections of laser radiation from multiple optical fibers or from a multi-core optical fiber integrated into an instrument to measure local strains to which the instrument is exposed. The shape of the optical fibers, hence that of the instrument, is derived by processing optical reflection signals from within the optical fibers, received by a detector. The advantage of optical shape sensing over electromagnetic tracking is that the full three-dimensional shape of the instrument is known at all instances, whereas with electromagnetic tracking only the discrete positions of the electromagnetic sensors integrated into the instrument can be derived.

In an embodiment of the apparatus, the first and second temporal location information indicative for the location of the instrument in the vessel originate at same phase of a cyclical cardiac motion. Assigning the first and second diameters of the vessel in a three-dimensional morphological model based on gating to the phase of the cyclical cardiac and/or respiratory motion is critical in instances where real-time assessment is carried out on the condition of coronary arteries, with significant motion due to heart beat and respiration.

In an embodiment the apparatus further comprises a display, and the processor is configured to render a graphical representation of the three-dimensional morphological model with the assigned first and second diameters on the display. Visual aspect of the three-dimensional vessel model supports assessment of the condition of the vasculature, since stenotic regions are represented by a significant narrowing of the vessel, whereas aneurysms have a bulging aspect.

According to a second aspect of the invention a system comprises:the apparatus for characterizing a vessel of a living being,the trackable instrument for introduction into the vessel of the living being,the tracking unit for measuring temporal location information of the instrument in the vessel,the imaging unit for generating morphological projection information of the vessel. The trackable instrument comprises at least an electromagnetic sensor for sensing an electromagnetic field generated by the tracking unit, or at least an optical fiber for sensing strain to which the instrument is exposed when the tracking unit transmits and receives laser radiation from within the at least an optical fiber. A radiological imaging unit such as a fluoroscopy system or a system used for x-ray computed tomography, capable of providing radiographic projection, can be used for acquiring the morphological information of vessels by angiography. Other imaging techniques suitable for acquiring morphological information of vessels may however be used, such as ultrasound imaging, or magnetic resonance imaging. The tracking unit may be integrated into the imaging unit. The trackable instrument may comprise markers traceable with the imaging unit used for acquiring morphological information of the vessels. The markers on the instrument are recognizable with the respective imaging modalities, for instance ultrasound reflecting or absorbing markers in ultrasound imaging.

In an embodiment of the system, the trackable instrument comprises a sensor for measuring physiological information, and the processor is configured to assign at least a first physiological information to the three-dimensional morphological model of the vessel at the location defined by the first temporal location of the instrument. In an alternative embodiment, the processor is further configured to assign at least a second physiological information to the three-dimensional morphological model of the vessel at the location defined by the second temporal location of the instrument. Assigning physiological information to the three-dimensional model supports the physician in assessment of vessel condition, for instance change in visual aspect of the model due to narrowing or broadening vessel branch, by confirmation of a variation of pressure, FFR, blood flow velocity or blood flow resistance values.

According to further aspect of the invention a method for characterizing a vessel of a living being comprises:introducing a trackable instrument into the vessel,measuring temporal location information of the instrument in the vessel,generating morphological projection information of the vessel,deriving a first diameter of the vessel from the morphological projection information corresponding to a first temporal location of a distal portion of the instrument,deriving a second diameter of the vessel from the morphological projection information corresponding to a second temporal location of the distal portion of the instrument, andassigning the first and second diameters of the vessel in a three-dimensional morphological model of the vessel at two locations defined by a relative position between the first and second temporal locations of the distal portion of the instrument.

In an embodiment of the methodderiving the first and second diameters and measuring the first and second temporal locations of the instrument are performed for consecutive phases of a cyclical motion, andassigning the first and second diameters of the vessel in the three-dimensional morphological model of the vessel at two locations defined by the relative position between the first and second temporal locations of the distal portion of the instrument is performed for respective consecutive phases of the cyclical motion.

In an embodiment, the method further comprises the step of rendering a graphical representation of the three-dimensional morphological model on a display. The visual representation of the three-dimensional morphological model enables rapid assessment of various structural and functional nonconformities, such as vessel stenosis and/or presence of aneurysms.

Additional aspects and advantages of the invention will become more apparent from the following detailed description, which may be best understood with reference to and in conjunction with the accompanying drawings.

