Method for determining the final length of stents before the positioning thereof
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Publication Number
US-10176566-B2
Publication Date
2019-01-08
Expiration Date
Abstract
The invention relates to a new method for determining the change in length of a stent which will occur after it has been implanted inside a vascular structure. Said determining process is carried out based on the relationship between said change in length and the morphological characteristics of the vascular structure of interest.
Core Innovation
The invention relates to a computer-implemented method for determining the final length of a stent before it is positioned in a vascular structure. The method obtains an angiographic three-dimensional image of the vascular structure, traces a centreline of the vascular structure in the three-dimensional image, defines an exact location of an initial point at which the stent will be positioned, and divides the centreline into small segments.
For each segment starting from the initial point, the computer measures descriptor parameters of a morphology of the vascular structure. The computer calculates a length of the stent for the segment using an indicator ratio of the change in length of the stent as a function of local morphology of the vascular structure, and the segment-based calculated length is subtracted from the nominal length of the stent to obtain a new nominal length.
The procedure is repeated for a contiguous segment when the new nominal length is different from 0, and when the new nominal length is 0, the distances of each segment are added together to obtain the final length of the stent after positioning. The indicator ratio is experimentally obtained, mathematically modelled, or provided by the stent manufacturer, and the morphology descriptor parameters include radii, cross-sectional geometry descriptors, curvature and torsion.
Claims Coverage
The partial content identifies one independent claim. The independent claim covers a computer-implemented workflow that derives a stent final length from angiographic 3D imaging by tracing and segmenting a vascular centreline, measuring local vascular morphology descriptors per segment, and iteratively adjusting nominal stent length via an indicator ratio relating stent length change to local morphology. Dependent claims refine how the indicator ratio is obtained and which morphology descriptor parameters are used.
Angiographic 3D centreline tracing and segmenting for pre-positioning stent length
Obtaining an angiographic three-dimensional image of the vascular structure, tracing a centreline in the three-dimensional image, defining an exact location of an initial point for stent positioning, and dividing the centreline into small segments.
Segment-wise morphology measurement on angiographic 3D image
Measuring, by the computer, on the three-dimensional image descriptor parameters of a morphology of the vascular structure for a first segment that starts from the initial point.
Indicator-ratio based stent length calculation from local morphology
Calculating, by the computer, a length of the stent for the first segment using an indicator ratio of the change in length of the stent as a function of local morphology of the vascular structure.
Iterative nominal length updating and final length summation
Subtracting the calculated segment length from the nominal length of the stent to obtain a new nominal length, repeating measurement and calculation for a contiguous segment while the new nominal length is different from 0, and when the new nominal length is 0 adding together the distances of each segment to obtain the final length after positioning.
Indicator ratio obtained experimentally
Determining an indicator ratio based on the change in length of a stent using experimental obtaining.
Indicator ratio determined by mathematical modeling
Determining an indicator ratio based on the change in length of a stent using mathematical modelling.
Indicator ratio provided by stent manufacturer
Using an indicator ratio of the change in length of the stent provided by the manufacturer of the stent.
Use of specified vascular morphology descriptor parameters
Characterizing vascular morphology using descriptor parameters including radii and cross-sectional geometry descriptors, and including curvature and torsion values.
Overall, the claims coverage centers on an angiographic 3D image-driven, segment-wise, indicator-ratio calculation of how stent length changes with local vascular morphology, coupled to an iterative nominal-length subtraction process until the final segment distances are summed; dependent claims narrow how the indicator ratio is sourced and specify classes of vascular morphology descriptor parameters.
Stated Advantages
Detecting poor apposition/occlusion/migration risk regions.
Documented Applications
Neurointerventional radiologist planning using an example with patient-specific vascular geometry and comparisons of computed versus nominal length.
Use in phantom/tubes experiments for braided and unbraided stents.
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