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EP-3923818-B1 - ULTRASOUND ANALYSIS METHOD AND DEVICE

EP3923818B1EP 3923818 B1EP3923818 B1EP 3923818B1EP-3923818-B1

Inventors

  • SCHMEITZ, HAROLD, AGNES, WILHELMUS
  • DE BRUIJN, FREDERIK, JAN
  • LUCASSEN, GERHARDUS, WILHELMUS
  • AUVRAY, Vincent, Maurice, André

Dates

Publication Date
20260513
Application Date
20200214

Claims (15)

  1. An ultrasound data analysis method (30) performed by an ultrasound data processor, the method for analyzing ultrasound data captured by an intravascular ultrasound, IVUS, device, the method comprising: receiving (32) a plurality of frames of ultrasound data captured by an IVUS device, each frame comprising data for a plurality of radial scan lines, each radial scan line corresponding to an acoustic signal received along a different rotational angle (φ) with respect to a longitudinal axis (A - A') of the device; characterized in that the method further comprises processing (34) the ultrasound data for each radial scan line in each frame, to reduce the data for each line to a single representative data value for the line; deriving (36) from the set of representative data values a set of probability values corresponding to probability of presence of an intravascular object at least within each frame; determining (38) a region within the ultrasound data occupied by the intravascular object based on the probability values.
  2. The method (30) as claimed in claim 1, wherein determining (38) the region occupied by the intravascular object comprises identifying a consecutive subset of frames of the data occupied by the intravascular object, and/or identifying a consecutive subset of radial lines occupied by the intravascular object.
  3. The method (30) as claimed in claim 1 or 2, wherein determining (38) the region occupied by the intravascular object comprises identifying a consecutive subset of frames for which the derived probability values are each higher than a pre-defined threshold.
  4. The method (30) as claimed in any of claims 1 - 3, wherein determining (38) the region occupied by the intravascular object comprises detecting edges of the intravascular object.
  5. The method (30) as claimed in any of claims 1 - 4, wherein determining (38) the region within the data occupied by the intravascular object comprises testing a plurality of trial regions within the data, the testing comprising calculating for each trial region a difference between the set of probability values for the trial region and an equivalent set of probability values representative of exact occupation of the region by an object.
  6. The method (30) as claimed in claim 5, wherein: the testing comprises calculating a cost function, the cost function comprising, as at least one additive term, the sum of said set of difference values of claim 5 for the whole set of frames across the trial region; or the testing comprises calculating a cost function, the cost function comprising, as at least one additive term, the sum of said set of difference values of claim 5 for the whole set of frames across the trial region, and wherein the cost function comprises, as one or more further additive terms, a sum of the probability values for consecutive sets of frames on one or both sides of the trial region.
  7. The method (30) as claimed in any of claims 1 - 6, wherein the representative values are representative of a maximum intensity value of the respective radial line.
  8. The method (30) as claimed in claim 7, wherein the method further comprises determining a set of index values representative of a location of each maximum intensity value along each radial line.
  9. The method (30) as claimed in any of claims 1 - 8, wherein the method comprises generating a plot or map of the representative values, for example a plot or map representing the values plotted against frame number and/or radial line number.
  10. The method (30) as claimed in any of claims 1 - 9, wherein deriving (36) from the set of representative data values a set of probability values comprises detecting within the set of representative values one or more characteristic patterns characteristic of presence of an object.
  11. The method (30) as claimed in any of claims 1 - 10, wherein deriving (36) from the set of representative data values a set of probability values comprises use of a classifier algorithm, and preferably wherein the classifier algorithm comprises a machine learning algorithm, for example a neural network.
  12. The method (30) as claimed in any of claims 1 - 11, wherein each frame corresponds to a different longitudinal location along a lumen.
  13. An ultrasound data processor for analyzing ultrasound data captured by an IVUS device, the processor adapted to: receive a plurality of frames of ultrasound data captured by the IVUS device, each frame comprising data for a plurality of radial scan lines, each radial scan line corresponding to an acoustic signal received along a different rotational angle (φ) with respect to a longitudinal axis (A - A') of the device; characterized in that the processor is further adapted to process the ultrasound data for each radial scan line in each frame, to reduce the data for each line to a single representative data value for the line; derive from the set of representative data values a set of probability values corresponding to probability of presence of an intravascular object at least within each frame; determine a region within the ultrasound data occupied by an intravascular object based on the probability values.
  14. An ultrasound system comprising: an intravascular ultrasound, IVUS, device (12) for capturing ultrasound data within a blood vessel lumen along a plurality of different radial scan lines; and an ultrasound data processor as claimed in claim 14, operably coupled with the intravascular ultrasound device, and configured to receive ultrasound data captured by the IVUS device.
  15. One or more computer programs comprising processor readable code which, when executed by the ultrasound data processor, cause execution of the ultrasound data analysis method of any one of claims 1 to 12.

Description

FIELD OF THE INVENTION The present invention relates to an ultrasound processing method and device, in particular for detecting the presence of objects in intravascular ultrasound data. BACKGROUND OF THE INVENTION Intravascular Ultrasound (IVUS) imaging is a valuable technique to obtain internal images of the cardiovascular system of a patient, such as the patient's arteries or heart. The IVUS images may assist in assessing a condition of the cardiovascular system, such as for example in detecting and quantifying the size of a stenosis, the build-up of plaque, or in assisting with the positioning of a medical implant such as a stent. In order to obtain the IVUS images, a minimally invasive medical device such as a catheter or guidewire fitted with an ultrasound probe or set of ultrasound transducers, e.g. at its tip, is inserted into the cardiovascular system of the patient, typically into an artery, after which the IVUS images are captured at regular intervals whilst pulling back the minimally invasive medical device. In this manner, captured cross-sectional IVUS images of the cardiovascular system can assist in providing valuable insights into the condition of the cardiovascular system along its imaged length. IVUS devices e.g. catheters incorporate one or more ultrasound transducers for imaging the vessel lumen. The transducers emit and receive ultrasonic energy in order to create an image of the vessel of interest. Ultrasonic waves are partially reflected by discontinuities arising from tissue structures such as the various layers of the vessel wall, red blood cells, and other features of interest, including artificial objects implanted into the vessel. Echoes from the reflected waves are received by a transducer and passed to an IVUS imaging system, which may for instance be connected to the IVUS catheter by way of a patient interface module termed a "PIM". The imaging system processes the received ultrasound signals to produce e.g. a cross-sectional image of the vessel. Two types of IVUS catheters are commonly in use today: rotational and solid-state. For a typical rotational IVUS catheter, one or more ultrasound transducer elements are located at the tip of a flexible driveshaft that spins inside a sheath inserted into the vessel of interest. In contrast, solid-state IVUS catheters carry an ultrasound scanner assembly that includes an array of ultrasound transducers, such as a one-dimensional or two-dimensional array, distributed around the circumference of the device and connected to a set of transducer control circuits. The array and its corresponding circuity are often referred to as the imaging core or scanner of the IVUS device. For traditional image generation, transducer control circuits may select individual or groups of transducers of the array for transmitting an ultrasound pulse and/ or for receiving the echo signal. By stepping through a sequence of transmitter-receiver pairs, sequentially around the circumference of the device, the IVUS system can synthesize the effect of a mechanically rotating transducer element but without moving parts. Since there is no rotating mechanical element, the transducer array can be placed in direct contact with the blood and vessel tissue with minimal risk of vessel trauma. The data captured at each of the sequential positions around the device circumference are often referred to a radial scan lines. The common way to visualize a full pullback (pullback of the IVUS device along the longitudinal axis of a vessel lumen) IVUS dataset is to display one or more cross-sectional views along the pullback (longitudinal) axis. A cross-sectional view means a representation of the data of a single radial line, along the whole longitudinal pull-back distance. This is illustrated in Fig. 1. Fig. 1 schematically illustrates an example IVUS device 12 having an elongate device body 14. The elongate device body extends along a longitudinal axis, the direction of which is indicated by line A-A' in Fig. 1. The example IVUS device is shown comprising an array 16 of outward-facing ultrasound transducer elements 20, extending circumferentially around the device. Fig. 1 illustrates activation of one transducer element to generate a single radial acoustic signal line 24 along a particular azimuth angle, φ, directionality, i.e. along a particular rotational angle φ around the device. The single radial signal line 24 captures a single radial line of ultrasound data. Multiple radial signal lines together form a full cross-sectional IVUS image 25. In Fig. 1, trajectories of two example radial lines, a1 and a2, are schematically illustrated. The corresponding trajectories of the lines within the full IVUS scan image 25 are also shown. Although a single transducer element is shown as generating each radial line, in practice, each radial scan line may be generated using a subset of transducer elements (to enable beamforming to be used to focus an acoustic transmission and reflection alon