# US 10,441,164 B1 · Correction of decorrelation tail artifacts in a whole OCT-A volume

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- Number: US 10,441,164 B1
- Document ID: US10441164B1
- Status: Granted
- Kind: B1
- Application number: 15/914,933
- Filed: 2018-03-07
- Granted: 2019-10-15
- Earliest claimed: 2017-03-09
- Assignees: Carl Zeiss Meditec AG
- Applicants: Carl Zeiss Meditec, Inc.
- Inventors: Luis De Sisternes; Homayoun Bagherinia
- Web page: https://patentgrep.com/patent/US10441164B1

## CPC

- G16H 40/67: for remote operation
- A61B 3/102: {for optical coherence tomography [OCT]}
- A61B 3/1233: {for measuring blood flow, e.g. at the retina}
- A61B 3/1241: {specially adapted for observation of ocular blood flow, e.g. by fluorescein angiography}
- A61B 5/0022: {Monitoring a patient using a global network, e.g. telephone networks, internet}
- A61B 5/0066: {Optical coherence imaging}
- A61B 5/1495: Calibrating or testing of in-vivo probes
- A61B 5/7207: {of noise induced by motion artifacts}
- A61B 5/7253: {characterised by using transforms}
- G06T 5/00: Image enhancement or restoration
- A61B 3/0025: {characterised by electronic signal processing, e.g. eye models}
- A61B 5/02007: {Evaluating blood vessel condition, e.g. elasticity, compliance}
- G06T 7/0012: {Biomedical image inspection}
- G06T 2207/10028: Range image; Depth image; 3D point clouds
- G06T 2207/10101: Optical tomography; Optical coherence tomography [OCT]
- G06T 2207/20182: Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering
- G06T 2207/30041: Eye; Retina; Ophthalmic
- G06T 2207/30104: Vascular flow; Blood flow; Perfusion
- G06V 10/30: Noise filtering
- G06V 2201/03: Recognition of patterns in medical or anatomical images
- G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING

## Abstract

A method and system for correction of decorrelation tail artifacts in optical coherence tomography (OCT) angiography volumetric data defines a movable target subvolume within the OCT-A volumetric data. The target subvolume is axially moveable within the OCT-A volumetric data in discrete axial steps. At each axial step, a reference subvolume corresponding to a depth location in the OCT A volumetric data is defined axially offset from the target subvolume. The reference subvolume may be defined within the OCT A volumetric data, or defined within a different (previously corrected) OCT-A volume. Irrespective, corrected OCT-A data that corrects for decorrelation tail artifacts in the target subvolume is defined using information in the reference subvolume and information in the target subvolume.

## Claims

### Claim 1

A method for correcting decorrelation tail artifacts in optical coherence tomography (OCT) angiography volumetric data of an eye, said method comprising:
collecting three dimensional OCT data of the eye using an OCT system;
calculating motion contrast information in the three dimensional OCT data using an OCT angiography (OCT-A) processing technique to obtain the OCT-A volumetric data containing the decorrelation tail artifacts;
defining a target subvolume within the OCT-A volumetric data, the target subvolume having an axial depth and being axially moveable within the OCT-A volumetric data;
moving the target subvolume in discrete axial steps within the OCT-A volumetric data, and at each axial step:
(a) defining a reference subvolume corresponding to a depth location in the OCT-A volumetric data axially offset from the target subvolume;
(b) defining corrected OCT-A data that corrects for decorrelation tail artifacts in the target subvolume using information in the reference subvolume and information in the target subvolume; and
displaying or storing the corrected OCT-A data or a further analysis thereof.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein the reference subvolume contains corrected OCT-A data from a previous axial step.

### Claim 3 (depends on 1)

The method as recited in claim 1, wherein the step of defining corrected OCT-A data comprises:
using an inverse calculation, determining a corrected subvolume that can be mixed with the reference subvolume to generate the target subvolume, said corrected subvolume being said corrected OCT-A data.

### Claim 4 (depends on 3)

The method as recited in claim 3, wherein the inverse calculation uses one or more of an additive mixing, a multiplicative mixing, and a combination of the two for determining the corrected subvolume that can be mixed with the reference subvolume to generate the target subvolume.

### Claim 5 (depends on 1)

The method as recited in claim 1, further comprising at each axial step:
(c) determining a positional correspondence between the defined corrected OCT-A data and the OCT-A volumetric data within the target subvolume;
(d) updating OCT-A volumetric data within the target subvolume based on its corresponding corrected OCT-A data;
wherein the reference subvolume is defined within the OCT-A volumetric data.

### Claim 6 (depends on 1)

The method as recited in claim 1, further comprising:
initializing an empty volume to serve as a corrected OCT-A volume; and
at each axial step:
(c) updating the corrected OCT-A volume with the defined corrected OCT-A data at an updated depth location within the corrected OCT-A volume, and mapping the updated depth location with the corrected OCT-A volume to the current depth location of the target subvolume within the OCT-A volumetric data.

### Claim 7 (depends on 6)

The method as recited in claim 6, wherein the reference subvolume is defined within the corrected OCT-A volume.

### Claim 8 (depends on 1)

The method as recited in claim 1, wherein step (b) of defining corrected OCT-A data includes:
projecting the target subvolume to a corresponding target map and projecting the reference subvolume to a corresponding reference map using a projection technique; and
correcting decorrelation tail artifacts in the target map, to define a corrected target map, using information in the reference map and in the target map;
wherein the defining of the corrected OCT-A data is based on the corrected target map.

### Claim 9 (depends on 8)

The method as recited in claim 8, wherein defining of the corrected OCT-A data further includes adding weighted values of the corrected target map to locations in the corrected OCT-A data indicated by the target subvolume in a pixel by pixel manner.

### Claim 10 (depends on 8)

The method as recited in claim 8, wherein the projection technique is axial summation of data corresponding to a region indicated by the target subvolume for the target map and axial summation of data corresponding to a region indicated by the reference subvolume for the reference map.

### Claim 11 (depends on 1)

The method as recited in claim 1, further comprising:
segmenting the corrected OCT-A data to define a segmented output identifying two or more retinal layer boundaries located at different depth locations in the eye;
generating an optimal slab from the segmented output, said optimal slab defined by an upper layer boundary and a lower layer boundary, wherein the optimal slab visualizes a particular pathology in the eye; and
displaying or storing the optimal slab or a further analysis thereof.

### Claim 12 (depends on 11)

The method as recited in claim 11, wherein the pathology is choroidal neovascularization (CNV).

### Claim 13 (depends on 11)

The method as recited in claim 11, wherein the upper layer boundary is outer plexiform layer (OPL) and the lower layer boundary is retinal pigment epithelium (RPE).

### Claim 14 (depends on 11)

The method as recited in claim 11, wherein the segmented output is free from segmentation errors.

### Claim 15 (depends on 1)

The method as recited in claim 1, wherein the three dimensional OCT data contains multiple B-scans taken at approximately the same set of transverse locations on a particular region of the eye, and the target subvolume includes one or more A-scans.

### Claim 16 (depends on 1)

The method as recited in claim 1, wherein the OCT-A processing technique is one or more of an intensity-based processing technique, a phase-based processing technique, and a complex-based processing technique.

### Claim 17 (depends on 1)

The method as recited in claim 1, wherein the axial depth of the target subvolume is variable at each axial step.

### Claim 18 (depends on 1)

The method as recited in claim 1, wherein an axial distance that the target subvolume moves between discrete axial steps is variable.

### Claim 19 (depends on 1)

The method of as recited in claim 1, wherein a current axial position of the target subvolume is define as k*S, where k tracks axial movements of the target subvolume and S is a depth displacement multiplier for each axial movement of the target subvolume.

### Claim 20 (depends on 19)

The method as recited in claim 19, wherein a current axial position of the reference subvolume corresponds to a depth position in the OCT-A volumetric data defined as (k*S−T), where T is a correction margin that defines the axial offset from the target subvolume, and T is variable at each axial step.