# US 9,750,403 B2 · Retinal movement tracking in optical coherence tomography

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- Number: US 9,750,403 B2
- Document ID: US9750403B2
- Status: Granted
- Kind: B2
- Application number: 14/519,983
- Filed: 2014-10-21
- Published: 2015-04-23
- Granted: 2017-09-05
- Earliest claimed: 2013-10-23
- Assignees: Canon Kabushiki Kaisha
- Applicants: Canon Kabushiki Kaisha
- Inventors: Slawomir Orlowski; Tomasz Dziubak; Jakub Szatkowski; Pawel Dalasinski; Maciej Pańkowiec
- Web page: https://patentgrep.com/patent/US9750403B2

## CPC

- A61B 3/102: {for optical coherence tomography [OCT]}
- A61B 3/0025: {characterised by electronic signal processing, e.g. eye models}
- A61B 3/10: Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
- A61B 3/113: for determining or recording eye movement
- A61B 3/1225: {using coherent radiation}
- A61B 3/1233: {for measuring blood flow, e.g. at the retina}
- G06T 7/0016: {involving temporal comparison}
- G06T 7/246: using feature-based methods, e.g. the tracking of corners or segments
- G06T 7/337: {involving reference images or patches}
- G06T 7/74: {involving reference images or patches}
- G06T 2207/10101: Optical tomography; Optical coherence tomography [OCT]
- G06T 2207/30041: Eye; Retina; Ophthalmic
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

The present invention defines a method of correcting for eye movement during optical coherence tomography imaging. The method includes imaging (by scanning) a fundus of an eye to obtain a fundus image (for example, using an SLO); scanning the fundus to obtain a plurality of tomographic images (for example, using OCT); determining, at predetermined intervals, an alignment of the tomographic images with respect to the fundus image, and, if it is determined that there is a misalignment, determining the number of tomographic images that have been scanned in the predetermined interval since the previous alignment determination; determining the offset by which the tomographic images are misaligned; applying the offset to the next tomographic image to be scanned and rescanning the determined number of tomographic images that were scanned during the interval between misalignment being determined and offset being applied.

## Claims

### Claim 1

A method comprising:
imaging a fundus of an eye to obtain a plurality of fundus images;
imaging the fundus to obtain a plurality of tomographic images;
determining a fundus movement of the eyes based on the plurality of fundus image;
tracking the determined fundus movement of the fundus;
determining the number and positions of tomographic images imaged during a time including a time during which the fundus movement cannot be tracked;
re-imaging the determined number of tomographic images at the determined positions.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the imaging of the fundus to obtain a fundus image and the imaging of the fundus to obtain a tomographic image have synchronised starts.

### Claim 3 (depends on 1)

A method according to claim 1, wherein the time during which the fundus movement cannot be tracked includes the amount of time required to determine whether there is a misalignment in a tomographic image.

### Claim 4 (depends on 1)

A method according to claim 1, wherein the time during which the fundus movement cannot be tracked includes a feedback delay for the tracking.

### Claim 5 (depends on 1)

A method according to claim 1, wherein the step of determining the fundus movement comprises comparing two fundus images.

### Claim 6 (depends on 1)

A method according to claim 1, further comprising replacing the tomographic image imaged in the interval with the re-imaged tomographic images.

### Claim 7 (depends on 1)

A method according to claim 1, further comprising outputting a fail flag if the fundus movement cannot be tracked.

### Claim 8 (depends on 1)

A method according to claim 1, wherein the fundus image is a 2-dimensional image.

### Claim 9 (depends on 1)

A method according to claim 1, wherein the fundus image is an SLO (scanning laser ophthalmoscope) image.

### Claim 10 (depends on 1)

A method according to claim 1, wherein the tomographic images are b-scans of an OCT apparatus.

### Claim 11

An OCT apparatus for use with a processing apparatus, the OCT apparatus comprising:
an imaging unit operable to image a fundus of an eye to obtain a plurality of tomographic images;
a communication unit for receiving a number and positions of tomographic images that were imaged during a time period including a time during which the fundus movement cannot be tracked based on a plurality of the fundus images by the processing apparatus; and
a processor for re-imaging the tomographic images corresponding to the number and the positions of tomographic images received by the communication unit and for replacing the tomographic images that were imaged during the time including the time during which the fundus movement cannot be tracked based on the plurality images by the processing apparatus.

### Claim 12 (depends on 11)

An OCT apparatus according to claim 11, further comprising:
a synchronisation unit for synchronising the start of the imaging of a tomographic image within a region of the fundus by the imaging unit with a start of imaging the same region of the fundus by a fundus imaging apparatus.

### Claim 13 (depends on 11)

An OCT apparatus according to claim 11, further comprising:
a correction unit for correcting a tomographic image position according to the offset received from the processing apparatus.

### Claim 14

A system for correcting for eye movement during imaging of the eye comprising:
a processing apparatus comprising:
an offset measuring unit operable to compare the alignment of a tomographic image imaged by the OCT apparatus with a fundus of an eye to be examined by determining an alignment of the tomographic image compared to a fundus image imaged by the fundus imaging apparatus and by measuring an offset between the fundus image position and a reference fundus position;
a correction unit operable to correct the position of a subsequently imaged tomographic image based on the offset measured by the offset measuring unit;
a calculating unit operable to calculate the number of tomographic images that were imaged while the offset measuring unit was measuring the offset; and
a communication unit for transmitting to the OCT apparatus the number of tomographic images calculated by the calculating unit;
an OCT apparatus comprising:
an imaging unit operable to image a fundus of an eye to obtain a plurality of tomographic images;
a communication unit for receiving a number of tomographic images that were imaged while the processing apparatus calculated an offset of a tomographic image position with respect to the fundus; and
a processor for re-imaging the tomographic images corresponding to the number of tomographic images received by the communication unit and replacing the tomographic images that were imaged while the processing apparatus calculated an offset of a tomographic image position with respect to the fundus with the re-imaged tomographic images; and
a fundus imaging apparatus comprising: an imaging unit for imaging a fundus of an eye to obtain a fundus image; and
a synchronisation unit for synchronising the start of the imaging of a region of the fundus by the imaging unit with a start of imaging of a tomographic image within the same region of the fundus by an OCT apparatus.

### Claim 15 (depends on 14)

A system according to claim 14, further comprising a synchronisation controller for controlling a synchronisation of the imaging of the fundus by the fundus imaging apparatus and the imaging of the tomographic image by the OCT apparatus.

### Claim 16

A non-transitory storage medium containing a computer program which, when run on a computer, causes the computer to perform the following steps:
imaging a fundus of an eye to obtain a plurality of fundus image;
imaging the fundus to obtain a plurality of tomographic images;
determining a fundus movement of the eye based the plurality of fundus images, and,
determining the number and positions of tomographic images imaged in an interval including a time during which the fundus movement cannot be tracked; and
re-imaging the determined number of tomographic images at the determined positions.