Distributed Scan Pattern for OCT Motion Artifact Reduction
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Solution Overview
Problem
Current optical coherence tomography (OCT) systems face challenges in accurately measuring corneal refractive power after laser refractive surgery due to motion artifacts, which degrade the calculation of corneal power and lead to unsatisfactory outcomes in cataract surgery, especially for patients who have undergone LASIK or similar procedures.
Innovation Solution
The implementation of a distributed scan pattern in OCT systems that acquires data at multiple locations non-sequentially in time, allowing for the estimation of a sample profile by encoding patient motion as high spatial frequency content, which can be separated from the actual profile using high-pass filtering, thereby reducing motion artifacts and improving the accuracy of corneal refractive power measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential scanning is used to acquire OCT data, then the scanning process is simple and fast, but motion artifacts are introduced that degrade measurement accuracy
Solution Approach 1:
The scanning process is segmented into multiple passes, where each pass acquires data from a subset of locations. The distributed scan pattern divides the corneal surface into regions that are scanned in an interlaced manner, allowing spatially adjacent locations to be acquired at different times. This segmentation enables motion artifact reduction while maintaining measurement accuracy.
Solution Approach 2:
The scanning pattern is made dynamic by varying the scan locations and timing across multiple passes. Rather than following a fixed sequential pattern, the system adaptively distributes scan locations across the corneal surface, with the second pass scanning locations between those of the first pass. This dynamic approach allows the system to accommodate patient motion while maintaining measurement precision.
2Measurement precision
If faster scanning is used to reduce motion artifacts, then measurement accuracy improves, but the system cannot separate motion from actual profile changes
Solution Approach 1:
The system employs periodic scanning passes with alternating patterns. The first pass scans certain locations, the second pass scans intermediate locations, and subsequent passes continue this interlaced pattern. This periodic action creates a temporal distribution of scan locations that allows separation of motion artifacts from actual profile changes through high-pass filtering, while maintaining reasonable acquisition time.
Solution Approach 2:
The problem is solved by adding a temporal dimension to the scanning pattern. Instead of scanning all locations in a single spatial pass, the system distributes acquisitions across multiple time points, creating a time-space mapping. This allows the use of high-pass filtering in the spatial domain to remove temporal motion artifacts, effectively separating motion from actual profile changes.
3Measurement precision
If distributed non-sequential scanning is used to reduce motion artifacts, then measurement accuracy improves, but the scanning process becomes more complex
Solution Approach 1:
The complex distributed scanning process is segmented into simple, repeatable passes. Each pass follows a straightforward scanning pattern, but the combination of multiple passes creates the distributed non-sequential acquisition. This segmentation maintains operational simplicity while achieving the complexity needed for motion artifact reduction.
Solution Approach 2:
The system uses feedback from the scanning process to guide subsequent passes. By analyzing the data acquired in earlier passes and the patient's motion patterns, the system optimizes the distribution of scan locations in subsequent passes. This feedback mechanism simplifies the overall operation by automatically adapting to patient-specific motion characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of corneal refractive power measurement to within 0.25D, comparable to or better than existing methods, reducing the risk of 'refractive surprises' in cataract surgery and providing more reliable intraocular lens power predictions.
Implementation Method 1
optical coherence tomography (OCT) systems face challenges in accurately measuring corneal refractive power
Implementation Method 2
allowing for the estimation of a sample profile by encoding patient motion as high spatial frequency content, which can be separated from the actual profile using high-pass filtering
Data Source
AI summary
Methods of reducing motion artifacts in Optical Coherence Tomography (OCT) include scanning a sample with a scan pattern to acquire OCT data at a plurality of data locations. The data locations are distributed in the scan pattern across the sample such that at least some spatially adjacent data locations are acquired non-sequentially in time. A profile of the sample corresponding to a sample surface or an aspect of an internal structure of the sample is estimated responsive the OCT data.