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Joint Iterative Reconstruction and Motion Compensation for Optical Coherence Tomography Angiography

Joint Iterative Reconstruction and Motion Compensation for Optical Coherence Tomography
Angiography

(Third Party Funds Single)

Overall project:
Project leader: ,
Project members: , ,
Start date: July 24, 2017
End date:
Acronym: Joint Reco & MoCo for OCT(A)
Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
URL:

Abstract

Optical coherence tomography (OCT) is a non-invasive 3-D optical imaging
modality that is a standard of care in ophthalmology [1,2]. Since the introduction of Fourier-domain OCT [3], dramatic increases in imaging speed
became possible, enabling 3-D volumetric data to be acquired. Typically, a
region of the retina is scanned line by line, where each scanned line
acquires a cross-sectional image or a B-scan. Since B-scans are acquired
in milliseconds, slices extracted along a scan line, or the fast scan
axis, are barely affected by motion. In contrast, slices extracted
orthogonally to scan lines, i. e. in slow scan direction, are
affected by various types of eye motion occurring throughout the full,
multi-second volume acquisition time. The most relevant types of eye
movements during acquisition are (micro-)saccades, which can introduce
discontinuities or gaps between B-scans, and slow drifts, which cause
small, slowly changing distortion [4]. Additional eye motion is caused by pulsatile blood flow,
respiration and head motion. Despite ongoing advances in instrument
scanning speed [5,6] typical volume acquisition times have
not decreased. Instead, the additional scanning speed is used for dense
volumetric scanning or wider fields of view [7]. OCT angiography (OCTA) [811] multiplies the
required number of scans by at least two, and even more scans are needed
to accommodate recent developments in blood flow speed estimation which
are based on multiple interscan times [12,13]. As a consequence,
there is an ongoing need for improvement in motion compensation especially
in pathology [1416].

We develop novel methods for retrospective motion correction of OCT volume scans of the anterior and posterior eye, and widefield imaging. Our algorithms are clinically usable due to their suitability for patients with limited fixation capabilities and increased amount of motion, due to their fast processing speed, and their high accuracy, both in terms of alignment and motion correction. By merging multiple accurately aligned scans, image quality can be increased substantially, enabling the inspection of novel features.

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