Abstract
Ultrahigh speed optical coherence tomography (OCT) systems with >100 kHz A-scan rates can generate volumes rapidly with minimal motion artifacts and are well suited for 4D imaging (volumes through time) applications such as intra-operative imaging. In such systems, high OCT data acquisition efficiency (defined as the fraction of usable A-scans generated during the total acquisition time) is desired to maximize the volumetric frame rate and sampling pitch. However, current methods for beam scanning using non-resonant and resonant mirror scanners can result in severe scan distortion and transverse oversampling as well as require acquisition dead times, which limit the acquisition efficiency and performance of ultrahigh speed 4D OCT. We introduce constant linear velocity spiral scanning (CLV-SC) as a novel beam scanning method to maximize the data acquisition efficiency of ultrahigh speed 4D OCT systems. We demonstrate that CLV-SC does not require acquisition dead times and achieves more uniform transverse sampling compared to raster scanning. To assess its clinical utility, we implement CLV-SC with a 400 kHz OCT system and image the anterior eye and retina of healthy adults at up to 10 volumes per second with isotropic transverse sampling, allowing B-scans with equal sampling pitch to be extracted from arbitrary locations within a single volume. The feasibility of CLV-SC for intra-operative imaging is also demonstrated using a 800 kHz OCT system to image simulated retinal surgery at 15 volumes per second with isotropic transverse sampling, resulting in high quality volume renders that enable clear visualization of surgical instruments and manipulation of tissue.
Highlights
Optical coherence tomography (OCT) is a non-contact tomographic imaging modality [1] that has achieved widespread adoption in clinical ophthalmology [2]
constant linear velocity spiral scanning (CLV-SC) is a continuous 2D scan pattern, and we demonstrate that properly configured and sequenced, it requires zero acquisition dead time and achieves more uniform transverse sampling for 4D optical coherence tomography (OCT) imaging compared to raster scanning
The superior performance of CLV-SC compared to bidirectional raster scanning (BRS) was more drastic for faster fvolume: At fvolume = 10 Hz, the CLV-SC degree of sampling uniformity was 13.5% greater than the degree of sampling uniformity for BRS
Summary
Optical coherence tomography (OCT) is a non-contact tomographic imaging modality [1] that has achieved widespread adoption in clinical ophthalmology [2]. Ultrahigh speed OCT enables volumetric imaging with isotropic transverse sampling, allowing post-acquisition visualization of high resolution B-scans from arbitrary orientations from a single volume [4,5]. These systems are well suited for 4D OCT imaging (volumetric imaging through time) applications [6,7], such as intra-surgical guidance [8,9,10,11], in which isotropic and high pitch transverse sampling would optimize volume render quality and system efficiency. Transverse oversampling, vignetting, and acquisition dead times limit the efficiency of ultrahigh speed OCT (defined here as the fraction of usable (displayable) versus total acquired A-scans) and lead to reduced effective A-scan rates and imaging speed
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