Microscope-integrated OCT at 800 kHz line rate for high speed 4D imaging of ophthalmic surgery

Abstract

Purpose : The en face view through an operating stereomicroscope offers limited depth perception. Recently developed microscope-integrated OCT (MIOCT) systems have enabled tomographic imaging of live surgery, but most implementations to date have been limited to live B-scans that capture limited information about maneuvers extending beyond the imaging plane. We recently reported on four dimensional (4D: 3D imaging over time) MIOCT for human retinal surgery, but this 100 kHz system was restricted to 3.3 vols/sec to sufficiently sample a 5x5 mm field of view (FOV). To facilitate imaging of fast surgical maneuvers with high sampling densities, we present a new high-speed 4D MIOCT (HS 4D MIOCT) system for volumetric imaging at 800 kHz line rate.

Methods : The HS 4D MIOCT system employed a 200 kHz swept-source commercially available laser buffered to 400 kHz. Using a temporal spectral splitting (TSS) technique inspired by split spectrum OCT angiography, each spectrum (original and buffered) was split in two sub-spectra that were processed independently, yielding A-scans with 2x poorer resolution but acquired at an effective line rate of 800 kHz. The axial resolution of the 800 kHz A-scans was 17.04 µm. The 800 kHz TSS OCT engine system was coupled to an MIOCT scanner for 4D imaging of porcine eye surgery.

Results : The HS 4D MIOCT data was acquired using two protocols: 200 A-scans/B-scan and 96 B-scans at 400 kHz, and 400 A-scans/B-scan and 96 B-scans at 800 kHz. Both imaging protocols achieved a volume imaging rate of 10.85 Hz over a 5x5 mm FOV, but the 800 kHz system provided twice the sampling density along the B-scan axis. HS 4D MIOCT images were acquired during porcine surgery with 27 gauge forceps (Fig. 1). The increased lateral sampling at 800 kHz aided in visualizing subtle structures such as the prongs of the forceps and superficial vasculature.

Conclusions : We demonstrated a prototype HS 4D MIOCT that utilizes TSS for volumetric imaging at 800 kHz line rate. The system was used to image porcine eye surgery at 10.85 volumes/sec with sufficient lateral pixels for human surgery applications.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Excerpts from a volumetric recording of porcine eye surgery with intrasurgical forceps acquired with high-speed 4D MIOCT (HS 4D MIOCT). Temporal spectral splitting (TSS) allowed volumetric imaging at 800 kHz A-scan rate and a 2x increase in lateral sampling density compared to 400 kHz imaging.