Abstract
We realized graphics processing unit (GPU) based real-time 4D (3D + time) signal processing and visualization on a regular Fourier-domain optical coherence tomography (FD-OCT) system with a nonlinear k-space spectrometer. An ultra-high speed linear spline interpolation (LSI) method for λ-to-k spectral re-sampling is implemented in the GPU architecture, which gives average interpolation speeds of >3,000,000 line/s for 1024-pixel OCT (1024-OCT) and >1,400,000 line/s for 2048-pixel OCT (2048-OCT). The complete FD-OCT signal processing including λ-to-k spectral re-sampling, fast Fourier transform (FFT) and post-FFT processing have all been implemented on a GPU. The maximum complete A-scan processing speeds are investigated to be 680,000 line/s for 1024-OCT and 320,000 line/s for 2048-OCT, which correspond to 1GByte processing bandwidth. In our experiment, a 2048-pixel CMOS camera running up to 70 kHz is used as an acquisition device. Therefore the actual imaging speed is camera-limited to 128,000 line/s for 1024-OCT or 70,000 line/s for 2048-OCT. 3D Data sets are continuously acquired in real time at 1024-OCT mode, immediately processed and visualized as high as 10 volumes/second (12,500 A-scans/volume) by either en face slice extraction or ray-casting based volume rendering from 3D texture mapped in graphics memory. For standard FD-OCT systems, a GPU is the only additional hardware needed to realize this improvement and no optical modification is needed. This technique is highly cost-effective and can be easily integrated into most ultrahigh speed FD-OCT systems to overcome the 3D data processing and visualization bottlenecks.
Highlights
The acquisition line (A-scan) speed of Fourier-domain optical coherence tomography (FDOCT) has been advancing rapidly to >100,000 line/s level in the last few years
The complete Fourier-domain optical coherence tomography (FD-OCT) signal processing including interpolation, fast Fourier transform (FFT) and post-FFT processing have all been implemented on a graphics processing unit (GPU). 3D Data sets are continuously acquired in real time, immediately processed and visualized by either en face slice extraction or ray-casting based volume rendering from 3D texture mapped in graphics memory
Since currently there is no suitable function in Compute Unified Device Architecture (CUDA) library for λ-to-k spectral re-sampling, here we propose a GPU accelerated linear spline interpolation (LSI) method as following: Start from the LSI equation: S '[ j] = S[i] + S[i +1] − S[i] (k '[ j] − k[i]), (1)
Summary
The acquisition line (A-scan) speed of Fourier-domain optical coherence tomography (FDOCT) has been advancing rapidly to >100,000 line/s level in the last few years. To overcome the signal processing bottleneck, several solutions have recently been proposed and demonstrated: Multi-CPU parallel processing has been implemented and achieved 80,000 line/s processing rate on nonlinear-k system [8] and 207,000 line/s on lineark system for 1024-OCT [9]; A linear-k Fourier-domain mode-locked laser (FDML) with direct hardware frequency demodulation method enabled real-time en face image by yielding the analytic reflectance signal from one depth for each axial scan [10]; More recently, a graphics processing unit (GPU) has been utilized for processing FD-OCT data [11] using linear-k spectrometer. For standard FD-OCT systems, a GPU is the only additional hardware needed to realize this improvement and no optical modification is needed This technique is highly cost-effective and can be integrated into most ultrahigh speed FD-OCT systems to overcome the 3D data processing and visualization bottlenecks
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