Purpose:
High resolution Fourier domain OCT (FD-OCT) is a new clinical alternative to conventional time domain OCT (TD-OCT). Before FD-OCT can be used in clinical practice, it must first be compared to the current standard, TD-OCT. This study uses subjective and objective metrics to compare data quality from TD and FD-OCT devices.
Methods:
Fifty eyes of 28 consecutive patients were imaged with a TD-OCT device (StratusOCT, Carl Zeiss Meditec, USA) using a high-resolution radial line protocol (6 x 512 A-scans) and a prototype FD-OCT instrument (Topcon, Japan) using both a 3D-OCT protocol (128 x 512 A-scans) and a high-resolution B-scan protocol (1 x 1024 A-scans). Average scan qualities were rated subjectively using a 100 point scale. Numerical image quality metrics from each device (TQ for TD-OCT [10 point scale], FQ for FD-OCT [100 point scale]) were recorded. FQ was calculated on TD-OCT data by converting this data into the FD-OCT format and loading it with the FD-OCT software. TQ was not calculated on FD-OCT data because the FD-OCT data could not be imported into the TD-OCT software.
Results:
The mean subjective rating for TD-OCT (54.68) was 10% less than the mean subjective rating for the FD-OCT scans (60.77). The mean TQ for TD-OCT was 7.46. The mean FQ for TD-OCT was 70.12 (Fig 1) which was 6% less than the mean FQ for FD-OCT line scans (74.86) and 2% less than the mean FQ for FD-OCT 3D scans (71.39). TQ and FQ correlated well with subjective quality ratings (rTQ=0.83, p<.01; rFQ=0.79, p<.01) and correlated well with each other (r=0.92, p<.01).
Conclusions:
Objective image quality metrics provided by TD and FD-OCT devices correlate well with subjective assessments of image quality. Both subjective and objective measures of image quality suggest that the image quality of Fourier domain OCT is superior to time domain OCT.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • retina