ophthalmic optical coherence tomography
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Program#/Poster#: 1838/D747
Abstrac t Ti tle: Image Quality Enhancement in Ophthalmic Optical Coherence Tomography
by Frame Registration and Averaging
Presentation Start/End
Time:
Monday, Apr 28, 2008, 11:15 AM - 1:00 PM
Location: Hall B/C
Reviewing Code: 228 imaging techniques: novel image processing -VI
Author Block: P. Liu1,2, O. Tan1, Y. Li1, D. Huang1. 1Ophthalmology, Doheny Eye Institute, Los
Angeles, CA; 2College of Biomedical Engineering & Instrument Science,ZheJiang University, HangZhou, China.
Keywords: 551 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound), 548
image processing, 550 imaging/image analysis: non-clinical
Purpose: To evaluate quality enhancement for Fourier-domain optical coherence tomography (FD-OCT)
images by averaging multiple registered frames.
Methods:7 normal subjects were scanned with a commercially available FD-OCT system (RTVue with
software version 2.7, Optovue, Fremont, CA) . The system scans 26,000 a-scans per second and has 5 micron
axial resolution. Subjects were scanned with line scans on retina (centered at fovea, scan length=6mm), cornea(centered at vertex, scan length=6mm) and anterior chamber angle (scan length= 4mm). Sixteen consecutive
frames are acquired for each scan. A reference frame was picked by the operator and a rectangular region was
drawn on the reference frame. An automatic algorithm was applied to register other frames to the content in the
rectangle. The algorithm automatically determines if registration is successful for each frame. Successfully
registered frames were averaged in the logarithmic domain. Contrast-to-noise ratio (CNR) enhancement was
used to quantify the reduction of background and speckle noise. CNR enhancement ratio is equal to the CNR of
averaged image divided by CNR of reference image. To evaluate edge preservation, a cross correlation
parameter (F. Sattar et al., Image enhancement based on a nonlinear multiscale method, IEEE Trans.
Image Processing, vol. 6, pp. 888-895, June 1997) was used. The interpretation of is: 0 to 0.20, poor; 0.21 to
0.40, fair; 0.41 to 0.60, moderate; 0.61 to 0.80, good; and above 0.80, excellent.
Results: The values of CNR enhancement ratio and are shown in Table 1
Conclusions: The frame-averaging algorithm on the RTVue FD-OCT system successfully improved image
quality by suppressing background and speckle noises. A moderate loss of edge sharpness was observed,
indicating that there is room for further improvement of the registration algorithm. The algorithm worked best on
corneal images.
Table 1. CNR enhancement ratio and result
Scan location CNR enhancement ratio
Retina 2.01 0.67 0.53 0.09
Angle 3.64 1.32 0.44 0.03
Cornea 5.57 1.65 0.54 0.19
Commercial Relationship: P. Liu, None; O. Tan, Optovue, Inc., F; Optovue, Inc., P; Y. Li, Optovue, Inc., F;
Optovue, Inc., P; D. Huang, Optovue, Inc., F; Optovue, Inc., I; Optovue, Inc., C;Optovue, Inc., P; Optovue, Inc., R.
Support: NIH grants R01 EY018184-01, NIH grants R01 EY013516, P30 EY03040;
Research to Prevent Blindness; Optovue, Inc;CHINA SCHOLARSHIP
2007U07002
2008, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to
www.iovs.org to access the version of record. For permission to reproduce any abstract, contact the ARVO Office at
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