Ultra-Short-Term Reproducibility of Speckle-Noise Freed Fluid and Tissue Compartmentalization of the Choroid Analyzed by Standard OCT

Peter Maloca; Cyrill Gyger; Andreas Schoetzau; Pascal W Hasler

doi:10.1167/tvst.4.6.3

Ultra-Short-Term Reproducibility of Speckle-Noise Freed Fluid and Tissue Compartmentalization of the Choroid Analyzed by Standard OCT

Transl Vis Sci Technol. 2015 Nov 17;4(6):3. doi: 10.1167/tvst.4.6.3. eCollection 2015 Nov.

Authors

Peter Maloca¹, Cyrill Gyger¹, Andreas Schoetzau², Pascal W Hasler¹

Affiliations

¹ Department of Ophthalmology, University of Basel, Basel, Switzerland.
² Department of Biomedical Statistics, University of Basel, Basel, Switzerland.

Abstract

Purpose: We measured reproducibility of speckle-noise freed fluid and tissue compartmentalization of the choroid (choroidal angiography and tissue characterization).

Methods: This study included 26 eyes of 13 healthy females: 13 were used for repeated measurements and 13 were used for side comparison. A semiautomated algorithm removed speckle-noise with structure preservation.

Results: Intraclass correlation (ICC), with respect to reproducibility of the method, showed an ICC for choroidal fluid inner space analysis (FISA) of 95.15% (90.01-98.24). The ICC of tissue inner space analysis (TISA) was 99.75% (99.47-99.91). The total choroid ratio (TCR), calculated from volumes of tissue to vessels, showed an ICC of 88.84% (78.28-95.82). Comparison of eyes (left to right) showed a difference for FISA of 0.033 (95% confidence interval [CI] -0.0018-0.0680, P = 0.063), TISA -0.118 (CI -0.2373-0.0023, P = 0.055), and TCR -0.590 (CI -0.9047 to -0.2754, P = 0.004). The ICC for FISA and TISA showed a trend in the difference comparing left and right eyes; however, TCR showed a significant difference between the eyes in the measured area (P < 0.001). Mean overall FISA was 0.58 mm³ (range, 0.25-0.98 mm³, SD = 0.14). Mean TISA was 3.45 mm³ (range, 2.38-5.0 mm³, SD 0.072). Mean TCR was 6.13 (overall range, 3.93-10.2, SD = 1.34).

Conclusions: Differences in choroidal layers between subjects were found mainly due to alterations in choroidal tissue. Reproducibility of speckle-noise freed choroidal angiography appeared excellent.

Translational relevance: Speckle noise is a granular "noise" that appears in a wide range of medical imaging methods as ultrasonography, magnetic resonance, computer tomography, or optical coherence tomography (OCT). Findings from basic science about speckle noise were translated into a novel, medical image postprocessing application that can separate signal from speckle noise with structure preservation with high reproducibility and enhance medical imaging.

Keywords: angiography; choroid; imaging; optical coherence tomography; speckle noise; tissue.