Analysis of Various Artifacts Produced by Spectral-Domain Optical Coherence Tomography Based on Macular Pathologies

Yong Woon Shin; Ju Hyang Lee; Jae Yeon Jun; Yumi Song; Hee Yoon Cho; Byung Ro Lee

doi:10.3341/jkos.2010.51.8.1084

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Shin, Lee, Jun, Song, Cho, and Lee: Analysis of Various Artifacts Produced by Spectral-Domain Optical Coherence Tomography Based on Macular Pathologies

Original Article

J Korean Ophthalmol Soc 2010;51(8):1084-1091.

Published online: 7 September 2010

DOI: https://doi.org/10.3341/jkos.2010.51.8.1084

Analysis of Various Artifacts Produced by Spectral-Domain Optical Coherence Tomography Based on Macular Pathologies

Yong Woon Shin, MD, Ju Hyang Lee, MD, Jae Yeon Jun, MD, Yumi Song, MD, Hee Yoon Cho, MD, Byung Ro Lee, MD

Department of Ophthalmology, Hanyang University College of Medicine, Seoul, Korea

Address reprint requests to Byung Ro Lee, MD Department of Ophthalmology, Hanyang University Medical Center #17 Haengdang-dong, Seongdong-gu, Seoul 133-070, Korea Tel: 82-2-2290-8570, Fax: 82-2-2290-8570, E-mail: brlee@hanyang.ac.kr

Received 6 January 2010 Accepted 30 June 2010

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To report the frequency, severity and various types of artifacts associated with spectral-domain optical coherence tomography (SD-OCT) based on macular pathologies.

Methods

Data was collected retrospectively from 116 eyes of 116 subjects. SD-OCT (3D-1000, Topcon Corp., Japan) imaging was performed in 40 healthy eyes, 45 eyes with intraretinal pathology (IRP) and 31 eyes with subretinal pathology (SRP). The scan protocol was 12×6 mm radial scan. The frequency and types of artifacts were investigated in each scan and were analyzed based on macular disease. Additionally, the effect of artifacts on the measurement of macular thickness was studied.

Results

Errors occurred in 77 eyes (66.38%). Inner retinal boundary misidentification (IRBM) was the most common error (25.86%), with the frequencies of other types of artifacts being 10.34% for off-center fixation, 15.52% for degraded image and 8.6% for outer retinal boundary misidentification (ORBM). The overall error rate of SD-OCT in the retinal pathology group was much higher than that in the normal group. Macular thickness was underestimated in the IRP group because the outer retinal boundary of the IRP group tended to be misidentified toward the inner retina (p＜0.01).

Conclusions

SD-OCT can frequently cause various types of artifacts in patients with macular disease. When interpreting OCT images, the artifacts of SD-OCT should be considered in order to obtain accurate macular thickness and to prevent erroneous clinical decisions.

Keywords: Artifact, Macular disease, Segmentation error, Spectral domain optical coherence tomography

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Figure 1.

Type of artifacts of Fourier-domain OCT in current study. (A) IRBM, inner retina boundary misidentification. (B) ORBM, outer retinal boundary misidentification. (C) Off center fixation: white arrow, center of OCT; yellow arrow; center of retina. (D) Degraded image, note that Q factor of this image is 30.98, which means signal strength of OCT is low.

Figure 2.

Examples of artifact scoring. (A) OCT image shows inner retina boundary misidentification of central macula. 1 point is given due to presence of error. Because deviations of horizontal and vertical line are more than two thirds of the central macula respectively, 4 points are added. Therefore, the sum of error scores in this scan is 5 points. (B) OCT image shows outer retina boundary misidentification of the outer macula. One point is given due to presence of error. Only 1 point is added because deviation of the horizontal line is less than one third of the outer macula and deviation of the vertical line is from one third to two thirds of the outer macula. The sum of error score is 2 points.

Figure 3.

Examples of wrong measured MT. (A) Overestimation of MT due to IRBM. (B) Overestimation of MT due to ORBM. (C) Underestimation of MT due to IRBM. (D) Underestimation of MT due to ORBM. MT=macular thickness; IRBM=inner retina boundary misidentification; ORBM=outer retina boundary misidentification.

Table 1.

Demographic data in current study

	Disease groups (n=116)			P-value
	Normal (n=40)	IRP (n=45)	SRP (n=31)	P-value
Age (yr)	54.65 ± 13.59	57.81 ± 12.70	60.64 ± 11.09	0.03^*
Sex (Male: Female)	16: 24	19: 26	17: 14	0.42^†
Diagnosis (number)		DME 25	eAMD CNV 20
		RVOME 10	nonAMD CNV 9
		FTMH 4	Others 2
		ERM 4
		Others 2

^* ANOVA test

^† Pearson chi-square test. IRP=intraretinal pathology; SRP=subretinal pathology; DME=diabetic macular edema; RVOME=retinal venous occlusion with macular edema; FTMH=full-thickness macular hole; ERM=idiopathic epiretinal membrane; eAMD CNV=choroidal neovascularization due to exudative age-related macular degeneration; nonAMD CNV=choroidal neovascularization due to other various macular disease.

Table 2.

Frequency of artifacts in spectral-domain OCT based on underlying pathology

	Normal	IRP	SRP	Total
IRBM	20.0% (n=8)	35.60% (n=16)	12.90% (n=6)	25.86% (n=30)
ORBM	0% (n=0)	6.7% (n=3)	19.40% (n=7)	8.62% (n=10)
Both (IRBM+ORBM)	10.0% (n=4)	35.6% (n=16)	45.2% (n=14)	29.31% (n=34)
Off center fixation	0% (n=0)	17.78% (n=8)	13.79% (n=4)	10.34% (n=12)
Degraded image	7.5% (n=3)	22.22% (n=10)	17.24% (n=5)	15.52% (n=18)
Presence of any errors	37.5% (n=15)	88.89% (n=40)	96.7% (n=30)
Overall rate of errors	66.38% (n=77)
IRP=intraretinal pathology; SRP=subretinal pathology; IRBM=inner retinal boundary misidentification; ORBM=outer retinal boundary misidentification. Retinal boundary misidentifications can be coexisted with off center fixation or degraded image error.

Table 3.

Average error score (AES) of artifacts based on underlying pathology

Diagnosis	IRBM		ORBM		Off center fixation	Degraded image
	CM	OM	CM	OM	Off center fixation	Degraded image
	Range 0∼5				Range 0∼1
Normal	0.65 ± 1.44	0.61 ± 1.28	0.00 ± 0.01	0.04 ± 0.15	0	0.07 ± 0.26
IRP	0.75 ± 1.12	0.73 ± 1.02	0.17 ± 0.55	0.34 ± 0.66	0.15 ± 0.36	0.13 ± 0.34
SRP	0.82 ± 1.44	0.63 ± 1.03	0.13 ± 0.34	0.27 ± 0.42	0.20 ± 0.41	0.10 ± 0.31
Total	0.73 ± 1.29	0.67 ± 1.11	0.10 ± 0.41	0.22 ± 0.51	0.10 ± 0.31	0.10 ± 0.31
CM=central macular area; OM=outer macular area; IRBM=inner retinal boundary misidentification; ORBM=outer retinal boundary misidentification; IRP=intraretinal pathology; SRP=subretinal pathology.

Table 4.

Comparison of average error score between each group (^* P-value)

	Error type
	IRBM (CM)	IRBM (OM)	ORBM (CM)	ORBM (OM)	Off center fixation	Degraded image
N-I	0.932	0.853	0.114	0.013	0.053	0.671
I-S	0.976	0.929	0.904	0.871	0.763	0.938
S-N	0.885	0.998	0.509	0.212	0.04	0.945
IRBM=inner retinal boundary misidentification; ORBM=outer retinal boundary misidentification; CM=central macula; OM=outer macula; N-I=comparison of AES between normal and intraretinal pathology groups; I-S=comparison of AES between intraretinal and subretinal pathology group; S-N=comparison of AES between normal and subretinal pathology group. ^* ANOVA test with Turkey's multiple comparison test.

Table 5.

Average numbers of scans which show wrong measured macular thickness in SD-OCT

	Normal	IRP		SRP
	Number of scans	Number of scans	^* P-value	Number of scans	P-value
OMT due to IRBM	0.98 ± 2.22	1.64 ± 2.28	0.572	1.40 ± 2.11	0.275
UMT due to IRBM	0.88 ± 2.60	1.53 ± 2.49	0.482	1.50 ± 3.49	0.680
OMT due to ORBM	0.12 ± 0.40	0.31 ± 1.17	0.572	0.50 ± 0.76	0.275
UMT due to ORBM	0.02 ± 0.16	1.44 ± 2.44	0.000	0.55 ± 1.19	0.0519
OMT=overestimation of macular thickness; UMT=underestimation of macular thickness; IRBM=inner retinal boundary misidentification; ORBM=outer retinal boundary misidentification; IRP=intraretinal pathology; SRP=subretinal pathology.

^* Mean comparison of the number of abnormal scans between normal and pathology group by ANOVA test.

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