Limits...
Objective determination of optimal number of spectral-domain optical coherence tomographic images of retina to average.

Shirasawa M, Sakamoto T, Terasaki H, Yamashita T, Uchino E, Sonoda S - PLoS ONE (2014)

Bottom Line: The SDs decreased significantly when the number of images averaged increased from 1 to 5 and also from 5 to 20 (P<0.05, post hoc Tukey's honestly significant difference tests).Similar results were obtained with the phantom eye model.Although the image quality of the SD-OCT images of the retina improved with an increase in the number of images averaged, it does not improve significantly by averaging more than 20 images.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.

ABSTRACT

Purpose: To determine by objective methods the minimum number of spectral-domain optical coherence tomographic (SD-OCT) images to average to obtain the clearest retinal image.

Methods: SD-OCT Images were obtained from 9 healthy eyes and also from a phantom eye model. The SD-OCT images were obtained by averaging 1, 5, 20, 60, and 100 B-scan images. The reflectivity (mean gray value) of the different retinal layers was evaluated in these images. The image quality was evaluated by the size of the standard deviations (SDs) and the contrast-to-noise ratios (CNRs). A phantom eye model made by TiO2 silicone plates was also examined.

Results: The SDs decreased significantly when the number of images averaged increased from 1 to 5 and also from 5 to 20 (P<0.05, post hoc Tukey's honestly significant difference tests). The SD of the automatic real time averaging of 1 (ART = 1) and ART = 5 were significantly larger than the SD of ART = 100 (P<0.05). The SDs of all other averaged numbers were not significantly larger than that of ART = 100. The CNR increased with an increase in the number of images averaged, and there was a significant increase between ART = 1 to 5 and between ART = 5 to 20 (P<0.05). No significant differences in the CNR was observed between ART = 5, ART = 20 and ART = 60. Similar results were obtained with the phantom eye model.

Conclusions: Although the image quality of the SD-OCT images of the retina improved with an increase in the number of images averaged, it does not improve significantly by averaging more than 20 images.

Show MeSH

Related in: MedlinePlus

Gray values of SD-OCT reflectivity of each retinal layer of normal human eyes.The mean gray values of retina were significantly lower in the single scan image than in image averaged 100 times (mean gray value; **; P<0.01; post hoc Dunnett's multiple comparison test). ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tip; RPE, retinal pigment epithelium. ART indicates automatic real time averaging.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4206300&req=5

pone-0110550-g003: Gray values of SD-OCT reflectivity of each retinal layer of normal human eyes.The mean gray values of retina were significantly lower in the single scan image than in image averaged 100 times (mean gray value; **; P<0.01; post hoc Dunnett's multiple comparison test). ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tip; RPE, retinal pigment epithelium. ART indicates automatic real time averaging.

Mentions: The gray value of the vitreous did not change significantly after averaging up to 100 images (P = 0.083; repeated measures ANOVA). For the IPL, INL, ONL, ELM, IS/OS, COST, and RPE, the gray value of ART = 1 was significantly lower than that of ART = 100. By our definition using ImageJ software, the brightness of each point was expressed in 256 levels from black  = 0 to white  = 255. Thus, the higher gray values indicate a brighter image. These findings indicate that the ROI became brighter after 100 averages (Figure 3).


Objective determination of optimal number of spectral-domain optical coherence tomographic images of retina to average.

Shirasawa M, Sakamoto T, Terasaki H, Yamashita T, Uchino E, Sonoda S - PLoS ONE (2014)

Gray values of SD-OCT reflectivity of each retinal layer of normal human eyes.The mean gray values of retina were significantly lower in the single scan image than in image averaged 100 times (mean gray value; **; P<0.01; post hoc Dunnett's multiple comparison test). ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tip; RPE, retinal pigment epithelium. ART indicates automatic real time averaging.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206300&req=5

pone-0110550-g003: Gray values of SD-OCT reflectivity of each retinal layer of normal human eyes.The mean gray values of retina were significantly lower in the single scan image than in image averaged 100 times (mean gray value; **; P<0.01; post hoc Dunnett's multiple comparison test). ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tip; RPE, retinal pigment epithelium. ART indicates automatic real time averaging.
Mentions: The gray value of the vitreous did not change significantly after averaging up to 100 images (P = 0.083; repeated measures ANOVA). For the IPL, INL, ONL, ELM, IS/OS, COST, and RPE, the gray value of ART = 1 was significantly lower than that of ART = 100. By our definition using ImageJ software, the brightness of each point was expressed in 256 levels from black  = 0 to white  = 255. Thus, the higher gray values indicate a brighter image. These findings indicate that the ROI became brighter after 100 averages (Figure 3).

Bottom Line: The SDs decreased significantly when the number of images averaged increased from 1 to 5 and also from 5 to 20 (P<0.05, post hoc Tukey's honestly significant difference tests).Similar results were obtained with the phantom eye model.Although the image quality of the SD-OCT images of the retina improved with an increase in the number of images averaged, it does not improve significantly by averaging more than 20 images.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.

ABSTRACT

Purpose: To determine by objective methods the minimum number of spectral-domain optical coherence tomographic (SD-OCT) images to average to obtain the clearest retinal image.

Methods: SD-OCT Images were obtained from 9 healthy eyes and also from a phantom eye model. The SD-OCT images were obtained by averaging 1, 5, 20, 60, and 100 B-scan images. The reflectivity (mean gray value) of the different retinal layers was evaluated in these images. The image quality was evaluated by the size of the standard deviations (SDs) and the contrast-to-noise ratios (CNRs). A phantom eye model made by TiO2 silicone plates was also examined.

Results: The SDs decreased significantly when the number of images averaged increased from 1 to 5 and also from 5 to 20 (P<0.05, post hoc Tukey's honestly significant difference tests). The SD of the automatic real time averaging of 1 (ART = 1) and ART = 5 were significantly larger than the SD of ART = 100 (P<0.05). The SDs of all other averaged numbers were not significantly larger than that of ART = 100. The CNR increased with an increase in the number of images averaged, and there was a significant increase between ART = 1 to 5 and between ART = 5 to 20 (P<0.05). No significant differences in the CNR was observed between ART = 5, ART = 20 and ART = 60. Similar results were obtained with the phantom eye model.

Conclusions: Although the image quality of the SD-OCT images of the retina improved with an increase in the number of images averaged, it does not improve significantly by averaging more than 20 images.

Show MeSH
Related in: MedlinePlus