Spectroscopic imaging of the retinal vessels using a new dual-wavelength

Rasta, Seyed Hossein; Manivannan, A.; Sharp, P.

doi:10.1117/12.831635

Cited by 4 publications

(13 citation statements)

References 14 publications

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“…The strategy we have adopted is to screen the whole image by a fixed window size, small enough to enclose areas with desired characteristics. 15 Finally, thresholding operation of morphological opening and closing is performed to discard false positives among the detected nominees. In order to select a suitable threshold level for statistical momentum characteristics, we selected a total of five images and five corresponding patches.…”

Section: Methodsmentioning

confidence: 99%

Detection of retinal capillary nonperfusion in fundus fluorescein angiogram of diabetic retinopathy

Rasta¹,

Nikfarjam²,

Javadzadeh³

2016

Bioimpacts

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Introduction: Retinal capillary nonperfusion (CNP) is one of the retinal vascular diseases in diabetic retinopathy (DR) patients. As there is no comprehensive detection technique to recognize CNP areas, we proposed a different method for computing detection of ischemic retina, non-perfused (NP) regions, in fundus fluorescein angiogram (FFA) images. Methods: Whilst major vessels appear as ridges, non-perfused areas are usually observed as ponds that are surrounded by healthy capillaries in FFA images. A new technique using homomorphic filtering to correct light illumination and detect the ponds surrounded in healthy capillaries on FFA images was designed and applied on DR fundus images. These images were acquired from the diabetic patients who had referred to the Nikookari hospital and were diagnosed for diabetic retinopathy during one year. Our strategy was screening the whole image with a fixed window size, which is small enough to enclose areas with identified topographic characteristics. To discard false nominees, we also performed a thresholding operation on the screen and marked images. To validate its performance we applied our detection algorithm on 41 FFA diabetic retinopathy fundus images in which the CNP areas were manually delineated by three clinical experts. Results: Lesions were found as smooth regions with very high uniformity, low entropy, and small intensity variations in FFA images. The results of automated detection method were compared with manually marked CNP areas so achieved sensitivity of 81%, specificity of 78%, and accuracy of 91%.The result was present as a Receiver operating character (ROC) curve, which has an area under the curve (AUC) of 0.796 with 95% confidence intervals. Conclusion: This technique introduced a new automated detection algorithm to recognize non-perfusion lesions on FFA. This has potential to assist detecting and managing of ischemic retina and may be incorporated into automated grading diabetic retinopathy structures.

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Section: Methodsmentioning

confidence: 99%

Detection of retinal capillary nonperfusion in fundus fluorescein angiogram of diabetic retinopathy

Rasta¹,

Nikfarjam²,

Javadzadeh³

2016

Bioimpacts

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“…The cell size was chosen to be at least twice as large as the expected maximum diameter of retinal vessels. [ 35 ] The optimum size of the cell was chosen to be 31 × 31 to include the variations in illumination. [ 34 ]…”

Section: Methodsmentioning

confidence: 99%

A comparative study on preprocessing techniques in diabetic retinopathy retinal images: Illumination correction and contrast enhancement

et al. 2015

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To investigate the effect of preprocessing techniques including contrast enhancement and illumination correction on retinal image quality, a comparative study was carried out. We studied and implemented a few illumination correction and contrast enhancement techniques on color retinal images to find out the best technique for optimum image enhancement. To compare and choose the best illumination correction technique we analyzed the corrected red and green components of color retinal images statistically and visually. The two contrast enhancement techniques were analyzed using a vessel segmentation algorithm by calculating the sensitivity and specificity. The statistical evaluation of the illumination correction techniques were carried out by calculating the coefficients of variation. The dividing method using the median filter to estimate background illumination showed the lowest Coefficients of variations in the red component. The quotient and homomorphic filtering methods after the dividing method presented good results based on their low Coefficients of variations. The contrast limited adaptive histogram equalization increased the sensitivity of the vessel segmentation algorithm up to 5% in the same amount of accuracy. The contrast limited adaptive histogram equalization technique has a higher sensitivity than the polynomial transformation operator as a contrast enhancement technique for vessel segmentation. Three techniques including the dividing method using the median filter to estimate background, quotient based and homomorphic filtering were found as the effective illumination correction techniques based on a statistical evaluation. Applying the local contrast enhancement technique, such as CLAHE, for fundus images presented good potentials in enhancing the vasculature segmentation.

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“…From our previous work two wavelengths λ 1 = 670 nm and λ 2 = 810 nm were chosen [6,8]. To choose wavelengths for perfusion imaging of the eye a series of criteria was considered to introduce a new combination of wavelengths based on previous researches [5,12].…”

Section: Beer-lambert Law For Haemoglobin Saturationmentioning

confidence: 99%

“…The scanning laser ophthalmoscope illuminates the eye using a low light intensity with high contrast due to low scattering of light. The Aberdeen group previously reported the reproducibility of the cSLO measurements in the human eye studies [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

The feasibility of oxygen perfusion imaging of the human retina using a new non-invasive near infrared imaging technique

Rasta

Manivannan

Sharp

2010

2010 17th Iranian Conference of Biomedical Engineering (ICBME)

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The feasibility of non-invasive imaging oxygen perfusion in the human retina was evaluated using a confocal scanning laser ophthalmoscope (cSLO) that adapted to use a new combination of two red (670 nm) and near infrared (810 nm) wavelengths simultaneously. Spectral analyses of the physiological status of retinal blood vessels give the ability to image perfusion in the human eye. This technique was evaluated using measurements made on an eye model, normal and diabetic retinopathy volunteers' eyes. The reproducibility of the measurements of reflected light from the eye was investigated. The measurements of light reflected from retinal vessels were determined and oxygen saturation of blood using spectral transmittance based on Beer-Lambert law was investigated. The relative oxygen levels of retinal blood vessels (artery and vein) were successfully determined using these two wavelengths. The technique showed promise in the determination of the relative oxygen saturation levels of the retina in amongst eye subjects.

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Spectroscopic imaging of the retinal vessels using a new dual-wavelength

Cited by 4 publications

References 14 publications

Detection of retinal capillary nonperfusion in fundus fluorescein angiogram of diabetic retinopathy

Detection of retinal capillary nonperfusion in fundus fluorescein angiogram of diabetic retinopathy

A comparative study on preprocessing techniques in diabetic retinopathy retinal images: Illumination correction and contrast enhancement

The feasibility of oxygen perfusion imaging of the human retina using a new non-invasive near infrared imaging technique

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