| Choroid is the most vascularized structure in human eye.It is regarded as an important anatomical,physiological,photoprotective and immunology structure.However due to its relatively deep location beneath retinal pigmentary epithelium(RPE),direct imaging of the choroid lesion is difficult.Imaging technologies in the fundus has provided new approaches to our understanding of the deep area of choroid,from different aspect.in 1956 ultrasound was first reported the capture of the choroid imaging,and in 1973 Indocyanine Green Angiography was first described to observed in vivo dynamic time-lapse changes of the choroid.The advent of optical coherence tomography(OCT)in 1991 was able to revolutionarily present the sectional view of the choroid.However due its limited penetration ability at early stage,it is still very much constrained in revealing the full portrait of choroidal lesions.In 2008 the Enhanced-depth-Imaging OCT(EDI-OCT)made the full-depth imaging of the choroid and allied disorders.The advent of Optical Coherence Tomography Angiography(OCTA)was another cutting-edge event that allows for the visualized of the very detailed vasculature of the retina and choriocapillaries based on OCT scanning,however it also has its own limitations such as it can fail to image lesions if the flow within that area is too fast or too slow.Besides its imaging field of view is very limited for most of the devices.Multispectral imaging(MSI),as a non-invasive enface chorioretinal imaging technology,allows for the visualization of spatial-distribution of lightabsorbent structures and reflective surfaces,producing a series of retinal and choroidal images.The short wavelengths(550 nm-600 nm)of MSI has proved its application in retinal disorders such as diabetic retinopathy by multiple studies.We have observed in our clinical practice that longer wavelengths(680nm,780 nm,810 nm and 850 nm)showed good penetration beyond RPE barrier and a bird's-eye-view of the choroidal structure is highly promising for non-invasive diagnosis of choroidal lesions.Current this is still rarely reported and not been fully investigated.It is thus in our first part of the study we focused on the diagnostic power of MSI in several pachychoroid spectrum disease and its characteristic presentations quantified by choroidal vascular density.In the second part of the study,we further compare the features of several choroidal tumors by MSI and other imaging modalities,with quantified analysis of the investigation of tumor-specific spectrum fingerprint,which will serve as a foundation work for further large-sample clinical study.Part One Novel Imaging Characteristics in Pachychoroid Disease by MSIPurpose: The aim of this study was to describe the characteristics of eyes with pachychoroid diseases,including pachychoroid pigment epitheliopathy(PPE),central serous chorioretinopathy(CSCR)including acute and chronic types,pachychoroid neovascularization(PNV)and polypoidal choroidal vasculopathy(PCV)using multispectral imaging(MSI)and to evaluate the diagnostic accuracy and reliability of MSI in detecting pachychoroid-related disorders.Methods: A total of 173 patients with unilateral serous or hemorrhagic maculopathy eyes with diagnosis of central serous chorioretinopathy,pachychoroid neovascularization or polypoidal choroidal vasculopathy were included in the study.All study eye went through MSI and other multimodal imaging examinations.Images of MSI alone were evaluated by 2 retinal specialists masked to indocyanine green angiography(ICGA)findings for potential diagnosis.MSI-based diagnoses were compared with those made by FFA/ICGA.Diagnostic imaging characteristic criteria were set as the following:Polyp on MSI is defined by the characteristic oval or lobular hyper-reflective oval lesion with hyporeflective center.Branching vascular networks(BVN)on MSI is featured by a hyper-reflective interlacing signal staring from middle wavelengths.Subretinal fluid(SRF)is characterized by the minimally hyperreflective disc border and iso-reflectance within the detachment area but significantly increased hyperreflectance in longer wavelengths.PED is featured by the either oval or relatively irregular hyperreflective-bordered lesion with iso-reflectance in the center.Diagnostic sensitivity and specificity of each pachychoroid disease was calculated,and the morphological MSI features for non-invasive evaluation of pachychoroid pathology were summarized.Quantitative analysis was performed in terms of SFCT,large vascular choroidal thickness(LVCT),choroidal vessel density was analyzed based on quantified MSI(CVD).The correlation of variants including age,gender,axial length,spherical equivalent on the parameters was also analyzed.Results:1.The diagnosis between different graders showed high agreement(Cohen's Kappa=0.91).2.Sensitivity,specificity,positive predicative value(PPV)and negative predicative value(NPV)for diagnosing CSCR by MSI were 97.86%,96.00%,96.67% and 97.30% respectively,and for diagnosing PNV were80.00%,95.21%,66.67% and 97.55% respectively,and for PCV were87.27%,96.91%,92.31% and 94.21% respectively.3.The sensitivity and specificity for detecting polypoidal lesion were87.27% and 92.31%,which was comparable to the performance of ICGA.The sensitivity and specificity for detecting BVN were 91.49% and 92.06%respectively.The sensitivity and specificity for detecting subretinal fluid(SRF)were 82.16% and 94.87%,while the sensitivity and specificity for detecting pigment epithelial detachment(PED)were 82.11% and 74.00% respectively.The sensitivity and specificity for detecting Pachyvessels were 35.90% and94.74% respectively.4.The sensitivity and specificity for detecting leakage point in acute CSCR is significantly higher than in the chronic group(P<0.01).The detection of leakage point in CSCR with PED is more characteristically presented as hyperreflective dots while in CSCR without PED the leakage is significantly less characteristic.5.MSI-based choroidal vascular vessel density CDVMSI showed no statistical significance in CSCR group and PNV group,but significantly higher than PCV group(P<0.001).CDVMSI showed negative correlation with age(r=-0.158,P=0.0187),positive correlation with combined thickness of choriocapillaries and Sattler's layer(r=0.425,P<0.001),but no relation with gender,axial length,spherical equivalent or SFCT.Summary:1.MSI presented characteristic imaging features for pachychoroid lesion with good diagnostic accuracy for symptomatic pachychoroid diseases including CSCR,PNV and PCV.2.MSI-based CVD could be a new parameter to evaluate choroidal changes in pachychoroid disorders.Part Two Novel Imaging Feature of MSI in diagnosis of choroidal tumors and its comparative analysis with multimodal imagingPurpose: To identify novel tumor-pathological-specific features of ossification and vascularization-related reflectance by using multispectral imaging(MSI)in patients diagnosed with several choroidal tumors,specifically non-melanocytic tumors(choroidal osteoma,choroidal hemangioma)and melanocytic tumors(choroidal melanoma)in comparison with choroidal nevus.Methods: This was a cross-sectional,comparative,observational study.We complied a total of 30 eyes of 29 patients consisting of the following: 9choroidal osteomas,10 choroidal hemangiomas,1 choroidal melanoma,10 choroidal nevi.MSI was performed on the lesions to create images that were analyzed by 3 different physicians.In addition to MSI,we also used multimodal imaging including color fundus photo(CFP),autofluorescence(AF),fluorescein/ Indocyanine angiography(FFA/ICGA),OCT and EDI-OCT,ocular ultrasonography,computerized tomography(CT)and/or Magnetic Resonance Imaging(MRI).were observed with multispectral imaging(MSI).Traditional multi-mode fundus examination,including fundus color photography and optical coherence tomography(EDI-OCT),were performed.Spectrum-based imaging features were recorded: hyperreflectance,hyporeflectance,isoreflectance,homogenous or heterogenous reflectance and the pattern if the reflectance is uneven,the demarcation line of the tumor and its degree of definition,RPE disruption on the surface and around the tumor as well as the vascular reflectance and its intensity changes on different spectrum slices.All lesions were analyzed by quantitative MSI indexes including reflectance index(RI)and border definition index BDI)and compared between different pathologies.Results:1.For choroidal osteoma,osseous feature was observed and defined as‘sandwich phenomenon'(homogeneous hyperreflective in 550 nm-beehive heterogenous hyperreflective in 680 nm-homogeneous hyperreflective in 850 nm)in all eyes with inactive choroidal osteoma(100%).Calcifying osseous features,defined as ‘floating island' was observed in all decalcified osteomas(100%).Vascular transmission was observed in eyes with chorioretinal atrophy in the 5eyes with the decalcified osteomas.None of the features above were present in the choroidal hemangiomas.MSI was able to differentiate the inactive portion of the osteoma characterized by geographic hyper-reflective islands with appreciable higher reflectivity border from the active portion,which was featured by increased definition and reflectivity of osteoma soma and border.2.In hemangioma,a reflectance pattern of “isoreflectance in 550 nmhyperf-lectance in 680-decreased reflectance in infrared” was observed in all hemangioma cases(100%).3.In choroidal melanoma,the reflectance showed negative relationship with the spectrum with increased hyporeflectance.4.MSI reflection index(RI)showed different reflection pattern in different choroidal tumors based on histology basis,with osteoma showed increment reflection in relation to spectrums,hemangiomas showed curve-fit reflection pattern with maximum reflection in 680 nm,while choroidal melanoma showed consistently decreased reflection index,but minimally higher than choroidal nevus.The BDI showed MSI is able to reveal the border of both melanocytic and non-melanocytic tumors significantly better than SWAF,NIR-AF,NIR-SLO and FFA(P<0.05).ICGA is the only other en-face imaging tool to delineate the size,distribution of choroidal tumor in addition to MSI.Summary:1.MSI allows the visualization of the characterized presentation different types of choroidal tumors,showing correlation with their specific pathohistology origin.2.Both tumor Reflection Index and Border Definition Index can provide quantatitive diagnosis and differential diagnosis value for choroidal tumors.Conclusion:1.Multispectral Imaging provide accurate diagnostic sensitivity and specificity in pachychoroid spectrum diseases,with CVD as an dependable index for evaluating small and medium choroidal tumors.2.Multispectral Imaging revealed novel features in choroid tumors compared with other multimodal imaging technique,providing new evaluation tool for more accuracy diagnosis.3.The application for MSI in choroidal disorders proved to be valuale which can potentially reduce the dependence on invasive imaging methods. |
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