SDOCT IMAGE RECONSTRUCTION BY INTERFEROMETRIC SYNTHETIC APERTURE MICROSCOPY

Spectral domain optical coherence tomography(SDOCT)is a noninvasive,cross-sectional imaging technique that measures depth resolved reflectance of tissue by Fourier transforming the spectral interferogram with the scanning of the reference avoided.Interferometric synthetic aperture microscopy(ISAM)is an optical microscopy computed-imaging technique for measuring the optical properties of biological tissues,which can overcome the compromise between depth of focus and transverse resolution.This paper describes the principle of SDOCT and ISAM,which multiplexes raw acquisitions to provide quantitatively meaningful data with reliable spatially invariant resolution at all depths.A mathematical model for a coherent microscope with a planar scanning geometry and spectral detection was described.The two-dimensional fast Fourier transform(FFT)of spectral data in the transverse directions was calculated.Then the nonuniform ISAM resampling and filtering was implemented to yield the scattering potential within the scalar model.Inverse FFT was used to obtain the ISAM reconstruction.One scatterer,multiple scatterers,and noisy simulations were implemented by use of ISAM to catch spatially invariant resolution.ISAM images were compared to those obtained using standard optical coherence tomography(OCT)methods.The high quality of the results validates the rationality of the founded model and that diffraction limited resolution can be achieved outside the focal plane.

GRIN透镜对SDOCT系统中成像质量的影响分析

搭建基于光谱光学相干层析术(SDOCT,spectral domain optical coherence tomography)的内窥成像系统,分析SDOCT的理论分辨率和探测深度。根据近轴子午光线方程,利用矩阵法分析自聚焦GRIN(gradient index)透镜成像原理,设计适用于SDOCT扫描探头的GRIN透镜,聚焦距离为10mm,透镜长度为5.31mm,直径为1.8mm。通过光学传递函数(MTF)对比GRIN透镜和传统球面透镜对成像质量的影响。利用内窥成像系统对洋葱内外表皮样品进行成像,获得3.2mm×0.7mm的层析图像。实验结果表明,利用GRIN透镜聚焦光束时,SDOCT系统的横向分辨率可达8μm,成像质量得到提高。

频域OCT的光学相移器的标定

提出了一种对频域光学相干层析(OCT)系统中压电陶瓷相移器进行标定的方法。该标定法是在用干涉条纹跟踪法初步标定的基础上,用差分光谱法进行精确标定来实现的,可将标定精度提高约6%。在差分频域OCT系统中进行了实验验证,表明该方法能够将频域OCT图像的信噪比提高约10%。

Geographic mapping of choroidal thickness in myopic eyes using 1050-nm spectral domain optical coherence tomography

Purpose:To provide a geographical map of choroidal thickness(CT)around the macular region armong subjects with low,moderate and high myopia.Methods:20 myopic subjects(n=40 eyes)without other identified pathologies participated in this study:20 eyes of≤3 diopters(D)(low myopic),10 eyes between-3 and-6D(moderate myopic),and 10 eyes of≥6D(high myopic).The mean age of subjects was 30.2 years(±7.6 years;range,24 to 46 years).A 1050 nm spectral-domain optical coberence tomography(SD-OCT)system,operating at 120kHz imaging rate,was used in this study to simultaneously capture 3D anatomical images of the choroid and measure intraocular length(IOL)in the subject.The 3D OCT images of the choroid were segmented into superior,inferior,nasal and temporal quadrants,from which the CT was measured,representing radial distance between the outer retinal pigment epithelium(RPE)layer and inner scleral border.Measurements were made within concentric regjons centered at fovea centralis,extended to 5 mm away from fovea at 1 mm intervals in the nasal and temporal directions.The measured IOL was the distance from the anterior cornea surface to the RPE in alignment along the optical axis of the eye.Statistical analysis was performed to evaluate CT at each geographic region and observe the relationship between CT and the degree of myopia.Results:For low myopic eyes,the IOL was measured at 24.619±0.016 mm.The CT(273.85±49.01μm)was greatest under fovea as is in the case of healthy eyes.Peripheral to the fovea,the mean CT decreased rapidly along the nasal direction,reaching a minimum of 180.65±58.25 pum at 5 mm away from the fovea.There was less of a change in thickness from the fovea in the temporal direction reaching a minimum of 234.25±42.27μm.In contrast to the low myopic eyes,for moderate and high myopic eyes,CTs were thickest in termnporal region(where CT=194.94±27.28 and 163±34.89μm,respectively).Like the low myopic eyes,moderate and high myopic eyes had thinnest CTs in the nasal region(where CT=100.84±16.75 and 86.64±42.6μm,respectively)-High myopic eyes had the longest mean IOL(25.983±0.021 mm),while the IOL of moderate myopia was 25.413±0.022 mm(**p<0.001).The CT reduction rate was calculated at 31.28 umn/D(diopter)from low to mod-erate myopia,whilst it is 13.49μm/D from moderate to high myopia.The similar tendency was found for the IOL reduction rate in our study:0.265 mm/D from low to moderate myopia,and 0.137 mm/D from moderate to high myopia.Conclusion:The CT decreases and the IOL increases gradually with the increase of myopic condition.The current results support the theory that choroidal abnormality may play an important role in the pathogenesis of myopic degeneration.

应用频域光学相干断层扫描观察脉络膜厚度研究进展

脉络膜作为外层视网膜主要的营养供应来源，其血管系统的正常结构与功能对于视网膜显得尤为重要，所以观察脉络膜形态有助于临床医生理解许多视网膜脉络膜疾病的病理生理过程。有文献报道SDOCT用于准确测量正常和病理状态下的脉络膜厚度，还可以用于脉络膜疾病治疗后的效果评估。SDOCT为人们研究视网膜脉络膜疾病开辟了一条崭新的路径，随着光学相干断层技术的进一步发展，它将给越来越多眼底疾病的诊断与治疗提供帮助；

频域光学在伽玛刀治疗前后视功能评价中的初步观察

目的通过相干断层扫描(spectral-domain optical coherence tomography,SDOCT)测量retinal nerve fiber layer RNFL,厚度来观察伽玛刀治疗前后视功能的改变。方法适合伽玛刀治疗的患者,经过眼科筛查,在伽玛刀治疗前后行SDOCT检查,记录RNFL厚度改变,并行分组:第一组为肿瘤远离鞍区组;第二组为鞍区肿瘤,视器未接触组;第三组为鞍区肿瘤且视器有接触组。共入选36例患者,共72只眼。女性23例,男性13例,平均年龄47.59岁。结果所有患者治疗前后RNFL厚度及各个象限厚度无统计学差异(P>0.05);3组前后数据统计分析无统计学差异(P>0.05)。第一组患者治疗前象限在正常背景,治疗后无变化;第二组患者治疗前有2例象限异常,为手术后患者,治疗后象限背景无改变;第三组患者治疗前有10例患者有象限异常,治疗后有3例患者出现象限背景改变。结论 SDOCT可以作为伽玛刀治疗鞍区肿瘤患者视功能评价的指标之一。对于视器附近的肿瘤进行伽玛刀治疗是安全的。但是,肿瘤对视器有压迫的患者,包括曾经有较长时间压迫的患者,伽玛刀治疗时剂量给予需谨慎。本组资料样本较少,仍需要更大样本检验。