Raster Lines Research Articles

Evaluation of spectral domain and time domain optical coherence tomography findings in toxoplasmic retinochoroiditis

Purpose:To investigate spectral domain optical coherence tomography (SD-OCT) findings and compare them with time domain (TD)-OCT imaging of macula and retinochoroiditis lesions of patients with toxoplasmosis.Design:Prospective cross-sectional study.Methods:Ten eyes of 10 patients with active toxoplasmic retinochoroiditis were included. Morphologic features from the macula and retinochoroiditis lesions were obtained at baseline and at 6-week follow up. Scan acquisition protocols for TD-OCT included raster and radial lines through the retinochoroiditis lesion, fast macular, and a linear scan from the lesion to the fovea, whereas the acquisition protocols for SD-OCT also included horizontal volume scans at the lesion site and at the macula. Thickness measurements obtained by SD-OCT were analyzed.Results:At baseline, macular serous retinal detachment was observed in five patients; two of them only seen by SD-OCT. Retinochoroidal lesions were 4260 μm distant from the fovea on average (R = 681–7130) and this distance had an indirect correlation to the presence of macular detachment. Epiretinal membrane and vitreo-macular traction were also observed. The posterior hyaloid was not identified in four patients by TD-OCT and only in one by SD-OCT at baseline. Perilesional subretinal fluid was observed in two patients. The median retinal thickness significantly decreased at the retinochoroiditis lesion (P = 0.0004), and all the patients remained with disorganized retinal layers reflectivity at follow up.Conclusion:SD-OCT is a useful tool in the diagnosis of macular changes related with toxoplasmic retinochoroiditis. SD-OCT is superior in evaluating retinal changes associated with ocular toxoplasmosis.

High-Definition Optical Coherence Tomography in a Case of Congenital Hypertrophy of the Retinal Pigment Epithelium

The authors describe the use of high-definition optical coherence tomography (HD-OCT) in a case of congenital hypertrophy of the retinal pigment epithelium. A 40-year-old woman presented with a large flat pigmented lesion in the inferior retinal quadrant of the left eye, which was compatible with congenital hypertrophy of the retinal pigment epithelium. The lesion was studied with HD-OCT (5 line raster and macular cube 512 × 128) and the results were compared with those of the fellow eye. The volume of the cube in the normal eye measured 7.1 mm(3), whereas the volume of the cube with the lesion was 6.7 mm(3). The subfield thickness analysis was 153 μm in the eye with congenital hypertrophy of the retinal pigment epithelium and 188 μm in the fellow eye, showing a difference of 35 μm between the two eyes. Congenital hypertrophy of the retinal pigment epithelium studied with HD-OCT showed loss of the junction layer between the inner and outer segment of photoreceptors and of the outer nuclear layer.

SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHIC FINDINGS IN MYOPIC FOVEOSCHISIS

The purpose of this study was to investigate the sensitivity of various scan modes of spectral-domain optical coherence tomography (SD-OCT) for detecting pathologies that may accompany myopic foveoschisis, which is important for making surgical decisions and planning surgical strategies for myopic foveoschisis. Twenty-one eyes of 18 patients were diagnosed with myopic foveoschisis by SD-OCT. Patients were examined with SD-OCT using both a five-line raster scan and a three-dimensional scan at the same visit. The detection rates of pathologies such as macular hole, epiretinal membrane, retinal vascular microfolds, internal limiting membrane detachment, paravascular microhole, and photoreceptor inner and outer segments defect were compared between modes. The three-dimensional scanning mode of the SD-OCT tended to be superior to both the one-line and five-line raster scanning modes for detecting inner and outer segments, epiretinal membrane, macular hole, paravascular microhole, and internal limiting membrane. The three-dimensional mode had a significantly higher detection rate (71%) of retinal vascular microfolds than both the 1-line (19%, P < 0.01) and 5-line raster scanning modes (33%, P < 0.05). The three-dimensional scan mode of SD-OCT was more sensitive for detecting the pathologies that accompany myopic foveoschisis, providing important information for vitreous surgery.

New Insights Into Intranuclear mRNP Dynamics

Messenger ribonucleoprotein particles (mRNPs) move randomly within the nucleoplasm on their way to the nuclear pore [1]. In interphase the decondensed chromatin of mammalian cells largely governs the structure of the intranuclear environment and therefore has a strong impact on mRNP mobility. The salivary gland cell nuclei of Chironomus tentans harbor giant polytene chromosomes, where chromatin is compact and surrounded by extended regions of nucleoplasm void of chromatin. This allows studying mRNP mobility under conditions, which presumably correspond to that of interchromatin channels in mammalian cell nuclei. In this domain we examined the intranuclear movement of a specific endogenous mRNP, the BR2 mRNP, by high-speed single molecule fluorescence microscopy [2]. mRNP dynamics could be characterized by four diffusion coefficients, 0.015μm2/s, 0.23μm2/s, 0.7μm2/s and 3.7μm2/s, respectively.We now used 2’-O-Me-RNA oligonucleotides and molecular beacons to label the mRNPs in vivo, and studied the mobility of the BR2 mRNPs by complementary state-of-the-art fluorescence microscopy techniques: single molecule tracking, FCS, line scanning FCS and raster image correlation spectroscopy. These quantitative methods revealed that mobility components >3μm2/s were likely due to unbound oligonucleotides. The remaining components were shown to be typical for BR2 mRNP movement with all techniques and labelling approaches used.The BR2 mRNPs moved in a discontinuous manner in the chromatin-free nucleoplasm. That reflects transient interactions between diffusing BR2 mRNPs and submicroscopic intranuclear structures not containing chromatin. To reveal the nature of the transient mRNP immobilization we examined the impact of the nuclear actin-binding protein hrp65-2, as well as hrp65-1 on mRNP mobility. Altogether, our experiments provided a comprehensive view on the intranuclear trafficking of native mRNPs.[1] Gorski SA, Dundr M, T. Misteli. CurrOpinCellBiol. 2006 Jun; 18(3):284-90.[2] Siebrasse JP, Veith R, Dobay A, Leonhardt H, Daneholt B, U. Kubitscheck. PNAS. 2008 Dec 23; 105(51):20291-6.

Spectral domain optical coherence tomography predates fluorescein angiography in diagnosing central serous chorioretinopathy

Dear Editor, Central serous chorioretinopathy (CSCR) is characterized by the development of serous retinal detachment in the macula and is mainly diagnosed by fluorescein angiography that shows one or multiple areas of leakage from the retinal pigment epithelium (RPE) seen as “expanding dot” or “smoke stack” sign.[12] The RPE defect corresponding to the dominant hyperfluorescence in the fluorescein angiogram, is believed to be the cause for serous leakage of fluid into the subretinal space and is seen as a pigment epithelium detachment (PED) on time domain Stratus Optical coherence tomography (OCT).[3] We present a case of CSCR where the spectral domain high-definition (HD) Cirrus OCT (Carl Zeiss Meditec) could diagnose subclinical CSCR before the development of the expanding dot sign on fluorescein angiography. A 40-year-old man was seen with complaints of blurred vision in his left eye with a visual acuity of 20/30 and was diagnosed to be suffering from CSCR in this eye. His right eye was asymptomatic with a visual acuity of 20/20. On fluorescein angiography, multiple areas of hyperfluorescence were seen that were diagnosed as PED. No expanding dot sign was seen at this stage in the right eye [Fig. 1] while the left eye showed multiple hyperfluroscence with late leakage [Fig. 2]. Analysis of the single-layer RPE showed elevations in the corresponding areas [Fig. 3]. A raster line scan of the right eye showed PED with serous retinal detachment [Fig. 4]. Similarly, the left eye showed PED with a serous retinal detachment [Fig. 2]. The patient was under regular follow-up for next few months. Three months later, the patient complained of blurred vision in his right eye (20/30) that now showed an expanding dot sign on fluorescein angiography [Fig. 5]. Repeat analysis of the single RPE layer now showed increased irregularity with bumps in the superior half [Fig. 5].Figure 1: (a and b) Fundus and red-free photograph of the right eye showing mottled appearance superotemporal to the fovea. (c and d) Angiogram during transit and late phase showing hyperfluorescence suggestive of pigment epithelium detachment (arrows). Additionally, an area of punctate hyperfluorescence (solid arrow) is shown with an absence of smoke stack or subretinal fluidFigure 2: (a and b) Fundus photograph and angiogram of left eye showing pigmentry changes and yellowish precipitate, mottled appearance supero-temporal to fovea showing hyperfluorescence (arrows). (c) Additionally, showing multiple areas of pinpoint hyperfluorescence (d). OCT of left eye showing pigment epithelium detachment and subretinal fluidFigure 3: Single layer retinal pigment epithelium scan of right eye on Macular Cube 512 × 128 Combo shows pigment epithelium detachment s (arrows). In addition, the superior part of retinal pigment epithelium layer shows uneven surface with bumps. The inset shows fundus image with scan cube overlayFigure 4: Raster Line scan of right eye passing above the fovea shows pigment epithelium detachment (black arrows), with subretinal fluid (arrowhead). Red arrows demarcate external limiting membrane while yellow arrows shows outer photoreceptor layer. Inset shows OCT slice showing the presence of subretinal fluid (solid arrow)Figure 5: (a and b) Same eye(right eye) 3 months later shows expanding dot sign on fluorescein angiography (arrows). (c). Single layer RPE scan shows more uneven and bumpy surface compared to previous scan in Figure 2. (d). Raster Line scan right eye shows pigment epithelium detachment with subretinal fluidThe diagnosis of CSCR is mainly clinical, aided by fluorescein angiography and OCT. Fluorescein angiography classically shows the leakage of dye from the choroid through a focal RPE defect and its pooling in the subretinal space in acute CSCR. OCT is traditionally used to quantify the amount and extent of the subretinal fluid, demonstrate thickening of the neural retina and is commonly used for monitoring during the follow-up and also for diagnosing the changes in the neurosensory retina that can cause permanent impairment in vision in such eyes.[34] Recently, 3D high-speed OCT has shown to facilitate the understanding of pathophysiologic changes in CSCR.[5] However, this case illustrates that spectral domain HD OCT could pick up the presence of the subretinal fluid and RPE changes even before they could manifest angiographically in CSCR. This indeed may be a better tool for monitoring the asymptomatic eye for the detection of early changes and may obviate the need for fluorescein angiography in selected cases. However, this is only a case report and a larger study is required.

Spontaneous closure of retinal pigment epithelium microrip in the natural course of central serous chorioretinopathy

To study the natural course of changes observed in the retinal pigment epithelium (RPE) on spectral domain OCT transverse and RPE fit C-scans corresponding to the leakage point observed on fundus fluorescein angiograms in central serous chorioretinopathy (CSC). Thirteen patients with acute CSC were prospectively enrolled and followed up for 6 months. All were examined using Zeiss Cirrus HD-OCT Model 4000. Transverse and RPE fit C-scans corresponding to point of leakage were superimposed on an OCT fundus photograph and correlated with the leakage point on a fluorescein angiogram. The RPE alterations observed at the leakage point were noted at presentation and follow-up. Transverse and RPE fit C-scans showed an irregularity of RPE resembling a 'honeycomb' pattern in 11 (85%) eyes at the point corresponding to the fluorescein leakage site. These were observed as pigment epithelium detachment (PED) on Raster line scan. Six of these 11 eyes (54.5%) showed a disruption/breach in the RPE on transverse C-scan and on RPE fit C-scan. All eyes showed a resolution of subretinal fluid with a closure of microrip, and the honeycombed pattern at the leakage site was replaced with RPE hypertrophy. RPE microrips show spontaneous closure in the natural course of CSC.

Morphological changes in the retinal pigment epithelium on spectral-domain OCT in the unaffected eyes with idiopathic central serous chorioretinopathy

To report the changes seen in the retinal pigment epithelium (RPE) morphology in the asymptomatic eyes of patients with idiopathic central serous chorioretinopathy (ICSC) using spectral-domain Cirrus (TM) high-definition optical coherence tomography (HD-OCT). In a prospective case series, 17 consecutive patients with unilateral ICSC underwent spectral-domain Cirrus (TM) HD-OCT scans for both affected and opposite asymptomatic eye. Three-dimensional single-layer RPE map was studied in both eyes for morphological alterations, and findings were correlated with clinical presentation, fluorescein angiogram, and 5 Line raster scan. Additionally, three-dimensional (3D) single-layer RPE maps done in 111 healthy volunteers served as control. In patients with ICSC, 3D single-layer RPE analysis of asymptomatic eyes showed presence of RPE bumps in 16 (94%) eyes and pigment epithelium detachment (PED) in 2 (11.8%) eyes. The 5 Line raster scan was normal in all eyes. Of 222 normal (control) scans, 18 showed RPE bumps and none showed PED. Conclusions 3D single-layer RPE map showed abnormal pattern in the asymptomatic eyes of patients with unilateral ICSC. Spectral-domain optical coherence tomography showed morphologic alterations in retinal pigment epithelium in both eyes of patients with idiopathic central serous chorioretinopathy.

Conservative treatment effects on spinal deformities revealed by surface topography – a critical review of literature

Materials and methods A review of literature has been undertaken to investigate the usefulness of rasterstereography applied to reveal treatment effects of conservative treatment of spinal deformities. In the video rasterstereography (Formetric®system), the whole object is illuminated by a pattern of parallel lines, recorded in a single frame and needing only a short measurement time (40 msec). The automatic image processing consists of the identification of the raster lines and automatic 3-D reconstruction of the back; shape analysis is performed by a computer. Parameters used to compare the short-term effects of the different treatment concepts described were average lateral deformation (root mean square [rms]) with a technical error of 3 mm and average surface rotation (rms) with a technical error of 1,5°.

Comparison of High‐ResolutionTRACEData to Spectroscopic CDS Data for Temperature Determination

In this paper we aim to measure the temperature along a specific coronal loop feature which is located in an active region on the western solar limb. The data are taken from Joint Observing Program 146 and consist of high-cadence TRACE triple-filter images coinciding with sparse raster Coronal Diagnostic Spectrometer (CDS) spectroscopic data. The double filter ratio temperature analysis technique is applied to two sets of TRACE images having a 20 minute time gap resulting in temperatures between 1.0 and 1.3 MK. The CDS sparse raster line intensities are used to create emission measure (EM) loci plots determining temperature values over an overlapping 40 minute observing period. These plots appear to be consistent with a line-of-sight isothermal structure which increases in temperature from ~1.20 to ~1.75 MK over the observing period; in contrast, EM loci plots for nearby background pixels depict multithermal emission. Possible reasons for the difference between the TRACE and CDS results and the implications of this analysis on future observations are discussed.

A photoelectric angular-position sensor

This paper discusses the layout and operating principle of a photoelectric angular-position sensor based on obturation raster coupling with interperiod interpolation of the angle, in which filtering of the spatial spectrum of the images of the raster lines is used to increase the accuracy. The maximum measurement error of the angular position achieved on a prototype of the sensor was ±0.7″.

Imaging and spatial distribution of β-amyloid peptide and metal ions in Alzheimer’s plaques by laser ablation–inductively coupled plasma–mass spectrometry

Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) has been developed as a new strategy for detection and imaging of β-amyloid protein in immunohistochemical sections from the brains of a transgenic mouse model of Alzheimer’s disease. The distribution of β-amyloid deposits in tissue was based on measurement of Eu- and Ni-coupled antibodies. The laser-based methodologies (spot ablation, single line raster, and two-dimensional imaging) were also used to detect and map trace element distributions and thus provide a novel probe for both elemental and protein data. We also report the combination of laser capture microdissection with LA–ICP–MS as an alternative strategy for microanalysis of immunohistochemical sections.

New approach in tool wear measuring technique using CCD vision system

This paper suggests a reliable direct measuring procedure for measuring different tool wear parameters. Modern image processing techniques and machine vision systems today enable direct tool wear measurement to be accomplished in-cycle. The presented system is characterized by its measurement flexibility, high spatial resolution and good accuracy. The system consists of a light source to illuminate the tool, CCD camera, laser diod (used in conjunction with profile deepness assessment) with linear projector, grabber for capturing the picture, and a PC. The technique is specially characterized by its determination of profile deepness with the help of projected laser raster lines on a tool surface. So it has advantage comparing with other techniques, which can measure only 2D profiles. With the technique presented in this paper a 3D image of relief surface can be obtained without having need to employ a very complicated measuring system. All indirect methods like acoustic emission, force measurement, spindle current measurement, vibration sensors, etc. are very time consuming and demand very expensive subsidiary measurement equipment, compared with the method presented here.

Thermal viewer TPV-1M2, with an improved image raster

This paper presents a brief description of the TPV-1M2 compact thermal viewer, with an improved image raster. An analysis is given of the raster created by the LED module of the thermal viewer with optomechanical scanning. The raster is improved by altering the topology of the LED module to provide overlap of the adjacent raster lines.© 2004 Optical Society of America

Thermal strain analysis of an electronics package using the SEM Moiré technique

This paper reports on a study of the scanning electron microscope (SEM) Moiré method. Tests were carried out by rotating the specimen grating slightly with respect to the electron scanning raster lines, to verify that the Moiré images captured were really due to the interference between specimen and reference gratings. The experimental results coincided well with the calculated theoretical values and with small measurement errors. Then, the shear strains experienced by the solder joints of a flip‐chip ball grid array specimen were investigated using the SEM Moiré method. The results were compared with those obtained using the optical Moiré method.

The effect of pixel nonlinearity on cathode-ray tube-based visual acuity tests.

Pixel nonlinearity of a cathode-ray tube (CRT) display can cause differences between the actual image and the nominal image. One of the discrepancies, the anisotropy of interactions between neighboring pixels on the same raster line and between neighboring raster lines, may have an impact on the CRT-based visual acuity test where small horizontal and vertical gaps are used. We evaluated this impact. Two high-quality color CRT monitors were tested. The stimulus target was a black square ring on a white background. White gaps of one stroke width were opened in the middle of the straight sides of the square ring. In a gap width comparison study, the up and down gaps were flanked with a one-pixel band on the left and right side. The pixel value of the bands was varied to determine the luminance that made up and down gaps appear to have the same width as left and right gaps. The comparison was made at 1 and 2 m. In a visual acuity study, horizontal gap (left/right) acuity and vertical gap (up/down) acuity were measured separately at several distances between 8 and 11 m. Similar measurements were made when the monitor was rotated 90 degrees. Gaps with edges that were parallel to raster lines (raster-parallel gaps) appeared wider than gaps with edges that were perpendicular to raster lines (raster-perpendicular gaps). To match the apparent width of the left and right gaps, the two one-pixel bands flanking the up and down gaps required a pixel value that corresponded approximately to a luminance of mid gray, indicating that the apparent width of a four-pixel left or right gap was similar to that of a five-pixel up or down gap. Raster-parallel gaps produced a higher percentage of correct responses than raster-perpendicular gaps in a visual acuity test. When nominal gap widths were equal, left and right gaps produced 10% or more correct responses than up and down gaps at some target sizes, which translated to a two-letter acuity difference. This acuity difference could not be accounted for by uncorrected astigmatism because the anisotropy persisted when the monitor was turned 90 degrees. Pixel nonlinearity of a CRT-display results in an anisotropy of gap width that can be observed at and above visual acuity size. This anisotropy may introduce uncertainties in the results of CRT-based visual acuity tests where gaps of different orientations are used.

Mixed-Signal Architecture for Real-Time Two-Dimensional Live TV Image Restoration

This paper describes novel electronic architecture for a real-time image restoration of live TV signals at live TV frame rates with a latency of two frames. The spatial filtering is obtained from two electronic analog filters, one for the raster lines and one for the columns. The very fast response of analog filters makes possible truly real-time video frame rate performance. The digital part of the system serves the purpose of pipelined parallel data conversion and flow, rather than that of image processing (filtering). This architecture exhibits some very important advantages. It does not need any computational source, it is very fast, and it is quite inexpensive. In addition, such a “parallel analog computer” can be easily incorporated into any complex system with video signal data as a simple “plug-in” between the camera and monitor. An important aspect is that the system carries low digitalization noise, thus yielding good SNR characteristics. The system can perform any kind of separable spatial frequency filtering and can be electronically tuned to obtain exact performance parameters. Because of these advantages, this architecture is promising for a variety of systems such as supermarket multicamera security, military and aerospace vision systems, and medical diagnostics.

Luminance artifacts of cathode-ray tube displays for vision research.

Phosphor persistence, video bandwidth, DC restoration and high-voltage regulation affect the appearance of images presented on cathode-ray tubes (CRTs), potentially resulting in differences between nominal and actual stimuli. We illustrate these effects by measuring physical parameters of horizontal and vertical static and counter-phase flickering gratings, and we illustrate problems for vision research by measuring contrast sensitivity to these gratings. We also measured the extent to which calibration protocols actually result in the monitor being calibrated over its entire area regardless of image size. The results of our physical measurements indicate substantial differences between gratings that nominally differ only as to orientation. Consistent with these differences, our psychophysical measurements indicate different sensitivities when the bars of the gratings are parallel or orthogonal to raster lines, regardless of the retinal orientation of the gratings. The results of our calibration check show that only a small region around the target area of calibration can be regarded as effectively linearized, and only if the size of the test image used during the check is similar to the size of the calibration patch. Overall, our results indicate potentially severe problems with the use of CRTs in vision research, and we discuss some published results that are likely to have been affected by these problems.

An efficient integer-based skeletonization algorithm

The problem of generating vector representation of a raster image has been the question of present interest for decades. Although, there are many approaches to this problem, most of them suffer from sophisticated computations and irrational memory usage. We introduce here a new skeletonization algorithm that is very efficient in terms of time and memory consumption. Starting from the description of our approach to the concept of skeleton on raster grid, we present a comprehensive explanation of the algorithm. Its main idea consists of generating a special polyline for each raster line considering them in top-to-bottom direction; skeleton is constructed from points of these polylines. The skeletons obtained by our algorithm allow the precise reconstruction of the initial raster shapes; therefore they may reflect some artifacts possible on raster grid. For this reason, we also present here two algorithms of simplification and our approach to defects filtering on a stage of skeleton generation. The time of simplification by presented algorithms depends linearly on the number of input points that makes these methods fast and efficient. The paper concludes with performance evaluation and discussion of possible implementations of the introduced techniques.

From Raster to Vectors: Extracting Visual Information from Line Drawings

Vectorisation of raster line images is a relatively mature subject in the document analysis and recognition field, but it is far from being perfect as yet. We survey the methods and algorithms developed to-date for the vectorisation of document images, and classify them into six categories: Hough transform-based, thinning-based, contour-based, run-graph-based, mesh-pattern-based, and sparse-pixel-based. The purpose of the survey is to provide researchers with a comprehensive overview of this technique, to enable a judicious decision while selecting a vectorisation algorithm for a system under development or a newly developed vectorisation algorithm.

A NEW ALGORITHM FOR LINE IMAGE VECTORIZATION

In this paper, a new approach which differentiates from the conventional thinning algorithms in vectorizing a raster line image called maximal inscribing circle (MIC) is used. This region-based vectorization algorithm takes the ensemble of pixels within the line segments collectively as legitimate candidates in deciding the vectorized representation. An iterative procedure is outlined and the criteria for merging short straight line segments into the corresponding curve representation are described. This method cannot only segment the lines and junctions, construct their spatial relationships in a computation efficient manner, but also retain their line width.