Slit Scanning Research Articles

Corneal Thickness Measurement Using Orbscan, Pentacam, Galilei, and Ultrasound in Normal and Post-Femtosecond Laser In Situ Keratomileusis Eyes

To compare corneal pachymetry assessment using slit scanning imaging (Orbscan), rotating Scheimpflug imaging (Pentacam), dual Scheimpflug system (Galilei), and ultrasound pachymetry in normal and post-femtosecond (FS) laser in situ keratomileusis (LASIK) eyes. Sixty eyes of 60 patients were enrolled for this study, which consisted of 30 unoperated eyes (normal corneas) and 30 eyes after FS-LASIK (post-LASIK corneas). Central corneal thickness was measured sequentially using Orbscan II, Pentacam, Galilei, and ultrasound pachymetry, and the average value of measurements obtained by the 4 different methods were compared in each group. In normal corneas, corneal thickness measurements were not different by all 4 methods [P = 0.202, 1-way analysis of variance (ANOVA)]. In post-LASIK corneas, the measurement was significantly different among those achieved by 4 methods (P < 0.001, 1-way ANOVA). Orbscan measurement was thinner than those yielded by Galilei, Pentacam, or ultrasound pachymetry with average of 47.7, 38.5, and 34.4 μm, respectively (all P values < 0.001, 1-way ANOVA and the Tukey multiple comparisons test) in post-LASIK corneas. Orbscan, Pentacam, and Galilei measurements showed good agreement with ultrasound pachymetry data in both groups, except Orbscan data in post-LASIK corneas showed a statistically significant difference from ultrasound pachymetry measurements (P value = 0.001, 1-way ANOVA and the Tukey multiple comparisons test). Any of central corneal thicknesses obtained by all 4 measurement modalities might be acceptable before refractive surgery. However, in post-FS-LASIK eyes, measurements using Orbscan were thinner than those obtained with other modalities; in contrast, those with Pentacam or Galilei were comparable with ultrasound pachymetry.

Keratoconus and Keratoectasia: Advancements in Diagnosis and Treatment

Keratoconus and Keratoectasia: Advancements in Diagnosis and Treatment

A Review of Full-Body Radiography in Nontraumatic Emergency Medicine

This paper reports on the application of full-body radiography to nontraumatic emergency situations. The Lodox Statscan is an X-ray machine capable of imaging the entire body in 13 seconds using linear slit scanning radiography (LSSR). Nontraumatic emergency applications in ventriculoperitoneal (VP) shunt visualisation, emergency room arteriography (ERA), detection of foreign bodies, and paediatric emergency imaging are presented. Reports show that the fast, full-body, and low-dose scanning capabilities of the Lodox system make it well suited to these applications, with the same or better image quality, faster processing times, and lower dose to patients. In particular, the large format scans allowing visualisation of a greater area of anatomy make it well suited to VP shunt monitoring, ERA, and the detection of foreign bodies. Whilst more studies are required, it can be concluded that the Lodox Statscan has the potential for widespread use in these and other nontraumatic emergency radiology applications.

Optimizations of transverse projected emittance at the photo-injector test facility at DESY, location Zeuthen

High brightness electron sources for linac based short-wavelength free-electron lasers are developed and optimized for small transverse projected emittance at the photo-injector test facility at DESY, location Zeuthen (PITZ). A major part of the measurement program at PITZ is dedicated to transverse phase space optimization in order to fulfill the requirements of the European X-ray free-electron laser (European XFEL). A laser-driven RF-gun, treated with a dry-ice sublimation-impulse cleaning technique, a new photocathode laser system allowing short rise and fall times of the flat-top temporal distribution as well as several new diagnostic components have been installed at PITZ in 2008. The electrons generated via the photo-effect at a cesium telluride (Cs2Te) cathode are accelerated by a 1.6 cell L-band RF-gun cavity with a maximum accelerating gradient at the cathode of about 60MV/m. The transverse projected emittance is measured using a single slit scan technique. In the 2008–2009 run period, a detailed characterization of the projected transverse emittance was performed at different operating conditions. Optimizations and measurement results as well as simulation predictions of the transverse projected emittance for bunch charges of 1, 0.5, 0.25 and 0.1nC are presented and discussed in this paper. The geometric mean of the normalized projected rms emittance in both transverse directions for an electron bunch charge of 1nC was measured to be 0.89±0.01mmmrad for a 100% rms phase-space distribution.

Modeling of a slit-scan-type aerial image measurement sensor used for optical lithography

Theoretical modeling of a slit-scan-type aerial image measurement sensor used for optical lithography is presented. Slit transmission properties are fully represented by the slit transfer function in terms of incident and scattering angles of light, which is then incorporated into the scheme of a partially coherent imaging formula to obtain an expression for image profiles measured by slit scanning. As an exemplary case, we analyze the influence of a 100 nm width slit used in an ArF lithography system. To understand the mechanism of image profile changes by slit transmission, we focus on frequency transfer characteristics of sinusoidal patterns.

Standardization of Corneal Haze Measurement in Confocal Microscopy

Corneal stromal haze cannot be compared in longitudinal studies or across laboratories without standardization. In this study, a method was devised of standardizing image brightness in confocal microscopy of the cornea. Thirty-six normal corneas of 18 untreated volunteers and 35 corneas of 18 patients 3 years after LASIK were examined by slit scanning confocal microscopy. The mean image intensity of each frame was adjusted for daily variations in sensitivity of the microscope by using scans through a solution of Amco Clear (GSF Chemicals, Columbus, OH). Adjusted image intensities were expressed in scatter units (SU), representing the concentration of Amco Clear that produced the same intensity as the image. The intensity from the stroma in corneas after LASIK was compared to that in untreated corneas by using generalized estimating equation models. In the untreated corneas, image brightness was 1079 ± 242 and 758 ± 142 SU in the anterior and mid stroma, respectively. Three years after LASIK, image intensity in the flap was 740 ± 186 SU, approximately 30% lower than in corresponding stroma of the untreated corneas (P < 0.001). At mid stroma, brightness was 715 ± 117 SU after LASIK, and was not significantly different from brightness in untreated corneas (P = 0.26). Clinical confocal microscopy provides a high-resolution measurement of corneal haze, and Amco Clear provides a means of standardizing these measurements. This method can detect subtle decreases in haze in the corneal flap 3 years after LASIK and could be used to examine changes in haze after lamellar keratoplasty.

Detection of Toric intraocular lens misalignment by digital photograph

Background Toric intraocular lens (Toric IOL) is a well accepted method of correct of corneal astigmatism.Axial misalignment,including the error of intraocular lens alignment during surgery and rotation of Toric IOL,is the main barrier to the precise alignment of Toric intraocular lenses.Therefore,the angle of axial misalignment is a main index to evaluate the effectiveness of Toric IOL implantation.Objective The present study is to describe a method of precisely detecting Toric IOL misalignment using postoperative digital photograph.Methods A measuring template (polar coordinates) was constructed using Adobe Photoshop software.Minimum graduate to detect the Toric axis was 1° (maximum error 0.5°).The clinical data of 24 eyes undergone Toric IOL implantation was retrospectively analyzed.Corneal astigmatism was detected by rotating Scheimpflug camera (Pentacam) or slit scan (Orbscan).Digital retro illumination picture was photographed after mydriasis.The picture was analyzed by our derived template.The steepest corneal axis and the axis of Toric IOL were then determined.The misalignment of Toric IOL was determined as the angle between the steepest corneal axis and the axis of Toric IOL.Misalignment of Toric IOL and its distribution were analyzed by statistical means.Results A method using polar coordinates and digital photo to precisely detect Toric IOL misalignment was derived.Mean Toric IOL misalignment was 10.93±6.90 degrees (0-24 degrees) in the 24 cases.The axial misalignment in all of cases were within 25 degrees,including clockwise in 14 eyes(58.33%),anticlockwise in 10 eyes (41.67%).In this study,the misalignment angle of 4 eyes were within 5 degrees;11 eyes were 5 to 10 degrees;1 eye was 10 to 15 degrees;6 eyes were 15 to 20 degrees;2 eyes were 20 to 25 degrees.Conclusion The method is feasible to the direction of Toric IOL misalignment in clinic. Key words: digital photograph analysis; Toric intraocular lens; misalignment; corneal astigmatism

Corneal Sensitivity and Slit Scanning In Vivo Confocal Microscopy of the Subbasal Nerve Plexus of the Normal Central and Peripheral Human Cornea

To determine the subbasal nerve density and tortuosity at 5 corneal locations and to investigate whether these microstructural observations correlate with corneal sensitivity. Sixty eyes of 60 normal human subjects were recruited into 1 of 3 age groups, group 1: aged <35 years, group 2: aged 35-50 years, and group 3: aged >50 years. All eyes were examined using slit-lamp biomicroscopy, noncontact corneal esthesiometry, and slit scanning in vivo confocal microscopy. The mean subbasal nerve density and the mean corneal sensitivity were greatest centrally (14,731 +/- 6056 microm/mm and 0.38 +/- 0.21 millibars, respectively) and lowest in the nasal mid periphery (7850 +/- 4947 microm/mm and 0.49 +/- 0.25 millibars, respectively). The mean subbasal nerve tortuosity coefficient was greatest in the temporal mid periphery (27.3 +/- 6.4) and lowest in the superior mid periphery (19.3 +/- 14.1). There was no significant difference in mean total subbasal nerve density between age groups. However, corneal sensation (P = 0.001) and subbasal nerve tortuosity (P = 0.004) demonstrated significant differences between age groups. Subbasal nerve density only showed significant correlations with corneal sensitivity threshold in the temporal cornea and with subbasal nerve tortuosity in the inferior and nasal cornea. However, these correlations were weak. This study quantitatively analyzes living human corneal nerve structure and an aspect of nerve function. There is no strong correlation between subbasal nerve density and corneal sensation. This study provides useful baseline data for the normal living human cornea at central and mid-peripheral locations.

Detection of Urinary Stones at Reduced Radiation Exposure: A Phantom Study Comparing Computed Radiography and a Low-Dose Digital Radiography Linear Slit Scanning System

In this experimental study we assessed the diagnostic performance of digital linear slit scanning radiography compared with computed radiography (CR) for the detection of urinary calculi in an anthropomorphic phantom imitating patients weighing approximately 58-88 kg. Compared with CR, linear slit scanning radiography is superior for the detection of urinary stones and may be used for pretreatment localization and follow-up at a lower patient exposure.

Real-time slit scanning microscopy in the meridional plane

The standard microscope architecture around which confocal microscopes are built imposes fundamental restrictions on the speed with which images (three-dimensional data sets) can be obtained. Commercially available slit scanning confocal microscopes are able to produce optically sectioned images at frame rates well in excess of 100 Hz. However only the focal (x-y) plane can be imaged at this speed. To image a volume specimen it is necessary to physically change the distance between the objective lens and the specimen. This refocusing process is often necessarily slow and represents a bottleneck to the speed of image acquisition. We describe the construction of a slit scanning confocal microscope based on what we know to be a novel microscope architecture, which permits images of other planes and, particular, the meridional (x-z) plane to be acquired in real time.

Orbscan Evaluation of Corneal Power after Myopic PRK: Placido Disc-Based vs Scanning Slit Topography

Purpose To compare Placido disc-based and scanning slit topography in the evaluation of corneal power changes after PRK. Methods The changes in corneal power, evaluated with an Orbscan II utilizing both Placido disc-based and Scanning Slit topography, before and 1, 3 and 6 months after PRK were compared with refractive changes in 109 individuals (149 eyes) who underwent photorefractive keratectomy (PRK) with a sphero equivalent refraction, calculated at the corneal apex, ranging from -0.25 to -12 D (mean -4.58±2.54 D). Results 1,3 and 6 months refractive changes showed a good correlation with changes in BFS (r 2=0.64, r 2= 0.53, r 2= 0.62, respectively); in Sim K's (r 2= 0.77, r 2= 0.8, r 2= 0.78, respectively) in Mean Power 3 mm (r 2= 0.81, r 2= 0.88, r 2= 0.87, respectively) in Mean Power 5 mm (r 2= 0.68, r 2= 0.78, r 2= 0.78, respectively) in Anterior Mean Power 3 mm (r 2= 0.88, r 2= 0.85, r 2= 0.85, respectively) in Anterior Mean Power 5 mm (r 2= 0.75, r 2= 0.7, r 2= 0.75, respectively) in Total Mean Power 3 mm (r 2= 0.75, r 2= 0.71, r 2= 0.79, respectively) in Total Mean Power 5 mm (r 2= 0.75, r 2= 0.71, r 2= 0.78, respectively). However, all differences were statistically significant ( P<0.001). Conclusion The data obtained with the scanning slit system seem to be more reliable, but need correcting factors to improve their precision.

In vivo confocal microscopy, an inner vision of the cornea – a major review

The demands of modern ophthalmology have evolved from descriptive findings from the slit lamp to in vivo assessment of cellular level changes. Nowadays, the latter can be provided by in vivo confocal microscopy. This article gives an overview of confocal principles using tandem scanning, scanning slit and laser scanning techniques used in ophthalmology. The main part of the paper describes the clinical applications emphasizing the anatomy of the normal and pathological cornea, and illustrates side-effects of topical medication, contact lens wear, cross-linking and refractive surgery. Finally, a summary about experimental applications, including animal studies, surface characterization and volume rendering as well as future developments, is given.

Improved sectioning in a slit scanning confocal microscope

We describe a simple implementation of a slit scanning confocal microscope to obtain an axial resolution better than that of a point-scanning confocal microscope. Under slit illumination, images of a fluorescent object are captured using an array detector instead of a line detector so that out-of-focus light is recorded and then subtracted from the adjacent images. Axial resolution after background subtraction is 2.2 times better than the slit confocal resolution, and out-of-focus image suppression is calculated to attenuate with defocus faster by 1 order of magnitude than in the point confocal case.

Radial Velocities of Stars in the Galactic Center

We present results from K-band slit scan observations of a ~20'' × 20'' region of the Galactic center (GC) in two separate epochs more than 5 years apart. The high-resolution (R = λ/Δ λ ≥ 14,000) observations allow the most accurate radial velocity and acceleration measurements of the stars in the central parsec of the Galaxy. Detected stars can be divided into three groups based on the CO absorption band heads at ~2.2935 μm and the He II lines at ~2.0581 and ~2.112, 2.113 μm: cool, narrow-line hot, and broad-line hot. The radial velocities of the cool, late-type stars have approximately a symmetrical distribution with its center at ~–7.8 ± 10.3 km s−1 and a standard deviation ~113.7 ± 10.3 km s−1. Although our statistics are dominated by the brightest stars, we estimate a central black hole mass of (3.9 ± 1.1) × 106 M☉, consistent with current estimates from complete orbits of individual stars. Our surface density profile and the velocity dispersion of the late-type stars support the existence of a low-density region at the Galactic center suggested by earlier observations. Many hot, early-type stars show radial velocity changes higher than maximum values allowed by pure circular orbital motions around a central massive object, suggesting that the motions of these stars greatly deviate from circular orbital motions around the Galactic center. The correlation between the radial velocities of the early-type He I stars and their declination offsets from Sagittarius A* suggests that a systematic rotation is present for the early-type population. No figure rotation around the Galactic center for the late-type stars is supported by the new observations.

Spectropolarimetric Observation of an Emerging Flux Region: Triggering Mechanisms of Ellerman Bombs

A high spatial resolution observation of an emerging flux region (EFR) was made using a vector magnetograph and a Hα Lyot filtergraph with the Domeless Solar Telescope at Hida Observatory on 2006 October 22. In Hα wing images, we could see many Ellerman bombs (EBs) in the EFR. Observations in two modes, slit scan and slit fixed, were performed with the vector magnetograph, along with the Hα filtergraph. Using the Hα wing images, we detected 12 EBs during the slit scan observation period and 9 EBs during the slit fixed observation period. With the slit scan observation, we found that all the EBs were distributed in the area where the spatial gradient of vertical field intensity was large, which indicates the possibility of rapid topological change in the magnetic field in the area of EBs. With the slit fixed observation, we found that EBs were distributed in the areas of undulatory magnetic fields, in both the vertical and horizontal components. This paper is the first to report the undulatory pattern in the horizontal components of the magnetic field, which is also evidence for emerging magnetic flux triggered by the Parker instability. These results allow us to confirm the association between EBs and emerging flux tubes. Three triggering mechanisms for EBs are discussed with respect to emerging flux tubes: 9 out of 21 EBs occurred at the footpoints of emerging flux tubes, 8 occurred at the top of emerging flux tubes, and 4 occurred in the unipolar region. Each case can be explained by magnetic reconnection in the low chromosphere.

Radiation dose from a linear slit scanning X-ray machine with full-body imaging capabilities

Doses for a range of examinations and views using digital X-ray equipment with full-body linear slit scanning capabilities (Statscan) have been compared with those from other published studies. Entrance doses (free-in-air) were measured using a dosimeter, and effective doses were generated using a Monte Carlo simulator. Doses delivered by the linear slit scanning system were significantly lower than those from conventional X-ray equipment. Effective doses were between 9 and 75% of the United Nations Scientific Committee Report on the Effects of Ionising Radiation doses for standard examinations. This dose reduction can be explained by the properties of linear slit scanning technology, including low scatter, beam geometry, the use of a digital detector and the use of higher than usual tube voltages.

Korneale Topographie

Various diagnostic procedures have been developed for analyzing the corneal surface. Corneal topographical measurements can be performed by classic Placido disc topographers and tomographers creating three-dimensional corneal models from cross-sectional images. Using a slit scanning system or the Scheimpflug technique additional information about the anterior segment can be obtained. New systems give us a wide range of diagnostic tools. Beside the measurement of the corneal anterior and posterior surfaces and point-to-point-pachymetry they enable analysis of corneal aberrations and measurement of the whole anterior segment, including the anterior chamber and the position of implants, pupil diameter, horizontal white-to-white and the kappa angle. Densitometry, statistical programs for the evaluation of corneal pathology and assistance with intraocular lens calculation following excimer laser treatment are further options available. This article is intended to give an overview of the principles and limitations of the various diagnostic systems.

ＣＴ撮像系におけるスライス面の位置と方向に対する解像力特性の評価

Analysis of the detailed physical property in CT system is important in an understanding of a clinical image. In this study, we evaluated resolution power property about the positions and direction for in-plane in CT system. The indexes of the resolving power property of CT images were measured by MTFs using the thin metal wire (diameter of 0.2 mm). We measured the positions of the iso-center and the off-center (32 mm, 64 mm, 96 mm, 128 mm) in in-plane. One-dimensional MTFs for the X-direction and Y-direction were calculated by the numerical slit scanning method. Then, MTF was calculated from the corresponding direction. As a result, when a filter kernel of high resolutions (B70) is used in the position of 128 mm, the resolution of X-direction was inferior to the Y-direction about 30% (at the MTF-value of 0.5 cycles/mm). Moreover, the resolution of X-direction at the position of 128 mm was inferior to the center about 33% (at the MTF-value of 0.5 cycles/mm). The resolving power property of in-plane in CT system was decreased in the calculation from the numerical slit that becomes perpendicular to the direction of centrifugal and, decreased proportionately with the distance from the center. Also, the resolutions along the centrifugal direction fell off remarkably at the peripheral area. And also, it turned out that the declining trend becomes larger, when the filter function for high-resolving power that is adapted for lungs is used.

不等温体热膨胀系数的测量

A new technique is developed to measure the longitudinal thermal expansion coefficient of C/C composite material at high temperature. The measuring principle and components of the apparatus are described in detail. The calculation method is derived from the temperature dependence of the thermal expansion coefficient. The apparatus mainly consists of a high temperature environmental chamber, a power circuit of heating, two high-speed pyrometers, and a laser scanning system. A long solid specimen is resistively heated to a steady high-temperature state by a steady electrical current. The temperature profile of the specimen surface is not uniform because of the thermal conduction and radiation. The temperature profile and the total expansion are measured with a high-speed scanning pyrometer and a laser slit scanning measuring system, respectively. The thermal expansion coefficient in a wide temperature range (1000-3800 K) of the specimen can therefore be obtained. The perfect consistency between the present and previous results justifies the validity of this technique.

Image-converter tubes for lasers and lasers for image-converter tubes (operating experience of the Photoelectronics Department, GPI, RAS)

Work in the field of electron-optical diagnostics of laser-induced rapid processes performed for almost half a century at the Photoelectronics Department at the General Physics Institute, RAS, is summed up. New femtosecond image-converter tubes have been developed, which provide the time resolution no worse than 100 fs in the slit scan (streak) regime, and photoelectron guns have been built for time-resolved studies of electron diffraction. The results of recent studies on manifold (up to fifty-fold) compression of picosecond electron bunches in nonstationary focusing fields are demonstrated.