Особенности изображения структур глаза при томографических методах исследования

PURPOSE: Analysis of technical characteristics of tomographic imaging methods and their impact on study results assessment.METHODS: A retrospective evaluation of optical coherence tomography and Heidelberg retinal tomography data of 50 patients with macular area and optic disc pathology. The study was conducted using Nidek optical coherence tomography device and HRT-II retinal tomography device. Technical characteristics of obtained images, such as brightness, contrast, chromaticity, their interpretation and their impact on the diagnostic and treatment process were studied.RESULTS: While analyzing optical coherence tomography and Heidelberg retinal tomography results for all of 50 patients (100%) we detected problems related to image quality. They are defined by specifications of the monitor and printer, characteristics of computer graphic, image visualization problems. Recommended display resolution is 1280×800 dpi or higher. Correct color reproduction of the image depends on the output resolution of the printer. Visualization of a three-dimensional object on a plane is currently under development. The process of transforming a 3D-object into 2D-graphics is often accompanied by software errors related to polygon conversion, as well as object «smoothing» and mapping when transferring it into a planar model. These technical issues do not have a significant impact on eye structures imaging in tomography studies. However, they may lead to inaccuracies in the assessment of morphometric parameters of the intraocular structures, which is significant in determining the dynamics of pathological processes.CONCLUSION: Ophthalmologists studying ocular tomography results should have a clear understanding of possible technical errors and their causes. Computer diagnostic methods should be regarded as auxiliary. We recommend giving preference to clinical examination methods for diagnosis specification and assessment of the pathological process dynamics.ЦЕЛЬ. Анализ технических особенностей формирования изображения, полученного с помощью томографических методов исследования, и их влияние на оценку результатов исследования.МЕТОДЫ. Проведена ретроспективная оценка качества данных оптической когерентной томографии (ОКТ) и гейдельбергской ретинальной томографии (HRT) у 50 пациентов, имеющих патологию макулярной зоны и диска зрительного нерва. Исследование проводилось на оптическом когерентном томографе Nidek и гейдельбергском ретинальном томографе HRT-II. Изучались технические особенности полученных изображений, такие как яркость, контрастность, цветность, их интерпретация и влияние на диагностический и лечебный процесс.РЕЗУЛЬТАТЫ. При анализе результатов ОКТ и HRT у всех 50 пациентов (100%) выявлены проблемы, связанные с качеством изображения. Они определяются техническими характеристиками монитора и принтера, особенностями компьютерной графики, проблемами визуализации изображения. Рекомендуемым для монитора является разрешение от 1280×800 ppi и выше. Корректная цветопередача изображения во многом зависит от выходного разрешения принтера. Визуализация трехмерного объекта на плоскости в настоящее время находится в стадии разработки. Механизмы трансформации 3D-объекта в 2D-графику имеют программную ошибку, связанную с преобразованием полигонов, механизмом «сглаживания» и механизмом «картирования» объекта при переводе его в плоскостную модель. Перечисленные технические проблемы не оказывают значительного влияния на изображение структур глаза при томографических исследованиях. Однако возможны неточности в оценке морфометрических параметров внутриглазных структур, что существенно при определении динамики патологических процессов.ЗАКЛЮЧЕНИЕ. Врачи-офтальмологи, изучающие результаты томографических исследований структур глаза, должны иметь четкое представление о возможных технических ошибках и их причинах. Компьютерные методы исследования следует расценивать как вспомогательные. При уточнении диагноза или динамики патологического процесса рекомендуется отдавать предпочтение клиническим методам осмотра

Роль индексов компьютерной периметрии в оценке стадий глаукомного процесса

Purpose: To study the role of Octopus computer visual field indices in assessing the stages of the glaucomatous process. Successful treatment of primary open-angle glaucoma (POAG) largely depends on the possibility of reliable control of its effectiveness. The system of POAG early detection and monitoring has significant problems: insufficient clinical coverage of the population, poor quality of patients’ examination at the outpatient level. Standard automated perimetry (SAP) is the golden standard in glaucoma diagnosis and is suitable for a life-long clinical examination of POAG patients. Currently, ophthalmologists do not fully use all the features of this method to determine the stages of POAG.Methods: The study included 150 patients with POAG (284 eyes). According to the results of the study in 102 patients with POAG (193 eyes), exclusion criteria that affect the reliability of SAP indicators were identified The results were evaluated in 48 patients (91 eyes) with POAG diagnosed at least 2 years prior. This group included 27 women (56.3%) and 21 men (43.7%), the average age of patients was 64±10.2 (σ=0.036). The control group consisted of 26 people (52 eyes) — 16 women (61.5%) and 10 men (38.5%). The average age of these subjects was 61±9.0 years. (σ=0.030). All patients underwent a study of the central visual field on the Octopus-101 perimeter (Switzerland), G2 program (glaucomatous test).Results: The corrected loss variance index (СLV) of the Octopus computer visual field analyzer is the most important for determining of the stage of glaucoma. The СLV index less than 8 dB is found in patients without glaucoma. The CLV index interval from 8.1 dB to 19.0 dB corresponds to stage I of POAG, from 19.1 dB to 36.0 dB — to stage II of POAG and the CLV index value of more than 36.1 dB corresponds to stage III of POAG.Conclusion: Glaucoma stage of can be determined not only by the location and depth of the central visual field loss but also based on the evaluation of statistical indicators available in a number of models of automated perimeters. Based on that, we propose a screening method for glaucoma stage assessment in outpatient clinic conditions.Цель. Изучить роль индексов компьютерного анализатора поля зрения «Octopus» в оценке стадий глаукомного процесса. Успешное лечение первичной открытоугольной глаукомы (ПОУГ) во многом зависит от возможности надежного контроля его эффективности. Система раннего выявления и мониторинга ПОУГ имеет существенные проблемы: недостаточный охват населения диспансеризацией, низкое качество осмотра больных с ПОУГ на уровне амбулаторно-поликлинического звена. Стандартная автоматизированная периметрия (SAP) является «золотым» стандартом в диагностике глаукомы и целесообразна при пожизненной диспансеризации больных ПОУГ. До настоящего времени практикующие офтальмологи не в полной степени используют все возможности этого метода для определения стадий ПОУГ.Методы. В исследование принимали участие 150 больных ПОУГ (284 глаза). По результатам исследования у 102 пациентов (193 глаза) были определены критерии исключения, влияющие на достоверность показателей SAP. Полученные результаты оценивались у 48 больных (27 (56,3%) женщин, 21 (43,7%) мужчина; средний возраст 64±10,2 года (σ=0,036); 91 глаз) с ПОУГ сроком не менее 2-х лет. В контрольную группу вошли 26 человек (52 глаза) — 16 (61,5%) женщин; 10 (38,5%) мужчин; средний возраст 61±9,0 лет (σ=0,030). Всем больным проводилось исследование центрального поля зрения на периметре Octopus-101 (Швейцария) по программе G2 (глаукомный тест).Результаты. Наиболее значимым для определения стадии глаукомы является индекс корректированной вариабельности дефектов (СLV) компьютерного анализатора поля зрения Octopus. Значение показателя СLV менее 8 дБ определяет больных, не страдающих глаукомой. Интервал СLV от 8,1 дБ до 19,0 дБ соответствует I стадии ПОУГ, от 19,1 дБ до 36,0 дБ — II стадии ПОУГ и показатель СLV более 36,1 дБ — соответствует III стадии ПОУГ.Заключение. Определение стадии глаукомы можно проводить не только по локализации и глубине скотом в центральном поле зрения, но и на основе оценки статистических индексов, имеющихся в ряде моделей автоматизированных периметров. На этой основе предложен скрининговый метод определения стадии глаукомы, актуальный в условиях амбулаторно-поликлинического звена офтальмологической службы

Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets

This document is the Technical Design Report covering the two large spectrometer magnets of the PANDA detector set-up. It shows the conceptual design of the magnets and their anticipated performance. It precedes the tender and procurement of the magnets and, hence, is subject to possible modifications arising during this process.Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski, Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy), Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy

Charge separation relative to the reaction plane in Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm NN}}= 2.76 TeV

Measurements of charge dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudo-rapidity range $|\eta| < 0.8$ are presented as a function of the collision centrality, particle separation in pseudo-rapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge dependent azimuthal correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286

A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE

In this small note we are concerned with the solution of Forward-Backward Stochastic Differential Equations (FBSDE) with drivers that grow quadratically in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem is a comparison result that allows comparing componentwise the signs of the control processes of two different qgFBSDE. As a byproduct one obtains conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio

Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR

Simulation results for future measurements of electromagnetic proton form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, $\textit{i.e.}$ $\bar p p \to \pi^+ \pi^-$, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance

Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at s=0.9\sqrt{s}=0.9, 2.76 and 7 TeV

Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at $\sqrt{s}=0.9$, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with $p_{\rm T}\geq0.5$ GeV/c in $|\eta|\leq0.8$. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity ($N_{\rm ch}$) is reported for events with different $p_{\rm T}$ scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low $N_{\rm ch}$, whereas the event generators show the opposite tendency. The combined study of the sphericity and the mean $p_{\rm T}$ with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16, published version, figures from http://aliceinfo.cern.ch/ArtSubmission/node/308

Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at sNN\sqrt{s_{NN}} = 5.02 TeV

Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7 $< p_{\rm{T}, assoc} < p_{\rm{T}, trig} <$ 5.0 GeV/$c$ is examined, to include correlations induced by jets originating from low momen\-tum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range $|\eta|<0.9$. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton--parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p-Pb collisions. Further, the number scales in the intermediate multiplicity region with the number of binary nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/161

Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider

Measurements of multi-particle azimuthal correlations (cumulants) for charged particles in p-Pb and Pb-Pb collisions are presented. They help address the question of whether there is evidence for global, flow-like, azimuthal correlations in the p-Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p-Pb collisions. However, when a $|\Delta \eta|$ gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high-multiplicity, indicating the presence of global azimuthal correlations. The Pb-Pb values are higher than the p-Pb values at similar multiplicities. In both systems, the second harmonic four-particle cumulants exhibit a transition from positive to negative values when the multiplicity increases. The negative values allow for a measurement of $v_{2}\{4\}$ to be made, which is found to be higher in Pb-Pb collisions at similar multiplicities. The second harmonic six-particle cumulants are also found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find $v_{2}\{4\} \simeq v_{2}\{6\}\neq 0$ which is indicative of a Bessel-Gaussian function for the $v_{2}$ distribution. For very high-multiplicity Pb-Pb collisions, we observe that the four- and six-particle cumulants become consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and Pb-Pb are measured. These are found to be similar for overlapping multiplicities, when a $|\Delta\eta| > 1.4$ gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87

Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR

The possibility of measuring the proton electromagnetic form factors in the time-like region at FAIR with the \PANDA detector is discussed. Detailed simulations on signal efficiency for the annihilation of $\bar p +p$ into a lepton pair as well as for the most important background channels have been performed. It is shown that precision measurements of the differential cross section of the reaction $\bar p +p \to e^++ e^-$ can be obtained in a wide angular and kinematical range. The individual determination of the moduli of the electric and magnetic proton form factors will be possible up to a value of momentum transfer squared of $q^2\simeq 14$ (GeV/c)$^2$. The total $\bar p +p\to e^++e^-$ cross section will be measured up to $q^2\simeq 28$ (GeV/c)$^2$. The results obtained from simulated events are compared to the existing data. Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations, 4 tables, 9 figure