Ring Imaging Research Articles

Robust keratoconus detection with Bayesian network classifier for Placido-based corneal indices

PurposeTo evaluate in a sample of normal and keratoconic eyes a simple Bayesian network classifier for keratoconus identification that uses previously developed topographic indices, calculated directly from the digital analysis of the Placido ring images. MethodsA comparative study was performed on a total of 60 eyes from 60 patients (age 20–60 years) from the Department of keratoconus of INVISION Ophthalmology clinic (Almería, Spain). Patients were divided into two groups depending on their preliminary diagnosis based on the classical topographic criteria: a control group without topographic alteration (30 eyes) and a keratoconus group (30 eyes). The keratoconus group included all grades except grade IV with excessively distorted corneal topography. All cases were examined using the CSO topography system (CSO, Firenze, Italy), and primary corneal Placido-indices were computed, as described in literature. Finally, a classifier was built by fitting a conditional linear Gaussian Bayesian network to the data, using the 5- and 10-fold cross-validation. For comparison, the original data were perturbed with random white noise of different magnitude. ResultsThe naïve Bayes classifier showed perfect discrimination ability among normal and keratoconic corneas, with 100% of sensibility and specificity, even in the presence of a very significant noise. ConclusionsThe Bayesian network classifiers are highly accurate and proved a stable screening method to assist ophthalmologists with the detection of keratoconus, even in the presence of noise or incomplete data. This algorithm is easily implemented for any Placido topographic system.

638. Comparative Genomics of Mycoplasma pneumoniae Isolated From Children with Pneumonia: South Korea, 2010–2016

BackgroundThis study applied high-throughput whole-genome sequencing (WGS) technologies to investigate the comparative genomics of 30 M. pneumoniae strains isolated from children with pneumonia in South Korea during two epidemics from 2010 to 2016 in comparison with a global collection of 48 Mycoplasma pneumoniae strains which includes seven countries ranging from 1944 to 2017.MethodsA total number of 30 M. pneumoniae strains were selected for whole-genome sequence analysis from two epidemics, 2010–2012 and 2014–2016. Next-generation sequencing (NGS) of all M. pneumoniae strains was performed using the Illumina MiSeq desktop sequencer. Comparative genomic analysis was performed using BLAST Ring Image Generator (BRIG), MAUVE, MAFFT, CLC Phylogeny Module, SnpEff, and Pathosystems Resource Integration Center (PATRIC).ResultsThe 30 Korean strains had approximately 40% GC content and ranged from 815,686 to 818,669 base pairs, coding for a total of 809 to 828 genes. Overall, BRIG revealed 99% to>99% similarity among strains. The genomic similarity dropped to approximately 95% in the P1 type 2 strains when aligned to the reference M129 genome, which corresponded to the region of the p1 gene. MAUVE detected four subtype-specific of which were all hypothetical proteins except for one tRNA insertion in all P1 type 1 strains. eBURST analysis demonstrated two clonal complexes which are accordant with the known P1 typing, with higher diversity among P1 type 2 strains. The phylogenetic tree constructed with 78 genomes including 48 genomes outside Korea, formed three clusters, in which the sequence type 3 strains from Korea were divided into two P1 type 1 clusters.ConclusionThe comparative genomics of the 78 M. pneumoniae strains including 30 strains from Korea by WGS reveals structural diversity and phylogenetic associations, even though the similarity across the strains was very high.Disclosures All authors: No reported disclosures.

Presentación sincrónica de tumor epidermoides intracraneal y absceso cerebral. Reporte de un caso

Introducción: Un paciente con tumor epidermoides intracraneal extradural con presentación sincrónica con absceso cerebral, sin antecedentes de trauma craneal penetrante, no ha sido reportado con anterioridad en la revisión del tema realizada por los autores. Se presenta un caso con estas características y se exponen consideraciones sobre el diagnóstico y el tratamiento. Caso clínico: Paciente femenina, de 48 años de edad, con antecedentes de cefalea crónica y tumor craneal palpable en región frontal izquierda. Los estudios humorales fueron normales. La RNM craneal mostró dos imágenes en anillo yuxtapuestas, extra e intraaxial de forma respectiva. En la cirugía se encontró tumor perlado extradural sin evidencia a la inspección de tumor intradural, se comprobó en el examen histopatológico tumor epidermoides. En los controles imagenológicos posoperatorios se descubrió la persistencia de la lesión intraaxial, en anillo, frontal izquierda. Una segunda cirugía evidenció un absceso cerebral de ubicación subcortical y se efectuó la resección radical. La evolución fue favorable, sin secuelas después de cuatro meses de seguimiento. Conclusiones: Se reportó un caso infrecuente, donde se presentó de forma sincrónica un tumor epidermoides extradural frontal izquierdo y absceso cerebral frontal ipsilateral, sin relación de continuidad ni comunicación fistulosa demostrada en las neuroimágenes ni en la exploración quirúrgica.

MtreeRing: An R package with graphical user interface for automatic measurement of tree ring widths using image processing techniques

Accurate measurements of ring-width series are essential for dendrochronological analyses. We present an R package MtreeRing for ring-width measurements on scanned digital images. A morphological alternate sequential filter is used for noise reduction in the original image. Ring boundaries are determined by the steepest negative slopes in the light reflectance of latewood-earlywood transitions. To automatically identify tree rings, the package provides three alternative methods (watershed-based segmentation, Canny edge detector, and a linear detection algorithm), each with advantages and disadvantages and suited to different wood anatomical features. The user can also manually mark tree rings on species with complex anatomical structures. The arcs of inner-rings and angles of successive inclined ring boundaries are used to correct ring-width series. Differences in ring-width measurements between MtreeRing and WinDENDRO in a given coniferous species (Larix gmelinii) were assessed, and no significant difference between programs was found. Furthermore, the package provides an R-based web application which was developed using the Shiny framework. This beginner-friendly application allows viewing and interacting with tree ring images. It requires no programming experience and can run on either a local computer or a remote server.

An Exo–Kuiper Belt with an Extended Halo around HD 191089 in Scattered Light

Abstract We have obtained Hubble Space Telescope STIS and NICMOS and Gemini/GPI scattered-light images of the HD 191089 debris disk. We identify two spatial components: a ring resembling the Kuiper Belt in radial extent (FWHM ∼ 25 au, centered at ∼46 au) and a halo extending to ∼640 au. We find that the halo is significantly bluer than the ring, consistent with the scenario that the ring serves as the “birth ring” for the smaller dust in the halo. We measure the scattering phase functions in the 30°–150° scattering-angle range and find that the halo dust is more forward- and backward-scattering than the ring dust. We measure a surface density power-law index of −0.68 ± 0.04 for the halo, which indicates the slowdown of the radial outward motion of the dust. Using radiative transfer modeling, we attempt to simultaneously reproduce the (visible) total and (near-infrared) polarized intensity images of the birth ring. Our modeling leads to mutually inconsistent results, indicating that more complex models, such as the inclusion of more realistic aggregate particles, are needed.

Feasibility of Submillisievert CT of the Skeletal Pelvis Using Iterative Reconstruction: A Human Cadaver Study.

OBJECTIVE. The purpose of this study is to investigate the feasibility of submillisievert CT of the skeletal pelvis of human cadavers using a standard-dose protocol and four different reduced-dose protocols reconstructed with filtered back projection (FBP) and iterative reconstruction (IR). MATERIALS AND METHODS. The pelvis of 25 human cadavers was repeatedly examined using different reduced-dose CT (RDCT) protocols with decreasing reference tube current-exposure time products (RDCT protocol 1, 80 mAs; RDCT protocol 2, 60 mAs; RDCT protocol 3, 40 mAs; and RDCT protocol 4, 10 mAs) and a tube voltage of 120 kV. A standard-dose CT (SDCT) protocol (reference tube current-exposure time product, 100 mAs; tube voltage, 120 kV) used for the same cadavers served as the reference. Raw data were reconstructed using FBP and two increasing levels of IR (IR levels 4 and 6). The image quality and diagnostic acceptability of images of the anterior pelvic ring, acetabulum, and posterior pelvic ring including the sacroiliac joints were evaluated on a 5-point scale. A mixed-effects model for repeated measures was performed. RESULTS. The image quality of all anatomic structures was rated as diagnostically acceptable for all protocols reconstructed with IR, except for 11 cadavers that were imaged using RDCT protocol 4. For reconstructions with FBP, image quality was generally rated lower and was diagnostically acceptable only for images obtained using SDCT and RDCT protocol 1 and 2. RDCT protocol 3 with IR was the RDCT protocol with the largest reduced dose still allowing diagnostically acceptable image quality for all anatomic structures in all cadavers. Compared with SDCT, the RDCT protocols resulted in significantly reduced mean (± SD) effective radiation doses (SDCT, 2.0 ± 0.7 mSv; RDCT protocol 1, 1.6 ± 0.6 mSv; RDCT protocol 2, 1.2 ± 0.4 mSv; RDCT protocol 3, 0.8 ± 0.3 mSv; and RDCT protocol 4, 0.3 ± 0.1 mSv; p = 0.001). CONCLUSION. Diagnostically acceptable submillisievert CT of the skeletal pelvis is feasible using IR. To adhere to the ALARA (as low as reasonably achievable) principle, submillisievert pelvic CT protocols combined with IR should be implemented as part of routine clinical practice.

Particle identification system for the Super Charm–Tau Factory at Novosibirsk

The Super Charm–Tau (SCT) Factory is a proposed electron–positron collider in Novosibirsk with a peak luminosity of 1035cm−1s−1 operating in the energy range between 2and 6 GeV. The interaction region should be equipped by an excellent universal particle detector meeting the requirements of broad physics program of the experiment. Research and development for all detector subsystems is currently underway. Particle identification (PID) system of the detector is required to provide the state-of-the-art level of μ/π separation for the particle momenta up to 1.2GeV∕c. The following options for the PID system are considered in this paper: focusing aerogel ring imaging Cherenkov (FARICH) detector composed of 4-layer aerogel tiles, threshold Cherenkov counters based on aerogel shifter photomultiplier (ASHIPH), and time-of-flight (ToF) detector combined with the time-of-propagation (ToP) approach providing a time resolution better than 30ps. Assessment of the charged particle separation performance for these options based on simulation and prototype tests results is presented.

Using Muon Rings for the Calibration of the Cherenkov Telescope Array: A Systematic Review of the Method and Its Potential Accuracy

The analysis of ring images produced by muons in an Imaging Atmospheric Cherenkov Telescope (IACT) provides a powerful and precise method to calibrate the IACT optical throughput and monitor its optical point-spread function (PSF). First proposed by the Whipple collaboration in the early 90's, this method has been refined by the so-called second generation of IACT experiments: H.E.S.S., MAGIC and VERITAS. We review here the progress made with these instruments and investigate the applicability of the method as the primary throughput calibration method for the different telescope types forming the future Cherenkov Telescope Array (CTA). We find several additional systematic effects not yet taken into account by previous authors and propose several new analytical methods to include these in the analysis. Slight modifications in hardware and analysis need to be made to ensure that such a calibration works as accurately as required for the CTA. We derive analytic estimates for the expected muon data rates for optical throughput calibration, camera pixel flat-fielding and monitoring of the optical PSF. The achievable statistical and systematic uncertainties of the method are also assessed.

Dependence of the Stereokinetic Effect on the Rotational Speed and Eccentricity of the Test Image in Children with Partial Optic Atrophy

We studied the influence of the rotational speed and eccentricity of the ring image on the severity of the stereokinetic effect (SE) in a group of 36 children aged 8 to 16 years with partial optic atrophy and in the control group of 44 age-matched children with a normal fundus. Four variants of the ring image with the eccentricity of 0.2, 0.4, 0.6 or 0.8 were used as a test image. The rotational speed of the ring image was 2, 10, 30, 60 or 90 rpm. It was found that the stereokinetic effect was absent in the majority of children (63.9%) with optic atrophy at a combination of eccentricity of 0.2 and a rotational speed of 2 rpm, in contrast to the control group, where the stereokinetic effect was only absent in 9.1% of children under the same conditions of stimulus presentation. The stereokinetic effect was observed with all eccentricities when the speed of rotation of the test image was 30–90 rpm in children with optic atrophy and 10–90 rpm in children from the control group. The number of children with alternate perception of the virtual cone and the virtual funnel was significantly higher in the control group than in the group of children with optic atrophy at all the test image eccentricities and rotational speeds used. The binocular figure size estimates were equal to the monocular estimates in the group of children with optic atrophy for all the image eccentricities and rotation speeds in contrast to the control group with a general tendency for the virtual cone size estimate to increase under the monocular conditions of observation. An increase in the test image rotation speed from 2 to 60 rpm was accompanied by an increase in the size of a virtual figure and a significant decrease in the duration of alternate dominance of virtual cone and virtual funnel perception in both groups of subjects with all the eccentricities used. The difference between the results obtained in the group of children with POA and in the control group may be explained by reduction of afferent visual information flow. These differences are partially offset by increased speed and increased eccentricity of the test image.

Performance and commissioning of HAPDs in the Aerogel RICH counter

The Belle II Aerogel Ring Imaging Cherenkov (ARICH) counter uses the angular distribution of Cherenkov photons emitted in silica aerogel to discriminate between charged pions and kaons. The Hybrid Avalanche Photo Detector (HAPD) is used as the photo-sensor, and is clearly the most critical component of the detector. HAPDs were installed into ARICH in July 2017, and ARICH was installed in the Belle II spectrometer in the end of 2017. During the Belle II beam commissioning in spring 2018, the performance of HAPDs was evaluated through measurements of the offset value, noise level and pulse height. Long term stability of the signal-to-noise ratio and the fraction of dead channel was also monitored. The signal-to-noise ratio exceeded 6, and the fraction of dead channels was less than 1%. The results of the performance evaluation and of the commissioning showed that the ARICH counter fulfills the requirements.

Robust Optical Spatial Localization Using a Single Image Sensor

A novel 3-D spatial localization method using a single camera with temporal-difference image processing is proposed. The proposed active localization method uses a ring of light-emitting diodes embedded on the target. The diameter and the central location of the ring's image on the image sensor are used to estimate the target location using a Volterra series expansion of the target coordinates. No knowledge of the camera hardware parameters is needed. Instead, Volterra series parameters are obtained through a prior training that needs to be performed only once. The proposed method can be implemented with low computational complexity and storage. The performance of the proposed method is compared against an earlier method that relies on prior knowledge of the camera hardware parameters. The proposed method demonstrates excellent performance even when the target is located far away from the axial direction of the camera lens. The proposed method can be applied in low-power outdoor unmanned aerial vehicle localization and indoor robotic navigation.

Conical beam geometry intensity-modulated radiation therapy

Most commonly in radiation therapy, treatments are delivered in a co-planar geometry. Numerous advantages have been reported of adding non-coplanar beams to the treatment plan. The aim of this study was to compare current state-of-the-art VMAT and CyberKnife treatment plans to that of a novel linac design developed at Stanford which utilizes a static conical beam arrangement that allows the inclusion of a full ring diagnostic CT with shared isocenter with the treatment beams.Four clinical cases, prostate, lung, head/neck, and pediatric brain, were selected and treatment plans were generated with 45° or 60° (to the longitudinal axis of the patient) conical beam IMRT and compared with co-planar 90° VMAT plans. Double cone, with beams entering from both superior and inferior directions, and single cone geometries were evaluated. Plans were optimized in RayStation using an in-house developed script to minimize operator bias between the different techniques. Non-coplanar CyberKnife IMRT plans for the pediatric and prostate case were optimized separately in MultiPlan and compared to conical geometry plans.In the prostate case, increased mean dose to the rectum (2.3–3.7 Gy) and bladder (9.5–14.5 Gy) but decreased dose to the femoral heads (femurs) (7.1–10 Gy) were found with the conical arrangement compared to 90° VMAT. Only minor dosimetric differences were found in the lung case, while selective sparing of organs at risk was found with 45° or 60° conical arrangement in the pediatric brain and head/neck cases. For the prostate case, a reduction in mean doses to the bladder and rectum of 6% (2 Gy) and 18% (5.2 Gy), respectively, was found when comparing the CyberKnife to the 60° conical plan, in favor of the CyberKnife plan, but with an increase in integral dose and reduced conformity. An increase in integral dose and reduced conformity was also found for the pediatric brain case when comparing CyberKnife and 60° conical plan. Minor benefits were found with double cone compared to single cone geometry.Comparable treatment plan quality could be achieved between conical beam arrangement and 90° (coplanar) VMAT and CyberKnife (non-coplanar) IMRT, demonstrating the promise of this novel beam geometry. The use of this beam geometry allows volumetric image-guidance with full ring imaging and a common isocenter for simultaneous treatment and imaging.

Belle II aerogel RICH detector

The aerogel Ring Imaging CHerenkov counter (ARICH) is the particle identification device installed in the forward region of the Belle II detector at the SuperKEKB accelerator facility in Japan. The first electron–positron collisions at SuperKEKB took place on April 26, 2018, during the so called phase 2 run. The measured performance of the detector based on recorded Bhabha events during phase 2 is presented. We measure a 14 mrad average angular resolution per photon and 10 photons per Bhabha electron in the [6–8] GeV/c momentum range.

Particle identification in the Belle II experiment

The Belle II experiment integrates two dedicated particle identification (PID) subdetectors for pion/kaon separation. The Aerogel Ring Image Cherenkov (ARICH) detector is a forward region PID detector based on two layers of aerogel read out by hybrid avalanche photo detectors. The Time of Propagation (TOP) detector is a novel Cherenkov barrel PID system built for the Belle II detector upgrade based on quartz radiator bars read out by Micro-Channel Plate PMTs. The readout electronics of the TOP system are built around a switched capacitor array waveform sampling ASIC operating at 2.7 GSa/s. Acquired waveforms are processed in real time in the front-end electronics, extracting the individual timing of detected photons to better than 100 ps. This contribution presents the concept of the Belle II particle identification systems with a focus on the current status of commissioning, calibration and operation of the Belle II TOP detector.

RICH detector development for the Electron–Ion Collider experiments

Abstract In the proposed Electron–Ion Collider (EIC) experiments, particle identification (PID) of the final state hadrons in semi-inclusive deep inelastic scattering allows the measurement of flavor-dependent gluon and quark distributions inside nucleons and nuclei. The EIC PID consortium (eRD14 Collaboration) has been formed for identifying and developing PID detectors using ring imaging Cherenkov (RICH) techniques for the future EIC experiments in a broad kinematic coverage. In this article, we summarize the recent work of the eRD14 Collaboration on three RICH detector systems: DIRC, dual radiator RICH, and compact modular RICH.

Status of the NA62 ring imaging Cherenkov detector

Abstract The Ring Imaging Cherenkov detector of the NA62 experiment at the CERN SPS is a key element of particle identification in the NA62 experimental strategy. The detector fulfills different conditions: to distinguish pions from muons with a muon rejection factor of O(10 2 ) in the NA62 momentum range of operation, between 15 and 35 GeV/c; to measure particle arrival time in the decay region with a precision better than 100 ps; to provide fast signals and reference time to the NA62 trigger system. The main design aspects and functional characteristics, as well as the performance of the detector measured with the data taken in the first NA62 physics runs, will be summarized in this paper.

Operational status of the Belle II Time-Of-Propagation counter readout and data acquisition system

Abstract The front-end electronics system for the Belle II Time-Of-Propagation (TOP) counter was fully installed in May 2016. The detector is a novel particle identification device for the barrel region, where Cherenkov ring images are reconstructed with precise timing information of each photon. The readout electronics need to have excellent timing performance for single photon detection. To exploit the benefit of high luminosity, the electronics must also be able to cope with a high input trigger rate (30 kHz) and have buffer memory which is deep enough to wait for a trigger decision ( > 5 μ s ). The TOP electronics has switching capacitor arrays to sample waveforms with 2.7 GSample/s, which allows a timing resolution of 50 ps for a single photon signal. The programmable logic and the processing system are the effective implementation to meet these requirements, where flexible optimization and step-by-step development of readout logic are possible. The system has been successfully operated in the first accelerator commissioning runs with beam collisions in 2018, where the typical trigger rate was 500 Hz . Operation with a 20 kHz trigger rate was also tested.

Performance of the NA62 ring imaging Cherenkov detector

The Ring Imaging Cherenkov detector of the NA62 experiment at the CERN SPS is a key element of particle identification in the NA62 experimental strategy. According to the NA62 requirements, the RICH identifies π+ and μ+ in the momentum range between 15 and 35 GeV/c with a muon rejection factor of O(102), measures the arrival time of charged particles with a precision better than 100 ps and is one of the main components of the NA62 trigger system. After the commissioning in 2014–2015, the RICH detector has been successfully operated during the 2016, 2017 and 2018 data taking periods of NA62. The main design aspects and operational characteristics of the NA62 RICH are described and results on its performance, directly measured with data, are presented.

Cherenkov light imaging in particle and nuclear physics experiments

Abstract Ring Imaging Cherenkov Detectors (RICH) play a significant role in particle and nuclear physics experiments providing particle identification. They work exceptionally well for hadron identification as there are few other techniques that can differentiate between pions kaons and protons in the multi-GeV/c momentum range. This article is a review of detectors using Cherenkov light imaging viewed from a historical perspective and following the evolution of the techniques and technologies.

Practical considerations in modeling the low light response of photomultiplier tubes in large batch testing

Abstract Photomultiplier tubes continue to be a reliable, cost-effective means of detecting light produced by the interaction of subatomic particles with detectors. For detectors where the expected light yield is modest, characterizing the low light response of the tube is of paramount importance. Several phenomenological models addressing this issue exist. This paper presents side-by-side comparison between three such approaches as they arose from a large scale testing of tubes to be used by a Ring Imaging Cherenkov detector at Jefferson Lab. The main characteristics of the tubes, such as the gain, were found to be consistent within the expected uncertainties for all models considered. Leveraging the extensive nature of the study, a machine learning algorithm based on an artificial neural network capable of obtaining the tube characteristics directly from the raw ADC data was developed and trained. The trained neural network produced results fully compatible with the three models considered, with substantial savings in both computation time and experimenter overhead.