15,238 research outputs found
Quantitative assessment of intrinsic noise for visually guided behaviour in zebrafish
Supported by Royal Society of London (University Research Fellowship), Medical Research Council (New Investigator Research Grant) and CNRS.Peer reviewedPostprin
ThicknessTool: automated ImageJ retinal layer thickness and profile in digital images
To develop an automated retina layer thickness measurement tool for the ImageJ platform, to quantitate nuclear layers following the retina contour. We developed the ThicknessTool (TT), an automated thickness measurement plugin for the ImageJ platform. To calibrate TT, we created a calibration dataset of mock binary skeletonized mask images with increasing thickness masks and different rotations. Following, we created a training dataset and performed an agreement analysis of thickness measurements between TT and two masked manual observers. Finally, we tested the performance of TT measurements in a validation dataset of retinal detachment images. In the calibration dataset, there were no differences in layer thickness between measured and known thickness masks, with an overall coefficient of variation of 0.00%. Training dataset measurements of immunofluorescence retina nuclear layers disclosed no significant differences between TT and any observer's average outer nuclear layer (ONL) (p = 0.998), inner nuclear layer (INL) (p = 0.807), and ONL/INL ratio (p = 0.944) measurements. Agreement analysis showed that bias between TT vs. observers' mean was lower than between any observers' mean against each other in the ONL (0.77 ± 0.34 µm vs 3.25 ± 0.33 µm) and INL (1.59 ± 0.28 µm vs 2.82 ± 0.36 µm). Validation dataset showed that TT can detect significant and true ONL thinning (p = 0.006), more sensitive than manual measurement capabilities (p = 0.069). ThicknessTool can measure retina nuclear layers thickness in a fast, accurate, and precise manner with multi-platform capabilities. In addition, the TT can be customized to user preferences and is freely available to download
A review of agreement measure as a subset of association measure between raters
Agreement can be regarded as a special case of association and not the other way round. Virtually in all life or social science researches, subjects are being classified into categories by raters, interviewers or observers and both association and agreement measures can be obtained from the results of this researchers. The distinction between association and agreement for a given data is that, for two responses to be perfectly associated we require that we can predict the category of one response from the category of the other response, while for two response to agree, they must fall into the identical category. Which hence mean, once there is agreement between the two responses, association has already exist, however, strong association may exist between the two responses without any strong agreement. Many approaches have been proposed by various authors for measuring each of these measures. In this work, we present some up till date development on these measures statistics
Healing Response to Coronary Stenting In Acute Coronary Syndrome – Early Anatomical and Functional Healing Assessed by Optical Coherence Tomography and Flow Reserve
Drug-eluting stents are associated with delayed vascular healing. Anatomical and functional healing of coronary arteries after balloon angioplasty with stenting was investigated in patients presenting with acute coronary syndrome. Bioactive stents, sirolimus-, zotarolimus-, and everolimus-eluting stents were compared in two ran-omized trials with optical coherence tomography and coronary flow reserve measurement at 2- or 3-month follow-up after stenting. Coronary flow reserve measurements were obtained by invasive thermodilution and transthoracic echocardiography. Variability of optical coherence tomography data was assessed between observers and sampling intervals.
Uncovered stent struts and impaired coronary flow reserve values were detected in all stent groups, and a link between anatomical and functional healing was discovered. Bioactive stents showed earlier and more comprehensive neointimal coverage, which happened at the expense of luminal narrowing. Strut malapposition occurred frequently despite post-dilatation.
Measurement of coronary flow reserve by transthoracic echocardiography was feasible after stenting in the left anterior descending artery of non-diabetic patients, and agreement with the invasive method was good. The results confirm that noninvasive measurement of coronary flow reserve by echocardiography can be considered for follow-up after stenting.
The sampling interval of optical coherence tomography cross-sections had a significant effect on the observed percentage of uncovered and malapposed struts. The shorter sampling interval of 0.6 mm can be used to reduce variability and overestimation of strut level data.Sepelvaltimostenttien paranemisvaste sepelvaltimotautikohtauksen hoidossa – varhainen anatominen ja toiminnallinen paraneminen valokerroskuvauksella ja virtausreservillä tarkasteltuna
Lääkestentteihin liittyy viivästynyttä verisuonen seinämän paranemista. Sepelvaltimoiden anatomista ja toiminnallista paranemista pallolaajennuksen jälkeen selvitettiin akuutin sepelvaltimotautikohtauksen saaneilla potilailla. Bioaktiivisia sekä sirolimuusia, everolimuusia ja tsotarolimuusia vapauttavia stenttejä vertailtiin kahdessa satunnaistetussa tutkimuksessa valokerroskuvantamisella ja virtausreservimittauksella 2 tai 3 kuukauden kuluttua stenttauksesta. Virtausreservimittaukset suoritettiin sekä kajoavalla termodiluutiomenetelmällä että kajoamattomalla kaikututkimuksella rintakehän päältä. Valokerroskuvantamismittausten hajontaa vertailtiin havainnoijien ja otantatiheyksien välillä.
Peittymättömiä stentin osia ja heikentyneitä virtausreserviarvoja havaittiin kaikissa stenttiryhmissä ja anatomisen ja toiminnallisen paranemisen välillä havaittiin yhteys. Bioaktiiviset stentit osoittautuivat peittyneen endoteelilla aikaisemmin ja kattavammin, mikä puolestaan johti suonen kaventumiseen. Huono kontakti suonen seinämään oli yleistä jälkilaajennuksesta riippumatta.
Kaikututkimus mahdollisti virtausreservin mittauksen kajoamattomasti vasemman laskevan haaran stenttauksen jälkitilassa diabetesta sairastamattomilla ja mittausarvot korreloivat hyvin kajoavalla menetelmällä mitattujen arvojen kanssa. Tulokset vahvistavat, että kajoamatonta virtausreservin mittausta kaikututkimuksella voidaan hyödyntää stenttauksen jälkeisessä seurannassa.
Valokerroskuvauksen otantatiheys vaikutti merkitsevästi stenttien havaittuun peittymättömyyden ja malapposition osuuteen. Tiheämmällä 0,6 mm otantavälillä voidaan vähentää hajontaa ja peittymättömyyden yliarviointia.Siirretty Doriast
Modelos de observador aplicados a la detectabilidad de bajo contraste en tomografía computarizada
Tesis inédita de la Universidad Complutense de Madrid, Facultad de Medicina, leída el 15/01/2016. Tesis formato europeo (compendio de artículos)Introduction. Medical imaging has become one of the comerstones in modem healthcare. Computed tomography (CT) is a widely used imaging modality in radiology worldwide. This technique allows to obtain three-dimensional volume reconstructions ofdifferent parts of the patient with isotropic spatial resolution. Also, to acquire sharp images of moving organs, such as the heart orthe lungs, without artifacts. The spectrum ofindications which can be tackled with this technique is wide, and it comprises brain perfusion, cardiology, oncology, vascular radiology, interventionism and traumatology, amongst others. CT is a very popular imaging technique, widely implanted in healthcare services worldwide. The amount of CT scans performed per year has been continuously growing in the past decades, which has led to a great benefit for the patients. At the same time, CT exams represent the highest contribution to the collective radiation dose. Patient dose in CT is one order ofmagnitude higher than in conventional X-ray studies. Regarding patient dose in X-ray imaging the ALARA criteria is universally accepted. It states that patient images should be obtained using adose as low as reasonably achievable and compatible with the diagnostic task. Sorne cases ofpatients' radiation overexposure, most ofthem in brain perfusion procedures have come to the public eye and hada great impact in the USA media. These cases, together with the increasing number ofCT scans performed per year, have raised a red flag about the patient imparted doses in CT. Several guidelines and recommendation for dose optimization in CT have been published by different organizations, which have been included in European and National regulations and adopted by CT manufacturers. In CT, the X-ray tube is rotating around the patient, emitting photons in beams from different angles or projections. These photons interact with the tissues in the patient, depending on their energy and the tissue composition and density. A fraction of these photons deposit all or part of their energy inside the patient, resulting in organs absorbed dose. The images are generated using the data from the projections ofthe X-ray beam that reach the detectors after passing through the patient. Each proj ection represents the total integrated attenuation of the X-ray beam along its path. A CT protocol is defined as a collection of settings which can be selected in the CT console and affect the image quality outcome and the patient dose. They can be acquisition parameters such as beam collimation, tube current, rotation time, kV, pitch, or reconstruction parameters such as the slice thickness and spacing, reconstruction filter and method (filtered back projection (FBP) or iterative algorithms). All main CT manufacturers offer default protocols for different indications, depending on the anatomical region. The user can frequently set the protocol parameters selecting amongst a range of values to adapt them to the clinical indication and patient characteristics, such as size or age. The selected settings in the protocol affect greatly image quality and dose. Many combinations ofsean parameters can render an appropriate image quality for a particular study. Protocol optimization is a complex task in CT because most sean protocol parameters are intertwined and affect image quality and patient dose...Introducción. La imagen médica se ha convertido en uno de los pilares en la atención sanitaria actual. La tomografía computarizada (TC) es una modalidad de imagen ampliamente extendida en radiología en todo el mundo. Esta técnica permite adquirir imágenes de órganos en movimiento, como el corazón o los pulmones, sin artefactos. También permite obtener reconstrucciones de volúmenes tridimensionales de distintas partes del cuerpo de los pacientes. El abanico de indicaciones que pueden abordarse con esta técnica es amplio, e incluye la perfusión cerebral, cardiología, oncología, radiología vascular, intervencionismo y traumatología, entre otras. La TC es una técnica de imagen muy popular, ampliamente implantada en los servicios de salud de hospitales de todo el mundo. El número de estudios de TC hechos anualmente ha crecido de manera continua en las últimas décadas, lo que ha supuesto un gran beneficio para los pacientes. A la vez, los exámenes de TC representan la contribución más alta a la dosis de radiación colectiva en la actualidad. La dosis que reciben los pacientes en un estudio de TC es un orden de magnitud más alta que en exámenes de radiología convencional. En relación con la dosis a pacientes en radiodiagnóstico, el criterio ALARA es aceptado universalmente. Expone que las imágenes de los pacientes deberían obtenerse utilizando una dosis tan baja como sea razonablemente posible y compatible con el objetivo diagnóstico de la prueba. Algunos casos de sobreexposición de pacientes a la radiación, la mayoría en exámenes de perfusión cerebral, se han hecho públicos, lo que ha tenido un gran impacto en los medios de comunicación de EEUU. Estos accidentes, junto con el creciente número de exámenes TC anuales, han hecho aumentar la preocupación sobre las dosis de radiación impartidas a los pacientes en TC. V arias guías y recomendaciones para la optimización de la dosis en TC han sido publicadas por distintas organizaciones, y han sido incluidas en normas europeas y nacionales y adoptadas parcialmente por los fabricantes de equipos de TC. En TC, el tubo de rayos-X rota en tomo al paciente, emitiendo fotones en haces desde distintos ángulos o proyecciones. Estos fotones interactúan con los tejidos en el paciente, en función de su energía y de la composición y densidad del tejido. Una fracción de estos fotones depositan parte o toda su energía dentro del paciente, dando lugar a la dosis absorbida en los órganos. Las imágenes se generan usando los datos de las proyecciones del haz de rayos-X que alcanzan los detectores tras atravesar al paciente. Cada proyección representa la atenuación total del haz de rayos-X integrada a lo largo de su trayectoria. Un protocolo de TC se define como una colección de opciones que pueden seleccionarse en la consola del equipo y que afectan a la calidad de las imágenes y a la dosis que recibe el paciente. Pueden ser parámetros de adquisición, tales como la colimación del haz, la intensidad de corriente, el tiempo de rotación, el kV, el factor de paso parámetros de reconstrucción como el espesor y espaciado de corte, el filtro y el método de reconstrucción (retroproyección filtrada (FBP) o algoritmos iterativos). Los principales fabricantes de equipos de TC ofrecen protocolos recomendados para distintas indicaciones, dependiendo de la región anatómica. El usuario con frecuencia fija los parámetros del protocolo eligiendo entre un rango de valores disponibles, para adaptarlo a la indicación clínica y a las características del paciente, tales como su tamaño o edad. Las condiciones seleccionadas en el protocolo tienen un gran impacto en la calidad de imagen y la dosis. Múltiples combinaciones de los parámetros pueden dar lugar a un nivel de calidad de imagen apropiado para un estudio en concreto. La optimización de los protocolos es una tarea compleja en TC, ya que la mayoría de los parámetros del protocolo están relacionados entre sí y afectan a la calidad de imagen y a la dosis que recibe el paciente...Depto. de Radiología, Rehabilitación y FisioterapiaFac. de MedicinaTRUEunpu
Prediction of sarcomere mutations in subclinical hypertrophic cardiomyopathy.
BACKGROUND: Sarcomere protein mutations in hypertrophic cardiomyopathy induce subtle cardiac structural changes before the development of left ventricular hypertrophy (LVH). We have proposed that myocardial crypts are part of this phenotype and independently associated with the presence of sarcomere gene mutations. We tested this hypothesis in genetic hypertrophic cardiomyopathy pre-LVH (genotype positive, LVH negative [G+LVH-]). METHODS AND RESULTS: A multicenter case-control study investigated crypts and 22 other cardiovascular magnetic resonance parameters in subclinical hypertrophic cardiomyopathy to determine their strength of association with sarcomere gene mutation carriage. The G+LVH- sample (n=73) was 29 ± 13 years old and 51% were men. Crypts were related to the presence of sarcomere mutations (for ≥1 crypt, β=2.5; 95% confidence interval [CI], 0.5-4.4; P=0.014 and for ≥2 crypts, β=3.0; 95% CI, 0.8-7.9; P=0.004). In combination with 3 other parameters: anterior mitral valve leaflet elongation (β=2.1; 95% CI, 1.7-3.1; P<0.001), abnormal LV apical trabeculae (β=1.6; 95% CI, 0.8-2.5; P<0.001), and smaller LV end-systolic volumes (β=1.4; 95% CI, 0.5-2.3; P=0.001), multiple crypts indicated the presence of sarcomere gene mutations with 80% accuracy and an area under the curve of 0.85 (95% CI, 0.8-0.9). In this G+LVH- population, cardiac myosin-binding protein C mutation carriers had twice the prevalence of crypts when compared with the other combined mutations (47 versus 23%; odds ratio, 2.9; 95% CI, 1.1-7.9; P=0.045). CONCLUSIONS: The subclinical hypertrophic cardiomyopathy phenotype measured by cardiovascular magnetic resonance in a multicenter environment and consisting of crypts (particularly multiple), anterior mitral valve leaflet elongation, abnormal trabeculae, and smaller LV systolic cavity is indicative of the presence of sarcomere gene mutations and highlights the need for further study
Single breath-hold 3D measurement of left atrial volume using compressed sensing cardiovascular magnetic resonance and a non-model-based reconstruction approach
Background:Left atrial (LA) dilatation is associated with a large variety of cardiac diseases. Current cardiovascular magnetic resonance (CMR) strategies to measure LA volumes are based on multi-breath-hold multi-slice acquisitions, which are time-consuming and susceptible to misregistration.Aim:To develop a time-efficient single breath-hold 3D CMR acquisition and reconstruction method to precisely measure LA volumes and function.Methods:A highly accelerated compressed-sensing multi-slice cine sequence (CS-cineCMR) was combined with a non-model-based 3D reconstruction method to measure LA volumes with high temporal and spatial resolution during a single breath-hold. This approach was validated in LA phantoms of different shapes and applied in 3 patients. In addition, the influence of slice orientations on accuracy was evaluated in the LA phantoms for the new approach in comparison with a conventional model-based biplane area-length reconstruction. As a reference in patients, a self-navigated high-resolution whole-heart 3D dataset (3D-HR-CMR) was acquired during mid-diastole to yield accurate LA volumes.Results:Phantom studies. LA volumes were accurately measured by CS-cineCMR with a mean difference of −4.73 ± 1.75 ml (−8.67 ± 3.54 %, r² = 0.94). For the new method the calculated volumes were not significantly different when different orientations of the CS-cineCMR slices were applied to cover the LA phantoms. Long-axis “aligned” vs “not aligned” with the phantom long-axis yielded similar differences vs the reference volume (−4.87 ± 1.73 ml vs −4.45 ± 1.97 ml, p = 0.67) and short-axis “perpendicular” vs “not-perpendicular” with the LA long-axis (−4.72 ± 1.66 ml vs −4.75 ± 2.13 ml; p = 0.98). The conventional bi-plane area-length method was susceptible for slice orientations (p = 0.0085 for the interaction of “slice orientation” and “reconstruction technique”, 2-way ANOVA for repeated measures). To use the 3D-HR-CMR as the reference for LA volumes in patients, it was validated in the LA phantoms (mean difference: −1.37 ± 1.35 ml, −2.38 ± 2.44 %, r² = 0.97). Patient study: The CS-cineCMR LA volumes of the mid-diastolic frame matched closely with the reference LA volume (measured by 3D-HR-CMR) with a difference of −2.66 ± 6.5 ml (3.0 % underestimation; true LA volumes: 63 ml, 62 ml, and 395 ml). Finally, a high intra- and inter-observer agreement for maximal and minimal LA volume measurement is also shown.Conclusions:The proposed method combines a highly accelerated single-breathhold compressed-sensing multi-slice CMR technique with a non-model-based 3D reconstruction to accurately and reproducibly measure LA volumes and function
Phase-resolved Hubble Space Telescope ultraviolet spectroscopy
We present highly time-resolved HST FOS UV spectroscopy of the nova-like binary V795 Her. Several key results emerge. For the first time we find a strong 2.6-h signature in the variability of the UV lines. The HST data reveal no evidence of a 4.8-h ‘period’, in contrast to our previous IUE observations. This, and differences in the spectral line characteristics, suggests that HST found the system in a different state from earlier IUE observations. The C IV line alone contains a fairly stable, asymmetric, extended blueward absorption trough which we associate with a wind outflow. The 2.6-h variations of the line profiles are largely confined to an interval of about 0.4 in phase and to the velocity regime −1500 < v < 0 km s−1, the changes being dominated by the apparent decline and re-emergence of a blueshifted emission peak. The complex profiles permit many empirical interpretations, but the simplest attributes the variability to a narrow (FWHM∼1000 km s−1) emission component which is always blueshifted with a mean velocity of around –600 km s−1. This interpretation, however, is not readily related to any obvious source within the binary. An alternative picture, which attempts to relate the UV and (simultaneously observed) optical line behaviour, invokes a more stable, broad (FWHM∼2000 km s−1) emission feature, the intrinsic morphology of which is disguised by superposed constant and variable absorption components. One tentative physical explanation of such a decomposition involves an accretion stream that overflows the accretion disc. However, several problems with this model remain to be resolved. We also draw attention to similarities between the velocity-restricted behaviour in the UV lines of V795 Her and that in the optical lines of T Tauri stars. This might indicate a connection between V795 Her and the magnetically influenced inflow/outflow characteristics associated with the central star in T Tauri systems. If such a connection were eventually demonstrated, it would reopen the question of whether the 2.6-h period in V795 Her is really the binary period and whether the system is in fact related to the intermediate polars
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