The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform

Mirko Nitsche - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Field size and length of plantar spur on treatment outcome in radiation therapy of plantar fasciitis: the bigger the better?
    International journal of radiation oncology biology physics, 2013
    Co-Authors: Robert Michael Hermann, Andreas Meyer, Alexandra Becker, Michael Schneider, Michael Reible, U. M. Carl, Hans Christiansen, Mirko Nitsche
    Abstract:

    Purpose Radiation therapy is well established in the treatment of painful plantar fasciitis or heel spur. A retrospective analysis was conducted to investigate the effect of Field Definition on treatment outcome and to determine the impact of factors potentially involved. Methods and Materials A review of treatment data of 250 patients (285 heels) with a mean follow-up time of 11 months showed that complete symptom remission occurred in 38%, partial remission in 32%, and no change in 19% (11% were lost to follow-up). Variables such as radiologic evidence of plantar spurs, their length, radiation dose, Field size, age, sex, and onset of pain before administration of radiation therapy were investigated in univariate and multivariate regression analyses. Results Treatment response depended upon age >53 years, length of heel spur ≤6.5 mm (or no radiologic evidence of a heel spur), and onset of pain Conclusion Patients with short plantar heel spurs benefit from radiation therapy equally well as patients without any radiologic evidence. Moreover, smaller Field sizes have the same positive effect as commonly used large Field Definitions covering the entire calcaneal bone. This leads to a recommendation of a considerable reduction of Field size in future clinical practice.

Richard Ellis - One of the best experts on this subject based on the ideXlab platform.

  • Isorotation and differential rotation in a magnetic mirror with imposed E×B rotation
    Physics of Plasmas, 2012
    Co-Authors: Carlos Romero-talamas, R. Elton, W. C. Young, R. Reid, Richard Ellis
    Abstract:

    Doppler spectroscopy of helium impurities in the Maryland Centrifugal Experiment reveals the simultaneous existence of isorotating and differentially rotating magnetic surfaces. Differential rotation occurs at the innermost surfaces and is conjectured to cause plasma voltage oscillations of hundreds of kilohertz by periodically changing the current path inductance. High-speed images show the periodic expulsion of plasma near the mirror ends at the same frequencies. In spite of this, the critical ionization velocity limit is exceeded, with respect to the vacuum Field Definition, for at least 0.5 ms.

Peter F Sharp - One of the best experts on this subject based on the ideXlab platform.

  • automated assessment of diabetic retinal image quality based on clarity and Field Definition
    Investigative Ophthalmology & Visual Science, 2006
    Co-Authors: Alan Fleming, Sam Philip, Keith A Goatman, J A Olson, Peter F Sharp
    Abstract:

    PURPOSE: To evaluate the performance of an automated retinal image quality assessment system for use in automated diabetic retinopathy grading. METHODS: Algorithmic methods have been developed for assessing the quality of 45 degrees single Field retinal images for use in diabetic retinopathy screening. For this purpose, image quality was defined by two aspects: image clarity and Field Definition. An image with adequate clarity was defined as one that shows sufficient detail for automated retinopathy grading. The visibility of the macular vessels was used as an indicator of image clarity, since these vessels are known to be narrow and become less visible with any image degradation. An image with adequate Field Definition was defined as one that shows the desired Field of view for retinopathy grading, including the full 45 degrees Field of view, the optic disc, and at least two optic disc diameters of visible retina around the fovea. From 489 patients attending a diabetic retinopathy screening program, 1039 retinal images were obtained. The images were graded by a clinician for image clarity and Field Definition, with a comprehensive image-quality grading scheme. RESULTS: The sensitivity and specificity were, respectively, 100% and 90.9% for inadequate clarity detection, 95.3% and 96.4% for inadequate Field Definition detection, and 99.1% and 89.4% for inadequate overall quality detection. CONCLUSIONS: The automated system performs with sufficient accuracy to form part of an automated diabetic retinopathy grading system.

Joachim Hornegger - One of the best experts on this subject based on the ideXlab platform.

  • Retinal image quality assessment based on image clarity and content.
    Journal of biomedical optics, 2016
    Co-Authors: Lamiaa Abdel-hamid, Ahmed El-rafei, Salwa Elramly, Georg Michelson, Joachim Hornegger
    Abstract:

    Retinal image quality assessment (RIQA) is an essential step in automated screening systems to avoid misdiagnosis caused by processing poor quality retinal images. A no-reference transform-based RIQA algorithm is introduced that assesses images based on five clarity and content quality issues: sharpness, illumination, homogeneity, Field Definition, and content. Transform-based RIQA algorithms have the advantage of considering retinal structures while being computationally inexpensive. Wavelet-based features are proposed to evaluate the sharpness and overall illumination of the images. A retinal saturation channel is designed and used along with wavelet-based features for homogeneity assessment. The presented sharpness and illumination features are utilized to assure adequate Field Definition, whereas color information is used to exclude nonretinal images. Several publicly available datasets of varying quality grades are utilized to evaluate the feature sets resulting in area under the receiver operating characteristic curve above 0.99 for each of the individual feature sets. The overall quality is assessed by a classifier that uses the collective features as an input vector. The classification results show superior performance of the algorithm in comparison to other methods from literature. Moreover, the algorithm addresses efficiently and comprehensively various quality issues and is suitable for automatic screening systems.

Volker Budach - One of the best experts on this subject based on the ideXlab platform.

  • Virtual Simulation of a Boost Field in Adjuvant Radiotherapy of the Breast
    Strahlentherapie und Onkologie, 2004
    Co-Authors: Andreas Kaiser, Lutz Moser, Wolf Kuschke, Margit Hinkelbein, André Buchali, Volker Budach
    Abstract:

    Background and Purpose: In CT-based adjuvant radiotherapy of the breast, virtual simulation techniques have been developed. This paper demonstrates a simple virtual simulation of a boost Field. Material and Methods: 41 Fields were planned virtually, 26 as electron beams, 15 as tangential photon beams. Results: Depending on the user’s expertise the geometric accuracy was high; possible sources of error are illustrated. Resulting Field sizes tended to be slightly larger compared to conventional simulation when applying the same rules of Field Definition. Differences in focus-skin distances with consecutive divergence effects as well as partial volume effects were discussed to be causal. Conclusion: Virtual simulation of a boost Field has the potential to elegantly link the simplicity of a conventional simulation with the accurate tumor bed identification provided by a CT data set. It was shown to be feasible and favorable with regard to the patient, the medical staff, and the simulator time. Moreover, it offers a visualization of dose distributions, which was found helpful in some cases. Hintergrund und Ziel: Für die CT-geplante adjuvante Strahlentherapie der Brust sind Techniken der virtuellen Simulation entwickelt worden. In dieser Arbeit wird eine einfache virtuelle Simulation eines Boostfeldes demonstriert. Material und Methodik: 41 Felder wurden virtuell geplant, 26 als Elektronenfelder, 15 als tangentiale Photonenfelder (Abbildung 1). Ergebnisse: Für erfahrene Anwender war die geometrische Genauigkeit hoch; mögliche Fehlerquellen werden illustriert. Tendenziell waren die resultierenden Felder etwas größer als bei konventioneller Simulation, wenn die gleichen FeldDefinitionsregeln angewandt wurden (Tabelle 1). Differierende Fokus-Haut-Abstände mit konsekutiven Divergenzeffekten und Teilvolumeneffekte waren als ursächlich zu diskutieren. Schlussfolgerung: Die virtuelle Simulation eines Boostfeldes hat das Potential, die einfache Technik einer konventionellen Simulation mit der Genauigkeit der Tumorbettidentifizierung im CT-Datensatz elegant zu verbinden. Sie erwies sich als einfach zu handhaben und zeitsparend für die Patientin, das beteiligte medizinische Personal sowie die Simulatornutzung (Tabelle 2). Darüber hinaus ermöglichte sie eine Visualisierung der Dosisverteilung, die in einigen Fällen als hilfreich empfunden wurde (Abbildung 2).