Improved assessment of middle ear recurrent/residual cholesteatomas using temporal subtraction CT

Purpose The purpose of this study was to investigate the usefulness of temporal subtraction CT (TSCT) of temporal bone CT for the detection of postoperative recurrent/residual cholesteatoma of the middle ear. Methods Thirty-two consecutive patients with surgically proven postoperative recurrent/residual cholesteatoma and 14 consecutive patients without recurrent/residual lesion matched the selection criteria and were retrospectively evaluated. TSCT imaging was generated with the use of serial postoperative CT. Two experienced radiologists and two residents evaluated the presence of bone erosive change by comparison serial CT studies, and CT and TSCT. The detection rate of bone erosive change, sensitivity and specificity of the recurrence/residual lesions, and reading time for each reader were evaluated. Results TSCT + CT significantly improved the detection of bone erosive changes compared to CT-only evaluation (17.4–41.3% vs. 37.0–58.7%, p = 0.008–0.046). The mean sensitivity and specificity of TSCT + CT for experienced radiologists were 0.77 and 1.00, and 0.52 and 0.97 without TSCT. The mean sensitivity and specificity of TSCT + CT for residents were 0.64 and 1.00, and 0.41 and 1.00 without TSCT. Sensitivity showed an increase in all readers. The use of TSCT significantly reduced the reading time per case in all readers (p < 0.001). Conclusion TSCT improves the depiction of newly occurring progressive bone erosive changes, and detection sensitivity and reading time in postoperative recurrence/residual cholesteatoma of middle ear.

High-Speed Shadowgraphy Measurements of an Erosive Particle-Laden Jet Under High-Pressure Compressor Conditions

Erosive damage done to jet engine compressor blading by solid particles has a negative influence on the compressor aerodynamic properties and hence decreases performance. The erosive change of shape has been investigated in a multitude of experiments ranging from eroding flat plates to eroding full engines. The basic challenge to transfer the results from very simple tests to real life erosion remains. Up to date measurement techniques today allow closing this gap. The necessary experimental and analytical steps are shown. The erosion resistance of Ti–6Al–4V at realistic flow conditions with fluid velocities ranging from 200 to 400 m/s is used. The erodent used was quartz sand with a size distribution corresponding to standardized Arizona Test Dust A3 (1–120 μm). Flat plates out of Ti–6Al–4V were eroded at different impingement angles. The particle velocities and sizes were investigated using a high-speed laser shadowgraphy technique. A dimensional analysis was carried out to obtain nondimensional parameters suitable for describing erosion. Different averaging methods of the particle velocity were examined in order to identify a representative particle velocity. Compared to the fluid velocity and the mean particle velocity, the energy averaged particle velocity is found to be the best representation of the erosiveness of a particle stream. The correlations derived from the dimensional analysis are capable of precisely predicting erosion rates for different rig operating points (OPs). The results can be applied to the methodology published by Schrade et al. (2015, “Experimental and Numerical Investigation of Erosive Change of Shape for High-Pressure Compressors,” ASME Paper No. GT2015-42061).

Experimental and Numerical Investigation of Erosive Change of Shape for High-Pressure Compressors

Compressor performance and maintenance characteristics of jet engines are highly influenced by erosion caused by ingested, solid particles. For a meaningful prediction of these characteristics, an adequate modeling of the erosive change of shape of compressor blades is necessary. This article investigates the erosive change of shape of two different specimens (cylinder and compressor blade) out of aluminum alloy EN AW-6060 both experimentally and numerically. The erosion experiments were performed with a test rig using different amounts of standardized Arizona Test Dust A3 (particle sizes of 1–120μm) to acquire the time-dependent change of shape of the specimens. The shape of the specimens was digitized using a strip projection technique before and after each erosion test. The test rig provides boundary conditions specific for first stages of axial high-pressure compressors of jet engines in terms of relative fluid velocity (350ms−1) which is the main parameter of erosion. Numerical results were obtained with a model predicting the time-dependent change of shape of the specimens in 2D. The numerical model uses erosion rate curves that were experimentally determined in the same test rig using flat plates out of the aforementioned aluminum alloy. Thus, we were able to investigate experimentally the time-dependent erosive change of shape of the specimens and compare it with the numerical predictions. We conclude that the numerical model is a valid approach to predict erosive change of shape for different specimen geometries and materials, when erosion rate curves are available for these materials.

Longstanding Eosinophilic Gastroenteritis of More Than 20 Years

Eosinophilic gastroenteritis (EGE) is an eosinophil-predominant inflammatory process that may be detected in endoscopic gastric or intestinal biopsies. The long-term natural history and effects of EGE treatment are not known. A 44-year-old man with abdominal pain was treated with oral ketotifen and followed for more than 20 years. Ketotifen provided symptomatic benefit, with prompt clinical relapse if the drug was discontinued. However, despite the use of ketotifen, the endoscopic abnormalities persisted and appeared to progress. Gastric body and antral mucosal folds appeared thickened, erythematous and friable, with minimal erosive change. Later, even during long asymptomatic periods suggesting clinical ‘remission’, inflammatory polypoid change, previously described in children with EGE, developed with mucosal ‘pock-marking’ and apparent scarring. Ketotifen treatment does not appear to prohibit or reverse the inflammatory process in the gastric mucosa in EGE, although long-term effects of steroids may be avoided. In the future, treatment of EGE may involve monoclonal antibody agents that target the specific biological effects of the eosino-phil, apparently central to this unusual inflammatory process.