18F-FDGPET/CT: diabetes and hyperglycaemia

BACKGROUND: Some patients who undergo 18F-FDG PET/CT for neoplastic or benign disease are also affected by diabetes or hyperglycaemia. We propose different preparation procedures in patients (pts) with hyperglycaemia (acute, temporary or chronic) or diabetes (type 1 or 2) at the time of the 18F-FDG injection, in order to improve the diagnostic scheduling of 18F-FDG PET/CT. MATERIAL AND METHODS: We evaluated a sample of 13,063 pts, examined in two different PET/CT centres, one with a stationary scanner (94.4%) and the other with a mobile device (5.6%). High blood sugar was present in 1,698 patients (13%) at the time of the 18F-FDG injection (hyperglycaemia was defined as fasting blood glucose > 11.1 mmol/l). We considered all 18F-FDG PET/CT tests performed over a period of 4 years (2006-2009). In the first 2 years (6,236 tests), scheduling was done directly by the administrative secretary. In the next two years, 6,827 pts underwent a preliminary visit to assess the test indications, medical history, and therapy as well as pre-test preparation. We evaluated different preparation protocols for hyperglycaemic or diabetic pts, especially those recommended in the guidelines of the European Association of Nuclear Medicine (EANM) and Society of Nuclear Medicine (SNM). RESULTS: In the four-year period, 713/13,063 patients (5.45%) were rescheduled; of these, 78.8% were rescheduled in the two years before the implementation of our preparation protocols and 21.2% in the next two years. Before the implementation of our preparation protocols, 562 patients (9%) presented occasional, acute or chronic hyperglycaemia (56.7%), or diabetes (43.3%), requiring postponement of the test to a later date. The test was not performed in 17 of 6,236 pts (0.27%) because of blood glucose levels above 11.1 mmol/l for several days, while in 16/6236 pts (0.26%) the 18F-FDG injection was performed despite high blood glucose levels, in view of the clinical urgency. After the implementation of the preparation protocols, 2.2% of pts were rescheduled because of occasional, acute or chronic hyperglycaemia (79%), or diabetes (21%); 0.1% of pts did not undergo the test because of chronic high blood glucose levels. Although the administration of insulin is recommended in the EANM and SNM guidelines, in our new preparation procedures experience it was not necessary, because we reduced the numbers of hyperglycaemic pts thanks to screening at the preliminary visit and a subsequent good preparation of the patient before scheduling. CONCLUSIONS: The application of our preparation protocols improves the on-time performance and diagnostic accuracy, and increases patients' compliance. Copyright © 2013 Via Medica

Transport of swirling entropy waves through an axial turbine stator

The transport of entropy waves and their impact on the stage aerodynamics are still open questions. This paper shows the results of an experimental campaign that focuses on the swirling entropy waves advection through an axial turbine stator. The research aims at quantifying the aerodynamic impact of the swirling entropy waves on the first nozzle and characterizing their transport. The disturbance is generated by a novel entropy wave generator that ensures a wide set of different injection parameters. The device injects the disturbance axially, four different clocking positions are investigated. Measurements show a severe temperature attenuation of the swirling entropy wave at stator outlet. The high temperature location changes with the injection position as a result of the different interaction with the stator secondary flows. Depending on the injection position, the aerodynamic flow field is strongly perturbed by the injected swirl profile, instead the entropy wave effect is negligible

Impact of swirling entropy waves on a high pressure turbine

The harsh environment exiting modern gas turbine combustion chamber is characterized by vorticity and temperature perturbations, the latter commonly referred as entropy waves. The interaction of these unsteadiness with the first turbine stage causes non-negligible effects on the aerodynamic performance, blade cooling and noise production. The first of these drawbacks is addressed in this paper by means of an experimental campaign: entropy waves and swirl profile are injected upstream of an axial turbine stage through a novel combustor simulator. Two injection positions and different inlet conditions are considered. Steady and unsteady experimental measurements are carried out through the stage to address the combustor-turbine interaction characterizing the injected disturbance, the nozzle and rotor outlet aerothermal field. The experimental outcomes show a severe reduction of the temperature perturbation already at stator outlet. The generated swirl profile influences significantly the aerodynamic, as it interacts with the stator and rotor secondary flows and wakes. Furthermore, the clocking position changes the region most affected by the disturbance, showing a potential modifying the injection position to minimize the entropy wave and swirl profile impact on the stage. Finally, this work shows that in order to proficiently study entropy waves, the unsteady aerodynamic flow field stator downstream has to be addressed

The Role of Turbine Operating Conditions on Combustor-Turbine Interaction-Part II: Loading Effects

Aero-engine combustors burn a lean and premixed blend releasing vorticity and temperature perturbations. Interacting with the first turbine stage, these disturbances impact the cascade aerodynamics, add criticality to the blade cooling, and are sources of noise. The first of these issues is addressed in this paper, focusing on off-design turbine conditions, as experienced by aero-engines in their duty. This paper, Part II of a two-fold contribution, analyses the effect of the stage loading obtained by changing the rpm (three different values) at the same expansion ratio of 1.4, representative of subsonic flow conditions. Engine-representative disturbances are generated by a combustor simulator able to produce a swirling entropy wave. Two injection positions and four injection patterns are considered. Experimental measurements are carried out through the stage, measuring the injected disturbance and the aerothermal flow field downstream of the stator and the rotor. Results show that the swirl profile mostly impacts the stage aerodynamics. The different work extraction and the interaction with secondary flow structures change the entropy wave transport, diffusion, and decay through the rotor. Furthermore, the increased angle of the incidence caused by the injected disturbance can make the blade stall under the most loaded operating condition

The Role of Turbine Operating Conditions on Combustor-Turbine Interaction - Part I: Change in Expansion Ratio

Aeroengine lean-burn combustors release vorticity and temperature perturbations that, interacting with the first turbine stage, impact the stage aerodynamics, the blade cooling, and noise production. The first of these issues is addressed in this paper that is Part I of a two-fold contribution. A detailed experimental analysis is carried out to study the impact on the combustor-turbine interaction of the off-design conditions experienced by aero-engines in their duty. Engine-representative disturbances are generated by a combustor simulator able to produce swirling entropy waves. Two injection positions and four injection cases are studied. Experimental measurements are carried out at three traverses: upstream of the stator, at the interstage, and downstream of the rotor. This paper analyses the effect of the stage expansion ratio: two values are studied, namely 1.4 and 1.76, representative of subsonic and transonic flow conditions. They are chosen imposing similar velocity triangles at the rotor inlet. Results show that the swirl profile considerably impacts the stage aerodynamics. The aerothermal flow field downstream of the stator is modified significantly by the combustor disturbances. Conversely, downstream of the rotor, the differences in aerodynamics lessen. However, the entropy wave persists at the stage outlet and its transport depends on both the operating point and the injection position