| 1. |
- Abou Nada, Fahd Jouda, et al.
(author)
-
A first application of thermographic phosphors in a marine two-stroke diesel engine for surface temperature measurement
- 2014
-
In: Proceedings of the ASME 2014 Internal Combustion Engine Division Fall Technical Conference (ICEF2014). ; , s. 001-001
-
Conference paper (peer-reviewed)abstract
- Phosphor thermometry is applied for the first time in a large-bore two-stroke diesel engine. The work proves the practicality of phosphor thermometry in large-bore engines. The experiments were conducted on the MAN 4T50ME-X marine research engine equipped with an optical cylinder head. By employing a thin surface coating of CdWO4 phosphor, cycle resolved temperature measurements of the cylinder wall were obtained. Motored and fired engine operations were tested at engine loads covering the low and medium engine load range. Phosphor thermometry proved to be successful in retrieving the temperature with standard deviations ranging around 1-8 K. Experimental considerations like detector linearity, coating thickness and an automated phosphor calibration routine will be addressed.
|
|
| 2. |
- Abou Nada, Fahd Jouda, et al.
(author)
-
Development of an automatic routine for calibration of thermographic phosphors
- 2014
-
In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
-
Journal article (peer-reviewed)abstract
- An automated routine for the continuous calibration of thermographic phosphors was developed as a replacement for the conventional calibration scheme that relied on fixed temperature points. The automated calibration routine was validated using Mg 3 F 2 GeO 4 :Mn as a calibration phosphor. Hardware and software aspects of the calibration process were addressed in this development. The hardware aspect included a new substrate design using a high performance alloy, the Hastelloy-C alloy, whereas the software aspect included an automated acquisition system which was capable of acquiring simultaneous thermocouple temperatures and phosphor decay waveform in real time. The design of the calibration process eliminates the need for a system in thermal equilibrium during a phosphor calibration measurement. Temperature ramping rates of up to 4 K min −1 were employed in the oven without a delay in the temperature response being measured between the phosphor and the thermocouples involved. In addition, the automated calibration setup allowed for detailed investigations on the effect of heat being delivered to the phosphor coating by the laser. These findings were confirmed by a simple heat transfer model, based on lumped system analysis. In comparison to the data acquisition performed at several fixed points with the conventional calibration scheme, the experiment duration was shortened by a factor of 4 with the overall accuracy improved by 1–2 K.
|
|
| 3. |
- Abou Nada, Fahd Jouda, et al.
(author)
-
Improved measurement precision in decay time‑based phosphor thermometry
- 2016
-
In: Applied Physics B. - : Springer Science and Business Media LLC. - 1432-0649 .- 0946-2171. ; 122
-
Journal article (peer-reviewed)abstract
- This study comprises a continuation of the previous efforts of the authors to characterize different sources of errors in phosphor thermometry based on the determination of luminescence decays from thermographic phosphors. Whereas earlier investigations focused on point detectors utilizing different sensor technology, this work presents a comparison of four PMTs that are identical in terms of their product type. These detectors are supposedly identical, but the investigations revealed that their response is strictly individual. This study also shows a linear excitation energy dependence for the decay time of cadmium tungstate (CdWO4), the phosphor being used in this work. In addition, the potential influence of the intense and short fluorescence peak preceding the weaker and longer exponential decay in some phosphor materials, was investigated using the electrical signal gating capability of the PMT. Finally, the evaluated decay time also appeared to be affected by the oscilloscope settings used when recording the phosphorescence signals. The presented results indicate that all operating parameters from the calibration measurement need to be rigorously reproduced in order to avoid systematic temperature errors in phosphor thermometry experiments that are based on reproducible measurements of the decay time. These results should be of more general interest also outside the phosphor community as the findings, presented herein, in principal concern all kinds of measurements that are dependent on reproducible measurements of signal shapes or time-transients.
|
|
| 4. |
- Abou Nada, Fahd Jouda, et al.
(author)
-
On the automation of thermographic phosphor calibration
- 2014
-
In: Proceedings of the 60th International Instrumentation Symposium.
-
Conference paper (peer-reviewed)abstract
- Thermographic phosphors can be robust temperature remote sensors. The accuracy of the temperature measured by the phosphor is highly dependent on the quality of the phosphor calibration used. Conventionally, thermographic phosphors are calibrated by measuring a series of decay curves at known stable oven temperatures. The process is then repeated covering the thermal sensitivity range of the phosphor chosen. Heating and cooling rates of high temperature ovens are usually low. Also, thermal equilibrium of the system is required at each calibration temperature before acquiring luminescence decay curves. Thus, the process is usually time consuming and the number of calibration points achieved is limited to a couple of dozen points. This study presents and validates the development of an automatic routine for the calibration of thermographic phosphors. It was designed to continuously and simultaneously acquire phosphor decay curves along with their corresponding thermocouple temperatures. The developed routine required software and hardware improvements. An updated design of the calibration substrate was implemented to improve the thermal conditions during calibration. Thermal gradients were further studied using a heat transfer model. The routine implemented a specially designed sparsing algorithm that reduced the sampling rate of the decaying luminescence curve without influencing the calculated decay time. The upper heating rate is set at 4 K.min-1 due to limitation imposed by the ceramic calibration oven. The phosphors CdWO4 and Mg3F2GeO4:Mn were chosen to validate the finalized routine. After the completion of the calibration process, a library-based calibration is created as the final product. The automated calibration routine delivered an overall accuracy improvement of 1-2 K, reduced calibration duration by factor of four and provided the possibility of deriving signal recognition algorithms. The condensed calibration dataset produced by the proposed calibration routine was further employed to develop a novel signal shape recognition algorithm for temperature evaluation.
|
|
| 5. |
- Algotsson, Martin, et al.
(author)
-
In-cylinder Surface Thermometry using Laser Induced Phosphorescence
- 2012
-
In: [Host publication title missing]. ; , s. 482-487
-
Conference paper (peer-reviewed)abstract
- Surface temperature in internal combustion engines is of high interest when studying heat losses. Two approaches for retrieving the surface temperatures are thermocouples and Laser Induced Phosphorescence, LIP. This study aims to analyze LIP as a technique for measuring surface temperature in internal combustion engines. The motivation for this study is the need for accurate surface temperatures which can be used by predictive models and increase knowledge about heat transfer. In this work LIP measurements have been carried out in two optical engines. In the first engine a thermographic phosphor was applied on top of a metal piston. The second engine was fitted with a quartz liner which was coated with phosphor material. Several coating thicknesses have been tested and the LIP temperature was extracted from both opposing sides of the phosphor. Both engines were run in HCCI mode with reference fuels and electrically heated air. In a previous publication, the authors showed that a layer of phosphor can show different temperatures i.e. a higher temperature on the side facing the cylinder gas than on the side facing the wall. In this study it is shown which thickness is needed to accurately present the temperature for typical engine combustion. With an increasing thickness of the phosphor material, the surface gets gradually insulated and the phosphor temperature reading becomes inaccurate. LIP measurements from a quartz ring and a metal piston have been compared and the temperature increase during combustion is similar although the heat conductivity of quartz is 40-200 times smaller than the metal piston. Measurements with thermocouples often show a lower temperature increase than what is seen in the LIP results. The difference in heat conductivity between the phosphor coating and the underlying surface is of importance for understanding what temperature is actually measured.
|
|
| 6. |
- Knappe, Christoph, et al.
(author)
-
A library-based algorithm for evaluation of luminescent decay curves by shape recognition in time domain phosphor thermometry
- 2014
-
In: Journal of Thermal Analysis and Calorimetry. - : Springer Science and Business Media LLC. - 1588-2926 .- 1388-6150. ; 115:1, s. 545-554
-
Journal article (peer-reviewed)abstract
- This work describes and characterizes an algorithm for the nonambiguous reduction of multiexponentially decaying luminescence signals to scalar values of corresponding calibration temperatures. Previous evaluation schemes in phosphor thermometry make use of an intermediate step, where data reduction is achieved by fitting a model equation to phosphorescence decays in order to translate one or more fitting parameters into temperature. However, every slight mismatch between model equation and experimental data may lead to substantial errors in connection to noise-related inaccuracies during the retrieval of adequate fitting windows. Additionally, there is a need for fitting windows, capable of automatically adapting to largely varying signal time scales. In this context, the authors propose to set the fitting window length according to the time where the signal falls below a given percentage of the initial intensity. In comparison to fitting windows, defined by multiple decay times, modeling results suggest substantial precision benefits for as long as signal-to-noise ratios stay above 4. Nevertheless, by comparing signal shapes of measured curves directly with a library of temperature-calibrated decay signals, all necessary assumptions on the mathematical description of measured signals become redundant and evaluation errors connected to uncertain fitting windows are largely circumvented. Resulting capabilities of the proposed signal shape recognition method (SSR) in terms of temperature precision and accuracy were compared to a conventional least-squares fitting approach, using a set of temperaturecalibrated phosphorescence decay signals from CdWO4. Accordingly, the SSR algorithm was found to reduce statistical temperature errors by at least 9 %.
|
|
| 7. |
- Knappe, Christoph, et al.
(author)
-
Comparison of photo detectors and operating conditions for decay time determination in phosphor thermometry
- 2012
-
In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:9
-
Journal article (peer-reviewed)abstract
- This work compares the extent of linear response regions from standard time-resolving optical detectors for phosphor thermometry. Different types of photomultipliers (ordinary and time-gated) as well as an avalanche photodiode were tested and compared using the phosphorescence decay time of cadmium tungstate (CdWO4). Effects originating from incipient detector saturation are revealed as a change in evaluated phosphorescence decay time, which was found to be a more sensitive measure for saturation than the conventional signal strength comparison between in- and output. Since the decay time of thermographic phosphors is used for temperature determination systematic temperature errors in the order of several tens of Kelvins may be introduced. Saturation from the initial intensity is isolated from temporally developed saturation by varying the CdWO4 decay time over the microsecond to nanosecond range, resultant of varying the temperature from 290 to 580 K. A detector mapping procedure is developed in order to identify linear response regions where the decay-to-temperature evaluations are unbiased. In addition, this mapping procedure generates a library of the degree of distortion for operating points outside of linear response regions. Signals collected in the partly saturated regime can thus be corrected to their unbiased value using this library, extending the usable detector operating range significantly. © 2012 American Institute of Physics.
|
|
| 8. |
- Knappe, Christoph, et al.
(author)
-
Enhanced color ratio calibration approach for two-dimensional surface thermometry using laser-induced phosphorescence
- 2013
-
In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 24:8
-
Journal article (peer-reviewed)abstract
- An alternative concept for calibrating spectral image intensity ratios is described, which provides simple, but effective means of compensation for systematic errors, caused by nonlinearities in signal detection. The method relies on image segmentation by means of signal thresholds, where pixels are organized into different subgroups according to their corresponding signal count value. Instead of defining one global spectral ratio per calibration temperature, the phosphor-coated target surface is illuminated inhomogeneously and resulting image ratios are calibrated individually for each pixel intensity subgroup. This allows the exploitation of high intensity regions on the camera chip which offer great precision advantages, but suffer from systematic errors caused by signal nonlinearities. Temperature calibration data of BaMg2Al16O27:Eu in the temperature range between 270 and 470 K was used to assess and compare the potential of both calibration approaches. In comparison to the conventional, e.g. global calibration approach, accuracy improvements of up to 39% were gained even while keeping average signal intensities below 15% of the detector’s full dynamic range. Image ratio evaluations, based on segregated pixel subgroups, could help improve measurement accuracy also for other techniques, relying on the calibration of measured quantities. In two-dimensional phosphor thermometry, it helps bridge the current precision gap between two-color ratio methods and more elaborate lifetime-imaging approaches.
|
|
| 9. |
- Knappe, Christoph, et al.
(author)
-
Investigation and compensation of the nonlinear response in photomultiplier tubes for quantitative single-shot measurements.
- 2012
-
In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 83:3
-
Journal article (peer-reviewed)abstract
- A concept for time-sensitive optical detectors is described that shows how to confirm whether the detection device is operating in the linear response regime. By evaluating the recorded time decay of a thermographic phosphor, even weak saturation effects far from obvious situations can be identified and further related to either optical or electrical saturation. The concept has been validated by running a PMT detector close to saturation and exposing it to the optical signal decay of two different thermographic phosphors, La(2)O(2)S:Eu and CdWO(4). It was confirmed that short but intense light exposures at the beginning of an individual time decay influence the detector response for the rest of the decaying signal including temporal areas, where the anode current has dropped well below the manufacturer specified current limit. Such situations are common when applying, e.g., phosphor thermometry where it is necessary to retrieve the full decay curve from a single-shot event, i.e., standard techniques based on single-photon counting are omitted. Finally, means of compensation are introduced in order to facilitate the retrieval of useful information from the measurement data when operation in the non-linear response regime is inevitable.
|
|
| 10. |
|
|
| 11. |
- Knappe, Christoph
(author)
-
Phosphor Thermometry on Surfaces - A Study of its Methodology and its Practical Applications
- 2013
-
Doctoral thesis (other academic/artistic)abstract
- Phosphor Thermometry is a term describing an optical measurement technique for remote temperature sensing. Its working principle is based on the temperature-sensitive emission characteristics of certain ceramic substances termed thermographic phosphors. These inorganic materials can either be coated on objects for surface thermometry or be seeded into the gas phase or into liquid flows as solid particles. After optical excitation, often achieved using pulsed laser systems, the phosphor emits an extended and typically red-shifted afterglow referred to as phosphorescence. As the temperature changes, either the temporal or the spectral composition of the phosphorescence emission can be used to determine temperatures through comparison with the results of temperature calibration, carried out earlier. In many applications, temperatures both at various points and in two-dimensional fields have been characterised with a high degree of temporal and spatial resolution by use of thermographic phosphors. The combined sensitivities of different phosphors span a temperature range extending from cryogenic temperatures up to approximately 2000 K. In the present study, the reader is introduced to the physical basis of phosphor luminescence and to utilization of the optical properties involved for temperature measurement. The thesis also examines various means of reducing measurement uncertainty in surface phosphor thermometry. This is done in a series of experimental studies concerned with the characterization and treatment of various error sources during temperature calibration, signal detection and data evaluation. A major factor considered here is that of the coating thickness. It appears to have an intrusive effect on surface temperatures in applications involving both high local and temporal thermal gradients. The effects of instrumentation on signal detection are also investigated. The measurement accuracy was found to depend very much upon the consistency, achieved in the reproduction of the operating conditions from the temperature calibrations carried out to the experiments. This can be attributed to non-linear signal transformations that occur during detection. Even two detectors nominally identical were shown to exhibit large differences in the linearity of the signal response. Unfortunately, the linear workspace of many detectors is confined to very low signal values, the measurement precision being comparably poor due to the low signal-to-noise ratios involved. In order to improve the measurement precision without reducing the accuracy of the results, higher signal levels could be accessed through measures to compensate for detector-specific non-linearities. The signal responses to variations in operating conditions of several different point detectors and imaging devices were characterized, providing a basis for effective means of signal correction. Interest in uncertainty reduction here also led to the investigation of means of signal processing enhancement. Temperature sensitivity was found to be a quantity which is not determined exclusively by the phosphor itself, it is also depending on the operator's choice of conditions for detection and evaluation. For evaluation schemes based on temporal decay transients, the proper choice of a time window for evaluation was found to play an important role. Finally, the versatility of phosphor thermometry as applied to surfaces was demonstrated in several industry-relevant applications, including a car engine, an aircraft turbine and a large-bore two-stroke diesel engine for marine vessels.
|
|
| 12. |
- Knappe, Christoph, et al.
(author)
-
Response Regime Studies on Standard Detectors for Decay Time Determination in Phosphor Thermometry
- 2013
-
In: Temperature: Its Measurement and Control in Science and Industry, Vol 8. - : AIP. - 1551-7616 .- 0094-243X. ; 1552, s. 879-884
-
Conference paper (peer-reviewed)abstract
- This work compares the extent of linear response regimes from standard time-resolving optical detectors for phosphor thermometry. Different types of Photomultipliers (ordinary and time-gated) as well as an Avalanche Photodiode are tested and compared using the phosphorescent time decay of CdWO4 that ranges from 10 mu s down to a few ns within a temperature span of 290 to 580 K. Effects originating from incipient detector saturation, far from obvious to the operator's eye, are revealed as a change in evaluated phosphorescence decay time. Since the decay time of thermographic phosphors itself is used for temperature determination - systematic temperature errors up to several tens of Kelvins may be introduced by such detector saturation. A detector mapping procedure is suggested in order to identify linear response regions where the decay-to-temperature evaluation can be performed unbiased. Generation of such a library is highly recommended prior to any quantitative measurement attempt. Using this detector library, even signals collected in the partly saturated regime can be corrected to their unbiased value extending the usable detector operating range significantly. Further, the use of an external current-to-voltage amplifier proved useful for most applications in time-based phosphor thermometry helping to limit saturation effects whilst maintaining a reasonable bandwidth and signal outputs.
|
|
| 13. |
- Knappe, Christoph, et al.
(author)
-
Thickness dependent variations in surface phosphor thermometry during transient combustion in an HCCI engine
- 2013
-
In: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 160:8, s. 1466-1475
-
Journal article (peer-reviewed)abstract
- Phosphor thermometry is a semi-invasive measurement technique which is commonly used for temperature determination in combustion applications. Surface temperature measurements using thermographic phosphors rely on the assumption that the phosphor layer is thin enough in order to adopt the surface temperature non-intrusively. This work compares the temperature information, recorded from two opposing sides of phosphor films, coated on a translucent part of the combustion chamber wall inside a car engine. The film thickness was varied between 5 and 72 mu m and two different phosphors were studied; CdWO4 and La2O2S:Eu. For both phosphors, the results showed no significant differences. Being subject to unsteady heat transfer during fired engine operation, phosphor coatings above 20 mu m in thickness experienced a significant temperature gradient between the front- and the backside of the coating, whereas thinner layers did not seem to be affected within the limits of measurement accuracy and precision. Cycle-to-cycle variations of the global gas temperature were not found to correlate with phosphor temperature variations. However, a strong temperature correlation between opposite sides of the phosphor coating was observed for film thicknesses below 20 mu m during engine cycle-to-cycle variations. (C) 2013 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 14. |
- Knappe, Maren, et al.
(author)
-
Surface-exposed amino acid residues of HPV16 L1 protein mediating interaction with cell surface heparan sulfate
- 2007
-
In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 282:38, s. 27913-27922
-
Journal article (peer-reviewed)abstract
- Efficient infection of cells by human papillomaviruses (HPVs) and pseudovirions requires primary interaction with cell surface proteoglycans with apparent preference for species carrying heparan sulfate (HS) side chains. To identify residues contributing to virus/cell interaction, we performed point mutational analysis of the HPV16 major capsid protein, L1, targeting surface-exposed amino acid residues. Replacement of lysine residues 278, 356, or 361 for alanine reduced cell binding and infectivity of pseudovirions. Various combinations of these amino acid exchanges further decreased cell attachment and infectivity with residual infectivity of less than 5% for the triple mutant, suggesting that these lysine residues cooperate in HS binding. Single, double, or triple exchanges for arginine did not impair infectivity, demonstrating that interaction is dependent on charge distribution rather than sequence-specific. The lysine residues are located within a pocket on the capsomere surface, which was previously proposed as the putative receptor binding site. Fab fragments of binding-neutralizing antibody H16.56E that recognize an epitope directly adjacent to lysine residues strongly reduced HS-mediated cell binding, further corroborating our findings. In contrast, mutation of basic surface residues located in the cleft between capsomeres outside this pocket did not significantly reduce interaction with HS or resulted in assembly-deficient proteins. Computer-simulated heparin docking suggested that all three lysine residues can form hydrogen bonds with 2-O-, 6-O-, and N-sulfate groups of a single HS molecule with a minimal saccharide domain length of eight monomer units. This prediction was experimentally confirmed in binding experiments using capsid protein, heparin molecules of defined length, and sulfate group modifications.
|
|
| 15. |
- Lang, Margareta, et al.
(author)
-
A pilot study of methods for prediction of poor outcome by head computed tomography after cardiac arrest
- 2022
-
In: Resuscitation. - : Elsevier BV. - 0300-9572. ; 179, s. 61-70
-
Journal article (peer-reviewed)abstract
- Introduction: In Sweden, head computed tomography (CT) is commonly used for prediction of neurological outcome after cardiac arrest, as recommended by guidelines. We compare the prognostic ability and interrater variability of routine and novel CT methods for prediction of poor outcome. Methods: Retrospective study including patients from Swedish sites within the Target Temperature Management after out-of-hospital cardiac arrest trial examined with CT. Original images were assessed by two independent radiologists blinded from clinical data with eye-balling without pre-specified criteria, and with a semi-quantitative assessment. Grey-white-matter ratios (GWR) were quantified using models with 4–20 manually placed regions of interest. Prognostic abilities and interrater variability were calculated for prediction of poor outcome (modified Rankin Scale 4–6 at 6 months) for early (<24 h) and late (≥24 h) examinations. Results: 68/106 (64 %) of included patients were examined < 24 h post-arrest. Eye-balling predicted poor outcome with 89–100 % specificity and 15–78 % sensitivity. GWR < 24 h predicted neurological outcome with unsatisfactory to satisfactory Area Under the Receiver Operating Characteristics Curve (AUROC: 0.54–0.64). GWR ≥ 24 h yielded very good to excellent AUROC (0.80–0.93). Sensitivities increased > 2–3-fold in examinations performed after 24 h compared to early examinations. Combining eye-balling with GWR < 1.15 predicted poor outcome without false positives with sensitivities remaining acceptable. Conclusion: In our cohort, qualitative and quantitative CT methods predicted poor outcome with high specificity and low to moderate sensitivity. Sensitivity increased relevantly after the first 24 h after CA. Interrater variability poses a problem and indicates the need to standardise brain CT evaluation to increase the methods’ safety.
|
|
| 16. |
- Lang, Margareta, et al.
(author)
-
Prognostic accuracy of head computed tomography for prediction of functional outcome after out-of-hospital cardiac arrest : Rationale and design of the prospective TTM2-CT-substudy
- 2022
-
In: Resuscitation Plus. - : Elsevier. - 2666-5204. ; 12
-
Journal article (peer-reviewed)abstract
- Background: Head computed tomography (CT) is a guideline recommended method to predict functional outcome after cardiac arrest (CA), but standardized criteria for evaluation are lacking. To date, no prospective trial has systematically validated methods for diagnosing hypoxic-ischaemic encephalopathy (HIE) on CT after CA. We present a protocol for validation of pre-specified radiological criteria for assessment of HIE on CT for neuroprognostication after CA.Methods/design: This is a prospective observational international multicentre substudy of the Targeted Hypothermia versus Targeted Normother-mia after out-of-hospital cardiac arrest (TTM2) trial. Patients still unconscious 48 hours post-arrest at 13 participating hospitals were routinely exam-ined with CT. Original images will be evaluated by examiners blinded to clinical data using a standardized protocol. Qualitative assessment will include evaluation of absence/presence of "severe HIE". Radiodensities will be quantified in pre-specified regions of interest for calculation of grey-white matter ratios (GWR) at the basal ganglia level. Functional outcome will be dichotomized into good (modified Rankin Scale 0-3) and poor (modified Rankin Scale 4-6) at six months post-arrest. Prognostic accuracies for good and poor outcome will be presented as sensitivities and speci-ficities with 95% confidence intervals (using pre-specified cut-offs for quantitative analysis), descriptive statistics (Area Under the Receiver Operating Characteristics Curve), inter-and intra-rater reliabilities according to STARD guidelines.Conclusions: The results from this prospective trial will validate a standardized approach to radiological evaluations of HIE on CT for prediction of functional outcome in comatose CA patients.The TTM2 trial and the TTM2 CT substudy are registered at ClinicalTrials.gov NCT02908308 and NCT03913065.
|
|
| 17. |
- Lindén, Johannes, et al.
(author)
-
Limitations of ICCD detectors and optimized 2D phosphor thermometry
- 2012
-
In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:3
-
Journal article (peer-reviewed)abstract
- This paper presents investigations on the limitations of intensified CCD (ICCD) cameras when performing quantitative 2D temperature measurements using thermographic phosphors. The temperature is evaluated using a two-color ratio technique, which demands high signal linearity of the detector. However, this work shows that the ICCD cameras used suffer from nonlinearity at levels of irradiance that do not necessarily produce particularly high count levels, i.e. well below the saturation limit of the A/D converter. For the phosphor thermometry, this results in false absolute temperature readings and decreased measurement precision. The results show that there is a useful workspace in the irradiance/camera gain combination where the detector should preferably be used. A response function for the ICCD camera used is constructed. Furthermore, in order to perform quantitative measurements, there is an upper limit of counts that should not be exceeded. This limit must be investigated for each experimental configuration since it depends on the characteristics of the specific light source and also varies between different cameras.
|
|
| 18. |
- Lindén, Johannes, et al.
(author)
-
Precision in 2D temperature measurements using the thermographic phosphor BAM
- 2012
-
In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:8
-
Journal article (peer-reviewed)abstract
- Investigation of optimized spatial precision for surface temperature measurements is performed. The temperature is measured by means of two-color ratio imaging with ICCD cameras, using the thermographic phosphor BAM. The precision in temperature is put in relation to the spatial resolution, two quantities which involve a trade-off in this case: the more spatial smoothing the better precision, but also the worse spatial resolution. Two different setups are used in order to investigate the influence of laser shot-to-shot variations, the flat-field correction and image registration process on the precision. In order to achieve high precision it is crucial to operate the ICCD cameras with a gain setting that does not introduce nonlinearity effects at the present level of irradiance. The results provide guidance on the precision to be expected from surface temperature measurements using the two-color ratio technique in combination with thermographic phosphors and also confirm the importance of highly stable and linear ICCD detectors. At room temperature and low spatial resolution the precision is evaluated to 0.4%.
|
|
| 19. |
- Moseby-Knappe, Marion, et al.
(author)
-
Biomarkers of brain injury after cardiac arrest; a statistical analysis plan from the TTM2 trial biobank investigators
- 2022
-
In: Resuscitation Plus. - : Elsevier. - 2666-5204. ; 10
-
Journal article (peer-reviewed)abstract
- Background: Several biochemical markers in blood correlate with the magnitude of brain injury and may be used to predict neurological outcome after cardiac arrest. We present a protocol for the evaluation of prognostic accuracy of brain injury markers after cardiac arrest. The aim is to define the best predictive marker and to establish clinically useful cut-off levels for routine implementation. Methods: Prospective international multicenter trial within the Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest (TTM2) trial in collaboration with Roche Diagnostics International AG. Samples were collected 0, 24, 48, and 72 hours after randomisation (serum) and 0 and 48 hours after randomisation (plasma), and pre-analytically processed at each site before storage in a central biobank. Routine markers neuron-specific enolase (NSE) and S100B, and neurofilament light, total-tau and glial fibrillary acidic protein will be batch analysed using novel Elecsys (R) electrochemiluminescence immunoassays on a Cobas e601 instrument. Results: Statistical analysis will be reported according to the Standards for Reporting Diagnostic accuracy studies (STARD) and will include comparisons for prediction of good versus poor functional outcome at six months post-arrest, by modified Rankin Scale (0-3 vs. 4-6), using logistic regression models and receiver operating characteristics curves, evaluation of mortality at six months according to biomarker levels and establishment of cut-off values for prediction of poor neurological outcome at 95-100% specificities. Conclusions: This prospective trial may establish a standard methodology and clinically appropriate cut-off levels for the optimal biomarker of brain injury which predicts poor neurological outcome after cardiac arrest.
|
|
| 20. |
- Turella, Sara, et al.
(author)
-
The predictive value of highly malignant EEG patterns after cardiac arrest : evaluation of the ERC-ESICM recommendations
-
In: Intensive Care Medicine. - 0342-4642.
-
Journal article (peer-reviewed)abstract
- Purpose: The 2021 guidelines endorsed by the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) recommend using highly malignant electroencephalogram (EEG) patterns (HMEP; suppression or burst-suppression) at > 24 h after cardiac arrest (CA) in combination with at least one other concordant predictor to prognosticate poor neurological outcome. We evaluated the prognostic accuracy of HMEP in a large multicentre cohort and investigated the added value of absent EEG reactivity. Methods: This is a pre-planned prognostic substudy of the Targeted Temperature Management trial 2. The presence of HMEP and background reactivity to external stimuli on EEG recorded > 24 h after CA was prospectively reported. Poor outcome was measured at 6 months and defined as a modified Rankin Scale score of 4–6. Prognostication was multimodal, and withdrawal of life-sustaining therapy (WLST) was not allowed before 96 h after CA. Results: 845 patients at 59 sites were included. Of these, 579 (69%) had poor outcome, including 304 (36%) with WLST due to poor neurological prognosis. EEG was recorded at a median of 71 h (interquartile range [IQR] 52–93) after CA. HMEP at > 24 h from CA had 50% [95% confidence interval [CI] 46–54] sensitivity and 93% [90–96] specificity to predict poor outcome. Specificity was similar (93%) in 541 patients without WLST. When HMEP were unreactive, specificity improved to 97% [94–99] (p = 0.008). Conclusion: The specificity of the ERC-ESICM-recommended EEG patterns for predicting poor outcome after CA exceeds 90% but is lower than in previous studies, suggesting that large-scale implementation may reduce their accuracy. Combining HMEP with an unreactive EEG background significantly improved specificity. As in other prognostication studies, a self-fulfilling prophecy bias may have contributed to observed results.
|
|
