scholarly journals Application of the EANM practical guidance on uncertainty analysis for MRT absorbed dose calculations on clinical cases

2020 ◽  
Author(s):  
Domenico Finocchiaro ◽  
Jonathan I Gear ◽  
Federica Fioroni ◽  
Glenn D Flux ◽  
Iain Murray ◽  
...  
Keyword(s):  
Uncertainty Analysis ◽  
Spatial Resolution ◽  
Absorbed Dose ◽  
Dose Calculations ◽  
Large Sample ◽  
Wide Range ◽  
Practical Guidance ◽  
Dose Uncertainty ◽  
The Impact ◽  
Clinical Cases

Abstract Background Internal dosimetry evaluation consists of a multi-step process ranging from imaging acquisition to absorbed dose calculations. Assessment of uncertainty is complicated and, for that reason, it is commonly ignored in clinical routine. However, it is essential for adequate interpretation of the results. Recently, the EANM published a practical guidance on uncertainty analysis for molecular radiotherapy based on the application of the law of propagation of uncertainty. In this study, we investigated the overall uncertainty on a large sample of patient following the EANM guidelines. The aim of this study was to provide an indication of the typical uncertainties that may be expected from performing dosimetry, to determine parameters that have the greatest effect on the accuracy of calculations and to consider the potential improvements that could be made if these effects were reduced. Results Absorbed doses and the relative uncertainties were calculated for a sample of 49 patients and a total of 154 tumours. A wide range of relative dose uncertainty values was observed (14 - 102%). Uncertainties associated to each quantity along the dose calculation chain (i.e. Volume, Recovery Coefficient, Calibration Factor, Activity, Time-Activity Curve Fitting, Cumulated Activity and Absorbed Dose) were estimated. An equation was derived to describe relationship between the uncertainty in the absorbed dose and the volume. The largest source of error was the VOI delineation. By postulating different values of FHWM, the impact of the imaging system spatial resolution on the uncertainties was investigated. Discussion To the best of our knowledge, this is the first analysis of uncertainty in MRT based on a large sample of clinical cases. Wide inter-lesion variability of dose uncertainty was observed. Hence, a proper assessment of the uncertainties associated with the calculations should be considered as a basic scientific standard. A model for a quick estimate of uncertainty without implementing the entire error propagation schema, which may be useful in clinical practice, was presented. Ameliorating spatial resolution may be in future the key factor for accurate absorbed dose assessment.

scholarly journals Uncertainty analysis of tumour absorbed dose calculations in molecular radiotherapy

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Domenico Finocchiaro ◽  
Jonathan I. Gear ◽  
Federica Fioroni ◽  
Glenn D. Flux ◽  
Iain Murray ◽  
...  
Keyword(s):  
Uncertainty Analysis ◽  
Spatial Resolution ◽  
Absorbed Dose ◽  
Dose Assessment ◽  
Dose Calculations ◽  
Time Activity ◽  
Molecular Radiotherapy ◽  
Wide Range ◽  
Dose Uncertainty ◽  
The Impact

Abstract Background Internal dosimetry evaluation consists of a multi-step process ranging from imaging acquisition to absorbed dose calculations. Assessment of uncertainty is complicated and, for that reason, it is commonly ignored in clinical routine. However, it is essential for adequate interpretation of the results. Recently, the EANM published a practical guidance on uncertainty analysis for molecular radiotherapy based on the application of the law of propagation of uncertainty. In this study, we investigated the overall uncertainty on a sample of a patient following the EANM guidelines. The aim of this study was to provide an indication of the typical uncertainties that may be expected from performing dosimetry, to determine parameters that have the greatest effect on the accuracy of calculations and to consider the potential improvements that could be made if these effects were reduced. Results Absorbed doses and the relative uncertainties were calculated for a sample of 49 patients and a total of 154 tumours. A wide range of relative absorbed dose uncertainty values was observed (14–102%). Uncertainties associated with each quantity along the absorbed dose calculation chain (i.e. volume, recovery coefficient, calibration factor, activity, time-activity curve fitting, time-integrated activity and absorbed dose) were estimated. An equation was derived to describe the relationship between the uncertainty in the absorbed dose and the volume. The largest source of error was the VOI delineation. By postulating different values of FWHM, the impact of the imaging system spatial resolution on the uncertainties was investigated. Discussion To the best of our knowledge, this is the first analysis of uncertainty in molecular radiotherapy based on a cohort of clinical cases. Wide inter-lesion variability of absorbed dose uncertainty was observed. Hence, a proper assessment of the uncertainties associated with the calculations should be considered as a basic scientific standard. A model for a quick estimate of uncertainty without implementing the entire error propagation schema, which may be useful in clinical practice, was presented. Ameliorating spatial resolution may be in future the key factor for accurate absorbed dose assessment.

scholarly journals Uncertainty analysis of tumour absorbed dose calculations in Molecular Radiotherapy

2020 ◽  
Author(s):  
Domenico Finocchiaro ◽  
Jonathan I Gear ◽  
Federica Fioroni ◽  
Glenn D Flux ◽  
Iain Murray ◽  
...  
Keyword(s):  
Uncertainty Analysis ◽  
Spatial Resolution ◽  
Absorbed Dose ◽  
Dose Assessment ◽  
Dose Calculations ◽  
Time Activity ◽  
Molecular Radiotherapy ◽  
Wide Range ◽  
Dose Uncertainty ◽  
The Impact

Abstract Background: Internal dosimetry evaluation consists of a multi-step process ranging from imaging acquisition to absorbed dose calculations. Assessment of uncertainty is complicated and, for that reason, it is commonly ignored in clinical routine. However, it is essential for adequate interpretation of the results. Recently, the EANM published a practical guidance on uncertainty analysis for molecular radiotherapy based on the application of the law of propagation of uncertainty. In this study, we investigated the overall uncertainty on a sample of patient following the EANM guidelines. The aim of this study was to provide an indication of the typical uncertainties that may be expected from performing dosimetry, to determine parameters that have the greatest effect on the accuracy of calculations and to consider the potential improvements that could be made if these effects were reduced.Results: Absorbed doses and the relative uncertainties were calculated for a sample of 49 patients and a total of 154 tumours. A wide range of relative absorbed dose uncertainty values was observed (14 - 102%). Uncertainties associated with each quantity along the absorbed dose calculation chain (i.e. Volume, Recovery Coefficient, Calibration Factor, Activity, Time-Activity Curve Fitting, Time-Integrated Activity and Absorbed Dose) were estimated. An equation was derived to describe relationship between the uncertainty in the absorbed dose and the volume. The largest source of error was the VOI delineation. By postulating different values of FWHM, the impact of the imaging system spatial resolution on the uncertainties was investigated.Discussion: To the best of our knowledge, this is the first analysis of uncertainty in molecular radiotherapy based on a cohort of clinical cases. Wide inter-lesion variability of absorbed dose uncertainty was observed. Hence, a proper assessment of the uncertainties associated with the calculations should be considered as a basic scientific standard. A model for a quick estimate of uncertainty without implementing the entire error propagation schema, which may be useful in clinical practice, was presented. Ameliorating spatial resolution may be in future the key factor for accurate absorbed dose assessment.

scholarly journals Uncertainty analysis of tumour absorbed dose calculations in Molecular Radiotherapy

2020 ◽  
Author(s):  
Domenico Finocchiaro ◽  
Jonathan I Gear ◽  
Federica Fioroni ◽  
Glenn D Flux ◽  
Iain Murray ◽  
...  
Keyword(s):  
Uncertainty Analysis ◽  
Spatial Resolution ◽  
Absorbed Dose ◽  
Dose Assessment ◽  
Dose Calculations ◽  
Time Activity ◽  
Molecular Radiotherapy ◽  
Wide Range ◽  
Dose Uncertainty ◽  
The Impact

Abstract Background: Internal dosimetry evaluation consists of a multi-step process ranging from imaging acquisition to absorbed dose calculations. Assessment of uncertainty is complicated and, for that reason, it is commonly ignored in clinical routine. However, it is essential for adequate interpretation of the results. Recently, the EANM published a practical guidance on uncertainty analysis for molecular radiotherapy based on the application of the law of propagation of uncertainty. In this study, we investigated the overall uncertainty on a sample of patient following the EANM guidelines. The aim of this study was to provide an indication of the typical uncertainties that may be expected from performing dosimetry, to determine parameters that have the greatest effect on the accuracy of calculations and to consider the potential improvements that could be made if these effects were reduced.Results: Absorbed doses and the relative uncertainties were calculated for a sample of 49 patients and a total of 154 tumours. A wide range of relative absorbed dose uncertainty values was observed (14 - 102%). Uncertainties associated with each quantity along the absorbed dose calculation chain (i.e. Volume, Recovery Coefficient, Calibration Factor, Activity, Time-Activity Curve Fitting, Time-Integrated Activity and Absorbed Dose) were estimated. An equation was derived to describe relationship between the uncertainty in the absorbed dose and the volume. The largest source of error was the VOI delineation. By postulating different values of FWHM, the impact of the imaging system spatial resolution on the uncertainties was investigated.Discussion: To the best of our knowledge, this is the first analysis of uncertainty in molecular radiotherapy based on a cohort of clinical cases. Wide inter-lesion variability of absorbed dose uncertainty was observed. Hence, a proper assessment of the uncertainties associated with the calculations should be considered as a basic scientific standard. A model for a quick estimate of uncertainty without implementing the entire error propagation schema, which may be useful in clinical practice, was presented. Ameliorating spatial resolution may be in future the key factor for accurate absorbed dose assessment.

scholarly journals EANM practical guidance on uncertainty analysis for molecular radiotherapy absorbed dose calculations

2018 ◽  
Vol 45 (13) ◽  
pp. 2456-2474 ◽  
Author(s):  
Jonathan I. Gear ◽  
Maurice G. Cox ◽  
Johan Gustafsson ◽  
Katarina Sjögreen Gleisner ◽  
Iain Murray ◽  
...  
Keyword(s):  
Uncertainty Analysis ◽  
Absorbed Dose ◽  
Dose Calculations ◽  
Molecular Radiotherapy ◽  
Practical Guidance

scholarly journals Scale dependence of cirrus heterogeneity effects. Part II: MODIS NIR and SWIR channels

2018 ◽  
Vol 18 (16) ◽  
pp. 12105-12121 ◽  
Author(s):  
Thomas Fauchez ◽  
Steven Platnick ◽  
Tamás Várnai ◽  
Kerry Meyer ◽  
Céline Cornet ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Spatial Resolution ◽  
Thermal Infrared ◽  
Radiative Effects ◽  
Ice Clouds ◽  
Plane Parallel ◽  
Wide Range ◽  
The Impact ◽  
Side Illumination

Abstract. In a context of global climate change, the understanding of the radiative role of clouds is crucial. On average, ice clouds such as cirrus have a significant positive radiative effect, but under some conditions the effect may be negative. However, many uncertainties remain regarding the role of ice clouds on Earth's radiative budget and in a changing climate. Global satellite observations are particularly well suited to monitoring clouds, retrieving their characteristics and inferring their radiative impact. To retrieve ice cloud properties (optical thickness and ice crystal effective size), current operational algorithms assume that each pixel of the observed scene is plane-parallel and homogeneous, and that there is no radiative connection between neighboring pixels. Yet these retrieval assumptions are far from accurate, as real radiative transfer is 3-D. This leads to the plane-parallel and homogeneous bias (PPHB) plus the independent pixel approximation bias (IPAB), which impacts both the estimation of top-of-the-atmosphere (TOA) radiation and the retrievals. An important factor that determines the impact of these assumptions is the sensor spatial resolution. High-spatial-resolution pixels can better represent cloud variability (low PPHB), but the radiative path through the cloud can involve many pixels (high IPAB). In contrast, low-spatial-resolution pixels poorly represent the cloud variability (high PPHB), but the radiation is better contained within the pixel field of view (low IPAB). In addition, the solar and viewing geometry (as well as cloud optical properties) can modulate the magnitude of the PPHB and IPAB. In this, Part II of our study, we simulate TOA 0.86 and 2.13 µm solar reflectances over a cirrus uncinus scene produced by the 3DCLOUD model. Then, 3-D radiative transfer simulations are performed with the 3DMCPOL code at spatial resolutions ranging from 50 m to 10 km, for 12 viewing geometries and nine solar geometries. It is found that, for simulated nadir observations taken at resolution higher than 2.5 km, horizontal radiation transport (HRT) dominates biases between 3-D and 1-D reflectance calculations, but these biases are mitigated by the side illumination and shadowing effects for off-zenith solar geometries. At resolutions coarser than 2.5 km, PPHB dominates. For off-nadir observations at resolutions higher than 2.5 km, the effect that we call THEAB (tilted and homogeneous extinction approximation bias) due to the oblique line of sight passing through many cloud columns contributes to a large increase of the reflectances, but 3-D radiative effects such as shadowing and side illumination for oblique Sun are also important. At resolutions coarser than 2.5 km, the PPHB is again the dominant effect. The magnitude and resolution dependence of PPHB and IPAB is very different for visible, near-infrared and shortwave infrared channels compared with the thermal infrared channels discussed in Part I of this study. The contrast of 3-D radiative effects between solar and thermal infrared channels may be a significant issue for retrieval techniques that simultaneously use radiative measurements across a wide range of solar reflectance and infrared wavelengths.

Uncertainty analysis of absorbed dose calculations from thermoluminescence dosimeters

1992 ◽  
Vol 19 (6) ◽  
pp. 1427-1433 ◽  
Author(s):  
T. H. Kirby ◽  
W. F. Hanson ◽  
D. A. Johnston
Keyword(s):  
Uncertainty Analysis ◽  
Absorbed Dose ◽  
Dose Calculations

scholarly journals THEORETICAL ASPECTS OF IMPLEMENTATION OF ORGANIZATIONAL CHANGES UNDER UNCERTAINTY

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Yu Opanasiuk ◽  
M. Maryn
Keyword(s):  
Decision Making ◽  
Qualitative Analysis ◽  
Uncertainty Analysis ◽  
Steady Increase ◽  
Decision Making Process ◽  
Organizational Changes ◽  
Publishing Activity ◽  
Risk Manager ◽  
Wide Range ◽  
The Impact

In the work the bibliometric analysis of scientific works on definition of concepts "organizational changes" and "uncertainty" is made. There is a steady increase in attention to the problems of organization management in conditions of uncertainty. This emphasizes the relevance of the research topic and the search for interconnected promising areas for future research. The growth of publishing activity made it possible to conduct a qualitative analysis based on a sample of 515 publications (articles and conference proceedings), the authors of which study organizational changes in risk conditions. The articles were selected from the Web of Science in a systematic process of search and selection over the past 5 years in order to obtain the most up-to-date views on the problem. The analysis shows that despite the fact that the main number of relevant publications is growing over time, but in general is contained in journals related to ecology and environmental management. Based on selected publications using VOSviewer, the results of the analysis were visualized to provide a better understanding of key contextual areas and authors of research, publishing activity over the years and the appropriate number of citations. Uncertainty is seen as a factor that overshadows the decision-making process. The risk manager often considers uncertainty in terms of the decision-making process, estimating decision errors and costs. Important components of uncertainty analysis are qualitative analysis, which identifies uncertainty, and quantitative analysis of the impact of uncertainty on decision-making and communication. Uncertainty analysis depends on the problem. Thus, the uncertainty analysis used in the environmental, economic and general literature covers a wide range of different methods. Given the results obtained, the uncertainty analysis varies from simple descriptive procedures to quantifying uncertainty and more formal decision-making procedures. The authors define and analyze in detail the concept of "uncertainty" in terms of its essence and structure.

scholarly journals Scale dependence of cirrus heterogeneity effects. Part II: MODIS VNIR and SWIR channels

2018 ◽  
Author(s):  
Thomas Fauchez ◽  
Steven Platnick ◽  
Tamás Várnai ◽  
Kerry Meyer ◽  
Céline Cornet ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Spatial Resolution ◽  
Radiation Transport ◽  
Oblique Line ◽  
Dominant Effect ◽  
Plane Parallel ◽  
Wide Range ◽  
The Impact ◽  
Side Illumination

Abstract. The understanding of the radiative role of clouds is crucial. Ice clouds such as cirrus have, on average, a significant positive radiative effect, while in some conditions it may be negative. However, many uncertainties remain on the role of this type of clouds on Earth's radiative budget and in a changing climate. Global satellite observations are particularly well suited to monitor clouds, retrieve their characteristics and infer their radiative impact. To retrieve ice cloud properties (optical thickness and ice crystal effective size), current operational algorithms assume that each pixel of the observed scene is plane-parallel and homogeneous, and that there is no radiative connection between neighboring pixels. This retrieval representation is far from the reality, where the radiative transfer is 3D, leading to the plane parallel and homogeneous bias (PPHB) and the independent pixel approximation bias (IPAB) impacting both the estimation of top of the atmosphere (TOA) radiation and retrievals. An important factor that constrains the impact of these assumptions is the sensor spatial resolution. High spatial resolution pixels can better represent cloud variability (low PPHB) though the radiative path through the cloud can involve many pixels (high IPAB). In contrast, low spatial resolution pixels poorly represent the cloud variability (high PPHB) but the radiation is better contained within the pixel field of view (low IPAB). In addition, the solar and viewing geometry (as well as cloud optical properties) can modulate the magnitude of the PPHB and IPAB. In this Part II of our study, we have simulated TOA 0.86 μm and 2:13 μm solar reflectances over a cirrus uncinus scene produced by the 3DCLOUD model. Then, 3D radiative transfer simulations are performed by the 3DMCPOL code at spatial resolutions ranging from 50 m to 10 km, for twelve viewing geometries and nine solar geometries. It is found that, for simulated nadir observations taken at resolution higher than 2.5 km, horizontal radiation transport (HRT) dominates biases between 3D and 1D reflectance calculations, but it is mitigated by the side illumination effect for off-zenith solar geometries. At resolutions coarser than 2.5 km, PPHB dominates. For off-nadir observations at resolutions higher than 2.5 km, the dominant effect is that the oblique line of sight passes through many cloud columns, but other 3D effects are also important. Similar to nadir simulations, side illumination effects mitigate the HRT. At resolutions coarser than 2.5 km, the PPHB is again the dominant effect. The magnitude and resolution-dependence of PPHB and IPAB is very different for visible, near-infrared, and short-wave infrared channels compared with the thermal infrared channels discussed in Part I of this study. This strong wavelength dependency of cirrus cloud 3D radiative effects may be a significant issue for retrieval techniques that simultaneously use radiative measurements across a wide range of solar reflectances and infrared wavelengths.

scholarly journals Optical-Radiation-Calorimeter Refinement by Virtual-Sensitivity Analysis

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1167 ◽  
Author(s):  
Lancia Hubley ◽  
Jackson Roberts ◽  
Juergen Meyer ◽  
Alicia Moggré ◽  
Steven Marsh
Keyword(s):  
Spatial Resolution ◽  
Optical Radiation ◽  
Environmental Influence ◽  
Absorbed Dose ◽  
Detector System ◽  
Optical Systems ◽  
Novel Approach ◽  
Heat Expansion ◽  
Path Lengths ◽  
The Impact

Digital holographic interferometry (DHI) radiation dosimetry has been proposed as an experimental metrology technique for measuring absorbed radiation doses to water with high spatial resolution via noninvasive optical calorimetry. The process involves digitally recording consecutive interference patterns resulting from variations in the refractive index as a function of the radiation-absorbed dose. Experiments conducted on prototype optical systems revealed the approach to be feasible but strongly dependent on environmental-influence quantities and setup configuration. A virtual dosimeter reflecting the prototype was created in a commercial optical modelling package. A number of virtual phantoms were developed to characterize the performance of the dosimeter under ideal conditions and with simulated disruptions in environmental-influence quantities, such as atmospheric and temperature perturbations as well as mechanical vibrations. Investigations into the error response revealed that slow drifts in atmospheric parameters and heat expansion caused the measured dose to vary between measurements, while atmospheric fluctuations and vibration contributed to system noise, significantly lowering the spatial resolution of the detector system. The impact of these effects was found to be largely mitigated with equalisation of the dosimeter’s reference and object path lengths, and by miniaturising the detector. Equalising path lengths resulted in a reduction of 97.5% and 96.9% in dosimetric error introduced by heat expansion and atmospheric drift, respectively, while miniaturisation of the dosimeter was found to reduce its sensitivity to vibrations and atmospheric turbulence by up to 41.7% and 54.5%, respectively. This work represents a novel approach to optical-detector refinement in which metrics from medical imaging were adapted into software and applied to a a virtual-detector system. This methodology was found to be well-suited for the optimization of a digital holographic interferometer.

THE IMPACT OF LEADERSHIP PRACTICES TO TEAM MEMBERS’ SATISFACTION

2009 ◽  
Vol 8 (1) ◽  
Author(s):  
Chalimah .
Keyword(s):  
Conflict Resolution ◽  
Leadership Practices ◽  
Hotel Industry ◽  
Leader Behavior ◽  
Team Leader ◽  
Shop Floor ◽  
Team Members ◽  
Top Executives ◽  
Wide Range ◽  
The Impact

eamwork is becoming increasingly important to wide range of operations. It applies to all levels of the company. It is just as important for top executives as it is to middle management, supervisors and shop floor workers. Poor teamwork at any level or between levels can seriously damage organizational effectiveness. The focus of this paper was therefore to examine whether leadership practices consist of team leader behavior, conflict resolution style and openness in communication significantly influenced the team member’s satisfaction in hotel industry. Result indicates that team leader behavior and the conflict resolution style significantly influenced team member satisfaction. It was surprising that openness in communication did not affect significantly to the team members’ satisfaction.

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