The Experts below are selected from a list of 29001 Experts worldwide ranked by ideXlab platform
Christos V Ioannou - One of the best experts on this subject based on the ideXlab platform.
-
Spatial Distribution of Abdominal Aortic Aneurysm Surface Expansion and Correlation With Maximum Diameter and Volume Growth.
Annals of Vascular Surgery, 2019Co-Authors: Konstantinos Tzirakis, Nikolaos Kontopodis, Eleni Metaxa, Christos V Ioannou, Yannis PapaharilaouAbstract:Background Abdominal aortic aneurysm (AAA) growth rate, measured as Maximum Diameter (Dmax) change over time, is used as a surrogate marker of rupture risk. However, AAA expansion presents significant spatial variability. We aim to record the spatial distribution of regional wall surface expansion. Methods Thirty AAAs were retrospectively studied. Each AAA had one baseline and at least one follow-up computed tomography scan. Three-dimensional AAA models were reconstructed, and change in Dmax and total aneurysm volume was recorded to calculate annual growth rates. Regional surface growth was quantified using the VascForm algorithm, which is based on nonrigid point cloud registration and iterative closest point analysis. Maximum and average surface growths were calculated and correlated with the Diameter/volume growth rates. Furthermore, to identify potential correlation between Maximum thrombus (intraluminal thrombus) thickness and Maximum surface growth, as well as between peak wall stress (PWS) and surface growth, their colocalization was examined. Results The median average annual surface growth was 6% (0%–28%), and the Maximum surface growth 24% (11%–238%). There was strong evidence of a moderate correlation between Dmax and average as well as Maximum surface growth. Regarding volumes, there was strong evidence of a very strong association with average surface growth rate and a moderate association with Maximum surface growth rate (rho: 0.91, P Conclusions More than half of the lesions display Maximum growth away from Dmax, suggesting that a more accurate method of analyzing AAA growth needs to be established in clinical practice that will take into account local surface growth.
-
the obsolete Maximum Diameter criterion the evident role of biomechanical pressure indices the new role of hemodynamic flow indices and the multi modal approach to the rupture risk assessment of abdominal aortic aneurysms
Annals of Vascular Diseases, 2018Co-Authors: Nikolaos Kontopodis, Konstantinos Tzirakis, Christos V IoannouAbstract:Although the therapeutic management of abdominal aortic aneurysms (AAAs) is currently based on the Maximum Diameter criterion, this has often proved inaccurate and misleading. Conversely, the biomechanical approach, which takes into account the pressure-induced wall stress exerted at every point throughout the aneurysmal surface, has been proven superior in predicting the rupture risk of AAAs, and its value is being increasingly recognized among physicians. More recently, hemodynamic indices, such as flow-induced wall shear stresses, have been indicated as potentially significant determinants of AAA natural history. Ultimately, a statistical model that takes into account all these factors may be relevant for making a sound prediction of the rupture risk of aneurysms and optimizing the management of these patients.
-
Value of volume measurements in evaluating abdominal aortic aneurysms growth rate and need for surgical treatment
European Journal of Radiology, 2014Co-Authors: Nikolaos Kontopodis, Eleni Metaxa, Yannis Papaharilaou, Efstratios Georgakarakos, D. Tsetis, Christos V IoannouAbstract:Abstract Purpose To examine whether indices other than the traditionally used abdominal aortic aneurysm (AAA) Maximum Diameter, such as AAA volume, intraluminal thrombus (ILT) thickness and ILT volume, may be superior to evaluate aneurismal enlargement. Materials and methods Thirty-four small AAAs (initially presenting a Maximum Diameter AAAs were divided according to outcome (surveillance vs. elective repair after follow-up which is based on the Maximum Diameter criterion) and according to growth rate (high vs. low) based on four indices. Contingency between groups of high/low growth rate regarding each of the four indices on one hand and those regarding need for surgical repair on the other was assessed. Results A strong correlation between growth rates of Maximum Diameter and those of AAA and ILT volumes could be established. Evaluation of contingency between groups of outcome and those of growth rate revealed significant associations only for AAA and ILT volumes. Subsequently AAAs with a rapid volumetric increase over time had a likelihood ratio of 10 to be operated compared to those with a slower enlargement. Regarding increase of Maximum Diameter, likelihood ratio between AAAs with rapid and those with slow expansion was only 3. Conclusion Growth rate of aneurysms regarding 3Dimensional indices of AAA and ILT volumes is significantly associated with the need for surgical intervention while the same does not hold for growth rates determined by 2Dimensional indices of Maximum Diameter and ILT thickness.
-
discrepancies in determination of abdominal aortic aneurysms Maximum Diameter and growth rate using axial and orhtogonal computed tomography measurements
European Journal of Radiology, 2013Co-Authors: Nikolaos Kontopodis, Eleni Metaxa, Michalis N Gionis, Yannis Papaharilaou, Christos V IoannouAbstract:Abstract Purpose Maximum Diameter and growth rate of abdominal aortic aneurysms (AAAs) which are currently used as the only variables to set the indication for elective repair are recorded through computed tomography (CT) measurements on an axial plane or on an orthogonal plane that is perpendicular to vessel centerline, interchangeably. We will attempt to record possible discrepancies between the two methods, identify whether such differences could influence therapeutic decisions and determine in which cases this should be expected. Materials and methods We retrospectively reviewed sixty CT-scans performed in thirty-nine patients. Three-dimensional reconstruction of AAAs has been performed and differences in Maximum Diameter measured on axial and orthogonal planes were recorded. A measure for asymmetry was introduced termed ShapeIndex defined as the value of section minor over major axis and was related with differences in Maximum Diameter recordings. Growth rates were also determined using both axial and orthogonal measurements. Results Axial measurements overestimate Maximum Diameter by 2±2.7mm ( P 5.5cm indicating the need for intervention whereas, orthogonal Diameter was below that threshold. Asymmetry of the axial sections with ShapeIndex ≤0.8 was found to be related to an overestimation of Maximum Diameter by >5mm. There were no significant differences in growth rates when determined using orthogonal or axial measurements in both examinations (median growth rate: 2.3mm and 3.3mm respectively P =0.2). However there were significant differences when orthogonal measurements were used at initial and axial measurements used at follow-up examination or vice versa (median growth rate: 4.9mm and 0.9mm respectively P Conclusions Although the mean difference between measurements is low there is a wide range among cases, mainly observed in asymmetrical AAAs. ShapeIndex may identify those which are more likely to be misestimated. CT measurements performed to establish AAA growth rates should consistently use either the axial or orthogonal technique to avoid inaccuracies from occurring.
Chulhwa Song - One of the best experts on this subject based on the ideXlab platform.
-
a mechanistic model for predicting the Maximum Diameter of vapor bubbles in a subcooled boiling flow
International Journal of Heat and Mass Transfer, 2016Co-Authors: Nhan Hien Hoang, Chulhwa SongAbstract:Abstract Vapor bubbles attached to the heated surface in a subcooled boiling flow usually reach their Maximum size during the latter phase of the bubble growth period when the liquid microlayer trapped under them is almost depleted. The heat transfer at the bubble during this phase involves only the transient heat conduction through a so-called relaxation microlayer surrounding the lower bubble surface and the condensation at the bubble dome. On this physical base, a new mechanistic model for predicting the Maximum Diameter of attached vapor bubbles in a subcooled boiling flow is proposed in this study. The new model is derived from the lumped energy balance for the bubbles. It is then validated using published experimental databases on the Maximum bubble Diameter measured for subcooled boiling flows of water under a wide range of flow conditions. A good agreement between the predicted Maximum bubble Diameter and the experimental one is obtained. The average relative error is less than about 35.5%. This model is expectedly worthy of being used in the analysis of subcooled boiling flows.
Mohammad Hamady - One of the best experts on this subject based on the ideXlab platform.
-
variation in Maximum Diameter measurements of descending thoracic aortic aneurysms using unformatted planes versus images corrected to aortic centerline
European Journal of Vascular and Endovascular Surgery, 2014Co-Authors: Nung Rudarakanchana, Colin Bicknell, N J W Cheshire, N Burfitt, A Chapman, Mohammad HamadyAbstract:Objective Evaluation of variation in descending thoracic aortic aneurysm (dTAA) Diameters measured on CT scans in different planes and by different observers and the potential impact on treatment decisions. Methods CT angiography of dTAA ( N = 20) were assessed by three specialists, with measurements repeated after 1 month. Calliper measurements of Maximum external Diameters were made on unformatted images and perpendicular to the aneurysm centerline after image processing (corrected). Repeatability was assessed using Bland–Altman plots. Results Maximum corrected Diameter measurements were smaller than axial measurements (66.3 ± 7.9 mm vs. 74.9 ± 20.9 mm, p p p Conclusion Corrected Diameters were smaller than axial Diameters, could be measured with higher repeatability, and were subject to less interobserver variability. Using corrected versus axial measurements would have changed management decisions in up to half of the cases in this study.
Steven W Cheung - One of the best experts on this subject based on the ideXlab platform.
-
a spheroid weighted axis converter of vestibular schwannoma size Maximum Diameter and cisternal volume
Otolaryngology-Head and Neck Surgery, 2013Co-Authors: Brandon L Prendes, Eli R Groppo, Catherine Reynolds, Andrew T Parsa, Steven W CheungAbstract:ObjectivesTo evaluate spheroid models of vestibular schwannoma (VS) size for bidirectional conversion of Maximum Diameter in the cistern and 3-dimensional volume.Study DesignMethodological study.SettingAcademic tertiary referral center.Subjects and MethodsMagnetic resonance imaging studies from 91 patients with VS from 2003 to 2011 were analyzed. Linear measurements defining meatal and cisternal components were extracted. Geometrically based conformal models of tumor volume were compared with measured tumor volume using a semiautomated computerized tracing method. Models were inverted to predict Maximum axial cisternal length at the level of the internal auditory canal (IAC).ResultsA spheroid-weighted axis converter (SWC) of VS size was identified by minimizing input measurement parameters while maximizing output prediction performance. Computation steps of tumor volumes were (1) meatal—measure tumor lengths along the IAC and at the porus acusticus and take the average of a cone and cylinder and (2) ciste...
Nikolaos Kontopodis - One of the best experts on this subject based on the ideXlab platform.
-
Spatial Distribution of Abdominal Aortic Aneurysm Surface Expansion and Correlation With Maximum Diameter and Volume Growth.
Annals of Vascular Surgery, 2019Co-Authors: Konstantinos Tzirakis, Nikolaos Kontopodis, Eleni Metaxa, Christos V Ioannou, Yannis PapaharilaouAbstract:Background Abdominal aortic aneurysm (AAA) growth rate, measured as Maximum Diameter (Dmax) change over time, is used as a surrogate marker of rupture risk. However, AAA expansion presents significant spatial variability. We aim to record the spatial distribution of regional wall surface expansion. Methods Thirty AAAs were retrospectively studied. Each AAA had one baseline and at least one follow-up computed tomography scan. Three-dimensional AAA models were reconstructed, and change in Dmax and total aneurysm volume was recorded to calculate annual growth rates. Regional surface growth was quantified using the VascForm algorithm, which is based on nonrigid point cloud registration and iterative closest point analysis. Maximum and average surface growths were calculated and correlated with the Diameter/volume growth rates. Furthermore, to identify potential correlation between Maximum thrombus (intraluminal thrombus) thickness and Maximum surface growth, as well as between peak wall stress (PWS) and surface growth, their colocalization was examined. Results The median average annual surface growth was 6% (0%–28%), and the Maximum surface growth 24% (11%–238%). There was strong evidence of a moderate correlation between Dmax and average as well as Maximum surface growth. Regarding volumes, there was strong evidence of a very strong association with average surface growth rate and a moderate association with Maximum surface growth rate (rho: 0.91, P Conclusions More than half of the lesions display Maximum growth away from Dmax, suggesting that a more accurate method of analyzing AAA growth needs to be established in clinical practice that will take into account local surface growth.
-
the obsolete Maximum Diameter criterion the evident role of biomechanical pressure indices the new role of hemodynamic flow indices and the multi modal approach to the rupture risk assessment of abdominal aortic aneurysms
Annals of Vascular Diseases, 2018Co-Authors: Nikolaos Kontopodis, Konstantinos Tzirakis, Christos V IoannouAbstract:Although the therapeutic management of abdominal aortic aneurysms (AAAs) is currently based on the Maximum Diameter criterion, this has often proved inaccurate and misleading. Conversely, the biomechanical approach, which takes into account the pressure-induced wall stress exerted at every point throughout the aneurysmal surface, has been proven superior in predicting the rupture risk of AAAs, and its value is being increasingly recognized among physicians. More recently, hemodynamic indices, such as flow-induced wall shear stresses, have been indicated as potentially significant determinants of AAA natural history. Ultimately, a statistical model that takes into account all these factors may be relevant for making a sound prediction of the rupture risk of aneurysms and optimizing the management of these patients.
-
Value of volume measurements in evaluating abdominal aortic aneurysms growth rate and need for surgical treatment
European Journal of Radiology, 2014Co-Authors: Nikolaos Kontopodis, Eleni Metaxa, Yannis Papaharilaou, Efstratios Georgakarakos, D. Tsetis, Christos V IoannouAbstract:Abstract Purpose To examine whether indices other than the traditionally used abdominal aortic aneurysm (AAA) Maximum Diameter, such as AAA volume, intraluminal thrombus (ILT) thickness and ILT volume, may be superior to evaluate aneurismal enlargement. Materials and methods Thirty-four small AAAs (initially presenting a Maximum Diameter AAAs were divided according to outcome (surveillance vs. elective repair after follow-up which is based on the Maximum Diameter criterion) and according to growth rate (high vs. low) based on four indices. Contingency between groups of high/low growth rate regarding each of the four indices on one hand and those regarding need for surgical repair on the other was assessed. Results A strong correlation between growth rates of Maximum Diameter and those of AAA and ILT volumes could be established. Evaluation of contingency between groups of outcome and those of growth rate revealed significant associations only for AAA and ILT volumes. Subsequently AAAs with a rapid volumetric increase over time had a likelihood ratio of 10 to be operated compared to those with a slower enlargement. Regarding increase of Maximum Diameter, likelihood ratio between AAAs with rapid and those with slow expansion was only 3. Conclusion Growth rate of aneurysms regarding 3Dimensional indices of AAA and ILT volumes is significantly associated with the need for surgical intervention while the same does not hold for growth rates determined by 2Dimensional indices of Maximum Diameter and ILT thickness.
-
discrepancies in determination of abdominal aortic aneurysms Maximum Diameter and growth rate using axial and orhtogonal computed tomography measurements
European Journal of Radiology, 2013Co-Authors: Nikolaos Kontopodis, Eleni Metaxa, Michalis N Gionis, Yannis Papaharilaou, Christos V IoannouAbstract:Abstract Purpose Maximum Diameter and growth rate of abdominal aortic aneurysms (AAAs) which are currently used as the only variables to set the indication for elective repair are recorded through computed tomography (CT) measurements on an axial plane or on an orthogonal plane that is perpendicular to vessel centerline, interchangeably. We will attempt to record possible discrepancies between the two methods, identify whether such differences could influence therapeutic decisions and determine in which cases this should be expected. Materials and methods We retrospectively reviewed sixty CT-scans performed in thirty-nine patients. Three-dimensional reconstruction of AAAs has been performed and differences in Maximum Diameter measured on axial and orthogonal planes were recorded. A measure for asymmetry was introduced termed ShapeIndex defined as the value of section minor over major axis and was related with differences in Maximum Diameter recordings. Growth rates were also determined using both axial and orthogonal measurements. Results Axial measurements overestimate Maximum Diameter by 2±2.7mm ( P 5.5cm indicating the need for intervention whereas, orthogonal Diameter was below that threshold. Asymmetry of the axial sections with ShapeIndex ≤0.8 was found to be related to an overestimation of Maximum Diameter by >5mm. There were no significant differences in growth rates when determined using orthogonal or axial measurements in both examinations (median growth rate: 2.3mm and 3.3mm respectively P =0.2). However there were significant differences when orthogonal measurements were used at initial and axial measurements used at follow-up examination or vice versa (median growth rate: 4.9mm and 0.9mm respectively P Conclusions Although the mean difference between measurements is low there is a wide range among cases, mainly observed in asymmetrical AAAs. ShapeIndex may identify those which are more likely to be misestimated. CT measurements performed to establish AAA growth rates should consistently use either the axial or orthogonal technique to avoid inaccuracies from occurring.
