Surface Factors Research Articles

Predicting histological grade in symptomatic meningioma by an objective estimation of the tumoral surface irregularity

IntroductionPredicting the histopathologic grade of meningioma is relevant because local recurrence is significantly greater in WHO grade II–III compared to WHO grade I tumours, which would ideally benefit from a more aggressive surgical strategy. It has been suggested that higher WHO grade tumours are more irregularly-shaped. However, irregularity is a subjective and observer-dependent feature. In this study, the tumour surface irregularity of a large series of meningiomas, measured upon preoperative MRI, is quantified and correlated with the WHO grade. MethodsUnicentric retrospective observational study of a cohort of symptomatic meningiomas surgically removed in the time period between January 2015 and December 2022. Using specific segmentation software, the Surface Factor (SF) was calculated for each meningioma. SF is an objective parameter that compares the surface of a sphere (minimum surface area for a given volume) with the same volume of the tumour against the actual surface of the tumour. This ratio varies from 0 to 1, being 1 the maximum sphericity. Since irregularly-shaped meningiomas present proportionally greater surface area, the SF tends to decrease as irregularity increases. SF was correlated with WHO grade and its predictive power was estimated with ROC curve analysis. ResultsA total of 176 patients (64.7% females) were included in the study; 120 WHO grade I (71.9%), 43 WHO grade II (25.7%) and 4 WHO grade III (2.4%). A statistically significant difference was found between the mean SF of WHO grade I and WHO grade II–III tumours (0.8651 ± 0.049 versus 0.7081 ± 0.105, p < 0.0001). Globally, the SF correctly classified more than 90% of cases (area under ROC curve 0.940) with 93.3% sensibility and 80.9% specificity. A cutoff value of 0.79 yielded the maximum precision, with positive and negative predictive powers of 82.6% and 92.6%, respectively. Multivariate analysis yielded SF as an independent prognostic factor of WHO grade. ConclusionThe Surface Factor is an objective and quantitative parameter that helps to identify aggressive meningiomas preoperatively. A cutoff value of 0.79 allowed differentiation between WHO grade I and WHO grade II–III with high precision.

Predicción del grado histológico en meningiomas sintomáticos mediante una estimación objetiva de la irregularidad de su superficie

IntroductionPredicting the histopathologic grade of meningioma is relevant because local recurrence is significantly greater in WHO grade II–III compared to WHO grade I tumors, which would ideally benefit from a more aggressive surgical strategy. It has been suggested that higher WHO grade tumors are more irregularly-shaped. However, irregularity is a subjective and observer-dependent feature. In this study, the tumor surface irregularity of a large series of meningiomas, measured upon preoperative MRI, is quantified and correlated with the WHO grade. MethodsUnicentric retrospective observational study of a cohort of symptomatic meningiomas surgically removed in the time period between January 2015 and December 2022. Using specific segmentation software, the surface factor (SF) was calculated for each meningioma. SF is an objective parameter that compares the surface of a sphere (minimum surface area for a given volume) with the same volume of the tumor against the actual surface of the tumor. This ratio varies from 0 to 1, being 1 the maximum sphericity. Since irregularly-shaped meningiomas present proportionally greater surface area, the SF tends to decrease as irregularity increases. SF was correlated with WHO grade and its predictive power was estimated with ROC curve analysis. ResultsA total of 176 patients (64.7% females) were included in the study; 120 WHO grade I (71.9%), 43 WHO grade II (25.7%) and 4 WHO grade III (2.4%). A statistically significant difference was found between the mean SF of WHO grade I and WHO grade II–III tumors (0.8651±0.049 versus 0.7081±0.105, p<0.0001). Globally, the SF correctly classified more than 90% of cases (area under ROC curve 0.940) with 93.3% sensibility and 80.9% specificity. A cutoff value of 0.79 yielded the maximum precision, with positive and negative predictive powers of 82.6% and 92.6%, respectively. Multivariate analysis yielded SF as an independent prognostic factor of WHO grade. ConclusionThe surface factor is an objective and quantitative parameter that helps to identify aggressive meningiomas preoperatively. A cutoff value of 0.79 allowed differentiation between WHO grade I and WHO grade II–III with high precision.

The meningioma surface factor: a novel approach to quantify shape irregularity on preoperative imaging and its correlation with WHO grade.

Atypical and anaplastic meningiomas account for 20% of all meningiomas. An irregular tumor shape on preoperative MRI has been associated with WHO grade II-III histology. However, this subjective allocation does not allow quantification or comparison. An objective parameter of irregularity could substantially influence resection strategy toward a more aggressive approach. Therefore, the aim of this study was to objectively quantify the level of irregularity on preoperative MRI and predict histology based on WHO grade using this novel approach. A retrospective study on meningiomas resected between January 2010 and December 2018 was conducted at two neurosurgical centers. This novel approach relies on the theory that a regularly shaped tumor has a smaller surface area than an irregularly shaped tumor with the same volume. A factor was generated using the surface area of a corresponding sphere as a reference, because for a given volume a sphere represents the shape with the smallest surface area possible. Consequently, the surface factor (SF) was calculated by dividing the surface area of a sphere with the same volume as the tumor with the surface area of the tumor. The resulting value of the SF ranges from > 0 to 1. Finally, the SF of each meningioma was then correlated with the corresponding histopathological grading. A total of 126 patients were included in this study; 60.3% had a WHO grade I, 34.9% a WHO grade II, and 4.8% a WHO grade III meningioma. Calculation of the SF demonstrated a significant difference in SFs between WHO grade I (SF 0.851) and WHO grade II-III meningiomas (SF 0.788) (p < 0.001). Multivariate analysis identified SF as an independent prognostic factor for WHO grade (OR 0.000009, 95% CI 0.000-0.159; p = 0.020). The SF is a proposed mathematical model for a quantitative and objective measurement of meningioma shape, instead of the present subjective assessment. This study revealed significant differences between the SFs of WHO grade I and WHO grade II-III meningiomas and demonstrated that SF is an independent prognostic factor for WHO grade.

Characterization of the Microstructure and Rheological Behavior of Al-4wt%Si-2.5wt%Cu Alloy Produced by Direct Chill Casting and Electromagnetic Stirring

This work involved an evaluation of a Al-4wt%Si-2.5wtCu alloy to be used as raw materials in the thixoforming process. The alloy was produced by direct casting under electromagnetic stirring to obtain ingots of 250 mm length and 30 mm diameter. The alloy was analyzed to determine their morphology and rheological behavior in the semi-solid range. The tests included characterization of the microstructural evolution by subjecting them to re-heating treatment in two conditions of solid fractions, 45% and 60%, for 0, 30, 90 and 210 s. A compression testing device designed specifically to evaluate semi-solid materials was used to determine the rheological behavior, and the tests were performed at the same heating rate and hold times to determine the apparent viscosity. The use of electromagnetic stirring to produce the raw material was effective in producing alloy with very small grain/primary particle sizes (80 up to 120 µm). Based on the morphological evolution in the semi-solid state, the alloy showed only minor variations in grain/primary particle size and surface factor (SF) as a function of the different globularization heat treatment times, suggesting that all these alloys are suitable for production. The Al-4.0wt%Si-2.5wt%Cu alloy with 45% solid fraction presented apparent viscosity about 1.5 x106 Pa.s.

Solar gain and building envelope: the surface factor

Harnessing the appropriate radiative characteristics of buildings' external surfaces is a highly effective way to reduce internal space heating and cooling demand. Building energy-dynamic simulations are created in order to compare various external coatings with reference to a social housing case study in a typical Mediterranean climate (Naples, Italy). An innovative index, the surface factor (SF), is proposed to inform the choice of the most suitable surface coatings as a function of local climatic conditions and thereby reduce overall energy demand. For cities with high solar gain and/or low winter degrees-day (SF > 0.65), high-reflective and/or high-emissive coatings (i.e. ‘cool paints’) are suitable, while low-reflective and/or low-emissive external coatings are more suitable for cooler climates (SF < 0.4). The simultaneous interactions of wall mass, surface radiative characteristics, and indoor ventilation on the summer cooling energy demands are evaluated and substantial heating or cooling savings can be achieved, particularly for existing buildings. For regions in which outdoor night temperature is lower than the indoor value, high thermal inertia walls are viable only when coupled to night ventilation. Diurnal ventilation coupled to massive walls was found to be energy inefficient. Exploiter les caractéristiques radiatives appropriées des surfaces extérieures des bâtiments est une manière extrêmement efficace de réduire la demande de chauffage et de refroidissement des espaces intérieurs. Il est créé des simulations dynamiques des bâtiments en termes d'énergie afin de comparer les divers revêtements extérieurs en prenant pour référence une étude de cas dans le logement social sous un climat méditerranéen type (Naples, en Italie). Un indice innovant, le facteur de surface, est proposé afin d'aider à choisir les revêtements de surface les plus adaptés en fonction des conditions climatiques locales et de réduire de ce fait la demande énergétique globale. Pour des villes ayant un apport solaire élevé et/ou des degrés-jour bas en hiver (facteur de surface > 0,65), des revêtements hautement réfléchissants et/ou à fort pouvoir émissif (c'est-à-dire des « peintures froides ») sont adaptés, tandis que des revêtements extérieurs faiblement réfléchissants et/ou à faible pouvoir émissif sont plus adaptés sous des climats plus froids (facteur de surface < 0,4). Les interactions simultanées de la masse des murs, des caractéristiques radiatives des surfaces et de la ventilation intérieure sur les demandes estivales en énergie de refroidissement sont évaluées et d'importantes économies de chauffage ou de refroidissement peuvent être réalisées, s'agissant en particulier de bâtiments existants. En ce qui concerne les régions dans lesquelles la température extérieure nocturne est inférieure à la valeur intérieure, des murs à haute inertie thermique ne sont viables que s'ils sont associés à une ventilation nocturne. Il a été constaté qu'une ventilation diurne associée à des murs massifs est énergétiquement inefficace. Mots clés: enveloppe des bâtiments physique des bâtiments surfaces extérieures revêtements de surface confort thermique inertie thermique

Permeability factor and surface esterase

Both vascular permeability factor and surface factor (SF), which have been implicated in the activation of the kinin-releasing system in plasma, are activated when plasma is exposed to glass (1, 2). SF is adsorbed by the glass and, as a consequence, permeability-increasing activity is generated in solution (3).

The Plasmatic Atmosphere of Blood Platelets. Evidence that only Fibrinogen, AcG, and Activated Hageman Factor are Present on the Surface of Platelets.

SummaryWashed platelet suspensions contain active SF (surface factor or activation product), when prepared from normal (N) subjects or from patients deficient in factors Vili, IX or X, but not from a Hageman-deficient. Factor V-deficient plasmas were normalized by platelets from N, XII- and other subjects. Allowing for (a) the platelet prothromboplastic phospholipids, and (b) the above SF and AcG (V) effects, there was no evidence of any significant factors Vili, IX or X in the platelet plasmatic atmosphere. Since XII-platelets showed no true correction of plasmas deficient in Vili, IX or X, the minor “improvement” of test results in these (and N) plasmas on adding N, Vili-, IX- or X-platelets can be explained as a nonspecific surface factor effect. XII-platelets when incubated with normal plasma were normalized by adsorbing Hageman factor (XII) on their surface.

Surface Factor Mechanisms in Relation to Blood Platelets: Evidence that Activated Hageman Factor is Present on the Surface of Platelets*

SummaryBlood platelet suspensions from normal (N) or hemophilia A (VIII-) subjects contain active SF (surface factor or activation product) in their plasmatic atmosphere. Since factor XII is an essential precursor, SF is not formed on platelets from a Hageman-deficient. Experimental evidence establishing these facts was obtained by means of clotting tests (PCa and PTT) and the thrombelastograph (TEG). The SF activity of normal platelets, like a plasma SF preparation, corrects the deficiencies in XII- plasmas, best tested in silicone or the stainless steel cuvette of the TEG. An anti-SF preparation inhibited the platelet SF activity. Allowing for the SF effect, there was no evidence for any significant factor VIII (AHF) in the platelet plasmatic atmospheres.How surface factor (SF) activation from precursors (XII, XI) in the plasma and plasmatic atmosphere of altering platelets may combine in a mutually reinforcing reaction to trigger intrinsic blood clotting is discussed. When stress, vascular injury, stasis, and other factors enter the picture, the stage may be set for the occurrence of thrombosis in vivo.

Rôles of Surface Factor and a Plasma Inhibitory Activity (Anti-SF) During Experimental Thrombosis in Rabbits

SummaryIntravenous injection of active surface factor (SF) preparations, in rabbits, induces a thrombotic tendency, which correlates with a hypercoagulability of the blood revealed with the thrombelastograph. These effects are largely dissipated within 10 minutes post-injection. Portal vein injections, or confirmed occlusion of the liver circulation, fail to show that the SF inactivation has any direct connection with the liver. Rabbit plasma normally contains a high titer of inhibitor (anti-SF), which shows no significant increase after the SF injections. The inhibition is chiefly “progressive” in rabbit plasma. Plasma anti-SF could largely explain the nonpersistence of hypercoagulability and thrombo-genic activity in the 10 min post-injection tests. These mechanisms may be an important element in the body defenses against any thrombotic tendency associated with increased SF activity.