Automated 2-dimensional measurement of vestibular schwannoma: validity and accuracy of an artificial intelligence algorithm

ObjectiveValidation of automated 2-dimensional (2D) diameter measurements of vestibular schwannomas on magnetic resonance imaging (MRI). Study DesignRetrospective validation study using 2 data sets containing MRIs of vestibular schwannoma patients. SettingUniversity Hospital in The Netherlands. MethodsTwo data sets were used, 1 containing 1 scan per patient (n = 134) and the other containing at least 3 consecutive MRIs of 51 patients, all with contrast-enhanced T1 or high-resolution T2 sequences. 2D measurements of the maximal extrameatal diameters in the axial plane were automatically derived from a 3D-convolutional neural network compared to manual measurements by 2 human observers. Intra- and interobserver variabilities were calculated using the intraclass correlation coefficient (ICC), agreement on tumor progression using Cohen's kappa. ResultsThe human intra- and interobserver variability showed a high correlation (ICC: 0.98-0.99) and limits of agreement of 1.7 to 2.1 mm. Comparing the automated to human measurements resulted in ICC of 0.98 (95% confidence interval [CI]: 0.974; 0.987) and 0.97 (95% CI: 0.968; 0.984), with limits of agreement of 2.2 and 2.1 mm for diameters parallel and perpendicular to the posterior side of the temporal bone, respectively. There was satisfactory agreement on tumor progression between automated measurements and human observers (Cohen's & kappa; = 0.77), better than the agreement between the human observers (Cohen's & kappa; = 0.74). ConclusionAutomated 2D diameter measurements and growth detection of vestibular schwannomas are at least as accurate as human 2D measurements. In clinical practice, measurements of the maximal extrameatal tumor (2D) diameters of vestibular schwannomas provide important complementary information to total tumor volume (3D) measurements. Combining both in an automated measurement algorithm facilitates clinical adoption.Radiolog

Morphological changes after cranial fractionated photon radiotherapy: Localized loss of white matter and grey matter volume with increasing dose

Purpose: Numerous brain MR imaging studies have been performed to understand radiation-induced cognitive decline. However, many of them focus on a single region of interest, e.g. cerebral cortex or hippocampus. In this study, we use deformation-based morphometry (DBM) and voxel-based morphometry (VBM) to measure the morphological changes in patients receiving fractionated photon RT, and relate these to the dose. Additionally, we study tissue specific volume changes in white matter (WM), grey matter (GM), cerebrospinal fluid and total intracranial volume (TIV). Methods and materials: From our database, we selected 28 patients with MRI of high quality available at baseline and 1 year after RT. Scans were rigidly registered to each other, and to the planning CT and dose file. We used DBM to study non-tissue-specific volumetric changes, and VBM to study volume loss in grey matter. Observed changes were then related to the applied radiation dose (in EQD2). Additionally, brain tissue was segmented into WM, GM and cerebrospinal fluid, and changes in these volumes and TIV were tested. Results: Performing DBM resulted in clusters of dose-dependent volume loss 1 year after RT seen throughout the brain. Both WM and GM were affected; within the latter both cerebral cortex and subcortical nuclei show volume loss. Volume loss rates ranging from 5.3 to 15.3%/30 Gy were seen in the cerebral cortical regions in which more than 40% of voxels were affected. In VBM, similar loss rates were seen in the cortex and nuclei. The total volume of WM and GM significantly decreased with rates of 5.8% and 2.1%, while TIV remained unchanged as expected. Conclusions: Radiotherapy is associated with dose-dependent intracranial morphological changes throughout the entire brain. Therefore, we will consider to revise sparing of organs at risk based on future cognitive and neurofunctional data

Numerical investigation of 3-D constraint effects on brittle fracture in SE(B) and C(T) specimens

This investigation employs 3-D nonlinear finite element analyses to conduct an extensive parametric evaluation of crack front stress triaxiality for deep notch SE(B) and C(T) specimens and shallow notch SE(B) specimens, with and without side grooves. Crack front conditions are characterized in terms of J-Q trajectories and the constraint scaling model for cleavage fracture toughness proposed previously by Dodds and Anderson. The 3-D computational results imply that a significantly less strict size/deformation limit, relative to the limits indicated by previous plane-strain computations, is needed to maintain small-scale yielding conditions at fracture by a stress- controlled, cleavage mechanism in deep notch SE(B) and C(T) specimens. Additional new results made available from the 3-D analyses also include revised {eta}-plastic factors for use in experimental studies to convert measured work quantities to thickness average and maximum (local) J-values over the crack front

Sedimentology, paleoclimatology, and diagenesis of Post-Hercynian continental deposits in the South-Central Pyrenees, Spain

The first chapter of the post-Hercynian geologic history of the South-Central Pyrenees is recorded in a sequence of fluvial and volcanic deposits which reach a total of added maximum thicknesses of more than 2300 m and date from the Westphalian D up to and including the Lower Triassic. The present study concerns the primary lithology, paleocurrents, depositional environment, paleoclimatology, and diagenesis of these deposits. Five formations are distinguished: (5) Bunter Formation (Lower Triassic) (4) Peranera Formation (Permian) (3) Malpas Formation (Stephanian) (2) Erill Castell Volcanics (Stephanian?) (1) Aguiró Formation (Westphalian D) The deposits of the Aguiró Formation are the fills of fossil valleys forming part of a pronounced paleorelief. The formation consists largely of conglomerates deposited by braided streams. One level, near Aguiró, contains coal-bearing, tuffaceous mudstone and tuff beds, the environment of deposition corresponding to that of a back-swamp. Most clastic components, many of wich are non-calcareous phyllite grains, can be recognized as stemming from the Paleozoic basement (Axial Zone of the Pyrenees, lying to the North of Aguiró). The Erill Castell Volcanics, consisting of silicified and kaolinized andesitic tuffs and one intercalated basaltic andesite sheet, were deposited on a hilly land surface, since they locally overly fossil slope breccia and contain some fluvial channel-fills. The tuffs show evidence of penecontemporaneous pedogenesis. The Malpas Formation contains coal-bearing mudstones and shales, bedded chert, limestones, and ferroan dolomite beds (backswamp and lacustrine environments), sheets of upward-fining sandstones (the fills of mainly meandering streams), and one thick level of conglomerates (braided stream environment). The distribution of these deposits on the geological map still indicates the filling-in of a fossil valley. Nearly all the clastic components in the Malpas Formation stem from the directly underlying Erill Castell Volcanics, which had already been altered by weathering. The Peranera Formation consists of caliche-bearing red beds. Depositional features point to the lowlands bordering alluvial fans. Many of the clastic components are similar to those in the Aguiró Formation, stemming from the Paleozoic basement. The Bunter Formation, which is also composed of red beds, unconformably overlies all other deposits; its lower surface records a period of pediplanation. The Bunter sandstones consist mainly of quartz; they are the most mature in the entire sequence. The Peranera depositional environment was comparable to that of the present-day steppes, the Bunter environment to that of savannahs. All fluvial deposits show paleocurrent directions indicating flow from either the West, the North, or the East. The paleoclimate was of paramount importance for the primary lithology, depositional characteristics, and diagenesis of the deposits. Humid conditions would account for the deduced continuous flow during the deposition of the Malpas Formation and flooded back-swamps of the Aguiró and Malpas formations. In these formations, diagenetic parageneses of iron sulfides, kaolinite, and siderite, and the preservation of abundant vegetational debris, point to a weakly to strongly reducing and a neutral to acid milieu. A semi-arid climate is consistent with the intermittent flow deduced from channel-fill properties in the Peranera Formation. Flow in the Bunter channels was more continuous, but the channels dried up in the dry seasons. The instability of the vegetational debris in both formations (root traces are present but there is hardly any coalified material) points to lowered water-tables and the oxidizing conditions of sub-aerial diagenesis. In spite of the similarity represented by a greyish-red stain, the Peranera and Bunter red beds differ strongly in primary lithology and diagenesis. The clastic composition of the Peranera Formation is to a great extent unstable; in the Bunter Formation it is highly stable; ferric oxides in the Peranera sandstones were largely brought in clastically; in the Bunter sandstones they are authigenic. Diagenesis in the Peranera deposits is mainly that of precipitation of and replacement by calcite (caliche); in the Bunter deposits in situ kaolinization of muscovite, possibly early diagenetic quartz (silcrete?), and authigenesis of dolomite can be observed. These differences are probably related in part to the morphologic setting (Peranera Formation: still some relief; Bunter Formation: deposits directly overlying wide pediments), but chiefly to the paleoclimate (Peranera Formation: steppe climate; Bunter Formation: savannah climate). The composition of recent fluvial sands deriving from the Paleozoic core of the Pyrenees is treated in an Appendix. These sands are to a large extent comparable to the sandstones in the Aguiró and Peranera Formations