Cross-sectional Reconstruction Research Articles

Evaluation of gingival thickness obtained from intraoral scanning registration with cone beam computed tomography at different acquisition modes

To investigate the reliability of gingival thickness measurements obtained from the registration of intraoral scans with cone beam computed tomography (CBCT) examinations at different acquisition modes. CBCT examinations of 9 porcine hemimandibles were acquired using the OP300 Maxio unit operating at the highest-dose protocol with the smallest voxel size as the reference standard for visualizing the gingival surface. Subsequently, the hemimandibles were surrounded by water to simulate soft tissue attenuation of radiation, and additional CBCT examinations were acquired in 4 modes: Endo, High-resolution, Standard-resolution, and Low-dose. These CBCT datasets were registered with corresponding intraoral scans obtained with the Carestream Dental 3600 intraoral scanning system using the Blue Sky Plan 4 software. Four oral radiologists measured the buccal gingival thickness on cross-sectional reconstructions at 4 measurement sites and 2 distances from the gingival margin in the CBCT reference standard examinations and examinations obtained with water and intraoral scan registration. Multifactorial analysis of variance was used to assess the influence of acquisition mode, measurement site, and distance from the gingival margin on measurements (α = 5%; statistical power = 90%). Buccal gingival thickness measurements obtained via CBCT after registration with intraoral scanning were not significantly influenced by acquisition mode (P = .153) or measurement site (P = .089). Gingival thickness measurements derived from the registration of intraoral scans with CBCT examinations at different acquisition modes appear to be reliable.

Establishment of a Uniaxial Tensile Fracture Inversion Model Based on Fracture Surface Reconstruction (FRASTA)

In order to infer the load on the component after the experimental uniaxial tensile fracture inversion model based on cross-sectional reconstruction, (FRASTA) was proposed to infer the load on the tested components. This model can combine the fracture surface characteristics of experimental specimens to reconstruct the fracture surface morphology and invert the fracture process of uniaxial tensile specimens. Based on the assumption of rectangular rod fracture, a quantitative inversion model for a unidirectional stress load based on dissipative plasticity characteristics was established, and the inversion results based on cross-sectional reconstruction were compared with the experimental measurement results. The results indicate that when only considering the unidirectional stress state, the two have a high degree of consistency, with a maximum measurement error of 5.3%, fully verifying the accuracy of the fracture surface reconstruction and inversion model.

Exploring for structurally concealed Carlin-type mineralization: A case study from the northern Shoshone Range, Nevada, USA

This study integrates results from previous studies with new reconnaissance-scale mapping of rock types, structures, and hydrothermal alteration at Goat Ridge and Tenabo to provide a district-scale cross section and palinspastic restoration of an area in Nevada with high potential for Carlin-type mineralization in the footwall of a dismembered thrust fault. Reinterpretation of legacy drill data in light of recent advances in the understanding of Cenozoic normal faulting in the area with the expected stratigraphy of the Roberts Mountains autochthon allows for deciphering whether previous drill holes piercements of faults are the Roberts Mountains thrust or are tilted normal faults that down-dropped the deep-water siliciclastic rocks of Roberts Mountains allochthon onto the coeval carbonate rocks of the Roberts Mountains autochthon. A cross-sectional reconstruction shows that ∼11.1 km (120 %) of extension was accomplished along one set of faults that initiated at 60-70°and tilted 40°E. Previously underappreciated Mesozoic folds are present, which likely formed with horizontal fold hinges. Because of Cenozoic normal faulting and associated tilting, the hinge lines currently plunge at moderate angles and are offset as they step across each crosscutting fault. The anticlinal fold hinges produced the modern exposures of lower plate rocks in the range. The Eocene paleogeologic map that results from a plan-view structural restoration shows that the hinge lines of the original folds trended northwest-southeast in the southern half of the range but turned northward toward the northern end of the range.Mineralization in the range includes silver-dominated polymetallic veins/lodes, weak porphyry-type, Carlin-type, and siliciclastic-hosted gold deposits of uncertain origin. Porphyry-style and silver-dominated polymetallic vein mineralization is associated with ∼39–40 Ma granodiorites, with the silver-dominated polymetallic veins interpreted as the distal veins around weakly mineralized and/or deeply buried porphyry system(s), probably of the quartz monzonitic-granitic porphyry Mo-Cu subclass of porphyry molybdenum deposits. Crosscutting relationships demonstrate that at least one of “upper plate” gold deposits is Eocene, but a Miocene age cannot be ruled out for the other gold deposits.

Influence of CBCT-derived panoramic curve variability in the measurements for dental implant planning.

To investigate whether the curve markings performed prior to panoramic and cross-sectional reconstructions can influence the planning of oral implants. Twenty oral radiologists landmarked the reference panoramic curves in 25 CBCT scans of the mandible. Bone height was measured on the resulting cross-sectional slices in the edentulous region of the lower first molar. The following data were recorded: (1) number of landmarks used to build each reference curve; (2) shape of the reference curve (inverted "U", inverted "V" or "horseshoe"); and (3) measurement in the first molar region. The data were assessed for variability based on the number of landmarks, the shape of the reference curve, and the measurements obtained. The number of landmarks used to guide the panoramic reconstruction varied among radiologists (p < 0.05), but most of them draw curves in inverted "U" shape (68-100%). The reproducibility of the measurements taken in the edentulous mandibular first molar region was excellent (84.7%). The number of landmarks and the shape of the curve did not have a significant influence on the reproducibility of the measurements (p > 0.05). Variations of the operator-dependent steps during the panoramic reconstructions occur but do not play a significant part changing the measurements taken for oral implant planning.

Direct solar FTIR measurements of CO2 and HCl in the plume of Popocatépetl Volcano, Mexico

Volcanic CO2 emissions inventories have great importance in the understanding of the geological carbon cycle. Volcanoes provide the primary pathway for solid-earth volatiles to reach the Earth’s atmosphere and have the potential to significantly contribute to the carbon-climate feedback. Volcanic carbon emissions (both passive and eruptive degassing) included in inventories, largely stem from patchy surface measurements that suffer from difficulties in removing the atmospheric background. With a 27-year-long ongoing open-vent eruption, Popocatépetl ranks as one of the highest permanent volcanic CO2 emitters worldwide and provides an excellent natural laboratory to design and experiment with new remote sensing methods for volcanic gas emission measurements. Since October 2012, infrared spectra at different spectral regions have been recorded with a solar occultation FTIR spectrometer. The near-infrared spectra allow for high precision measurements of CO2 and HCl columns. Under favorable conditions, the continuous observations during sunrise allow the reconstruction of a plume cross-section of HCl and the estimation of the emission flux using wind data. Despite that the detection of CO2 is more challenging, on April 26th, 2015 we captured a volcanic plume under favourable wind conditions which allowed us to reconstruct from this particular event a CO2 emission rate of 116.10 ± 17.2 kg/s. The volcanic HCl emission on this event was the highest detected during the 2012-2016 period. An annual average CO2 emission estimate of (41.2 ± 16.7) kg/s ((1.30 ± 0.53) Tg/yr) could be determined from a statistical treatment of the detected CO2 and HCl columns in the IR spectra, and their corresponding molecular ratios, during this period. A total of 25 events were used to derive a mean CO2/HCl molecule ratio of 11.4 ± 4.4 and an average HCl emission rate of (3.0 ± 0.3) kg/s could be determined. The CO2 emissions of Popocatépetl were found to be around 0.32% of the total anthropogenic CO2 emissions reported in the country and 3.6% of those corresponding to the Mexico City Metropolitan Area (MCMA). CO2 emissions from the Popocatépetl volcano can be considered to play a negligible role in the global CO2 budget, but should be taken into account.

Challenges of transsphenoidal pituitary surgery in severe brachycephalic dogs.

Transsphenoidal hypophysectomy is the standard surgical technique for the excision of pituitary neoplasms. Anatomy may be more obscured in brachycephalic skull types due to the crowding of soft tissue and osseous structures. We describe the unique challenges to approach the sphenoid bone and localize the correct burr hole site in severe brachycephalic dogs. A single institution retrospective case series of brachycephalic dogs with pituitary-dependent hypercortisolism (PDH). Preoperative computed tomography enabled 3D-, and cross-sectional reconstruction to plan and dry-practice the position of the ideal burr hole in relation to the sella turcica, pterygoid hamular processes, and hard palate. Rostral burring of the caudal hard palate obscuring the direct sphenoid approach necessitated adaptations to the original transsphenoidal hypophysectomy procedure. Postoperative outcomes and complications with respect to those seen in mesocephalic dogs are described. Ten brachycephalic dogs including French Bulldogs (n = 9) and a single Dogue de Bordeaux were included. All dogs were diagnosed with PDH and had preoperative advanced imaging performed on the skull. All but one dog had an enlarged pituitary gland, with a median pituitary/brain value of 0.5 (range 0.21-0.9). A total of 11 transsphenoidal hypophysectomy procedures were performed in these 10 dogs. Rostral extension of the soft palate incision into the hard palate was performed to access the burr hole site on the sphenoid bone. Major complications included aspiration pneumonia (n = 1), severe gastroesophageal reflux (n = 1), and central nervous signs (=1). All dogs survived until discharge, with a median time to follow-up of 618 days (range 79-1,669 days). Seven dogs experienced long-term remission of PDH. Brachycephalic dogs undergoing transsphenoid al hypophysectomy benefit from meticulous presurgical planning and extension of the approach into the caudal hard palate. Advanced surgical skills can render a good outcome in a technically challenging environment.

A comparison of computed tomography imaging with histopathology in the sensitivity and correlation of evaluating coronary arterial calcification.

The sensitivity and correlation of coronary computed tomography angiography (CTA) as compared with histopathology are unknown in evaluating coronary arterial calcification. In this study, we retrospectively evaluated qualitatively and quantitatively the sensitivity and correlation of coronary CTA compared with histopathology in assessing coronary arterial calcification. This study was conducted on 12 randomly selected cadavers aged over 40 years at the time of death, and 53 segments of coronary arteries from these 12 cadavers were obtained from the Human Anatomy Laboratory of Tianjin Medical University. The artery segments were scanned using contrasted-enhanced dual-source computed tomography (DSCT) with an axial slice thickness of 0.6 mm. Coronary artery calcification in a coronary segment was defined as the presence of 1 or more voxels with a CT density >130 Hounsfield units. According to the arc of calcification in the cross section of the coronary artery wall, calcified plaques were divided into three categories: mild, moderate, and severe calcification. The coronary artery stenosis caused by calcified plaque was observed and calculated with multiplanar reconstruction (MPR), maximum density projection, volume rendering (VR), and cross-sectional reconstruction. After CT enhancement scanning, the coronary artery specimens were cut into 4-mm long segments and embedded in paraffin for pathological staining. Pathological classification and coronary artery stenosis measured with pathological analysis were used as comparison criteria. Histopathology detected 69 Vb-type plaques, while DSCT detected 57 calcified plaques. The sensitivity of CT for detecting mild, moderate, and severe calcified plaques were 88.3% [95% confidence interval (CI): 74.1-95.6%], 100% (95% CI: 69.8-100%), and 100% (95% CI: 73.2-100%), respectively. DSCT had a significant (P<0.001) correlation with histopathology in quantifying coronary artery stenosis caused by mild, moderate, and severe calcified plaques (R2=0.9278, R2=0.9158, R2=0.7923, respectively). Compared with histopathology, DSCT overestimated coronary artery stenosis caused by mild, moderate, and severe calcified plaques (3.2%±2.0%, 4.9%±4.7%, and 14.7%±8.2%, respectively; P<0.05). DSCT contrast enhancement scanning can detect and characterize coronary artery calcification with a good correlation with histopathologic quantification of coronary artery stenosis caused by different types of calcified plaques, even though coronary CTA may overestimate the stenosis.

Evaluation of the morphology of accessory canals of the canalis sinuosus via cone-beam computed tomography

Purpose: This study aims to assess the presence of accessory canal (AC) associated with canalis sinuous (CS), describing their frequency, lateralization, location, direction, and measurements in cone beam computed tomography (CBCT).Methods: Axial, coronal, sagittal, and cross-sectional reconstructions were analyzed in 248 CBCT images and the presence of CS, the presence of AC associated with CS, the lateralization, localization, and direction course of AC associated with CS was evaluated. CS diameter, AC diameter, the distance between the nasal cavity floor and CS (M1), CS and the buccal cortical bone (M2), and CS and the alveolar ridge (M3) were measured.Results: CS was detected in all CBCT scans as bilaterally. The prevalence of AC associated with CS was 35.5%. There was a significant difference between dental status anthe d presence of AC associated with CS. There was a significant difference between gender, dental status, and lateralization of AC associated with CS. While M1 was greater in male patients than females, M3 was greater in female patients. M2 and M3 were greater in younger patients.Conclusion: Clinicians performing surgical procedures should keep in mind that anatomical variations of the vascular nerve bundle may be seen. M1, M2, and M3 measurements can be affected by gender, age, and dental status.

Cone-beam computed tomographic reconstructions in the evaluation of maxillary impacted canines.

Prior to cone-beam computed tomography (CBCT), orthodontic competence included radiological interpretation. Nevertheless, maxillary impacted canines (MICs), because of their position and adjacent complex anatomy, have been challenging to interpret, particularly with regard to root resorption. Although CBCT cross-sectional reconstructions of MICs yielded clearer insights into its diagnosis and treatment planning, the value of simultaneously using 2 different cross-sectional or multiplanar reconstructions of the CBCT datasets - orthogonal and curved/panoramic multiplanar reconstructions - has hitherto not been considered. Both orthogonal and curved/panoramic multiplanar reconstruction series of 5 screenshots were each reconstructed from the 5 cm × 5 cm CBCT datasets of 15 separate MICs. Fifteen credentialled and experienced orthodontist volunteers reviewed 2 separate PowerPoints of 15 randomized series each, 1 week apart. Their review considered 6 factors that could affect treatment: the position and level of the MIC, the presence or absence of root resorption, ankylosis, cysts, and dilaceration. All 15 orthodontists were statistically similar regarding overall years of experience and of CBCT use. Although either reconstruction alone allowed the orthodontists to determine whether ankylosis and, to a lesser extent, most of the other features were present or absent in the MIC, reviewing both reconstructions together was necessary to determine whether root resorption was present or absent in the adjacent tooth. Reviewing both orthogonal and curved/panoramic multiplanar reconstructions was necessary to evaluate the presence or absence of root resorption in the teeth adjacent to MICs and that of many other features.

Development and verification of a new nuclear data processing code AXSP

The advanced reactor design needs an accurate cross-section generation code. In this study, a new nuclear data processing code AXSP is developed, and the method and performance of which are described. Compared with the NJOY program, the precision of the unresolved resonance processing module UnresXS has been significantly improved due to the adoption of a more accurate solution method and the consideration of in-sequence overlap integrals. The time consumption of PUnresXS has been decreased significantly due to an optimized sorting algorithm. At the same time, other modules of AXSP are relatively comprehensive. The function of resolved resonance cross-section reconstruction and linearization is the ReconXS module. The Doppler broadening module is BroadXS by using Gauss–Hermite quadrature and Gauss–Legendre quadrature from 0 K temperature pointwise cross section to any temperature which is defined by the user. The shielding factor in the unresolved resonance energy region is calculated by the UnresXS or the PUnresXS module, which are developed based on the Bondarenko method and the probability table method, respectively. The ACE formatted cross sections for the Monte Carlo code is processed by the ACEXS module, and the multigroup cross sections are generated by the GroupXS module. The cross sections processed by different modules were verified by the NJOY2016 code, and the multigroup cross sections were also verified by using the critical benchmarks. The multiplication factor difference between AXSP and NJOY2016 is less than 20 pcm. In addition to this, the ZPR6/7 fast reactor is used for ACE format library verification. The results show that the criticality calculated by AXSP has a good agreement with that of NJOY2016.

A guide for standardized interpretation of lumbar multifidus ultrasonography; an observational study

BackgroundInconsistent descriptions of Lumbar multifidus (LM) morphology were previously identified, especially in research applying ultrasonography (US), hampering its clinical applicability with regard to diagnosis and therapy. The aim of this study is to determine the LM-sonoanatomy by comparing high-resolution reconstructions from a 3-D digital spine compared to standard LM-ultrasonography.MethodsAn observational study was carried out. From three deeply frozen human tissue blocks of the lumbosacral spine, a large series of consecutive photographs at 78 μm interval were acquired and reformatted into 3-D blocks. This enabled the reconstruction of (semi-)oblique cross-sections that could match US-images obtained from a healthy volunteer. Transverse and oblique short-axis views were compared from the most caudal insertion of LM to L1.ResultsBased on the anatomical reconstructions, we could distinguish the LM from the adjacent erector spinae (ES) in the standard US imaging of the lower spine. At the lumbosacral junction, LM is the only dorsal muscle facing the surface. From L5 upwards, the ES progresses from lateral to medial. A clear distinction between deep and superficial LM could not be discerned. We were only able to identify five separate bands between every lumbar spinous processes and the dorsal part of the sacrum in the caudal anatomical cross-sections, but not in the standard US images.ConclusionThe detailed cross-sectional LM-sonoanatomy and reconstructions facilitate the interpretations of standard LM US-imaging, the position of the separate LM-bands, the details of deep interspinal muscles, and demarcation of the LM versus the ES. Guidelines for electrode positioning in EMG studies should be refined to establish reliable and verifiable findings. For clinical practice, this study can serve as a guide for a better characterisation of LM compared to ES and for a more reliable placement of US-probe in biofeedback.

Endovascular Management of Intracranial Pial Arteriovenous Fistula with Giant Venous Varix: Case Report and Review of Literature.

Abstract: Background: Intracranial pial arteriovenous fistulas (AVFs) are rare intracranial vascular malformation and their treatment is challenging because of high-flow pial supply of the lesion. We report a case of intracranial pial AVF with associated giant venous varices managed successfully by embolization. Case Description: A 25-year-old male presented with sudden onset headache and altered sensorium. Computed tomographic scan was suggestive of frontal lobar hematoma that had dissected into the third ventricle with associated intraventricular hemorrhage. Magnetic resonance imaging revealed presence of large vascular channels with the presence of multiple flow voids in bilateral frontal location. Digital subtraction angiography revealed pial fistula with arterial supply from hypertrophied left anterior cerebral artery. Treatment was done using combined coil and onyx embolization after careful analysis of angioarchitecture of the lesion using three-dimensional rotational angiogram cross-sectional reconstructions. Postprocedure angiogram revealed closure of fistula and giant varices. Conclusion: Pial AVFs with giant venous varix in adults are rare vascular malformation and understanding the angioarchitecture with exact identification of fistulous point is important to plan for surgical/endovascular management strategies. Combined strategy of embolization using coils and onyx is a safe option in such cases with giant varices.

Three-dimensional measurement of yarn evenness using mirrored images

A three-dimensional measurement method for yarn evenness is proposed in this paper. A sample is placed in the image acquisition system and the virtual images and real image are collected in one image by a camera. The geometric relationship of the xoy and the xoz plane of the system is obtained. The multi-view image of sample is calibrated according to the geometric relationship. The intersection method and the tangent method are proposed to determine the key-points of yarn cross-section reconstruction in the xoy plane. 3D model of yarn core is obtained by combining all the yarn cross-sections in the xoz plane. The correlation coefficient between mean area of yarn cross-sections in the proposed method and diameter measured by the Uster TESTER 5 is up to 0.759. The correlation coefficient of CV values between the proposed method and the Uster TESTER 5 is up to 0.944.

Late Paleozoic Gondwanide deformation in the Central Andes: Insights from RSCM thermometry and thermal modeling, southern Bolivia

A widespread unconformity between Ordovician metasedimentary rocks and nonmetamorphosed Mesozoic sedimentary rocks across the Eastern Cordillera of Bolivia provides evidence for significant pre-Late Cretaceous deformation and erosion. In this paper, we refine the middle to late Paleozoic tectonic history of the central Andean segment of Gondwana's western margin. We combine Raman spectroscopy of carbonaceous material (RSCM) thermometry with semi-quantitative deformation temperature estimates from quartz recrystallization microstructures and published illite crystallinity values from Cambrian-Devonian sedimentary rocks that span the Eastern Cordillera of southern Bolivia at ~21°S. Estimates of peak temperature and deformation temperature range primarily between ~220 and ~ 400 °C and show a general increase with depth that defines a metamorphic field gradient between ~37 and ~ 47 °C/km. Temperatures obtained from Ordovician rocks directly below the unconformity require erosion of a > ~5 km overburden prior to the Late Cretaceous, which was likely accomplished by a combination of distributed cleavage development and Paleozoic folding and thrust faulting revealed from cross-section reconstructions. The peak temperature data are incorporated into thermal models along with published illite KAr, zircon (UTh)/He, and zircon fission-track cooling ages that refine the timing of Paleozoic orogenesis in the central Andes. We interpret shortening-related flexural subsidence driven by cratonward growth of a pre-Andean orogenic wedge along the western margin of Gondwana, with peak temperature conditions attained during eastward advance of a foreland basin between ~420 and ~ 318 Ma during the Devonian-Carboniferous Gondwanide Orogeny. Erosional exhumation between ~352 and ~ 294 Ma was the result of continued growth and eastward expansion of the associated Transpampean tectonic highland across the Eastern Cordillera. The growth of this pre-Andean contractional orogen coincided with global plate reorganization and the reestablishment of subduction and arc magmatism along the western margin of Gondwana, as indicated by a significant influx of Carboniferous arc-related detritus into the foreland basin system.

Intraoperative cone beam computed tomography for detecting residual stones in percutaneous nephrolithotomy: a feasibility study

Cone beam computed tomography (CBCT) provides multiplanar cross-sectional imaging and three-dimensional reconstructions and can be used intraoperatively in a hybrid operating room. In this study, we investigated the feasibility of using a CBCT-scanner for detecting residual stones during percutaneous nephrolithotomy (PCNL). Intraoperative CBCT-scans were made during PCNL procedures from November 2018 until March 2019 in a university hospital. At the point where the urologist would have otherwise ended the procedure, a CBCT-scan was made to image any residual fragments that could not be detected by either nephroscopy or conventional C-arm fluoroscopy. Residual fragments that were visualized on the CBCT-scan were attempted to be extracted additionally. To evaluate the effect of this additional extraction, each CBCT-scan was compared with a regular follow-up CT-scan that was made 4 weeks postoperatively. A total of 19 procedures were analyzed in this study. The mean duration of performing the CBCT-scan, including preparation and interpretation, was 8 min. Additional stone extraction, if applicable, had a mean duration of 11 min. The mean effective dose per CBCT-scan was 7.25 mSv. Additional extraction of residual fragments as imaged on the CBCT-scan occurred in nine procedures (47%). Of the follow-up CT-scans, 63% showed a stone-free status as compared to 47% of the intraoperative CBCT-scans. We conclude that the use of CBCT for the detection of residual stones in PCNL is meaningful, safe, and feasible.

A study of fracture toughness of granite under impact load using three-dimensional reconstruction and high-speed photography techniques

To study the dynamic fracture toughness of granite under impact load, the dynamic stress intensity factor of I-type cracks was calculated based on a bending test for straight cut grooves in semi-circular discs. With the help of high-speed photography, the process of dynamic fracture failure was studied, and it was found that the cracks propagated rapidly in the dynamic fracture toughness test; initiation of cracks occurred at the crystal boundaries; then, the cracks propagated rapidly, accompanied by intracrystalline and cleavage cracks, followed by convergence, penetration, and ultimately failure. By performing surface three-dimensional reconstruction of sample cross-sections using the LM740 laser confocal microscope, the surface coarseness and surface three-dimensional reconstruction of the granite were determined, and relationships between the surface coarseness and crack propagation velocity and between the dynamic propagation toughness and crack propagation velocity were determined. The research results show that the average value of dynamic fracture toughness of the granite was 4.12 MPa m1/2, the crack propagation velocity during dynamic loading was 400–600 m/s, the maximum dynamic propagation toughness was 14.88 MPa m1/2, and the crack surface coarseness and crack dynamic propagation toughness exhibited exponential increasing trends with the increase in crack propagation velocity.

Influence of Bone Anatomy on Implant Placement Procedures in Edentulous Arches of Elderly Individuals: A Cross-Sectional Study on Computed Tomography Images.

To describe the prevalence of alveolar bone atrophy in edentulous arches of elderly individuals in relation to insertion of dental implants and the eventual need for bone grafting procedures. Computed tomography scan files of 228 edentulous arches of elderly patients (ages 65 to 100 years) were evaluated in relation to implant placement. Six measurements per arch were taken on cross-sectional reconstructions. Bone atrophy categories were described, in relation to implant placement, for the anterior and posterior sections of the arches. Six bone sections per arch were evaluated and allocated to the predetermined categories. Prevalence of each type of atrophy was calculated. In the maxilla, only 5.0% of the patients showed a bone anatomy capable of receiving implants without any augmentation both in the posterior and anterior regions; 64.4% showed the need for major reconstruction in both areas. In the mandible, 17.3% of the patients did not require any augmentation in both regions; 9.4% were in need of major reconstruction in both areas. The anterior part of the arches could eventually be treated without any bone augmentation in 10.9% of the maxillae and 72.4% of the mandibles, while minor augmentation was needed in 16.8% of maxillae and 15.8% of mandibles. Most edentulous elderly patients show some degree of alveolar bone atrophy. It is often feasible to insert implants in the anterior mandible to support a restoration. In most maxillary cases, alveolar atrophy calls for augmentation procedures in both the anterior and posterior areas. In elderly individuals, the anterior maxilla often shows bone deficiency interfering with simple implant placement procedures, thus also limiting the use of tilted implants.

Simultaneous reconstruction of emission and attenuation in passive gamma emission tomography of spent nuclear fuel

In the context of international nuclear safeguards, the International Atomic Energy Agency (IAEA) has recently approved passive gamma emission tomography (PGET) as a method for inspecting spent nuclear fuel assemblies (SFAs). The PGET instrument is essentially a single photon emission computed tomography (SPECT) system that allows the reconstruction of axial cross-sections of the emission map of an SFA. The fuel material heavily self-attenuates its gamma-ray emissions, so that correctly accounting for the attenuation is a critical factor in producing accurate images. Due to the nature of the inspections, it is desirable to use as little a priori information as possible about the fuel, including the attenuation map, in the reconstruction process. Current reconstruction methods either do not correct for attenuation, assume a uniform attenuation throughout the fuel assembly, or assume an attenuation map based on an initial filtered back-projection reconstruction. We propose a method to simultaneously reconstruct the emission and attenuation maps by formulating the reconstruction as a constrained minimization problem with a least squares data fidelity term and regularization terms. Using simulated data, we show that our approach produces clear reconstructions which allow for a highly reliable classification of spent, missing, and fresh fuel rods.

Erbium YAG laser and diode laser applications for the second phase of implant surgery: a comparison of clinical outcomes

This study assessed the clinic outcomes of erbium: yttrium/aluminum/garnet (Er:YAG) laser and diode laser use in second phase of implant surgery. Fifty implants scheduled for stage II implant surgery were randomly assigned to 4 groups. In the first group (G1), Lite-touch Er:YAG laser was selected, and a vacuum-formed template was used for each site to indicate surgical entrance. For the second group (G2), Lite-touch Er:YAG laser was used and the surgery was performed in a free-hand way. The third group (G3) adopted free-hand surgery while diode laser was used. In the last group (G4), LightWalker Er:YAG laser was applied by free hand. The surgeon was allowed to look at cross-sectional images and 3D reconstruction in the computer to obtain implant position in G2, G3, and G4. The time of operation, healing time, and accuracy of operation were assessed. G1 and G4 took the shortest time in surgery than that of the other two groups (P 0.05). The healing time of Lite-touch Er:YAG laser with or without surgical guide was the shortest when compared with the other two groups (P < 0.05). G3 had the longest healing time among the 4 treatment modalities (P < 0.05). When applied in the implant uncover surgery, Er:YAG laser presents shorter healing time than diode laser. Contact laser operation provides more accuracy than noncontact operation.

Leadership from behind

Neurodevelopment![Figure][1] Cross-sectional reconstruction of a C. elegans embryo (teal) showing higher (red) and lower (blue, green, and purple) morphogen concentrations IMAGE: SANDEEP GOPAL/MONASH UNIVERSITY Morphogens of the Wnt family regulate development during embryogenesis in organisms ranging from hydra to humans. These peptides, secreted in globular form by the synthesizing cells, initiate signaling cascades that direct morphogenesis. Wnt protein stability in the extracellular environment depends on its multiple disulfide bonds. Torpe et al. identified the protein-folding chaperone in the small nematode Caenorhabditis elegans that is required for viability of a Wnt variant. By controlling folding of this Wnt variant, the protein disulfide isomerase (PDI) controls neuronal migration. Similarly, human cells tested with a pharmacological inhibitor of PDI confirm that Wnts can regulate human development, too. Cell Reports 10.1016/j.celrep.2019.02.072 (2019). [1]: pending:yes