Texture Appearance Research Articles

Reversible spin texture in ferroelectric HfO2

Spin-orbit coupling effects occurring in non-centrosymmetric materials are known to be responsible for non-trivial spin configurations and a number of emergent physical phenomena. Ferroelectric materials may be especially interesting in this regard due to reversible spontaneous polarization making possible for a non-volatile electrical control of the spin degrees of freedom. Here, we explore a technologically relevant oxide material, HfO2, which has been shown to exhibit robust ferroelectricity in a non-centrosymmetric orthorhombic phase. Using theoretical modelling based on density-functional theory, we investigate the spin-dependent electronic structure of the ferroelectric HfO2 and demonstrate the appearance of chiral spin textures driven by spin-orbit coupling. We analyze these spin configurations in terms of the Rashba and Dresselhaus effects within the k.p Hamiltonian model and find that the Rashba-type spin texture dominates around the valence band maximum, while the Dresselhaus-type spin texture prevails around the conduction band minimum. The latter is characterized by a very large Dresselhaus constant {\alpha}D = 0.578 eV {\AA}, which allows using this material as a tunnel barrier to produce tunneling anomalous and spin Hall effects that are reversible by ferroelectric polarization.

Visual Psychology Research on the Invariant Feature and Performance of Texture Recognition

Designed three visual psychological experiments to explore human ability on transformed texture discrimination and classical texture classification, and make some comparisons between human beings and computer algorithms. Some interesting results are obtained from these visual psychological experiments: (1) the invariance performance of sevral computer algorithms is appropriate to human beings; (2) texture is almost rotation invariant for human beings although single “b” and single “p” have significant different comprehension; (3) texture appearance depends on visual resolution. The biggest invariant scale of spatial scaling is roughly 2.3 times for human visual system at some fixed observation conditions; (4) some computer algorithms (such as MBF and Gabor) have achieved better performance than human beings under some restrictive conditions for fair comparison.

The application of pedicled anterolateral thigh propeller flaps in reconstruction of inguinal skin and soft tissue defects

Objective To discuss the effectiveness of anterolateral thigh propeller flaps for treatment of inguinal skin and soft tissue defects. Methods From June, 2009 to October, 2014, 12 patients with inguinal skin and soft tissue defects were treated with anterolateral thigh propeller flaps pedicled with perforator of descending branch of lateral circumflex femoral artery. Of them there were 8 males and 4 females, aged from 22 to 51 years. The left side was involved in 3 cases and right side 9 cases. Defects were caused by traffic accident injury in 5 cases, crash injury of heavy object in 7 cases. There were mere skin and soft tissue in 2 cases, combined with bone fractures, nerves, vessels and muscles injury in 10 cases. The area of defects ranged from 9.0 cm×5.0 cm to 22.0 cm×9.0 cm. During operation, anterolateral thigh propeller flaps ranging from 11.0 cm×7.0 cm to 24.0 cm×11.0 cm were used to repair the wounds. Results All flaps and skingrafts survived after operation and the wounds obtained primary healing. After 8-24 months follow-up, all flaps were characterized by soft texture, good color, and satisfactory appearance. According to the Britain’s Medical Research Council at 8 months after operation, the sensation of the flaps were recovered to S2~ S3+, No obvious scar contracture and chromatosis were observed at donor site. Conclusion Anterolateral thigh propeller flaps pedicled with artery descending branch of lateral circumflex femoral perforator is an ideal choice for the reconstruction for inguinal skin and soft tissue defects. Key words: Anterolateral thigh flaps; Propeller, perforator flaps; Descending branch of lateral circumflex femoral artery; Inguinal; Repair

Local binary circumferential and radial derivative pattern for texture classification

Building discriminative and robust texture representation to deal with the changes of texture appearance is a fundamental issue in texture classification. The Local Binary Pattern (LBP) and its variants gain a lot of attention during the past decade and achieve great success in texture description. However, the current existing LBP-based features which treat LBP as local differential or orientation gradient operator, exploited local orientation pattern or anisotropic structure information separately. In this paper, we investigate the theoretical scheme of local differential approximation on the polar coordinate system in order to build a new LBP-based descriptor which better takes into account both radial plus tangential components and derivative information. First, we present an operator called circumferential derivative (CD) based on the tangential information with different order of derivatives. Then, we present an operator called radial derivative (RD) based on the radial information with different order of derivatives. Both extract complementary information locally around a central pixel. A new descriptor, the local binary circumferential and radial derivative pattern (CRDP) is constructed to fuse both local circumferential and radial derivative features based on different orders as well as a global feature based on global difference (GD) of central pixel’s intensity. Extensive experiments on Outex, CUReT, KTH-TIPS and KTH-TIPS2-a texture datasets indicate that the proposed CRDP descriptor is discriminative and robust. The results obtained by the proposed CRDP descriptor outperforms more than twenty recent LBP-based state-of-the-art methods, including the best reported results in the literature for aforementioned texture datasets to the best of our knowledge.

The Influence of Lighting on The Appearance of Texture of Glossy and Matte fabric

The Influence of Lighting on The Appearance of Texture of Glossy and Matte fabric

Image denoising based on sparse representation and gradient histogram

Various image priors, such as sparsity prior, non-local self-similarity prior and gradient histogram prior, have been widely used for noise removal, while preserving the image texture. However, the gradient histogram prior used for texture enhancement sometimes generates false textures in the smooth areas. In order to address these problems, the authors propose a robust algorithm combining gradient histogram with sparse representation to obtain good estimates of the sparse coding coefficients of the latent image and realising image denoising while preserving the texture. The proposed model is solved by having a balance between over-enhancement and over-smoothing of the texture in order to preserve the natural texture appearance. Experimental results demonstrate the efficiency and effectiveness of the proposed method.

Evaluation of Quality Characteristics for Beef Cuts Following Different Production and Branding Approaches

ObjectivesConsumer demand has driven the expanding variety of fresh beef available for retail purchase, with considerably variable price points. The objective of this study was to assess the impact of production style and branding on the quality and sensory characteristics of ribeye steaks. Materials and MethodsThe varieties evaluated in this study were USDA Choice Black Angus, grass-fed, organic, USDA Prime, and Piedmontese. For each trial and variety, 5 steaks were cut to a target thickness of 3.18 cm from ribeye rolls procured from a local grocery store with sell-by dates within 3 d of each other. Steaks were individually overwrapped on foam trays with PVC film and stored at 1.1°C ± 2.0 under 175 ± 15 foot candle lighting for 7 d. Purge, color, cooked texture, and cook yield were measured on d 0, 1, 4, and 7 while sensory evaluation was conducted only on d 0. A Minolta colorimeter was used to measure L*a*b* values at 3 locations on the longissimus dorsi (LD) of each raw, overwrapped steak. Raw steaks were weighed and placed onto griddles preheated to 177°C, cooked to an internal temperature of 35°C, flipped over, and cooked to a final internal temperature of 70°C. For sensory analysis, eight semi-trained panelists evaluated 1.75 cm cubes of LD for aroma, juiciness, flavor, texture, and overall appearance using a nine-point hedonic scale to score, where 1 = dislike extremely and 9 = like extremely. After cooking, steaks used for texture analysis were allowed to cool for 2 h at room temperature before five cores (diameter = 1.5 cm) were taken from each steak parallel to the muscle fibers while avoiding visible exterior fat. Using a TA.XT Texture Analyzer, Warner-Bratzler shear force was measured perpendicular to the muscle fiber of each core using a rounded V-shaped blade with a 60° angle and a cross head speed of 200mm/min, where firmness equaled the maximum peak of the curve (kg) and toughness equaled the area under the curve (kg-s). This experiment was repeated three times. ResultsUSDA Prime and Piedmontese scored significantly higher (p ≤ 0.05) than all other varieties for overall acceptance with scores of 7.42 ± 1.22 and 7.04 ± 1.34, respectively. Although not always significant (p > 0.05), both USDA Prime and Piedmontese also received numerically higher ratings for all other sensory traits evaluated compared to other varieties. For d 1 objective texture measurements, USDA Prime displayed lower (p < 0.05) values for both firmness and toughness, while organic revealed the numerically highest value. At d 1 and 4 Piedmontese had significantly more purge (p < 0.05) than USDA Prime, USDA Choice Black Angus and organic, but by d 7 differences between all treatments were diminished. For any single variety, cook yields over time (ranging from 70.2 to 80.0%) were not always found consistently different than other varieties. USDA Prime had the highest a* value at d 0 (p ≤ 0.05) and was also significantly higher than organic on d 1, 4, and 7 (p < 0.05). ConclusionConsidering quality and sensory traits evaluated in this study, USDA Prime consistently stood out as being the most distinguishable branding type, while there were limited differences between Piedmontese, organic, grass-fed and USDA Choice.

Textural changes during recovery annealing of a heavily cold-rolled Fe–Mn–Al–Si–C alloy

A heavily cold-rolled (80%) high manganese austenitic steel was subjected to isochronal and isothermal heat treatments, in order to study the texture development during the recovery stage. Progress of recovery was negligible after annealing at 500°C for 60 min, but annealing for 60 min at 800°C led to complete recrystallisation, and appearance of the final texture was very similar to that of a copper type deformation texture. Isothermal heat treatments at 600°C revealed that at the very early stage of recovery, there was a weakening of brass type deformation texture, but it was followed by a sharpening of Bs component. At the same time, there was a shift of peak intensity towards Bs/Goss location. After this stage of intermediate sharpening, the texture sharpness experienced a continuous weakening with further progress of recovery.

Automatic Dynamic Texture Transformation Based on a New Motion Coherence Metric

Changing dynamic texture appearances can create new looks in both the motion and color appearances of videos. Dynamic textures with sophisticated shape and motion appearance are difficult to represent by physical models and are difficult to predict, especially for transformation to new motion texture. We propose a dynamic texture transformation algorithm for the video sequences based on the motion coherence of patches. We successfully apply the technology in many special effect videos, using the interactive tool we developed. In this paper, we address the issues of 3-D patch creation, motion coherence analysis, and patch matching for the dynamic texture transformation. The main contribution includes two issues. First, we propose a new metric for evaluating motion coherence with solid tests to justify the usefulness (close to human eye perception). Second, the proposed algorithm for an automatic dynamic texture transformation only needs users to segment textures on the first frame using an optional threshold to identify the texture area. The rest of the process is completed automatically. The experimental results show that the motion coherence index is effectively used to find the coherent motion region for patch matching and transformation. The experimental results, test data, source code, and system demonstration videos are posted at http://video.minelab.tw/DTT/index.html .

Unsupervised delineation of stratum corneum using reflectance confocal microscopy and spectral clustering.

Measuring the thickness of the stratum corneum (SC) in vivo is often required in pharmacological, dermatological, and cosmetological studies. Reflectance confocal microscopy (RCM) offers a non-invasive imaging-based approach. However, RCM-based measurements currently rely on purely visual analysis of images, which is time-consuming and suffers from inter-user subjectivity. We developed an unsupervised segmentation algorithm that can automatically delineate the SC layer in stacks of RCM images of human skin. We represent the unique textural appearance of SC layer using complex wavelet transform and distinguish it from deeper granular layers of skin using spectral clustering. Moreover, through localized processing in a matrix of small areas (called 'tiles'), we obtain lateral variation of SC thickness over the entire field of view. On a set of 15 RCM stacks of normal human skin, our method estimated SC thickness with a mean error of 5.4 ± 5.1 μm compared to the 'ground truth' segmentation obtained from a clinical expert. Our algorithm provides a non-invasive RCM imaging-based solution which is automated, rapid, objective, and repeatable.

Visualization of precut DSAEK and pre-stripped DMEK donor corneas by intraoperative optical coherence tomography using the RESCAN 700.

BackgroundTo report the feasibility of intraoperative spectral domain optical coherence tomography (OCT) using the RESCAN 700 for the visualization and evaluation of precut Descemet’s stripping automated endothelial keratoplasty (DSAEK) and prestripped Descemet’s membrane endothelial keratoplasty (DMEK) donor tissue.MethodsPrecut DSAEK (n = 11), prestripped DMEK (n = 4) preserved in a viewing chamber were examined by intraoperative OCT. Wholly intact donor corneas for penetrating keratoplasty (PK) (n = 8) were also examined as controls. The obtained images were analyzed qualitatively for characteristics of each type of donor.ResultsFor each type of donor, characteristic images were consistently obtained by intraoperative OCT in both the front and back views through the viewing chamber. In wholly intact donors for PK, appearance of normal corneal curvature and stromal texture with high reflectivity of epithelium and endothelium cell layers were clearly visualized. In precut DSAEK donors, precut lines were characteristically visualized in addition to the intact donor cornea images. In prestripped DMEK donors, identical OCT images to the intact donor cornea were noted when observed from the anterior surface. However, peripheral partial detachments of Descemet’s membrane were characteristically observed in all prestripped DMEK donors when viewed from the back of the viewing chamber.ConclusionRapid visualization and rough evaluation of donor tissues for PK, precut DSAEK and prestripped DMEK donor corneas by intraoperative OCT was consistently possible through the viewing chamber. Therefore, this device may be used as an alternative of AS-OCT when the eyebank does not have their own AS-OCT. Although the peripheral detachment in DMEK donors are quite common and clinically non-problematic in DMEK donor quality and subsequent DMEK surgeries, it may be useful to distinguish between wholly intact PK donors and prestripped DMEK donors, enabling to prevent mix-ups of donors, especially when several different types of keratoplasties are scheduled in a same day in one operating theater.

A Study on Development of Fortified Pasta with Ginger Powder

Pasta is a popular food and its quality can also measured by appearance of flavour and texture. Present study was undertaken to evaluate the quality of pasta supplemented with different quantities of ginger powder. In the present study four samples (C, C1, C2, and C3) of pasta were prepared by using refined wheat flour and different proportion of ginger powder. Sample C was prepared as control containing only refined wheat flour (100%) while sample C1 (refined wheat flour 99% ginger powder 1% ), C2 (refined wheat flour 97% ginger powder 3%) and C3 (refined wheat flour 95% ginger powder 5%) were prepared by changing the concentration of refined wheat flour and ginger powder. All the four samples were evaluated for the physicochemical properties (ash, texture and viscosity analysis), nutritional properties (carbohydrate, protein, fat, and fibre), cooking time and sensory quality. On the basis of results sample C2 (refined wheat flour 97% ginger powder 3%) was found to be best in quality having more nutritional element and higher overall acceptability.

Pituitary stalk thickening: the role of an innovative MRI imaging analysis which may assist in determining clinical management.

Disease processes that affect the pituitary stalk are broad; the diagnosis and management of these lesions remains unclear. The aim was to assess the clinical, biochemical and histopathological characteristics of pituitary stalk lesions and their association with specific MRI features in order to provide diagnostic and prognostic guidance. Retrospective observational study of 36 patients (mean age 37years, range: 4-83) with pituitary stalk thickening evaluated at a university hospital in Oxford, UK, 2007-2015. We reviewed morphology, signal intensity, enhancement and texture appearance at MRI (evaluated with the ImageJ programme), along with clinical, biochemical, histopathological and long-term follow-up data. Diagnosis was considered certain for 22 patients: 46% neoplastic, 32% inflammatory and 22% congenital lesions. In the remaining 14 patients, a diagnosis of a non-neoplastic disorder was assumed on the basis of long-term follow-up (mean 41.3months, range: 12-84). Diabetes insipidus and headache were common features in 47 and 42% at presentation, with secondary hypogonadism the most frequent anterior pituitary defect. Neoplasia was suggested on size criteria or progression with 30% sensitivity. However, textural analysis of MRI scans revealed a significant correlation between the tumour pathology and pituitary stalk heterogeneity in pre- and post-gadolinium T1-weighted images (sensitivity: 88.9%, specificity: 91.7%). New techniques of MRI imaging analysis may identify clinically significant neoplastic lesions, thus directing future therapy. We propose possible textural heterogeneity criteria of the pituitary stalk on pre- and post-gadolinium T1 images with the aim of differentiating between neoplastic and non-neoplastic lesions with a high degree of accuracy.

Time-varying weathering in texture space

We present a technique to synthesize time-varying weathered textures. Given a single texture image as input, the degree of weathering at different regions of the input texture is estimated by prevalence analysis of texture patches. This information then allows to gracefully increase or decrease the popularity of weathered patches, simulating the evolution of texture appearance both backward and forward in time. Our method can be applied to a wide variety of different textures since the reaction of the material to weathering effects is physically-oblivious and learned from the input texture itself. The weathering process evolves new structures as well as color variations, providing rich and natural results. In contrast with existing methods, our method does not require any user interaction or assistance. We demonstrate our technique on various textures, and their application to time-varying weathering of 3D scenes. We also extend our method to handle multi-layered textures, weathering transfer, and interactive weathering painting.

톳(Hizikia fusiformis)을 첨가한 흰찰쌀보리죽의 제조 및 품질특성

This study was conducted to evaluate the physicochemical characteristics, perform a sensory evaluation of glutinous barley gruel after adding Hizikia fusiformis powder to promote consumption, and identify the best ratio and recipe. The gruel was prepared with rice and glutinous barley powder, and various levels (0, 2.5, 5.0, and 7.5%) of H. fusiformis powder. pH, color, viscosity, and spreadability of the gruel were investigated. A sensory evaluation was conducted by 20 panelists in the categories of color, flavor, taste, texture appearance, and overall preference using a 9-point hedonic scale. The viscosity and pH of the gruel increased as H. fusiformis powder content increased, whereas spreadability of the gruel decreased gradually as H. fusiformis powder content increased. As the level of H. fusiformis powder increased, lightness decreased significantly, whereas redness and yellowness increased. Color, bitter taste, and H. fusiformis flavor of the gruel increased significantly as H. fusiformis powder content increased. On the other hand, sweet taste (delicious taste level) and viscosity were not different among the different gruels. The sensory test results indicated that the gruel with 5% H. fusiformis powder had the best overall acceptability. In conclusion, glutinous barley gruel with 5% added H. fusiformis powder was more acceptable than the others.

Spontaneous Spin Textures in Multiorbital Mott Systems.

Spin textures in k-space arising from spin-orbit coupling in noncentrosymmetric crystals find numerous applications in spintronics. We present a mechanism that leads to the appearance of k-space spin texture due to spontaneous symmetry breaking driven by electronic correlations. Using dynamical mean-field theory we show that doping a spin-triplet excitonic insulator provides a means of creating new thermodynamic phases with unique properties. The numerical results are interpreted using analytic calculations within a generalized double-exchange framework.

Physico-chemical and sensory evaluation of potato (Solanum tuberosum L.) after irradiation.

This work evaluated the effects of ionizing radiation on the physico-chemical and sensory characteristics of the potato cultivar Ágata (Solanum tuberosum L.), including budding and deterioration, with the end goal of increasing shelf life. For this, four groups of samples were harvested at the maturation stage. Three of them were separately exposed to a Co-60 source, receiving respective doses of 0.10, 0.15 and 2.00 kGy, while the non-irradiated group was kept as a control. All samples were stored for 35 days at 24 °C (± 2) and at 39% relative humidity. The following aspects were evaluated: budding, rot, loss of weight, texture, flesh color, moisture, external and internal appearance, aroma, soluble solids, titratable acidity, vitamin C, protein, starch and glucose. The results indicated that 0.15 kGy was the most effective dose to reduce sprouting and post-harvest losses, under the conditions studied.

SU‐F‐R‐57: Validation of Quantitative Radiomic Texture Features for Oncologic MRI: A Simulation Study

Purpose:Radiomic texture features extracted from diverse MRI modalities have been investigated regarding their predictive and prognostic values in a variety of cancers. However, their validity has not yet been fully assessed. With the aid of a digital MRI phantom, the objective of this study was to examine the validity and reliability of MRI texture metrics.Methods:MR signal of the employed digital phantom was simulated in a multiple coil setting with realistic acquisition noise. Three iterative algorithms based respectively on conjugate gradient (CG), total variation (TV), and wavelet regularization (WL) were used for image reconstruction. For each algorithm, 80 independent simulations were carried out with different levels of noise perturbation. 22 features related to grey‐level co‐occurrence matrices (GLCOM), zone size matrices (GLZSM), and neighborhood difference matrices (GLNDM) were evaluated for each resultant image within two ROIs featuring heterogeneous patterns of signal intensity on the ground truth image. Texture features extracted from these simulated images were compared to those from the ground truth image, and differences were identified.Results:In comparison to the ground truth data, texture features appearing on images reconstructed with CG, TV, and WL from signal with no noise perturbation varied with a range of 0.18–3.3×104%, 0.57–3.6×104%, and 0.84–3.5×104%, respectively while varying more significantly for noisy data with largest variation of 2.6×105% for CG, 2.2×105% for TV, and 2.8×105% for WL. Texture differences between ROIs also revealed considerable extent of variation from those on the ground truth image with a range of 1.91–4.9×104% for CG‐based data, 27.50–3.0×104% for TV‐based, and 11.99‐3.2×104% for WL‐based.Conclusion:Variability of texture appearance on MRI with respect to the choice of reconstruction algorithm and noise level is significant and feature‐dependent. Certain texture features may be preserved by MR imaging; however adequate precautions need to be taken on their validity and reliability.

SU‐F‐R‐36: Validating Quantitative Radiomic Texture Features for Oncologic PET: A Digital Phantom Study

Purpose:Radiomic texture features derived from the oncologic PET have recently been brought under intense investigation within the context of patient stratification and treatment outcome prediction in a variety of cancer types; however, their validity has not yet been examined. This work is aimed to validate radiomic PET texture metrics through the use of realistic simulations in the ground truth setting.Methods:Simulation of FDG‐PET was conducted by applying the Zubal phantom as an attenuation map to the SimSET software package that employs Monte Carlo techniques to model the physical process of emission imaging. A total of 15 irregularly‐shaped lesions featuring heterogeneous activity distribution were simulated. For each simulated lesion, 28 texture features in relation to the intensity histograms (GLIH), grey‐level co‐occurrence matrices (GLCOM), neighborhood difference matrices (GLNDM), and zone size matrices (GLZSM) were evaluated and compared with their respective values extracted from the ground truth activity map.Results:In reference to the values from the ground truth images, texture parameters appearing on the simulated data varied with a range of 0.73–3026.2% for GLIH‐based, 0.02–100.1% for GLCOM‐based, 1.11–173.8% for GLNDM‐based, and 0.35–66.3% for GLZSM‐based. For majority of the examined texture metrics (16/28), their values on the simulated data differed significantly from those from the ground truth images (P‐value ranges from &lt;0.0001 to 0.04). Features not exhibiting significant difference comprised of GLIH‐based standard deviation, GLCO‐based energy and entropy, GLND‐based coarseness and contrast, and GLZS‐based low gray‐level zone emphasis, high gray‐level zone emphasis, short zone low gray‐level emphasis, long zone low gray‐level emphasis, long zone high gray‐level emphasis, and zone size nonuniformity.Conclusion:The extent to which PET imaging disturbs texture appearance is feature‐dependent and could be substantial. It is thus advised that use of PET texture parameters for predictive and prognostic measurements in oncologic setting awaits further systematic and critical evaluation.

Full Dose-Reduction Potential of Statistical Iterative Reconstruction for Head CT Protocols in a Predominantly Pediatric Population.

A statistical iterative reconstruction algorithm provides an effective approach to reduce patient dose by compensating for increased image noise in CT due to reduced radiation output. However, after a point, the degree to which a statistical iterative algorithm is used for image reconstruction changes the image appearance. Our aim was to determine the maximum level of statistical iterative reconstruction that can be used to establish dose-reduced head CT protocols in a primarily pediatric population while maintaining similar appearance and level of image noise in the reconstructed image. Select head examinations (brain, orbits, sinus, maxilla, and temporal bones) were investigated. Dose-reduced head protocols using an adaptive statistical iterative reconstruction were compared for image quality with the original filtered back-projection reconstructed protocols in a phantom by using the following metrics: image noise frequency (change in perceived appearance of noise texture), image noise magnitude, contrast-to-noise ratio, and spatial resolution. Dose-reduction estimates were based on CT dose index values. Patient volume CT dose index and image noise magnitude were assessed in 737 pre- and post-dose-reduced examinations. Image noise texture was acceptable for up to 60% adaptive statistical iterative reconstruction for the soft reconstruction kernel (at both 100 and 120 kV[peak]) and up to 40% adaptive statistical iterative reconstruction for the standard reconstruction kernel. Implementation of 40% and 60% adaptive statistical iterative reconstruction led to an average reduction in the volume CT dose index of 43% for brain, 41% for orbit, 30% for maxilla, 43% for sinus, and 42% for temporal bone protocols for patients between 1 month and 26 years of age, while maintaining an average noise magnitude difference of 0.1% (range, -3% to 5%), improving the contrast-to-noise ratio of low-contrast soft-tissue targets and the spatial resolution of high-contrast bony anatomy, compared with filtered back-projection. The methodology in this study demonstrates maximizing patient dose reduction and maintaining image quality by using statistical iterative reconstruction for a primarily pediatric population undergoing head CT examinations.