Scanning Conditions Research Articles

Comparison of the Analysis of Respirable Crystalline Silica in Workplace Air by Direct-on-Filter Methods using X-ray Diffraction and Fourier Transform Infrared Spectroscopy.

A comparison of the analysis of respirable crystalline silica direct-on-filter methods using X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy was undertaken using 253 real workplace air samples from road construction and tunnelling, coal mining, and kitchen benchtop manufacturing in Australia. Using pure α-quartz standards, XRD and FT-IR direct-on-filter analyses produced identical test results, however, the real workplace samples showed a clear discrepancy between FT-IR and XRD results with on average a 9% positive bias of the FT-IR results. The cause of the positive bias was due to matrix interferences which was confirmed by using synthetic mixture air samples. Approximately a third of the data by direct-on-filter method using FT-IR was assessed to be invalid based on the peak height ratio criterion due to excessive interferences and weight overload limitations. The XRD method showed better results due to less interference from the common matrices. XRD could handle up to twice the sample loading and at higher loadings up to 7 mg when a correction was applied. It was also able to achieve a lower limit of detection of 2 µg filter−1 when a slower scan condition was utilized.

Back-to-Basics tutorial: X-ray diffraction of thin films

X-ray diffraction (XRD) is an indispensable tool for characterising thin films of electroceramic materials. For the beginner, however, it can be a daunting technique at first due to the number of operation modes and measurements types, as well as the interpretation of the resultant patterns and scans. In this tutorial article, we provide a foundation for the thin-film engineer/scientist conducting their first measurements using XRD. We give a brief introduction of the principle of diffraction and description of the instrument, detailing the relevant operation modes. Next, we introduce five types of measurements essential for thin film characterisation: \(2\theta /\omega\) scans, grazing-incidence scans, rocking curves, pole figures, and azimuth scans (or ϕ scans). Practical guidelines for selecting the appropriate optics, mounting and aligning the sample, and selecting scan conditions are given. Finally, we discuss some of the basics of data analysis, and give recommendations on the presentation of data. The aim of this article is to ultimately lower the barrier for researchers to perform meaningful XRD analysis, and, building on this foundation, find the existing literature more accessible, enabling more advanced XRD investigations.

Microstructural development and aging behavior of Al–Cr–Zr heat-resistant alloy fabricated using laser powder bed fusion

Using laser powder bed fusion (L-PBF), we designed and fabricated specimens of a heat-resistant Al–4mass%Cr–1.5mass%Zr alloy (Al–4Cr–1.5Zr). The Al–4Cr–1.5Zr L-PBF specimen achieved high relative density greater than 99.9% by optimizing the laser scan conditions. The hardness and tensile and 0.2% proof stresses of the Al–4Cr–1.5Zr L-PBF specimens significantly increased after aging heat treatments, and the peak-aged specimens exhibited excellent high-temperature strength. The L-PBF specimens consisted of coarse columnar and fine equiaxed crystal grains owing to heterogeneous nucleation by the primarily crystallized Al3Zr phase. In the peak-aged L-PBF specimen, a finely dispersed Al3Zr granular phase on the order of single nanometers was precipitated in the α-Al matrix by aging. Meanwhile, the chromium was supersaturated in an α-Al solid solution even after peak aging, and partially precipitated into coarse granular Al–Cr-based compounds. These multi-scale microstructural observation results revealed that the dominant strengthening factors in the Al–4Cr–1.5Zr L-PBF specimens were precipitation hardening by the fine L12-Al3Zr phase having a strong crystallographic consistency with the α-Al matrix, solid-solution hardening with chromium, dispersion hardening due to the Al–Cr-based compounds, and hardening by the crystal grain refinement mainly with the fine equiaxed grains.

Advanced Maximum Power Point Tracker for PV Systems Under Dusty Weather Environments

Dusty weather is a most important disturbance for photovoltaic (PV) systems, that may result in PV panels exposure to partial shading conditions where the PV panel characteristics show several maximum power points. Moreover, dusty weather conditions may lead to rapid changes in solar radiations. Thus, conventional power system tracking algorithms are not being capable to track the global maximum power point (GMPP). This paper provides an advanced maximum power point tracker for partial shading and dusty weather conditions. In the presented technique, scanning and power lock conditions are added to the conventional perturbations and observation technique in photovoltaic system under partial shading or dusty weather conditions. This tracking method scans the PV characteristic in steps and stores all the maximum power points in order to get the GMPP. The proposed tracker is capable to identify the uniform weather conditions to save it from having unnecessary scanning. In addition, this tracker permits dynamic tracking of the GMPP under dusty weather conditions with less fluctuations and stable operation compared to the conventional methods. Accurate and fast conversion to the GMPP during various weather conditions is accomplished using the proposed technique. The proposed modified perturb and observe technique is validated using simulation and practical results. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

CT image quality influence on different material Edge Response Functions for accurate metrological applications

The main objective of the proposed work was to analyse the influence of magnification and focal spot size scan settings on X-ray computed tomography (CT) measurements results under commercial threshold-based algorithms. The relationship between spatial resolution and contrast sensitivity in CT scans of different materials and the accuracy of the resulting CT measurement results is discussed. For that purpose, Aluminium, Copper, Inconel 718 and Titanium disk phantoms were scanned. Preliminary measurements showed that deviations can increase up to 0.48% when the scanning magnification was increased while, for a given magnification, the decrease of a focus size from 1mm to 0.4mm slightly improves the differences up to 0.15%, being negligible at low magnifications. Unsharpness (U T ) and contrast-to-noise ratio (CNR) were calculated for each scanning conditions according to standard ASTM E1695 – 20. A new image quality indicator that includes the combined effect of the U T and CNR was proposed in order to relate measurement error with the image quality. The indicator proves that the influence of CNR is much higher than influence of U T on the CT measurements.

Sparse and continuous sampling approaches to fMRI of overt vocalization tasks

Sparse temporal sampling has become the dominant paradigm for functional magnetic resonance imaging studies of auditory stimuli or verbal responses, as it allows the presentation or production of stimuli during the relatively quiet periods when there is no gradient switching and ensures that task-related movements are not occurring during scan acquisitions. To date, however, there has been no direct comparison between sparse and continuous acquisition protocols for overt auditory-verbal studies (i.e., speaking or singing). The aim of this study was to determine whether sparse temporal sampling would reduce movement artefacts and show better network activation for overt singing compared to continuous imaging. Fifteen healthy adults performed the same overt singing task under both sparse and continuous scanning conditions. We noted significant variations in signal intensity between adjacent slices in our sparse acquisition, with (odd-numbered) slices acquired in the second half of each volume acquisition being of lower intensity and showing less reliable task-related activation, and thus requiring the removal of these slices prior to preprocessing. Edge artefacts, presumably due to movement, were observed in both acquisition types at a subthreshold level, although ventricular space artefacts were more apparent in the continuous data. However, statistical comparison revealed no significant differences in functional activation nor in motion correction parameters. Our results show that sparse imaging has the potential to introduce significant image artefacts affecting downstream analyses. While sparse sampling provides benefits that may be essential for certain studies (e.g., periods free from scanner noise), the technical requirements of such sequences should not be overlooked and inspection of raw data is essential. Our data also show that continuous imaging can be used for overt response auditory-verbal studies and may be of wider utility than previously appreciated.

Virtual Monoenergetic Images of Dual-Energy CT-Impact on Repeatability, Reproducibility, and Classification in Radiomics.

Simple SummaryVirtual monoenergetic images from dual-energy CT are incrementally used in routine clinical practice. Thus, radiomic analysis will be more often performed on these images in the future. This study characterized the test–retest repeatability and reproducibility of radiomic features from virtual monoenergetic images and their impact on machine-learning-based lesion classification. The results of this study provide a basis to improve radiomic analyses and identify the role of feature stability in classification tasks when using virtual monoenergetic imaging with different scan or reconstruction parameters in multicenter clinical studies.The purpose of this study was to (i) evaluate the test–retest repeatability and reproducibility of radiomic features in virtual monoenergetic images (VMI) from dual-energy CT (DECT) depending on VMI energy (40, 50, 75, 120, 190 keV), radiation dose (5 and 15 mGy), and DECT approach (dual-source and split-filter DECT) in a phantom (ex vivo), and (ii) to assess the impact of VMI energy and feature repeatability on machine-learning-based classification in vivo in 72 patients with 72 hypodense liver lesions. Feature repeatability and reproducibility were determined by concordance–correlation–coefficient (CCC) and dynamic range (DR) ≥0.9. Test–retest repeatability was high within the same VMI energies and scan conditions (percentage of repeatable features ranging from 74% for SFDE mode at 40 keV and 15 mGy to 86% for DSDE at 190 keV and 15 mGy), while reproducibility varied substantially across different VMI energies and DECTs (percentage of reproducible features ranging from 32.8% for SFDE at 5 mGy comparing 40 with 190 keV to 99.2% for DSDE at 15 mGy comparing 40 with 50 keV). No major differences were observed between the two radiation doses (<10%) in all pair-wise comparisons. In vivo, machine learning classification using penalized regression and random forests resulted in the best discrimination of hemangiomas and metastases at low-energy VMI (40 keV), and for cysts at high-energy VMI (120 keV). Feature selection based on feature repeatability did not improve classification performance. Our results demonstrate the high repeatability of radiomics features when keeping scan and reconstruction conditions constant. Reproducibility diminished when using different VMI energies or DECT approaches. The choice of optimal VMI energy improved lesion classification in vivo and should hence be adapted to the specific task.

Underground Pipeline Identification into a Non-Destructive Case Study Based on Ground-Penetrating Radar Imaging

Ground-penetrating radar (GPR) has become one of the key technologies in subsurface sensing and, in general, in nondestructive testing (NDT), since it is able to detect both metallic and nonmetallic targets. GPR has proven its ability to work in electromagnetic frequency range for subsoil investigations, and it is a risk-reduction strategy for surveying underground various targets and their identification and detection. This paper presents the results of a case study which exceeds the laboratory level being realized in the field in a real case where the scanning conditions are much more difficult using GPR signals for detecting and assessing underground drainage metallic pipes which cross an area with large buildings parallel to the riverbed. The two urban drainage pipes are detected based on GPR imaging. This provides an approximation of their location and depth which are convenient to find from the reconstructed profiles of both simulated and practical GPR signals. The processing of data recorded with GPR tools requires appropriate software for this type of measurement to detect between different reflections at multiple interfaces located at different depths below the surface. In addition to the radargrams recorded and processed with the software corresponding to a GPR device, the paper contains significant results obtained using techniques and algorithms of the processing and post-processing of the signals (background removal and migration) that gave us the opportunity to estimate the location, depth, and profile of pipes, placed into a concrete duct bank, under a structure with different layers, including pavement, with good accuracy.

A New Pipeline to Automatically Segment and Semi-Automatically Measure Bone Length on 3D Models Obtained by Computed Tomography.

The characterization of developmental phenotypes often relies on the accurate linear measurement of structures that are small and require laborious preparation. This is tedious and prone to errors, especially when repeated for the multiple replicates that are required for statistical analysis, or when multiple distinct structures have to be analyzed. To address this issue, we have developed a pipeline for characterization of long-bone length using X-ray microtomography (XMT) scans. The pipeline involves semi-automated algorithms for automatic thresholding and fast interactive isolation and 3D-model generation of the main limb bones, using either the open-source ImageJ plugin BoneJ or the commercial Mimics Innovation Suite package. The tests showed the appropriate combination of scanning conditions and analysis parameters yields fast and comparable length results, highly correlated with the measurements obtained via ex vivo skeletal preparations. Moreover, since XMT is not destructive, the samples can be used afterward for histology or other applications. Our new pipelines will help developmental biologists and evolutionary researchers to achieve fast, reproducible and non-destructive length measurement of bone samples from multiple animal species.

Onset of selective laser flash sintering of AlN

AbstractFlash sintering uses a combination of heating and electric fields to rapidly densify ceramics. Previously, it has been shown that a scanning laser can be used to initiate flash sintering in localized regions on an yttria‐stabilized zirconia (YSZ) sample in a process known as selective laser flash sintering (SLFS). In this work, we show using a combination of measurements of electric current flowing through the sample and observations of necks formed between powder particles that aluminum nitride (AlN) can also undergo SLFS. Scan conditions required to initiate SLFS are characterized over a range of laser powers and laser scan speeds in a dry nitrogen environment. It is shown that initiation of SLFS in AlN is governed by both the local input energy density per scan and heat dissipation and a numerical model is developed to predict temperatures during SLFS. Assuming the minimum temperature along the conductive path determines the onset of SLFS, the minimum temperature and time required is 450–670 K in 2–0.25 s for the pressed AlN pellets used in this study for laser scan speeds of 33–300 m/s, laser powers of 10–30 W, and an applied electric field of 3000 V/cm.

Basic features of VIC-T dosimeter with spiral CT readout, CT scanning conditions and data processing with a new polyGeVero-CT software package

This work reports on the results obtained for VIC-T dosimeter for radiotherapy dosimetry (17 % (w/v) N-vinylpyrrolidone, 8 % (w/v) N,N′-methylenebisacrylamide, 12 % (w/v) tert-butyl alcohol, 5 % (w/v) gelatine, 0.02 % (w/v) hydroquinone and 14 mM tetrakis (hydroxymethyl) phosphonium chloride (THPC)) measured with a spiral computed tomography (CT). Optimal spiral CT protocol, CT measurements conditions and image processing are provided. Basic features of VIC-T are discussed such as a calibration relation and dose resolution with respect to former N-vinylpyrrolidone containing dosimeters. Both adopted data processing performed with a new polyGeVero®-CT software package and its features are reported.

Quantitative characterisation of ballistic cartridge cases from micro-CT

Evaluation of cartridge cases is essential within forensic ballistic analysis and is used in an attempt to establish a connection to the weapon used to fire it. This study consists of two experiments. The aims of Experiment 1 were to establish whether micro-CT is appropriate and repeatable for ballistic cartridge case analysis and if measurements can be extracted repeatably and reliably. Experiment 2 aimed to compare cartridge cases from two weapons to establish the magnitude of variation within and between weapons. A total of 48 cartridge cases fired by two distinct weapons were collected and micro-CT scanned to a high resolution. One randomly selected cartridge was scanned ten times under the same conditions to ensure repeatability of the scanning conditions in Experiment 1. Three novel measurements to quantitatively assess the firing pin impressions were proposed in Experiment 1 and comparatively analysed from two weapons in Experiment 2. Experiment 1 showed that micro-CT is an effective and highly repeatable and reliable method for 3-dimensional imaging and measurement of ballistic cartridge cases. Furthermore, high agreement for inter-rater reliability was found between five raters. Quantitative micro-CT analysis of the firing pin impression measurements in Experiment 2 showed a significant difference between the two studied weapons using Welch’s t-test (p < 0.01). This study shows the advantage and reliability of utilising micro-CT for firing pin impression analysis. Quantitation of the firing pin impression allows distinction between the weapons studied. With expansion to further weapons, application of this methodology could complement current analysis techniques through classification models.

Safety and data quality of EEG recorded simultaneously with multi-band fMRI.

Simultaneously recorded electroencephalography and functional magnetic resonance imaging (EEG-fMRI) is highly informative yet technically challenging. Until recently, there has been little information about EEG data quality and safety when used with newer multi-band (MB) fMRI sequences. Here, we measure the relative heating of a MB protocol compared with a standard single-band (SB) protocol considered to be safe. We also evaluated EEG quality recorded concurrently with the MB protocol on humans. We compared radiofrequency (RF)-related heating at multiple electrodes and magnetic field magnitude, B1+RMS, of a MB fMRI sequence with whole-brain coverage (TR = 440 ms, MB factor = 4) against a previously recommended, safe SB sequence using a phantom outfitted with a 64-channel EEG cap. Next, 9 human subjects underwent eyes-closed resting state EEG-fMRI using the MB sequence. Additionally, in three of the subjects resting state EEG was recorded also during the SB sequence and in an fMRI-free condition to directly compare EEG data quality across scanning conditions. EEG data quality was assessed by the ability to remove gradient and cardioballistic artifacts along with a clean spectrogram. The heating induced by the MB sequence was lower than that of the SB sequence by a factor of 0.73 ± 0.38. This is consistent with an expected heating ratio of 0.64, calculated from the square of the ratio of B1+RMS values of the sequences. In the resting state EEG data, gradient and cardioballistic artifacts were successfully removed using traditional template subtraction. All subjects showed an individual alpha peak in the spectrogram with a posterior topography characteristic of eyes-closed EEG. The success of artifact rejection for the MB sequence was comparable to that in traditional SB sequences. Our study shows that B1+RMS is a useful indication of the relative heating of fMRI protocols. This observation indicates that simultaneous EEG-fMRI recordings using this MB sequence can be safe in terms of RF-related heating, and that EEG data recorded using this sequence is of acceptable quality after traditional artifact removal techniques.

Автоматизована система безконтактного ультразвукового неруйнівного контролю якості корпусів ракетних двигунів твердого палива з композиційних матеріалів

Currently, in various industries (engineering, aircraft, energy, etc.) the issue of product quality assurance and control is particularly acute. This is due primarily to the ever-increasing requirements for increasing reliability with increasing loads on products, which entails the strengthening of technical standards. The issue of quality control for rocket and space technology products is especially relevant. Modern power structures of rocket and spacecraft made of polymer composite materials, and especially the body of solid fuel rocket engines (SFRЕ), are multilayer packages of various polymer-composite materials (PKM), obtained and interconnected in the process of manufacturing the body. The efficiency of SFRЕ depends on the quality of the formation of PKM in production conditions. The most important issues are the implementation of production quality control of composite structures, the reliability of control results and the ability to automate the control process. The article presents an automated system of non-contact ultrasonic non-destructive testing, which allows to control the stability of the technological process of forming the composite material of the wall of the SFRЕ body and, if necessary, to adjust it. The probability of detecting zones of anomalous violation of the integrity of the wall material of the SFRЕ housing is carried out due to adaptive algorithms, digital systems of multilevel matrix processing and optimal filtering of the received signals. The automated system of contactless ultrasonic non-destructive quality control of SFRЕ cases allows to register conditions of scanning and control for more visual representation of the defectogram in the expanded look of the case of a product in the course of control and at documentation of its results. The presented results of work on the development of an automated system of non-destructive testing of the integrity of the buildings of the SFRЕ type "cocoon" confirm the possibilities of practical implementation in production.

Multifiller nanocomposites containing gadolinium oxide and bismuth nanoparticles with enhanced X‐ray attenuation property

AbstractWe report here the development of multifiller nanocomposite containing gadolinium oxide and bismuth nanofillers with enhanced X‐ray attenuation property. The mass attenuation coefficient of the nanocomposite is found to be 5.26 (X‐ray attenuation: 95%) and 2.22 cm2/g (X‐ray attenuation: 71%), respectively, under dental and lung X‐ray scan conditions. Fourier transform infrared spectroscopy confirms the interfacial interaction between Gd2O3 nanofillers and the polymer matrix through hydrogen bonding. Atomic force microscopy images of the nanocomposite show a smooth and uniform topography with an average surface roughness of ~19 nm. Thermogravimetric analysis confirms the thermal stability of the nanocomposite upto 384°C. The enhanced X‐ray attenuation property of the nanocomposite is attributed to the good interfacial bonding, dual k‐edge effect of nanofillers and their uniform distribution within the polymeric matrix. Therefore, this nanocomposite is a promising material for diagnostic X‐ray shielding, especially as, thyroid collar, gonad shield, aprons, gloves, and so on.

Scan time and accuracy of full-arch scans with intraoral scanners: a comparative study on conditions of the intraoral head-simulator and the hand-held model

Objective: To comparatively evaluate the scan time and the accuracy of maxillary full-arch scans using four intraoral scanners (IOS) on conditions of the intraoral head-simulator and the hand-held model, and to evaluate the influence of different scanning conditions on digital scan. Methods: A upper dental arch model with melamine-formaldehyde resin teeth and silica gel gingiva that could be fixed on a head simulator was scanned with an optical scanner (ATOS Core) in order to obtain the standard tessellation language dataset as reference. Intraoral scans were performed on the model fixed on the head simulator by three researchers with four IOS [A: TRIOS 3; B: CS 3600; C: CEREC Omnicam; D: iTero]. For each scanner and each researcher, six scans were performed, to obtain the datasets as the head simulator group. And another six scans with each of the four intraoral scanners were performed by each researcher on the hand-held model to obtain the STL datasets as the hand-held group. The scan time were recorded for each scan. In the Geomagic Wrap software, the digital models were trimmed with only the teeth information retained and supreimposed by best fit alignment function and compared to obtain the root mean square (RMS) values of the discrepancies by three-dimensional compare function. The test datasets of each group were compared with the reference dataset for trueness. The six test scanning datasets with the same scanner of the same researcher were cross compared for precision. Mann Whitney U test was used to statistically analyze the difference values of the scan time, trueness and precision of the same intraoral scanner between head simulator group and hand-held group. Results: Compared to the hand-held group, the scan time of A [142(82) s] and D [119(52) s], which two IOS both with handle, were longer in head simulator group [A: 98(28) s; D: 85(22) s] (P<0.01). However there were no significant differences between the two groups for scan time of IOS B and C (P>0.05). For full-arch scan accuracy (trueness and precision), there were no significant differences between the two groups of IOS A and B (P>0.05), while the trueness of C (P<0.05) and the precision of D (P<0.01) were better in head simulator group [C: 112(38) μm; D: 43(13) μm] compared to hand-held group [C: 135(47) μm; D: 53(18) μm]. However, there were no significant differences for the precision of C (P>0.05) and the trueness of D (P>0.05). Conclusions: The scan time and the accuracy of full-arch digital scans with different IOS may be effected by the scan conditions. For in vitro study of intraoral scanning, head-simulator can simulate the intraoral environment of the real patient to some extent. Meanwhile, the position of the dentist and the patient, and also the limited intraoral space during intraoral scanning are also simulated.

Insight to agglomeration and chemical reactions of CoAl2O4 inoculants in IN718 processed by selective laser melting

The investigation aims to clarify the influence of scan parameters on the morphology and phase constitution of CoAl2O4 inoculants in Inconel 718 (IN718) superalloy processed by selective laser melting (SLM). Gas atomized IN718 powder feedstock was uniformly blended with 0.2 wt% of CoAl2O4 flakes and processed with a range of laser scan parameters to understand the effect of the inoculant additions on microstructure. Similar to the reactions observed in investment cast Ni-superalloys, the CoAl2O4 particles were found to chemically react with elemental Al, Cr, and Ti present in the melt pool of IN718 and become reduced into Al2O3, Cr2O3, and TiO2 oxides after the SLM process. Analyses of single melt pool beads revealed the existence of Co-rich metallic particles distributed along the surface of the oxides. However, since SLM processing involves remelting of the previously deposited layers to minimize the occurrence of porosity, this results in the dissolution of the Co-rich metallic particles that form when the CoAl2O4 particles are reduced in the melt pool. As such, the ability of the metallic Co particles to contribute to grain refinement becomes limited during SLM processing. Furthermore, the inoculant particles were found to agglomerate along the scan direction. The underlying mechanisms can be attributed to the Marangoni convection following the moving center of laser beam. It was found that decreasing energy density and increasing scan speed can effectively reduce the size and number density of the agglomerated oxide particles. Faster laser scan velocities lead to reduced convective flow within the melt pool and reduce the tendency for agglomeration. However, the reduced magnitude of energy input limited the time over which the CoAl2O4 particles could react with the melt pool. This led to the formation of lack of fusion defects and incomplete chemical reaction between CoAl2O4 and IN718 after the SLM process. The effectiveness of CoAl2O4 inoculant particles on grain refinement in as-built SLM IN718 microstructures is strongly dependent on the melt pool physics and laser scan conditions.

Fine-tuning neural excitation/inhibition for tailored ketamine use in treatment-resistant depression

The glutamatergic modulator ketamine has been shown to rapidly reduce depressive symptoms in patients with treatment-resistant major depressive disorder (TRD). Although its mechanisms of action are not fully understood, changes in cortical excitation/inhibition (E/I) following ketamine administration are well documented in animal models and could represent a potential biomarker of treatment response. Here, we analyse neuromagnetic virtual electrode time series collected from the primary somatosensory cortex in 18 unmedicated patients with TRD and in an equal number of age-matched healthy controls during a somatosensory ‘airpuff’ stimulation task. These two groups were scanned as part of a clinical trial of ketamine efficacy under three conditions: (a) baseline; (b) 6–9 h following subanesthetic ketamine infusion; and (c) 6–9 h following placebo-saline infusion. We obtained estimates of E/I interaction strengths by using dynamic causal modelling (DCM) on the time series, thereby allowing us to pinpoint, under each scanning condition, where each subject’s dynamics lie within the Poincaré diagram—as defined in dynamical systems theory. We demonstrate that the Poincaré diagram offers classification capability for TRD patients, in that the further the patients’ coordinates were shifted (by virtue of ketamine) toward the stable (top-left) quadrant of the Poincaré diagram, the more their depressive symptoms improved. The same relationship was not observed by virtue of a placebo effect—thereby verifying the drug-specific nature of the results. We show that the shift in neural dynamics required for symptom improvement necessitates an increase in both excitatory and inhibitory coupling. We present accompanying MATLAB code made available in a public repository, thereby allowing for future studies to assess individually tailored treatments of TRD.

Toward a comparison and an optimization of CT protocols using new metrics of dose and image quality part I: prediction of human observers using a model observer for detection and discrimination tasks in low-dose CT images in various scanning conditions

In the context of reducing the patient dose coming from CT scanner examinations without penalizing the diagnosis, the assessment of both patient dose and image quality (IQ) with relevant metrics is crucial. The present study represents the first stage in a larger work, aiming to compare and optimize CT protocols using dose and IQ new metrics. We proposed here to evaluate the capacity of the Non-PreWhitening matched filter with an eye (NPWE) model observer to be a robust and accurate estimation of IQ. We focused our work on two types of clinical tasks: a low contrast detection task and a discrimination task. We designed a torso-shaped phantom, including Plastic Water® slabs with cylindrical inserts of different diameters, sections and compositions. We led a human observer study with 13 human observers on images acquired in multiple irradiation and reconstruction scanning conditions (voltage, pitch, slice thickness, noise level of the reconstruction algorithm, energy level in dual-energy mode and dose), to evaluate the behavior of the model observer compared to the human responses faced to changing conditions. The model observer presented the same trends as the human observers with generally better results. We rescaled the NPWE model on the human responses by scanning conditions (kVp, pitch, slice thickness) to obtain the best agreement between both observer types, estimated using the Bland-Altman method. The impact of some scanning parameters was estimated using the correct answer rate given by the rescaled NPWE model, for both tasks and each insert size. In particular, the comparison between the dual-energy mode at 74 keV and the single-energy mode at 120 kVp showed that, if the 120 kVp voltage provided better results for the smallest insert at the lower doses for both tasks, their responses were equivalent in many cases.

Technical Note: validation of a material assignment method for a retrospective study of carbon-ion radiotherapy using Monte Carlo simulation.

We propose a two-step method to converse human tissue materials from patient computed tomography (CT) images, which is required in dose reconstructions for a retrospective study of carbon-ion radiotherapy (CIRT) using Monte Carlo (MC) simulation. The first step was to assign the standard tissues of the International Commission on Radiological Protection reference phantoms according to the CT-number. The second step was to determine the mass density of each material based on the relationship between CT-number and stopping power ratio (Hounsfield unit [HU]-SPR) registered in treatment planning system (TPS). Direct implementation of the well-calibrated HU-SPR curve allows the reproduction of previous clinical treatments recorded in TPS without uncertainty due to a mismatch of the CT scanner or scanning conditions, whereas MC simulation with realistic human tissue materials can fulfill the out-of-field dose, which was missing in the record. To validate our proposed method, depth-dose distributions in the homogenous and heterogeneous phantoms irradiated by a 400 MeV/u carbon beam with an 8 cm spread-out Bragg peak (SOBP) were computed by the MC simulation in combination with the proposed methods and compared with those of TPS. Good agreement of the depth-dose distributions between the TPS and MC simulation (within a 1% discrepancy in range) was obtained for different materials. In contrast, fluence distributions of secondary particles revealed the necessity of MC simulation using realistic human tissue. The proposed material assignment method will be used for a retrospective study using previous clinical data of CIRT at the National Institute of Radiological Sciences (NIRS).