Standardisation of conventional and advanced iterative reconstruction methods for Gallium-68 multi-centre PET-CT trials

Purpose To assess the applicability of the Fluorine-18 performance specifications defined by EANM Research Ltd (EARL), in Gallium-68 multi-centre PET-CT trials using conventional (ordered subset expectation maximisation, OSEM) and advanced iterative reconstructions which include the systems’ point spread function (PSF) and a Bayesian penalised likelihood algorithm (BPL) commercially known as Q.CLEAR. The possibility of standardising the two advanced reconstruction methods was examined. Methods The NEMA image quality phantom was filled with Gallium-68 and scanned on a GE PET-CT system. PSF and BPL with varying post-reconstruction Gaussian filter width (2–6.4 mm) and penalisation factor (200–1200), respectively, were applied. The average peak-to-valley ratio from six profiles across each sphere was estimated to inspect any edge artefacts. Image noise was assessed using background variability and image roughness. Six GE and Siemens PET-CT scanners provided Gallium-68 images of the NEMA phantom using both conventional and advanced reconstructions from which the maximum, mean and peak recoveries were drawn. Fourteen patients underwent 68Ga-PSMA PET-CT imaging. BPL (200-1200) reconstructions of the data were compared against PSF smoothed with a 6.4-mm Gaussian filter. Results A Gaussian filter width of approximately 6 mm for PSF and a penalisation factor of 800 for BPL were needed to suppress the edge artefacts. In addition, those reconstructions provided the closest agreement between the two advanced iterative reconstructions and low noise levels with the background variability and the image roughness being lower than 7.5% and 11.5%, respectively. The recoveries for all methods generally performed at the lower limits of the EARL specifications, especially for the 13- and 10-mm spheres for which up to 27% (conventional) and 41% (advanced reconstructions) lower limits are suggested. The lesion standardised uptake values from the clinical data were significantly different between BPL and PSF smoothed with a Gaussian filter of 6.4 mm wide for all penalisation factors except for 800 and 1000. Conclusion It is possible to standardise the advanced reconstruction methods with the reconstruction parameters being also sufficient for minimising the edge artefacts and noise in the images. For both conventional and advanced reconstructions, Gallium-68 specific recovery coefficient limits were required, especially for the smallest phantom spheres.

Argumentation of filter width selection with the use of envelope spectrum in vibration diagnostics of rotary machine defects

The paper shows certain ambiguity of the narrow-band boundary of random processes obtained by different authors. The use of filters of different widths in obtaining the envelope spectrum makes it difficult to compare the obtained results by estimating the depth of amplitude modulation in vibration diagnostics of defects in rotary machines. We studied the results of bandpass filtering of the noise process only, as well as of amplitude-modulated noise. The analysis of the results of filtering of a broadband normal random process with constant spectral density and the representation of the spectrum width of the resulting oscillations through spectral moments showed that processes selected by a filter of no more than 1/3 octave bandwidth should be considered narrowband. Simulation of the amplitude of a broadband noise by the harmonic process and estimating the dependence of the modulating harmonic amplitude, the depth of amplitude modulation, skewness and kurtosis, as well as envelope characteristics on the width of the selecting filter allowed us to establish that a relative filter width of 30% should be applied when the envelope spectrum is used.

An uncertainty principle for star formation – III. The characteristic emission time-scales of star formation rate tracers

ABSTRACT We recently presented a new statistical method to constrain the physics of star formation and feedback on the cloud scale by reconstructing the underlying evolutionary timeline. However, by itself this new method only recovers the relative durations of different evolutionary phases. To enable observational applications, it therefore requires knowledge of an absolute ‘reference time-scale’ to convert relative time-scales into absolute values. The logical choice for this reference time-scale is the duration over which the star formation rate (SFR) tracer is visible because it can be characterized using stellar population synthesis (SPS) models. In this paper, we calibrate this reference time-scale using synthetic emission maps of several SFR tracers, generated by combining the output from a hydrodynamical disc galaxy simulation with the SPS model slug2. We apply our statistical method to obtain self-consistent measurements of each tracer’s reference time-scale. These include H α and 12 ultraviolet (UV) filters (from GALEX, Swift, and HST), which cover a wavelength range 150–350 nm. At solar metallicity, the measured reference time-scales of H α are ${4.32^{+0.09}_{-0.23}}$ Myr with continuum subtraction, and 6–16 Myr without, where the time-scale increases with filter width. For the UV filters we find 17–33 Myr, nearly monotonically increasing with wavelength. The characteristic time-scale decreases towards higher metallicities, as well as to lower star formation rate surface densities, owing to stellar initial mass function sampling effects. We provide fitting functions for the reference time-scale as a function of metallicity, filter width, or wavelength, to enable observational applications of our statistical method across a wide variety of galaxies.

Minimal and mild hearing loss in children: Association with auditory perception, cognition, and communication problems

ABSTRACTObjectives‘Minimal’ and ‘mild’ hearing loss are the most common but least understood forms of hearing loss in children. Children with better ear hearing level as low as 30 dB HL have a global language impairment and, according to the World Health Organization, a “disabling level of hearing loss”. We examined in a population of 6 - 11 year olds how hearing level ≤ 40.0 dB HL (1 and 4 kHz pure tone average, PTA, threshold) related to auditory perception, cognition and communication.DesignSchool children (n=1638) were recruited in four centres across the UK. They completed a battery of hearing (audiometry, filter width, temporal envelope, speech-in-noise) and cognitive (IQ, attention, verbal memory, receptive language, reading) tests. Caregivers assessed their children’s communication and listening skills. Children included in this study (702 male; 752 female) had four reliable tone thresholds (1, 4 kHz each ear), and no caregiver reported medical or intellectual disorder. Normal hearing children (n=1124, 77.1%) had all four thresholds and PTA < 15 dB HL. Children with ≥ 15 dB HL for at least one threshold, and PTA < 20 dB (n=245, 16.8%) had Minimal hearing loss. Children with 20 ≤ PTA < 40 dB HL (n=88, 6.0%) had Mild hearing loss. Interaural Asymmetric hearing loss (|Left PTA – Right PTA| ≥ 10 dB) was found in 28.9% of those with Minimal and 39.8% of those with Mild hearing loss.ResultsSpeech perception in noise, indexed by VCV pseudoword repetition in speech modulated noise, was impaired in children with Minimal and Mild hearing loss, relative to Normal hearing children. Effect size was largest (d=0.63) in Asymmetric Mild hearing loss and smallest (d=0.21) in Symmetric Minimal hearing loss. Spectral (filter width) and temporal (backward masking) perception were impaired in children with both forms of hearing loss, but supra-threshold perception generally related only weakly to PTA. Speech-in-noise (nonsense syllables) and language (pseudoword repetition) were also impaired in both forms of hearing loss and correlated more strongly with PTA. Children with Mild hearing loss were additionally impaired in working memory (digit span) and reading, and generally performed more poorly than those with Minimal loss. Asymmetric hearing loss produced as much impairment overall on both auditory and cognitive tasks as Symmetric hearing loss. Nonverbal IQ, attention and caregiver-rated listening and communication were not significantly impaired in children with hearing loss. Modelling suggested that 15 dB HL is objectively an appropriate lower audibility limit for diagnosis of hearing loss.ConclusionsHearing loss between 15 - 30 dB PTA is, at ~20%, much more prevalent in 6-11 y.o. children than most current estimates. Key aspects of auditory and cognitive skills are impaired in both symmetric and asymmetric minimal and mild hearing loss. Hearing loss < 30 dB HL is most closely related to speech perception in noise, and to cognitive abilities underpinning language and reading. The results suggest wider use of speech-in-noise measures to diagnose and assess management of hearing loss and reduction of the clinical hearing loss threshold for children to 15 dB HL.

Efficient CNN for Lung Cancer Detection

The machine learning based solutions for medical image analysis are successful in detection of wide variety of anomalies in imaging procedures. The aim of the medical image analysis systems based on machine learning methods is to improve the accuracy and minimize the detection time. The aim in turn contributes to early disease detection and extending the patient life. This paper presents an efficient CNN (EFFI-CNN) for Lung cancer detection. EFFI-CNN consists of seven CNN layers (i.e. Convolution layer, Max-Pool layer, Convolution layer, Max-Pool layer, fully connected layer, fully connected layer and Soft-Max layer). EFFI-CNN uses lung CT scan images from LIDC-IDRI and Mendeley data sets. EFFI-CNN has a unique combination of CNN layers with parameters (Depth, Height, Width, filter Height and filter width).

LES and Hybrid RANS-LES Simulation of a Pulsating Channel Flow

Simulation of turbulent boundary layers for flows characterized by unsteady driving conditions is important for solving complicated engineering problems such as combustion, blood flow in stenosed arteries, and flow over immersed structures. These flows are often dominated by complex vortical structures, regions of varying turbulence intensities, and fluctuating pressure fields. Pulsating channel flow is one such case that presents a unique set of challenges for newly developed and existing turbulence models used in computational fluid dynamics (CFD) solvers. In the present study, performance of the dynamic hybrid RANS-LES model (DHRL) with exponential time averaging (ETA) is evaluated against Monotonically Integrated Large Eddy Simulation (MILES) and a previously documented LES study for a fully developed channel flow with a time-periodic driving pressure gradient. Results indicate that MILES over predicts mean streamwise velocity for all forcing frequencies while the DHRL model with ETA provides a method for improved results, especially for the lower frequencies. It is concluded that a hybrid RANS-LES model with ETA is a useful alternative to simulate unsteady non-stationary flows but further work is needed to determine the appropriate filter width for ETA to significantly improve the predictive capabilities of the DHRL model.

Effectiveness of Contour Farming and Filter Strips on Ecosystem Services

The failing ecosystem services in Thika-Chania catchment is manifested in the deterioration of water quality, sedimentation of reservoirs, and subsequent increase in water treatment costs due to high turbidity. The services can be restored by implementing relevant soil and water conservation practices to enhance flow regulation and control sediment yield. The impacts of contour farming and filter strips on water and sediment yield were evaluated using Soil Water and Assessment Tool (SWAT), Texas A&M University, USA. Sediment calibration and validation was achieved using data obtained from a bathymetric survey. Model parameters were adjusted to simulate the conservation impacts of contour farming and filter strips. Results indicated the average annual sediment yield as 22 t/ha at the outlet of the catchment and average annual surface runoff of 202 mm. The simulation results showed that filter strips of 5 m width would reduce the average annual sediment yield from the catchment by 54%. The efficacy of filter strips in reducing sediment yield was observed to increase with increasing filter width. Three-meter filter strips and contour farming reduced the average annual sediment yield at catchment outlet by 46% and 36%, respectively. It was concluded that the implementation of contour farming and filters strips reduced sediments by 63% from the base value. Water yield at the sub-basin level was only influenced by contour farming. The total water yield at the catchment outlet experienced no significant change.

Filtered Optical Feedback in Quantum Dot Light Emitting Diode

This research reports a theoretical investigation on the role of filtered optical feedback (FOF) in the quantum dot light emitting diode (QD-LED). The underlying dynamics is affected by a sidle node, which returns to an elliptical shape when the wetting layer (WL) is neglected. Both filter width and time delay change the appearance of different dynamics (chaotic and mixed mode oscillations ,MMOs). The results agrees with the experimental observations. Here, the fixed point analysis for QDs was done for the first time. For QD-LED with FOF, the system transits from the coherence collapse (CC) case in conventional optical feedback (COF) to a coherent case with a filtered mode in FOF. It was found that the WL washes out the modes which is an unexpected result. This may attributed to the longer capture time of WL compared with that between QD states. Thus, WL reduces the chaotic behavior.