Data Efficiency, Dimensionality Reduction, and the Generalized Symmetric Information Bottleneck.

The symmetric information bottleneck (SIB), an extension of the more familiar information bottleneck, is a dimensionality-reduction technique that simultaneously compresses two random variables to preserve information between their compressed versions. We introduce the generalized symmetric information bottleneck (GSIB), which explores different functional forms of the cost of such simultaneous reduction. We then explore the data set size requirements of such simultaneous compression. We do this by deriving bounds and root-mean-squared estimates of statistical fluctuations of the involved loss functions. We show that in typical situations, the simultaneous GSIB compression requires qualitatively less data to achieve the same errors compared to compressing variables one at a time. We suggest that this is an example of a more general principle that simultaneous compression is more data efficient than independent compression of each of the input variables.

Intraoperative iStent versus postoperative selective laser trabeculoplasty in early glaucoma patients undergoing cataract surgery: A retrospective comparative study.

PURPOSE: To compare the efficacy and safety of iStent inject® versus 360° selective laser trabeculoplasty (SLT) in patients with early glaucoma undergoing cataract surgery. METHODS: A retrospective non-randomized study was conducted in 73 eyes divided into two groups: cataract surgery+intraoperative iStent (n=40) versus cataract surgery+postoperative SLT at one month (n=33). The primary endpoint was intraocular pressure (IOP) lowering≥20% between baseline and 6 months postoperatively. The secondary endpoints were IOP lowering at 1, 6 and 12 months, and the mean number of IOP-lowering medications at 6 and 12 months. RESULTS: The mean baseline IOP was 19.1 mmHg with no significant difference between groups. The mean baseline number of IOP-lowering medications was higher in the iStent group (n=1.95) compared to the SLT group (n=1.53; P=0.04). At 6 months, 18 (60%) patients in the SLT group and 20 (51%) patients in the iStent group achieved IOP lowering≥20% with no significant difference between groups (P=0.431). At 6 months, no difference in the mean number of IOP-lowering medications was found between groups (-0.92 and -0.89 in the iStent and SLT groups, respectively). Similar results were found at 12 months. CONCLUSION: These results suggest similar safety and efficacy of intraoperative iStent and postoperative 360° SLT in lowering IOP and reducing glaucoma eye drops in early glaucoma patients undergoing cataract surgery. Treatment choice should be based on the ophthalmologist's experience and on the cost-benefit ratio.

COVID-19 pneumonia imaging follow-up: when and how? A proposition from ESTI and ESR.

This document from the European Society of Thoracic Imaging (ESTI) and the European Society of Radiology (ESR) discusses the role of imaging in the long-term follow-up of COVID-19 patients, to define which patients may benefit from imaging, and what imaging modalities and protocols should be used. Insights into imaging features encountered on computed tomography (CT) scans and potential pitfalls are discussed and possible areas for future review and research are also included. KEY POINTS: • Post-COVID-19 pneumonia changes are mainly consistent with prior organizing pneumonia and are likely to disappear within 12 months of recovery from the acute infection in the majority of patients. • At present, with the longest series of follow-up examinations reported not exceeding 12 months, the development of persistent or progressive fibrosis in at least some individuals cannot yet be excluded. • Residual ground glass opacification may be associated with persisting bronchial dilatation and distortion, and might be termed "fibrotic-like changes" probably consistent with prior organizing pneumonia.

Applicability of radiomics in interstitial lung disease associated with systemic sclerosis: proof of concept.

OBJECTIVE: To retrospectively evaluate if texture-based radiomics features are able to detect interstitial lung disease (ILD) and to distinguish between the different disease stages in patients with systemic sclerosis (SSc) in comparison with mere visual analysis of high-resolution computed tomography (HRCT). METHODS: Sixty patients (46 females, median age 56 years) with SSc who underwent HRCT of the thorax were retrospectively analyzed. Visual analysis was performed by two radiologists for the presence of ILD features. Gender, age, and pulmonary function (GAP) stage was calculated from clinical data (gender, age, pulmonary function test). Data augmentation was performed and the balanced dataset was split into a training (70%) and a testing dataset (30%). For selecting variables that allow classification of the GAP stage, single and multiple logistic regression models were fitted and compared by using the Akaike information criterion (AIC). Diagnostic accuracy was evaluated from the area under the curve (AUC) from receiver operating characteristic (ROC) analyses, and diagnostic sensitivity and specificity were calculated. RESULTS: Values for some radiomics features were significantly lower (p < 0.05) and those of other radiomics features were significantly higher (p = 0.001) in patients with GAP2 compared with those in patients with GAP1. The combination of two specific radiomics features in a multivariable model resulted in the lowest AIC of 10.73 with an AUC of 0.96, 84% sensitivity, and 99% specificity. Visual assessment of fibrosis was inferior in predicting individual GAP stages (AUC 0.86; 83% sensitivity; 74% specificity). CONCLUSION: The correlation of radiomics with GAP stage, but not with the visually defined features of ILD-HRCT, implies that radiomics might capture features indicating severity of SSc-ILD on HRCT, which are not recognized by visual analysis. KEY POINTS: • Radiomics features can predict GAP stage with a sensitivity of 84% and a specificity of almost 100%. • Extent of fibrosis on HRCT and a combined model of different visual HRCT-ILD features perform worse in predicting GAP stage. • The correlation of radiomics with GAP stage, but not with the visually defined features of ILD-HRCT, implies that radiomics might capture features on HRCT, which are not recognized by visual analysis.

Impact of Vessel Suppressed-CT on Diagnostic Accuracy in Detection of Pulmonary Metastasis and Reading Time.

RATIONALE AND OBJECTIVES: To assess if vessel suppression (VS) improves nodule detection rate, interreader agreement, and reduces reading time in oncologic chest computed tomography (CT). MATERIAL AND METHODS: One-hundred consecutive oncologic patients (65 male; median age 60y) who underwent contrast-enhanced chest CT were retrospectively included. For all exams, additional VS series (ClearRead CT, Riverrain Technologies, Miamisburg) were reconstructed. Two groups of three radiologists each with matched experience were defined. Each group evaluated the SD-CT as well as VS-CT. Each reader marked the presence, size, and position of pulmonary nodules and documented reading time. In addition, for the VS-CT the presence of false positive nodules had to be stated. Cohen's Kappa (k) was used to calculate the interreader-agreement between groups. Reading time was compared using paired t test. RESULTS: Nodule detection rate was significantly higher in VS-CT compared to the SD-CT (+21%; p <0.001). Interreader-agreement was higher in the VS-CT (k = 0.431, moderate agreement) compared to SD-CT (k = 0.209, fair agreement). Almost all VS-CT series had false positive findings (97-99 out of 100). Average reading time was significantly shorter in the VS-CT compared to the SD-CT (154 ± 134vs. 194 ± 126; 21%, p<0.001). CONCLUSIONS: Vessel suppression increases nodule detection rate, improves interreader agreement, and reduces reading time in chest CT of oncologic patients. Due to false positive results a consensus reading with the SD-CT is essential.

Radiological assessment after stereotactic body radiation of lung tumours.

The increasing use of stereotactic body radiation therapy for lung tumours comes along with new post-therapeutic imaging findings that should be known by physicians involved in patient follow-up. Radiation-induced lung injury is much more frequent than after conventional radiation therapy, it can also be delayed and has a different radiological presentation. Radiation-induced lung injury after stereotactic body radiation therapy involves the lung parenchyma surrounding the target tumour and appears as a dynamic process continuing for years after completion of the treatment. Thus, the radiological pattern and the severity of radiation-induced lung injury are prone to changes during follow-up, which can make it difficult to differentiate from local recurrence. Contrary to radiation-induced lung injury, local recurrence after stereotactic body radiation therapy is rare. Other complications mainly depend on tumour location and include airway complications, rib fractures and organizing pneumonia. The aim of this article is to provide a wide overview of radiological changes occurring after SBRT for lung tumours. Awareness of changes following stereotactic body radiation therapy should help avoiding unnecessary interventions for pseudo tumoral presentations.

Feelings, preoperative anxiety, and need for information in patients undergoing intravitreal injections.

PURPOSE: To assess feelings, preoperative anxiety, and need for information in patients undergoing intravitreal injections (IVI). METHODS: An observational cross-sectional study was conducted in our tertiary university care center between December 2017 and December 2018. Consecutive patients undergoing IVI were included. A paper survey was completed before and after IVI to assess patient experience. Preoperative anxiety and need for information were assessed using the Amsterdam Preoperative Anxiety Information Scale (APAIS) score. RESULTS: Hundred patients with a median age of 76.5 years (42-95, SD = 10.1) were included. Median best-corrected visual acuity (BCVA) in both eyes was 0.4 logMAR. Main IVI indications were wet age-related macular degeneration (n = 58), diabetic macular edema (n = 19), and venous occlusion (n = 16). The IVI most unpleasant steps were as follows: using an eyelid retractor, needle entry, changing of physician from one IVI to another, the pre-IVI waiting time, and the high number of IVI required for disease control. Preoperative anxiety (APAIS score ≥ 11) was correlated in the multivariate analysis with the need for information (p = 0.004), changing of ophthalmologist between different IVI sessions (p = 0.006), and pain expected before the IVI (p = 0.010). The need for information (APAIS score ≥ 5) was only associated with the preoperative anxiety in the multivariate analysis (p = 0.001). CONCLUSION: Preoperative anxiety and need for information are common in patients undergoing IVI even after many IVI. Being injected by different practitioners was strongly correlated with preoperative anxiety and should be avoided as much as possible. Better educational and information programs are needed.

Optimization of acquisition parameters for reduced-dose thoracic CT: A phantom study.

PURPOSE: The purpose of this study was to analyze the impact of different options for reduced-dose computed tomography (CT) on image noise and visibility of pulmonary structures in order to define the best choice of parameters when performing ultra-low dose acquisitions of the chest in clinical routine. MATERIALS AND METHODS: Using an anthropomorphic chest phantom, CT images were acquired at four defined low dose levels (computed tomography dose index [CTDIvol]=0.15, 0.20, 0.30 and 0.40mGy), by changing tube voltage, pitch factor, or rotation time and adapting tube current to reach the predefined CTDIvol-values. Images were reconstructed using two different levels of iteration (adaptive statistical iterative reconstruction [ASIR®]-v70% and ASIR®-v100%). Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) was calculated. Visibility of pulmonary structures (bronchi/vessels) were assessed by two readers on a 5-point-Likert scale. RESULTS: Best visual image assessments and CNR/SNR were obtained with high tube voltage, while lowest scores were reached with lower pitch factor followed by high tube current. Protocols favoring lower pitch factor resulted in decreased visibility of bronchi/vessels, especially in the periphery. Decreasing radiation dose from 0.40 to 0.30mGy was not associated with a significant decrease in visual scores (P<0.05), however decreasing radiation dose from 0.30mGy to 0.15mGy was associated with a lower visibility of most of the evaluated structures (P<0.001). While image noise could be significantly reduced when ASIR®-v100% instead of ASIR®-v70% was used, the visibility-scores of pulmonary structures did not change significantly. CONCLUSION: Favoring high tube voltage is the best option for reduced-dose protocols. A decrease of SNR and CNR does not necessarily go along with reduced visibility of pulmonary structures.

Nodular reverse halo sign in active pulmonary tuberculosis: A rare CT feature?

PURPOSE: The purpose of this study was to investigate the prevalence of the nodular reverse halo sign (NRHS) in chest computed tomography (CT) in patients with active pulmonary tuberculosis. MATERIALS AND METHODS: From March 2018 to March 2019, 29 consecutive patients with a culture-confirmed active pulmonary tuberculosis and who underwent chest CT examination during hospital-admission were retrospectively included in the study. There were 24 men and 5 women with a mean age of 40.9±16.7 (SD) years (range: 18-80years). Chest CT examinations of included patients were evaluated for the presence of NRHS and other tuberculosis-related CT signs. RESULTS: CT revealed the NRHS in 5 patients (5/29; 17%). The other CT signs of tuberculosis included consolidations in 18 patients (18/29; 62%), tree-in-bud pattern in 14 patients (14/29; 48%), cavitation in 12 patients (12/29; 41%), sparse nodules in 10 patients (10/29; 34%), and pleural effusion in 8 patients (8/29; 28%). CONCLUSION: CT shows NRHS in 17% of patients with active pulmonary tuberculosis, indicating that the sign is not as rare as previously thought in patients with this condition.

Testing the retroelement invasion hypothesis for the emergence of the ancestral eukaryotic cell.

Phylogenetic evidence suggests that the invasion and proliferation of retroelements, selfish mobile genetic elements that copy and paste themselves within a host genome, was one of the early evolutionary events in the emergence of eukaryotes. Here we test the effects of this event by determining the pressures retroelements exert on simple genomes. We transferred two retroelements, human LINE-1 and the bacterial group II intron Ll.LtrB, into bacteria, and find that both are functional and detrimental to growth. We find, surprisingly, that retroelement lethality and proliferation are enhanced by the ability to perform eukaryotic-like nonhomologous end-joining (NHEJ) DNA repair. We show that the only stable evolutionary consequence in simple cells is maintenance of retroelements in low numbers, suggesting how retrotransposition rates and costs in early eukaryotes could have been constrained to allow proliferation. Our results suggest that the interplay between NHEJ and retroelements may have played a fundamental and previously unappreciated role in facilitating the proliferation of retroelements, elements of which became the ancestors of the spliceosome components in eukaryotes.

Stochastic Turing patterns in a synthetic bacterial population.

The origin of biological morphology and form is one of the deepest problems in science, underlying our understanding of development and the functioning of living systems. In 1952, Alan Turing showed that chemical morphogenesis could arise from a linear instability of a spatially uniform state, giving rise to periodic pattern formation in reaction-diffusion systems but only those with a rapidly diffusing inhibitor and a slowly diffusing activator. These conditions are disappointingly hard to achieve in nature, and the role of Turing instabilities in biological pattern formation has been called into question. Recently, the theory was extended to include noisy activator-inhibitor birth and death processes. Surprisingly, this stochastic Turing theory predicts the existence of patterns over a wide range of parameters, in particular with no severe requirement on the ratio of activator-inhibitor diffusion coefficients. To explore whether this mechanism is viable in practice, we have genetically engineered a synthetic bacterial population in which the signaling molecules form a stochastic activator-inhibitor system. The synthetic pattern-forming gene circuit destabilizes an initially homogenous lawn of genetically engineered bacteria, producing disordered patterns with tunable features on a spatial scale much larger than that of a single cell. Spatial correlations of the experimental patterns agree quantitatively with the signature predicted by theory. These results show that Turing-type pattern-forming mechanisms, if driven by stochasticity, can potentially underlie a broad range of biological patterns. These findings provide the groundwork for a unified picture of biological morphogenesis, arising from a combination of stochastic gene expression and dynamical instabilities.

Correction to: Volumetric dynamic oxygen-enhanced MRI (OE-MRI): comparison with CT Brody score and lung function in cystic fibrosis patients.

The original version of this article, published on 13 April 2018, unfortunately contained a mistake.

Volumetric dynamic oxygen-enhanced MRI (OE-MRI): comparison with CT Brody score and lung function in cystic fibrosis patients.

OBJECTIVES: To demonstrate, in patients with cystic fibrosis (CF), the correlation between three-dimensional dynamic oxygen-enhanced magnetic resonance imaging (OE-MRI) measurements and computed tomography Brody score (CF-CT) and lung function testing (LFT). METHODS: Twenty-one patients (median age, 25 years; female, n = 8) with a range of CF lung disease and five healthy volunteers (median age, 31 years; female, n = 2) underwent OE-MRI performed on a 1.5-T MRI scanner. Coronal volumes were acquired while patients alternately breathed room air and 100% oxygen. Pre-oxygen T1 was measured. Dynamic series of T1-weighted volumes were then obtained while breathing oxygen. T1-parameter maps were generated and the following OE-MRI parameters were measured: oxygen uptake (ΔPO2max), wash-in time and wash-out time. High-resolution CT and LFT were performed. The relationship between CF-CT, LFT and OE-MRI parameters were evaluated using Pearson correlation for the whole lung and regionally. RESULTS: Mean CF-CT was 24.1±17.1. Mean ΔPO2max and mean wash-in as well as skewness of wash-out showed significant correlation with CF-CT (ΔPO2max: r = -0.741, p < 0.001; mean wash-in: r = 0.501, p = 0.017; skewness of wash-out: r = 0.597, p = 0.001). There was significant correlation for the whole lung and regionally between LFT parameters and OE-MR (ΔPO2max: r = 0.718, p < 0.001; wash-in: r = -0.576, p = 0.003; wash-out skewness: r = -0.552, p = 0.004). CONCLUSIONS: Functional lung imaging using OE-MRI has the capability to assess the severity of CF lung disease and shows a significant correlation with LFT and CF-CT. KEY POINTS: • Oxygen-enhanced MRI might play a future role in evaluation and follow-up of cystic fibrosis. • Heterogeneity of parameter maps reflects localised functional impairment in cystic fibrosis. • Avoidance of cumulative radiation burden in CF is feasible using OE-MRI.

Postoperative imaging of orthopaedic hardware in the hand and wrist: is there an added value for tomosynthesis?

AIM: To prospectively investigate digital tomosynthesis (DTS) as an alternative to digital radiography (DR) for postoperative imaging of orthopaedic hardware after trauma or arthrodesis in the hand and wrist. MATERIALS AND METHODS: Thirty-six consecutive patients (12 female, median age 36 years, range 19-86 years) were included in this institutional review board approved clinical trial. Imaging was performed with DTS in dorso-palmar projection and DR was performed in dorso-palmar, lateral, and oblique views. Images were evaluated by two independent radiologists for qualitative and diagnosis-related imaging parameters using a four-point Likert scale (1=excellent, 4not diagnostic) and nominal scale. Interobserver agreement between the two readers was assessed with Cohen's kappa (k). Differences between DTS and CR were tested with Wilcoxon's signed-rank test. A p-value <0.05 was considered statistically significant. RESULTS: Regarding image quality, interobserver agreement was higher for DTS compared to DR, especially for fracture-related parameters (delineation osteosynthesis material [OSM]: KDTS0.96 versus KDR0.45; delineation fracture margins: KDTS0.78 versus KDR0.35). Delineation of fracture margins and delineation of adjacent joint spaces scored significant better for DTS compared to DR (delineation fracture margins: DTS1.54, DR2.28, p0.001; delineation adjacent joint spaces: DTS1.31, DR2.24, p0.001). Regarding diagnosis-related findings, interobserver agreement was almost equal. DTS showed a significant higher sharpness of fracture margins (DTS1.94, DR2.33, p0.04). Mean dose area product (DAP) for DTS was significant higher compared to DR (mean DR0.219 Gy·cm2, mean DTS0.903 Gy·cm2, p0.001). CONCLUSION: Fracture healing is more visible and interobserver agreement is higher for DTS compared to DR in the postoperative assessment of orthopaedic hardware in the hand and wrist.

Model for screened, charge-regulated electrostatics of an eye lens protein: Bovine gammaB-crystallin.

We model screened, site-specific charge regulation of the eye lens protein bovine gammaB-crystallin (γB) and study the probability distributions of its proton occupancy patterns. Using a simplified dielectric model, we solve the linearized Poisson-Boltzmann equation to calculate a 54×54 work-of-charging matrix, each entry being the modeled voltage at a given titratable site, due to an elementary charge at another site. The matrix quantifies interactions within patches of sites, including γB charge pairs. We model intrinsic pK values that would occur hypothetically in the absence of other charges, with use of experimental data on the dependence of pK values on aqueous solution conditions, the dielectric model, and literature values. We use Monte Carlo simulations to calculate a model grand-canonical partition function that incorporates both the work-of-charging and the intrinsic pK values for isolated γB molecules and we calculate the probabilities of leading proton occupancy configurations, for 4

Easy Pulsatile Phantom for Teaching and Validation of Flow Measurements in Ultrasound.

PURPOSE: To build a simple model to teach and validate non-pulsatile and pulsatile flow quantification in ultrasound. MATERIALS AND METHODS: The setting consists of the following connected components: (1) medical syringe pump producing an adjustable constant flow (ml/min), (2) modulator modifying constant flow to a reproducible pulsatile flow, (3) water tank containing a diagonal running silicone tube (0.5 mm inner diameter), and (4) a fixated ultrasound probe (L9 Linear Array 9 MHz, GE Logiq E9) measuring the flow inside the tube. Commercially available microbubbles suspended with physiological saline solution were used for ultrasonic visibility. Spectral Doppler of different flow profiles is performed. RESULTS: The syringe pump produces an adjustable, constant flow and serves as the reference standard. The filling volume of the tube system is 1.2 ml. Microbubbles are very well detected by ultrasound and can be used as an easy and clean blood mimicking substance. The modulator generates different physiological and pathological flow profiles. Velocities are similar to those found within human blood vessels. Thus, it is possible to train and validate flow measurements in ultrasound. CONCLUSION: The model produces non-pulsatile and various pulsatile flow profiles and allows validation of flow measurements. The compact size permits easy and economic setup for flow measurements in research, skills lab and continuing education.

Prospective Randomized Comparison of High-pitch CT at 80 kVp Under Free Breathing with Standard-pitch CT at 100 kVp Under Breath-Hold for Detection of Pulmonary Embolism.

RATIONALE AND OBJECTIVES: To prospectively compare high-pitch computed tomography (HPCT) under free breathing (FB) with standard-pitch CT (SPCT) under breath-hold (BH) for detection of pulmonary embolism (PE). MATERIALS AND METHODS: One hundred consecutive patients (47 females; mean age 58.7 ± 16.6) randomly underwent HPCT-FB (n = 50) or SPCT-BH (n = 50). Radiation doses were documented. One reader measured pulmonary artery attenuation and noise; mean signal-to-noise ratio (SNR) was calculated. Two readers assessed image quality, diagnostic confidence for detection of PE, motion artifacts, assessability of anatomical structures, and presence of transient interruption of contrast as sign of Valsalva maneuver. Inter-reader agreement was calculated. RESULTS: Radiation dose was significantly lower in HPCT compared to SPCT (2.68 ± 0.60 mGy vs 6.01 ± 2.26 mGy; P < .001). Mean pulmonary artery attenuation and image noise were significantly higher in HPCT (attenuation: 479 Hounsfield unit (HU) vs 343HU; P < .001; noise: 16 HU vs 10 HU; P < .001) whereas SNR was similar between groups (34 HU vs 38 HU; P = .258). HPCT had significantly higher diagnostic confidence for PE detection (P = .048), less cardiac and breathing artifacts (P < .001), better assessability of anatomical structures, and fewer cases of transient interruption of contrast (P < .001) compared to the SPCT. CONCLUSIONS: HPCT-FB allows for a significant reduction of breathing and motion artifacts compared to SPCT-BH. Diagnostic confidence, assessability of vascular and bronchial structures, as well as SNR are maintained.

Real-time transposable element activity in individual live cells.

The excision and reintegration of transposable elements (TEs) restructure their host genomes, generating cellular diversity involved in evolution, development, and the etiology of human diseases. Our current knowledge of TE behavior primarily results from bulk techniques that generate time and cell ensemble averages, but cannot capture cell-to-cell variation or local environmental and temporal variability. We have developed an experimental system based on the bacterial TE IS608 that uses fluorescent reporters to directly observe single TE excision events in individual cells in real time. We find that TE activity depends upon the TE's orientation in the genome and the amount of transposase protein in the cell. We also find that TE activity is highly variable throughout the lifetime of the cell. Upon entering stationary phase, TE activity increases in cells hereditarily predisposed to TE activity. These direct observations demonstrate that real-time live-cell imaging of evolution at the molecular and individual event level is a powerful tool for the exploration of genome plasticity in stressed cells.