Radiomics strategies for risk assessment of tumour failure in head-and-neck cancer

Quantitative extraction of high-dimensional mineable data from medical images is a process known as radiomics. Radiomics is foreseen as an essential prognostic tool for cancer risk assessment and the quantification of intratumoural heterogeneity. In this work, 1615 radiomic features (quantifying tumour image intensity, shape, texture) extracted from pre-treatment FDG-PET and CT images of 300 patients from four different cohorts were analyzed for the risk assessment of locoregional recurrences (LR) and distant metastases (DM) in head-and-neck cancer. Prediction models combining radiomic and clinical variables were constructed via random forests and imbalance-adjustment strategies using two of the four cohorts. Independent validation of the prediction and prognostic performance of the models was carried out on the other two cohorts (LR: AUC = 0.69 and CI = 0.67; DM: AUC = 0.86 and CI = 0.88). Furthermore, the results obtained via Kaplan-Meier analysis demonstrated the potential of radiomics for assessing the risk of specific tumour outcomes using multiple stratification groups. This could have important clinical impact, notably by allowing for a better personalization of chemo-radiation treatments for head-and-neck cancer patients from different risk groups.Comment: (1) Paper: 33 pages, 4 figures, 1 table; (2) SUPP info: 41 pages, 7 figures, 8 table

Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics

International audienceThe frequency range of the WHISPER relaxation sounder instrument on board CLUSTER, 4–80 kHz, has been chosen so as to encompass the electron gyro-frequency, F ce , and the electron plasma frequency, F p , in most regions to be explored. Measurement of those frequencies, which are triggered as resonances by the sounder, provides a direct estimation of in situ fundamental plasma characteristics: electron density and magnetic field intensity. In the late mission phase, CLUSTER penetrated regions deep inside the plas-masphere where F ce and F p are much higher than the upper frequency of the sounder's range. However, they are of the right order of magnitude as to place the lower hybrid frequency , F lh , in the 4–15 kHz band. This characteristic frequency , placed at a resonance of the medium, is triggered by the sounder's transmitter and shows up as an isolated peak in the received spectrum, not present in spectra of naturally occuring VLF waves. This paper illustrates, from analysis of case events, how measured F lh values give access to a plasma diagnostic novel of its kind. CLUSTER, travelling along its orbit, encounters favourable conditions where F ce is increasing and F p decreasing, such that F ce /F p increases from values below unity to values above unity. Measured F lh values thus give access, in turn, to the effective mass, M eff , indicative of plasma ion composition, and to the core plasma-sphere electron density value, a parameter difficult to measure. The analysed case events indicate that the estimated quantities (M eff in the 1.0–1.4 range, N e in the 5 × 10 2 – 10 4 cm −3 range) are varying with external factors (altitude, L value, geomagnetic activity) in a plausible way. Although covering only a restricted region (mid-latitude, low altitude inner plasmasphere), these measurements are available, since Correspondence to: S. Kougblénou ([email protected]) late 2009, for all CLUSTER perigee passes not affected by eclipses (on average, roughly a third of a total of ∼200 passes per year) and offer multipoint observations previously unavailable in this region

Federated learning enables big data for rare cancer boundary detection.

Although machine learning (ML) has shown promise across disciplines, out-of-sample generalizability is concerning. This is currently addressed by sharing multi-site data, but such centralization is challenging/infeasible to scale due to various limitations. Federated ML (FL) provides an alternative paradigm for accurate and generalizable ML, by only sharing numerical model updates. Here we present the largest FL study to-date, involving data from 71 sites across 6 continents, to generate an automatic tumor boundary detector for the rare disease of glioblastoma, reporting the largest such dataset in the literature (n = 6, 314). We demonstrate a 33% delineation improvement for the surgically targetable tumor, and 23% for the complete tumor extent, over a publicly trained model. We anticipate our study to: 1) enable more healthcare studies informed by large diverse data, ensuring meaningful results for rare diseases and underrepresented populations, 2) facilitate further analyses for glioblastoma by releasing our consensus model, and 3) demonstrate the FL effectiveness at such scale and task-complexity as a paradigm shift for multi-site collaborations, alleviating the need for data-sharing

Author Correction: Federated learning enables big data for rare cancer boundary detection.

10.1038/s41467-023-36188-7NATURE COMMUNICATIONS14

Federated Learning Enables Big Data for Rare Cancer Boundary Detection

Although machine learning (ML) has shown promise across disciplines, out-of-sample generalizability is concerning. This is currently addressed by sharing multi-site data, but such centralization is challenging/infeasible to scale due to various limitations. Federated ML (FL) provides an alternative paradigm for accurate and generalizable ML, by only sharing numerical model updates. Here we present the largest FL study to-date, involving data from 71 sites across 6 continents, to generate an automatic tumor boundary detector for the rare disease of glioblastoma, reporting the largest such dataset in the literature (n = 6, 314). We demonstrate a 33% delineation improvement for the surgically targetable tumor, and 23% for the complete tumor extent, over a publicly trained model. We anticipate our study to: 1) enable more healthcare studies informed by large diverse data, ensuring meaningful results for rare diseases and underrepresented populations, 2) facilitate further analyses for glioblastoma by releasing our consensus model, and 3) demonstrate the FL effectiveness at such scale and task-complexity as a paradigm shift for multi-site collaborations, alleviating the need for data-sharing

Les échelles de la turbulence dans l'ionosphère des hautes latitudes et leurs signatures sur les échos des radars HF du réseau SuperDARN

SuperDARN is a coherent HF radar network dedicated to the study of high-latitude ionospheric plasma convection and finds its major applications in the field of Sun/Earth connection. This work deals with the interactions between a transmitted radar wave and ionisation gradients at different scales and their impact on measurements. Studies are performed in order to detect the ion cyclotron signature, superimposed to turbulent motions, in observed spectra. On the other hand, the role of intermediate scales (from hundreds of meters to kilometers) on spectral width estimation is evidenced. Statistical studies show that the value of this parameter depends upon transmitted frequency and echo range. We propose an interpretation in terms of a wave front decorrelation during propagation and validate it with numerical simulations based upon realistic ionospheric parameters.SuperDARN est un réseau de radars HF cohérents dédié à l'étude de la convection du plasma ionosphérique à haute latitude qui trouve ses principales applications dans l'étude des relations Soleil/Terre. On s'intéresse ici aux effets des interactions entre l'onde radar émise et les gradients d'ionisation de différentes échelles et à leur impact sur la mesure. Des études sont menées pour détecter la signature du mouvement cyclotron des ions, superposé aux mouvements turbulents, dans les spectres mesurés. Ensuite, l'effet des moyennes échelles (100 m à 10 km) est mis en évidence sur la mesure des largeurs spectrales. Des études statistiques montrent que la détermination des paramètres est affectée par le rapport entre la fréquence émise et la fréquence plasma et par la distance de l'écho. Nous proposons une interprétation en terme de décorrélation du front d'onde au cours de la propagation, validée par la mise en place de simulations s'appuyant sur des paramètres réalistes de l'ionosphère

Study of nonthermal continuum patches : wave propagation and plasmapause study

Nonthermal continuum (NTC) radiation is believed to be emitted at the plasmapause and near the magnetic equator. We present a particular type of NTC radiation, referred to as NTC patch, which appears over a wide frequency range and within a relatively short time interval. NTC patches are observed in all magnetospheric plasma environments of the Cluster 2 orbit and are shown to represent a quarter of the NTC events observed in 2003. A statistical analysis of the frequency pattern performed on the 2003 Cluster 2 Waves of High frequency and Sounder for Probing of Electron Density by Relaxation data indicates that the NTC patches can be divided into two classes: Those with banded emission in frequency are only observed close to the source region and are thus termed "plasmaspheric," while the others, nonbanded, are termed "outer magnetospheric." In an event on 26 September 2003, we localize the sources positions and study the expected propagation of each NTC frequency beam of a plasmaspheric patch. From the observations, we show that the sources are located very close to the satellite and to each other at positions projected on the XY GSE plane. Using a ray tracing code, we demonstrate that, close to the source regions, the satellite observes all frequency rays at the same time which overlap in the spectrogram making up the plasmaspheric patch. After the satellite crossing, the rays follow diverging paths and cannot therefore be observed further out by the same satellite simultaneously. Plasmaspheric patches are thus specific signatures of close and distorted source regions

Determination of the Noise Floor of the WHISPER instrument on Cluster

International audienceThe WHISPER (Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation) instrument is part of the WEC (Wave Experiment Consortium) of the ongoing Cluster mission, launched almost 20 years ago in 2000. It uses the long double sphere electric dipole antennas of the EFW (Electric Field and Wave) instrument to measure the electric field spectra in the frequency range 2-80 kHz. The characteristic signatures of natural or actively triggered waves indicate the nature of the ambient plasma regime and, combined with the spacecraft position, reveals the position of key magnetospheric boundaries encountered during a specific time interval.Most of the time, WHISPER observes natural waves in the 2-80 kHz band, using one of the two EFW antennae pairs: Ey or Ez, which can have different characteristics. After successive technical problems with the EFW sensors, the receiving antenna had to be changed on 3 of the 4 spacecraft over the years, and Cluster 1 (C1) WHISPER measurements are currently being made with only one probe (the spacecraft acts as the second probe).In order to understand the signals observed by the WHISPER experiment, one needs to know the instrumental noise floor, around which the measurements are meaningless. It is a frequent feature of wave detectors that this noise floor is temporally static - it does not degrade with time. However, what this noise floor actually is, and how its behaviour changes around the failure of probes and switching to other probes is the purpose of this study. The NATURAL spectra were processed orbit by orbit, in order to avoid strong emissions from any one region, then the minimum value for the low-energy spectra was picked out for each frequency. Individually, these show a large amount of variation, but the median of 20 orbits gives a very reproducible curve showing how the noise floor varies with frequency. The periods before, during and after probe failures and configuration changes were investigated and show the limited changes to the curves and strength of interference lines

Plasma characterization at comet 67P between 2 and 4 AU from the Sun with the RPC-MIP instrument

International audienceThe plasma of comet 67P/Churyumov Gerasimenko is analyzed based on the RPC-MIP mutual impedance probe data of the Rosetta mission. Numerical simulations of the RPC-MIP instrumental response considering two populations of electrons were t on experimental responses acquired from January to September 2016 to extract the electron densities and temperatures. A time-tracking of the plasma parameters was performed, leading to the identi cation of a cold and a warm population of electrons during the period of interest. The respective densities and temperatures lie in the ranges [100 ; 1000] cm−3 and [0.05 ; 0.3] eV for the cold electrons and in the ranges [50 ; 500] cm−3 and [2 ; 10] eV for the warm electrons. Warm electrons most of the time made up between 10% and 30% of the whole population, while the temperature ratio between warm and cold electrons lay mostly between 30 and 70 during the period we studied. The uctuation range of the plasma parameters, that is, the electron densities and temperatures, appears to have remained rather constant during the last nine months of the mission. We take the limitations of the instrument that are due to the experimental noise into account in our discussion of the results

Medium-latitude sources of plasmaspheric nonthermal continuum radiations observed close to harmonics of the electron gyrofrequency

International audienceNonthermal continuum (NTC) radiation is, with auroral kilometric radiation (AKR), one of the two electromagnetic emissions generated within the Earth's magnetosphere and radiated into space. It is generally believed that NTC is emitted in the plasmapause density gradient after conversion of intense electrostatic waves, present near the magnetic equator, into electromagnetic waves. In this paper, we present a specific type of NTC event, of infrequent occurrence, displaying a finger-like pattern not yet reported: banded emissions peaking at exact multiples of a common frequency, df, which decrease inbound toward the plasmapause boundary layer (PPBL). Analysis is presented that indicates that the corresponding sources are nearby sites of the PPBL where the local electron gyrofrequency f(ce) equals df. The sources are radiating beams of limited cone angle size. The NTC sources for this event are shown to be located at about 20 degrees magnetic latitude. This illustrates that the PPBL is active in radiating NTC waves not only near the magnetic equator but also up to the medium-latitude range