Radial Spread Research Articles

What Is the Optimal Radiation Technique for Esophageal Cancer? A Dosimetric Comparison of Four Techniques.

BackgroundEsophageal cancer treatment requires large radiation fields due to the deep location of the esophagus in the mediastinum and the high incidence of radial spread. There is no optimal radiation technique to ensure appropriate target coverage and minimal dose to all normal structures.MethodsFifteen consecutive cases of locally advanced esophageal cancer treated with radical chemoradiation (CRT) were analyzed. The total prescribed dose was 50.4 Gy in 28 fractions. A total of 60 plans were generated for analysis, including four different methods for each case. Method 1 consisted of a four-field conformal technique; method 2 was a two-plan technique (antero-posterior (AP), postero-anterior (PA), two posterior oblique fields (RPO and LPO)); method 3 was a three-field conformal technique (AP, LPO, RPO); and method 4 was a volumetric modulated arc radiotherapy (VMAT) technique. Dose ratios were calculated using the minimum, maximum, mean, and median doses of methods 2-4 over the dose of method 1. Ratios for the planning target volume (PTV) and to surrounding organs were analyzed.ResultsThe mean PTV dose ratio ranged from 0.994 to 1.048 (SD = 0.01) representing an adequate target coverage for all techniques based on an analysis of variance (ANOVA). For the lungs, method 2 had the lowest lung V20 with a ratio of 0.861 (SD = 0.12), whereas method 3 had the highest with 1.644 (SD = 0.14). For the heart, method 3 had the lowest heart V40 with a mean dose ratio of 0.807 (SD = 0.09), whereas method 2 had the highest with 1.160 (SD = 0.11). For the liver, method 2 had the lowest V30 with a mean ratio of 0.857 (SD = 0.1) whereas method 4 had the highest with 1.672 (SD = 0.48). For the spinal cord, method 3 had the lowest mean dose ratio of 0.559 (SD = 0.09) whereas method 2 had the highest with 1.094 (SD = 0.04).ConclusionThe four radiation techniques for esophageal cancer treatment were appropriate for target coverage. Method 2 had the most organ-sparing effect for the lungs and liver, and method 3 for the heart and spinal cord. VMAT did not add any significant sparing. A case-by-case decision should be made based on the patient’s comorbidities.

A study of the spatial and temporal evolution of auto-ignition kernels using time-resolved tomographic OH-LIF

In this paper, the spatial and temporal evolution of auto-ignition kernels from methane jets propagating into a NOx-vitiated, high-turbulence, hot air co-flow was studied by means of time-resolved tomographic laser-induced fluorescence of OH (Tomo OH-LIF). Measurements were performed using a burst dye laser system at 10 kHz for volumetric laser illumination and a multi-camera arrangement (8-views) for detection of the fluorescence signal. Auto-ignition kernels were detected three-dimensionally and tracked using a robust algorithm based on the intensity gradient of the volumetrically reconstructed signals. The size and location of the detected kernels were evaluated for operating conditions with different Reynolds numbers of the fuel jet. Results showed that auto-ignition randomly occurred with high probability in a well defined fairly axisymmetric radial region with strong fluctuations in the main direction of the flow. The increase of the Reynolds number of the fuel jet resulted in a radial spread of the location of auto-ignition events. The statistical evaluation of the orientation and growth of auto-ignition kernels with respect to the mean flow field showed that the kernels were oriented tangentially to the flow and temporally evolve towards this preferential direction as the ignition events progressed.

Spatial orientation of coronary arteries and its implication for breast and thoracic radiotherapy-proposing "coronary strip" as anew organ at risk.

Radiotherapy for breast cancer has been associated with various side effects including cardiac sequelae. Our study aimed to define the spatial arc of spread of coronary vessels in aradian angle. We analysed the records of 51CT coronary angiographies done in our hospital from January 2016 to July 2016. Left anterior descending (LAD) and right coronary (RC) were contoured for each patient. In each axial section, the radial spread of each artery was noted. A5 mm brush tool was used to join the start and stop angles for making the summated "coronary strips". Start and end angle of LAD with 95% confidence interval (CI) (in clockwise direction) were 23.9 ± 4° and 79.0 ± 6.6°, respectively. Mean LAD arc length ± SD (standard deviation) noted was 55.1° ± 7.7° (95% CI). For RC the smallest start angle and the largest end angle in all patients was 297.6° and 322.6°, respectively. RC start angle, end angle and arc length for 95% confidence interval were 322.2 ± 6.1°, 292.4 ± 11.6° and 29.8 ± 13.1°, respectively. Our study provides ameasure of the radial spread of the coronary arteries, especially from the perspective of breast radiotherapy. We have proposed anew organ at risk (OAR) of coronary strip. This should provide an easy and cost-effective way to delineate the coronary vasculature in breast cancer patients undergoing radiotherapy.

Velocity Distribution in an Annular Diffuser Fitted with Twisted Hub for Different Area Ratios

This investigation is aimed at studying the flow and velocity characteristics in an annular diffuser fitted with square twisted hub for different geometries. The study was numerically performed. The formulation was based on the steady-state Reynolds averaged Navier–Stokes equations with two-equation turbulence models. In this study, the effect of different twisted hub geometries was studied using three area ratios (AR) 2.4, 2.8 and 3.7 with air as the working fluid. The analysis of the flow features in an annular diffuser fitted with twisted hub showed that the insertion of twisted hub distributed the velocity as well as promoted the radial spread of the tangential velocity. The results show the development of the velocity distribution improved with the insertion of the square twisted hub. More importantly, the obtained results illustrate the velocity distribution through the annular diffuser increases with decreases the area ratio (AR). In addition, the results indicate that the square twisted hub with area ratio (AR) 2.4 offered a higher velocity distribution.

Monte Carlo simulation of Varian Linac for 6 MV photon beam with BEAMnrc code

The purpose of this study is to investigate the effects of the initial electron beam parameters on the absorbed dose distribution calculated with EGSnrc Monte Carlo code, for 6MV photon beam. A proposed methodology for benchmarking the BEAMnrc model of Varian Linac has been used. Also, a new photon cross section data based on ENDF/B-VII release 8 evaluation has been employed. The parameters tested include mean energy, radial intensity distribution and angular spread of the initial electron beam. Mean energy and angular spread were tested for a square irradiation field 10 × 10cm2, whereas beam width of the electron beam was studied for 10 × 10cm2 at different depths and 30 × 30cm2 at depth of 10cm. The results obtained are compared with measurement data to select the optimal electron beam parameters. The differences between MC calculation and measurements data are analyzed using gamma index criteria which fixed within 1% −1mm accuracy.The obtained results indicated that the depth-dose and dose-profile curves were considerably influenced by the mean energy of the electron beam. The depth-dose curves were unaffected by the beam width of the electron beam, for both irradiation fields. On the contrary, lateral dose-profile curves were affected by the beam width of initial electron beam. Both dose-profile and depth-dose curves were unaffected to the angular spread of the electron beam. A deep depth of 10 × 10cm2 is very accurate to tune the beam width. Mean energy and beam width must be tuned precisely, to get the MC does distribution with acceptable accuracy.

Soil moisture study under drip irrigated cabbage (Brassica oleracea L. var. capitata) in sandy loam soil

Field experiment was conducted at Plasticulture Farm, CTAE, Udaipur, Rajasthan during Rabi season of 2012-2013 and 2013-2014 on sandy loam soil to study the moisture distribution pattern of sandy loam soil under the drip irrigated cabbage at various irrigation and fertigation levels. The experiments were laid out in Factorial Randomized Block Design with ten treatments which included three irrigation levels 100, 80 and 60% of evapotranspiration (ET) along with three fertigation levels, viz., 100, 75 and 50% of recommended dose of fertilizer and one control (Surface irrigation at 1.0 IW/CPE ratio + 100% RDF through farmer’s practice) and were replicated thrice. Observations revealed that highest yield (340.73 q ha -1 ) was recorded with the treatment combination of drip irrigation with 80 % ET and fertigation @ 75 % RDF. The crops treated with 80 per cent ET experienced that the moisture content was maintained near to field capacity at the root zone of the crop. The vertical and radial spread of water in the soil increased with the amount of irrigation. In all the treatments, the soil moisture distribution along the vertical direction increased and laterally it was decreased.

Estimates of the evolution of small perturbations in the radial spread (drain) of a viscous ring

This paper studies the evolution of small perturbations in the kinematic and dynamic characteristics of the radial flow of a flat ring filled with a homogeneous Newtonian fluid or an ideal incompressible fluid. When the flow rate is specified as a function of time, the main motion is completely determined by the incompressibility condition regardless of the properties of the medium. A biparabolic equation for the stream function with four homogeneous boundary conditions which simulate adhesion to the expanding (contracting) walls of the ring is derived. Upper bounds for the perturbation are obtained using the method of integral relations for quadratic functionals. The case of an exponential decay of initial perturbations is considered in a finite or infinite time interval. The admissibility of the inviscid limit in this problem is proved, and upper and lower bounds for this limit are estimated.

Full annulus numerical study of hot streaks propagation in a hydrogen-rich syngas-fired heavy duty axial turbine

This paper presents a study of the effect of fuel composition on hot streaks propagation in a high-pressure turbine using a full annulus unsteady computational fluid dynamics analysis of the first two stages. Hot streaks result from the inherent non-uniformities of temperature profiles at the exit of the combustion chamber. Variations in composition arise from current challenges requiring gas turbines to adapt to fuel variations driven by the need to reduce CO2 emissions through the use of synthetic hydrogen-rich fuels (syngas) typically generated from the gasification of coal or solid waste. Syngas containing 80% hydrogen has been used in this study in a heavy duty gas turbine modified to accommodate the low calorific value fuel. Calculations were conducted on the baseline gas turbine originally designed for natural gas for the comparative study. Applying combustor representative hot streak profiles, analyses were performed for different hot streak distributions and locations. Analysis of results focused on the segregation of cold and hot fluid patterns and the effects of hot streaks on secondary flows and temperature re-distributions up to the second turbine stage. The hot flow pattern is affected by the fuel composition, resulting in more concentrated thermal wake shapes for syngas when compared to the reference natural gas fuel. In effect, the interaction with the secondary flow leads to more intense flow turning of the pressure side leg of the horseshoe vortex in the first rotor passage. The higher temperature levels in the case of syngas, in combination with the effect of the enhanced secondary flow, result in higher radial spread of the hot fluid that tends to migrate towards the blade hub and tip with the effects being obvious further downstream the first turbine stage.

Epicardial-endocardial breakthrough during stable atrial macroreentry: Evidence from ultra–high-resolution 3-dimensional mapping

Evidence for epicardial-endocardial breakthrough (EEB) is derived from mapping inferences in patients with atrial fibrillation who may also have focal activations. The purpose of this study was to investigate whether EEB could be discerned during stable right atrial (RA) macroreentry using high-density high-spatial resolution 3-dimensional mapping. Macroreentry was diagnosed using 3-dimensional mapping and entrainment. Bipolar maps were reviewed for EEB defined as (1) presence of focal endocardial activation with radial spread unaccounted for by an endocardial wavefront and (2) present with the same timing on every tachycardia cycle. The EEB site was always in proximity to a line of endocardial conduction slowing or block. Distance and conduction velocity from the line of block to the EEB site was calculated. Electrograms at EEB sites were individually analyzed for morphology and to confirm direction of activation. Entrainment was performed at EEB sites. Twenty-six patients were studied. Fourteen examples of EEB were seen: 11 at the posterior RA (4 at the superior portion of the posterior wall and 7 at the inferior section) and 1 each at the cavotricuspid isthmus postablation, RA septum, and inferolateral RA. The mean area of the EEB site was 0.6 ± 0.2 cm2. A mean of 79.5% ± 18.6% of unipolar electrograms at the EEB site demonstrated an rS morphology. The mean distance and conduction velocity from the line of endocardial block to the EEB site at the posterior RA was 13.6 ± 2.3 mm and 59.3 ± 12.3 cm/s, respectively. In 4 patients, entrainment demonstrated that EEB sites were within the circuit and in 1 of these patients critical to arrhythmia maintenance. Activation maps during tachycardia and coronary sinus pacing demonstrated EEB at the same anatomic site. EEB sites were demonstrated in stable atrial macroreentry supported by systematic entrainment confirmation and demonstration of the same phenomenon during pacing.

Angular emission from 1D and 2D meso- and nano-structures: Probed by dual-channel Fourier-plane microscopy

The optical emission characteristics from individual nanostructures such as organic waveguides, plasmonic nanowires and 2D materials such as MoS2 can vary depending on the nature of interface on which they are grown or deposited. We constructed a dual-channel Fourier-plane microscopy, and studied the directional emission characteristics of an individual organic mesowires, Ag nanowires and MoS2 nanolayers through the glass substrate or air superstrate. Specifically, we show the ability of our microscope to quantitatively probe the radial and azimuthal angular spread in the waveguided PL from the distal ends of the mesowire across the interface without changing its position or orientation. Furthermore, from the guided PL spectral signatures, we show that the finesse of the waveguided Fabry-Perot resonance depends on whether the measurement was performed through the substrate or superstrate. To reveal the versatility of our microscope, we have quantified angular distribution of directional light scattering from the distal end of Ag nanowire at an interface, and angular distribution of excitonic emission from MoS2 nanolayers through a glass substrate. Our work highlights the capability of dual-channel Fourier microscope in quantifying the angular emission characteristics from individual optical antenna structures at an interface, and can be extrapolated to nonlinear organic nanophotonic regimes.

Direct Observation of Strain Transmission through the Microtubule Network of Cardiomyocytes

The stable microtubule (MT) network plays a significant role in regulating cardiomyocyte contractility and acts as a critical component for stretch-dependent activation of intracellular Ca2+ release. Our previous studies suggest that force transmission though the MT network enhances Ca2+ sparks in response to mechanical stress, yet stress transmission through the MT network has not been observed or characterized. To this end we have combined high-speed sub-diffraction limit microscopy and atomic force microscopy (AFM) to directly observe deformation of the MT network in response to localized stress. The radial spread of MT deflection and the timescale of network relaxation was quantified while directly probing myocyte mechanical properties. We find that the normalized radial propagation of strain in the MT network is inversely proportional to cardiomyocyte stiffness. Further, MT strain propagation is decreased by a post-translational modification of the MT network, detyrosination, which is increased in heart disease. To determine if MT deflections may be transmitting forces capable of enhancing Ca2+ release, the length and time dependence of calcium sparks were measured before, during and after localized mechanical stress. During the application of stress, a localized upregulation in calcium sparks occured over the same length-scale that deformations in the MT network propagated. These findings suggest that the stable MT-network may transmit mechanical signals through the cardiomyocyte that correlate with Ca2+ release and depend on MT detyrosination.

Intact-decay transitions in profiles of density-calibratable resistance drilling devices using long thin needles

In 1986, two German universities started developing resistance drilling for tree-ring analysis in a joint physics–botany project. In order to differentiate between early wood and late wood zones of tree-rings, the system had to provide a minimum spatial (>10 points per mm) and signal (>10 Bit) resolution combined with a high (preferably linear) correlation to wood density (r² > 0.8). The same conditions have to be fulfilled when decay in trees and timber should be identified reliably because the stages of decomposition by fungal decay are largely characterised and differentiated by the corresponding loss in density. Experiences from thousands of drillings in trees since 1986 suggest that the profile trend in the transition zone from intact to decayed wood seems to indicate the speed of radial extension of the decomposition. For a few of the various types of resistance drills used on the market, a sufficient resolution and precision in combination with a high correlation to wood density was already shown. Consequently, these device types deliver correspondingly reliable profiles enabling experts to estimate trends in future radial increments as well as in radial spread of decay.

Measuring landscape-scale spread and persistence of an invaded submerged plant community from airborne remote sensing.

Processes of spread and patterns of persistence of invasive species affect species and communities in the new environment. Predicting future rates of spread is of great interest for timely management decisions, but this depends on models that rely on understanding the processes of invasion and historic observations of spread and persistence. Unfortunately, the rates of spread and patterns of persistence are difficult to model or directly observe, especially when multiple rates of spread and diverse persistence patterns may be co-occurring over the geographic distribution of the invaded ecosystem. Remote sensing systematically acquires data over large areas at fine spatial and spectral resolutions over multiple time periods that can be used to quantify spread processes and persistence patterns. We used airborne imaging spectroscopy data acquired once a year for 5years from 2004 to 2008 to map an invaded submerged aquatic vegetation (SAV) community across 2220km2 of waterways in the Sacramento-San Joaquin River Delta, California, USA, and measured its spread rate and its persistence. Submerged aquatic vegetation covered 13-23km2 of the waterways (6-11%) every year. Yearly new growth accounted for 40-60% of the SAV area, ~50% of which survived to following year. Spread rates were overall negative and persistence decreased with time. From this dataset, we were able to identify both radial and saltatorial spread of the invaded SAV in the entire extent of the Delta over time. With both decreasing spread rate and persistence, it is possible that over time the invasion of this SAV community could decrease its ecological impact. A landscape-scale approach allows measurements of all invasion fronts and the spatial anisotropies associated with spread processes and persistence patterns, without spatial interpolation, at locations both proximate and distant to the focus of invasion at multiple points in time.

Effect of buoyancy on power deposition in microwave cavity hydrogen plasma source

A self-consistent model describing the coupling of resonant microwave radiation and plasma has been constructed. This model improves upon the models developed by Hassouni et al and Hagelaar et al, in 1999 and 2004, respectively with inclusion of hydrodynamic effects. The model has been used to study the effect of buoyancy on power deposition in microwave assisted hydrogen plasmas at different operating pressures over the range 25–300 mbar and power over the range 400 and 4000 W. Three cases viz. normal reactor (g = −9.81 m s−2, negative buoyancy), pure diffusion (g = 0 m s−2) and the inverted case (g = 9.81 m s−2, positive buoyancy) were considered. Buoyancy effects in the cavity become important at high power / pressure operating conditions. The formation of a secondary plasma zone is strongly increased in the presence of negative buoyancy, while positive buoyancy and diffusion cases are more stable. Also the density of atomic hydrogen close to the substrate is larger with a wider radial spread for the positive buoyancy case over normal operating conditions which augurs well for achieving good deposition of diamond.

SU‐F‐I‐54: Spatial Resolution Studies in Proton CT Using a Phase‐II Prototype Head Scanner

Purpose:To characterize the modulation transfer function (MTF) of the pre‐clinical (phase II) head scanner developed for proton computed tomography (pCT) by the pCT collaboration. To evaluate the spatial resolution achievable by this system.Methods:Our phase II proton CT scanner prototype consists of two silicon telescopes that track individual protons upstream and downstream from a phantom, and a 5‐stage scintillation detector that measures a combination of the residual energy and range of the proton. Residual energy is converted to water equivalent path length (WEPL) of the protons in the scanned object. The set of WEPL values and associated paths of protons passing through the object over a 360° angular scan is processed by an iterative parallelizable reconstruction algorithm that runs on GP‐GPU hardware. A custom edge phantom composed of water‐equivalent polymer and tissue‐equivalent material inserts was constructed. The phantom was first simulated in Geant4 and then built to perform experimental beam tests with 200 MeV protons at the Northwestern Medicine Chicago Proton Center. The oversampling method was used to construct radial and azimuthal edge spread functions and modulation transfer functions. The spatial resolution was defined by the 10% point of the modulation transfer function in units of lp/cm.Results:The spatial resolution of the image was found to be strongly correlated with the radial position of the insert but independent of the relative stopping power of the insert. The spatial resolution varies between roughly 4 and 6 lp/cm in both the the radial and azimuthal directions depending on the radial displacement of the edge.Conclusion:The amount of image degradation due to our detector system is small compared with the effects of multiple Coulomb scattering, pixelation of the image and the reconstruction algorithm. Improvements in reconstruction will be made in order to achieve the theoretical limits of spatial resolution.

Dynamics of a thin radial liquid flow

The present work proposes an extension of the existing analytical development on the radial spread of a liquid jet over a horizontal surface to the case of a thin radial flow. When the gap, H, between the jet nozzle and the plate is reduced the discharging area may be smaller than the inlet area leading to an increase of the main flow velocity downstream of the thin cylindrical opening. This increase of velocity, defined here as 1α, can be related to the relative gap of the nozzle HR with R the nozzle pipe radius. Numerical computations with a volume of fluid method were realised with for HR ranging from 0.2 to 3 and with flow rates Q of 3 and 6lmin−1. The results of these computations allowed us to express α with respect to HR. Taking in account the flow acceleration allowed us to extend the set of equation from the jet impacting flow to the thin cylindrical opening flow. The liquid layer thickness and the surface velocity differ with a maximum error of 4% between the flow predicted by the model and computations. Main discrepancies appear in the region close to the nozzle where the analytical model assumption of a constant velocity outside the boundary layer is not valid. However, further downstream the model and the computations are in good agreement.

Monte Carlo simulation of beam characteristics from small fields based on TrueBeam flattening-filter-free mode.

PurposeThrough the Monte Carlo (MC) simulation of 6 and 10 MV flattening-filter-free (FFF) beams from Varian TrueBeam accelerator, this study aims to find the best incident electron distribution for further studying the small field characteristics of these beams.MethodsBy incorporating the training materials of Varian on the geometry and material parameters of TrueBeam Linac head, the 6 and 10 MV FFF beams were modelled using the BEAMnrc and DOSXYZnrc codes, where the percentage depth doses (PDDs) and the off-axis ratios (OARs) curves of fields ranging from 4 × 4 to 40 × 40 cm2 were simulated for both energies by adjusting the incident beam energy, radial intensity distribution and angular spread, respectively. The beam quality and relative output factor (ROF) were calculated. The simulations and measurements were compared using Gamma analysis method provided by Verisoft program (PTW, Freiburg, Germany), based on which the optimal MC model input parameters were selected and were further used to investigate the beam characteristics of small fields.ResultsThe Full Width Half Maximum (FWHM), mono-energetic energy and angular spread of the resultant incident Gaussian radial intensity electron distribution were 0.75 mm, 6.1 MeV and 0.9° for the nominal 6 MV FFF beam, and 0.7 mm, 10.8 MeV and 0.3° for the nominal 10 MV FFF beam respectively. The simulation was mostly comparable to the measurement. Gamma criteria of 1 mm/1 % (local dose) can be met by all PDDs of fields larger than 1 × 1 cm2, and by all OARs of no larger than 20 × 20 cm2, otherwise criteria of 1 mm/2 % can be fulfilled. Our MC simulated ROFs agreed well with the measured ROFs of various field sizes (the discrepancies were less than 1 %), except for the 1 × 1 cm2 field.ConclusionsThe MC simulation agrees well with the measurement and the proposed model parameters can be clinically used for further dosimetric studies of 6 and 10 MV FFF beams.

Temporal and interspecific variation in rates of spread for insect species invading Europe during the last 200 years

Globalization is triggering an increase in the establishment of alien insects in Europe, with several species having substantial ecological and economic impacts. We investigated long-term changes in rates of species spread following establishment. We used the total area of countries invaded by 1171 insect species for which the date of first record in Europe is known, to estimate their current range radius (calculated as [invaded area]0.5/π). We estimated initial rates of radial spread and compared them among different groups of insects for all years (1800–2014) and for a subset of more recent decades (1950–2014). Accidentally introduced species spread faster than intentionally introduced species. Considering the whole period 1800–2014, spread patterns also differ between feeding guilds, with decreasing spread rates over residence time in herbivores but not in detritivores or parasitic species. These decreases for herbivorous species appeared mainly in those associated with herbaceous plants and crops rather than woody plants. Initial spread rate was significantly greater for species detected after 1990, roughly 3–4 times higher than for species that arrived earlier. We hypothesize that the political changes in Europe following the collapse of the Iron Curtain in 1989, and the further dismantling of customs checkpoints within an enlarged European Union (EU) have facilitated the faster spread of alien insect species. Also, the number of species first recorded in the Eastern Bloc of the politically-divided Europe before 1989 was lower than for the rest of Europe. A detailed analysis of six recent invaders indicated a dominant role of long-distance translocations related to human activities, especially with the plant trade, in determining rates of spread.

Diagnostics of Plasma Jet Generated in Water/Argon DC Arc Torch

Thermal plasma jet generated by the torch with water/argon stabilized arc was investigated. Plasma torches of this type have been used for plasma spraying, waste treatment and gasification of organic materials. Electric probes, enthalpy probe, and schlieren photography were used for diagnostics of the jet in the region downstream of the torch exit. Information about structure and shape of plasma jet was evaluated from the measured data. Large extent of radial plasma spread and high level of turbulence were found from both the schlieren and the probe diagnostics. Plasma temperature corresponding to measured ion saturation currents was determined using calculated composition of plasma assuming ex-istence of local thermodynamic equilibrium.

Propagation of spontaneous slow-wave activity across columns and layers of the adult rat barrel cortex in vivo.

During slow-wave sleep, neocortical networks exhibit self-organized activity switching between periods of concurrent spiking (up-states) and periods of network silence (down-states), a phenomenon also occurring under the effects of different anesthetics and in in vitro brain slice preparations. Although this type of ongoing activity has been implicated into important functions such as memory consolidation and learning, the manner in which it propagates across different cortical modules (i.e., columns and layers) has not been fully characterized. In the present study, we investigated this issue by measuring spontaneous activity at large scale in the adult rat barrel cortex under urethane anesthesia by means of voltage-sensitive dye imaging and 128-channel probe recordings. Up to 74 neurons located in all layers of up to four functionally identified barrel-related columns were recorded simultaneously. The spontaneous activity propagated isotropically across the cortical surface with a median speed of ~35µm/ms. A concomitant radial spread of activation was present from deep to superficial cortical layers. Thus, spontaneous activity occurred rather globally in the barrel cortex, with ≥50% of the up-states presenting spikes in ≥3 columns and layers. Temporally precise spike sequences, which occurred repeatedly (although sporadically) within the up-states, were typically led by putative excitatory neurons in the infragranular cortical layers. In summary, our data provide for the first time an overall view of the spontaneous slow-wave activity within the barrel cortex circuit, characterizing its propagation across columns and layers at high spatio-temporal resolution.