Attenuation Profiles Research Articles

CBCT artefact-burden of zirconia-based as compared to titanium implants for different beam energies: an analytical approach

Beam hardening artefacts induced by highly-dense material (e.g. metal) is a common quality issue in maxillofacial Cone Beam Computed Tomography (CBCT-) images. This experimental and analytical study investigated attenuation patterns of two typical dental implant materials: zirconia-ceramic and pure titanium. By application of different x-ray beam energies (60, 70, 80, 90 [kVp]) energy-dependent attenuation of these materials is assessed and the resulting artefact induction in the resulting CBCT-images evaluated. A zirconia (Y-TZP-) implant (varnothing: 4.1 mm) and a pure titanium rod (varnothing: 4.0 mm) were exposed in a commercial CBCT (3D Accuitomo 170). The raw two-dimensional (2D) projection radiographs the CBCT utilizes for three-dimensional reconstruction applied for acquisition of attenuation profiles through the circular central slice of the implant-phantom images. Distances the x-rays traverse through the implant-phantoms at this location were computed. Using this information and the linear attenuation coefficient, transmission and attenuation was computed for each material and beam energy. These data were related to beam hardening artefacts that were assessed in the axial reconstructions of the implants’ CBCT images. Transmission of titanium for all peak kilovoltages (kVp) was higher and approximately 200% that of Y-TZP at 60 kVp versus 530% at 90 kVp. At 4 mm diameter transmission for Y-TZP was only approximately 5 % for all four beam-energies. In agreement with this finding, beam hardening artefacts for Y-TZP could not be reduced using higher energies, whereas for titanium they decreased with increasing energy. For the energy spectrum used in this study (60–90 kVp), beam hardening caused by titanium can be reduced using higher energies while this is not the case for zirconia-ceramic (Y-TZP).

Flexural Wave Propagation in Rigid Elastic Combined Metabeam

Abstract In this paper, flexural wave propagation, attenuation, and reflection through finite number of rigid elastic combined metabeam (RECM) elements sandwiched between two Euler Bernoulli beams has been studied, implementing the spectral element, inverse Fourier transform, and transfer matrix method. Spectral element has been formulated for the unit representative cell of RECM employing the rigid body dynamics. Governing dimensionless parameters are identified. Furthermore, the sensitivity analysis has been carried out to comprehend the influence of non-dimensional parameters, such as mass ratio, length ratio, and rotary inertia ratio on the attenuation profile. Rotary inertia of rigid body produces local resonance (LR) band, which may abridge the gap between the two Bragg scattering (BS) bands and results in an ultra-wide stop band for the specific combination of governing non-dimensional parameters. A total of 164% normalized attenuation band is possible to obtain in RECM. Natural frequencies for the finite RECM have also been evaluated from the global spectral element matrix and observed that some natural frequencies lie in the attenuation band. Therefore, the level of attenuation near that natural frequencies is significantly less and cannot be identified from the dispersion diagram of the infinite RECM.

Network upgrade exploiting multi band: S- or E-band?

Nowadays, the fiber spectrum is only partially exploited, i.e., mainly in the C-band and more recently in the C + L-band, where the fiber attenuation profile experiences the minimum. Thus, fiber communications technology—amplifiers, switching, transceivers, etc.—and networking solutions are mature for those spectrum bands. However, the continuous increase in traffic means that capacity saturation of the current infrastructure is looming. Taking advantage of the unused portions of the spectrum (e.g., the S- and E-bands) may be an efficient solution to accommodate an increase in traffic without installing new fibers. Research is thus investigating multi-band transmission and networking to evaluate and enable such network upgrades. Some issues need to be solved or taken into account, from the enabling technology (e.g., amplifiers in the S- or E-band are still under development) to physical layer effects previously neglected, such as stimulated Raman scattering (SRS). SRS affects wideband transmission, potentially degrading active channels. The contribution of this paper is the investigation of network upgrades for C + L-band systems. In particular, upgrades exploiting the E- and S-bands are compared taking into account each band capacity and the effects of SRS on both new and already deployed channels (in both the C- and L-bands). A detailed analysis of the physical layer is provided also in the presence of guard bands between previously exploited bands and the bands used for upgrade. By leveraging the physical layer assessment, a networking analysis is carried out to evaluate the supported traffic increase and also the signal quality degradation due to SRS on active channels. The results suggest that upgrades to the E- and S-bands support a comparable increase in traffic. However, the exploitation of the E-band with 14 THz of guard band between the C- and E-bands may avoid detrimental effects to already active channels in the C + L-band, suggesting this upgrade strategy can be the most effective of the two.

Propagation Attenuation Maps Based on Parabolic Equation Method.

Modern wireless communication systems use various technological solutions to increase the efficiency of created radio networks. This efficiency also applies to radio resources. Currently, the utilization of a radio environment map (REM) is one of the directions allowing to improve radio resource management. The REM is increasingly used in emerging mobile ad-hoc networks (MANETs), in particular military tactical networks. In this case, the use of new technologies such as software-defined radio and network, cognitive radio, radio sensing, and building electromagnetic situational awareness made it possible to implement REM in tactical MANETs. Propagation attenuation maps (PAMs) are crucial REM elements that allow for determining the ranges of radio network nodes. In this paper, we present a novel algorithm for PAM based on a parabolic equation method (PEM). The PEM allows determining the signal attenuation along the assumed propagation direction. In this case, we consider terrain topography to obtain a more realistic analysis. Then, we average the adjacent attenuation profiles defined for the selected directions in places where attenuation has not been calculated. To this aim, linear regression is applied. Finally, we define several metrics that allow for the accuracy assessment of determining the PAM as a function of its dimensions.

Spatially Variant Ultrasound Attenuation Mapping Using a Regularized Linear Least-Squares Approach

Quantitative ultrasound methods aim to estimate the acoustic properties of the underlying medium, such as the attenuation and backscatter coefficients, and have applications in various areas including tissue characterization. In practice, tissue heterogeneity makes the coefficient estimation challenging. In this work, we propose a computationally efficient algorithm to map spatial variations of the attenuation coefficient. Our proposed approach adopts a fast, linear least-squares strategy to fit the signal model to data from pulse-echo measurements. As opposed to existing approaches, we directly estimate the attenuation map, that is, the local attenuation coefficient at each axial location by solving a joint estimation problem. In particular, we impose a physical model that couples all these local estimates and combine it with a smooth regularization to obtain a smooth map. Compared to the conventional spectral log difference method and the more recent ALGEBRA approach, we demonstrate that the attenuation estimates obtained by our method are more accurate and better correlate with the ground-truth attenuation profiles over a wide range of spatial and contrast resolutions.

Deep learning-based monitoring of surface residual stress and efficient sensing of AE for laser shock peening

• A multi-channel acoustic emission real-time efficient signal detection method and acquisition system. • A novel spatio-temporal complementary model (CNN-LSTM) for fusion of time-varying AE signal. • Dual circulation LSTM explains the decay mechanism of AE using temporal sampling points. • Stronger correlation between information from AE attenuation profile and surface quality. Laser shock peening (LSP) is one of the main anti-fatigue technologies in high-end manufacturing industries. However, guaranteeing its quality consistency is difficult due to its process complexity. Acoustic emission (AE) is a promising solution to accurately monitoring the surface quality of LSP, although, the large scale of monitoring data is still challenging for industrial applications. This paper studied the in-situ evaluation of surface residual compressive stress (SRCS) for 7075 aluminum alloy in LSP and the efficient sensing of AE based on deep learning methods. Firstly, a monitoring system of LSP with four types of AE sensors was developed in order to simultaneously acquire both the ultra-high and ultra-low amplitude of shock wave. The performance of those sensors is further quantitatively evaluated via long-short term memory (LSTM). Then, a new spatio-temporal parallel CNN-LSTM model for SRCS classification was proposed and experimentally validated to outperform CNN and LSTM after parameters optimization. Finally, aiming to efficient sensing of AE, the importance of different frames of AE signal was analyzed by means of the proposed dual circulation LSTM (DC-LSTM) model, which can accurately locate the key frame of time series signal. Besides, the effects of different frames of AE on classification performance was discussed. It was found that the broadband AE sensor without attenuator shows the highest classification accuracy, while the fast decay stage of AE signal has more contribution to the SRCS classification. This paper provides guidance for real-time non-destructive evaluation of residual stress via AE in laser manufacturing.

A novel use of time separation technique to improve flat detector CT perfusion imaging in stroke patients.

CT perfusion imaging (CTP) is used in the diagnostic workup of acute ischemic stroke (AIS). CTP may be performed within the angio suite using flat detector CT (FDCT) to help reduce patient management time. In order to significantly improve FDCT perfusion (FDCTP) imaging, data-processing algorithms need to be able to compensate for the higher levels of noise, slow rotation speed, and a lower frame rate of current FDCT devices. We performed a realistic simulation of FDCTP acquisition based on CTP data from seven subjects. We used the time separation technique (TST) as a model-based approach for FDCTP data processing. We propose a novel dimension reduction in which we approximate the time attenuation curves by a linear combination of trigonometric functions. Our goal was to show that the TST can be used even without prior assumptions on the shape of the attenuation profiles. We first demonstrated that a trigonometric basis is suitable for dimension reduction of perfusion data. Using simulated FDCTP data, we have shown that a trigonometric basis in the TST provided better results than the classical straightforward processing even with additional noise. Average correlation coefficients of perfusion maps were improved for cerebral blood flow (CBF), cerebral blood volume, mean transit time (MTT) maps. In a moderate noise scenario, the average Pearson's coefficient for the CBF map was improved using the TST from 0.76 to 0.81. For the MTT map, it was improved from 0.37 to 0.45. Furthermore, we achieved a total processing time from the reconstruction of FDCTP data to the generation of perfusion maps of under 5 min. In our study cohort, perfusion maps created from FDCTP data using the TST with a trigonometric basis showed equivalent perfusion deficits to classic CT perfusion maps. It follows, that this novel FDCTP technique has potential to provide fast and accurate FDCTP imaging for AIS patients.

Concurrent Solar-Illumination and Power Line Voice Communication for Indian Underground Coal Mines – An Experimental Study

The illumination systems in underground coal mines in India, generally operating in unfavourable, hazardous, and restricted environments, are badly in need of updating and revamping as they play a vital role in mine safety and productivity. Moreover, person-to-person communication in underground coal mines is very inadequate. In view of limited resources, the provision of illumination and communication using the same infrastructure forms an attractive proposition. As wireless communication is not a viable alternative because of the high attenuation profile there, wired personal communication employing the proposed DC distribution system along with LED illumination proves to be a very efficient and economical approach. The proposed technique establishes the design and implementation of the very low voltage DC (LVDC) power distribution system especially for mine illumination in consort with power line voice communication for underground coal mines. The environment of an Indian underground coal mine is simulated inside a sub-way tunnel and a suitable model designed. An experimental study is made to validate the technical aspects. The major contribution of the present work is a novel solution comprising of a low-cost mine-safe illumination system along with essential voice communication by the same underground infrastructure.

Normal incidence reflection coefficient measurements of layered sand-mud sediment and comparison to models

Depth-dependent variability in seabed acoustic and geophysical properties can be introduced by both physical and biogenic processes. An experiment was conducted near the mouth of Mobile Bay, Alabama to investigate spatial variability over a mud-sand gradient, where sediment properties showed lateral changes on the scales of tens of meters. Additionally, sediment layering on the scale of centimeters was evident in the top 20 cm of the seabed. Normal-incidence seabed reflection coefficient measurements (20–60 kHz) were acquired using a ship-mounted system to survey a 1.9 km2 area of the seabed, and diver cores were collected for direct analysis of near-surface seabed properties. The cores were acoustically logged to obtain vertical profiles of sound speed and attenuation (10–1000 kHz) and then analyzed for vertical profiles of sediment physical properties (porosity, grain size, organic matter content), infauna community composition, and tensile strength. Physical and acoustic profiles obtained from the cores were then used as inputs to model the n-layer reflection coefficient. Comparison of the modeled and measured reflection coefficients will be discussed. [Work supported by ONR.]

Utility of dual energy computed tomography in the evaluation of infiltrative skeletal lesions and metastasis: a literature review.

Computed tomography (CT) is routinely used to diagnose and evaluate metastatic lesions in oncology. CT alone suffers from lack of sensitivity, especially for skeletal lesions in the bone marrow and lesions that have similar attenuation profiles to surrounding bone. Magnetic resonance imaging and nuclear medicine imaging remain the gold standard in evaluating skeletal lesions. However, compared to CT, these modalities are not as widely available or suitable for all patients. Dual energy computed tomography (DECT) exploits variations in linear attenuation coefficient of materials at different photon energy levels to reconstruct images based on material composition. DECT in musculoskeletal imaging is used in the imaging of crystal arthropathy and detecting subtle fractures, but it is not broadly utilized in evaluating infiltrative skeletal lesions. Malignant skeletal lesions have different tissue and molecular compositions compared to normal bone. DECT may exploit these physical differences to delineate infiltrative skeletal lesions from surrounding bone better than conventional monoenergetic CT. Studies so far have examined the utility of DECT in evaluating skeletal metastases, multiple myeloma lesions, pathologic fractures, and performing image-guided biopsies with promising results. These studies were mostly retrospective analyses and case reports containing small samples sizes. As DECT becomes more widely used clinically and more scientific studies evaluating the performance of DECT are published, DECT may eventually become an important modality in the work-up of infiltrative skeletal lesions. It may even challenge MRI and nuclear medicine because of relatively faster scanning times and ease of access.

Dual-Energy CT, Virtual Non-Calcium Bone Marrow Imaging of the Spine: An AI-Assisted, Volumetric Evaluation of a Reference Cohort with 500 CT Scans.

Virtual non-calcium (VNCa) images from dual-energy computed tomography (DECT) have shown high potential to diagnose bone marrow disease of the spine, which is frequently disguised by dense trabecular bone on conventional CT. In this study, we aimed to define reference values for VNCa bone marrow images of the spine in a large-scale cohort of healthy individuals. DECT was performed after resection of a malignant skin tumor without evidence of metastatic disease. Image analysis was fully automated and did not require specific user interaction. The thoracolumbar spine was segmented by a pretrained convolutional neuronal network. Volumetric VNCa data of the spine’s bone marrow space were processed using the maximum, medium, and low calcium suppression indices. Histograms of VNCa attenuation were created for each exam and suppression setting. We included 500 exams of 168 individuals (88 female, patient age 61.0 ± 15.9). A total of 8298 vertebrae were segmented. The attenuation histograms’ overlap of two consecutive exams, as a measure for intraindividual consistency, yielded a median of 0.93 (IQR: 0.88–0.96). As our main result, we provide the age- and sex-specific bone marrow attenuation profiles of a large-scale cohort of individuals with healthy trabecular bone structure as a reference for future studies. We conclude that artificial-intelligence-supported, fully automated volumetric assessment is an intraindividually robust method to image the spine’s bone marrow using VNCa data from DECT.

Optimized design of windowed-sinc anti-aliasing filters for phase-preserving decimation of hydrophone data.

Passive acoustic monitoring generates large data sets for which decimation is beneficial to analysis and portability for data sharing. Among the goals for effective decimation are avoidance of aliasing in the passband, accurate and complete control of the attenuation profile, phase preservation, and high efficiency in processing. We present an approach to decimator design that addresses each of these goals, and we demonstrate its application to ocean audio recordings. Anti-aliasing is achieved by windowed-sinc filters that also preserve phase. Control of the passband attenuation profile is based on the specification of the maximum allowed attenuation at a certain percentage of the final output Nyquist frequency. The window type is selected to meet the stopband attenuation requirement. Efficiency is achieved through optimization of the anti-aliasing filters applied in each decimation stage, and through parallelization of processing. The best combination of the sinc function's cutoff frequency and the mainlobe bandwidth of the window function generates the shortest qualifying filter, optimizing the trade-off between filter performance and computational load. Parallelization is enabled by applying the overlap-add method to contiguous segments of audio data, consistent with the commonly used storage of contiguous audio data in files of limited duration. Beyond addressing common goals for effective decimation of audio data, the approach presented is deployable in open-source environments.

How the translucency of direct anatomic fiber posts affects the bond strength and microhardness of a self-adhesive luting agent in flared roots.

To evaluate the influence of the composite resin translucency used in direct anatomic fiber posts on the bond strength (BS) and microhardness (VHN) of a luting agent into flared roots. The root canals of 70 single-rooted premolars were endodontically treated and prepared to simulate an oversized root canal. Prior to post cementation, composite resins with varying translucency (high translucent, HT; medium translucent, MT; high opacity, HO) were placed around the fiber posts to create anatomic fiber posts. The attenuation profile (%) of light passing either through the post or through the anatomic posts (n = 8) was obtained prior to the cementing procedures. A positive control group (PC) in which a prefabricated fiber post (PFP) with the diameter compatible with the root canal was cemented and a poorly adapted fiber post (negative control group, NC) were also evaluated. For both tests, the data were subjected to 2-way ANOVA and Bonferroni tests (α = 0.05). A more severe light attenuation through the post at the cervical (P < .001) and medium (P < 0.001) thirds was noted when less translucent composite resin surrounded the anatomic post. HO groups showed lower BS (P = .009) and VHN (P < .001) values than the other groups, regardless of root third. No significant difference in BS values was noted between PC and HT groups. The use of a more translucent composite resin in anatomic fiber posts increased the microhardness and bond strength of a dual polymerization self-adhesive RLA compared to the use of MT and HO composite. A well-adapted PFP showed the highest adhesive and mechanical behavior. Clinicians should choose more translucent composite resins to create direct anatomic fiber posts to be cemented in flared root canals. That choice may allow improved mechanical properties of self-adhesive RLA and higher bond strength to the root canal as a consequence.

Cognitive Raman Amplifier Control Using an Evolutionary Optimization Strategy

In this work, a cognitive Raman amplifier controller using an evolutionary optimization strategy for both in-field device calibration and optimal pump power configuration design is presented. The conceived methodology allows to jointly characterize the physical layer properties of the optical fiber span, such as the fiber attenuation profile, the entities of the lumped losses due to mechanical connectors or splices, the polarization coefficients between each Raman pump pair and the Raman efficiency curve. The developed framework expects to work using optical channel monitors (OCMs) as telemetry device and it has been experimentally validated, obtaining outstanding results in terms of precision on a C-band setup.

Role of cardiac CT in the diagnostic evaluation and risk stratification of patients with myocardial infarction and non-obstructive coronary arteries (MINOCA): rationale and design of the MINOCA-GR study

IntroductionMyocardial infarction with non-obstructive coronary arteries (MINOCA) occurs in 5%–15% of all patients with acute myocardial infarction. Cardiac MR (CMR) and optical coherence tomography have been used to identify the...

Modeling methods for dispersive sound speed profiles of the Martian atmosphere and their effects on sound propagation paths

At present, Mars acoustic detection is gradually becoming an important new tool for the knowledge and exploration of Mars. To explore the sources of Mars sound, it is necessary to study the sound speed and the sound attenuation in the thin and low-temperature Martian atmosphere, and to model the sound propagation in the stratified atmosphere. Based on the extremely low pressure of Mars and the large variation of gas composition with altitude, we proposed a simulation method based on the Navier-Stokes (NS) equation and the mixed-gas model to calculate the vertical profiles of sound speed and attenuation in the Martian atmosphere at 0~250 km altitude in this paper. By comparing sound-speed profiles at different frequencies, there is notably sound dispersion in the Martian atmosphere, especially at high altitudes and in the high frequency range. It is also verified through sound speed measurement experiments verify that significant sound dispersion does exist in low-pressure carbon dioxide, illustrating the need to consider sound dispersion in the modelling of Martian sound speed profiles. The scope of application of the NS equation in modelling the sound speed of the Martian atmosphere is also discussed, as the NS equation may fail in a too rarefied gas. Next, the non-dispersive ideal-gas sound speed profiles and the dispersive NS sound speed at different frequencies (0.01 Hz, 0.1 Hz, 1 Hz) were applied to simulate the sound propagation paths in the multilayered Martian atmosphere. And both cases of the Martian ground-based and high-altitude sources were compared respectively. It is found that the dispersive sound speed has a significant effect on the sound propagation path on Mars. The main impact is that the first fold back height and the first return distance of the sound ray to the surface are shortened, which directly changes the area and location of the acoustic quiet zone. The effect of dispersion on the sound propagation path becomes more notable with both the increasing frequency and the elevation of the acoustic source, confirming that consideration of dispersion has a significant effect on the calculation of the sound propagation path.

Methods of modelling dispersive sound speed profiles of Martian atmosphere and their effects on sound propagation paths

At present, Mars acoustic detection is gradually becoming an important new tool for understanding and exploring Mars. To explore the sources of Mars sound, it is necessary to study the sound speed and the sound attenuation in the thin and low-temperature Martian atmosphere, and to model the sound propagation in the stratified atmosphere. According to the extremely low pressure of Mars and the large variation of gas composition with altitude, we propose a simulation method based on the Navier-Stokes (NS) equation and the mixed-gas model to calculate the vertical profiles of sound speed and attenuation in the Martian atmosphere at 0–250 km altitude in this work. A comparison among sound-speed profiles at different frequencies shows that there is a notable sound dispersion in the Martian atmosphere, especially at high altitudes and in the high frequency range. It is also verified through sound speed measurement experiments that significant sound dispersion does exist in low-pressure carbon dioxide, implying the need to consider sound dispersion in the modelling of Martian sound speed profiles. The scope of application of the NS equation in modelling the sound speed of the Martian atmosphere is also discussed, as the NS equation may fail in a too rarefied gas. Next, the non-dispersive ideal-gas sound speed profiles and the dispersive NS sound speed at different frequencies (0.01, 0.1, 1 Hz) are used to simulate the sound propagation paths in the multilayered Martian atmosphere. And both cases of the Martian ground-based and high-altitude sources are compared with each other. It is found that the dispersive sound speed has a significant effect on the sound propagation path on Mars. The main influence is that the first fold back height and the first return distance of the sound ray to the surface are both shortened, which directly changes the area and location of the acoustic quiet zone. The effect of dispersion on the sound propagation path becomes more notable with both the frequency and the elevation of the acoustic source increasing, confirming that consideration of dispersion has a significant effect on the calculation of the sound propagation path.

MODELLING AUTOMATIC EXPOSURE CONTROL RESPONSE TO THE PRESENCE OF THE PATIENT SCANNING BED IN A HYBRID PET/CT SCANNER.

Automatic Exposure Control (AEC) systems optimise radiation dose to the patient while providing adequate image quality. This study examined the effect that the increased localiser region of interest of a hybrid PET/CT has on the CTDIvol, focussing on the role of extraneous objects and patient attenuation profiles. A Siemens Biograph™ 16 Horizon PET/CT system and a Siemens Somatom Sensation 64, both employing the Siemens CAREDose 4D AEC system, were used for acquisition of a range of phantoms. The effect of patient miscentring and effect of the patient bed impinging on the localiser was established and modelled. For PA localiser scans, a non-linear relationship between miscentring and CTDIvol was observed, attributable to the presence of the patient bed being misinterpreted as the patient width. The model identified how the presence of the patient bed led to an increase in the CTDIvol significantly larger than expected (~12%, or 1mSv), particularly prevalent for smaller patients.

Normal-incidence bottom loss measurements over a sand-mud gradient and comparison to direct seabed measurements

Seabed variability introduced by physical or biogenic processes contributes to multi-scale horizontal and vertical variability in seabed acoustic and geotechnical properties. An experiment was conducted near the mouth of Mobile Bay to investigate such spatial variability over a mud-sand gradient. A normal-incidence bottom loss survey was conducted on a 750 × 1500 m2 grid with 50-m track-line spacing, in which a broadband acoustic source transmitted frequency-modulated chirps (1–100 kHz) every second, resulting in dense sampling of the seabed reflection coefficient over a wide frequency band. Diver cores were collected in the survey area for direct analysis of near-surface seabed properties. Cores were acoustically logged to obtain vertical profiles of sound speed and attenuation (10–1000 kHz) and then analyzed for physical properties (porosity, grain size, carbon content), infauna community composition, and sediment strength properties. Additionally, in situ portable free fall penetrometer measurements were conducted within the survey area to characterize geotechnical properties within the upper 50 cm of the sediment. Spatial distributions of properties estimated from bottom loss measurements (e.g. porosity and sound speed) will be compared with vertical profiles from the cores and from the penetrometer to examine potential connections between seabed acoustic, geotechnical, and biological parameters. [Sponsored by ONR.]

Diffusion of gravity waves by random space inhomogeneities in pancake-ice fields. Theory and validation with wave buoys and synthetic aperture radar

We study the diffusion of ocean waves by ice bodies much smaller than a wavelength, such as pancakes and small ice floes. We argue that inhomogeneities in the ice cover at scales comparable to that of the wavelength significantly increase diffusion, producing a contribution to wave attenuation comparable to what is observed in the field and usually explained by viscous effects. The resulting attenuation spectrum is characterized by a peak at the scale of the inhomogeneities in the ice cover, which could explain the rollover of the attenuation profile at small wavelengths observed in field experiments. The proposed attenuation mechanism leads to the same behaviors that would be produced by a viscous wave model with effective viscosity linearly dependent on the ice thickness. This may explain recent findings that viscous wave models require a thickness-dependent viscosity to fit experimental attenuation data. Experimental validation is carried out using wave buoy attenuation data and synthetic aperture radar image analysis.