Acoustical modeling and Bayesian inference for rigid porous media in the low-mid frequency regime.

In this article, a modeling extension for the description of wave propagation in porous media at low-mid frequencies is introduced. To better characterize the viscous and inertial interactions between the fluid and the structure in this regime, two additional terms described by two parameters α 1 and α 2 are taken into account in the representation of the dynamic tortuosity in a Laurent-series on frequency. The model limitations are discussed. A sensitivity analysis is performed, showing that the influence of α 1 and α 2 on the acoustic response of porous media is significant. A general Bayesian inference is then conducted to infer, simultaneously, the posterior probability densities of the model parameters. The proposed method is based on the measurement of waves transmitted by a slab of rigid porous material, using a temporal model for the direct and inverse transmission problem. Bayesian inference results obtained on three different porous materials are presented, which suggests that the two additional parameters are accessible and help reduce systematic errors in the identification of other parameters: porosity, static viscous permeability, static viscous tortuosity, static thermal permeability, and static thermal tortuosity.

Guidelines update: Post-treatment follow-up of adult head and neck squamous cell carcinoma: Screening for metastasis and metachronous esophageal and bronchial locations.

OBJECTIVE: The present article is an update of the guideline of the French Society of Otorhinolaryngology and Head and Neck Surgery (SFORL) on the post-treatment follow-up of adult head and neck squamous cell carcinoma concerning screening for metastasis and metachronous esophageal and bronchial locations. METHODS: A multidisciplinary work-group was entrusted with a review of the literature on the above topic. Guidelines were drawn up, based on the articles retrieved and the work-group members' own experience. These were then reviewed by an editorial group independent of the work-group. A coordination meeting then finalized the guidelines. Guidelines were graded A, B, C or "expert opinion" according to decreasing level of evidence.

Guidelines of the French Society of Otorhinolaryngology (SFORL), short version. Diagnosis of local recurrence and metachronous locations in head and neck oncology.

Surveillance is fundamental to the management of head and neck cancer. The present guidelines of the French ENT society (SFORL) were drawn up by a group of experts in the field, and are intended to specify the modalities of management, based on a review of the literature and, where data are lacking, to provide expert opinion. The present paper deals with guidelines for the diagnosis of local and regional recurrence and metachronous head and neck locations. Locoregional recurrence usually occurs within 3 years of primary treatment and is mainly related to the characteristics of the primary tumor and the treatment measures taken. Laryngeal location, safe primary resection margins, low level of lymph node invasion, unimodal primary treatment and early diagnosis of recurrence are factors of good prognosis. Systematic imaging surveillance may be considered for patients for whom a curative technique exists and when surveillance is difficult. The role of PET-scanning remains to be determined. Metachronous locations are frequent, even in the late course; prolonged surveillance is appropriate. The best preventive measure is cessation of alcohol abuse and smoking. Patient education is primordial.

Multiple scattering of acoustic waves and porous absorbing media.

Porous media like air-saturated polymer foams with open cells, have a nontrivial frequency-dependent absorption that arises due to viscous and thermal effects at the scale of the rigid frame microstructure. In order to produce multiple scattering at ultrasonic frequencies, mesoscale scatterers are introduced in the porous medium host. The effective wave number of such a multiscale medium should take into account the peculiar absorption at the microscale and the multiple scattering at the mesoscale to describe precisely the propagation of a coherent acoustic wave. For this purpose, a simple model is developed. First, an equivalent fluid model, derived from a homogenization method, is used to describe the acoustic propagation in the host porous medium itself. Second, the scattering by the inclusions is described with a multiple scattering approximation (independent scattering approximation). This simple model allows to obtain the total effective wave number of the porous medium with mesoscale scatterers. After some validating results on the multiple scattering by an array of rigid cylinders in air, experiments on the multiple scattering by rigid cylinders embedded in a porous medium are presented and compared to the developed simple model. Incidentally, it appears that for the host medium itself, the equivalent fluid model is not capable to describe the high-frequency behavior whilst a multiple scattering approach with (thin) viscous and thermal boundary layers around the scatterers is accurate in the whole frequency range.