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Objective To report the clinical and MRI-based volumetric mid-term outcome after image guided percutaneous sclerotherapy (PS) of venous malformations (VM) of the head and neck. Methods A retrospective analysis of a prospectively maintained database was performed, including patients with VM of the head and neck who were treated with PS. Only patients with available pre- and post-interventional MRI were included into this study. Clinical outcome, which was subjectively assessed by the patients, their parents (for paediatric patients) and/or the physicians, was categorized as worse, unchanged, minor or major improvement. Radiological outcome, determined by MRI-based volumetric measurements, was categorized as worse (>10% increase), unchanged (≤10% increase to <10% decrease), minor (≥10% to <25% decrease), intermediate (≥25% to <50% decrease) or major improvement (≥50% decrease). Results Twenty-seven patients were treated in 51 treatment sessions. After a mean follow-up of 31 months, clinical outcome was worse for 7.4%, unchanged for 3.7% of the patients, while there was minor and major improvement for 7.4% and 81.5%, respectively. In the volumetric imaging analysis 7.4% of the VMs were worse and 14.8% were unchanged. Minor improvement was observed in 22.2%, intermediate improvement in 44.4% and major improvement in 11.1%. The rate of permanent complications was 3.7%. Conclusion PS can be an effective therapy to treat the symptoms of patients with VMs of the head and neck and to downsize the VMs. MRI-based volumetry can be used to objectively follow the change in size of the VMs after PS. Relief of symptoms frequently does not require substantial volume reduction.

Over the last years there has been a growing interest in the study of the behavior of field‐responsive or so called smart materials. Porous ferrogels are a class of these materials consisting of a porous polymeric matrix with dispersed micro‐ or nano‐sized ferromagnetic particles [1–3]. Due to their ability to exhibit large deformations and alter their effective material characteristics upon external magnetic stimulation, these materials are interesting for a wide range of applications in biomedical engineering, microfluidics and other innovative fields of research. The magneto‐poro‐mechanical response of porous ferrogels is a complex phenomenon that spans over multiple length‐scales and essentially depends on (i) the constitutive behavior of the individual components, (ii) their morphology and microstructural arrangement and (iii) the macroscopic shape of the specimen. In this contribution a theoretical and computational framework for the modeling of isotropic porous ferrogels at the macroscale is presented. Within this modeling approach the porous ferrogel is treated as a homogeneous continuum, whereat its complex microstructure is not resolved explicitly. A prototypical isotropic constitutive model is formulated in a conventional enthalpy‐based setting. Numerical examples show the the crucial impact of the macroscopic specimen shape on the macroscopic deformation response in an uniform external magnetic field.

Porous ferrogels are a new class of magnetoactive composite materials that consist of a polymeric hydrogel matrix with embedded magnetizable particles. The mutual particle interaction within the soft elastic matrix enables ferrogels to deform and alter their material characteristics upon magnetic stimulation. Due to these unique properties, ferrogels have attracted significant attention for potential uses in a variety of engineering applications, especially in biomedical engineering and microfluidics. Therefore, it is crucial to develop precise mathematical models capturing the complex material behavior of ferrogels, which spans over multiple length scales. The aim of this work is to present suitable modeling approaches for porous ferrogels. Following the hierarchical structure of scales, we present modeling frameworks for two different scenarios: (i) the modeling of ferrogels at the macroscale level and (ii) the modeling of ferrogels at the microscale level. Regarding the constitutive modeling of ferrogels, we limit our attention to locally nondissipative isotropic material response. For both modeling approaches, we provide comprehensive variational principles and briefly discuss relevant ingredients of a stable finite element implementation. In each section, numerical simulations are outlined in order to demonstrate the capabilities and relevant features of each modeling approach. Main emphasis of the numerical studies lies on the investigation of the macroscopic shape effect as well as on the characterization of the magnetomechanical material response of ferrogels with random monodisperse microstructures.