After birth, the skull grows and remodels in close synchrony with the brain to allow for an increase in intracranial volume. Increase in skull area is provided primarily by bone accretion at the sutures. Additional remodeling, to allow for a change in curvatures, occurs by resorption on the inner surface of the bone plates and accretion on their outer surfaces. When a suture fuses too early, normal skull growth is disrupted, leading to a deformed final skull shape. The leading theory assumes that the main stimulus for skull growth is provided by mechanical stresses. Based on these ideas, we first discuss the dimensional, geometrical, and kinematic synchrony between brain, skull, and suture growth. Second, we present two mechanical models for skull growth that account for growth at the sutures and explain the various observed dysmorphologies. These models demonstrate the particular role of physical and geometrical constraints taking place in skull growth.
Remote magnetic navigation offers an ideal platform for automated catheter navigation. Magnetically guided catheters show great dexterity and can reach locations that are otherwise challenging to access. By automating aspects of catheterization procedures, we can simplify and expedite the procedure to allow surgeons to focus on other critical tasks during the surgery. In this article, we describe an automation strategy that is based on the center line of extracted and registered vascular geometries. Position feedback is accomplished with a Hall-effect sensor embedded near the distal end of the catheter. Sensor measurements are compared to the magnetic field predicted by a linear model of the electromagnetic navigation system. By defining specific magnetic field gradients and applying the known vascular geometry, the magnetic fields can be utilized for the simultaneous navigation and localization of the catheter. This eliminates the need for other external, dedicated mapping systems, and the use of fluoroscopy imaging is minimized. The concept is tested in 2d vascular models and the accuracy of the localization is assessed with overhead camera tracking.
Magnetic materials are key players for the development and implementation of novel technologies. However, the integration and tunability of these materials in complex designs remain challenging due to constraints in currently available manufacturing approaches. Herein, the fabrication of 3D printing (3DP) thermoplastic‐bonded magnetic composites is investigated with both tailored geometries and magnetic properties using a customized fused deposition modeling 3D printer. First, the level of complexity that can be achieved by printing magnetic architectures with different geometries is shown. Next, it is shown that architectures with tailored magnetic properties (saturation magnetization and coercivity) can be achieved by combining prints with different magnetic properties (i.e., hard‐ and soft, or hard‐ and semi‐hard). Additionally, to demonstrate the versatility and powerfulness of fused deposition, self‐contained mechanisms, which comprise multiple parts (magnetic and nonmagnetic) without the need for assembly, are successfully fabricated. As an example, planetary magnetic gearboxes are printed with different configurations and their potential applicability as magnetic rotary encoders is demonstrated.
Remote magnetic navigation offers various possibilities for medical interventions. Magnetic catheters can be wirelessly steered with high precision and accuracy through complex structures, as they are generally more dexterous and flexible than their manually steered counterparts. Position feedback is essential for many tasks. However, most commercially available systems do not integrate well with the magnetic navigation systems. As a result, fluoroscopy is still widely used in many interventions despite the known associated health risks.In this study, we propose a localization method that uses multiple Hall sensors to measure the magnetic fields produced by the magnetic navigation system and estimate the full sensor pose without the need for a separate dedicated mapping system. This makes the magnetic navigation system a 2-in-1 system that can be used for simultaneous navigation and localization of a medical tool.We perform an optimization of the sensors' array design in simulation and investigate the influence of the magnetic fields and gradients on the localization accuracy to provide information on the minimal requirements for a magnetic navigation system for this task.
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