Using 3D-Printed Mesh-Like Brain Cortex with Deep Structures for Planning Intracranial EEG Electrode Placement.

Surgical evaluation of medically refractory epilepsy frequently necessitates implantation of multiple intracranial electrodes for the identification of the seizure focus. Knowledge of the individual brain's surface anatomy and deep structures is crucial for planning the electrode implantation. We present a novel method of 3D printing a brain that allows for the simulation of placement of all types of intracranial electrodes. We used a DICOM dataset of a T1-weighted 3D-FSPGR brain MRI from one subject. The segmentation tools of Materialise Mimics 21.0 were used to remove the osseous anatomy from brain parenchyma. Materialise 3-matic 13.0 was then utilized in order to transform the cortex of the segmented brain parenchyma into a mesh-like surface. Using 3-matic tools, the model was modified to incorporate deep brain structures and create an opening in the medial aspect. The final model was then 3D printed as a cerebral hemisphere with nylon material using selective laser sintering technology. The final model was light and durable and reflected accurate details of the surface anatomy and some deep structures. Additionally, standard surgical depth electrodes could be passed through the model to reach deep structures without damaging the model. This novel 3D-printed brain model provides a unique combination of visualizing both the surface anatomy and deep structures through the mesh-like surface while allowing repeated needle insertions. This relatively low-cost technique can be implemented for interdisciplinary preprocedural planning in patients requiring intracranial EEG monitoring and for any intervention that requires needle insertion into a solid organ with unique anatomy and internal targets.

Creating patient-specific anatomical models for 3D printing and AR/VR: a supplement for the 2018 Radiological Society of North America (RSNA) hands-on course.

Advanced visualization of medical image data in the form of three-dimensional (3D) printing continues to expand in clinical settings and many hospitals have started to adapt 3D technologies to aid in patient care. It is imperative that radiologists and other medical professionals understand the multi-step process of converting medical imaging data to digital files. To educate health care professionals about the steps required to prepare DICOM data for 3D printing anatomical models, hands-on courses have been delivered at the Radiological Society of North America (RSNA) annual meeting since 2014. In this paper, a supplement to the RSNA 2018 hands-on 3D printing course, we review methods to create cranio-maxillofacial (CMF), orthopedic, and renal cancer models which can be 3D printed or visualized in augmented reality (AR) or virtual reality (VR).

Celect Inferior Vena Cava Wall Strut Perforation Begets Additional Strut Perforation.

PURPOSE: To identify risk factors for strut perforation following Celect inferior vena cava (IVC) filter (IVCF) placement and to use finite element modeling to predict the mechanical impact of long-dwelling filters. MATERIALS AND METHODS: Ninety-one patients with three computed tomography (CT) studies were evaluated following Celect IVCF placement (2007-2013). Three-dimensional finite element models of the Celect IVCF were developed to simulate mechanical deformation of the IVCF encountered in vivo. Simulated forces applied by the primary struts on the IVC wall were measured as a function of luminal area and tilt angle. RESULTS: Although 33 patients (36%) showed primary strut perforation on initial follow-up CT, 60 patients (66%) showed progressive perforation over time (P < .0001), with 72 patients (79%) showing primary strut perforation on the final CT (average, 554 d). Female patients (P = .004) and those with malignancy history (P = .01) had significantly higher perforation rates at a given time. Caval area also decreased after primary filter strut perforation, and we therefore proposed that this was the mechanism for progressive perforation. Consistent with this mechanism, three-dimensional finite element modeling demonstrated increasing strut force with decreasing IVC diameter. CONCLUSIONS: Celect IVCF primary strut perforation is progressive over time and is more common in female patients and those with a history of malignancy. In addition, this progressive perforation may be predicted by three-dimensional finite element modeling. These patient populations may require closer follow-up after IVCF placement to prevent or reduce the risk for filter complication or worsening perforation.

Fibers in the extracellular matrix enable long-range stress transmission between cells.

Cells can sense, signal, and organize via mechanical forces. The ability of cells to mechanically sense and respond to the presence of other cells over relatively long distances (e.g., ∼100 µm, or ∼10 cell-diameters) across extracellular matrix (ECM) has been attributed to the strain-hardening behavior of the ECM. In this study, we explore an alternative hypothesis: the fibrous nature of the ECM makes long-range stress transmission possible and provides an important mechanism for long-range cell-cell mechanical signaling. To test this hypothesis, confocal reflectance microscopy was used to develop image-based finite-element models of stress transmission within fibroblast-seeded collagen gels. Models that account for the gel's fibrous nature were compared with homogenous linear-elastic and strain-hardening models to investigate the mechanisms of stress propagation. Experimentally, cells were observed to compact the collagen gel and align collagen fibers between neighboring cells within 24 h. Finite-element analysis revealed that stresses generated by a centripetally contracting cell boundary are concentrated in the relatively stiff ECM fibers and are propagated farther in a fibrous matrix as compared to homogeneous linear elastic or strain-hardening materials. These results support the hypothesis that ECM fibers, especially aligned ones, play an important role in long-range stress transmission.