Combined use of 3D printing and mixed reality technology for neurosurgical training: getting ready for brain surgery.

OBJECTIVE: Learning surgical skills is an essential part of neurosurgical training. Ideally, these skills are acquired to a sufficient extent in an ex vivo setting. The authors previously described an in vitro brain tumor model, consisting of a cadaveric animal brain injected with fluorescent agar-agar, for acquiring a wide range of basic neuro-oncological skills. This model focused on haptic skills such as safe tissue ablation technique and the training of fluorescence-based resection. As important didactical technologies such as mixed reality and 3D printing become more readily available, the authors developed a readily available training model that integrates the haptic aspects into a mixed reality setup. METHODS: The anatomical structures of a brain tumor patient were segmented from medical imaging data to create a digital twin of the case. Bony structures were 3D printed and combined with the in vitro brain tumor model. The segmented structures were visualized in mixed reality headsets, and the congruence of the printed and the virtual objects allowed them to be spatially superimposed. In this way, users of the system were able to train on the entire treatment process from surgery planning to instrument preparation and execution of the surgery. RESULTS: Mixed reality visualization in the joint model facilitated model (patient) positioning as well as craniotomy and the extent of resection planning respecting case-dependent specifications. The advanced physical model allowed brain tumor surgery training including skin incision; craniotomy; dural opening; fluorescence-guided tumor resection; and dura, bone, and skin closure. CONCLUSIONS: Combining mixed reality visualization with the corresponding 3D printed physical hands-on model allowed advanced training of sequential brain tumor resection skills. Three-dimensional printing technology facilitates the production of a precise, reproducible, and worldwide accessible brain tumor surgery model. The described model for brain tumor resection advanced regarding important aspects of skills training for neurosurgical residents (e.g., locating the lesion, head position planning, skull trepanation, dura opening, tissue ablation techniques, fluorescence-guided resection, and closure). Mixed reality enriches the model with important structures that are difficult to model (e.g., vessels and fiber tracts) and advanced interaction concepts (e.g., craniotomy simulations). Finally, this concept demonstrates a bridging technology toward intraoperative application of mixed reality.

In-Vitro Use of Verteporfin for Photodynamic Therapy in Glioblastoma.

BACKGROUND: Stummer et al. established fluorescence-guided surgery (FGS) for glioblastoma (GBM) using 5-aminolevulinic acid (5-ALA). Its metabolite, protoporphyrin IX (PPIX), is also a photosensitizer and can be used for photodynamic therapy (PDT) using a laser beam of 635 nm. The porphyrin derivate verteporfin (VP) was discovered to have properties to penetrate the brain, pharmacologically target glioma cells, and is approved for PDT of choroidal neovascularization in wet age-related macular degeneration at 689 nm. OBJECTIVE: To elucidate whether GBM cell lines are susceptible to PDT with second-generation photosensitizer VP. METHODS: Human glioma cell lines LN229, HSR-GBM1, and a low-passage patient-derived GBM cell line P1 were treated with variable concentrations of VP for 24 h, followed by PDT at 689 nm using a diode laser light. Cell viability was measured using the MTT assay and VP uptake was measured using a desktop cytometer. RESULTS: Significantly higher cell death following PDT with VP compared to VP treatment alone or no treatment was detected in all cell models (LN229, HSR-GBM1, P1). Flowcytometric measurements revealed a concentration-dependent cellular uptake of VP after 24 h incubation up to 99% at 10 µM (HSR-GBM1). CONCLUSION: This study demonstrates that PDT with VP causes cell death in GBM cells at marginal concentrations. Additionally, red spectrum fluorescence was detected at therapeutic concentrations in all cell lines, validating the cellular uptake of VP in GBM cells. VP, therefore, is not only a potential drug for targeting GBM pharmacologically but can be used as an optical imaging dye in surgery and photosensitizer to make GBM susceptible to PDT.

Testing the Stability of Drug Resistance on Cryopreserved, Gene-Engineered Human Induced Pluripotent Stem Cells.

Human induced pluripotent stem cells (hiPSCs) have emerged as a powerful tool for in vitro modelling of diseases with broad application in drug development or toxicology testing. These assays usually require large quantities of hiPSC, which can entail long-term storage via cryopreservation of the same cell charges. However, it is essential that cryopreservation does not oppose durable changes on the cells. In this project, we characterize one parameter of functionality of one that is well established in the field, in a different research context, an applied hiPSC line (iPS11), namely their resistance to a medium size library of chemo interventions (>160 drugs). We demonstrate that cells, before and after cryopreservation, do not change their relative overall drug response phenotypes, as defined by identification of the top 20 interventions causing dose-dependent reduction of cell growth. Importantly, also frozen cells that are exogenously enforced for stable overexpression of oncogenes myelocytomatosis (cMYC) or tumor protein 53 mutation (TP53R175H), respectively, are not changed in their relative top 20 drugs response compared to their non-frozen counterparts. Taken together, our results support iPSCs as a reliable in vitro platform for in vitro pharmacology, further raising hopes that this technology supports biomarker-associated drug development. Given the general debate on ethical and economic problems associated with the reproducibly crisis in biomedicine, our results may be of interest to a wider audience beyond stem cell research.