Clinical Application to Improve the "Depth Perception Problem" by Combining Augmented Reality and a 3D Printing Model.

In our experience with intraoperative evaluation and educational application of augmented reality technology, an illusion of depth has been a major problem. To improve this depth perception problem, we conducted two experiments combining various three-dimensional models and holograms and the observation angles using an augmented reality device. Methods: In experiment 1, when observing holograms projected on the surface layer of the model (bone model) or holograms projected on a layer deeper than the model (body surface model), the observer's first impression regarding which model made it easier to understand positional relationships was investigated. In experiment 2, to achieve a more quantitative evaluation, the observer was asked to measure the distance between two specific points on the surface and deep layers from two angles in each of the above combinations. Statistical analysis was performed on the measurement error for this distance. Results: In experiment 1, the three-dimensional positional relationships were easier to understand in the bone than in the body surface model. In experiment 2, there was not much difference in the measurement error under either condition, which was not large enough to cause a misunderstanding of the depth relationship between the surface and deep layers. Conclusions: Any combination can be used for preoperative examinations and anatomical study purposes. In particular, projecting holograms on a deep model or observing positional relationships from not only the operator's viewpoint, but also multiple other angles is more desirable because it reduces confusion caused by the depth perception problem and improves understanding of anatomy.

Clinical Applications of Meshed Multilayered Anatomical Models by Low-Cost Three-Dimensional Printer.

SUMMARY: In recent years, even low-cost fused deposition modeling-type three-dimensional printers can be used to create a three-dimensional model with few errors. The authors devised a method to create a three-dimensional multilayered anatomical model at a lower cost and more easily than with established methods, by using a meshlike structure as the surface layer. Fused deposition modeling-type three-dimensional printers were used, with opaque polylactide filament for material. Using the three-dimensional data-editing software Blender (Blender Foundation, www.blender.org) and Instant Meshes (Jakob et al., https://igl.ethz.ch/projects/instant-meshes/) together, the body surface data were converted into a meshlike structure while retaining its overall shape. The meshed data were printed together with other data (nonmeshed) or printed separately. In each case, the multilayer model in which the layer of the body surface was meshed could be output without any trouble. It was possible to grasp the positional relationship between the body surface and the deep target, and it was clinically useful. The total work time for preparation and processing of three-dimensional data ranged from 1 hour to several hours, depending on the case, but the work time required for converting into a meshlike shape was about 10 minutes in all cases. The filament cost was $2 to $8. In conclusion, the authors devised a method to create a three-dimensional multilayered anatomical model to easily visualize positional relationships within the structure by converting the surface layer into a meshlike structure. This method is easy to adopt, regardless of the available facilities and economic environment, and has broad applications.

Intraoperative 3-dimensional Projection of Blood Vessels on Body Surface Using an Augmented Reality System.

Preoperative understanding of the running pattern of blood vessels is an important factor to approach surgical fields safely. In 2 cases where the vascular abnormalities were estimated, we projected the blood vessels onto the surgical field using an augmented reality device HoloLens. A splint was made to allow the patient to be fixed while undergoing computed tomographic angiography. Three-dimensional (3D) data on the blood vessels, skin surfaces, bones, and the 3 chosen points for alignment were segmented and then projected onto the body surfaces as holograms using the HoloLens. Two types of projection for holograms were used: projection type 1-where the body contours were projected as a line, and projection type 2-where the body surface was projected as meshed skin type. By projecting projection type 2 rather than projection type 1, we gained a better understanding of the 3D anatomic findings and deformation characteristics, including the anatomic blood vessel variation and positional relationships between the organs and body surfaces. To some extent, we could make sure that the depth perception can be obtained by recognizing the bone, vessels, or tumor inside the meshed skin surface. Our new method allows the 3D visualization of blood vessels from the body surface, and helps understand the 3D anatomic variation of the blood vessels to be applied as long as the blood vessels can be visualized.

Simulation Surgery Using 3D 3-layer Models for Congenital Anomaly.

We made realistic, three-dimensional, computer-assisted 3-layered elastic models of the face. The surface layer is made of polyurethane, the intermediate layer is silicone, and the deep layer is salt, representing the skin, subcutaneous tissue, and the bone. We have applied these 3-layer models to congenital anomaly cases and have understood that these models have a lot of advantages for simulation surgery. METHODS: We made 8 models. The models consisted of 2 models of 2 cases with Crouzon disease, 1 model of Binder syndrome, 1 model of facial cleft, 2 models of one case with Goldenhar syndrome, 1 model of cleft lip and palate, and 1 model of the hemifacial macrosomia. RESULTS: We could try several methods, could recognize whether the graft size is adequate, and could visualize the change of the facial contour. We could analyze how to approach the osteotomy line and actually perform osteotomy. The changes of the lower facial contour can be observed. We grafted the models of the graft and confirmed that the incisions could be closed well. We were able to visualize the change in the soft tissue contour by simulating distraction. CONCLUSIONS: The most versatile merit of our models is that we could visualize the change of the soft tissue by movement of the hard tissue with bone graft, distraction osteogenesis, and so on. We must improve the model further to make it more realistic.

17-year Follow-up after Mandibular Distraction Performed in an Infant with Robin Sequence.

Robin sequence is a congenital anomaly, first described by Pierre Robin as a triad of micrognathia, upper airway obstruction and glossoptosis. The most significant airway management technique is the use of distraction osteogenesis to advance the mandible. On the other hand, late complications such as permanent dentition loss and malformation of the damaged teeth have been reported. Therefore, long-term follow-up after mandibular distraction is important. In our case report, we describe 17 years of follow-up after mandibular distraction performed in a 4-month-old male infant with Robin sequence. The patient was a male with a cleft palate. The tracheotomy and tongue-lip adhesion was performed 1 month after birth, because the percutaneous oxygen saturation decreased to 70% during feeding and crying. However, postoperative X-ray examination revealed that he could not obtain sufficient airway after the operation. For the purpose of closing the tracheotomy early, we performed bilateral mandibular distraction at the age of 4 months. The bilateral corticotomy was performed on the mandibular body and an internal traction device was placed. The mandible was bilaterally lengthened by 17.5 mm, and expansion of the airway was confirmed by X-ray. A cleft palate operation was performed at the age of 17 months. At the age of 3 years, the tracheostomy orifice closed and speech/language training and orthodontics were begun. Dental panoramic radiographs showed favorable mandibular growth. No additional operation has been performed. Finally, his orthodontic treatment was completed without any complications at age 17.

Functional Temporomandibular Joint Reconstruction in Costochondral Grafting of Micrognathia.

Rib bone and costochondral complex grafting has been used to treat micrognathia classified as Pruzansky type III. To acquire more physiological joint movement, we reconstructed a temporomandibular joint with the glenoid fossa in addition to the mandibular ramus. The patient underwent a tracheostomy to correct her airway obstruction at 2 months of age. After that, no further surgical treatments were performed on the micrognathia. When she was 6 years of age and during consultation at our department, micrognathia caused by Goldenhar syndrome was confirmed. A head and neck computed tomography scan showed hypoplasia and deficit of the mandible, severe glossoptosis and airway constriction. Initially, a bilateral mandibular body distraction was performed at 6 years of age, and 15 mm of elongation was obtained. Subsequently, reconstruction of the right ramus and right temporomandibular joint fossa was performed at 8 years of age to achieve extubation. Part of her sixth rib and costochondral complex graft was used for the ramus, and costochondral graft was used for the joint fossa. Some new ideas for temporomandibular joint reconstruction were added. Postoperatively, the open mouth range was increased and improvement of the airway space narrowing was observed in a computed tomography scan. The main points of this new method are prevention of ankylosis, skull cortex thinning, and reconstructed ramus' dislocation. This method may become an effective new treatment for cases of micrognathia with a ramus classified as Pruzansky type III.

Physicochemical characteristics of carbonaceous adsorbent for dioxin-like polychlorinated biphenyl adsorption.

It has been known that dioxin-like polychlorinated biphenyls (DL-PCBs) are present in almost all types of environments worldwide. Activated carbon treatment has been expected for the removal of DL-PCBs because it is a simple and low-cost removal technology. In the present study, the physicochemical properties of activated carbon were investigated to identify the characteristics of 16 different types of activated carbon on adsorption properties for DL-PCBs. To accomplish this, micropore volume, and pore diameter were calculated by t-plot analysis and the mesopore volume was analyzed by the Barrett-Joyner-Halenda (BJH) method. In addition, the Brunauer-Emmett-Teller (BET) surface area, pH, metal elements, and surface acid functional groups were analyzed. Then, adsorption experiments using DL-PCB in hexane solution were conducted, and the relationship between adsorption and physicochemical properties of activated carbon was investigated. The results showed that activated carbons having a surface area of 700-1200 m(2)g(-1) and micropores with diameters of about 0.7-0.8 nm exhibited high activity for the adsorption of PCBs. The results also clearly showed that the mesopore volume of activated carbon influenced the adsorption rate and the equilibrium adsorption.