Hideyuki Suenaga

Augmented Reality Navigation With Automatic Marker-Free Image Registration Using 3-D Image Overlay for Dental Surgery

Computer-assisted oral and maxillofacial surgery (OMS) has been rapidly evolving since the last decade. State-of-the-art surgical navigation in OMS still suffers from bulky tracking sensors, troublesome image registration procedures, patient movement, loss of depth perception in visual guidance, and low navigation accuracy. We present an augmented reality navigation system with automatic marker-free image registration using 3-D image overlay and stereo tracking for dental surgery. A customized stereo camera is designed to track both the patient and instrument. Image registration is performed by patient tracking and real-time 3-D contour matching, without requiring any fiducial and reference markers. Real-time autostereoscopic 3-D imaging is implemented with the help of a consumer-level graphics processing unit. The resulting 3-D image of the patients anatomy is overlaid on the surgical site by a half-silvered mirror using image registration and IP-camera registration to guide the surgeon by exposing hidden critical structures. The 3-D image of the surgical instrument is also overlaid over the real one for an augmented display. The 3-D images present both stereo and motion parallax from which depth perception can be obtained. Experiments were performed to evaluate various aspects of the system; the overall image overlay error of the proposed system was 0.71 mm.

Rapid and large-scale formation of chondrocyte aggregates by rotational culture

Chondrocytes in articular cartilage synthesize collagen type II and large sulfated proteoglycans, whereas the same cells cultured in monolayer (2D) dedifferentiate into fibroblastic cells and express collagen type I and small proteoglycans. On the other hand, a pellet culture system was developed as a method for preventing the phenotypic modulation of chondrocytes and promoting the redifferentiation of dedifferentiated ones. Because the pellet culture system forms only one cell aggregate each tube by a centrifugator, the pellet could not be applied to produce a tissue-engineered cartilage. Therefore, we tried to form chondrocyte aggregates by a rotational culture, expecting to form a large number of aggregates at once. In order to increase cell–cell interactions and decrease chondrocyte–material interaction, dishes with low retention of protein adsorption and cell adhesiveness were used. In addition, rotational shaking of the dish including cells was attempted to increase the cell–cell interaction. The shaking speed was set at 80 rpm, so the cells would be distributed in the center of the dish to augment the frequency of cell–cell contact. Under these conditions, bovine articular chondrocytes started aggregating in a few hours. At 24–36 h of rotational culture, aggregates with smooth surfaces were observed. Parameters such as increase of culture time and addition of TGF-β controlled diameters of the aggregates. There were many fusiform cells at the periphery of the aggregates, where the cells tended to form a multilayered zone in cross sections. In addition, lacune-like structure, which was almost the same as pellet culture, was observed. It was found that the internal structure of the aggregates was similar to that of pellets reported previously. Therefore, the aggregates formed by a rotational culture could become an essential component to make tissue-engineered artificial cartilage.

Real-time computer-generated integral imaging and 3D image calibration for augmented reality surgical navigation.

Autostereoscopic 3D image overlay for augmented reality (AR) based surgical navigation has been studied and reported many times. For the purpose of surgical overlay, the 3D image is expected to have the same geometric shape as the original organ, and can be transformed to a specified location for image overlay. However, how to generate a 3D image with high geometric fidelity and quantitative evaluation of 3D images geometric accuracy have not been addressed. This paper proposes a graphics processing unit (GPU) based computer-generated integral imaging pipeline for real-time autostereoscopic 3D display, and an automatic closed-loop 3D image calibration paradigm for displaying undistorted 3D images. Based on the proposed methods, a novel AR device for 3D image surgical overlay is presented, which mainly consists of a 3D display, an AR window, a stereo camera for 3D measurement, and a workstation for information processing. The evaluation on the 3D image rendering performance with 2560×1600 elemental image resolution shows the rendering speeds of 50-60 frames per second (fps) for surface models, and 5-8 fps for large medical volumes. The evaluation of the undistorted 3D image after the calibration yields sub-millimeter geometric accuracy. A phantom experiment simulating oral and maxillofacial surgery was also performed to evaluate the proposed AR overlay device in terms of the image registration accuracy, 3D image overlay accuracy, and the visual effects of the overlay. The experimental results show satisfactory image registration and image overlay accuracy, and confirm the system usability.

Augmented reality system for oral surgery using 3d auto stereoscopic visualization

We present an augmented reality system for oral and maxillofacial surgery in this paper. Instead of being displayed on a separated screen, three-dimensional (3D) virtual presentations of osseous structures and soft tissues are projected onto the patients body, providing surgeons with exact knowledge of depth information of high risk tissues inside the bone. We employ a 3D integral imaging technique which produce motion parallax in both horizontal and vertical direction over a wide viewing area in this study. In addition, surgeons are able to check the progress of the operation in real-time through an intuitive 3D based interface which is content-rich, hardware accelerated. These features prevent surgeons from penetrating into high risk areas and thus help improve the quality of the operation. Operational tasks such as hole drilling, screw fixation were performed using our system and showed an overall positional error of less than 1 mm. Feasibility of our system was also verified with a human volunteer experiment.

Clinical presentation of epignathus teratoma with cleft palate; and duplication of cranial base, tongue, mandible, and pituitary gland.

A 2-day-old girl was diagnosed with an oral epignathus teratoma and an uncommon combination of orofacial malformations including cleft palate; tongue, mandible, cranial base, cervical vertebrae, lower lip, and pituitary gland duplications; and fistula of the glabella and lower lip. Computed tomography revealed that the mass within the nasal cavity had tooth-like calcifications and protruded into the nasopharynx and oral cavity. It was implanted on the anterior wall of the body of the sphenoid bone and was accompanied with mandibular duplication. Magnetic resonance imaging detected duplication of the pituitary gland and confirmed the absence of intracranial communication of the nasopharyngeal mass. The teratoma did not cause respiratory obstruction; however, the patient required continuous nasogastric tube feeding. Usually, an epignathus teratoma is associated with few midline defects and can be corrected with multiple interventions at different time points. The current study describes the surgical procedure comprising excision of the tumor along with reconstructive surgeries of the mandible, tongue, and fistulae undertaken when the infant reached 7 months of age. The cleft palate was repaired at 18 months of age using the Kaplan buccal flap method. Histopathologic examination confirmed a grade 0 teratoma covered with keratinized skin and containing pilosebaceous and sweat glands, adipose tissue, and smooth muscle. The long-term success of this intervention was determined at the follow-up examination conducted at 3 years of age, with no signs of the teratoma recurrence observed.

Metastasis of Hepatocellular Carcinoma into the Mandible with Radiographic Findings Mimicking a Radicular Cyst: A Case Report

INTRODUCTION Hepatocellular carcinoma (HCC) is a common neoplasm worldwide, with more than half of the tumors associated with regional metastasis. Extrahepatic metastasis is also common, and the most frequently affected sites are the lungs, abdominal lymph nodes, diaphragm, and bone. However, HCC metastasis to the mandible is rare, with approximately 50 cases reported in the literature. METHODS In this report, we describe a case of HCC metastasis to the mandible at the apex of #18 root in a 62-year-old man. This patient had already been diagnosed with metastasis to pancreatic caput lymph node. The radiographic features of the mandible resembled radicular cyst and did not show typical findings of malignancy. RESULTS Under the first diagnosis of radicular cyst, root canal treatment was initially performed, and then surgical treatment of the removal of the cystic lesion and #18 extraction were performed. Finally, the lesion was diagnosed as HCC metastasis from pathological examination. Consequently, he received constitutional chemotherapy in the hepatitis unit and is now in remission. CONCLUSION This case shows the importance of considering the differential diagnosis of malignancy.

Cyclooxygenase-2 activity is important in craniofacial fracture repair.

The aim of this study was to examine the effect of cyclooxygenase (COX)-2 on bone repair after craniofacial fracture in mice. A 4-mm fracture was created in the parietal bone of 8-week-old male COX-2 wild-type (COX-2(+/+)) and knockout (COX-2(-/-)) mice. Ribonucleic acid was extracted from the fractured bone and analysed. For morphological and histological analysis, the mice were killed 8 and 12 weeks after treatment, and sections were prepared. Three-dimensional computed tomography was performed, and the sections were stained with hematoxylin-eosin for histological examination. Expression of COX-2 messenger ribonucleic acid was induced in COX-2(+/+) mice, but not in COX-2(-/-) mice. Ossification at the fracture site was almost complete 12 weeks after fracture in COX-2(+/+) mice. In COX-2(-/-) mice, incomplete union had occurred at the fracture site. In both types of mice, the fracture site contained no cartilaginous tissue, and the callus formed from the periosteal side. These results suggest that COX-2 plays an important role in craniofacial fracture repair and that COX-2-selective non-steroidal anti-inflammatory drugs might interfere with fracture repair of the membranous viscerocranium in the clinical setting.

Computer-assisted preoperative simulation for positioning of plate fixation in Lefort I osteotomy: A case report

Computed tomography images are used for three-dimensional planning in orthognathic surgery. This facilitates the actual surgery by simulating the surgical scenario. We performed a computer-assisted virtual orthognathic surgical procedure using optically scanned three-dimensional (3D) data and real computed tomography data on a personal computer. It helped maxillary bone movement and positioning and the titanium plate temporary fixation and positioning. This simulated the surgical procedure, which made the procedure easy, and we could perform precise actual surgery and could forecast the postsurgery outcome. This simulation method promises great potential in orthognathic surgery to help surgeons plan and perform operative procedures more precisely.

Preclinical and clinical research on bone and cartilage regenerative medicine in oral and maxillofacial region

Abstract Recently, there have been remarkable advances in regenerative medicine, and almost all disorders of the oral and maxillofacial region could be research targets of regenerative medicine. Meanwhile, treatment in this region has been well established using biomaterials, prostheses, and microsurgery. Therefore, to surpass such a conventional approach as an alternative, regenerative medicine should take an approach of being less invasive and/or more effective. In this report, we present our preclinical and clinical research on bone and cartilage regenerative medicine in the oral and maxillofacial region. Regarding bone regenerative medicine, we have tried to develop artificial bone that would maximize bone formation at the transplanted site, but would subsequently be replaced by autologous bone. We have made custom-made artificial bone (CT-Bone) using alpha-tricalcium phosphate (α-TCP) particles and an ink-jet printer, and have conducted clinical research and trials on 30 patients. To develop tissue-engineered cartilage with proper three-dimensional (3D) morphological form and mechanical strength, we have optimized the culture medium of chondrocytes and the scaffold. Following a preclinical study confirming efficacy and safety, we have conducted clinical research in three patients with nasal deformity associated with cleft lip and palate, and are now starting multicenter clinical research.

Real-Time Marker-Free Patient Registration and Image-Based Navigation Using Stereovision for Dental Surgery

Surgical navigation techniques have been evolving rapidly in the field of oral and maxillofacial surgery (OMS). However, challenges still exist in the current state of the art of computer-assisted OMS especially from the viewpoint of dental surgery. The challenges include the invasive patient registration procedure, the difficulty of reference marker attachment, navigation error caused by patient movement, bulky optical markers and maintenance of line of sight for commercial optical tracking devices, inaccuracy and susceptibility of electromagnetic (EM) sensors to magnetic interference for EM tracking devices. In this paper, a new solution is proposed to overcome the mentioned challenges. A stereo camera is designed as a tracking device for both instrument tracking and patient tracking, which is customized optimally for the limited surgical space of dental surgery. A small dot pattern is mounted to the surgical tool for instrument tracking, which can be seen by the camera at all times during the operation. The patient registration is achieved by patient tracking and 3D contour matching with the preoperative patient model, requiring no fiducial marker and reference marker. In addition, the registration is updated in real-time. Experiments were performed to evaluate our method and an average overall error of 0.71 mm was achieved.