Silicone-based tissue-mimicking phantom is widely used as a surrogate of tissue for clinical simulators, allowing clinicians to practice medical procedures and researchers to study the performance of medical devices. This study investigates using the mineral oil in room-temperature vulcanizing silicone to create the desired mechanical properties and needle insertion characteristics of a tissue-mimicking phantom. Silicone samples mixed with 0, 20, 30, and 40 wt. % mineral oil were fabricated for indentation and needle insertion tests and compared to four types of porcine tissues (liver, muscle with the fiber perpendicular or parallel to the needle, and fat). The results demonstrated that the elastic modulus and needle insertion force of the phantom both decrease with an increasing concentration of mineral oil. Use of the mineral oil in silicone could effectively tailor the elastic modulus and needle insertion force to mimic the soft tissue. The silicone mixed with 40 wt. % mineral oil was found to be the best tissue-mimicking phantom and can be utilized for needle-based medical procedures.

This study develops a thermal model utilizing the inverse heat transfer method (IHTM) to investigate the bone grinding temperature created by a spherical diamond tool used for skull base neurosurgery. Bone grinding is a critical procedure in the expanded endonasal approach to remove the cranial bone and access to the skull base tumor via nasal corridor. The heat is generated during grinding and could damage the nerve or coagulate the blood in the carotid artery adjacent to the bone. The finite element analysis is adopted to investigate the grinding-induced bone temperature rise. The heat source distribution is defined by the thermal model, and the temperature distribution is solved using the IHTM with experimental inputs. Grinding experiments were conducted on a bovine cortical bone with embedded thermocouples. Results show significant temperature rise in bone grinding. Using 50°C as the threshold, the thermal injury can propagate about 3 mm in the traverse direction, and 3 mm below the ground surface under the dry grinding condition. The presented methodology demonstrated the capability of being a thermal analysis tool for bone grinding study.

J Neurosurg 124:811-816, 2016P atients suffering from pathologies of the ventral and ventrolateral skull base often require surgical intervention. Access to the skull base traditionally required extensive tissue manipulation, but recent advances in endoscopic techniques have allowed access to the skull base using less destructive techniques via the nostril as a natural corridor. The endoscopic endonasal approach (EEA) is employed in the treatment of pituitary adenomas, Rathke's cleft cysts, ventral cranial base meningiomas, craniopharyngiomas, chordomas, olfactory neuroblastomas, and sinonasal carcinomas involving the skull base, among other pathologies. Exposure and resection often require drilling of bone adjacent to critical neurovascular structures. Cranial nerve damage can result in catastrophic disability, and vascular injury may be maiming or fatal. 6 Although residents are trained to perform the EEA by participating in operations on patients while under close supervision, critical drilling is often still done by the attending surgeon. Endoscopic endonasal drilling is somewhat unique in regard to the instruments used, the long reach required, and the restricted angulation. Cadaver training is a viable option for teaching such skills, when available. Sensory feedback from cadaver bone remains largely unchanged from live tissue, and the anatomy remains intact. However, cadavers are expensive and require specialized equipment, staff, and facilities. Availability of specimens or facilities, in most cases, precludes the use of cadavers for basic technique training; rather, their value is maximized when used by more experienced operators. Alternatively, a number of virtual reality (VR) simulators are available for EEA, but they often lack realistic drilling haptics, and the initial costs could be high. 2,10We successfully developed a physical simulator for ventriculostomy placement and demonstrated its validity. 15 Based on that experience, we also sought to create an inexpensive, high-fidelity simulator by which the drilling aspects of the EEA could be practiced by trainees once they advance to the point of surgical participation, thereby reducing the risk to patients. This endeavor, a collaborative effort of neurosurgeons, otolaryngologists, engineers, and an education/research specialist, is described in terms of simulator design, training setup, and validation process. In this paper, the authors present a physical model developed to teach surgeons the requisite drilling techniques when using an endoscopic endonasal approach (EEA) to the skull base. EEA is increasingly used for treating pathologies of the ventral and ventrolateral cranial base. Endonasal drilling is a unique skill in terms of the instruments used, the long reach required, and the restricted angulation, and gaining competency requires much practice. Based on the successful experience in creating custom simulators, the authors used 3D printing to build an EEA training model from post-processed thin-cut head CT scans, formulating the materials ...

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22abbreviatioNs EVD = external ventricular drain; ICP = intracranial pressure; VR = virtual reality. In this paper, the authors present a physical model developed to simulate accurate external ventricular drain (EVD) placement with realistic haptic and visual feedbacks to serve as a platform for complete procedural training. Insertion of an EVD via ventriculostomy is a common neurosurgical procedure used to monitor intracranial pressures and/or drain CSF. Currently, realistic training tools are scarce and mainly limited to virtual reality simulation systems. The use of 3D printing technology enables the development of realistic anatomical structures and customized design for physical simulators. In this study, the authors used the advantages of 3D printing to directly build the model geometry from stealth head CT scans and build a phantom brain mold based on 3D scans of a plastinated human brain. The resultant simulator provides realistic haptic feedback during a procedure, with visualization of catheter trajectory and fluid drainage. A multiinstitutional survey was also used to prove content validity of the simulator. With minor refinement, this simulator is expected to be a cost-effective tool for training neurosurgical residents in EVD placement.

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Twist drills produced the smallest temperature rise among all bit types. Thermal effects should not be a reason for choosing K-wire size. The cannulated drill showed significantly higher temperatures when compared with standard drills, reaching maximal temperatures comparable with K wires.

The grinding procedure and setup, the cutting edge inclination and rake angles of the needle with lancet point (NLP), and the NLP tissue insertion force are investigated in this paper. The NLP is the most commonly used needle tip geometry. However, there is a lack of research on the NLP grinding and cutting edge characteristics. In this study, a fourstep grinding procedure and a mathematical model to calculate the inclination and rake angles along the cutting edge of the NLP are developed. Three cases of NLP are defined based on the relative position of the lancets. Prototype NLP for each case was produced and analyzed. Compared to the regular bias bevel needle, grinding two lancets in NLP can increases the inclination angle, particularly at the needle tip. Experiments with needle insertion into the porcine liver were conducted and results showed that NLP could achieve over 40% reduction of the initial peak needle insertion force compared to that of the regular bias bevel needle tip.