Fabrication and Characterization of Brain Tissue Phantoms Using Agarose Gels for Ultraviolet Vision Systems.

Recreating cerebral tissue using a tissue-mimicking phantom is valuable because it provides a tool for studying physiological and biological processes related to tissues without the necessity of performing the study directly in the tissue or even in a patient. The reproduction of the optical properties allows investigation in areas such as imaging, optics, and ultrasound, among others. This paper presents a methodology for manufacturing agarose-based phantoms that mimic the optical characteristics of brain tissue using scattering and absorbing agents and proposes combinations of these agents to recreate the healthy brain tissue optical coefficients within the wavelength range of 350 to 500 nm. The results of the characterization of the manufactured phantoms propose ideal combinations of the used materials for their use in controlled environment experiments in the UV range, following a cost-effective methodology.

Agarose Gel Characterization for the Fabrication of Brain Tissue Phantoms for Infrared Multispectral Vision Systems.

Synthetic phantoms that recreate the characteristics of biological tissues are valuable tools for systematically studying and comprehending physiologies, pathologies, and biological processes related to tissues. The reproduction of mechanical and optical properties allows for the development and evaluation of novel systems and applications in areas such as imaging, optics, ultrasound, or dosimetry, among others. This paper proposes a methodology for manufacturing agarose-based phantoms that mimics the optical properties of healthy brain tissue within the wavelength infrared range of 800 to 820 nm. The fabrication of such phantoms enables the possibility of testing and experimentation in controlled and safe environments toward the design of new near-infrared multispectral imaging systems in neurosurgery. The results of an experimental optical characterization study indicate the validity and reliability of the proposed method for fabricating brain tissue phantoms in a cost-effective and straightforward fashion.

Augmented reality simulation as training model of ventricular puncture: Evidence in the improvement of the quality of punctures.

BACKGROUND: Ventricular puncture is a common procedure in neurosurgery and the first that resident must learn. Ongoing education is critical to improving patient outcomes. However, training at the expense of potential risk to patients warrants new and safer training methods for residents. METHODS: An augmented reality (AR) simulator for the practice of ventricular punctures was designed. It consists of a navigation system with a virtual 3D projection of the anatomy over a 3D-printed patient model. Forty-eight participants from neurosurgery staff performed two free-hand ventricular punctures before and after a training session. RESULTS: Participants achieved enhanced accuracy in reaching the target at the Monro foramen after practicing with the system. Additional metrics revealed significantly better trajectories after the training. CONCLUSION: The study confirms the feasibility of AR as a training tool. This motivates future work towards standardising new educative methodologies in neurosurgery.

Force-Sensorless Identification and Classification of Tissue Biomechanical Parameters for Robot-Assisted Palpation.

The implementation of robotic systems for minimally invasive surgery and medical procedures is an active topic of research in recent years. One of the most common procedures is the palpation of soft tissues to identify their mechanical characteristics. In particular, it is very useful to identify the tissue's stiffness or equivalently its elasticity coefficient. However, this identification relies on the existence of a force sensor or a tactile sensor mounted at the tip of the robot, as well as on measuring the robot velocity. For some applications it would be desirable to identify the biomechanical characteristics of soft tissues without the need for a force/tactile nor velocity sensors. An estimation of such quantities can be obtained by a model-based state observer for which the inputs are only the robot joint positions and its commanded joint torques. The estimated velocities and forces can then be employed for closed-loop force control, force reflection, and mechanical parameters estimation. In this work, a closed-loop force control is proposed based on the estimated contact forces to avoid any tissue damage. Then, the information from the estimated forces and velocities is used in a least squares estimator of the mechanical parameters. Moreover, the estimated biomechanical parameters are employed in a Bayesian classifier to provide further help for the physician to make a diagnosis. We have found that a combination of the parameters of both linear and nonlinear viscoelastic models provide better classification results: 0% misclassifications against 50% when using a linear model, and 3.12% when using only a nonlinear model, for the case in which the samples have very similar mechanical properties.

A Wearable System Based on Multiple Magnetic and Inertial Measurement Units for Spine Mobility Assessment: A Reliability Study for the Evaluation of Ankylosing Spondylitis.

Spinal mobility assessment is essential for the diagnostic of patients with ankylosing spondylitis. BASMI is a routine clinical evaluation of the spine; its measurements are made with goniometers and tape measures, implying systematic errors, subjectivity, and low sensitivity. Therefore, it is crucial to develop better mobility assessment methods. The design, implementation, and evaluation of a novel system for assessing the entire spine's motion are presented. It consists of 16 magnetic and inertial measurement units (MIMUs) communicated wirelessly with a computer. The system evaluates the patient's movements by implementing a sensor fusion of the triaxial gyroscope, accelerometer, and magnetometer signals using a Kalman filter. Fifteen healthy participants were assessed with the system through six movements involving the entire spine to calculate continuous kinematics and maximum range of motion (RoM). The intrarater reliability was computed over the observed RoM, showing excellent reliability levels (intraclass correlation >0.9) in five of the six movements. The results demonstrate the feasibility of the system for further clinical studies with patients. The system has the potential to improve the BASMI method. To the best of our knowledge, our system involves the highest number of sensors, thus providing more objective information than current similar systems.

A High-Fidelity Hybrid Virtual Reality Simulator of Aneurysm Clipping Repair With Brain Sylvian Fissure Exploration for Vascular Neurosurgery Training.

INTRODUCTION: Microsurgery clipping is one of the most challenging surgical interventions in neurosurgery. The opportunities to train residents are scarce, but the need for accumulating practice is mandatory. New simulating tools are needed for skill learning. METHODS: The design, implementation, and assessment of a new hybrid aneurysm clipping simulator are presented. It consists of an ergonomic workstation with a patient head mannequin and a physics-based virtual reality simulation with bimanual haptic feedback. The simulator recreates scenarios of microsurgery from the patient fixation and the exploration of the brain lobes through Sylvian fissure and vascular structures to the aneurysm clipping. Skill metrics were introduced, including monitoring of gestures movements, exerted forces, tissue displacements, and precision in clipping. RESULTS: Two experimental conditions were tested: (1) simple clipping without brain tissue exploration and (2) clipping the aneurysm with brain Sylvian fissure exploration. Differences in the bimanual gestures were observed between both conditions. The quantitative measurements of tissue displacement of the brain lobes exhibited more tissue retrieval for the surgical gestures of neurosurgeons. Appraisal with questionnaires showed positive scores by neurosurgeons in all items evaluating the usability and realism of the simulator. CONCLUSIONS: The simulator was well accepted and feasible for training purposes. The analysis of the interactions with virtual tissues offers information to establish differential and common patterns between tested groups and thus useful metrics for skill evaluation of practitioners. Future work can lead to other tasks during the intervention and the inclusion of more clinical cases.

Virtual reality simulation of robotic transsphenoidal brain tumor resection: Evaluating dynamic motion scaling in a master-slave system.

BACKGROUND: Integrating simulators with robotic surgical procedures could assist in designing and testing of novel robotic control algorithms and further enhance patient-specific pre-operative planning and training for robotic surgeries. METHODS: A virtual reality simulator, developed to perform the transsphenoidal resection of pituitary gland tumours, tested the usability of robotic interfaces and control algorithms. It used position-based dynamics to allow soft-tissue deformation and resection with haptic feedback; dynamic motion scaling control was also incorporated into the simulator. RESULTS: Neurosurgeons and residents performed the surgery under constant and dynamic motion scaling conditions (CMS vs DMS). DMS increased dexterity and reduced the risk of damage to healthy brain tissue. Post-experimental questionnaires indicated that the system was well-evaluated by experts. CONCLUSION: The simulator was intuitively and realistically operated. It increased the safety and accuracy of the procedure without affecting intervention time. Future research can investigate incorporating this simulation into a real micro-surgical robotic system.

Young adult binge drinkers have immunophenotypic changes in peripheral polymorphonuclear cells and monocytes.

BACKGROUND: High alcohol intake on weekends (binge drinking) is more frequent in young adults, who could undergo early liver damage. Alcohol-induced liver damage is characterized by polymorphonuclear cell (PMN) infiltration, which can be represented in the peripheral blood by altered trafficking and activation profiles. OBJECTIVE: To evaluate the PMN trafficking and activation immunophenotypic profiles in people with a binge drinking pattern. METHODS: People with binge drinking (n = 18, 8 females) or at low risk (n = 16, 13 females) based on their AUDIT and HEPCA scores were studied. Hematic biometry and liver enzyme tests were conducted. Peripheral blood leukocytes were stained for CCR5, CCR4, and CXCR4 (trafficking) and CD69 and CD127 (activation). PMNs and monocytes were analyzed by FACS. The data were analyzed using the T-test and Mann-Whitney's U-test for contrasts and principal component and Fuzzy C means analyses for clustering, with p < 0.05 considered significant. RESULTS: Compared to the low-risk group, the binge group showed higher CCR5 expression on PMNs, decreases in the CD69 percentage and positive PMNs per microliter, and decreased CXCR4 expression on monocytes. Six immunophenotypical clusters were identified, all of which were distributed following the CCR5 and CXCR4 main vectors. CONCLUSION: Young adult binge drinkers have differential PMN trafficking and activation immunophenotypes, which could be related to the initial onset of alcoholic liver disease and a systemic inflammatory state in response to their alcohol consumption pattern. These findings could lead to the future development of an early diagnostic tool.