A design for simulating and validating the nuss procedure for the minimally invasive correction of pectus excavatum.

Surgical planners are used to achieve the optimal outcome for a surgery, especially in procedures where a positive aesthetic outcome is the primary goal, such as the Nuss procedure which is a minimally invasive surgery for correcting pectus excavatum (PE)--a congenital chest wall deformity. Although this procedure is routinely performed, the outcome depends mostly on the correct placement of the bar. It would be beneficial if a surgeon had a chance to practice and review possible strategies for placement of the corrective bar and the associated appearance of the chest. Therefore, we propose a strategy for the development and validation of a Nuss procedure surgical trainer and planner.

Development and Validation of a Hybrid Nuss Procedure Surgical Simulator and Trainer.

OBJECTIVE: This work presents the development and validation of an interactive simulation training platform for the minimally invasive repair of pectus excavatum, otherwise known as the Nuss procedure. METHODS: The challenges and implications of developing both an all-virtual and an all-physical version of the simulator are investigated in a training context. A hybrid system is then developed that integrates virtual and physical constituents and a haptic interface to reproduce the primary steps of the procedure and to satisfy clinically relevant prerequisites for its training system. Furthermore, this work carries out a study to investigate the system's face, content, and construct validity. RESULTS: Objective and subjective evaluations of the system demonstrate its utility for surgical training and establish various levels of its validity. CONCLUSION: A hybrid virtual/physical configuration of the trainer can efficiently and realistically reproduce the primary steps of the procedure. SIGNIFICANCE: Outside of this work, a simulation and training platform for the Nuss procedure is not available. This system was developed in close collaboration with the pioneers of this surgical technique.

Medical student evaluation using virtual pathology echocardiography (VPE) for augmented standardized patients.

With the increasing role played by ultrasound in clinical diagnostics, ultrasound training in medical education is becoming more important. We have developed a real-time ultrasound simulator to augment standardized patients (SPs) with a simulated echocardiogram. It enables changes in the standard of ultrasound training where the clinical routine is practiced on real patients, which limits monitored and guided examinations for medical students due to time constraints and availability of patients. This paper describes our preliminary system of a tracker-based echocardiogram simulator, the latest evaluation results, and future work.

Use of an Optical Scanning Device to Monitor the Progress of Noninvasive Treatments for Chest Wall Deformity: A Pilot Study.

BACKGROUND: The nonsurgical treatment of chest wall deformity by a vacuum bell or external brace is gradual, with correction taking place over months. Monitoring the progress of nonsurgical treatment of chest wall deformity has relied on the ancient methods of measuring the depth of the excavatum and the protrusion of the carinatum. Patients, who are often adolescent, may become discouraged and abandon treatment. METHODS: Optical scanning was utilized before and after the intervention to assess the effectiveness of treatment. The device measured the change in chest shape at each visit. In this pilot study, patients were included if they were willing to undergo scanning before and after treatment. Both surgical and nonsurgical treatment results were assessed. RESULTS: Scanning was successful in 7 patients. Optical scanning allowed a visually clear, precise assessment of treatment, whether by operation, vacuum bell (for pectus excavatum), or external compression brace (for pectus carinatum). Millimeter-scale differences were identified and presented graphically to patients and families. CONCLUSION: Optical scanning with the digital subtraction of images obtained months apart allows a comparison of chest shape before and after treatment. For nonsurgical, gradual methods, this allows the patient to more easily appreciate progress. We speculate that this will increase adherence to these methods in adolescent patients.

Optimization of biomathematical model predictions for cognitive performance impairment in individuals: accounting for unknown traits and uncertain states in homeostatic and circadian processes.

Current biomathematical models of fatigue and performance do not accurately predict cognitive performance for individuals with a priori unknown degrees of trait vulnerability to sleep loss, do not predict performance reliably when initial conditions are uncertain, and do not yield statistically valid estimates of prediction accuracy. These limitations diminish their usefulness for predicting the performance of individuals in operational environments. To overcome these 3 limitations, a novel modeling approach was developed, based on the expansion of a statistical technique called Bayesian forecasting. The expanded Bayesian forecasting procedure was implemented in the two-process model of sleep regulation, which has been used to predict performance on the basis of the combination of a sleep homeostatic process and a circadian process. Employing the two-process model with the Bayesian forecasting procedure to predict performance for individual subjects in the face of unknown traits and uncertain states entailed subject-specific optimization of 3 trait parameters (homeostatic build-up rate, circadian amplitude, and basal performance level) and 2 initial state parameters (initial homeostatic state and circadian phase angle). Prior information about the distribution of the trait parameters in the population at large was extracted from psychomotor vigilance test (PVT) performance measurements in 10 subjects who had participated in a laboratory experiment with 88 h of total sleep deprivation. The PVT performance data of 3 additional subjects in this experiment were set aside beforehand for use in prospective computer simulations. The simulations involved updating the subject-specific model parameters every time the next performance measurement became available, and then predicting performance 24 h ahead. Comparison of the predictions to the subjects' actual data revealed that as more data became available for the individuals at hand, the performance predictions became increasingly more accurate and had progressively smaller 95% confidence intervals, as the model parameters converged efficiently to those that best characterized each individual. Even when more challenging simulations were run (mimicking a change in the initial homeostatic state; simulating the data to be sparse), the predictions were still considerably more accurate than would have been achieved by the two-process model alone. Although the work described here is still limited to periods of consolidated wakefulness with stable circadian rhythms, the results obtained thus far indicate that the Bayesian forecasting procedure can successfully overcome some of the major outstanding challenges for biomathematical prediction of cognitive performance in operational settings.

Medical student evaluation using augmented standardized patients: new development and results.

Standardized patients (SPs), individuals who realistically portray patients, are widely used in medical education to teach and assess communication skills, eliciting a history, performing a physical exam, and other important clinical skills. They are typically healthy individuals with few or no abnormal physical findings. One limitation is that each SP can only portray a limited set of physical symptoms. We have developed a functioning prototype that uses sound-based augmented reality (AR) to expand the capabilities of an SP to exhibit physically-manifested abnormalities. The previous research and evaluation of this prototype have been published in medicine meets virtual reality conference in January 2006. Current research has combined a virtual crackle sound with a healthy SP's real breath sound at end of inspiration in real time. The technology used is intended to correlate the inspiration timing of SP's. A learner will hear this simulated sound through an electronic-stethoscope wirelessly.

Medical student evaluation using augmented standardized patients: preliminary results.

Standardized patients (SPs), individuals trained to realistically portray patients, are commonly used to teach and assess medical students. The range of clinical problems an SP can portray, however, is limited. They are typically healthy individuals with few or no abnormal physical findings. We have developed a functioning prototype that uses sound-based augmented reality to expand the capabilities of an SP to exhibit physically-manifested abnormalities. The primary purpose of this paper is to describe this prototype and report on its use in a study using medical students evaluated in a required annual Observed Structured Clinical Examination (OSCE). Presented is an overview of the prototype, a detailed description of the study, final results from the study, and conclusions drawn about the validity of using augmented SPs as a reliable medical assessment tool.

Validation of an Objective Assessment Instrument for Non-Surgical Treatments of Chest Wall Deformities.

Depending on the severity of the condition and associated risk, surgical intervention may not always be the first choice. This is true for treating chest wall deformities such as pectus excavatum and pectus carinatum. For both conditions, novel non-surgical treatments have been developed to gradually alleviate the malformation making use of the elastic nature of the costal cartilages at an early age of the patient. To quantify the performance of such treatments, this paper introduces and discusses the development of a software-based instrument that utilizes 3D chest optical images (surface scans) as input and uses registration techniques to produce an objective gauge of a patient's physical improvement after undergoing treatments. Further discussed is an experiment designed to investigate the construct validity of the developed instrument.

Automated image-guided surgery for common and complex dental implants.

Dental implantation is now recognized as a standard of care for replacing missing teeth. Pre-operative planning with patient-specific images provides the basis for precise surgery, but such accuracy is hampered to some degree because of the manual drilling procedures performed by the surgeon. In this paper, a robotic system for automated site preparation for dental implants is presented in order to provide high accuracy drilling. The results of some experiments are given to validate the system. Additionally, results are shown for jaw surgery that utilize natural-root-formed implants which can contain multiple roots. This more complex type of implant is impossible to drill manually but can provide better long-term stability and success. With this robotic system, controlled and accurate drilling was achieved, which made more advanced implant designs possible.

Developing clinically relevant aspects of the nuss procedure surgical simulator.

Surgical simulators can avail minimizing the risk of surgery and help achieving a better outcome. This is also the case for the Nuss procedure, a minimally invasive surgery for correcting pectus excavatum (PE) - a congenital chest wall deformity. A simulator can be of great benefit if it provides realistic behavior and representation of the actual surgery. In this paper, we address various clinical aspects of the procedure for a training simulation, reproducing a virtual model of the patient's thoracic cavity and internal organs with realistic textures, as well as physical behaviors. In addition, a high fidelity haptic force feedback system is constructed to provide the surgeon with a close-to-real sensation while interacting with the virtual model.

An Empirical Muscle Intracellular Action Potential Model with Multiple Erlang Probability Density Functions based on a Modified Newton Method.

The convolution of the transmembrane current of an excitable cell and a weighting function generates a single fiber action potential (SFAP) model by using the volume conductor theory. Here, we propose an empirical muscle IAP model with multiple Erlang probability density functions (PDFs) based on a modified Newton method. In addition, we generate SFAPs based on our IAP model and referent sources, and use the peak-to-peak ratios (PPRs) of SFAPs for model verification. Through this verification, we find that the relation between an IAP profile and the PPR of its SFAP is consistent with some previous studies, and our IAP model shows close profiles to the referent sources. Moreover, we simulate and discuss some possible ionic activities by using the Erlang PDFs in our IAP model, which might present the underlying activities of ions or their channels during an IAP.

Automated dental implantation using image-guided robotics: registration results.

PURPOSE: One of the most important factors affecting the outcome of dental implantation is the accurate insertion of the implant into the patient's jaw bone, which requires a high degree of anatomical accuracy. With the accuracy and stability of robots, image-guided robotics is expected to provide more reliable and successful outcomes for dental implantation. Here, we proposed the use of a robot for drilling the implant site in preparation for the insertion of the implant. METHODS: An image-guided robotic system for automated dental implantation is described in this paper. Patient-specific 3D models are reconstructed from preoperative Cone-beam CT images, and implantation planning is performed with these virtual models. A two-step registration procedure is applied to transform the preoperative plan of the implant insertion into intra-operative operations of the robot with the help of a Coordinate Measurement Machine (CMM). Experiments are carried out with a phantom that is generated from the patient-specific 3D model. Fiducial Registration Error (FRE) and Target Registration Error (TRE) values are calculated to evaluate the accuracy of the registration procedure. RESULTS: FRE values are less than 0.30 mm. Final TRE values after the two-step registration are 1.42 ± 0.70 mm (N = 5). CONCLUSIONS: The registration results of an automated dental implantation system using image-guided robotics are reported in this paper. Phantom experiments show that the practice of robot in the dental implantation is feasible and the system accuracy is comparable to other similar systems for dental implantation.

Optimized surgical tool for pectus bar extraction.

Surgeons on a daily basis improve or rescue human lives. Therefore, they should be provided with the most optimal tools so their skills are fully utilized. In this paper, we present such an optimized tool for surgeons who employ the Nuss procedure to correct pectus excavatum - a congenital chest wall deformity. The Nuss procedure is a minimally invasive procedure that results in the placement of a metal bar inside the chest cavity. The bar is removed after approximately two years. Surgeons have been reporting that the currently available tools for the bar extraction do not provide the most optimal functionality. Therefore, we have proposed an optimized and improved design of the tool for the bar extraction. The improved design tool is further analyzed using finite element techniques. Additionally, we have built a physical prototype to ensure that the new tool to seamlessly integrate with the bar and to further evaluate by the surgeons who routinely practice the Nuss procedure. In order to validate in the future the final design, we have manufactured wax models that will serve as the patterns in the casting process of metal prototypes. They should provide enough strength to withstand stresses present in the bar straightening process.