Vaibhav Patil

Evaluation of colonoscopy technical skill levels by use of an objective kinematic-based system.

BACKGROUND Colonoscopy requires training and experience to ensure accuracy and safety. Currently, no objective, validated process exists to determine when an endoscopist has attained technical competence. Kinematics data describing movements of laparoscopic instruments have been used in surgical skill assessment to define expert surgical technique. We have developed a novel system to record kinematics data during colonoscopy and quantitatively assess colonoscopist performance. OBJECTIVE To use kinematic analysis of colonoscopy to quantitatively assess endoscopic technical performance. DESIGN Prospective cohort study. SETTING Tertiary-care academic medical center. POPULATION This study involved physicians who perform colonoscopy. INTERVENTION Application of a kinematics data collection system to colonoscopy evaluation. MAIN OUTCOME MEASUREMENTS Kinematics data, validated task load assessment instrument, and technical difficulty visual analog scale. RESULTS All 13 participants completed the colonoscopy to the terminal ileum on the standard colon model. Attending physicians reached the terminal ileum quicker than fellows (median time, 150.19 seconds vs 299.86 seconds; p<.01) with reduced path lengths for all 4 sensors, decreased flex (1.75 m vs 3.14 m; P=.03), smaller tip angulation, reduced absolute roll, and lower curvature of the endoscope. With performance of attending physicians serving as the expert reference standard, the mean kinematic score increased by 19.89 for each decrease in postgraduate year (P<.01). Overall, fellows experienced greater mental, physical, and temporal demand than did attending physicians. LIMITATION Small cohort size. CONCLUSION Kinematic data and score calculation appear useful in the evaluation of colonoscopy technical skill levels. The kinematic score appears to consistently vary by year of training. Because this assessment is nonsubjective, it may be an improvement over current methods for determination of competence. Ongoing studies are establishing benchmarks and characteristic profiles of skill groups based on kinematics data.

Optimal spatial design of non-invasive magnetic field-based localization systems

Magnetic localization systems based on passive permanent magnets (PM) are of great interest due to their ability to provide non-contact sensing and without any power requirement for the PM. Medical procedures such as ventriculostomy can benefit greatly from real-time feedback of the inserted catheter tip. While the effects of the number of sensors on the localization accuracy in such systems has been reported, the spatial design of the sensor layout has been largely overlooked. Here in this paper, a framework for determining an optimal sensor assembly for enhanced localization performance is presented and investigated through numerical simulations and direct experiments. Two approaches are presented: one based on structured grid configuration and the other derived using Genetic Algorithms. Simulation results verified by experiments strongly suggest that the layout of the sensors not only has an effect on the localization accuracy, but also has an effect far more pronounced than improvements brought by increasing the number of sensors.

Image Registered Gastroscopic Ultrasound (IRGUS) in human subjects: a pilot study to assess feasibility

BACKGROUND AND STUDY AIMS Endoscopic ultrasound (EUS) is a complex procedure due to the subtleties of ultrasound interpretation, the small field of observation, and the uncertainty of probe position and orientation. Animal studies demonstrated that Image Registered Gastroscopic Ultrasound (IRGUS) is feasible and may be superior to conventional EUS in efficiency and image interpretation. This study explores whether these attributes of IRGUS will be evident in human subjects, with the aim of assessing the feasibility, effectiveness, and efficiency of IRGUS in patients with suspected pancreatic lesions. PATIENTS AND METHODS This was a prospective feasibility study at a tertiary care academic medical center in human patients with pancreatic lesions on computed tomography (CT) scan. Patients who were scheduled to undergo conventional EUS were randomly chosen to undergo their procedure with IRGUS. Main outcome measures included feasibility, ease of use, system function, validated task load (TLX) assessment instrument, and IRGUS experience questionnaire. RESULTS Five patients underwent IRGUS without complication. Localization of pancreatic lesions was accomplished efficiently and accurately (TLX temporal demand 3.7 %; TLX effort 8.6 %). Image synchronization and registration was accomplished in real time without procedure delay. The mean assessment score for endoscopist experience with IRGUS was positive (66.6 ± 29.4). Real-time display of CT images in the EUS plane and echoendoscope orientation were the most beneficial characteristics. CONCLUSIONS IRGUS appears feasible and safe in human subjects, and efficient and accurate at identification of probe position and image interpretation. IRGUS has the potential to broaden the adoption of EUS techniques and shorten EUS learning curves. Clinical studies comparing IRGUS with conventional EUS are ongoing.

Design Optimization of a Magnetic Field-Based Localization Device for Enhanced Ventriculostomy

The accuracy of many freehand medical procedures can be improved with assistance from real-time localization. Magnetic localization systems based on harnessing passive permanent magnets (PMs) are of great interest to track objects inside the body because they do not require a powered source and provide noncontact sensing without the need for line-of-sight. While the effect of the number of sensors on the localization accuracy in such systems has been reported, the spatial design of the sensing assembly is an open problem. This paper presents a systematic approach to determine an optimal spatial sensor configuration for localizing a PM during a medical procedure. Two alternative approaches were explored and compared through numerical simulations and experimental investigation: one based on traditional grid configuration and the other derived using genetic algorithms (GAs). Our results strongly suggest that optimizing the spatial arrangement has a larger influence on localization performance than increasing the number of sensors in the assembly. We found that among all the optimization schemes, the approach utilizing GA produced sensor designs with the smallest localization errors.

Smart Stylet: The Development and Use of a Bedside External Ventricular Drain Image-Guidance System

Background: Placement accuracy of ventriculostomy catheters is reported in a wide and variable range. Development of an efficient image-guidance system may improve physician performance and patient safety. Objective: We evaluate the prototype of Smart Stylet, a new electromagnetic image-guidance system for use during bedside ventriculostomy. Methods: Accuracy of the Smart Stylet system was assessed. System operators were evaluated for their ability to successfully target the ipsilateral frontal horn in a phantom model. Results: Target registration error across 15 intracranial targets ranged from 1.3 to 4.6 mm (mean 3.1 mm). Using Smart Stylet guidance, a test operator successfully passed a ventriculostomy catheter to a shifted ipsilateral frontal horn 20/20 (100%) times from the frontal approach in a skull phantom. Without Smart Stylet guidance, the operator was successful 4/10 (40%) times from the right frontal approach and 6/10 (60%) times from the left frontal approach. In a separate experiment, resident operators were successful 2/4 (50%) times when targeting the shifted ipsilateral frontal horn with Smart Stylet guidance and 0/4 (0%) times without image guidance using a skull phantom. Conclusions: Smart Stylet may improve the ability to successfully target the ventricles during frontal ventriculostomy.

Hidden Markov model for quantifying clinician expertise in flexible instrument manipulation

Clinicians are trained to manipulate a colonoscope while minimizing the force exerted on the colon walls to reduce the danger of luminal perforation and discomfort to the patient. Here, we classify the expertise of the clinician performing colonoscopy using a Hidden Markov Model. Seven models are trained corresponding to the performance of the expert in the entire colon, ascending, transverse and descending colon and three gestures corresponding to roll and two angulations of the distal end of the scope. Experimental results in a colon model (CM-1, Olympus, Tokyo, Japan) are shown to compare the performance of the four groups of users - first year, second year and third year GI residents and expert physicians.