Anti-IgG Doped Melanin Nanoparticles Functionalized Quartz Tuning Fork Immunosensors for Immunoglobulin G Detection: In Vitro and In Silico Study.

The quartz tuning fork (QTF) is a promising instrument for biosensor applications due to its advanced properties such as high sensitivity to physical quantities, cost-effectiveness, frequency stability, and high-quality factor. Nevertheless, the fork's small size and difficulty in modifying the prongs' surfaces limit its wide use in experimental research. Our study presents the development of a QTF immunosensor composed of three active layers: biocompatible natural melanin nanoparticles (MNPs), glutaraldehyde (GLU), and anti-IgG layers, for the detection of immunoglobulin G (IgG). Frequency shifts of QTFs after MNP functionalization, GLU activation, and anti-IgG immobilization were measured with an Asensis QTF F-master device. Using QTF immunosensors that had been modified under optimum conditions, the performance of QTF immunosensors for IgG detection was evaluated. Accordingly, a finite element method (FEM)-based model was produced using the COMSOL Multiphysics software program (COMSOL License No. 2102058) to simulate the effect of deposited layers on the QTF resonance frequency. The experimental results, which demonstrated shifts in frequency with each layer during QTF surface functionalization, corroborated the simulation model predictions. A modelling error of 0.05% was observed for the MNP-functionalized QTF biosensor compared to experimental findings. This study validated a simulation model that demonstrates the advantages of a simulation-based approach to optimize QTF biosensors, thereby reducing the need for extensive laboratory work.

Performance Monitoring via Functional Near Infrared Spectroscopy for Virtual Reality Based Basic Life Support Training.

The use of serious game tools in training of medical professions is steadily growing. However, there is a lack of reliable performance assessment methods to evaluate learner's outcome. The aim of this study is to determine whether functional near infrared spectroscopy (fNIRS) can be used as an additional tool for assessing the learning outcome of virtual reality (VR) based learning modules. The hypothesis is that together with an improvement in learning outcome there would be a decrease in the participants' cerebral oxygenation levels measured from the prefrontal cortex (PFC) region and an increase of participants' serious gaming results. To test this hypothesis, the subjects were recruited and divided into four groups with different combinations of prior virtual reality experience and prior Basic Life Support (BLS) knowledge levels. A VR based serious gaming module for teaching BLS and 16-Channel fNIRS system were used to collect data from the participants. Results of the participants' scores acquired from the serious gaming module were compared with fNIRS measures on the initial and final training sessions. Kruskal Wallis test was run to determine any significant statistical difference between the groups and Mann-Whitney U test was utilized to obtain pairwise comparisons. BLS training scores of the participants acquired from VR based serious game's the learning management system and fNIRS measurements revealed decrease in use of resources from the PFC, but increase in behavioral performance. Importantly, brain-based measures can provide an additional quantitative metric for trainee's expertise development and can assist the medical simulation instructors.

Thin film based semi-active resonant marker design for low profile interventional cardiovascular MRI devices.

OBJECTIVES: A new microfabrication method to produce low profile radio frequency (RF) resonant markers on catheter shafts was developed. A semi-active RF resonant marker incorporating a solenoid and a plate capacitor was constructed on the distal shaft of a 5 Fr guiding catheter. The resulting device can be used for interventional cardiovascular MRI procedures. MATERIALS AND METHODS: Unlike current semi-active device visualization techniques that require rigid and bulky analog circuit components (capacitor and solenoid), we fabricated a low profile RF resonant marker directly on guiding the catheter surface by thin film metal deposition and electroplating processes using a modified physical vapor deposition system. RESULTS: The increase of the overall device profile thickness caused by the semi-active RF resonant marker (130 µm thick) was lowered by a factor of 4.6 compared with using the thinnest commercial non-magnetic and rigid circuit components (600 µm thick). Moreover, adequate visibility performance of the RF resonant marker in different orientations and overall RF safety were confirmed through in vitro experiments under MRI successfully. CONCLUSION: The developed RF resonant marker on a clinical grade 5 Fr guiding catheter will enable several interventional congenital heart disease treatment procedures under MRI.

Simultaneous mapping of endocardium and epicardium from multielectrode intrachamber and intravenous catheters: a computer simulation-based validation.

A multielectrode basket-shaped contact catheter (MBC) provides simultaneous recordings of unipolar or bipolar electrograms from within the heart chambers. Another catheter-based mapping approach uses the multielectrode intravenous catheters (MIVCs), which are widely used to diagnose and treat supraventricular arrhythmias. It is also known that mapping techniques are usually limited to one surface at a time. Therefore, an approach that can be used for simultaneous mapping of left and right endocardial surfaces and epicardial surface will be beneficial to characterize and discriminate the endocardial and epicardial sources of the arrhythmias more accurately. In this study, we used statistical estimation method to map the endocardial and epicardial surfaces simultaneously based on combined usage of the MBC and MIVC. The statistical estimation method is based on high-resolution training data set to hypothesize the relationship between catheter measurements and inaccessible sites. To test this approach, we created a high-resolution map database consisting of computer simulation results of Aliev-Panfilov model of cardiac electrical activity on 3-dimensional Auckland canine heart geometry. The simulation database included 2590 maps each paced from a unique endocardial or epicardial site. Fifty or five percent of the database was used as the training data set and the remaining as test data set in the statistical estimation procedure. We selected 64 sites on the left and 64 on the right endocardial surfaces of the model heart geometry and used them as the surrogate MBC measurement sites. Ninety-one sites on the epicardium corresponding to the major coronary veins served as the surrogate MIVC leads. Finally, we tested the success of the method to determine the source of the arrhythmias using the correlation coefficient between the original and estimated activation maps and linear distance between their earliest activated sites. The performance of this approach was promising, such as when MBC on the left endocardium and MIVC were used together, the average linear distance was approximately 2.4 mm and mean correlation coefficient was 0.995. It was possible to locate 95% of epicardial arrhythmia cases correctly on the epicardium. Ninety-nine percent of left endocardially originating arrhythmias were correctly located on the left endocardium. The results of this study showed that this approach is feasible and requires further effort.

Usage of cardiac simulation results in source localization of focal epicardial arrhythmias using statistical estimation.

Mapping of the epicardium is possible with the usage of multielectrode venous catheters; however, most of epicardial surface is still inaccessible. To overcome this problem a method called statistical estimation was proposed, in which the relationship between catheter measurements and the remaining sites are created from previously obtained high resolution maps, called the training set. Thus, there is a need for the acquisition of high resolution epicardial maps from patients during open-chest procedures. In this study we hypothesize that epicardial maps created from computer simulations might be used in combination with maps from patients, so that the need for data acquisition during open-chest procedures would be reduced. We used high-resolution epicardial activation maps acquired from 13 dog heart experiments, 470 maps from 12 experiments (training set) and 50 maps from a separate experiment (test set). Hearts were paced from sites regularly distributed over the epicardium. The simulations of focal arrhythmias originating from epicardium were performed using a modified version of FitzHugh-Nagumo cardiac model within the ventricles of the Auckland canine heart model. We registered the experimental and simulation heart geometries using iterative closest-points algorithm and procrustes method. We started simulations from sites that corresponded to the pacing sites on the experimental geometry and created a simulated activation map database (470 maps) and compared the simulation results with the corresponding experimental maps. Finally, we performed the statistical estimation on the test set by adjusting the content of the training set in such a way that simulated maps constituted 100%, 75%, 50%, 25%, and 0% of the training set. Mean correlation coefficient (CC) between the simulated and experimental activation maps was 0.88. Mean CC and the arrhythmia source localization error worsened only from 0.93 to 0.92, and 9.65 mm to 12.14 mm when simulated activation maps constituted 50% of the training set. This study showed the feasibility of including cardiac simulation results in the training set for source localization of focal epicardial arrhythmias using statistical estimation.