The hemodynamic cardiac profiler volume-time curves and related parameters: an MRI validation study.

The hemodynamic cardiac profiler (HCP) is a new, non-invasive, operator-independent screening tool that uses six independent electrode pairs on the frontal thoracic skin, and a low-intensity, patient-safe, high-frequency applied alternating current to measure ventricular volume dynamics during the cardiac cycle for producing ventricular volume-time curves (VTCs).To validate VTCs from HCP against VTCs from MRI in healthy volunteers.Left- and right-ventricular VTCs were obtained by HCP and MRI in six healthy participants in supine position.

Bedside visualisation tool for prediction of deviation from intended dosage in multi-infusion therapy.

Background: In multi-infusion therapy, multiple infusion pumps are connected to one single vascular access point. Interaction between pressure changes from different pumps may result in temporary dosing errors, which can be very harmful to the patient. It is known that these dosing errors occur.

Unexpected dosing errors due to air bubbles in infusion lines with and without air filters.

The effect of the presence of an air bubble, inside an infusion line, on the time (Tnew) needed for a new medication to reach the patient after a syringe exchange was studied in this paper. If an air bubble escapes through an air filter, then a sudden drop in pressure occurs, causing a relaxation of the compressible part of the syringe, followed by a gradual restoration of the flow rate in the line. We modeled this phenomenon mathematically and measured it experimentally .

Effect of non-return valves on the time-of-arrival of new medication in a patient after syringe exchange in an infusion set-up.

The presence of a non-return valve in an infusion set-up is expected to affect the time-of-arrival of new medication in a patient after syringe exchange. Using Computational Fluid Dynamics (CFD) we have studied the flow through a typical non-return valve, focusing on two separate effects: (A) the overall delay in the time-of-arrival, and (B) timing effects due to the distortion of the Poiseuille flow profile in the non-return valve. The results show that (A) the additional delay in time-of-arrival of new medication, caused by the non-return valve alone, corresponds to the delay that would be caused by 11.

High-frequency irreversible electroporation for cardiac ablation using an asymmetrical waveform.

Background: Irreversible electroporation (IRE) using direct current (DC) is an effective method for the ablation of cardiac tissue. A major drawback of the use of DC-IRE, however, are two problems: requirement of general anesthesia due to severe muscle contractions and the formation of bubbles containing gaseous products from electrolysis. The use of high-frequency alternating current (HF-IRE) is expected to solve both problems, because HF-IRE produces little to no muscle spasms and does not cause electrolysis.

Non-invasive measurement of volume-time curves in patients with mitral regurgitation and in healthy volunteers, using a new operator-independent screening tool.

Left ventricular volume-time curves (VTCs) provide hemodynamic data, and may help clinical decision making. The generation of VTCs using echocardiography, however, is time-consuming and prone to inter-operator variability. In this study, we used a new non-invasive, operator-independent technique, the hemodynamic cardiac profiler (HCP), to generate VTCs.

Analytical method for calculation of deviations from intended dosages during multi-infusion.

Background: In this paper, a new method is presented that combines mechanical compliance effects with Poiseuille flow and push-out effects ("dead volume") in one single mathematical framework for calculating dosing errors in multi-infusion set-ups. In contrast to existing numerical methods, our method produces explicit expressions that illustrate the mathematical dependencies of the dosing errors on hardware parameters and pump flow rate settings.

Methods: Our new approach uses the Z-transform to model the contents of the catheter, and after implementation in Mathematica (Wolfram), explicit expressions are produced automatically.

Irreversible Electroporation of the Pancreas Using Parallel Plate Electrodes in a Porcine Model: A Feasibility Study.

Background: Irreversible electroporation (IRE) with needle electrodes is being explored as treatment option in locally advanced pancreatic cancer. Several studies have shown promising results with IRE needles, positioned around the tumor to achieve tumor ablation. Disadvantages are the technical difficulties for needle placement, the time needed to achieve tumor ablation, the risk of needle track seeding and most important the possible occurrence of postoperative pancreatic fistula via the needle tracks.

Flow variability and its physical causes in infusion technology: a systematic review of in vitro measurement and modeling studies.

Infusion therapy is medically and technically challenging and frequently associated with medical errors. When administering pharmaceuticals by means of infusion, dosing errors can occur due to flow rate variability. These dosing errors may lead to adverse effects.

How physical infusion system parameters cause clinically relevant dose deviations after setpoint changes.

Multi-infusion therapy, in which multiple pumps are connected to one access point, is frequently used in patient treatments. This practice is known to cause dosing errors following setpoint changes in the drug concentrations that actually enter the patients. Within the Metrology for Drug Delivery Project, we analyzed and quantified the two main physical phenomena leading to these errors: the "push-out" effect and the system mechanical compliance.

Correct positioning of central venous catheters using a new electric method.

Purpose: In order to find the correct final position of the tip of a central venous catheter, we have developed a new electric method (the Proximity of Cardiac Motion (PCM) method), designed to work in tandem with the existing ECG-based method.

Methods: A small, patient-safe, high-frequency current is fed through the catheter (via the saline-filled lumen of the catheter, or a stylet). Simultaneously, the resulting voltage is measured by two electrodes on the frontal thoracic skin.

A new electric method for non-invasive continuous monitoring of stroke volume and ventricular volume-time curves.

Background: In this paper a new non-invasive, operator-free, continuous ventricular stroke volume monitoring device (Hemodynamic Cardiac Profiler, HCP) is presented, that measures the average stroke volume (SV) for each period of 20 seconds, as well as ventricular volume-time curves for each cardiac cycle, using a new electric method (Ventricular Field Recognition) with six independent electrode pairs distributed over the frontal thoracic skin. In contrast to existing non-invasive electric methods, our method does not use the algorithms of impedance or bioreactance cardiography. Instead, our method is based on specific 2D spatial patterns on the thoracic skin, representing the distribution, over the thorax, of changes in the applied current field caused by cardiac volume changes during the cardiac cycle.

In-vivo validation of a new non-invasive continuous ventricular stroke volume monitoring system in an animal model.

Introduction: Recently, a non-invasive, continuous ventricular stroke volume monitoring system using skin electrodes has been developed. In contrast to impedance-based methods, the new technique (ventricular field recognition) enables measurement of changes in ventricular volume. A prototype using this new method was built (the hemologic cardiac profiler, HCP) and validated against a reference method in a pig model during variations in cardiac output.

Temperature-induced tissue susceptibility changes lead to significant temperature errors in PRFS-based MR thermometry during thermal interventions.

Proton resonance frequency shift-based MR thermometry (MRT) is hampered by temporal magnetic field changes. Temporal changes in the magnetic susceptibility distribution lead to nonlocal field changes and are, therefore, a possible source of errors. The magnetic volume susceptibility of tissue is temperature dependent.

Assessment of stroke volume index with three different bioimpedance algorithms: lack of agreement compared to thermodilution.

Objective: The accuracy of bioimpedance stroke volume index (SVI) is questionable as studies report inconsistent results. It remains unclear whether the algorithms alone are responsible for these findings. We analyzed the raw impedance data with three algorithms and compared bioimpedance SVI to transpulmonary thermodilution (SVI(TD)).

Robustness and complexity of a minimally invasive vascular intervention simulation system.

Minimally invasive vascular interventions offer advantages over open surgery. Thorough training is needed to master the skills required to correctly perform these minimally invasive interventions. Simulation is becoming a potential alternative for training.

Modeling friction, intrinsic curvature, and rotation of guide wires for simulation of minimally invasive vascular interventions.

Obtaining the expertise to perform minimally invasive vascular interventions requires thorough training. In this paper, an algorithm for simulating minimally invasive vascular interventions for training purposes is presented and evaluated. The algorithm enables the simulation of completely straight guide wires as well as intrinsically curved ones based on applied translations and rotations.

A new method for spatially selective, non-invasive activation of neurons: concept and computer simulation.

Currently available non-invasive neurostimulation devices, using skin electrodes or externally applied magnetic coils, are not capable of producing a local stimulation maximum deep inside a homogeneous conductor, because of a fundamental limitation inherent to the Laplace equation. In this paper, a new neurostimulation method (the DeepFocus method) is presented, which avoids this limitation by using an indirect method of producing electric currents inside tissues: First, cylinder-shaped ferromagnetic rotating disks of non-permanent magnetic material are placed near the skin and magnetized by a non-rotating magnetic coil. Each of the disks rotates at high speed around its own axis of symmetry, thus producing a purely electric Lorentz force field having a non-zero divergence outside the disk, and therefore giving rise to charge accumulations inside the tissues.

Simulation of minimally invasive vascular interventions for training purposes.

Objective: To master the skills required to perform minimally invasive vascular interventions, proper training is essential. A computer simulation environment has been developed to provide such training. The simulation is based on an algorithm specifically developed to simulate the motion of a guide wire--the main instrument used during these interventions--in the human vasculature.