The main objective of this document is to improve precision in communication in the field of image-guided tumor ablation that leads to more accurate comparison of technologies and results and ultimately to improved patient outcomes.

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Image-guided Tumor Ablation: Standardization of Terminology and Reporting Criteria—A 10-Year Update

Photoplethysmography (PPG) is used to estimate the skin blood flow using infrared light. Researchers from different domains of science have become increasingly interested in PPG because of its advantages as non-invasive, inexpensive, and convenient diagnostic tool. Traditionally, it measures the oxygen saturation, blood pressure, cardiac output, and for assessing autonomic functions. Moreover, PPG is a promising technique for early screening of various atherosclerotic pathologies and could be helpful for regular GP-assessment but a full understanding of the diagnostic value of the different features is still lacking. Recent studies emphasise the potential information embedded in the PPG waveform signal and it deserves further attention for its possible applications beyond pulse oximetry and heart-rate calculation. Therefore, this overview discusses different types of artifact added to PPG signal, characteristic features of PPG waveform, and existing indexes to evaluate for diagnoses.

On the Analysis of Fingertip Photoplethysmogram Signals

Developing advanced surgical tools for minimally invasive procedures represents an activity of central importance to improving human health. A key challenge is in establishing biocompatible interfaces between the classes of semiconductor device and sensor technologies that might be most useful in this context and the soft, curvilinear surfaces of the body. This paper describes a solution based on materials that integrate directly with the thin elastic membranes of otherwise conventional balloon catheters, to provide diverse, multimodal functionality suitable for clinical use. As examples, we present sensors for measuring temperature, flow, tactile, optical and electrophysiological data, together with radiofrequency electrodes for controlled, local ablation of tissue. Use of such 'instrumented' balloon catheters in live animal models illustrates their operation, as well as their specific utility in cardiac ablation therapy. The same concepts can be applied to other substrates of interest, such as surgical gloves.

Materials for multifunctional balloon catheters with capabilities in cardiac electrophysiological mapping and ablation therapy

結腸癌術後の早期離床・早期経口摂取に関するProspective Randomized Trial

An apparatus for transmural ablation using an instrument containing two electrodes. The electrodes extend along the surfaces of mating jaw members which are moveable between open and clamped positions. The electrodes are connected to an RF energy source so that, when activated, they are of opposite polarity. An EKG sensor is located on one of the jaw members and spaced from the electrode so that, when the electrodes are activated to form a line of ablation, the EKG sensor contacts the tissue outside the line of ablation. A pacing electrode is located on one of the jaw members so as to be on the opposite side of the line of ablation from the EKG sensor. Thus, if the line of ablation is not transmural, the EKG sensor will be able to detect signals generated by the pacing electrode.

Transmural ablation device with EKG sensor and pacing electrode

Radiofrequency ablation is an interventional technique that in recent years has come to be employed in very different medical fields, such as the elimination of cardiac arrhythmias or the destruction of tumors in different locations. In order to investigate and develop new techniques, and also to improve those currently employed, theoretical models and computer simulations are a powerful tool since they provide vital information on the electrical and thermal behavior of ablation rapidly and at low cost. In the future they could even help to plan individual treatment for each patient. This review analyzes the state-of-the-art in theoretical modeling as applied to the study of radiofrequency ablation techniques. Firstly, it describes the most important issues involved in this methodology, including the experimental validation. Secondly, it points out the present limitations, especially those related to the lack of an accurate characterization of the biological tissues. After analyzing the current and future benefits of this technique it finally suggests future lines and trends in the research of this area.

https://link.springer.com/content/pdf/10.1186%2F1475-925X-5-24.pdf

Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future.

Purpose: Although theoretical modelling is widely used to study different aspects of radiofrequency ablation (RFA), its utility is directly related to its realism. An important factor in this realism is the use of mathematical functions to model the temperature dependence of thermal (k) and electrical (σ) conductivities of tissue. Our aim was to review the piecewise mathematical functions most commonly used for modelling the temperature dependence of k and σ in RFA computational modelling.Materials and methods: We built a hepatic RFA theoretical model of a cooled electrode and compared lesion dimensions and impedance evolution with combinations of mathematical functions proposed in previous studies. We employed the thermal damage contour D63 to compute the lesion dimension contour, which corresponds to Ω = 1, Ω being local thermal damage assessed by the Arrhenius damage model.Results: The results were very similar in all cases in terms of impedance evolution and lesion size after 6 min of ablation...

https://www.tandfonline.com/doi/pdf/10.3109/02656736.2013.807438

Review of the mathematical functions used to model the temperature dependence of electrical and thermal conductivities of biological tissue in radiofrequency ablation.

Our aim was to compare the different methods of modeling the effect of circulating blood flow on the thermal lesion dimensions created by radio frequency (RF) cardiac ablation and on the maximum blood temperature. Computational models were built to study the temperature distributions and lesion dimensions created by a nonirrigated electrode by two RF energy delivery protocols (constant voltage and constant temperature) under high and low blood flow conditions. Four methods of modeling the effect of circulating blood flow on lesion dimensions and temperature distribution were compared. Three of them considered convective coefficients at the electrode–blood and tissue–blood interfaces to model blood flow: 1) without including blood as a part of the domain; 2) constant electrical conductivity of blood; and 3) temperature-dependent electrical conductivity of blood (+2%/°C). Method 4) included blood motion and was considered to be a reference method for comparison purposes. Only Method 4 provided a realistic blood temperature distribution. The other three methods predicted lesion depth values similar to those of the reference method (differences smaller than 1 mm), regardless of ablation mode and blood flow conditions. Considering the aspects of lesion size and maximum temperature reached in blood and tissue, Method 2 seems to be the most suitable alternative to Method 4 in order to reduce the computational complexity. Our findings could have an important implication in future studies of RF cardiac ablation, in particular, in choosing the most suitable method to model the thermal effect of circulating blood.

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Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation

Epicardial radiofrequency ablation is increasingly being used for intraoperative treatment of atrial fibrillation. However, the effect of different parameters on the lesion characteristics has not been sufficiently characterized. We used a finite element model to calculate the temperature distribution in the atrial tissue under different conditions during a constant voltage radiofrequency ablation. Our simulation results show that although in the case of a thin atrium the lesion was less deep for a thin atrium, it was easier to achieve transmurality. While considering a thinner atrium, the location of the hottest point of the lesion shifted from the electrode tip to epicardial surface. This effect was due to the convective cooling of the circulating blood inside the atrium. This convective cooling phenomenon has almost negligible effects for atria thicker than 3 mm. The variability of the cooling values has no significant effect on the lesion, even for thin atria (1-2 mm). Increasing the electrode insertion depth (ID) in the tissue produced larger lesions. However, for thinner atria (thickness <2 mm), this increase in the ID reduced the lesion width. It was also proved that the presence of a fat layer between the electrode and the atrial tissue decreased significantly the lesion dimensions.

Thermal-electrical modeling for epicardial atrial radiofrequency ablation

Aortic arterial stiffness is an independent predictor of cardiovascular risk. Pulse wave velocity (PWV) is the most validated and universally accepted measure of arterial stiffness. The Digital Volume Pulse (DVP) is an accurate and non invasive method to obtain information on the pressure pulse waveform, and provides two indexes: stiffness index (SIDVP) which relates with large artery stiffness, and the reflection index (RIDVP) which relates with vascular tone. SIDVP has been previously correlated with cfPWV (carotid-femoral PWV), however, the inguinal location of the employed transducer provokes a strong psychological impact on the patients, which may reduce reproducibility. By contrast, measurement of abPWV (ankle-brachial pulse wave velocity) minimizes this psychological stress. Our aim was to evaluate the relationship among blood pressure parameters and abPWV; and the relationship among abPWV, SIDVP and RIDVP in health subjects.

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Enrique Berjano

Papers

Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future.

Review of the mathematical functions used to model the temperature dependence of electrical and thermal conductivities of biological tissue in radiofrequency ablation.

Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation

Thermal-electrical modeling for epicardial atrial radiofrequency ablation

Assessment of relationships between blood pressure, pulse wave velocity and digital volume pulse