Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models

Purpose: To assess whether tailoring the Kp and Ki values of a proportional-integral (PI) controller during radiofrequency (RF) cardiac ablation could be advantageous from the point of view of the dynamic behaviour of the controller, in particular, whether control action could be speeded up and larger lesions obtained. Methods: Theoretical models were built and solved by the finite element method. RF cardiac ablations were simulated with temperature controlled at 55 degrees C. Specific PI controllers were implemented with Kp and Ki parameters adapted to cases with different tissue values (specific heat, thermal conductivity and electrical conductivity) electrode-tissue contact characteristics (insertion depth, cooling effect of circulating blood) and electrode characteristics (size, location and arrangement of the temperature sensor in the electrode). Results: The lesion dimensions and T(max) remained almost unchanged when the specific PI controller was used instead of one tuned for the standard case: T(max) varied less than 1.9 degrees C, lesion width less than 0.2 mm, and lesion depth less than 0.3 mm. As expected, we did observe a direct logical relationship between the response time of each controller and the transient value of electrode temperature. Conclusion: The results suggest that a PI controller designed for a standard case (such as that described in this study), could offer benefits under different tissue conditions, electrode-tissue contact, and electrode characteristics.This work received financial support from the Spanish 'Plan Nacional de I+D+I del Ministerio de Ciencia e Innovacion' Grant no. TEC2008-01369/TEC and FEDER Project MTM2010-14909. The translation of this paper was funded by the Universitat Politecnica de Valencia, Spain. The authors alone are responsible for the content and writing of the paperAlba Martínez, J.; Trujillo Guillen, M.; Blasco Giménez, RM.; Berjano Zanón, E. (2011). Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models. International Journal of Hyperthermia. 27(6):539-548. https://doi.org/10.3109/02656736.2011.586665S539548276Gaita, F., Caponi, D., Pianelli, M., Scaglione, M., Toso, E., Cesarani, F., … Leclercq, J. F. (2010). Radiofrequency Catheter Ablation of Atrial Fibrillation: A Cause of Silent Thromboembolism? Circulation, 122(17), 1667-1673. doi:10.1161/circulationaha.110.937953Anfinsen, O.-G., Aass, H., Kongsgaard, E., Foerster, A., Scott, H., & Amlie, J. P. (1999). Journal of Interventional Cardiac Electrophysiology, 3(4), 343-351. doi:10.1023/a:1009840004782PETERSEN, H. H., CHEN, X., PIETERSEN, A., SVENDSEN, J. H., & HAUNSO, S. (2000). Tissue Temperatures and Lesion Size During Irrigated Tip Catheter Radiofrequency Ablation: An In Vitro Comparison of Temperature-Controlled Irrigated Tip Ablation, Power-Controlled Irrigated Tip Ablation, and Standard Temperature-Controlled Ablation. Pacing and Clinical Electrophysiology, 23(1), 8-17. doi:10.1111/j.1540-8159.2000.tb00644.xTungjitkusolmun, S., Woo, E. J., Cao, H., Tsai, J. Z., Vorperian, V. R., & Webster, J. G. (2000). Thermal—electrical finite element modelling for radio frequency cardiac ablation: Effects of changes in myocardial properties. Medical & Biological Engineering & Computing, 38(5), 562-568. doi:10.1007/bf02345754Lai, Y.-C., Choy, Y. B., Haemmerich, D., Vorperian, V. R., & Webster, J. G. (2004). Lesion Size Estimator of Cardiac Radiofrequency Ablation at Different Common Locations With Different Tip Temperatures. IEEE Transactions on Biomedical Engineering, 51(10), 1859-1864. doi:10.1109/tbme.2004.831529Jain, M. K., & Wolf, P. D. (1999). Temperature-controlled and constant-power radio-frequency ablation: what affects lesion growth? IEEE Transactions on Biomedical Engineering, 46(12), 1405-1412. doi:10.1109/10.804568Panescu, D., Whayne, J. G., Fleischman, S. D., Mirotznik, M. S., Swanson, D. K., & Webster, J. G. (1995). Three-dimensional finite element analysis of current density and temperature distributions during radio-frequency ablation. IEEE Transactions on Biomedical Engineering, 42(9), 879-890. doi:10.1109/10.412649Hong Cao, Vorperian, V. R., Tungjitkusolmun, S., Jan-Zern Tsai, Haemmerich, D., Young Bin Choy, & Webster, J. G. (2001). Flow effect on lesion formation in RF cardiac catheter ablation. IEEE Transactions on Biomedical Engineering, 48(4), 425-433. doi:10.1109/10.915708Tungjitkusolmun, S., Vorperian, V. R., Bhavaraju, N., Cao, H., Tsai, J.-Z., & Webster, J. G. (2001). Guidelines for predicting lesion size at common endocardial locations during radio-frequency ablation. IEEE Transactions on Biomedical Engineering, 48(2), 194-201. doi:10.1109/10.909640Schutt, D., Berjano, E. J., & Haemmerich, D. (2009). Effect of electrode thermal conductivity in cardiac radiofrequency catheter ablation: A computational modeling study. International Journal of Hyperthermia, 25(2), 99-107. doi:10.1080/02656730802563051Langberg, J. J., Calkins, H., el-Atassi, R., Borganelli, M., Leon, A., Kalbfleisch, S. J., & Morady, F. (1992). Temperature monitoring during radiofrequency catheter ablation of accessory pathways. Circulation, 86(5), 1469-1474. doi:10.1161/01.cir.86.5.1469Calkins, H., Prystowsky, E., Carlson, M., Klein, L. S., Saul, J. P., & Gillette, P. (1994). Temperature monitoring during radiofrequency catheter ablation procedures using closed loop control. Atakr Multicenter Investigators Group. Circulation, 90(3), 1279-1286. doi:10.1161/01.cir.90.3.1279Lennox CD, Temperature controlled RF coagulation. Patent number: 5.122.137 Hudson NHEdwards SD, Stern RA, Electrode and associated system using thermally insulated temperature sensing elements. Patent number: US Patent 5,456,682Panescu D, Fleischman SD, Whayne JG, Swanson DK, (EP Technology. Effects of temperature sensor placement on performance of temperature-controlled ablation. IEEE 17th Annual Conference, Engineering in Medicine and Biology Society, Montreal, Canada (1995)BLOUIN, L. T., MARCUS, F. I., & LAMPE, L. (1991). Assessment of Effects of a Radiofrequency Energy Field and Thermistor Location in an Electrode Catheter on the Accuracy of Temperature Measurement. Pacing and Clinical Electrophysiology, 14(5), 807-813. doi:10.1111/j.1540-8159.1991.tb04111.xBerjano, E. J. (2006). BioMedical Engineering OnLine, 5(1), 24. doi:10.1186/1475-925x-5-24Bhavaraju, N. C., Cao, H., Yuan, D. Y., Valvano, J. W., & Webster, J. G. (2001). Measurement of directional thermal properties of biomaterials. IEEE Transactions on Biomedical Engineering, 48(2), 261-267. doi:10.1109/10.909647Hong Cao, Tungjitkusolmun, S., Young Bin Choy, Jang-Zern Tsai, Vorperian, V. R., & Webster, J. G. (2002). Using electrical impedance to predict catheter-endocardial contact during RF cardiac ablation. IEEE Transactions on Biomedical Engineering, 49(3), 247-253. doi:10.1109/10.983459PETERSEN, H. H., & SVENDSEN, J. H. (2003). Can Lesion Size During Radiofrequency Ablation Be Predicted By the Temperature Rise to a Low Power Test Pulse in Vitro? Pacing and Clinical Electrophysiology, 26(8), 1653-1659. doi:10.1046/j.1460-9592.2003.t01-1-00248.xLANGBERG, J. J., LEE, M. A., CHIN, M. C., & ROSENQVIST, M. (1990). Radiofrequency Catheter Ablation: The Effect of Electrode Size on Lesion Volume In Vivo. Pacing and Clinical Electrophysiology, 13(10), 1242-1248. doi:10.1111/j.1540-8159.1990.tb02022.

Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies

Low convergence ratio implosions (where wetted-foam layers are used to limit capsule convergence, achieving improved robustness to instability growth) and auxiliary heating (where electron beams are used to provide collisionless heating of a hotspot) are two promising techniques that are being explored for inertial fusion energy applications. In this paper, a new analytic study is presented to understand and predict the performance of these implosions. Firstly, conventional gain models are adapted to produce gain curves for fixed convergence ratios, which are shown to well-describe previously simulated results. Secondly, auxiliary heating is demonstrated to be well understood and interpreted through the burn-up fraction of the deuterium-tritium fuel, with the gradient of burn-up with respect to burn-averaged temperature shown to provide good qualitative predictions of the effectiveness of this technique for a given implosion. Simulations of auxiliary heating for a range of implosions are presented in support of this and demonstrate that this heating can have significant benefit for high gain implosions, being most effective when the burn-averaged temperature is between 5 and 20 keV

Thermal modeling of lesion growth with radiofrequency ablation devices

BACKGROUND: Temperature is a frequently used parameter to describe the predicted size of lesions computed by computational models. In many cases, however, temperature correlates poorly with lesion size. Although many studies have been conducted to characterize the relationship between time-temperature exposure of tissue heating to cell damage, to date these relationships have not been employed in a finite element model. METHODS: We present an axisymmetric two-dimensional finite element model that calculates cell damage in tissues and compare lesion sizes using common tissue damage and iso-temperature contour definitions. The model accounts for both temperature-dependent changes in the electrical conductivity of tissue as well as tissue damage-dependent changes in local tissue perfusion. The data is validated using excised porcine liver tissues. RESULTS: The data demonstrate the size of thermal lesions is grossly overestimated when calculated using traditional temperature isocontours of 42°C and 47°C. The computational model results predicted lesion dimensions that were within 5% of the experimental measurements. CONCLUSION: When modeling radiofrequency ablation problems, temperature isotherms may not be representative of actual tissue damage patterns

Factors affecting recruitment and retention of community health workers in a newborn care intervention in Bangladesh

<p>Abstract</p> <p>Background</p> <p>Well-trained and highly motivated community health workers (CHWs) are critical for delivery of many community-based newborn care interventions. High rates of CHW attrition undermine programme effectiveness and potential for implementation at scale. We investigated reasons for high rates of CHW attrition in Sylhet District in north-eastern Bangladesh.</p> <p>Methods</p> <p>Sixty-nine semi-structured questionnaires were administered to CHWs currently working with the project, as well as to those who had left. Process documentation was also carried out to identify project strengths and weaknesses, which included in-depth interviews, focus group discussions, review of project records (i.e. recruitment and resignation), and informal discussion with key project personnel.</p> <p>Results</p> <p>Motivation for becoming a CHW appeared to stem primarily from the desire for self-development, to improve community health, and for utilization of free time. The most common factors cited for continuing as a CHW were financial incentive, feeling needed by the community, and the value of the CHW position in securing future career advancement. Factors contributing to attrition included heavy workload, night visits, working outside of one's home area, familial opposition and dissatisfaction with pay.</p> <p>Conclusions</p> <p>The framework presented illustrates the decision making process women go through when deciding to become, or continue as, a CHW. Factors such as job satisfaction, community valuation of CHW work, and fulfilment of pre-hire expectations all need to be addressed systematically by programs to reduce rates of CHW attrition.</p

Identification of Genes Required for Neural-Specific Glycosylation Using Functional Genomics

Glycosylation plays crucial regulatory roles in various biological processes such as development, immunity, and neural functions. For example, α1,3-fucosylation, the addition of a fucose moiety abundant in Drosophila neural cells, is essential for neural development, function, and behavior. However, it remains largely unknown how neural-specific α1,3-fucosylation is regulated. In the present study, we searched for genes involved in the glycosylation of a neural-specific protein using a Drosophila RNAi library. We obtained 109 genes affecting glycosylation that clustered into nine functional groups. Among them, members of the RNA regulation group were enriched by a secondary screen that identified genes specifically regulating α1,3-fucosylation. Further analyses revealed that an RNA–binding protein, second mitotic wave missing (Swm), upregulates expression of the neural-specific glycosyltransferase FucTA and facilitates its mRNA export from the nucleus. This first large-scale genetic screen for glycosylation-related genes has revealed novel regulation of fucTA mRNA in neural cells

TRY plant trait database - enhanced coverage and open access

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

'A foundation-hatched black elite’: Obama, the US establishment and foreign policy

US foreign policy has a largely unacknowledged racial dimension due to the racial characteristics of the US foreign policy establishment, and in shared mindsets in a soon-to-be ‘majority-minority’ nation. White Anglo-Saxon Protestant (WASP) racial-ethnic and class factors produce managed change through socialisation in an attenuated meritocratic order, adapting to challenges to elite dominance by incorporating rising talent, without altering broader patterns of power. The greatest success of such a system would be the assimilation of the most elite minority individuals, even as the bulk of those groups’ members continue to experience discrimination. Such success would be compounded by election to the highest office of a minority US president extolling the virtues of post-racial politics. President Barack Obama represents a ‘Wasp-ified’ black elite, assimilated into the extant structures of power that remain wedded to a more secular, non-biologically-racial, version of Anglo-Saxonism or, more broadly, liberal internationalism. Hence, it should occasion little surprise that there has been so little change in US foreign policies during Obama’s two-term presidency

Under-Five Mortality in High Focus States in India: A District Level Geospatial Analysis

<div><h3>Background</h3><p>This paper examines if, when controlling for biophysical and geographical variables (including rainfall, productivity of agricultural lands, topography/temperature, and market access through road networks), socioeconomic and health care indicators help to explain variations in the under-five mortality rate across districts from nine high focus states in India. The literature on this subject is inconclusive because the survey data, upon which most studies of child mortality rely, rarely include variables that measure these factors. This paper introduces these variables into an analysis of 284 districts from nine high focus states in India.</p> <h3>Methodology/Principal Findings</h3><p>Information on the mortality indicator was accessed from the recently conducted Annual Health Survey of 2011 and other socioeconomic and geographic variables from Census 2011, District Level Household and Facility Survey (2007–08), Department of Economics and Statistics Divisions of the concerned states. Displaying high spatial dependence (spatial autocorrelation) in the mortality indicator (outcome variable) and its possible predictors used in the analysis, the paper uses the Spatial-Error Model in an effort to negate or reduce the spatial dependence in model parameters. The results evince that the coverage gap index (a mixed indicator of district wise coverage of reproductive and child health services), female literacy, urbanization, economic status, the number of newborn care provided in Primary Health Centers in the district transpired as significant correlates of under-five mortality in the nine high focus states in India. The study identifies three clusters with high under-five mortality rate including 30 districts, and advocates urgent attention.</p> <h3>Conclusion</h3><p>Even after controlling the possible biophysical and geographical variables, the study reveals that the health program initiatives have a major role to play in reducing under-five mortality rate in the high focus states in India.</p> </div