Automated segmentation of the atrial region and fossa ovalis towards computer-aided planning of inter-atrial wall interventions

Image-fusion strategies have been applied to improve inter-atrial septal (IAS) wall minimally-invasive interventions. Hereto, several landmarks are initially identified on richly-detailed datasets throughout the planning stage and then combined with intra-operative images, enhancing the relevant structures and easing the procedure. Nevertheless, such planning is still performed manually, which is time-consuming and not necessarily reproducible, hampering its regular application. In this article, we present a novel automatic strategy to segment the atrial region (left/right atrium and aortic tract) and the fossa ovalis (FO).Fundacão para a Ciência e a Tecnologia (FCT), in Portugal, and the European Social Found, European Union, for funding support through the “Programa Operacional Capital Humano” (POCH) in the scope of the PhD grants SFRH/BD/95438/2013 (P. Morais) and SFRH/BD/93443/2013 (S. Queirós). This work was funded by projects NORTE-01-0145-FEDER-000013, NORTE-01-0145-FEDER-000022 and NORTE-01-0145-FEDER-024300, supported by Northern Portugal Regional Operational Programme (Norte2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER), and also been funded by FEDER funds, through Competitiveness Factors Operational Programme (COMPETE), and by national funds, through the FCT, under the scope of the project POCI-01-0145-FEDER-007038info:eu-repo/semantics/publishedVersio

A competitive strategy for atrial and aortic tract segmentation based on deformable models

Multiple strategies have previously been described for atrial region (i.e. atrial bodies and aortic tract) segmentation. Although these techniques have proven their accuracy, inadequate results in the mid atrial walls are common, restricting their application for specific cardiac interventions. In this work, we introduce a novel competitive strategy to perform atrial region segmentation with correct delineation of the thin mid walls, and integrated it into the B-spline Explicit Active Surfaces framework. A double stage segmentation process is used, which starts with a fast contour growing followed by a refinement stage with local descriptors. Independent functions are used to define each region, being afterward combined to compete for the optimal boundary. The competition locally constrains the surface evolution, prevents overlaps and allows refinement to the walls. Three different scenarios were used to demonstrate the advantages of the proposed approach, through the evaluation of its segmentation accuracy, and its performance for heterogeneous mid walls. Both computed tomography and magnetic resonance imaging datasets were used, presenting results similar to the state-of-the-art methods for both atria and aorta. The competitive strategy showed its superior performance with statistically significant differences against the traditional free-evolution approach in cases with bad image quality or missed atrial/aortic walls. Moreover, only the competitive approach was able to accurately segment the atrial/aortic wall. Overall, the proposed strategy showed to be suitable for atrial region segmentation with a correct segmentation of the mid thin walls, demonstrating its added value with respect to the traditional techniques.The authors acknowledge Fundacao para a Ciencia e a Tecnologia (FCT), in Portugal, and the European Social Found, European Union, for funding support through the "Programa Operacional Capital Humano" (POCH) in the scope of the PhD grants SFRH/BD/95438/2013 (P. Morais) and SFRH/BD/93443/2013 (S. Queiros).Authors gratefully acknowledge the funding of projects NORTE-01-0145-FEDER-000013 and NORTE-01-0145-FEDER-000022, co-financed by "Programa Operacional Regional do Norte" (NORTE2020), through "Fundo Europeu de Desenvolvimento Regional" (FEDER).info:eu-repo/semantics/publishedVersio

Cryo-balloon reconstruction from two views

Atrial fibrillation is a major cause of stroke. Its treatment is performed under fluoroscopic image guidance. Augmented fluoroscopy has become a useful tool during the ablation pro-cedure for navigation under X-ray. Unfortunately, current navigation systems do not provide tools to localize and visu-alize a cryo-balloon catheters in 3-D. This is why we present a new approach to reconstruct the cryo-ballon catheter, mod-eled as a sphere, from two views. The reconstruction result can then be overlayed onto live fluoroscopic images during the procedure. In simulation studies, we compared our tech-nique to a reference method. While both methods worked equally well on noise-free data, we found our method more reliable if the input data was affected by noise. For example, in the presence of noise with a standard deviation of 4 mm, our maximum 3-D reconstruction error was less than 1 mm

Safe procedures despite ultra low radiation doses during catheter ablations of atrial and ventricular arrhythmias—A multicenter experience

Introduction: Despite the development of non-fluoroscopic catheter visualization options, fluoroscopy is still used in most ablation procedures. The aim of this multicenter study was to evaluate the safety and efficacy of a new ultra-low dose radiation protocol for EP procedures in a large number of patients. Methods and results: A total of 3462 consecutive patients (male 1926 (55.6%), age 64.4 ± 14.0 years, BMI 26.65 ± 4.70) undergoing radiofrequency ablation (left atrial (n = 2316 [66.9%], right atrial (n = 675 [19.5%], or ventricular (n = 471 [13.6%]) in three German centers were included in the analysis. Procedures were performed using a new ultra-low dose protocol operating at 8nGy for fluoroscopy and 36nGy for cine-loops. Additionally a very low framerate (2-3FPS) was used. Using the new protocol very low Air kerma-area product (KAP) values were achieved for left atrial ablations (104.25 ± 84.22 μGym2 ), right atrial ablations (70.98 ± 94.79 μGym2 ) and ablations for ventricular tachycardias or PVCs (78.62 ± 66.59 μGym2 ). Acute procedural success was achieved in 3289/3388 (97.1%) while the rate of major complications was very low compared to previously published studies not using low dose settings (n = 20, 0.6%). Conclusion: The ultra-low dose, low framerate protocol leads to very low radiation doses for all EP procedures while neither procedural time, fluoroscopy time nor success or complication rates were compromised. When compared to current real-world Air KAP data the new ultra-low dose fluoroscopy protocol reduces radiation exposure by more than 90%

Thermal impact of replacing constant voltage by low-frequency sine wave voltage in RF ablation computer modeling

[EN] Background and objectives: A constant voltage (DC voltage) is usually used in radiofrequency ablation (RFA) computer models to mimic the radiofrequency voltage. However, in some cases a low frequency sine wave voltage (AC voltage) may be used instead. Our objective was to assess the thermal impact of replacing DC voltage by low-frequency AC voltage in RFA computer modeling. Methods: A 2D model was used consisting of an ablation electrode placed perpendicular to the tissue fragment. The Finite Element method was used to solve a coupled electric-thermal problem. Quasi-static electrical approximation was implemented in two ways (both with equivalent electrical power): (1) by a constant voltage of 25 V in the ablation electrode (DC voltage), and (2) applying a sine waveform with peak amplitude of 25 root 2 V (AC voltage). The frequency of the sine signal (f(AC)) varied from 0.5 Hz to 50 Hz. Results: Sine wave thermal oscillations (at twice the f(AC) frequency) were observed in the case of AC voltage, in addition to the temperature obtained by DC voltage. The amplitude of the oscillations: (1) increased with temperature, remaining more or less constant after 30 s; (2) was of up to +/- 3 degrees C for very low f(AC) values (0.5 Hz); and (3) was reduced at higher f(AC) values and with distance from the electrode (almost negligible for distances > 5 mm). The evolution of maximum lesion depth and width were almost identical with both DC and AC. Conclusions: Although reducing f(AC) reduces the computation time, thermal oscillations appear at points near the electrode, which suggests that a minimum value of f(AC) should be used. Replacing DC voltage by low-frequency AC voltage does not appear to have an impact on the lesion depth. (C) 2020 Elsevier B.V. All rights reserved.This work was supported by the Spanish Ministerio de Ciencia, Innovacion y Universidades under "Programa Estatal de I+D+i Orientada a los Retos de la Sociedad", Grant no. "RTI2018-094357-B-C21".Pérez, JJ.; González Suárez, A.; Nadal, E.; Berjano, E. (2020). Thermal impact of replacing constant voltage by low-frequency sine wave voltage in RF ablation computer modeling. Computer Methods and Programs in Biomedicine. 195:1-7. https://doi.org/10.1016/j.cmpb.2020.105673S17195Doss, J. D. (1982). Calculation of electric fields in conductive media. Medical Physics, 9(4), 566-573. doi:10.1118/1.595107Tungjitkusolmun, S., Haemmerich, D., Hong Cao, Jang-Zern Tsai, Young Bin Choy, Vorperian, V. R., & Webster, J. G. (2002). Modeling bipolar phase-shifted multielectrode catheter ablation. IEEE Transactions on Biomedical Engineering, 49(1), 10-17. doi:10.1109/10.972835Yan, S., Wu, X., & Wang, W. (2016). A simulation study to compare the phase-shift angle radiofrequency ablation mode with bipolar and unipolar modes in creating linear lesions for atrial fibrillation ablation. International Journal of Hyperthermia, 32(3), 231-238. doi:10.3109/02656736.2016.1145746Pérez, J. J., González-Suárez, A., & Berjano, E. (2017). Numerical analysis of thermal impact of intramyocardial capillary blood flow during radiofrequency cardiac ablation. International Journal of Hyperthermia, 34(3), 243-249. doi:10.1080/02656736.2017.1336258Keangin, P., Wessapan, T., & Rattanadecho, P. (2011). Analysis of heat transfer in deformed liver cancer modeling treated using a microwave coaxial antenna. Applied Thermal Engineering, 31(16), 3243-3254. doi:10.1016/j.applthermaleng.2011.06.005Nakayama, A., & Kuwahara, F. (2008). A general bioheat transfer model based on the theory of porous media. International Journal of Heat and Mass Transfer, 51(11-12), 3190-3199. doi:10.1016/j.ijheatmasstransfer.2007.05.030Bhowmik, A., Singh, R., Repaka, R., & Mishra, S. C. (2013). Conventional and newly developed bioheat transport models in vascularized tissues: A review. Journal of Thermal Biology, 38(3), 107-125. doi:10.1016/j.jtherbio.2012.12.003Andreozzi, A., Brunese, L., Iasiello, M., Tucci, C., & Vanoli, G. P. (2018). Modeling Heat Transfer in Tumors: A Review of Thermal Therapies. Annals of Biomedical Engineering, 47(3), 676-693. doi:10.1007/s10439-018-02177-xIasiello M., Andreozzi A., Bianco N., Vafai K. The porous media theory applied to radiofrequency catheter ablation. Int. J. Numer. Methods Heat Fluid Flow, Vol. 30 No. 5, pp. 2669–2681. 10.1108/HFF-11-2018-0707.González‐Suárez, A., Herranz, D., Berjano, E., Rubio‐Guivernau, J. L., & Margallo‐Balbás, E. (2017). Relation between denaturation time measured by optical coherence reflectometry and thermal lesion depth during radiofrequency cardiac ablation: Feasibility numerical study. Lasers in Surgery and Medicine, 50(3), 222-229. doi:10.1002/lsm.22771Irastorza, R. M., Gonzalez-Suarez, A., Pérez, J. J., & Berjano, E. (2020). Differences in applied electrical power between full thorax models and limited-domain models for RF cardiac ablation. International Journal of Hyperthermia, 37(1), 677-687. doi:10.1080/02656736.2020.1777330Seiler, J., Roberts-Thomson, K. C., Raymond, J.-M., Vest, J., Delacretaz, E., & Stevenson, W. G. (2008). Steam pops during irrigated radiofrequency ablation: Feasibility of impedance monitoring for prevention. Heart Rhythm, 5(10), 1411-1416. doi:10.1016/j.hrthm.2008.07.011González-Suárez, A., Berjano, E., Guerra, J. M., & Gerardo-Giorda, L. (2016). Computational Modeling of Open-Irrigated Electrodes for Radiofrequency Cardiac Ablation Including Blood Motion-Saline Flow Interaction. PLOS ONE, 11(3), e0150356. doi:10.1371/journal.pone.0150356Bourier, F., Duchateau, J., Vlachos, K., Lam, A., Martin, C. A., Takigawa, M., … Jais, P. (2018). High‐power short‐duration versus standard radiofrequency ablation: Insights on lesion metrics. Journal of Cardiovascular Electrophysiology, 29(11), 1570-1575. doi:10.1111/jce.13724Labonte, S. (1994). Numerical model for radio-frequency ablation of the endocardium and its experimental validation. IEEE Transactions on Biomedical Engineering, 41(2), 108-115. doi:10.1109/10.284921Babuska, I., & Oden, J. T. (2004). Verification and validation in computational engineering and science: basic concepts. Computer Methods in Applied Mechanics and Engineering, 193(36-38), 4057-4066. doi:10.1016/j.cma.2004.03.00

Development of a patient-specific atrial phantom model for planning and training of inter-atrial interventions

Article is accepted for publicationBackgroundSeveral authors have presented cardiac phantoms to mimic the particularities of the heart, making it suitable for medical training and surgical planning. Although the initial models were mainly focused on the ventricles, personalized phantoms of the atria were recently presented. However, such models are typically rigid, the atrial wall is not realistic and they are not compatible with ultrasound (US), being sub-optimal for planning/training of several interventions. MethodsIn this work, we propose a strategy to construct a patient-specific atrial model. Specifically, the target anatomy is generated using a computed tomography (CT) dataset and then constructed using a mold-cast approach. An accurate representation of the inter-atrial wall (IAS) was ensured during the model generation, allowing its application for IAS interventions. Two phantoms were constructed using different flexible materials (silicone and polyvinyl alcohol cryogel, PVA-C), which were then compared to assess their appropriateness for US acquisition and for the generation of complex anatomies. ResultsTwo experiments were set up to validate the proposed methodology. First, the accuracy of the manufacturing approach was assessed through the comparison between a post-production CT and the virtual references. The results proved that the silicone-based model was more accurate than the PVA-C-based one, with an error of 1.680.79, 1.36 +/- 0.94, 1.45 +/- 0.77mm for the left (LA) and right atria (RA) and IAS, respectively. Second, an US acquisition of each model was performed and the obtained images quantitatively and qualitatively assessed. Both models showed a similar performance in terms of visual evaluation, with an easy detection of the LA, RA, and the IAS. Furthermore, a moderate accuracy was obtained between the atrial surfaces extracted from the US and the ideal reference, and again a superior performance of the silicone-based model against the PVA-C phantom was observed. ConclusionsThe proposed strategy proved to be accurate and feasible for the correct generation of complex personalized atrial models.The authors acknowledge "Fundacao para a Ciencia e a Tecnologia" (FCT), in Portugal, and the European Social Found, European Union, for funding support through the "Programa Operacional Capital Humano" (POCH) in the scope of the PhD grants SFRH/BD/95438/2013 (P. Morais) and SFRH/BD/93443/2013 (S. Queiros).Authors gratefully acknowledge the funding of Projects NORTE-01-0145-FEDER-000013 and NORTE-01-0145-FEDER-000022, cofinanced by "Programa Operacional Regional do Norte" (NORTE2020), through "Fundo Europeu de Desenvolvimento Regional" (FEDER).info:eu-repo/semantics/publishedVersio