Position sensitive detection of neutrons in high radiation background field.

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high γ and e(-) radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 µm(2)) spectroscopic Timepix detector adapted for neutron detection utilizing very thin (10)B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane) and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10(-4).

[Outcomes of catheter ablation of atrial fibrillation in patients over 65 years of age]. / Výsledky katetrové ablace fibrilace síní u pacientu nad 65 let.

PURPOSE: This study assessed ablation techniques, recurrent arrhythmias, long-term outcomes, and complications of catheter ablation for atrial fibrillation (AF) in patients 65 years of age. METHODS: Consecutive patients aged < 65 years (n = 653) vs 65 years (n = 213), who underwent catheter ablation of AF in the course of eight years, were compared. Ablation strategy and procedure endpoints were left at the operators discretion. RESULTS: The group of patients 65 years comprised more females (p < 0.001), and more frequently presented with persistent AF (p = 0.010). These patients less frequently underwent simple pulmonary vein isolation (p = 0.017); on the contrary, extensive ablation including coronary sinus intervention was more common (p = 0.020). There was no difference in repeat ablation procedures (25 % vs 26 % patients; p = 0.823, or 1.4 vs 1.5 ablation procedures/1 patients; p = 0.479, respectively). Spectrum of recurrent arrhythmias did not differ between the groups except for more frequent paroxysmal AF before the first repeat ablation in patients < 65 years (p = 0.050). At the end of 49 ± 26 month total follow-up, stable sinus rhythm (SR) was achieved in 85 % patients < 65 years vs 76 % patients 65 years (p = 0.318). To maintain stable SR, older patients more often continued to take antiarrhythmic medication (p = 0.054). More serious complication occurred in 3.8 % of the patients 65 years vs 2.1 % of the patients < 65 years of age (p = 0.207). CONCLUSION: Patients 65 years of age achieved insignificantly worse long-term outcome after insignificantly fewer repeat ablation procedures, and with more frequent use of antiarrhythmic drugs. SR maintenance and risk of complications were, however, favorable.

[Catheter ablation of atrio-ventricular accessory pathways in the era of ablation therapy of complex arrhythmias: a changing perspective for oncoming generation of electrophysiologists]. / Katetrová ablace atrioventrikulárních prídatných drah v ére ablacní lécby komplexních arytmií: menící se perspektiva pro nastupující generaci elektrofyziologu

INTRODUCTION: Catheter ablation of atrio-ventricular accessory pathways has become a routine treatment method. However, its perspective has been changing in the era of ablation of complex arrhythmias. This study was aimed at evaluating accessory pathways ablation efficacy within the last nine years at one center. METHODS: From February 2002 to June 2011, catheter ablation of accessory pathways was performed in 247 patients (100 females, 42 ± 16 years). Elimination of accessory pathways conduction in both directions was the procedure endpoint. RESULTS: Immediate accessory pathways conduction elimination at the first ablation was achieved in 228 (92%) patients. Ablation failed to eliminate accessory pathways conduction in 19 (8%) patients, or accessory pathways conduction subsequently recurred in another 7 (3%) patients. Repeat ablation was completed in 20 (8%) patients, 2 patients underwent a third ablation procedure. In total, accessory pathway was permanently eliminated in 238 (96%) patients. Ablation failure was connected with a risky position in the vicinity of atrio-ventricular conduction system in 6 (67 %) out of 9 patients. By the individual A, B, C, D operators experience, efficacy of the first procedure/total efficacy, was 97%/99%, 90%/96%, 87%/87%, and 91%/91%, respectively (comparison of inter-operator efficacy of the first and repeat ablation by Kruskal-Wallis ANOVA test: p = 0,19 and 0,05, respectively). CONCLUSION: Accessory pathways ablation efficacy exceeds 95%, and ablation failure is dominantly related to the accessory pathways location close to the atrio-ventricular conduction system. Individual operator's experience was associated with a certain disparity between high and nearly absolute accessory pathways ablation efficacy.