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RSTA showed a high and durable success rate in vein ablation in conjunction with sustained clinical efficacy.

BackgroundThis was a prospective study of radiofrequency segmental thermal ablation (RFA) for the treatment of incompetent varicose great saphenous veins (GSVs). The present report describes long-term follow-up at 5 years.MethodsThe 5-year follow-up of this multicentre European study included assessment of the Venous Clinical Severity Score (VCSS), and GSV occlusion and reflux on duplex imaging.ResultsA total of 225 patients had 295 GSVs treated by RFA, achieving an initial vein occlusion rate of 100 per cent. With 80·0 per cent compliance, Kaplan–Meier analyses showed a GSV occlusion rate of 91·9 per cent and a reflux-free rate of 94·9 per cent at 5 years. Among the 15 GSVs noted with reflux during follow-up, only three showed full recanalization of the GSV at 1 week, 6 months and 3 years. Of the 12 legs with partial recanalization, reflux originated at the saphenofemoral junction in ten, with a mean length of the patent segment of 5·8 (range 3·2–10) cm; only six patients were symptomatic. Mean(s.d.) VCSS scores improved from 3·9(2·1) at baseline to 0·6(1·2), 0·9(1·3) and 1·3(1·7) at 1, 3 and 5 years.ConclusionAt 5 years RFA proved to be an efficient endovenous treatment for incompetent GSVs in terms of sustained clinical and anatomical success for the vast majority of treated patients.

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This work concentrates on the diffusion barrier stability of very thin (10 or 20 nm) α- or β-Ta, TaN, Ta(O) and Ta(N,O) films in the Cu/barrier/Si system. Based on the classical theory of the thin film growth and know how of material transport in thin films, the various Ta-based films were classified according to their density of free short-circuit paths. Using scanning electron microscopy, transmission electron microscopy, glow discharge optical emission spectroscopy and secondary ion mass spectrometry, the 20 nm thin polycrystalline columnar-structured β-Ta films were found to be stable up to 500 °C for 1 h. After 1 h at 600 °C Cu3Si was formed due to short-circuit diffusion of Cu throughout the β-Ta films. The 20 nm thin giant-grained α-Ta films show equivalent performance to the β-Ta films. On the other hand, the 10 nm thin stuffed nanocrystalline face-centered-cubic (fcc) TaN films were able to protect the Si from Cu diffusion up to at least 600 °C/1 h. Ten nm thin amorphous-like Ta(N,O) and Ta(O) films also show barrier stability that is comparable to fcc TaN. While Ta(N,O) tends to recrystallize mainly into hexagonal-close-packed Ta2N above 500 °C, the Ta(O) remains amorphous even at 600 °C. Besides the amorphous-like microstructure, the high recrystallization temperature of Ta(O) is the reason why the introduction of 5 nm thin Ta(O) film into the Cu/5 nm Ta(O)/5 nm β-Ta/Si structure leads to a stability increase up to at least 600 °C for 1 h.

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