RESUMEN
PURPOSE: Arteriovenous fistula (AVF) is the preferred treatment for long-term hemodialysis patients to allow reliable vascular access. Arteriovenous graft (AVG) is monitored using Doppler sonography to check a vessel's condition and predict complications such as steal syndrome. In this study, we developed an analysis algorithm and method to quantify steal syndrome using Doppler sonography. METHODS: Doppler sonography was used to determine the pattern of anterograde and retrograde flow. The ratio of blood volumes was calculated with a vision analysis software. First, performance of the developed algorithm was validated by comparing it with commercial Doppler sonography data. Doppler sonography was performed for an artificial vessel to analyze the steal flow. RESULTS: A total of 58 patients with steal flow were enrolled in this study. Of these patients, 23 did not have a difference in fingertip temperature between both sides. The median difference in temperature of 35 patients was 0.8°C (range, 0.3-1.9°C). The ratio of retrograde flow volume/antegrade flow volume in patients with the presence of temperature difference was significantly higher compared to that in patients without the temperature difference (p < .001). The ROC curve for the difference in flow volume had an AUC of 0.770. The optimal cutoff of difference in the flow volume between the two groups was 0.24 (sensitivity of 91.4 % and specificity of 52.2%). The flow volume difference was significantly positively correlated to temperature difference (r = 0.487, p < .003). CONCLUSION: Our algorithm could measure steal flow volume of a bidirectional waveform by antegrade arterial flow and retrograde reversal flow.
RESUMEN
Techniques that manipulate DNA, a biomolecule with electrical properties, are in demand in various medical fields. This study fabricated a nanochannel with a conductive/semi-conductive interface using focused ion beams (FIBs) and introduced a nanochip technology to freely align, attach, and detach lambda DNAs in the interface via electrophoresis. Two-step fabrication process of nanochannels was quantitatively characterized according to the different conditions of the FIB dose (1~30 nC/µm2) and current (1~500 pA). For electrophoresis test, four different nanofluidic channels with depths of 200 nm and lengths of 0.5, 1.0, 1.5, and 2.0 µm were processed at the center of the rectangular channel (10 µm × 10 µm). Different voltages (1~30 V) were applied for 15 min to attach the DNAs. As the voltage increased, more lambda DNAs attached to the nanochannel interface. Furthermore, an inverse voltage (-30 V) was applied to the lambda DNAs attached to the interface for 15 min to confirm that DNAs could be successfully detached. The results showed that this method could produce a highly promising nanochip technology to align and manipulate DNAs in the desired direction according to a conductive/semi-conductive nano-sized interface, which is applicable in various biomedical fields.
