Fully Automatic and Real-Time Catheter Segmentation in X-Ray Fluoroscopy

Augmenting X-ray imaging with 3D roadmap to improve guidance is a common strategy. Such approaches benefit from automated analysis of the X-ray images, such as the automatic detection and tracking of instruments. In this paper, we propose a real-time method to segment the catheter and guidewire in 2D X-ray fluoroscopic sequences. The method is based on deep convolutional neural networks. The network takes as input the current image and the three previous ones, and segments the catheter and guidewire in the current image. Subsequently, a centerline model of the catheter is constructed from the segmented image. A small set of annotated data combined with data augmentation is used to train the network. We trained the method on images from 182 X-ray sequences from 23 different interventions. On a testing set with images of 55 X-ray sequences from 5 other interventions, a median centerline distance error of 0.2 mm and a median tip distance error of 0.9 mm was obtained. The segmentation of the instruments in 2D X-ray sequences is performed in a real-time fully-automatic manner.Comment: Accepted to MICCAI 201

Transcriptional Regulation of N-Acetylglutamate Synthase

The urea cycle converts toxic ammonia to urea within the liver of mammals. At least 6 enzymes are required for ureagenesis, which correlates with dietary protein intake. The transcription of urea cycle genes is, at least in part, regulated by glucocorticoid and glucagon hormone signaling pathways. N-acetylglutamate synthase (NAGS) produces a unique cofactor, N-acetylglutamate (NAG), that is essential for the catalytic function of the first and rate-limiting enzyme of ureagenesis, carbamyl phosphate synthetase 1 (CPS1). However, despite the important role of NAGS in ammonia removal, little is known about the mechanisms of its regulation. We identified two regions of high conservation upstream of the translation start of the NAGS gene. Reporter assays confirmed that these regions represent promoter and enhancer and that the enhancer is tissue specific. Within the promoter, we identified multiple transcription start sites that differed between liver and small intestine. Several transcription factor binding motifs were conserved within the promoter and enhancer regions while a TATA-box motif was absent. DNA-protein pull-down assays and chromatin immunoprecipitation confirmed binding of Sp1 and CREB, but not C/EBP in the promoter and HNF-1 and NF-Y, but not SMAD3 or AP-2 in the enhancer. The functional importance of these motifs was demonstrated by decreased transcription of reporter constructs following mutagenesis of each motif. The presented data strongly suggest that Sp1, CREB, HNF-1, and NF-Y, that are known to be responsive to hormones and diet, regulate NAGS transcription. This provides molecular mechanism of regulation of ureagenesis in response to hormonal and dietary changes

Continuous monitoring of droplet production of a vibrating orifice generator by laser light extinction.

To monitore droplet production of the vibrating orifice aerosol generator (VOAG) continously an optical droplet control has been developed on the bases of laser light extinction. The monodispersity of the droplets, the presence of satellites as well as bi - or multi - modal structures of the size distribution can be identified on the display of a oscilloscope

Xenon produces minimal haemodynamic effects in rabbits with chronically compromised left ventricular function

BACKGROUND: Xenon has only minimal haemodynamic side-effects on normal myocardium and might be a preferable anaesthetic agent for patients with heart failure. We studied the haemodynamic changes caused by 70% xenon in rabbits with chronically compromised left ventricular (LV) function. METHODS: Anaesthetized rabbits were thoracotomized and a major coronary artery was ligated to induce ischaemic heart disease. Nine weeks later, rabbits were again anaesthetized (ketamine/propofol), and haemodynamics were measured during inhalation of 70% xenon using echocardiography [LV end-diastolic dimension (LVedD), fractional shortening (FS), velocity of circumferential fibre shortening (VcF), ejection fraction (EF)] in closed-chest animals. Subsequently, rabbits were thoracotomized and instrumented for measurement of LV pressure (tip manometer), LV dP/dtmax and cardiac output (ultrasonic flow probe). Haemodynamics were recorded again during inhalation of 70% xenon. RESULTS: All rabbits had compromised LV function 9 weeks after coronary artery ligation. Mean LVedD increased from 12.9 (SD 0.9) mm to 17.1 (0.4) mm; EF decreased from 73 (9) to 64 (8)%; FS decreased from 36 (7) to 29 (5)%; VcF decreased from 28.9 (6.8) to 17.6 (4.7) mm s(-1); all P <0.05. Inhalation of 70% xenon had no effect on haemodynamics in closed-chest rabbits, as measured by echocardiography. After invasive instrumentation, small decreases in LV pressure from 78 (20) to 72 (19) mm Hg, LV dP/dtmax from 3081 (592) to 2633 (503) mm Hg s(-1) and cardiac output from 239 (69) to 225 (71) ml min(-1) were observed during xenon inhalation (all P <0.05). CONCLUSION: These data show that xenon has only minimal negative inotropic effects in rabbits with LV dysfunction after coronary artery ligatio