Dark Vessel Research Articles

Towards Automatic Recognition of Wakes Generated by Dark Vessels in Sentinel-1 Images

The recognition of wakes generated by dark vessels is a tremendous and interesting challenge in the field of maritime surveillance by Synthetic Aperture Radar (SAR) images. The paper aims at assessing the detection performance in different scenarios by processing Sentinel-1 SAR images along with ground truth data. Results confirm that the Radon-based approach is an effective technique for wake-based detection of dark vessels, and they lead to a deeper understanding of the effects of different sea and wind conditions. In general, the best applicative scenario is a marine image characterized by homogeneous sea clutter; the presence of natural surface film or strong transition from low wind speed areas to more windy zones worsen the detection performance. Nonetheless, the proposed approach features dark vessel detection capabilities by identifying their wakes, without any a priori knowledge of their positions.

Role of SWI in Early Detection of Hemorrhagic Transformation in Acute Cerebral Ischemia

Background: The advent of new magnetic resonance imaging (MRI) techniques has improved acute stroke diagnosis. Susceptibility weighted imaging (SWI) has an important role in the management of cerebro-vascular strokes. Patients and Method: The study was conducted upon 50 patients clinically diagnosed with cerebro-vascular strokes and referred to department of radio-diagnosis, Faculty of Medicine, Minia University. Computed tomography (CT) was done at first then magnetic resonance imaging was performed on a 1.5T Philips MR system using conventional MRI sequences as fluid attenuated inversion recovery (FLAIR), T2-weighted, T1-weighted and advanced sequences as susceptibility-weighted imaging (SWI) with the parameters including slice thickness, voxel size, field of view (FOV) and matrix,. They were done after the approval of ethical committee of our institution. Informed written consents were taken from the patients or their relatives. Results : In our study, we found that 35 patients presented with acute non hemorrhagic infarction even on SWI and 15 patients presented with hemorrhagic infarction noted in SWI. Only ten of those patients with hemorrhagic infarction detected in CT. We found that detection rate of hemorrhage in SWI sequence was (100%). Detection rate of hemorrhage in CT was (33.3%). In SWI as regarding detection of different signs of acute ischemic strokes we found that of hemorrhage was (88%), detection rate of prominent cortical veins in vicinity of infarct was (62%) and detection rate of dark vessel sign was 6%. Comparative studies between them were done revealed that hemorrhage was the most important sign detected at SWI. Conclusion : From this study we concluded that new imaging SWI MRI modality is a valuable MRI sequence in imaging hemorrhagic transformation in ischemic stroke.

Signal Intensity within Cerebral Venous Sinuses on Synthetic MRI.

Purpose:Flowing blood sometimes appears bright on synthetic T1-weighted images, which could be misdiagnosed as a thrombus. This study aimed to investigate the frequency of hyperintensity within cerebral venous sinuses on synthetic MR images and to evaluate the influence of increasing flow rates on signal intensity using a flow phantom.Materials and Methods:Imaging data, including synthetic and conventional MRI scans, from 22 patients were retrospectively analyzed. Signal intensities at eight locations of cerebral venous sinuses on synthetic images were graded using the following three-point scale: 0, “dark vessel”; 1, “hyperintensity within the walls”; and 2, “hyperintensity within the lumen.” A phantom with gadolinium solution inside a U-shaped tube was acquired without flow and then with increasing flow rates (60, 100, 200, 300, 400 ml/min).Results:Considering all sinus locations, the venous signal intensity on synthetic T1-weighted images was graded as 2 in 79.8% of the patients. On synthetic T2-weighted images, all sinuses were graded as 0. On fluid-attenuated inversion recovery (FLAIR) images, sinuses were almost always graded as 0 (99.4%). In the phantom study, the signal initially became brighter on synthetic T1-weighted images as the flow rate increased. Above a certain flow rate, the signal started to decrease.Conclusion:High signal intensity within the cerebral venous sinuses is a frequent finding on synthetic T1-weighted images. This corresponds to the hyperintensity noted at certain flow rates in the phantom experiment.

Vertical profiling and modelling of Escherichia coli decay in a shallow maturation pond operating in a tropical climate

ABSTRACTMaturation ponds are excellent natural treatment systems for disinfecting domestic wastewater from pathogenic bacteria because of their great sunlight exposure through depth and high pH and dissolved oxygen values – all considered important factors. Escherichia coli (E. coli) removal is higher at closer to the surface of the pond and proceeds to decrease due to the limited amount of sunlight at deeper depths. To quantify the decay coefficients (Kb) of E. coli in a shallow maturation pond, quartz vessels were used to create isolated batch experiments and submerged at different depths inside the pond during different periods of the day (morning and afternoon). Kb values ranged from 0.48 to 0.28 h−1, considering different depths and both periods. A dark control vessel was also used to quantify dark decay rates (Kd) at the same depth and periods as the quartz vessels, and ranged from 0.14 to 0.04 h−1. Environmental variables did not appear to influence overall disinfection. Two models for estimating final E. coli concentrations were proposed, considering the kinetic coefficients obtained in the batch experiments and the dispersed flow regime for continuous flow ponds, which resulted in very good fittings with monitoring data and demonstrated the vertical profiling of E. coli concentration.

Cholangiocarcinoma in a Young Woman With Perinatally Acquired HIV

Cholangiocarcinoma in a Young Woman With Perinatally Acquired HIV