Anatomical variations of the hepatic artery: a closer view of rare unclassified variants

Background: Defining the hepatic artery anatomy is of great importance for both surgeons and radiologists. Michel classification was designed to classify hepatic artery variations. Nevertheless, there are variations that do not fit into this classification. In this study, we aim to define the incidence of all variations in a healthy liver donor by reviewing their CT scan with special emphasis on variations that do not fit in any of the Michel classes. Materials and methods: A retrospective analysis of CT scan of donors and potential liver donors who were evaluated by triphasic CT scan. The CT scans were reviewed independently by a radiologist and two transplant surgeons. Cases that did not fit in any of the Michel classes were classified as class 0. Results: Out of 241 donors, 210 were classified within the Michel classification, of which 60.9 % were class I and 9.1% class II. Thirty-one donors (12.9%) classified as class 0. Of which, nine, three, two and three had replaced right hepatic artery from pancreaticoduodenal artery, gastroduodenal artery, aorta and celiac artery, respectively. Two and 6 donors had accessory right hepatic artery from pancreaticoduodenal artery and gastroduodenal artery respectively.  Segment 4 artery originated from left and right hepatic artery in 56.8% and 31.9%, respectively. Conclusions: A great caution should be taken when evaluating the hepatic artery anatomy, clinicians should anticipate and be familiar with the rare unclassified variations of the hepatic artery

Multiple concentric gating traffic control in large-scale urban networks

Summarization: A new gating strategy for concentric cities based on the notion of the macroscopic or network fundamental diagram and the feedback-based gating concept is introduced and successfully tested. Different regions of large-scale urban networks may experience congestion at different levels and times during the peak period. In this paper, the zone, including the initial core of congestion, is considered as the first region, which has to be protected from congestion via gating; eventually, as the congestion continues to expand, the border of an extended network part becomes the second perimeter for gating control. Remarkable extensions while distributing the ordered controller flow to the gated traffic signals in case of low demand or occurrence of spillback are also considered. A greater part of the San Francisco urban network is used as test-bed within a microscopic simulation environment. Significant improvements in terms of network-wide mean speed and average delay per kilometer are obtained compared to the single perimeter gating and non-gating simulation scenarios.Παρουσιάστηκε στο: Intelligent Transportation System

Traffic signal perimeter control with multiple boundaries for large urban networks

Summarization: A new gating strategy based on the notion of the macroscopic or network fundamental diagram (MFD or NFD) and the feedback-based gating concept is introduced and tested successfully. Different regions of large-scale urban networks may experience congestion at different times during the peak period. In this paper, the zone including the initial core of congestion is considered as the first region which has to be protected from congestion via gating; eventually, as the congestion continues to expand, the border of an extended network part becomes the second perimeter for gating control. Extensions while distributing the ordered controller flow to the gated traffic signals in case of low demand or occurrence of spillback are also introduced. A greater part of the San Francisco urban network is used as test-bed within a microscopic simulation environment. Significant improvements in terms of average travel time and average delay are obtained compared to the single perimeter gating and non-gating cases.Παρουσιάστηκε στο: Intelligent Transportation Systems - 16th International IEEE Conference o