Postmortem whole-body CT angiography: evaluation of two contrast media solutions

OBJECTIVE: The objective of our study was to establish a standardized procedure for postmortem whole-body CT-based angiography with lipophilic and hydrophilic contrast media solutions and to compare the results of these two methods. MATERIALS AND METHODS: Minimally invasive postmortem CT angiography was performed on 10 human cadavers via access to the femoral blood vessels. Separate perfusion of the arterial and venous systems was established with a modified heart-lung machine using a mixture of an oily contrast medium and paraffin (five cases) and a mixture of a water-soluble contrast medium with polyethylene glycol (PEG) 200 in the other five cases. Imaging was executed with an MDCT scanner. RESULTS: The minimally invasive femoral approach to the vascular system provided a good depiction of lesions of the complete vascular system down to the level of the small supplying vessels. Because of the enhancement of well-vascularized tissues, angiography with the PEG-mixed contrast medium allowed the detection of tissue lesions and the depiction of vascular abnormalities such as pulmonary embolisms or ruptures of the vessel wall. CONCLUSION: The angiographic method with a water-soluble contrast medium and PEG as a contrast-agent dissolver showed a clearly superior quality due to the lack of extravasation through the gastrointestinal vascular bed and the enhancement of soft tissues (cerebral cortex, myocardium, and parenchymal abdominal organs). The diagnostic possibilities of these findings in cases of antemortem ischemia of these tissues are not yet fully understood.

A mixed-integer linear programming approach to the optimization of event-bus schedules: a scheduling application in the tourism sector

This paper deals with “The Enchanted Journey,” which is a daily event tour booked by Bollywood-film fans. During the tour, the participants visit original sites of famous Bollywood films at various locations in Switzerland; moreover, the tour includes stops for lunch and shopping. Each day, up to five buses operate the tour. For operational reasons, however, two or more buses cannot stay at the same location simultaneously. Further operative constraints include time windows for all activities and precedence constraints between some activities. The planning problem is how to compute a feasible schedule for each bus. We implement a two-step hierarchical approach. In the first step, we minimize the total waiting time; in the second step, we minimize the total travel time of all buses. We present a basic formulation of this problem as a mixed-integer linear program. We enhance this basic formulation by symmetry-breaking constraints, which reduces the search space without loss of generality. We report on computational results obtained with the Gurobi Solver. Our numerical results show that all relevant problem instances can be solved using the basic formulation within reasonable CPU time, and that the symmetry-breaking constraints reduce that CPU time considerably.