Abstract-This paper presents a new on-line planner for dynamic environments that is based on the concept of Velocity Obstacles (VO). It addresses the issue of motion safety, i.e. avoiding states of inevitable collision, by selecting a proper time horizon for the velocity obstacle. The proper choice of the time horizon ensures that the boundary of the velocity obstacle coincides with the boundary of the set of inevitable collision states. This time horizon is determined by the minimum time it would take the robot to avoid collision, either by stopping or by passing the respective obstacle. The planner generates a near-time optimal trajectory to the goal by selecting at each time step the velocity that minimizes the time-to-go and is out of the velocity obstacle. The planner takes into account the shape, velocity, and path curvature of the obstacle's trajectory. It is demonstrated for on-line motion planning in very crowded static and dynamic environments.

Background: Inadequate bowel preparation is still the main obstacle to a complete colonoscopy in many patients and necessitates many repeated procedures. We aimed to identify risk factors associated with inadequate bowel preparation and to better characterize these patients. Methods: This was a retrospective study that reviewed electronic reports of colonoscopy procedures over a 10-year period. Patients were divided into 2 groups: adequate vs. non-adequate bowel preparation. A multivariate analysis was performed to identify variables associated with inadequate bowel preparation, including age, sex, setting (inpatient/outpatient), preparation regimen and procedures’ indications. We examined the effect of inadequate preparation on colonoscopy quality indicators. Results: Of the 28,725 patients included in the study, 6,702 (23.3%) had inadequate bowel preparation. In the multivariate analysis, advanced age (odds ratio [OR] 1.015, 95% confidence interval [CI] 1.013-1.017; P<0.01), male sex (OR 1.353, 95%CI 1.286-1.423; P<0.01) and a minority population (OR 1.635, 95%CI 1.531-1.746; P<0.01) were significantly associated with inadequate bowel preparation. The inpatient setting was among the most prominent factors associated with inadequate bowel preparation (OR 2.018, 95%CI 1.884-2.163; P<0.01). Adequate bowel preparation was associated with a higher polyp detection rate (26.8% vs. 23.6%; OR 1.22, 95%CI 1.109-1.347; P<0.01) and colorectal cancer (2.8% vs. 2.4%; OR 1.402, 95%CI 1.146-1.716; P<0.01), and higher frequencies of cecal (96.4% vs. 73.5%; OR 2.243, 95%CI 2.095-2.403; P<0.01) and terminal ileum intubation (8.1% vs. 5.4%; OR 1.243, 95%CI 1.088-1.434; P<0.01). Conclusion: We outlined various factors associated with inadequate bowel preparation and confirmed its adverse effect on colonoscopy quality indicators.

Background: Propofol-mediated sedation is safe and clearly associated with increased patient satisfaction. However, whether it results in a favorable effect on colonoscopy outcomes and performance compared to standard sedation with benzodiazepines/opiates remains unclear. Objectives: To determine the effect of propofol-mediated sedation on colonoscopy-quality measures compared to traditional sedation. Methods: A large cohort of 44,794 patients who had undergone sedated colonoscopies were included. Colonoscopy-quality indicators were examined in benzodiazepine/opiate-sedated patients and compared with a propofol-mediated sedation group. Adjustment for potential confounders, such as age, sex, quality of bowel preparation, procedural setting, and indication was performed. Results: Patients who received propofol-mediated sedation were more likely, and in a dosedependent manner, to have an enhanced polyp-detection rate (22.8% vs 20.9%, P<0.001), cecal intubation rate (90.4% vs 87.3%, P<0.001), and terminal ileum-intubation rate (6.4% vs 1.6%, P<0.001). On multivariate analysis, these findings were maintained, as propofol-mediated sedation use was significantly associated with improved colonoscopy indicators. Conclusion: Propofol-mediated sedation during colonoscopy is associated with better examination performance and improved outcomes. Further prospective or randomized trials to support these findings are warranted.

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We describe an inadequate antibody response to rabies vaccine in an immunocompromised patient. A literature search revealed 15 additional immunocompromised patients, of whom 7 did not exhibit the minimum acceptable level of antibodies after a complete postexposure prophylaxis regimen. An international rabies registry is needed to provide a basis for determining appropriate vaccination protocols.

Background:Melanosis coli, a brown discoloration of colonic mucosa, is considered as a benign condition mainly observed in patients under chronic anthranoid laxatives. Recent data link this condition with an increased adenoma detection rate. Moreover, its tumorigenic potential and possible association with the development of colorectal cancer remains uncertain. We conducted this study to compare the polyp detection rate and colorectal cancer diagnosis in patients with melanosis against matched control group without melanosis.Patients and methods:A retrospective single-center study. Patients diagnosed with melanosis coli on colonoscopy over a 15-year period were included. Each melanosis coli patient was matched with three controls by age, gender, setting (inpatient/outpatient), and procedure’s indication. Polyp detection rate and diagnosis of colorectal cancer were recorded and compared between the groups before and after adjustment for bowel preparation.Results:A cohort of 718 patients with melanosis and 2154 controls were included. The polyp detection rates were 33.4% and 21.8% of melanosis and control groups, respectively (P < .001). Melanosis coli, however, was associated with less diagnosis of colorectal cancer than controls (0.3% vs 3.9%; P < .001). In multivariate analysis, melanosis diagnosis on endoscopy was significantly associated with higher polyp detection rate (odds ratio [OR] = 1.986, 95% confidence interval [CI]: 1.626-2.425; P value < .01).Conclusions:Melanosis coli is not associated with increased diagnosis of colorectal cancer. It is associated, however, with enhanced polyp detection likely due to chromo-endoscopy-like effect.

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This paper addresses the issue of motion planning in dynamic environments using Velocity Obstacles. Specifically, we propose an adaptive time horizon to truncate the velocity obstacle so that its boundary closely, yet conservatively, approximates the boundary of the set of states from which collision is unavoidable. We wish to develop a representation such that any velocity vector that does not penetrate the velocity obstacle is safe, i.e. an avoidance maneuver exists, and any that does is not. Such clear partitioning between safe and unsafe velocities would allow safe planning with only one step look ahead, and can produce faster trajectories than the conservative trajectories produced when using an infinite time horizon. The computation of the adaptive time horizon is formulated as a minimum time problem, which is solved numerically for each static or moving obstacle. It is used in an on-line planner that generates locally time optimal trajectories to the goal. The planner is demonstrated for static and moving obstacles, and for on-line motion planning in a crowded dynamic environment.