Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey

This paper provides a tutorial and survey for a specific kind of illustrative visualization technique: feature lines. We examine different feature line methods. For this, we provide the differential geometry behind these concepts and adapt this mathematical field to the discrete differential geometry. All discrete differential geometry terms are explained for triangulated surface meshes. These utilities serve as basis for the feature line methods. We provide the reader with all knowledge to re-implement every feature line method. Furthermore, we summarize the methods and suggest a guideline for which kind of surface which feature line algorithm is best suited. Our work is motivated by, but not restricted to, medical and biological surface models.Comment: 33 page

Hypertonicity-induced non-selective cation conductance in Ehrlich-Ascites tumour cells

In many cell types studied, the regulatory volume increase following a hypertonicity-induced cell shrinkage is known to involve the conductive uptake of inorganic osmolytes as one of the key mechanisms. The present study aimed to characterize a possible shrinkage-activated membrane current in Ehrlich-Lettre-Ascites tumour cells (ELA). Membrane currents were monitored in single ELA by means of the conventional, fast whole-cell patch-clamp method. After exposure to a 16%-hypertonic medium, 62% of all cells tested (n=162) responded with the activation of an inward current (234 ± 32 pA), an accompanying decrease of cell input resistance, and a shift of the reversal potential from -40.0 mV to 0.3 ± 2.0 mV. This current was reversibly blocked by the ion channel inhibitors (in order of potency) benzamil > gadolinium > amiloride > EIPA. Ion substitution experiments revealed that the current could be carried with almost equal efficiency by Na+, K+ or Li+, whereas it declined completely with NMDG+ or choline+ as the substitute. The data presented show consistently that in ELA cells shrinkage activates a non-selective cation conductance with a pharmacology differing from other volume-activated conductances. (This abstract is as it is in the printed issue of the journal)

A cell shrinkage-induced non-selective cation conductance with a novel pharmacology in Ehrlich-Lettre-ascites tumour cells

AbstractIn whole-cell recordings on Ehrlich–Lettre-ascites tumour (ELA) cells, the shrinkage-induced activation of a cation conductance with a selectivity ratio PNa:PLi:PK:Pcholine:PNMDG of 1.00:0.97:0.88:0.03:0.01 was observed. In order of potency, this conductance was blocked by Gd3+=benzamil>amiloride>ethyl-isopropyl-amiloride (EIPA). In patch-clamp studies using the cell-attached configuration, a 14 pS channel became detectable that was reversibly activated upon hypertonic cell shrinkage. It is concluded that ELA cells express a shrinkage-induced cation channel that may reflect a molecular link between amiloride-sensitive and -insensitive channels. In addition, because of its pharmacological profile, it may possibly be related to epithelial Na+ channels (ENaCs)

Visual navigation support for liver applicator placement using interactive map displays

Navigated placement of an ablation applicator in liver surgery would benefit from an effective intraoperative visualization of delicate 3D anatomical structures. In this paper, we propose an approach that facilitates surgery with an interactive as well as an animated map display to support navigated applicator placement in the liver. By reducing the visual complexity of 3D anatomical structures, we provide only the most important information on and around a planned applicator path. By employing different illustrative visualization techniques, the applicator path and its surrounding critical structures, such as blood vessels, are clearly conveyed in an unobstructed way. To retain contextual information around the applicator path and its tip, we desaturate these structures with increasing distance. To alleviate time-consuming and tedious interaction during surgery, our visualization is controlled solely by the position and orientation of a tracked applicator. This enables a direct interaction with the map display without interruption of the intervention. Based on our requirement analysis, we conducted a pilot study with eleven participants and an interactive user study with six domain experts to assess the task completion time, error rate, visual parameters and the usefulness of the animation. The outcome of our pilot study shows that our map display facilitates significantly faster decision making (11.8 s vs. 40.9 s) and significantly fewer false assessments of structures at risk (7.4 % vs. 10.3 %) compared to a currently employed 3D visualization. Furthermore, the animation supports timely perception of the course and depth of upcoming blood vessels, and helps to detect possible areas at risk along the path in advance. Hence, the obtained results demonstrate that our proposed interactive map displays exhibit potential to improve the outcome of navigated liver interventions

PelVis: Atlas-based Surgical Planning for Oncological Pelvic Surgery

Stem cells & developmental biolog