3D Distance Fields: A Survey of Techniques and Applications

A distance field is a representation where, at each point within the field, we know the distance from that point to the closest point on any object within the domain. In addition to distance, other properties may be derived from the distance field, such as the direction to the surface, and when the distance field is signed, we may also determine if the point is internal or external to objects within the domain. The distance field has been found to be a useful construction within the areas of computer vision, physics, and computer graphics. This paper serves as an exposition of methods for the production of distance fields, and a review of alternative representations and applications of distance fields. In the course of this paper, we present various methods from all three of the above areas, and we answer pertinent questions such as How accurate are these methods compared to each other? How simple are they to implement?, and What is the complexity and runtime of such methods

The risk of post-operative pulmonary complications in lung resection candidates with normal forced expiratory volume in 1 s and diffusing capacity of the lung for carbon monoxide: a prospective multicentre study

Introduction According to the guidelines for preoperative assessment of lung resection candidates, patients with normal forced expiratory volume in 1 s (FEV1) and diffusing capacity of the lung for carbon monoxide (DLCO) are at low risk for post-operative pulmonary complications (PPC). However, PPC affect hospital length of stay and related healthcare costs. We aimed to assess risk of PPC for lung resection candidates with normal FEV1 and DLCO (>80% predicted) and identify factors associated with PPC. Methods 398 patients were prospectively studied at two centres between 2017 and 2021. PPC were recorded from the first 30 post-operative days. Subgroups of patients with and without PPC were compared and factors with significant difference were analysed by uni- and multivariate logistic regression. Results 188 subjects had normal FEV1 and DLCO. Of these, 17 patients (9%) developed PPC. Patients with PPC had significantly lower pressure of end-tidal carbon dioxide (PETCO2) at rest (27.7 versus 29.9; p=0.033) and higher ventilatory efficiency (V′E/V′CO2) slope (31.1 versus 28; p=0.016) compared to those without PPC. Multivariate models showed association between resting PETCO2 (OR 0.872; p=0.035) and V′E/V′CO2 slope (OR 1.116; p=0.03) and PPC. In both models, thoracotomy was strongly associated with PPC (OR 6.419; p=0.005 and OR 5.884; p=0.007, respectively). Peak oxygen consumption failed to predict PPC (p=0.917). Conclusions Resting PETCO2 adds incremental information for risk prediction of PPC in patients with normal FEV1 and DLCO. We propose resting PETCO2 be an additional parameter to FEV1 and DLCO for preoperative risk stratification