Real-time in situ three-dimensional integral videography and surgical navigation using augmented reality: a pilot study

To evaluate the feasibility and accuracy of a three-dimensional augmented reality system incorporating integral videography for imaging oral and maxillofacial regions, based on preoperative computed tomography data. Three-dimensional surface models of the jawbones, based on the computed tomography data, were used to create the integral videography images of a subject＇s maxillofacial area. The three-dimensional augmented reality system （integral videography display, computed tomography, a position tracker and a computer） was used to generate a three-dimensional overlay that was projected on the surgical site via a half-silvered mirror. Thereafter, a feasibility study was performed on a volunteer. The accuracy of this system was verified on a solid model while simulating bone resection. Positional registration was attained by identifying and tracking the patient/surgical instrument＇s position. Thus, integral videography images of jawbones, teeth and the surgical tool were superimposed in the correct position. Stereoscopic images viewed from various angles were accurately displayed. Change in the viewing angle did not negatively affect the surgeon＇s ability to simultaneously observe the three-dimensional images and the patient, without special glasses. The difference in three-dimensional position of each measuring point on the solid model and augmented reality navigation was almost negligible （〈1 mm）; this indicates that the system was highly accurate. This augmented reality system was highly accurate and effective for surgical navigation and for overlaying a three-dimensional computed tomography image on a patient＇s surgical area, enabling the surgeon to understand the positional relationship between the preoperative image and the actual surgical site, with the naked eye.

Human blastomere rotation in early cleavage embryos is not associated with reduced implantation: Evidence from time-lapse videography

Dear Editor,Time-lapse videography of human embryos allows for the easy visualization of the embryos without removing them from the protective environment of the incubator[1],the measurement of various morphokinetic(quantitative)parameters[2],and the identification of abnormalities of growth(qualitative parameters)such as direct cleavage[3],reverse cleavage[4]and intercellular contact of blastomeres[5].

FRAME: femtosecond videography for atomic and molecular dynamics

Many important scientific questions in physics,chemistry and biology require effective methodologies to spectroscopically probe ultrafast intra-and inter-atomic/molecular dynamics.However,current methods that extend into the femtosecond regime are capable of only point measurements or single-snapshot visualizations and thus lack the capability to perform ultrafast spectroscopic videography of dynamic single events.Here we present a laser-probe-based method that enables two-dimensional videography at ultrafast timescales(femtosecond and shorter)of single,non-repetitive events.The method is based on superimposing a structural code onto the illumination to encrypt a single event,which is then deciphered in a post-processing step.This coding strategy enables laser probing with arbitrary wavelengths/bandwidths to collect signals with indiscriminate spectral information,thus allowing for ultrafast videography with full spectroscopic capability.To demonstrate the high temporal resolution of our method,we present videography of light propagation with record high 200 femtosecond temporal resolution.The method is widely applicable for studying a multitude of dynamical processes in physics,chemistry and biology over a wide range of time scales.Because the minimum frame separation(temporal resolution)is dictated by only the laser pulse duration,attosecondlaser technology may further increase video rates by several orders of magnitude.

Motion visualization and estimation for flapping wing systems

Studies of fluid-structure interactions associated with flexible structures such as flapping wings require the capture and quantification of large motions of bodies that may be opaque. As a case study, motion capture of a free flying Manduca sexta, also known as hawkmoth, is considered by using three synchronized high-speed cameras. A solid finite element (FE) representation is used as a reference body and successive snapshots in time of the displacement fields are reconstructed via an optimization procedure. One of the original aspects of this work is the formulation of an objective function and the use of shadow matching and strain-energy regularization. With this objective function, the authors penalize the projection differences between silhouettes of the captured images and the FE representation of the deformed body. The process and procedures undertaken to go from high-speed videography to motion estimation are discussed, and snapshots of representative results are presented. Finally, the captured free-flight motion is also characterized and quantified.

Influence of Laser-Induced Bubble Formation on Laser Chemical Machining

Laser Chemical Machining (LCM) is a non-conventional processing method, which enables very accurate and precise ablation of metallic surfaces. Material ablation results from laser-induced thermal activation of heterogeneous chemical reactions between electrolytes and a metallic surface. However, when processing metallic surfaces with LCM, large fluctuations in ablation quality can occur due to rising bubbles. The for-mation of bubbles during laser chemical machining and their influence on the ablation quality has not been investigated. For a more detailed investigation of the bubbles, ablation experiments on Titanium and Ce-ramic under different thermal process conditions were performed. The experiments were recorded by a high-speed camera. The evaluation of the video sequences was performed using Matlab. The resulting bubbles were analyzed regarding their size and frequency. The results show that boil-ing bubbles formed on both materials during processing. Titanium also produces smaller bubbles, which can be identified as process bubbles ac-cording to their size. Furthermore, it was found that undisturbed laser chemical ablation can be achieved in the presence of a boiling process, since both boiling bubbles and process bubbles were detected during machining within the process window.