3,572 research outputs found
Reflectance Transformation Imaging (RTI) System for Ancient Documentary Artefacts
This tutorial summarises our uses of reflectance transformation imaging in archaeological contexts. It introduces the UK AHRC funded project reflectance Transformation Imaging for Anciant Documentary Artefacts and demonstrates imaging methodologies
Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery
One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions
Solar Stereoscopy with STEREO/EUVI A and B spacecraft from small (6 deg) to large (170 deg) spacecraft separation angles
We performed for the first time stereoscopic triangulation of coronal loops
in active regions over the entire range of spacecraft separation angles
(, and
). The accuracy of stereoscopic correlation depends mostly on the
viewing angle with respect to the solar surface for each spacecraft, which
affects the stereoscopic correspondence identification of loops in image pairs.
From a simple theoretical model we predict an optimum range of , which is also experimentally confirmed. The best
accuracy is generally obtained when an active region passes the central
meridian (viewed from Earth), which yields a symmetric view for both STEREO
spacecraft and causes minimum horizontal foreshortening. For the extended
angular range of we find a mean 3D
misalignment angle of of stereoscopically
triangulated loops with magnetic potential field models, and for a force-free field model, which is partly caused by
stereoscopic uncertainties . We predict optimum
conditions for solar stereoscopy during the time intervals of 2012--2014,
2016--2017, and 2021--2023.Comment: Solar Physics, (in press), 22 pages, 9 figure
Solar stereoscopy - where are we and what developments do we require to progress?
Observations from the two STEREO-spacecraft give us for the first time the
possibility to use stereoscopic methods to reconstruct the 3D solar corona.
Classical stereoscopy works best for solid objects with clear edges.
Consequently an application of classical stereoscopic methods to the faint
structures visible in the optically thin coronal plasma is by no means straight
forward and several problems have to be treated adequately: 1.)First there is
the problem of identifying one dimensional structures -e.g. active region
coronal loops or polar plumes- from the two individual EUV-images observed with
STEREO/EUVI. 2.) As a next step one has the association problem to find
corresponding structures in both images. 3.) Within the reconstruction problem
stereoscopic methods are used to compute the 3D-geometry of the identified
structures. Without any prior assumptions, e.g., regarding the footpoints of
coronal loops, the reconstruction problem has not one unique solution. 4.) One
has to estimate the reconstruction error or accuracy of the reconstructed
3D-structure, which depends on the accuracy of the identified structures in 2D,
the separation angle between the spacecraft, but also on the location, e.g.,
for east-west directed coronal loops the reconstruction error is highest close
to the loop top. 5.) Eventually we are not only interested in the 3D-geometry
of loops or plumes, but also in physical parameters like density, temperature,
plasma flow, magnetic field strength etc. Helpful for treating some of these
problems are coronal magnetic field models extrapolated from photospheric
measurements, because observed EUV-loops outline the magnetic field. This
feature has been used for a new method dubbed 'magnetic stereoscopy'. As
examples we show recent application to active region loops.Comment: 12 Pages, 9 Figures, a Review articl
Visualization and Correction of Automated Segmentation, Tracking and Lineaging from 5-D Stem Cell Image Sequences
Results: We present an application that enables the quantitative analysis of
multichannel 5-D (x, y, z, t, channel) and large montage confocal fluorescence
microscopy images. The image sequences show stem cells together with blood
vessels, enabling quantification of the dynamic behaviors of stem cells in
relation to their vascular niche, with applications in developmental and cancer
biology. Our application automatically segments, tracks, and lineages the image
sequence data and then allows the user to view and edit the results of
automated algorithms in a stereoscopic 3-D window while simultaneously viewing
the stem cell lineage tree in a 2-D window. Using the GPU to store and render
the image sequence data enables a hybrid computational approach. An
inference-based approach utilizing user-provided edits to automatically correct
related mistakes executes interactively on the system CPU while the GPU handles
3-D visualization tasks. Conclusions: By exploiting commodity computer gaming
hardware, we have developed an application that can be run in the laboratory to
facilitate rapid iteration through biological experiments. There is a pressing
need for visualization and analysis tools for 5-D live cell image data. We
combine accurate unsupervised processes with an intuitive visualization of the
results. Our validation interface allows for each data set to be corrected to
100% accuracy, ensuring that downstream data analysis is accurate and
verifiable. Our tool is the first to combine all of these aspects, leveraging
the synergies obtained by utilizing validation information from stereo
visualization to improve the low level image processing tasks.Comment: BioVis 2014 conferenc
- …