Dense Surface Models Research Articles

Highly Dense 3D Surface Generation Using Multi-image Matching

This study presents an automatic matching method for generating a dense, accurate, and discontinuity-preserved digital surface model (DSM) using multiple images acquired by an aerial digital frame camera. The proposed method consists of two main procedures: area-based multi-image matching (AMIM) and stereo-pair epipolar line matching (SELM). AMIM evaluates the sum of the normalized cross correlation of corresponding image points from multiple images to determine the optimal height of an object point. A novel method is introduced for determining the search height range and incremental height, which are necessary for the vertical line locus used in the AMIM. This procedure also includes the means to select the best reference and target images for each strip so that multi-image matching can resolve the common problem over occlusion areas. The SELM extracts densely positioned distinct points along epipolar lines from the multiple images and generates a discontinuity-preserved DSM using geometric and radiometric constraints. The matched points derived by the AMIM are used as anchor points between overlapped images to find conjugate distinct points using epipolar geometry. The performance of the proposed method was evaluated for several different test areas, including urban areas.

Fine-grained facial phenotype–genotype analysis in Wolf–Hirschhorn syndrome

Wolf-Hirschhorn syndrome is caused by anomalies of the short arm of chromosome 4. About 55% of cases are due to de novo terminal deletions, 40% from unbalanced translocations and 5% from other abnormalities. The facial phenotype is characterized by hypertelorism, protruding eyes, prominent glabella, broad nasal bridge and short philtrum. We used dense surface modelling and pattern recognition techniques to delineate the milder facial phenotype of individuals with a small terminal deletion (breakpoint within 4p16.3) compared to those with a large deletion (breakpoint more proximal than 4p16.3). Further, fine-grained facial analysis of several individuals with an atypical genotype and/or phenotype suggests that multiple genes contiguously contribute to the characteristic Wolf-Hirschhorn syndrome facial phenotype.

Variability in palatal shape and size in patients with bilateral complete cleft lip and palate assessed using dense surface model construction and 3D geometric morphometrics

Bilateral complete cleft lip and palate (BCLP) is the most severe of the common orofacial clefts and is associated with the greatest deformity during development. The aim of this study was to use geometric morphometrics to evaluate palatal shape and size variability in patients with BCLP in comparison to nonclefted Czech boys. The variability of palatal size and shape in BCLP patients was greater when compared with the nonclefted population. Though palate variability in BCLP was wide, nonclefted palatal shapes were generally different (a high, wide and vaulted palate) and fell almost outside the range of BCLP variability. The palatal size and shape of BCLP patients (range from 12.1 to 16.5 years) was not correlated with age.A comparison of the mean shapes of the clefted and nonclefted groups showed that the BCLP palate is flatter and narrower. The most notable size difference was found in the area between the maxilla and premaxilla. This phenomenon is associated with the persisting separation of the premaxilla from the rest of the palate. The shape of the palatal configuration of the premaxilla and adjacent area was concave in the nonclefted group and convex in BCLP patients.

Stability analysis of “Grotta delle Felci” Cliff (Capri Island, Italy): structural, engineering–geological, photogrammetric surveys and laser scanning

A study of rock slope stability was performed using geological surveys and Digital Terrestrial Photogrammetry (DTP) integrated by Laser Scanning (LS) and topographic measurements. The use of DTP is useful especially in inaccessible sites such as natural cliffs. By obtaining oriented stereo images, accurate digital surface models and orthophotos, useful data can be produced showing geometrical characteristics of joints, blocks and slopes such as planes, attitude, spacing, persistence and rock mass volumes. In order to accomplish the analysis, DTP was combined with LS in order to build the Digital Dense Surface Model (DDSM) of the slope. The conventional method of limit equilibrium was applied to study the slope stability using a deterministic approach and to suggest activities of geo-monitoring and engineering solutions for risk mitigation with respect to the environment.

Robust real-time 3D respiratory motion detection using time-of-flight cameras

PurposeRespiratory motion of the patient during data acquisition causes artifacts in the field of emission or computed tomography. Respiratory gating allows to track and correct these artifacts.Materials and methodsIn this paper, we present a system that uses the fairly new and off-the-shelf time-of-flight (ToF) technology to compute a dense estimate of the three-dimensional respiratory motion of a patient. The work is characterized by three key contributions. The first is the employment of ToF sensors. Using ToF sensors, it is feasible to acquire a dense 3D surface model of the chest and abdomen of the patient with more than 15 frames per second. The second contribution is an algorithm to derive a surface representation which enables the estimation of the 3D respiratory motion of the patient, which is sufficient to compute 1D breathing signals for scalable specific regions of interest like chest and abdomen. The proposed data-driven algorithm models the chest and abdomen three-dimensionally by fitting distinct planes to different regions of the torso of the patient. The third contribution is the possibility to derive a sub-millimeter accurate 1D respiratory motion signal by observing the displacement of each plane.ResultsOur ToF modeling approach enables marker less, real-time, 3D tracking of patient respiratory motion with an accuracy of 0.1 mm.ConclusionThus, our approach provides 1D breathing signals for scalable anatomical regions of interest with sufficient accuracy for artifact reduction in SPECT or X-ray angiography.

Williams syndrome

Williams syndrome

Discriminating Power of Localized Three-Dimensional Facial Morphology

Many genetic syndromes involve a facial gestalt that suggests a preliminary diagnosis to an experienced clinical geneticist even before a clinical examination and genotyping are undertaken. Previously, using visualization and pattern recognition, we showed that dense surface models (DSMs) of full face shape characterize facial dysmorphology in Noonan and in 22q11 deletion syndromes. In this much larger study of 696 individuals, we extend the use of DSMs of the full face to establish accurate discrimination between controls and individuals with Williams, Smith-Magenis, 22q11 deletion, or Noonan syndromes and between individuals with different syndromes in these groups. However, the full power of the DSM approach is demonstrated by the comparable discriminating abilities of localized facial features, such as periorbital, perinasal, and perioral patches, and the correlation of DSM-based predictions and molecular findings. This study demonstrates the potential of face shape models to assist clinical training through visualization, to support clinical diagnosis of affected individuals through pattern recognition, and to enable the objective comparison of individuals sharing other phenotypic or genotypic properties.

Visualization and model building in medical imaging.

We present technologies and ideas, developed from the JFIT 'Active Stereo Probe Project', which are applicable to problems within medical measurement and monitoring. Two related areas are considered. The first concerns patient body surface modelling. During the project two state-of-the-art non-contact surface measurement techniques have been developed which are applicable to medical situations requiring dense and accurate body surface modelling. Such applications include, for example, prosthetic appliance fabrication, presurgical planning and non-invasive deformity analysis. The second is concerned with overlay projection. Using this enabling technology the information content of a scene can be enhanced as an aid to medical personnel. Results and illustrative applications of the newly developed technology are presented.