Usefulness of image guidance in the surgical treatment of petrous apex cholesterol granuloma

The petrous apex is a pyramid-shaped structure, located medial to the inner ear and the intrapetrous segment of the internal carotid artery. Lesions of the petrous apex can be surgically treated through different surgical routes. Because of the important neurovascular structures located inside the temporal bone, anatomical 3D knowledge is paramount. For this reason, image-guided surgery could represent a useful tool. We report the case of a young woman who came to our observation for a trigeminal neuralgia due to a petrous apex cholesterol granuloma. The lesion was treated through the placement of a drainage tube via an infracochlear approach, with the aid of neuronavigation and intraoperative MRI. Preoperative CT scan images and intraoperative MRI images were fused for surgical planning. The accuracy of the neuronavigation system has proved to be good, and the safety of the procedure was enhanced. Therefore, neuronavigation and intraoperative MRI, though not available in all neurootological centres, should be considered useful tools in these challenging procedures

EXPERIMENTAL EVALUATION OF INTRAORAL SCANNERS IN EDENTULOUS MANDIBLES

Aim: the main difficulties for intraoral scanners (IOS) are found in the edentulous mandibles. The reduced bucco-lingual surface, the limited height of the bone crest and the mobility of the soft tissues generate criticalities for the acquisition of the digital impression. The purpose of this study is to evaluate the comparison between digital and analog impressions in these particular conditions. Methods: two scans were obtained for the 11 subjects. The first intraoral scan was carried out with intraoral scan (Omnicam DentsplySirona) and the second was acquired by digitizing a plaster model, obtained from an impression taken with an analogue method, the best choice in these cases. All scans were converted to standard tessellation language (STL). The STL files obtained for each patient were superimposed by means of the GEOMAGIC Control X software, to evaluate the comparison. The average distance values obtained through the Geomagic 3D software constitute our primary outcome measure. 1 sample t-test was used to prove the hypothesis that the average distances of the points obtained between the two files are relevant (α = .05). Results: concerning the scans ability to reproduce the analog impression the intraoral scans carried out with a intraoral scan generated files with single measurements in terms of minimal distance between objects far from scans obtained with analogue methods (t =-7.29, P < .001). Conclusion: regarding the results obtained, it was possible to conclude that the STL files deriving from digital impressions are significantly different from those deriving from analog impressions, highlighting a difference between the two methods

Current geodetic deformation in the South Africa region

We present a preliminary velocity field of the African continent derived from continuous GPS observations from 2004 to 2008. The aim of our work is to investigate the strain-rate pattern along the East Africa rift, in particular along the boundary of the two African plates (the Nubian and the Somalian) and in the South Africa region. We have processed GPS data in a time window spanning four years, i.e. from 2004 to 2008, involving IGS, TrigNet (a network of permanent GPS stations distributed throughout South Africa) and other sporadic sites. The GPS data have been processed by means of the Bernese software version 5.0 dividing the entire African network into two clusters. The combination of daily loosely constrained solutions provides the time series of about a hundred of permanent GPS sites mainly located in the African continent. Site velocities together with periodic signals, eventual steps, have been estimated simultaneously using the complete covariance matrices. Finally the velocity field has been expressed in the ITRF2005 reference frame. This investigation gives a preliminary idea of the velocity field and strain-rate pattern we can expect in the South-East Africa region, the observed deformations being barely measurable, below a few mm/year

An algorithm for the search of homogeneous strain-rate fields

The aim of this paper is to describe the theoretical fundamentals and the main features of a software suitably implemented to estimate the strain-rate tensor from continuous GPS data. Current softwares developed for geophysical applications generally estimate or compute bi-dimensional strain, since this is the most requested use. On the contrary, this software allows for a three-dimensional estimate of the strain-rate tensor. It accounts for all the significant GPS velocities and estimates the strain-rate components by the least squares method starting from the hypothesis of one homogeneous strain-rate field. An initial field has to be defined by at least 4 sites which pass the chi-squared test on the strain-rate homogeneity. The developed algorithm automatically searches for sites belonging to this initial homogeneous field, starting from the site nearest to the barycentre of the first 4 sites and proceeding until a user-defined limit distance. Each time a site is added, the homogeneity of the whole field is suitably tested by a number of statistic tests. In this work the algorithm has been also applied to some areas of geophysical interest

Rotational Effects associated with ground motion during the Mw 6.3 2009 L’Aquila (Central Italy) Earthquake

The Mw 6.3 2009 L’Aquila (Central Italy) earthquake produced more than one hundred rotational effects on chimneys, pillars, capitals and gravestones. In this paper we focus on the 37 objects that can be more reliably considered as representative of pure rotational ground motion, and find a relation between the distribution of the observed rotations, the epicentral distance, the macroseismic intensities and the directivity effects that characterize the L’Aquila event. We also find sound relationships between the type of observed rotations and the geophysical, geotechnical and geomorphological characteristics of the site of observation. In downtown L’Aquila we find 1) a remarkable convergence between distribution of the rotations and of the damage; 2) 100% of the rotations occurred at sites characterized by high factors of amplification and poor geological setting; 3) the ground rotations are not strongly dependent on topographic effects. Finally, from quantitative analyses of GPS data we find that the effect of the seismic arrival on an individual vertical object retrieved rotated is an overall rotation with a substantially unpredictable directio

Water level and volume estimations of the Albano and Nemi lakes (central Italy)

In April 2006 an airborne laser scanning (LIDAR) survey of the Albano and Nemi craters was carried out to obtain a high resolution digital terrain model (DTM) of the area. We have integrated the LIDAR survey of the craters and the recent bathymetry of the Albano lake to achieve a complete DTM, useful for morphological studies. In addition, with a GPS RTK survey (July 2007) we estimated the Albano and Nemi mean lake levels respectively at 288.16 m and 319.02 m (asl). Based on the integrated DTM and the newly estimated water level values, we evaluated about 21.7·106 m3 the water volume loss of the Albano lake from 1993 to 2007, with an average rate of about 1.6·106 m3/yr

GPS Positioning and Velocity Field in the Apennines Subduction Zone

A stable geodetic reference frame permits to relate one position to another and to compute a reliable deformation field from geodetic observations. In order to satisfy scientific requirements, the reference frame should be accurate, reliable and internally consistent over time with unambiguously specified datum definition (origin, scale, orientation and their respective time evolution). Current reference frame stability between successive frame realizations suggests that the agreement is at the level of 1 cm and 0.3 mm/yr respectively for absolute and time derivative translation and scale factors. They represent the current stability over time of the reference frame and set the sensitivity for geodetic measurements. Here we will present the results of a GPS deformation field in the Italian region obtained from all the available permanent GPS stations operated in Italy. The complex nature of the ongoing tectonic deformation along the Alpine-Apennines orogenic systems is now evident and GPS data have proven its capability to measure millimetre scale deformations

Strain rate relaxation of normal and thrust faults in Italy

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Integrazione di rilievi batimetrici e laser scanner aereo nell'area dei Colli Albani

The Colli Albani are a Quaternary volcanic complex located about 15 km SE of Rome, comprised in an area of latitudes 41.6-41.9 N and longitudes 12.5-12.9 E. It has recently developed particular interest in the geophysical community for some peculiar characteristics imputable to a residual volcanic activity. In the framework of a project financed by the Department of the Civil Protection devoted to the study of the Colli Albani deformations, we have recently realized a bathymetric survey of the Albano lake and an airborne laser scanner survey of the Albano and Nemi craters. The present work is composed by two phases. In a first phase the accuracy of the DEM achieved by the laser scanner is verified through a comparison with a GPS kinematic survey. In particular, our aim is to test if the use of DEM in different formats, TIN or Grid, could lead to meaningful differences in terms of accuracy and precision. In a second phase of the work, we merged the LIDAR and bathymetric data with the purpose to achieve a complete digital terrain model of the area that could allow in the next future geo-morphological analyses of the whole volcanic structure