Precision of transfer of preoperative planning for oral implants based on cone-beam CT-scan images through a robotic drilling machine

In this study, an image-guided system for oral implant placement was assessed. A specially designed mechanical tool has been elaborated to transfer the preoperative implant axis planned on 3-dimensional imagery into a surgical template by a numerically controlled drilling machine. The main drawback of image-guiding systems is the use of preoperative computed tomography, which is expensive and delivers high radiation doses. Therefore, in this study the image-guiding system was coupled with a cone-beam tomograph that significantly decreased both cost and radiation doses. Three edentulous models were used. To determine the accuracy of the system, the ability of a 1.8-mm diameter drill to enter a 2.0-mm diameter, 10-mm-long titanium tube inserted on the model with no contact was verified. Because the drill entered the tubes with no contact and went beyond the end of the tube, the transfer error was less than 0.2 mm for translation and less than 1.1 degrees for rotation. The method presented here is low cost and high precision compared to other technological solutions such as tracking. Further assessment in the surgical field should lead to daily use of this system for flapless surgery, to prepare a prosthesis prior to surgery for immediate loading, to reduce risk of injuring critical anatomical structures and to eliminate manual placement error.     

Comparative Evaluation of Dimension and Surface Detail Accuracy of Models Produced by Three Different Rapid Prototype Techniques

Rapid prototyping (RP) is a technology that produces physical models by selectively solidifying ultra violet (UV) sensitive liquid resin using a laser beam. These models can be formed using various techniques. A study was undertaken to compare the dimensional accuracy and surface details of three prototype models with a 3D STL (standard template library) image. In this study the STL file was used to produce three different rapid prototype models namely; model 1—fused deposition model (FDM) using ABS (acrylonitrile butadiene styrene), model 2—Polyjet using a clear resin and model 3—a 3 dimensional printing using a composite material. Measurements were made at various anatomical points. For surface detail reproductions the models were subjected to scanning electron microscopy analysis. The dimensions of the model created by Polyjet were closest to the 3D STL virtual image followed by the 3DP model and FDM. SEM analysis showed uniform smooth surface on Polyjet model with adequate surface details.     

Construction of a stereotaxic DTI atlas with full diffusion tensor information for studying white matter maturation from childhood to adolescence using tractography‐based segmentations

Reconstruction of white matter (WM) fiber tracts based on diffusion tensor imaging (DTI) is increasingly being used in clinical and research settings to study normal and pathological WM tissue as well as the maturation of this WM tissue. Such fiber tracking (FT) methodology, however, is highly dependent on the manual delineation of anatomical landmarks and the algorithm settings, often rendering the reproducibility and reliability questionable. Predefining these regions of interest on a fractional anisotropy (FA) atlas in standard space has already been shown to improve the reliability of FT results. In this paper, we constructed a new DTI atlas, which contains the complete diffusion tensor information in ICBM152 coordinates. From this high‐dimensional DTI atlas, and using robust FT protocols, we reconstructed a large number of WM tracts. Subsequently, we created tract masks from these fiber tract bundles and evaluated the atlas framework by comparing the reproducibility of the results obtained from our standardized tract masks with regions‐of‐interest labels from the conventional FA‐based WM atlas. Finally, we assessed laterality and age‐related WM changes in 42 normal subjects aged 0 to 18 years using these tractography‐derived tract segmentations. In agreement with previous literature, we observed an FA increase with age, which was mainly due to the decrease of perpendicular diffusivity. In addition, major functional pathways in the language, motor, and limbic system, showed a significant asymmetry in terms of the observed diffusion metrics. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc.     

THE ELIÁN GONZÁLEZ DISCURSIVE TEMPLATE

In this essay we return to the Elián González custody battle of 1999/2000 in order to investigate the lessons the case poses for understanding the conflicted mediation of childhood, and to ask why Elián's particular childhood continues to resonate widely years after his return to Cuba. Detailing how the Elián case ruptured the myth of Cuban exile exceptionalism, thereby ensuring that US Cubans became prey to the nativist discourses that historically targeted other US Latina/o groups, we also attend to the media, popular‐cultural, and international cooptions of the Elián story. Those cooptions indicate that the enduring and evolving Elián icon has come to provide an adaptable, differentially applied, and contradictory template by which numerous children have been pressed into symbolic service as “other Eliáns.” With this focus, we track the evolution of the Elián discursive template and its applications in cognate custody conflicts centred on the border‐crossing child as potential citizen.     

Effects of image normalization on the statistical analysis of perfusion MRI in elderly brains

Purpose

To fully understand the effects of an image processing methodology on the comparisons of regional patterns of brain perfusion over time and between subject groups.

Materials and Methods

Two brain normalization methods were compared using images of elderly controls and subjects with MCI and AD: the normalization package of statistical parametric mapping (SPM2), and a fully deformable model (FDM). The performance of these two normalization methods was quantitatively evaluated based on two criteria: (a) the alignment accuracy of five brain structures to the colin27 reference volume, and (b) impact of spatial normalization methods on the sensitivity of perfusion magnetic resonance imaging (pMRI).

Results

The delineations of all five brain structures had significantly higher overlap with expert manual tracings using FDM compared to SPM (two‐tailed, P < 0.025). When applied to the biostatistical analysis of CBF maps, a larger number of statistically significant voxels was identified from FDM compared with SPM2 regardless of the effects of the threshold and smoothing kernel.

Conclusion

The greater degree of deformation freedom associated with FDM may yield more accurate region matching and higher statistical sensitivity in identifying regions of CBF differences between elderly groups with prevalent late‐life neurodegenerative conditions. J. Magn. Reson. Imaging 2008;28:1351–1360. © 2008 Wiley‐Liss, Inc.     

Finding parametric representations of the cortical sulci using an active contour model

The cortical sulci are brain structures resembling thin convoluted ribbons embedded in three dimensions. The importance of the sulci lies primarily in their relation to the cytoarchitectonic and functional organization of the underlying cortex and in their utilization as features in non-rigid registration methods. This paper presents a methodology for extracting parametric representations of the cerebral sulci from magnetic resonance images. The proposed methodology is based on deformable models utilizing characteristics of the cortical shape. Specifically, a parametric representation of a sulcus is determined by the motion of an active contour along the medial surface of the corresponding cortical fold. The active contour is initialized along the outer boundary of the brain and deforms toward the deep root of a sulcus under the influence of an external force field, restricting it to lie along the medial surface of the particular cortical fold. A parametric representation of the medial surface of the sulcus is obtained as the active contour traverses the sulcus. Based on the first fundamental form of this representation, the location and degree of an interruption of a sulcus can be readily quantified; based on its second fundamental form, shape properties of the sulcus can be determined. This methodology is tested on magnetic resonance images and it is applied to three medical imaging problems: quantitative morphological analysis of the central sulcus; mapping of functional activation along the primary motor cortex and non-rigid registration of brain images.     

3D printing in designing of anatomical posterior column plate

Background

Acetabulum has a complex anatomy due to which anatomical acetabular plates are still under developmental phase. Although intra-operative contouring of reconstruction plate is done as a standard practice, it is associated with increased operative time and morbidity of patient. We have designed an acetabular plate for posterior fixation from experience of previous studies performed in our institute on acetabular fracture fixation which should be appropriate for most of the patient of Indian origin. Apart from avoiding intra-operative contouring of acetabular plates it also helps in preventing intra articular screw penetration.

应用真皮模板改善创面愈合质量的研究

目的:动态观察真皮模板应用后对创面微血管形成的影响,为真皮模板应用改善创面愈合质量提供依据。方法:选取2001/2002Ш度小面积烧伤患者,采用真皮模板(异体无细胞真皮基质)加自体薄皮复合移植的方法,修复Ш度烧伤患者切痂后创面,并以单纯自体薄皮移植作为对照,分别于术后1,2,3,4,6周取材,实验组与对照组各15例次,采用苏木精-伊红染色观察、免疫组化技术检测标本中CD34的表达。结果:在术后1～6周,随着创面的修复,真皮模板组CD34表达逐渐降低,而薄皮组CD34持续高表达,且有逐渐升高趋势,其结果与HE染色所见一致。两组比较具有显著性差异。结论:真皮模板与自体薄皮复合移植后,可以抑制创面毛细血管超常增生,从而减少瘢痕形成,改善创面愈合质量。     

Construction and Validation of Brain MRI Templates from a Korean Normal Elderly Population

ObjectiveThis study aimed to construct a Korean normal elderly brain template (KNE96) using Korean elderly individuals for use in brain MRI studies and to validate it.MethodsWe used high-resolution 3.0T T1 structural MR images from 96 Korean normal elderly individuals (M/F=48/48), aged 60 years or older (M=69.5±6.2 years, F=70.1±7.0 years), for constructing the KNE96 template. The KNE96 template was validated by comparing the registration-induced deformations between the KNE96 and ICBM152 templates using different MR images from 48 Korean normal elderly individuals (M/F=24/24), aged 60 years or older (M=71.5±5.9 years, F=72.8±5.1 years). We used the magnitude of displacement vectors (mag-displacement) and log of Jacobian determinants (log-Jacobian) to quantify the deformation produced during registration process to templates.ResultsThe mag-displacement and log-Jacobian of the registration were much smaller using the KNE96 template than with the ICBM152 template in most brain regions. There was a prominent difference in the significant averaged differences (SADs) of the mag-displacement and log-Jacobian between the KNE96 and ICBM152 at the superior, medial, and middle frontal gyrus, the lingual, inferior, middle, and superior occipital gyrus, and the caudate and thalamus.ConclusionThis study suggests that templates constructed from Asian populations, such as the KNE96, may be more desirable than those from Caucasian populations, like the ICBM152, in computational neuroimaging studies that measure and compare anatomical features of the frontal and occipital lobe, thalamus and caudate.