An image processing technique is presented for finding and localizing the centroids of cylindrical markers externally attached to the human head in computed tomography (CT) and magnetic resonance ...(MR) image volumes. The centroids can be used as control points for image registration. The technique, which is fast, automatic, and knowledge-based, has two major steps. First, it searches the entire image volume to find one voxel inside each marker-like object. The authors call this voxel a "candidate" voxel, and they call the object a candidate marker. Second, it classifies the voxels in a region surrounding the candidate voxel as marker or nonmarker voxels using knowledge-based rules and calculates an intensity-weighted centroid for each true marker. The authors call this final centroid the "fiducial" point of the marker. The technique was developed on 42 scans of six patients-one CT and six MR scans per patient. There are four markers attached to each patient for a total of 168 marker images. For the CT images the false marker rate was zero. For MR the false marker rate was 1.4% (Two out of 144 markers). To evaluate the accuracy of the fiducial points, CT-MR registration was performed after correcting the MR images for geometrical distortion. The fiducial registration accuracy averaged 0.4 mm and was better than 0.6 mm for each of the eighteen image pairs.
Posteromedial dislocation of the elbow with lateral condyle fracture is a rare injury, and only a few cases have been reported in the literature. We report 3 children who had posteromedial ...dislocation of the elbow with Milch type II lateral condylar fracture of the distal humerus. Major complications included malunion, nonunion of the fracture, heterotophic calcification and elbow subluxation. From our experience and a review of the literature, open anatomical reduction and internal fixation of the lateral condyle fracture is the mainstay of treatment for these children. Poor reduction of the lateral condyle fracture results in incongruity of the joint surface and leads to poor results.
A blinded evaluation of two groups of retrospective image registration techniques was performed using as a gold standard a prospective marker-based registration method, and we compared the ...performance of one group with the other. By grouping the techniques as volume-based or surface-based, we could make some interesting conclusions. In order to ensure blindness, all retrospective registrations were performed by participants who had no knowledge of the gold-standard results until after their results had been submitted. Image volumes of three modalities (X-ray CT, MRI and PET) were obtained from patients undergoing neurosurgery on whom bone-implanted fiducial markers were mounted. These volumes had all traces of the markers removed and were provided via the Internet to outside collaborators, who then performed retrospective registrations on the volumes, calculating transformations from CT to MRI and/or from PET to MRI. The accuracy of each registration was then evaluated. The accuracy is measured at multiple volumes of interest. The volume-based techniques in this study tended to give substantially more accurate and reliable results than the surface-based ones for the CT-to-MRI registration tasks, and slightly more accurate results for the PET-to-MRI tasks. Analysis of these results revealed that the rotational component of error was more pronounced for the surface-based group. It was also apparent that all of the registration techniques we examined have the potential to produce satisfactory results much of the time, but that visual inspection is necessary to guard against large errors.
Congenital pseudarthrosis of the tibia (CPT) in young children with large bone defect after surgical resection can be difficult to reconstruct. Structural allograft may be a useful alternative in ...such cases but data are limited. We report a girl 1 year and 10 months of age with CPT successfully treated with en bloc resection of the recurrent extensive pseudarthrosis, intramedullary rod placement, and long-segment intercalary allografting with supplemental autograft of the bony defect. At 6 years of follow-up, radiographs showed equal leg lengths, with good incorporation into the host bone. This method is technically simple and less time-consuming. It may be considered as an alternative method to the other more complicated procedures, such as microvascular fibula graft or the Ilizarov technique, in such a young child. J Formos Med Assoc 2007;106(3 Suppl):S44-S49
Background
Up to 80% of Alzheimer’s Disease (AD) patients suffer from concurrent vascular contributions to cognitive impairment and dementia (VCID) resulting in multi‐etiology dementia. VCID (the 2nd ...leading cause of dementia) is more common in men throughout most of the lifespan. while the majority (approximately 2/3) of Alzheimer’s Disease (AD) patients are women. Ageing is a main dementia risk factor which may act through the depletion of sex hormones. Both testosterone, in men, and estrogen, in women, have been shown to be neuroprotective. In this study we examine the effect of gonadal hormones on cognitive changes in a mouse model of multi etiology dementia using the AppNL‐F/NL‐F knock‐in Alzheimer’s disease mouse model that does not overexpress amyloid precursor protein.
Methods
5‐6 months old App
NL‐F/NL‐F mice were subjected to gonadectomy or sham surgery and left to recover for 3 weeks to clear any endogenous gonadal hormones. Multi‐etiology dementia was modeled using chronic cerebral hypoperfusion (unilateral carotid artery occlusion). Control animals (App
NL‐F/NL‐F without hypoperfusion; AD only model) received a sham surgery. Mice were then subjected to a battery of behavioral tests before being euthanized and then brains and serum were collected.
Results
Cognitive impairment differences between groups were investigated using several behavioral tests: anxiety‐like behavior and activity levels using an open field testing, episodic‐like memory using a novel object recognition test, spatial learning and memory via Barnes maze testing and activities of daily living using a nest building test. Our next step is to evaluate the underlying pathology in the brain that could mediate cognitive deficits (i.e. amyloid pathology, white matter damage and neuroinflammation).
Conclusions
We hope that this work will highlight the importance of modeling endocrine aging in animal models of dementia and will contribute to further understanding of sex differences and sex specific risk factors for dementia.
High quality thin films of topological insulators （TI） such as Bi2Se3 have been successfully synthesized by molecular beam epitaxy （MBE）. Although the surface of MBE films can be protected by capping ...with inert materials such as amorphous Se, restoring an atomically clean pristine surface after decapping has never been demonstrated, which prevents in-depth investigations of the intrinsic properties of TI thin films with ex situ tools. Using high resolution scanning tunneling microscopy/spectroscopy （STM/STS）, we demonstrate a simple and highly reproducible Se decapping method that allows recovery of the pristine surface of extremely high quality Bi2Se3 thin films grown and capped with Se in a separate MBE system then exposed to the atmosphere during transfer into the STM system. The crucial step of our decapping process is the removal of the surface contaminants on top of amorphous Se before thermal desorption of Se at a mild temperature （-210 ~C）. This effective Se decapping process opens up the possibility of ex situ characterizations of pristine surfaces of interesting selenide materials and beyond using cutting-edge techniques.
PDF
