Magnetic resonance diagnosis of spinal arachnoid cyst

Magnetic resonance (MR) findings in one case each of extradural and intradural arachnoid cyst are described. Thoracic segments were involved in both cases. The cysts were slightly more intense than cerebrospinal fluid in both cases on T1 weighted images. The nature and extent of the lesions wer better demonstrated on MR images as compared with combined myelography and computed tomography.     

Contrast-enhanced carotid MR angiography. Imaging principles and physics.

Arterial contrast enhancement on MR angiography images is dependent on the adequate timing of the contrast bolus arrival to the acquisition of the center of k-space. Different strategies for achieving this goal are described. The more advanced techniques are aimed at making the detection of the peak arrival and the start of data acquisition more robust in order to generate images with maximal arterial-background contrast with minimal venous signal contamination.     

Real-time imaging of axonally transported subresolution organelles in vertebrate myelinated axons

A procedure is described for the real-time imaging of organelles of sub-resolution dimensions that undergo rapid axonal transport in myelinated axons. The procedure uses commercially available processors to enhance images that are obtained with a video microscope. Image detail is enhanced by spatial high-pass filtering. Small moving organelles are detected by subtracting a dynamically updated image of stationary cellular detail from one that contains the same stationary features plus images of the moving organelles.     

Cystic Cervical Intramedullary Ependymoma with Previous lntracyst Hemorrhage: Magnetic Resonance Imaging at 1.5 T

A patient with a cystic cervical ependymoma is described. Magnetic resonance imaging identified evidence of previous intratumor hemorrhage, which was confirmed at surgery. The images, operative findings, and pathology are reviewed.     

Diffusion MR imaging for cerebral abscess

We report a case of cerebral abscess, which ruptured into the lateral ventricle. The radiological features on conventional MRI, appearance on both diffusion weighted images (DWI) and apparent diffusion coefficient (ADC) maps are described.     

Multiresolution analysis of emission tomography images in the wavelet domain.

This article develops a theoretical framework for the use of the wavelet transform in the estimation of emission tomography images. The solution of the problem of estimation addresses the equivalent problems of optimal filtering, maximum compression, and statistical testing. In particular, new theory and algorithms are presented that allow current wavelet methodology to deal with the two main characteristics of nuclear medicine images: low signal-to-noise ratios and correlated noise. The technique is applied to synthetic images, phantom studies, and clinical images. Results show the ability of wavelets to model images and to estimate the signal generated by cameras of different resolutions in a wide variety of noise conditions. Moreover, the same methodology can be used for the multiscale analysis of statistical maps. The relationship of the wavelet approach to current hypothesis-testing methods is shown with an example and discussed. The wavelet transform is shown to be a valuable tool for the numerical treatment of images in nuclear medicine. It is envisaged that the methods described here may be a starting point for further developments in image reconstruction and image processing.     

Atypical panic attacks and lack of resolution of mourning

A number of psychologic and biologic contributors to panic disorder have been identified. Three cases of young adult women who experienced atypical panic attacks are described. The attacks are atypical because they had ideational or situational precipitants and because they were inevitably accompanied by intrusive visual images of a deceased loved one. In each case, there was also the persistence of irrational beliefs and/or unintegrated feelings about the deceased, corroborating that the intrusive images and panic attacks occurred in the context of unresolved mourning. Although the association between panic attacks and intrusive images apparently has not been reported previously, both phenomena have been associated with lack of resolution of mourning. The discussion considers similarities in these cases and in reports of Vietnam veterans suffering from posttraumatic stress disorder and panic attacks. Together, these similarities suggest that unresolved traumas of various kinds may at times contribute to the development of atypical panic attacks accompanied by intrusive visual images.     

Harmonic imaging. A new method of ultrasound imaging of brain perfusion

In this review, methodological aspects of cerebral perfusion imaging with ultrasound contrast agents are described. The various experimental concepts contributing to an understanding of the phenomena are summarised and the resulting investigation techniques on patients are illustrated. By means of harmonic imaging, human cerebral perfusion can be depicted as a two-dimensional scan. The two major principles of contrast measurement are analysis of the bolus kinetics and analysis of the refill kinetics. Using the bolus method, hypoperfused areas in stroke patients can be visualised and parameter images of wash-in and wash-out curves can be generated off-line. The recently developed theory on the refill kinetics of UCA enables us to calculate parameters for describing the cerebral microcirculation, as they are less affected by the depth dependence of the contrast effect. These parameters can also be visualised as images. The ultrasound methods described in this article represent new minimally invasive bedside techniques for analysing brain perfusion. Although their development is still in an early stage, the potential of these ultrasound technologies to compete with perfusion CT, perfusion MRI, and SPECT in the diagnostic arsenal of brain imaging techniques is becoming evident.     

A simple and reliable method for construction of parallel multibarrel microelectrodes

A modification to the method of construction of parallel or “piggy-back” electrodes for extracellular single-unit recording combined with iontophoresis is described that facilitates the alignment of the two components of the array. The method involves the use of an orthogonal viewing device (a pair of mirrors mounted symmetrically at 45° to the horizontal), which produces a pair of virtual images of the electrode components that can be viewed with a microscope. A slight displacement between the electrodes is easily detected as an uneven separation between the electrode images. The positions of the electrode components are adjusted until there is no visible separation of the electrodes or their virtual images.     

Enlarged Virchow–Robin Spaces along the Medullary Perforators in a Child with Seizures

Enlarged Virchow–Robin spaces along the medullary perforators on brain magnetic resonance images (MRIs) of a 4–year–old, neurologically intact child with seizures are described. The differential diagnosis of cystic spaces in the centrum semiovale is discussed. The sparse MRI literature on bright signal intensities in childhood is reviewed.     

Critical evaluation of the searching technic of the polarization-sensitive neurons of insects]

The demerit of the light stimulator used by the authors was the presence of lenses between the eye and the observed light source. Apart from the image of the aperture diaphragm, the images of some details and reflections were formed. The terminal lens of the stimulator and the eye optics can divide the main and secondary images of the retina. Therefore the reactions of insect neurons to polarized light described previously could be explored also as the responses to flickers in secondary images.     

Nonlinear spatial normalization using basis functions.

We describe a comprehensive framework for performing rapid and automatic nonlabel-based nonlinear spatial normalizations. The approach adopted minimizes the residual squared difference between an image and a template of the same modality. In order to reduce the number of parameters to be fitted, the nonlinear warps are described by a linear combination of low spatial frequency basis functions. The objective is to determine the optimum coefficients for each of the bases by minimizing the sum of squared differences between the image and template, while simultaneously maximizing the smoothness of the transformation using a maximum a posteriori (MAP) approach. Most MAP approaches assume that the variance associated with each voxel is already known and that there is no covariance between neighboring voxels. The approach described here attempts to estimate this variance from the data, and also corrects for the correlations between neighboring voxels. This makes the same approach suitable for the spatial normalization of both high-quality magnetic resonance images, and low-resolution noisy positron emission tomography images. A fast algorithm has been developed that utilizes Taylor's theorem and the separable nature of the basis functions, meaning that most of the nonlinear spatial variability between images can be automatically corrected within a few minutes.     

Enhanced detection of focal brain responses using intersubject averaging and change-distribution analysis of subtracted PET images

Intersubject averaging and change-distribution analysis of subtracted positron emission tomographic (PET) images were developed and tested. The purpose of these techniques is to increase the sensitivity and objectivity of functional mapping of the human brain with PET. To permit image averaging, all primary tomographic images were converted to anatomically standardized three-dimensional images using stereotactic anatomical localization and interslice interpolation. Image noise, measured in control-minus-control subtractions, was strongly suppressed by averaging. Signal-to-noise ratio, measured in stimulus-minus-control subtractions (hand vibration minus eyes-closed rest), rose steadily with averaging, confirming the accuracy of our method of anatomical standardization. Distribution analysis of CBF change images (outlier detection by gamma-2 statistic) was assessed as an omnibus test for state-dependent changes in regional neuronal activity. Sensitivity in detecting the somatosensory response rose steadily with averaging, increasing from 50% in individual images to 100% when three or more images were averaged. Specificity was 100% at all averaging levels. Although described here as a technique for functional brain mapping with H2(15O) CBF images, image averaging, and change-distribution analysis are more generally applicable techniques, not limited to a single purpose or tracer.     

A single-camera method for three-dimensional video imaging

We describe a novel method for recovering the three-dimensional (3D) point geometry of an object from images acquired with a single-camera. Typically, multiple cameras are used to record 3D geometry. Occasionally, however, there is a need to record 3D geometry when the use of multiple cameras is either too costly or impractical. The algorithm described here uses single-camera images and requires in addition that each marker on the object be linked to at least one other marker by a known distance. The linkage distances are used to recover information about the third dimension that would otherwise be lost in single-camera two-dimensional images. The utilities of the method are its low-cost, simplicity, and ease of calibration and implementation. We were able to estimate 3D distances and positions as accurately as with a commercially available multi-camera 3D system. This method may be useful in pilot studies to determine whether 3D imaging systems are required, or, it can serve as a low-cost alternative to multi-camera systems.     

Method for bias field correction of brain T1-weighted magnetic resonance images minimizing segmentation error

This work presents a new algorithm (nonuniform intensity correction; NIC) for correction of intensity inhomogeneities in T1-weighted magnetic resonance (MR) images. The bias field and a bias-free image are obtained through an iterative process that uses brain tissue segmentation. The algorithm was validated by means of realistic phantom images and a set of 24 real images. The first evaluation phase was based on a public domain phantom dataset, used previously to assess bias field correction algorithms. NIC performed similar to previously described methods in removing the bias field from phantom images, without introduction of degradation in the absence of intensity inhomogeneity. The real image dataset was used to compare the performance of this new algorithm to that of other widely used methods (N3, SPM'99, and SPM2). This dataset included both low and high bias field images from two different MR scanners of low (0.5 T) and medium (1.5 T) static fields. Using standard quality criteria for determining the goodness of the different methods, NIC achieved the best results, correcting the images of the real MR dataset, enabling its systematic use in images from both low and medium static field MR scanners. A limitation of our method is that it might fail if the bias field is so high that the initial histogram does not show bimodal distribution for white and gray matter.     

Intrusive images and "hotspots" of trauma memories in Posttraumatic Stress Disorder: an exploratory investigation of emotions and cognitive themes

This study aimed to investigate the emotions and cognitions contained in "hotspots" of memory for trauma, as well as their associated images. Thirty-two participants at a specialist outpatient trauma clinic had experienced a range of traumatic events and met diagnostic criteria for Posttraumatic Stress Disorder (PTSD). Data were collected within an agreed protocol, involving reliving therapy. Patients described the different intrusive images of the trauma that they were re-experiencing. Their reports of cognitions and emotions during "hotspots" in their memory of the traumatic experience were recorded as part of reliving therapy. Hotspots refer to moments of peak emotional distress during the event. There was a high degree of match reported between intrusive images and hotspots. The cognitive and emotional contents of hotspots were qualitatively analysed into themes. The relative of frequency of these peritraumatic themes is presented. The exploratory findings are discussed with respect to our understanding and treatment of intrusive imagery in PTSD.     

A study of the standard brain in Japanese children: Morphological comparison with the MNI template

Functional magnetic resonance imaging (MRI) studies involve normalization so that the brains of different subjects can be described using the same coordinate system. However, standard brain templates, including the Montreal Neurological Institute (MNI) template that is most frequently used at present, were created based on the brains of Western adults. Because morphological characteristics of the brain differ by race and ethnicity and between adults and children, errors are likely to occur when data from the brains of non-Western individuals are processed using these templates. Therefore, this study was conducted to collect basic data for the creation of a Japanese pediatric standard brain. Participants in this study were 45 healthy children (contributing 65 brain images) between the ages of 6 and 9 years, who had nothing notable in their perinatal and other histories and neurological findings, had normal physical findings and cognitive function, exhibited no behavioral abnormalities, and provided analyzable MR images. 3D-T1-weighted images were obtained using a 1.5-T MRI device, and images from each child were adjusted to the reference image by affine transformation using SPM8. The lengths were measured and compared with those of the MNI template. The Western adult standard brain and the Japanese pediatric standard brain obtained in this study differed greatly in size, particularly along the anteroposterior diameter and in height, suggesting that the correction rates are high, and that errors are likely to occur in the normalization of pediatric brain images. We propose that the use of the Japanese pediatric standard brain created in this study will improve the accuracy of identification of brain regions in functional brain imaging studies involving children.     

Two useful techniques in three-dimensional electron microscopy: quarter-micron serial sectioning and stereoscopy

Quarter-micron serial sectioning is a technique useful for 3-D analyses in which light microscopical resolution is not sufficient and the maximal resolution of the electron microscope is not necessary. We propose that the technique described here is advantageous for many current electron microscopic studies in which ultrathin sections are commonly used. In particular, the sections are sturdier; they yield high-contrast images; they contain, per section, more information about the third dimension, information that can be retrieved through stereoscopy; and, when it comes to 3-D reconstruction from serial sections, less sections are needed to reconstruct tissue elements contained in a bloc of a given size. Compared to thicker sections, quarter-micron sections yield images of acceptable readability.     

Imaging of the lower cranial nerves

This article discusses the normal anatomy and pathologic entities that involve the lower cranial nerves. Normal anatomy is described and correlated with line diagrams and MR images. Distinct pathologic processes that involve the individual nerves along their various components are discussed. The imaging characteristics of these lesions are provided. Knowledge of the nuclear origins, the normal course of the cranial nerves, their func-tional components, and the imaging characteristics of pathologic lesions involving the nerves are important in any evaluation of cranial neuropathy.     

Intracranial anomalies in myelomeningocele--observation with magnetic resonance (MR) imaging

It is generally accepted that myelomeningocele frequently associates with Arnold-Chiari malformation and other anomalies of the intracranial structures. The ventriculographic and CT findings of the patients with myelomeningocele has been reported. Magnetic resonance (MR) imaging is useful to observe the coronal and sagittal images of the brain in order to speculate the etiological mechanism of myelomeningocele and its associated anomalies. We experienced three cases of myelomeningocele and reviewed their MR images using coronal and sagittal tomography in spin echo and inversion recovery technique. The morphological detail of MR images as to the intracranial structures was presented. Possible mechanism of the anomalous structures of the brain in myelomeningocele was also described.