Number Of Magnetic Resonance Imaging Research Articles

Design considerations and experimental results for MRI systems using HTS magnets

An increasing number of magnetic resonance imaging (MRI) systems using high temperature superconductors (HTS) magnets have been designed and constructed, with detailed results of their performance now available. Features of REBCO and BSCCO conductors are described as they pertain to use in high homogeneity magnets, with emphasis placed on the practical use of these conductors in magnets. Methods of coil winding are discussed, in particular the differences between pancake and layer winding techniques. Design considerations for HTS magnets are presented in light of the difficulties presented by quench in these magnets, but also in terms of the features of HTS magnets afforded by their high operating temperatures, namely robust cryogen free operation and the potential to use unshielded gradient coils. Drawing on two example MRI systems, namely a 3 T BSCCO brain imaging magnet developed in Japan and a 1.5 T REBCO orthopaedic imaging system developed in New Zealand, the report details real-world stability and homogeneity of HTS-MRI systems, in particular with regards to the screening current effects observed in these systems. It is concluded that, apart from conductor cost, there are currently no technical obstacles to use of HTS-MRI systems.

ADHD and Cerebellar Vermis Tumor: DTI Analysis of an Incidental Finding

The increase in number of magnetic resonance imaging (MRI) scans for investigation of neurological diseases in childhood and adolescence leads to increase of incidental findings of central nervous system (CNS) tumors in these stages of life. Among MRI techniques, diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) have been increasingly used in brain studies. These images are based on random motion of water molecules in the body, which can change depending on constitution and geometry of biological tissues, as well as the existence of pathologies. This paper reports the use of DTI and DWI to evaluation of a CNS tumor incidentally detected in a patient diagnosed previously with Attention Deficit Hyperactivity Disorder (ADHD). He was diagnosed at age 9 and has been treated with medicines and psycho-pedagogical therapies. At age 15 a MRI detected a cerebellar vermis tumor with a volume of 2 cm 3 . Due to parental decision, the patient did not undergo any surgical intervention. During the follow-up period we did not observe significant changes in tumor size or diffusion directions in the tumor and surrounding brain tissues. The main brain tracts presented normal diffusion patterns, both in terms of size and geometry. The DTI analysis showed that lesion was quite homogeneous and isotropic, with no significant restriction of diffusion. There also were no significant diffusion pattern changes in other regions of the brain which possibly could be related to ADHD. So, given the characteristics of lesion and the patient's clinical symptoms, it cannot be directly related to ADHD.

In vivo MRI visualization of U87 glioblastoma development dynamics in the model of orthotopic xenotransplantation to the SCID mouse

Glioblastoma is an extremely aggressive type of brain tumor. The average life span of patients with this diagnosis is 9–12 months. The development of adequate experimental models is required for the search of efficient approaches for the therapy and diagnostics of this disease. In this study, we used a number of magnetic resonance imaging (MRI) methods for describing the growth dynamics and cell morphology of U87 glioblastoma orthotopically xenotransplanted into mice of the immunodeficient SCID line. A comparison of the visualization efficiency of the developing tumor by means of T1- and T2-weighted images (obtained using an ultra-high field Bruker BioSpec (11.7 T) tomograph) demonstrated that T1-weighted images do not provide the required contrast of a pathological tissue relative to a healthy one (as opposed to T2-weighted images) due to the strong longitudinal magnetization of the tomograph’s magnetic field. of T1-weighted images, together with the intravenous introduction of paramagnetic nanoparticles (manganese oxide, MnO) significantly increased the tumor/normal tissue contrast in the MRI images. The study of the dynamics of the tumor cell growth by means of T2-weighted images demonstrated that the tumor development starts no earlier than 3 weeks after the intracranial introduction of the U87 cell culture (and the tumor cells grow exponentially). Thus, the methods of T1- and T2-weighted and MnO-enforced MRI were developed and characterized on the model of orthotopic xenotransplantation of U87 human glioblastoma cells into immunodeficient SCID animals, which can be used as the in vivo experimental model for checking new antitumor drugs and schemes of the treatment of the human brain’s oncological diseases.

Automatic brain MR image denoising based on texture feature-based artificial neural networks.

Noise is one of the main sources of quality deterioration not only for visual inspection but also in computerized processing in brain magnetic resonance (MR) image analysis such as tissue classification, segmentation and registration. Accordingly, noise removal in brain MR images is important for a wide variety of subsequent processing applications. However, most existing denoising algorithms require laborious tuning of parameters that are often sensitive to specific image features and textures. Automation of these parameters through artificial intelligence techniques will be highly beneficial. In the present study, an artificial neural network associated with image texture feature analysis is proposed to establish a predictable parameter model and automate the denoising procedure. In the proposed approach, a total of 83 image attributes were extracted based on four categories: 1) Basic image statistics. 2) Gray-level co-occurrence matrix (GLCM). 3) Gray-level run-length matrix (GLRLM) and 4) Tamura texture features. To obtain the ranking of discrimination in these texture features, a paired-samples t-test was applied to each individual image feature computed in every image. Subsequently, the sequential forward selection (SFS) method was used to select the best texture features according to the ranking of discrimination. The selected optimal features were further incorporated into a back propagation neural network to establish a predictable parameter model. A wide variety of MR images with various scenarios were adopted to evaluate the performance of the proposed framework. Experimental results indicated that this new automation system accurately predicted the bilateral filtering parameters and effectively removed the noise in a number of MR images. Comparing to the manually tuned filtering process, our approach not only produced better denoised results but also saved significant processing time.

Baseline clinical status as a predictor of methylprednisolone response in multiple sclerosis relapses

Background: To date, there are no available factors to predict the outcome after multiple sclerosis relapse. Aim: To investigate factors that may be useful for predicting response to methylprednisolone treatment, following a relapse of multiple sclerosis (MS). Methods: The study included 48 MS patients enrolled in a double-blind multicenter trial to receive intravenous versus oral high-dose methylprednisolone treatment. Associations were sought between the disability status prior to relapse and the relapse severity, determined by changes in the Expanded Disability Status Scale (EDSS) score, as well as the improvements after treatment. We also analyzed the relationships between the number of magnetic resonance imaging (MRI) gadolinium-enhancing lesions (Gd+) and improvement. Results: A higher EDSS score before relapse was associated with more severe relapses (p = 0.04) and less marked improvement (odds ratio (OR) 1.8; 95% CI (1.2–2.2); p = 0.05) after methylprednisolone treatment. Relapse severity (p = 0.29) and the number of Gd+ lesions at relapse (p = 0.41) were not related with improvement. Conclusions: Clinical baseline status prior to MS relapse is a predictor of response to methylprednisolone treatment.

Appropriate, quality imaging tests through linkage of payment to guidelines, accreditation and training.

The volume of imaging tests has risen more rapidly than most other drivers of health care costs, with the number of magnetic resonance imaging (MRI) and computed tomography (CT) tests increasing threefold between 1995 and 2010.[1][1],[2][2] It is estimated that 10%–30% of imaging tests are done

Magnetic resonance imaging in a patient with an implantable cardioverter-defibrillator

The number of patients with cardiac pacemakers (PM), implantable cardioverter-defibrillators (ICD) and cardiac resynchronisation therapy PM systems is increasing. The number of magnetic resonance imaging (MRI) examinations is also growing and amounts to about 60 million tests per year worldwide. The presence of an ICD is still considered to be an absolute contraindication to MRI by most experts. We present a patient with an implanted ICD who successfully underwent brain MRI with use of special precautions.

Brain perfusion imaging: How does it work and what should I use?

In the last 15 years there has been a relative explosion in the number of magnetic resonance imaging (MRI) techniques and developments related to cerebral perfusion. Given the variety of perfusion methods available, it is often difficult to decide which technique would be best for a particular clinical question or patient. In this review article we discuss the more common techniques, review how they are performed, and summarize the optimal technique or techniques for a variety of clinical situations.

Neuropathological substrates and structural changes in late-life depression: the impact of vascular burden

A first episode of depression after 65 years of age has long been associated with both severe macrovascular and small microvascular pathology. Among the three more frequent forms of depression in old age, post-stroke depression has been associated with an abrupt damage of cortical circuits involved in monoamine production and mood regulation. Late-onset depression (LOD) in the absence of stroke has been related to lacunes and white matter lesions that invade both the neocortex and subcortical nuclei. Recurrent late-life depression is thought to induce neuronal loss in the hippocampal formation and white matter lesions that affect limbic pathways. Despite an impressive number of magnetic resonance imaging (MRI) studies in this field, the presence of a causal relationship between structural changes in the human brain and LOD is still controversial. The present article provides a critical overview of the contribution of neuropathology in post-stroke, late-onset, and late-life recurrent depression. Recent autopsy findings challenge the role of stroke location in the occurrence of post-stroke depression by pointing to the deleterious effect of subcortical lacunes. Despite the lines of evidences supporting the association between MRI-assessed white matter changes and mood dysregulation, lacunes, periventricular and deep white matter demyelination are all unrelated to the occurrence of LOD. In the same line, neuropathological data show that early-onset depression is not associated with an acceleration of aging-related neurodegenerative changes in the human brain. However, they also provide data in favor of the neurotoxic theory of depression by showing that neuronal loss occurs in the hippocampus of chronically depressed patients. These three paradigms are discussed in the light of the complex relationships between psychosocial determinants and biological vulnerability in affective disorders.

Treatment of a large and symptomatic septum pellicidum cyst with endoscopic fenestration in a child—Case report and review of the literature

Septum pellucidum cysts (SPCs) are seen in 10% of adults and s many as 82% of neonates and are considered a normal variant hat usually do not require any surgical treatment [1,2]. The expanion of SPCs was reported to be as low as 0.04% in a database of a arge number of magnetic resonance images (MRIs) [3]. Expandng SPCs may become symptomatic, showing signs and symptoms f raised intracranial pressure and mass effect. Almost 100 cases f symptomatic SPCs have been reported so far in the literature 4–24]. We report an unusually large SPC in a four-year-old boy with ymptoms of increased intracranial pressure, paraparesis, and gait isorder. The patient dramatically improved after endoscopic fenstration of the SPC into the lateral ventricles. In this case report, we ocus on the rarity and the clinical importance of this large sympomatic SPC, and we present a review of the relevant literature.

Abnormal asymmetry of white matter integrity in schizophrenia revealed by voxelwise diffusion tensor imaging

A number of magnetic resonance imaging (MRI) studies have revealed morphological cortical asymmetry in the normal human brain, and reduction or inversion of such hemispheric asymmetry has been reported in schizophrenia. On the other hand, diffusion tensor imaging (DTI) studies have reported inconsistent findings concerning abnormal asymmetry of white matter integrity in schizophrenia. Our aim was to confirm whether there is reduced or inverted asymmetry of white matter integrity in the whole brain in schizophrenia. For this study, 26 right-handed schizophrenia patients, and 32 matched healthy control subjects were investigated. Voxelwise analysis of DTI data was performed using the tract-based spatial statistics. The fractional anisotropy (FA) images were normalized and projected onto the symmetrical white matter skeleton, and the laterality index (LI) of FA, determined by 2 × (left - right)/(left + right), was calculated. The results reveal that schizophrenia patients and healthy controls showed similar patterns of overall FA asymmetries. In the group comparison, patients showed significant reduction of LI in the external capsule (EC), and posterior limb of the internal capsule (PLIC). The EC cluster revealed increased rightward asymmetry, and the PLIC cluster showed reduced leftward asymmetry. Rightward-shift of FA in the EC cluster correlated with negative symptom severity. Considering that the EC cluster includes the uncinate and inferior occipitofrontal fasciculi, which have connections to the orbitofrontal cortex, abnormal asymmetry of white matter integrity in schizophrenia may play a crucial role in the pathogenesis of schizophrenia, through the altered connectivity to the orbitofrontal cortex.

Facts, Facts, Facts: What Is a Physician to Do?

IT IS A CLICHE TO OBSERVE THAT EVERYONE LIVES IN A GLOBAL economy. Anyone who travels internationally can see how rapidly the world is becoming similar in terms of shops, goods, and services. Perhaps it is timely to reengage physicians in thediscussion of international comparativedata about health care and to ask why the United States is so provincial in designing the systems by which care is delivered. Recently the Organisation for Economic Co-operation and Development (OECD) published Health at a Glance 2009, the annual compilation of health statistics from 30 countries. Even though most of the data are from 2007, these statistics provide revealing snapshots of various aspects of health and health systems, especially when comparing several US statistics to comparable statistics from other countries. Seventeen comparisons were selected to be representative of the different concepts (health status, nonmedical determinants of health, health work force, health care activities, quality of care, and health expenditures) that are covered in the OECD report. The comparisons (reported as United States; another country) are as follows. 1. Life expectancy in the United States is 78.1 years; in Switzerland, it is 81.9 years. 2. Years of life lost before age 70 per 100 000 men is 6291; in Italy, it is 3605. 3. The age-standardized ischemic heart mortality rate per 100 000 males is 145; in France, it is 54. 4. The percentage of newborns weighing less than 2500 g is 8.3%; in Ireland, it is 5%. 5. The percentage of children aged 11 to 15 years who are overweight or obese is 29.8%; in Belgium, it is 10.5%. 6. The number of practicing physicians per 1000 population is 2.4; in Belgium, it is 4.0. 7. The percentage of US physicians who are non-US trained is 25.9%; in the Netherlands, the percentage of non-Netherlands−trained physicians is 6.3%. 8. The ratio of the self-employed specialist’s average salary to the average salary of a full-time employee is 5.6:1; in Germany, the ratio is 4.1:1. For a selfemployed general practitioner, the comparable ratio is 3.7:1; in Canada, it is 3.1:1. 9. The number of physician consultations per capita is 3.8; in Germany, it is 7.5, and in Japan, it is 13.6. 10. The number of consultations per physician per year (data are from administrative sources and include visits in physician offices, hospital outpatient clinics, or patient homes) is 1570; in Korea, it is 7251 and in Canada, it is 3335 (fee-for-service visits only). 11. The number of magnetic resonance imaging (MRI) machines per 1 000 000 of population is 25.9; in Japan, it is 40.1; in Canada, it is 6.7. 12. The number of MRI examinations per 1000 population is 91.2; in Canada, the number is 31.2. 13. The hospital discharge rate is 126 per 1000; in France, it is 274. 14. The coronary revascularization rate is 521 per 100 000; in Switzerland, it is 144 and in Ireland, it is 128. 15. The number of patients treated for end-stage renal failureis169per100 000population; intheNetherlands, it is 77. 16. The age-sex standardized in-hospital death rate for acute myocardial infarction is 5.1%; in Sweden, it is 2.9%. 17. Health expenditures are 16.0% of gross domestic product; in France, 11% and in Ireland, 7.6%.

Serotonin transporter gene polymorphism implicates reduced orbito-frontal cortex in obsessive–compulsive disorder

Although a number of magnetic resonance imaging (MRI) and genetic studies have been performed on obsessive–compulsive disorder (OCD), only limited studies in which genetic and neuroanatomical variables are evaluated concurrently have been performed. Therefore, the aim of our present study is (to understand) better understanding how genetic variation in the promoter region of the 5-HTT gene (5-HTTLPR) is associated with key brain structures in OCD, orbito-frontal cortex (OFC), thalamus and anterior cingulate. 5-HTT genotypes (SS, SL, LL) were determined for 40 patients with OCD and the same number of healthy controls. MRI-derived volumes of the OFC, thalamus, and anterior cingulate were determined by reliable tracing techniques. Volumetric measurements were made with T1-weighted coronal MRI images, with 1.5-mm-thick slices, at 1.5 T, and were done blindly. In comparison with controls, OCD patients demonstrated volumes reduction in OFC, increased volumes of thalamus and total white matter volumes, but no difference in total brain volume, total gray matter volumes and anterior cingulate volumes. No significant difference was observed in allelic frequencies between the patients and controls. The stronger effects of 5-HTT polymorphism on brain morphology in OCD than those in controls were determined in the both OFC and thalamus. On the other hand, for the OCD patients, ANCOVA revealed a significant main effect of genotype for both the OFC and thalamus and a significant genotype-by-side interaction for the OFC, demonstrating that the short variants had a smaller right OFC than the long variants. In conclusion, we found a significant genotype-diagnosis interaction effects on key brain structures, with a stronger effects of 5-HTT polymorphism in OFC and thalamus of OCD patients, whereas no morphological changes related to the polymorphism were found in normal individuals.

Briefly

Diagnostic imaging: There's been significant growth in the number of magnetic resonance imaging (MRI) and computed tomography (CT) scanners in Canada over the past 4 years but the number of medical imaging professionals has remained relatively constant, according to the Canadian Institute for Health

Independent Component Analysis for Magnetic Resonance Image Analysis

Independent component analysis (ICA) has recently received considerable interest in applications of magnetic resonance (MR) image analysis. However, unlike its applications to functional magnetic resonance imaging (fMRI) where the number of data samples is greater than the number of signal sources to be separated, a dilemma encountered in MR image analysis is that the number of MR images is usually less than the number of signal sources to be blindly separated. As a result, at least two or more brain tissue substances are forced into a single independent component (IC) in which none of these brain tissue substances can be discriminated from another. In addition, since the ICA is generally initialized by random initial conditions, the final generated ICs are different. In order to resolve this issue, this paper presents an approach which implements the over-complete ICA in conjunction with spatial domain-based classification so as to achieve better classification in each of ICA-demixed ICs. In order to demonstrate the proposed over-complete ICA, (OC-ICA) experiments are conducted for performance analysis and evaluation. Results show that the OC-ICA implemented with classification can be very effective, provided the training samples are judiciously selected.

Efficient cardiac diffusion tensor MRI by three-dimensional reconstruction of solenoidal tensor fields

Tensor tomography is being investigated as a technique for reconstruction of in vivo diffusion tensor fields that can potentially be used to reduce the number of magnetic resonance imaging (MRI) measurements. Specifically, assessments are being made of the reconstruction of cardiac diffusion tensor fields from 3D Radon planar projections using a filtered backprojection algorithm in order to specify the helical fiber structure of myocardial tissue. Helmholtz type decomposition is proposed for 3D second order tensor fields. Using this decomposition a Fourier projection theorem is formulated in terms of the solenoidal and irrotational components of the tensor field. From the Fourier projection theorem, two sets of Radon directional measurements, one that reconstructs the solenoidal component and one that reconstructs the irrotational component of the tensor field, are prescribed. Based on these observations filtered backprojection reconstruction formulae are given for the reconstruction of a 3D second order tensor field and its solenoidal and irrotational components from Radon projection measurements. Computer simulations demonstrate the validity of the mathematical formulations and demonstrate that a realistic model of the helical fiber structure of the myocardial tissue specifies a diffusion tensor field for which the first principal vector (the vector associated with the maximum eigenvalue) of the solenoidal component accurately approximates the first principal vector of the diffusion tensor. A priori knowledge of this allows the orientation of the myocardial fiber structure to be specified utilizing one half of the number of MRI measurements of a normal diffusion tensor field study.

Immune and non-immune actions of interferon-beta-Ib on primary human neural cells.

Systemic interferon-beta-Ib (IFN-beta-Ib) reduces the frequency of clinical exacerbations and the number of magnetic resonance imaging (MRI)-defined lesions in patients with relapsing-remitting MS. The basis for this clinical effect is not understood. While IFN-beta-Ib has been demonstrated to have antiproliferative and immunomodulatory effects on the systemic immune system, its actions on neural cells could also contribute to its therapeutic efficacy. In this study, we have examined possible immune and non-immune effects of IFN-beta-Ib on CNS-derived primary human cells. With respect to immune-related effects, application of IFN-beta-Ib did not decrease basal expression of HLA-DR on astrocytes or microglia, and it reduced the IFN-gamma-enhanced HLA-DR expression on adult human astrocytes only at high concentrations (1000 IU ml-1); IFN-beta-Ib at all concentrations tested did not reduce the IFN-gamma-enhanced HLA-DR expression by fetal astrocytes or adult microglial cells. In contrast, but in correspondence with the literature, the IFN-gamma-enhanced HLA-DR expression on a glioma cell line was attenuated by IFN-beta-Ib in a dose-dependent manner. With respect to non-immune effects, the number of adult human oligodendrocytes and their state of morphological differentiation were not affected by IFN-beta-Ib. Proliferation of the mitotically active fetal human astrocytes, however, was reduced by IFN-beta-Ib treatment. Lactate dehydrogenase assays revealed that IFN-beta-Ib was not toxic to neural cells, including adult oligodendrocytes and fetal human neurons. We conclude that IFN-beta-Ib lacks efficacy in down-regulating HLA-DR expression by primary human neural cells and that regulation of MHC class II antigens is unlikely to be a mechanism for its beneficial effect in MS. Finally, the lack of toxicity of IFN-beta-Ib on human neural cells is important for a drug that will probably be used widely.