MRI Techniques (mri + techniques)

Distribution by Scientific Domains
Distribution within Medical Sciences

Selected Abstracts

Infectious discitis in adults: 9 years experience from Al-Yarmouk Teaching Hospital in Baghdad, Iraq

Riyadh A. SAKENI
Abstract Aim:, The objective of this study was to analyse the presentation, aetiology, diagnosis, management, and outcome of infectious discitis. Methods:, A screening prospective case-finding study was carried out at Al-Yarmouk teaching hospital in Baghdad, Iraq from 1997 to 2006. Fifty adult patients (12 men and 38 women) were diagnosed with infectious discitis from different referral sources. The diagnosis was based on laboratory biochemical tests, isolation of micro-organisms from blood and needle aspiration tissue, and radiological investigations including magnetic resonance images (MRI). Results:, Of the 50 cases, 32 (64%) patients presenting within 4 weeks, 94% had pelvic and abdominal surgical interventions, 70% presented with severe neck pain and 36% had neurological deficits. Marked elevation of erythrocyte sedimentation rate and high serum C-reactive protein levels were observed in all patients. Positive blood, percutaneous disc aspiration and surgical exploration samples for Staphylococcus aureus, Streptococcus viridans, E. coli, Pseudomonas aureginosa and Candida albicans were found. Radiological images showed that disc involvement did not exceed more than one intervertebrate disc with two adjacent vertebrae. The clinical outcome was full recovery (86%), residual neurological deficits (10%) and death (4%). Conclusions:, Infectious discitis in adults should be suspected in every case presenting with severe neck or back pain, followed by pelvic or abdominal surgical interventions. Therefore, MRI techniques should be performed on every case and an early empirical antibiotic therapy is advised. [source]

A practical method for 2D multiple-animal MRI

Marc S. Ramirez MS
Abstract Purpose To investigate practical methods for achieving routine simultaneous 2D MRI of multiple animals in large-bore experimental scanners. Materials and Methods Three four-element array geometries were compared against a standard single-coil configuration in terms of image quality, ease of use, and data efficiency using a four-channel, 4.7 T small animal imaging system. Results A linear arrangement of volume resonators permits unobstructed animal preparation and use of an imaging protocol that is almost identical to the single-coil configuration without requiring any image correction or other additional postprocessing. Resulting in vivo images were visually indistinguishable from those acquired through the single-coil configuration. Conclusion The efficiency of animal studies employing 2D MRI techniques can be substantially improved by using a linear array of commercially available resonators. J. Magn. Reson. Imaging 2007;26:1162,1166. 2007 Wiley-Liss, Inc. [source]

Magnetic resonance imaging for ischemic heart disease

Hajime Sakuma MD
Abstract Cardiac MRI has long been recognized as an accurate and reliable means of evaluating cardiac anatomy and ventricular function. Considerable progress has been made in the field of cardiac MRI, and cardiac MRI can provide accurate evaluation of myocardial ischemia and infarction (MI). Late gadolinium (Gd)-enhanced MRI can clearly delineate subendocardial infarction, and the assessment of transmural extent of infarction on late enhanced MRI has been shown to be useful in predicting functional recovery of dysfunctional myocardium in patients after MI. Stress first-pass contrast-enhanced (CE) myocardial perfusion MRI can be used to detect subendocardial ischemia, and recent studies have demonstrated the high diagnostic accuracy of stress myocardial perfusion MRI for detecting significant coronary artery disease (CAD). Free-breathing, whole-heart coronary MR angiography (MRA) was recently introduced as a method that can provide visualization of all three major coronary arteries within a single three-dimensional (3D) acquisition. With further improvements in MRI techniques and the establishment of a standardized study protocol, cardiac MRI will play a pivotal role in managing patients with ischemic heart disease. J. Magn. Reson. Imaging 2007;26:3,13. 2007 Wiley-Liss, Inc. [source]

Study of order and dynamic processes in tendon by NMR and MRI

G. Navon PhD
Abstract Tendons are composed of a parallel arrangement of densely packed collagen fibrils that results in unique biomechanical properties of strength and flexibility. In the present review we discuss several advanced magnetic resonance spectroscopy (MRS) and imaging (MRI) techniques that have allowed us to better understand the biophysical properties of tendons and ligaments. The methods include multiple quantum and T2 filtering combined with NMR and MRI techniques. It is shown in detail how these techniques can be used to extract a number of useful parameters: 1) the 1H- 1H and 1H- 2H dipolar interactions; 2) the proton exchange rates between water and collagen, and between water molecules; 3) the distribution of fibril orientations; and 4) the anisotropy of diffusion. It is shown that relaxation data as a function of angular dependence can be obtained in vivo using mobile NMR sensors. Finally, this article describes how double quantum filtered (DQF) MRI can be used to image and monitor the healing process in injured tendons. J. Magn. Reson. Imaging 2007. 2007 Wiley-Liss, Inc. [source]

A Magnetization Transfer MRI Study of Deep Gray Matter Involvement in Multiple Sclerosis

Jitendra Sharma MD
ABSTRACT Background/Purpose: Gray matter involvement in multiple sclerosis (MS) is of growing interest with respect to disease pathogenesis. Magnetization transfer imaging (MTI), an advanced MRI technique, is sensitive to disease in normal appearing white matter (NAWM) in patients with MS. Design/Methods: We tested if MTI detected subcortical (deep) gray matter abnormalities in patients with MS (n= 60) vs. age-matched normal controls (NL, n= 20). Magnetization transfer ratio (MTR) maps were produced from axial proton density, conventional spin-echo, 5 mm gapless slices covering the whole brain. Region-of-interest,derived MTR histograms for the caudate, putamen, globus pallidus, thalamus, and NAWM were obtained. Whole brain MTR was also measured. Results: Mean whole brain MTR and the peak position of the NAWM MTR histogram were lower in patients with MS than NL (P < .001) and mean whole brain MTR was lower in secondary progressive (SP, n= 10) than relapsing-remitting (RR, n= 50, P < .001) patients. However, none of the subcortical gray matter nuclei showed MTR differences in MS vs. NL, RR vs. SP, or SP vs. NL. Conclusions: The MTI technique used in this cohort was relatively insensitive to disease in the deep gray matter nuclei despite showing sensitivity for whole brain disease in MS. It remains to be determined if other MRI techniques are more sensitive than MTI for detecting pathology in these areas. [source]

Clinical,Magnetic Resonance Imaging Correlations in Multiple Sclerosis

Robert Zivadinov MD
ABSTRACT Conventional magnetic resonance imaging (MRI) has routinely been used to improve the accuracy of multiple sclerosis (MS) diagnosis and monitoring, detect the effects of diseasemodifying therapy, and refine the utility of clinical assessments. However, conventional MRI measures, such as the use of lesion volume and count of gadolinium-enhancing and T2 lesions, have insufficient sensitivity and specificity to reveal the true degree of pathological changes occurring in MS. Newer metrics of MRI analysis, including T1-weighted hypointense lesions (black holes) and central nervous system (CNS) atrophy measures, are able to capture a more global picture of the range of tissue alterations caused by inflammation, demyelination, axonal loss, and neurodegeneration. There is mounting evidence that these MRI measures correlate well with existing and developing neurological impairment and disability. In so doing, these MRI techniques can help elucidate the mechanisms underlying the pathophysiology and natural history of MS. The current understanding is that T1 black holes and CNS atrophy more accurately reflect the neurodegenerative and destructive components of the MS disease process. Therefore, the shortand long-term studies that aim to measure the degree and severity of the neurodegenerative MS disease process should incorporate these MRI metrics as part of their standard routine MRI protocols. [source]

Magnetic Resonance Imaging Monitoring of Multiple Sclerosis Lesion Evolution

Matilde Inglese MD
ABSTRACT The characteristic feature of multiple sclerosis (MS) pathology is the demyelinated plaque distributed throughout the central nervous system. Although MS is a primary demyelinating disease, acute axonal injury is common in actively demyelinating MS lesions and it is considered one of the major determinants of neurological deficit. Magnetic resonance imaging (MRI) has had a dramatic impact on MS in both the clinical practice and basic science settings. Techniques such as T2-weighted and gadolinium-enhanced T1-weighted MRI are very sensitive in detecting lesions and, thus, increase the level of certainty of MS diagnosis. Conventional MRI has also improved our understanding of the pathogenesis of the disease and has provided objective and reliable measures to monitor the effect of experimental treatments in clinical trials. However, conventional MR,I does not provide specific information on the heterogeneous pathologic substrate of MS lesions. Advanced MRI techniques, such as magnetization transfer imaging, diffusion tensor imaging, and proton MR spectroscopy, offer the unprecedented ability to observe and quantify pathological changes in lesions and normal-appearing brain tissue over time. The present review will discuss the major contributions of conventional MRI and quantitative MRI techniques to understand how individual MS lesions evolve. [source]

Bilateral Internal Carotid Artery Dissection Mimicking Inflammatory Demyelinating Disease

C. Lie MD
ABSTRACT Background and Purpose. Internal carotid artery (ICA) dissection (ICAD) may be extremely difficult to diagnose only on the basis of historical information and clinical signs, and even standard brain imaging (computed tomography [CT], T2-weighted magnetic resonance imaging [MRI]) may not be sufficient to delineate the underlying pathology clearly, as shown in this case. Methods. The clinical presentation and parenchymal lesion pattern on CT were suggestive of inflammatory demyelinating disease, and additional multiparametric MRI was per-formed. Results. Diffusion-weighted MRI, magnetic resonance angiography, and perfusion-weighted MRI revealed acute ischemic lesions, bilateral ICA obstruction, and bilateral hypoperfusion in the middle cerebral artery territories. Bilateral ICAD was confirmed by Doppler and duplex ultrasound, and anticoagulation therapy was initiated. A follow-up examination showed recanalization of the obstructed ICAs and the normalization of cerebral perfusion. Conclusion. This case illustrates the importance of demonstrating the pathology and the value of multiparametric MRI techniques for the diagnosis and monitoring of ICAD and its hemodynamic consequences. [source]

Magnetization transfer ratio as a predictor of malignancy in breast lesions: Preliminary results

Ruth Helena Morais Bonini
Abstract MRI is an important tool for investigating breast cancer. Although recognized as the method of choice for screening high-risk patients, and for other indications the role of MRI for lesion characterization remains controversial. Recently some authors have advocated the use of morphologic and postcontrast features for this purpose. Quantitative breast MRI techniques have not been applied extensively in breast diseases. Magnetization transfer (MT) is a quantitative MR technique commonly used to investigate neurological diseases. In breast diseases the use of MT has been limited to improving visualization of areas of enhancement in postcontrast images. The purpose of this study was to evaluate the feasibility and utility of MT in discriminating benign from malignant breast lesions. Fifty-two lesions, BIRADS 4 and 5, from 49 patients, were prospectively evaluated using the MT ratio (MTR). Patients were divided into two groups: benign and malignant lesions. The MTR of fat, pectoralis major muscle, fibroglandular tissue, and breast lesions were calculated. A statistically significant difference was found between MTR from benign and malignant lesions (P < 0.001). Preliminary results suggest that MT can be used to evaluate breast lesions. Further studies are necessary to better define the utility and applicability of this technique. Magn Reson Med 59:1030,1034, 2008. 2008 Wiley-Liss, Inc. [source]

Robust automated shimming technique using arbitrary mapping acquisition parameters (RASTAMAP)

L. Martyn Klassen
Abstract Quantitative MRI techniques as well as methods such as blood oxygen level-dependent (BOLD) imaging and in vivo spectroscopy require stringent optimization of magnetic field homogeneity, particularly when using high main magnetic fields. Automated shimming approaches require a method of measuring the main magnetic field, B0, followed by adjusting the currents in resistive shim coils to maximize homogeneity. A robust automated shimming technique using arbitrary mapping acquisition parameters (RASTAMAP) using a 3D multiecho gradient echo sequence that measures B0 with high precision was developed. Inherent compensation and postprocessing methods enable removal of artifacts due to hardware timing errors, gradient propagation delays, gradient amplifier asymmetry, and eddy currents. This allows field maps to be generated for any field of view, bandwidth, resolution, or acquisition orientation without custom tuning of sequence parameters. Field maps of an aqueous phantom show 1 Hz variation with altered acquisition orientations and bandwidths. Subsequent fitting of measured shim coil field maps allows calculation of shim currents to produce optimum field homogeneity. Magn Reson Med 51:881,887, 2004. 2004 Wiley-Liss, Inc. [source]

MRI in ocular drug delivery

S. Kevin Li
Abstract Conventional pharmacokinetic methods for studying ocular drug delivery are invasive and cannot be conveniently applied to humans. The advancement of MRI technology has provided new opportunities in ocular drug-delivery research. MRI provides a means to non-invasively and continuously monitor ocular drug-delivery systems with a contrast agent or compound labeled with a contrast agent. It is a useful technique in pharmacokinetic studies, evaluation of drug-delivery methods, and drug-delivery device testing. Although the current status of the technology presents some major challenges to pharmaceutical research using MRI, it has a lot of potential. In the past decade, MRI has been used to examine ocular drug delivery via the subconjunctival route, intravitreal injection, intrascleral injection to the suprachoroidal space, episcleral and intravitreal implants, periocular injections, and ocular iontophoresis. In this review, the advantages and limitations of MRI in the study of ocular drug delivery are discussed. Different MR contrast agents and MRI techniques for ocular drug-delivery research are compared. Ocular drug-delivery studies using MRI are reviewed. Copyright 2008 John Wiley & Sons, Ltd. [source]

An introduction to coil array design for parallel MRI

Michael A. Ohliger
Abstract The basic principles of radiofrequency coil array design for parallel MRI are described from both theoretical and practical perspectives. Because parallel MRI techniques rely on coil array sensitivities to provide spatial information about the sample, a careful choice of array design is essential. The concepts of coil array spatial encoding are first discussed from four qualitative perspectives. These qualitative descriptions include using coil arrays to emulate spatial harmonics, choosing coils with selective sensitivities to aliased pixels, using coil sensitivities with broad k -space reception profiles, and relying on detector coils to provide a set of generalized projections of the sample. This qualitative discussion is followed by a quantitative analysis of coil arrays, which is discussed in terms of the baseline SNR of the received images as well as the noise amplifications (g -factor) in the reconstructed data. The complications encountered during the experimental evaluation of coil array SNR are discussed, and solutions are proposed. A series of specific array designs are reviewed, with an emphasis on the general design considerations that motivate each approach. Finally, a set of special topics is discussed, which reflect issues that have become important, especially as arrays are being designed for more high-performance applications of parallel MRI. These topics include concerns about the depth penetration of arrays composed of small elements, the use of adaptive arrays for systems with limited receiver channels, the management of inductive coupling between array elements, and special considerations required at high field strengths. The fundamental limits of spatial encoding using coil arrays are discussed, with a primary emphasis on how the determination of these limits impacts the design of optimized arrays. This review is intended to provide insight into how arrays are currently used for parallel MRI and to place into context the new innovations that are to come. Copyright 2006 John Wiley & Sons, Ltd. [source]

Translating pathology in multiple sclerosis: the combination of postmortem imaging, histopathology and clinical findings

A. Seewann
Background,,, Studies combining postmortem magnetic resonance imaging (MRI) and histopathology have provided important insights into the abnormalities reflected by MRI. Materials and methods,,, A short overview of these studies applied to multiple sclerosis (MS) is provided in this review, and the Amsterdam postmortem imaging protocol is specifically highlighted. Conclusion,,, Postmortem MRI and histopathology correlation studies have enabled a direct translation of basic pathology in MS to the clinical setting, and have simultaneously served as a biological validation of new MRI techniques. [source]