High Field Strength Magnetic Resonance Research Articles

Orientation changes in the cruciate ligaments of the knee during skeletal growth: A porcine model.

Musculoskeletal injuries in pediatric patients are on the rise, including significant increases in anterior cruciate ligament (ACL) injuries. Previous studies have found major anatomical changes during skeletal growth in the soft tissues of the knee. Specifically, the ACL and the posterior cruciate ligament (PCL) change in their relative orientation to the tibial plateau throughout growth. In order to develop age-specific treatments for ACL injuries, the purpose of this study was to characterize orientation changes in the cruciate ligaments of the Yorkshire pig, a common pre-clinical model, during skeletal growth in order to verify the applicability of this model for pediatric musculoskeletal studies. Hind limbs were isolated from female Yorkshire pigs ranging in age from newborn to late adolescence and were then imaged using high field strength magnetic resonance imaging. Orientation changes were quantified from the magnetic resonance images using image segmentation software. Statistically significant increases were found in the coronal and sagittal angles of the ACL relative to the tibial plateau during pre-adolescent growth. Additional changes were observed in the PCL angle, Blumensaat angle, intercondylar roof angle, and the aspect ratio of the intercondylar notch. Only the sagittal angle of the ACL relative to the tibial plateau experienced statistically significant changes through late adolescence. The age-dependent properties of the ACL and PCL in the female pig mirrored results found in female human patients, suggesting that the porcine model may provide a pre-clinical platform to study the cruciate ligaments during skeletal growth. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2725-2732, 2017.

Effect of Magnetic Resonance Applications on Dental Amalgam Phase Changes

Aim: The aim of this study was to examine the potential for low- versus high-field strength magnetic resonance applications to effect phase changes in high-copper dental amalgam as detected by X-ray diffraction (XRD) analysis. Materials and Methods: Disk-shaped samples (5 x 1 mm2) of amalgam filling were prepared (n = 90) and were thermocycled for 1000 cycles. The samples were then divided into three groups that were exposed to a 0.2 tesla or a 1.5 tesla magnetic field, or received no magnetic field exposure as a control. The samples were subsequently examined by XRD for phase determination 1, 7, and 30 days later. Results: The relationships between the gama, gama1, and eta phases, as well as the mercury peak intensities, were statistically analyzed using analysis of variance and the Kruskal Wallis test. No statistically significant differences were observed (p > 0.05). There were also no significant time-dependent differences observed between the gama, gama1, and eta phases, or in the mercury peak intensities, of the groups, according to the Friedman test (p > 0.05). Conclusion: The results of this study indicate that exposure to a magnetic field via magnetic resonance imaging does not affect the structure of dental amalgam. Keywords: Dental amalgam, magnetic resonance imaging, x-ray diffraction.

Assessment of female ballet dancers' ankles in the en pointe position using high field strength magnetic resonance imaging.

The en pointe position of the ankle in ballet is extreme. Previously, magnetic resonance imaging (MRI) of ballet dancers' ankles en pointe was confined to a low field, open MR device. To develop a reproducible ankle MRI protocol for ballet dancers en pointe and to assess the positions of the key structures in the dancers ankles. Six female ballet dancers participated; each was randomly assigned to stand en pointe while one of her feet and ankles was splinted with wooden rods affixed with straps or to begin with the ankle in neutral position. She lay in an MR scanner with the ankle inside a knee coil for en pointe imaging and inside an ankle/foot coil for neutral position imaging. Proton density weighted images with and without fat suppression and 3D water excitation gradient recalled echo images were obtained en pointe and in neutral position in sagittal, axial, and coronal planes. We compared the bones, cartilage, and soft tissues within and between positions. No difficulties using the protocol were encountered. En pointe the posterior articular surface of the tibial plafond was incongruent with the talar dome and rested on the posterior talus. The posterior edge of the plafond impinged Kager's fat pad. All participants exhibited one or more small ganglion cysts about the ankle and proximal foot, as well as fluid accumulation in the flexor and fibularis tendon sheaths. Our MRI protocol allows assessment of female ballet dancers' ankles in the extreme plantar flexion position in which the dancers perform. We consistently noted incongruence of the talocrural joint and convergence of the tibia, talus, and calcaneus posteriorly. This protocol may be useful for clinicians who evaluate dancers.

Quantification of subcortical gray‐matter vascularization using 7 Tesla time‐of‐flight angiography

Background The integrity of subcortical brain nuclei is associated with maintenance of regular cognitive performance levels and has been shown to be particularly affected by aging-related vascular pathology. This study aims to demonstrate applicability of high field strength magnetic resonance angiography at 7 Tesla (7T) for assessment of interindividual variation in subcortical vascularization. Methods Two healthy female subjects without known history of cerebrovascular disease or malformation, aged 43 and 86 years, respectively, were administered three-dimensional (3D) high-resolution time-of-flight (TOF) magnetic resonance angiography at 7T. The FreeSurfer software package was used for automated parcellation and assessment of subcortical volumes. For each volume, mean regional intensities were calculated based on the TOF contrast as a quantitative reflection of regional subcortical gray-matter vascularization. Results While volumes of the subcortical brain region assessed did not differ significantly (30.2 and 27.8 mL, P = 0.78), mean intensities were significantly reduced in the older participant (10%, P = 0.004). Mean intensities could be assessed for each participant for 14 subcortical structures, strongest differences were observable for the left and right Thalamus (T [left, right] = 3.85, 3.82; P [left, right] = 0.002, 0.003). Conclusions High-resolution TOF magnetic resonance angiography may be used in combination with automated volume-based parcellation to quantify regional subcortical vascularization and to assess interindividual differences. Additional studies are necessary to assess its potential use in clinical trials on cerebrovascular integrity in a context of aging-related brain change.

Technological advances in the surgical treatment of movement disorders.

Technological innovations have driven the advancement of the surgical treatment of movement disorders, from the invention of the stereotactic frame to the adaptation of deep brain stimulation (DBS). Along these lines, this review will describe recent advances in inserting neuromodulation modalities, including DBS, to the target, and in the delivery of therapy at the target. Recent radiological advances are altering the way that DBS leads are targeted and inserted, by refining the ability to visualize the subcortical targets using high-field strength magnetic resonance imaging and other innovations, such as diffusion tensor imaging, and the development of novel targeting devices enabling purely anatomical implantations without the need for neurophysiological monitoring. New portable computed tomography scanners also are facilitating lead implantation without monitoring, as well as improving radiological verification of DBS lead location. Advances in neurophysiological mapping include efforts to develop automatic target verification algorithms, and probabilistic maps to guide target selection. The delivery of therapy at the target is being improved by the development of the next generation of internal pulse generators (IPGs). These include constant current devices that mitigate the variability introduced by impedance changes of the stimulated tissue and, in the near future, devices that deliver novel stimulation patterns with improved efficiency. Closed-loop adaptive IPGs are being tested, which may tailor stimulation to ongoing changes in the nervous system, reflected in biomarkers continuously recorded by the devices. Finer-grained DBS leads, in conjunction with new IPGs and advanced programming tools, may offer improved outcomes via current steering algorithms. Finally, even thermocoagulation-essentially replaced by DBS-is being advanced by new minimally-invasive approaches that may improve this therapy for selected patients in whom it may be preferred. Functional neurosurgery has a history of being driven by technological innovation, a tradition that continues into its future.

High field strength magnetic resonance imaging in paediatric brain tumour surgery—its role in prevention of early repeat resections

The purpose of this study is to compare the surgical and imaging outcome in children who underwent brain tumour surgery with intention of complete tumour resection, prior to and following the start of intra-operative MRI (ioMRI) service. ioMRI service for brain tumour resection commenced in October 2009. A cohort of patients operated between June 2007 and September 2009 with a pre-surgical intention of complete tumour resection were selected (Group A). A similar number of consecutive cases were selected from a prospective database of patients undergoing ioMRI (Group B). The demographics, imaging, pathology and surgical outcome of both groups were compared. Thirty-six of 47 cases from Group A met the inclusion criterion and 36 cases were selected from Group B; 7 of the 36 cases in Group A had unequivocal evidence of residual tumour on the post-operative scan; 5 (14%) of them underwent repeat resection within 6 months post-surgery. In Group B, ioMRI revealed unequivocal evidence of residual tumour in 11 of the 36 cases following initial resection. In 10 of these 11 cases, repeat resections were performed during the same surgical episode and none of these 11 cases required repeat surgery in the following 6 months. Early repeat resection rate was significantly different between both groups (p = 0.003). Following the advent of ioMRI at our institution, the need for repeat resection within 6 months has been prevented in cases where ioMRI revealed unequivocal evidence of residual tumour.

Targeting Vascular Amyloid in Arterioles of Alzheimer Disease Transgenic Mice With Amyloid β Protein Antibody-Coated Nanoparticles

The relevance of cerebral amyloid angiopathy (CAA) to the pathogenesis of Alzheimer disease (AD) and dementia in general emphasizes the importance of developing novel targeting approaches for detecting and treating cerebrovascular amyloid (CVA) deposits. We developed a nanoparticle-based technology that uses a monoclonal antibody against fibrillar human amyloid-β42 that is surface coated onto a functionalized phospholipid monolayer. We demonstrate that this conjugated nanoparticle binds to CVA deposits in arterioles of AD transgenic mice (Tg2576) after infusion into the external carotid artery using 3 different approaches. The first 2 approaches use a blood vessel enrichment of homogenized brain and a leptomeningeal vessel preparation from thin tangential brain slices from the surface of the cerebral cortex. Targeting of CVA by the antibody-coated nanoparticle was visualized using fluorescent lissamine rhodamine-labeled phospholipids in the nanoparticles, which were compared with fluorescent staining of the endothelial cells and amyloid deposits using confocal laser scanning microscopy. The third approach used high-field strength magnetic resonance imaging of antibody-coated iron oxide nanoparticles after infusion into the external carotid artery. Dark foci of contrast enhancement in cortical arterioles were observed in T2*-weighted images of ex vivo AD mouse brains that correlated histologically with CVA deposits. The targeting ability of these nanoparticles to CVA provides opportunities for the prevention and treatment of CAA.

Visualization of Mouse Pancreas Architecture Using MR Microscopy

Pancreatic diseases, which include diabetes, pancreatitis, and pancreatic cancer, are often difficult to detect and/or stage, contributing to a reduced quality of life and lifespan for patients. Thus, there is need for a technology that can visualize tissue changes in the pancreas, improve understanding of disease progression, and facilitate earlier detection in the human population. Because of low spatial resolution, current clinical magnetic resonance imaging (MRI) at low field strength has yet to fully visualize the exocrine, endocrine, vascular, and stromal components of the pancreas. We used high field strength magnetic resonance microscopy (μMRI) to image mouse pancreas ex vivo without contrast agents at high spatial resolution. We analyzed the resulting high-resolution images using volume rendering to resolve components in the pancreas, including acini, islets, blood vessels, and extracellular matrix. Locations and dimensions of pancreatic components as seen in three-dimensional μMRI were compared with histological images, and good correspondence was found. Future longitudinal studies could expand on the use of in vivo μMRI in mouse models of pancreatic diseases. Capturing three-dimensional structural changes through μMRI could help to identify early cellular and tissue changes associated with pancreatic disease, serving as a mode of improved detection in the clinic for endocrine and exocrine pathologies.

Susceptibility weighted magnetic resonance imaging of cerebral cavernous malformations: prospects, drawbacks, and first experience at ultra–high field strength (7-Tesla) magnetic resonance imaging

High-resolution susceptibility weighted MR imaging at high field strength provides excellent depiction of venous structures, blood products, and iron deposits, making it a promising complementary imaging modality for cerebral cavernous malformations (CCMs). Although already introduced in 1997 and being constantly improved, susceptibility weighted imaging is not yet routine in clinical neuroimaging protocols for CCMs. In this article, the authors review the recent literature dealing with clinical and scientific susceptibility weighted imaging of CCMs to summarize its prospects and drawbacks and provide their first experience with its use in ultra-high field (7-T) MR imaging.

Can Images Obtained With High Field Strength Magnetic Resonance Imaging Reduce Contouring Variability of the Prostate?

The objective of this study is to determine whether there is less contouring variability of the prostate using higher-strength magnetic resonance images (MRI) compared with standard MRI and computed tomography (CT). Forty patients treated with prostate brachytherapy were accrued to a prospective study that included the acquisition of 1.5-T MR and CT images at specified time points. A subset of 10 patients had additional 3.0-T MR images acquired at the same time as their 1.5-T MR scans. Images from each of these patients were contoured by 5 radiation oncologists, with a random subset of patients repeated to quantify intraobserver contouring variability. To minimize bias in contouring the prostate, the image sets were placed in folders in a random order with all identifiers removed from the images. Although there was less interobserver contouring variability in the overall prostate volumes in 1.5-T MRI compared with 3.0-T MRI (p < 0.01), there was no significant differences in contouring variability in the different regions of the prostate between 1.5-T MRI and 3.0-T MRI. MRI demonstrated significantly less interobserver contouring variability in both 1.5-T and 3.0-T compared with CT in overall prostate volumes (p < 0.01, p = 0.01), with the greatest benefits being appreciated in the base of the prostate. Overall, there was less intraobserver contouring variability than interobserver contouring variability for all of the measurements analyzed. Use of 3.0-T MRI does not demonstrate a significant improvement in contouring variability compared with 1.5-T MRI, although both magnetic strengths demonstrated less contouring variability compared with CT.

The Role of Imaging in the Diagnosis of Central Nervous System Vasculitis

Cerebral vasculitis is diagnosed with difficulty. Its presentation with heterogeneous symptoms and signs often delays diagnosis. In this context, imaging plays an important role in advancing the diagnosis. Digital subtraction cerebral angiography, MRI, and MRA, the most useful examinations for vasculitis, provide supportive, but not pathognomonic, evidence of cerebral vasculitis. On MRI, multiple infarcts in different vascular territories and of different ages are suggestive of vasculitis. On digital subtraction cerebral angiography, areas of stenosis, dilatation, and occlusion are suggestive of vasculitis. Small vessel vasculitis is currently best demonstrated by changes seen in brain parenchyma on MRI, but high field strength (7 T) magnetic resonance angiography offers the possibility of directly evaluating small vessel vasculitis. Ultrasound and high-resolution contrast MRI are excellent modalities for evaluating the superficial extracranial circulation.

Human Hippocampal Subfields in Young Adults at 7.0 T: Feasibility of Imaging

To establish an imaging approach to visualize the 100-microm-thick hippocampal neuron-generating dentate granule cell layer (DGCL) consistently within a clinically feasible magnetic resonance (MR) imaging duration and to assess its sensitivity by quantifying the likelihood that it will be detected in healthy young adults. The study was HIPAA compliant and institutional review board approved. All subjects provided written informed consent. Ten healthy volunteers (five male subjects, five female subjects; mean age, 26 years +/- 6 [standard deviation]) were imaged at 7.0 T by using a 24-element head coil array with three-dimensional T1-weighted MR imaging for anatomic reference, followed by T2*-weighted gradient-echo (echo time, 25 msec; repetition time, 944 msec) imaging at 232-microm in-plane resolution (0.05-mm(3) pixels) in coronal and sagittal slabs (17 sections at 1 mm thick) over the hippocampus in 14 minutes. The entire study took 45 minutes. The DGCL was consistently visible in all 10 enrolled subjects. All larger subfields were visible in excellent detail and contrast in every subject. The spatial resolution and tissue contrast at high field strength (7.0 T) MR imaging can be used to consistently reveal hippocampal morphology down to 100-microm subfields within a clinically acceptable imaging duration. This imaging technique might be used to detect cellular disarray and degenerative changes in this sensitive circuit earlier than at 1.5 T or even 3.0 T. (c) RSNA, 2010.

Clinical application of high field strength magnetic resonance imaging

Clinical application of high field strength magnetic resonance imaging

High field strength magnetic resonance imaging of cardiovascular diseases

1059 J Korean Med Assoc 2010 December; 53(12): 1059-1064 c Korean Medical Association This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Focused Issue of This Month·고자장 자기공명영상의 임상적 응용 J Korean Med Assoc 2010 December; 53(12): 1059-1064 DOI: 10.5124/jkma.2010.53.12.1059 pISSN: 1975-8456 eISSN: 2093-5951 http://jkma.org

High field strength magnetic resonance imaging of brain lesion

The primary merit of a 3 tesla (T) magnetic resonance (MR) scanner is the increase in the signal-to-noise ratio (SNR). It can offer high spatial and temporal image resolution and its diagnostic potential for brain lesions can be improved at the magnetic strength of 3T. In addition to the increased SNR, strong prolongation of T1 relaxation time at high field MR leads to overall improvements in enhancing lesions versus non-enhancing tissue on contrast-enhanced T1-weighted images and blood versus tissue contrast on time-of-flight MR angiography. Increased chemical shift and susceptibility can improve the spectral resolution in MR spectroscopy and the sensitivities in the micro-hemorrhage detection of gradient echo image, the perfusion change of perfusion MRI, and the blood oxygen level-dependent effect of functional magnetic resonance imaging (MRI). The short acquisition time of diffusion MRI at 3T can decrease motion artifacts in irritable stroke patients and it can be easier to estimate anisotrophy and to increase the efficiency of tractography in diffusion tensor imaging with high numbers of gradient directions. On the other hand, the regulation of the specific absorption rate due to increased radio-frequency energy deposition and the controls for signal loss and increased artifacts at 3T are the main clinical problems. If the drawbacks can be addressed by parallel imaging or pulse sequence changes, 3T MRI can be a useful diagnostic tool and increase the diagnostic accuracy in various brain lesions, such as stroke, trauma, epilepsy, multiple sclerosis, dementia, and brain tumors.

High field strength magnetic resonance imaging of musculoskeletal diseases

Musculskeletal magnetic resonance imaging (MRI) applications are making the transition rapidly from 1.5 tesla (T) to 3T. The higher signal-to-noise ratio (SNR) that is available with a 3T MRI system allows for greater spatial resolution and provides the potential to improve the diagnostic capability of musculoskeletal MRI. With the use of 3T systems, one can enhance the SNR, spatial resolution, and contrast-to-noise ratio of intrinsic joint structures such as osseous, tendinous, cartilaginous, and ligamentous structures, which makes them more discernable and amenable to proper radiologic assessment. The SNR gain and coil technology advances allow for a smaller voxel-size and parallel imaging, reducing the acquisition time without significant signal loss. Three-dimensional (3D) fast spin echo sequences with isotropic resolution reduce partial volume artifacts through the acquisition of thin continuous sections and enable free 3D-multi-planar-reformatting without loss of image quality. This technique may be a promising method to replace currently used 2D sequences in clinical practice. In addition to current clinical applications, 3T MRI will contribute to the development of new molecular and functional MRI techniques.

High field strength magnetic resonance imaging of abdominal diseases

1065 J Korean Med Assoc 2010 December; 53(12): 1065-1073 c Korean Medical Association This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Focused Issue of This Month·고자장 자기공명영상의 임상적 응용 J Korean Med Assoc 2010 December; 53(12): 1065-1073 DOI: 10.5124/jkma.2010.53.12.1065 pISSN: 1975-8456 eISSN: 2093-5951 http://jkma.org

High field strength magnetic resonance imaging in children

J Korean Med Assoc 2010 December; 53(12): 1093-1102 c Korean Medical Association This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons. org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. J Korean Med Assoc 2010 December; 53(12): 1093-1102 DOI: 10.5124/jkma.2010.53.12.1093 pISSN: 1975-8456 eISSN: 2093-5951 http://jkma.org

Introduction to high field strength magnetic resonance imaging

Introduction to high field strength magnetic resonance imaging

Minimizing Ferromagnetic Artefact With Metallic Lumbar Total Disc Arthroplasty Devices at Adjacent Segments

Technical report. To minimize the gross artefact associated with a conventional metallic lumbar total disc arthroplasty (TDA) device on a conventional high field-strength (1.5 Tesla [T]) magnetic resonance imaging (MRI) scanner. Gross artefact is often apparent with ferromagnetic metallic TDA devices on conventional high field-strength MRI scanners. Such artefact completely obliterates MRI assessment at the operated level, and usually obscures visualization of adjacent segments. Because adjacent segment preservation is a raison d'être of spinal TDA, clarity of imaging at this latter level is imperative. A failure to image adjacent segments may presage investigations, which are either invasive (e.g., myelography) or associated with significant radiation hazard (e.g., computed tomography), both with significantly less diagnostic sensitivity. This could negatively direct TDA choice with certain TDAs. Progressive modifications to specific imaging parameter settings were sought on a conventional high field-strength (1.5T) closed-bore scanner to match the minimal artefact previously observed on a lower field-strength (0.3T) open scanner. Direct comparisons were made between each modified protocol image obtained initially using a phantom; however, routine postoperative MRIs were subsequently obtained in n = 40 patients following lumbar TDA insertion. Key parameter modifications were required in the receive bandwidth, the strength of the frequency encoding gradient, as well as in the echo train length. The use of higher specification "focused gradients" was also avoided. The overall effect was to reduce the slew rate of the gradients, which limited artefact due to a decrease in phase dispersion. Such appearances effectively matched with those previously obtained on the low field-strength (0.3T) open scanner in n = 40 patients. Relatively simple modifications to MRI parameter settings can be made on conventional high field-strength (1.5T) closed-bore scanners, which minimize metal artefact and enhance imaging of adjacent segments with ferromagnetic TDA devices. Such modifications effectively match appearances to those obtained with outmoded low field-strength (0.3T) open-bore scanners.