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Introduction The aim of this work was to assess the role of 3T-MR spectroscopy (MRS) in the multi-parametric MRI evaluation of breast lesions, using a pattern-recognition based classification method. Methods 291 patients (301 lesions, median 2.3 cm3) were enrolled in the study (age 18–85 y, mean 54.2 y). T1-TSE (TR/TE = 400/10 ms) and T2-STIR imaging (TR/TE = 5000/60 ms), dynamic-contrast-enhanced MRI (DCE-MRI), apparent diffusion coefficient (ADC) (b = 0–800 s/mm2), and single-voxel MRS (10 × 10 × 10 mm3, PRESS, TR/TE = 3000 ms/135 ms) were performed by means of a 3T scanner. MRS results were accepted if the FWHM of the water peak was ⩽45 Hz. Total choline (tCho) was considered detected if the signal-to-noise ratio (SNR) of the 3.2 ppm peak was ⩾2. A classifier-based analysis (support-vector-machines, SVM) was performed with 4-dimensional vectors including type of margin, DCE-MRI kinetic curve type, ADC mean value, and tCho SNR. A comparison with 3-dimensional vectors (without tCho SNR) was used to assess MRS impact on sensitivity, specificity, and positive-negative predictive values (PPV-NPV) for malignancy. Results 228 lesions (180 malignant/48 benign) showed acceptable spectral quality. Comparison of classification results with histopathological examination of surgical specimens showed sensitivity = 93.7%, specificity = 84.9%, PPV = 95.2%, NPV = 81.5% without the inclusion of MRS in the SVM analysis. When MRS was included, the figures increased to 95.1%, 90.7%, 97.2%, and 85.0%, respectively. Conclusions Inclusion of 3T-MRS in the multi-parametric MRI evaluation of breast lesions improved the performance of the SVM-based classifier, showing a possible role of high-field MR spectroscopy in the differential diagnosis between benign and malignant breast lesions. Further research is however needed to confirm this initial evidence.

Magnetic resonance imaging is attracting increasing attention from the uroradiological community as a modality to guide the management of prostate cancer. With the high incidence of prostate cancer it might come as a surprise that for a very long time (and in many places even at present) treatment decisions were being made without the use of detailed anatomical and functional imaging of the prostate gland at hand. Although T2 -weighted MRI can provide great anatomical detail, by itself it is not specific enough to discriminate cancer from benign disease, so other functional MRI techniques have been explored to aid in detection, localization, staging and risk assessment of prostate cancer. With the current evolution of clinical MR systems from 1.5 to 3 T it is important to understand the advantages and the challenges of the higher magnetic field strength for the different functional MR techniques most used in the prostate: T2 -weighted MRI, diffusion-weighted MRI, MR spectroscopic imaging and dynamic contrast-enhanced imaging. In addition to this, the use of the endorectal coil at different field strengths is discussed in this review, together with an outlook of the possibilities of ultra-high-field MR for the prostate. Copyright © 2013 John Wiley & Sons, Ltd.

In this paper we describe the development of superconducting magnets for high-field Magnetic Resonance Imaging (MRI) by various businesses and institutions in China. As the Chinese MR market rapidly expands, many foreign and domestic companies and research institutions are joining the race to meet the burgeoning demand by developing key MRI components for various magnetic field configurations. After providing a brief introduction to research on MRI superconducting magnets that dates back to the 1980s, the first large-bore 1.5 T superconducting magnet with 50-cm DSV for whole-body MRI – successfully developed and manufactured by AllTech Medical Systems in Chengdu, China—is presented and its specifications are described.

Diffusion tensor imaging (DTI) and perfusion-weighted imaging (PWI) are essential tools for diagnosing, differentiating, and monitoring brain tumors. High-field MRI provides higher signal-to-noise ratio, shorter scan time, and better image quality. One-stop multiparametric study, including DTI and PWI, is possible with high-field MRI in brain tumors. DTI can be used for assessing spatial relationship between major white matter tract and tumor, differentiating gliomas from nonglial tumors, and postoperative evaluation. PWI provides reliable biomarkers for glioma grading, therapeutic responses, and differential diagnosis of various brain tumors. With higher field strength, better-quality DTI and PWI can raise the diagnostic accuracy in brain tumors.

Background and Purpose. Pilot study to examine the use of T1-, T2-, and T2*-weighted images for evaluating hematoma size and extent of edema in mouse brain at high field.Methods. Following collagenase-induced intracerebral hemorrhage, nine mice were imaged at 4.7 T using T1-, T2-, and T2*-weighted images for hematoma and edema quantitation on days 1, 3, 10, and 21 after surgery. Values were compared with morphometric analysis of cryosections at the time of final MR imaging.Results. For hematoma quantitation, the Spearman correlation coefficient (r) between T1 signal change and histology was 0.70 (P<0.04) compared withr=0.61(P<0.09) for T2*. The extent of perihematomal edema formation on cryosections was well reflected on T2 withr=0.73(P<0.03).Conclusions. Within the limits of our pilot study, MR imaging on 4.7 T appears to approximate the temporal changes in hematoma and edema sizes in murine ICH well, thus laying the groundwork for longitudinal studies on hematoma resorption and edema formation.

The objective was to improve the temporal resolution in black-blood CINE tissue phase mapping sequences at high field MR systems. The temporal resolution is limited due to SAR constraints causing idle times into the sequence. The aim was to avoid these idle times and therefore providing an increased number of heart phases.Thirteen volunteers were enrolled in this study. Each volunteer underwent different myocardial short-axis scans comprising scans with application of both presaturation pulses, with alternating application of presaturation pulses and with an attenuation of the excitation angle. The last two approaches enable a SAR reduction or increased temporal resolution. The contrast to noise ratio (CNR) between myocardium and blood and the influence on the measured tissue motion were investigated.High CNR between myocardium and blood could be obtained with the application of alternating presaturation-pulses. Reduction of the flip angle of the presaturation-pulses provided reduced CNR relative to both the original and the alternated presaturation-pulses approach. More details of the myocardial motion were observed with increased temporal resolution.It is feasible to increase the temporal resolution at high field strength by reducing the SAR with either alternating presaturation-pulses or decreased flip angle of these pulses.

Purpose: To implement a dual-echo sequence MRI technique at 7T for simultaneous acquisition of time-of-flight (TOF) MR angiogram (MRA) and blood oxygenation level-dependent (BOLD) MR venogram (MRV) in a single MR acquisition and to compare the image qualities with those acquired at 3T. Materials and Methods: We implemented a dual-echo sequence with an echo-specific k-space reordering scheme to uncouple the scan parameter requirements for MRA and MRV at 7T. The MRA and MRV vascular contrast was enhanced by maximally separating the k-space center regions acquired for the MRA and MRV and by adjusting and applying scan parameters compatible between the MRA and MRV. The same imaging sequence was implemented at 3T. Four normal subjects were imaged at both 3T and 7T. MRA and MRV at 7T were reconstructed both with and without phase-mask filtering and were compared quantitatively and qualitatively with those at 3T with phase-mask filtering. Results: The depiction of small cortical arteries and veins on MRA and MRV at 7T was substantially better than that at 3T, due to about twice higher contrast-to-noise ratio (CNR) for both arteries (164 ±57 vs. 77 ± 26) and veins (72 ± 8 vs. 36 ± 6). Even without use of the phase-masking filtering, the venous contrast at 7T (65 ± 7) was higher than that with the filtering at 3T (36 ± 6). Conclusion: The dual-echo arteriovenography technique we implemented at 7T allows the improved visualization of small vessels in both the MRA and MRV because of the greatly increased signal-to-noise ratio (SNR) and susceptibility contrast, compared to 3T. J. Magn. Reson. Imaging 2010;31:255–261. © 2009 Wiley-Liss, Inc.

In vivo 1H MRS is rapidly developing as a clinical tool for diagnosing and characterizing breast cancers. Many in vivo and in vitro experiments have demonstrated that alterations in concentrations of choline-containing metabolites are associated with malignant transformation. In recent years, considerable efforts have been made to evaluate the role of 1H MRS measurements of total choline-containing compounds in the management of patients with breast cancer. Current technological developments, including the use of high-field MR scanners and quantitative spectroscopic analysis methods, promise to increase the sensitivity and accuracy of breast MRS. This article reviews the literature describing in vivo MRS in breast cancer, with an emphasis on the development of high-field MR scanning and quantitative methods. Potential applications of these technologies for diagnosing suspicious lesions and monitoring response to chemotherapy are discussed.

Morphological and biochemical magnetic resonance imaging (MRI) is due to high field MR systems, advanced coil technology, and sophisticated sequence protocols capable of visualizing articular cartilage in vivo with high resolution in clinical applicable scan time. Several conventional two-dimensional (2D) and three-dimensional (3D) approaches show changes in cartilage structure. Furthermore newer isotropic 3D sequences show great promise in improving cartilage imaging and additionally in diagnosing surrounding pathologies within the knee joint. Functional MR approaches are additionally able to provide a specific measure of the composition of cartilage. Cartilage physiology and ultra-structure can be determined, changes in cartilage macromolecules can be detected, and cartilage repair tissue can thus be assessed and potentially differentiated. In cartilage defects and following nonsurgical and surgical cartilage repair, morphological MRI provides the basis for diagnosis and follow-up evaluation, whereas biochemical MRI provides a deeper insight into the composition of cartilage and cartilage repair tissue. A combination of both, together with clinical evaluation, may represent a desirable multimodal approach in the future, also available in routine clinical use.

High field magnetic resonance imaging at 3.0 T is rapidly gaining clinical acceptance as the preferred platform for magnetic resonance (MR) imaging. This is spurred in part because advances in the manufacture of magnet technology have brought the cost of 3.0-T magnets into the range of previous 1.5-T machines, as well as ongoing research demonstrating numerous advantages of 3.0 T over 1.5 T in neurological imaging. Many factors are responsible for improved imaging at higher field strength, including increased signal-to-noise and contrast-to-noise ratios. The impact of 3.0-T imaging of the musculoskeletal system has been less dramatic because its optimization is more complicated in the musculoskeletal system than in the brain. Many issues must be considered beyond what might be expected from simply doubling the field strength, including hardware design, protocol modifications because of changes in tissue characteristics at higher fields, artifact reduction, and safety. This article addresses many of these concerns, focusing on techniques to optimize high field MR imaging of the musculoskeletal system.

In vivo proton magnetic resonance spectroscopy ( 1 H MRS) is rapidly becoming useful as a clinical tool for diagnosing and characterizing breast cancers. Alterations of the levels of choline-containing metabolites are associated with malignancy. High-field MR scanners at 1.5 T, 3 T, 4 T, and 7 T have been used to evaluate the role of 1 H MRS measurements of total choline-containing compounds in patients with breast cancer. This article will review clinical use of MRI/MRS in vivo. Newer developments in high field MR scanning and quantitative MRS may help breast imagers improve sensitivity and specificity in diagnosing and treating breast cancer.

To prospectively investigate metabolic changes in the normal-appearing white matter (NAWM) of patients presenting with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) and to correlate these changes to conventional MR imaging findings in terms of MR imaging criteria.Multisequence MR imaging of the brain and (1)H-MR spectroscopy of the parietal NAWM were performed in 31 patients presenting with CIS and in 20 controls using a 3. 0 T MR system. MR imaging criteria and International Panel criteria were assessed based on imaging, clinical and paraclinical results. Metabolite ratios and absolute concentrations of N-acetyl-aspartate (tNAA), myoinositol (Ins), choline (Cho), and total creatine (tCr) were determined. The metabolite concentrations were correlated with the fulfilled MR imaging criteria.In comparison to the control group, the CIS group showed significantly decreased mean tNAA concentrations (-8. 1%, p = 0. 012). Significant changes could not be detected regarding Ins, tCr and Cho. No significant correlations between absolute metabolite concentrations and MR imaging criteria were observed. Patients with and without a lesion dissemination in space showed no significant differences of their metabolite concentrations.As assessed by (1)H-MRS a significant axonal damage already occurs during the first demyelinating episode in patients with CIS. Conventional MR imaging in terms of diagnostic imaging criteria does not significantly reflect NAWM disease activity in terms of metabolic alterations detected by (1)H-MR spectroscopy.

Mit dem verstarkten Einzug von 3-Tesla-Hochfeld-MR-Scannern in die klinische Routine bekommt auch der Sicherheitsbegriff in der MR-Bildgebung eine neue Dimension. Der erste Teil der Arbeit behandelt die 3 wichtigsten Quellen fur physikalische Wechselwirkungen der Magnetresonanztomographie (statisches Magnetfeld, Gradienten- und HF-Felder). Es werden jeweils die Unterschiede zum bisherigen klinischen 1,5-Tesla-Standard, Auswirkungen auf den Menschen, Wechselwirkungen mit metallischen Objekten und relevante Sicherheitsstandards besprochen. Der zweite Teil beleuchtet das Thema MR-Sicherheit aus Sicht der klinischen Praxis und versucht, Optimierungspotenziale aufzuzeigen. Von Bedeutung sind hier strukturelle Optimierungen im Bereich der Informationsdistribution und Klinikorganisation sowie Prufungsstandards und Kennzeichnungsrichtlinien.

Discrepancies exist in the literature regarding contrast between gray and white matter on spin-echo (SE) T1-weighted MR imaging at 3 T. The present study quantitatively assessed differences in gray matter-white matter contrast on both single- and multi-slice SE T1-weighted imaging between 3 and 1.5 T. SE T1-weighted sequences with the same parameters at both 3 and 1.5 T were used. Contrast-to-noise ratio (CNR) between gray and white matter (CNR(GM-WM)) was evaluated for both frontal lobes. To assess the effects of interslice gap, multi-slice images were obtained with both 0 and 25% interslice gap. Single-slice CNR(GM-WM) was higher at 3 T (17.66 +/- 2.68) than at 1.5 T (13.09 +/- 2.35; P0.001). No significant difference in CNR(GM-WM) of multi-slice images with 0% gap was noted between 3 and 1.5 T (3T, 8.61 +/- 2.55; 1.5T, 7.43 +/- 1.20; P0.05). Multi-slice CNR(GM-WM) with 25% gap was higher at 3T (12.47 +/- 3.31) than at 1.5 T (9.73 +/- 1.37; P0.001). CNR(GM-WM) reduction rate of multi-slice images with 0% gap compared with single-slice images was higher at 3T (0.47 +/- 0.13) than at 1.5 T (0.38 +/- 0.09; P = 0.02). CNR(GM-WM) on single-slice SE T1-weighted imaging and CNR(GM-WM) on multi-slice images with 25% interslice gap were better at 3 T than at 1.5 T. The influence of multi-slice imaging on CNR(GM-WM) was significantly larger at 3T than at 1.5 T.

This work introduces a robust framework for predicting Deep Brain Stimulation (DBS) target structures which are not identifiable on standard clinical MRI. While recent high-field MR imaging allows clear visualization of DBS target structures, such high-fields are not clinically available, and therefore DBS targeting needs to be performed on the standard clinical low contrast data. We first learn via regression models the shape relationships between DBS targets and their potential predictors from high-field (7 Tesla) MR training sets. A bagging procedure is utilized in the regression model, reducing the variability of learned dependencies. Then, given manually or automatically detected predictors on the clinical patient data, the target structure is predicted using the learned high quality information. Moreover, we derive a robust way to properly weight different training subsets, yielding higher accuracy when using an ensemble of predictions. The subthalamic nucleus (STN), the most common DBS target for Parkinson’s disease, is used to exemplify within our framework. Experimental validation from Parkinson’s patients shows that the proposed approach enables reliable prediction of the STN from the clinical 1.5T MR data.

To evaluate the signal characteristics of different iliac artery stents in MR angiography (MRA) at 3 T in comparison with 1.5 T.Sixteen iliac artery stents were implanted in plastic tubes filled with a solution of Gd-DTPA and imaged at 3 T and 1.5 T using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis included a subjective assessment of artifact characteristics, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements in stented and unstented vessel parts, and quantitative measurements of total artifact size.The pattern of stent artifacts inside the stents evidently did not differ at 3 T and 1.5 T. The average total size of the artifact areas surrounding the stents was significantly larger at 3 T (P0.03). However, within the stented part of the vessel phantom, the signal of the lumen and its contrast to modeled surrounding tissue was significantly higher at the higher field. The mean SNR of the lumen increased from 95.5 at 1.5 T to 127.3 at 3 T, and the CNR of the vessel increased from 70.3 to 93.Assessment of the stent lumen in iliac artery stents in a phantom model is not compromised by imaging at 3 T compared to 1.5 T. The signal gain inside the stented part of the vessel lumen at higher field compensates for the higher degree of stent artifacts seen in stents made of steel or cobalt.

Updating of neuronavigation systems with intraoperative image data is possible without repeated patient registration. Tumor remnants depicted by intraoperative imaging can be localized reliably, as well as brain shift can be compensated for.

Diffusion-weighted magnetic resonance spectroscopy of brain metabolites offers unique access to compartment-specific microstructural information on neural tissue. Here, we investigated in detail the diffusion characteristics of the neuronal/axonal markers N-acetylaspartate + N-acetyl aspartyl glutamate (tNAA) in a small region of the human corpus callosum at 7 T. The diffusion-weighted spectroscopy data were analyzed by fitting to a model in which information about cross-callosal tract orientation within the spectroscopy volume, obtained from diffusion tensor imaging data, was incorporated. We estimated the microscopic misalignment of axons (σ φ = 18.6° ± 3.0°) in excellent agreement with independent histological results (σ φ = 18.1° ± 4.6°) obtained from microscopic analysis of axonal orientations in the body of the corpus callosum from post-mortem human brain slices. We also robustly quantified the diffusion coefficient of tNAA (0.51 ± 0.06 × 10−3 mm2/s) in axonal cytoplasm, unbiased by the tract curvature. This work supports the notion that microscopic axonal misalignment is a dominant microstructural property in white matter tracts and has a strong impact on the evaluation of tissue microstructure using diffusion information, and should therefore be taken into consideration in the evaluation of white matter microstructure. Additionally, this study enabled robust and unbiased assessment of the cytosolic diffusion coefficient of tNAA, a potential biomarker for axonopathy and neuronal degeneration.

Background Comprehensive assessment of pediatric congenital heart disease (CHD) at any field strength mandates evaluation of both vascular and dynamic cardiac anatomy for which diagnostic quality contrast-enhanced magnetic resonance angiography (CEMRA) and cardiac cine are crucial. Objective To determine whether high-resolution (HR) CEMRA and steady-state free precession (SSFP) cine can be performed reliably at 3.0 T in children with CHD and to compare the image quality to similar techniques performed at 1.5 T. Materials and methods Twenty-eight patients with a median age of 5 months and average weight 9.0 ± 7.8 kg with suspected or known CHD were evaluated at 3.0 T. SSFP cine (n = 86 series) and HR-CEMRA (n = 414 named vascular segments) were performed and images were scored for image quality and artifacts. The findings were compared to those of 28 patients with CHD of similar weight who were evaluated at 1.5 T. Results Overall image quality on HR-CEMRA was rated as excellent or good in 96% (397/414) of vascular segments at 3.0 T (k = 0.49) and in 94% (349/371) of vascular segments at 1.5 T (k = 0.36). Overall image quality of SSFP was rated excellent or good in 91% (78/86) of cine series at 3.0 T (k = 0.55) and in 81% (87/108) at 1.5 T (k = 0.47). Off-resonance artifact was common at both field strengths, varied over the cardiac cycle and was more prevalent at 3.0 T. At 3.0 T, off-resonance dark band artifact on SSFP cine was absent in 3% (3/86), mild in 69% (59/86), moderate in 27% (23/86) and severe in 1% (1/86) of images; at 1.5 T, dark band artifact was absent in 16% (17/108), mild in 69% (75/108), moderate in 12% (13/108) and severe in 3% (3/108) of cine images. The signal-to-noise ratio and contrast-to-noise ratio of both SSFP cine and HR-CEMRA images were significantly higher at 3.0 T than at 1.5 T (P < 0.001). Conclusion Signal-to-noise ratio and contrast-to-noise ratio of high-resolution contrast-enhanced magnetic resonance angiography and SSFP cine were higher at 3.0 T than at 1.5 T. Artifacts on SSFP cine were cardiac phase specific and more prevalent at 3.0 T such that frequency-tuning was required in one-third of exams. In neonates, high spatial resolution CEMRA was highly reliable in defining extracardiac vascular anatomy. © 2014 The Author(s).

Background: Thin cerebral aneurysm wall thickness (AWT) is connected to high aneurysm rupture risk. MR imaging of AWT leads to overestimations. The aim of the present study was to quantify MR inaccuracy by comparison with accurate light microscopic measurements.

This paper describes an investigation of MR-active vena cava filter (VCF) implants. The active part of the VCF is a resonating circuit, which is tuned to the Lamor frequency of the MR scanner. The experiments were performed on a low field MRI system. The susceptibility artifact behaviour of different commercially available VCFs and their materials was investigated. Three MR-active VCF prototypes were built based on these results and evaluated. No lead connection between the resonating circuit of the implant and the MR system is necessary for reception of the MR signal. Localisation of the prototypes within the MR image was possible by their signal enhancement. The results provide a basis for further developments and investigations of MR-active VCF implants for high field MR scanners.

Stereotactic guided laser-induced interstitial thermotherapy (SLITT) represents a minimal invasive method to produce necrosis in cerebral tumor tissue by local heating. The dose/response relationship relies on experimental studies and few clinical data performed in high field MR systems. A better understanding of the energy-dose/tissue response in human brain tumors is important to optimize this treatment modality. Twenty-four patients with gliomas were treated with SLITT, with a total of 30 laser procedures performed. Under local anesthesia 600 microns laser-fibers were inserted by stereotactic-guided technique into the center of the tumor. In a low field open MR system (0.2 T) the denaturation of the tumor using a neodymium YAG laser (1064 nm) was monitored by 3D-turbo FLASH T1-weighted sequences. Laser energy was applied in steps of 400 to 1200 Joules. Development of necrosis at a mean total energy dose of 2979 Joules could be monitored in all procedures. Two different thermal lesion architectures were observed. First signal changes were monitored after a mean of 1108 Joules and 1393 Joules, respectively. Mean max. total lesion size was 21.2 mm. The higher the total energy the larger was the thermolesion, but no linear relationship could be seen. Tumor tissue response showed no dependency on tumor grading. Monitoring of stereotactic guided laser-induced thermolesions in the low-power MR OPEN is feasible and safe. Although lesion size basically is energy dependent, it should be applied individually, since the thermal response in brain tumors varies due to different optical properties, even in the same tumor gradings.

Recently, the introduction of the 3 Tesla (3T) magnetic resonance (MR) imaging system for more sophisticated clinical applications has yielded important benefits, especially in the field of neuroradiology. The greatest advantage ofthe high-field MR system is a higher signal-to-noise ratio, and higher spatial resolution with improved anatomical information. Diffusionweighted imaging (DWI) benefits from the higher signal-to-noise ratio and offers useful information for various brain disorders. Magnetic susceptibility provides an important contrast for MRI. Susceptibility-weighted MR imaging (SWI) is a new technique, which has been used increasingly to investigate brain tissue microstructure and to detect abnormal levels of brain iron (Haacke EM et Al, Thomas B et Al). The enhanced and increased potential of these MR techniques (DWI, DTI, MRS, SWI, fMRI) on high-field MR units has increased sensitivity not only to subtle white matter (WM), but also to gray matter (GM) changes.

Background DCE@urLAB is a software application for analysis of dynamic contrast-enhanced magnetic resonance imaging data (DCE-MRI). The tool incorporates a friendly graphical user interface (GUI) to interactively select and analyze a region of interest (ROI) within the image set, taking into account the tissue concentration of the contrast agent (CA) and its effect on pixel intensity. Results Pixel-wise model-based quantitative parameters are estimated by fitting DCE-MRI data to several pharmacokinetic models using the Levenberg-Marquardt algorithm (LMA). DCE@urLAB also includes the semi-quantitative parametric and heuristic analysis approaches commonly used in practice. This software application has been programmed in the Interactive Data Language (IDL) and tested both with publicly available simulated data and preclinical studies from tumor-bearing mouse brains. Conclusions A user-friendly solution for applying pharmacokinetic and non-quantitative analysis DCE-MRI in preclinical studies has been implemented and tested. The proposed tool has been specially designed for easy selection of multi-pixel ROIs. A public release of DCE@urLAB, together with the open source code and sample datasets, is available at http://www.die.upm.es/im/archives/DCEurLAB/ webcite.

Purpose Currently, a multi-contrast protocol, including a combination of five MR-sequences is used as reference standard for morphologic imaging and quantitative measurements of the carotid artery vessel wall. The purpose of this study is to investigate the scan–rescan reproducibility together with intra- and inter-observer reproducibility of each of the five MR-sequences. Methods Twenty healthy volunteers (55% male, mean age = 26 years) underwent repeated MR-examinations (3T-Philips-MRI) of the left carotid artery vessel wall with five sequences; T1-TFE, T2-TSE, PD-TSE, T1-TSE and 3D TOF. A standard phased-array coil with two flexible elements of 14 cm × 17 cm was used to obtain nine transverse imaging sections of the left carotid artery with identical in-plane resolution (0.46 mm × 0.46 mm). Reproducibility analysis was performed in 3 slices of the common carotid artery for all sequences. Results For, scan–rescan reproducibility, intra class correlation coefficients (ICC) were excellent for all sequences and ranged from 0.79 to 0.95. The intra-observer ICC ranged from 0.89 to 0.98 and the inter-observer ICC ranged from 0.84 to 0.96, for both lumen and vessel wall assessment. Conclusions By high field MR imaging, vessel wall and lumen area of the carotid artery can be assessed with excellent scan–rescan, intra- and inter-observer reproducibility for all five sequences.

Although much has been published highlighting the safety risks of magnetic resonance imaging, little mention has been made of acoustic noise levels. As the clinically available gradient strengths of MR systems increase, acoustic noise levels will become more important. Measurements were made of the acoustic noise levels generated by magnetic resonance imaging on two high field systems (1.0 T and 1.5 T). These data were compared with those in the literature. On the 1.0 T magnetic resonance system, comparisons were also made between data acquired using the standard gradient system (maximum levels of 10 m T/m) and a new upgraded gradient system (maximum levels of 15 m T/m). The results show that many sequences produce noise levels above the safe levels defined by the Department of Health and the Health and Safety Executive. Providing routine ear protection for patients is, therefore, important. Noise levels for the upgraded gradient system on the 1.0 T scanner are in the range of 2 dB greater. As expected, noise levels generated were greater for the 1.5 T magnetic resonance imager than on the 1.0 T system.

A prospective study was undertaken to compare MR imaging of the knee obtained with low-field and high-field systems. In 10 subjects, MR imaging of the knee was performed on a 0.2 T permanent magnet and on a 1.5 T superconductive system. Similar spin echo (SE) and 3D-FISP (3D Fourier transform with steady state precession) acquisitions were obtained. Comparative image analysis was performed independently by four radiologists. Results show that the image quality and diagnostic performance delivered by state-of-the-art 0.2 T and 1.5 T systems is equivalent. Advantages of the 1.5 T system included: better signal-to-noise ratio, shorter scan times, better visualization of asymptomatic grade 1 meniscal degeneration on SE images. Advantages of 0.2 T images were: decreased chemical shift, susceptibility and flow artifacts, improved evaluation of subchondral bone on 3D-FISP images, slightly better patient tolerance. We conclude that, for MR imaging of the knee, a low-field system is a cost-effective alternative to more expensive superconducting units.