Field Magnetic Resonance Imaging Research Articles

Ligand‐Mediated Magnetism‐Conversion Nanoprobes for Activatable Ultra‐High Field Magnetic Resonance Imaging

AbstractUltra‐high field (UHF) magnetic resonance imaging (MRI) has emerged as a focal point of interest in the field of cancer diagnosis. Despite the ability of current paramagnetic or superparamagnetic smart MRI contrast agents to selectively enhance tumor signals in low‐field MRI, their effectiveness at UHF remains inadequate due to inherent magnetism. Here, we report a ligand‐mediated magnetism‐conversion nanoprobe (MCNP) composed of 3‐mercaptopropionic acid ligand‐coated silver‐gadolinium bimetallic nanoparticles. The MCNP exhibits a pH‐dependent magnetism conversion from ferromagnetism to diamagnetism, facilitating tunable nanomagnetism for pH‐activatable UHF MRI. Under neutral pH, the thiolate (−S−) ligands lead to short τ′m and increased magnetization of the MCNPs. Conversely, in the acidic tumor microenvironment, the thiolate ligands are protonated and transform into thiol (−SH) ligands, resulting in prolonged τ′m and decreased magnetization of the MCNP, thereby enhancing longitudinal relaxivity (r1) values at UHF MRI. Notably, under a 9 T MRI field, the pH‐sensitive changes in Ag−S binding affinity of the MCNP lead to a remarkable (>10‐fold) r1 increase in an acidic medium (pH 5.0). In vivo studies demonstrate the capability of MCNPs to amplify MRI signal of hepatic tumors, suggesting their potential as a next‐generation UHF‐tailored smart MRI contrast agent.

7T MRI Versus 3T MRI of the Brain in Professional Fighters and Patients With Head Trauma.

Many studies have investigated the imaging sequelae of repetitive head trauma with mixed results, particularly with regard to the detection of intracranial white matter changes (WMCs) and cerebral microhemorrhages (CMHs) on ≤3 Tesla (T) field magnetic resonance imaging (MRI). 7T MRI, which has recently been approved for clinical use, is more sensitive at detecting lesions associated with multiple neurological diagnoses. In this study, we sought to determine whether 7T MRI would detect more WMCs and CMHs than 3T MRI in 19 professional fighters, 16 patients with single TBI, versus 82 normal healthy controls (NHCs). Fighters and patients with TBI underwent both 3T and 7T MRI; NHCs underwent either 3T (n = 61) or 7T (n = 21) MRI. Readers agreed on the presence/absence of WMCs in 88% (84 of 95) of 3T MRI studies (Cohen's kappa, 0.76) and in 93% (51 of 55) of 7T MRI studies (Cohen's kappa, 0.79). Readers agreed on the presence/absence of CMHs in 96% (91 of 95) of 3T MRI studies (Cohen's kappa, 0.76) and in 96% (54 of 56) of 7T MRI studies (Cohen's kappa, 0.88). The number of WMCs detected was greater in fighters and patients with TBI than NHCs at both 3T and 7T. Moreover, the number of WMCs was greater at 7T than at 3T for fighters, patients with TBI, and NHCs. There was no difference in the number of CMHs detected with 7T MRI versus 3T MRI or in the number of CMHs observed in fighters/patients with TBI versus NHCs. These initial findings suggest that fighters and patients with TBI may have more WMCs than NHCs and that the improved voxel size and signal-to-noise ratio at 7T may help to detect these changes. As 7T MRI becomes more prevalent clinically, larger patient populations should be studied to determine the cause of these WMCs.

Oregano Essential Oil-Pectin Edible Films on Shelf-Life Extension of Large Yellow Croaker (Pseudosciaena crocea) Fillet during Iced Storage

ABSTRACT The aim of this research was to determine the effects of pectin (P) combined with oregano essential oil (OEO) on the shelf-life extension of large yellow croaker (Pseudosciaena crocea) during storage at 4±1°C. Microbiological, physicochemical indexes, which also combined with low field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI), were periodically assessed during 21-day storage. The results showed that pectin combined with OEO added to can effectively inhibit the increase of microorganisms in fish, slow down the speed of lipid oxidation and delayed the rise of pH and TVB-N. Besides this, pectin coating with OEO has the positive effect on the increase of K value. Compared with CK group, 2.5% pectin + 0.6% oregano essential oil treatment could prolong the shelf-life of Pseudosciaena crocea for another 6 days. The combinations of pectin and OEO show promise as a natural preservative in aquatic products.

A Comparison of the Distortion in the Same Field MRI and MR-Linac System With a 3D Printed Phantom.

PurposeA 3D printed geometric phantom was developed that can be scanned with computed tomography (CT) and magnetic resonance imaging (MRI) to measure the geometric distortion and determine the relevant dose changes.Materials and MethodsA self-designed 3D printed photosensitive resin phantom was used, which adopts grid-like structures and has 822 1 cm2 squares. The scanning plan was delivered by three MRI scanners: the Elekta Unity MR-Linac 1.5T, GE Signa HDe 1.5T, and GE Discovery-sim 750 3.0T. The geometric distortion comparison was concentrated on two 1.5T MRI systems, whereas the 3.0T MRI was used as a supplemental experiment. The most central transverse images in each dataset were selected to demonstrate the plane distortion. Some mark points were selected to analyze the distortion in the 3D direction based on the plane geometric distortion. A treatment plan was created with the off-line Monaco system.ResultsThe distortion increases gradually from the center to the outside. The distortion range is 0.79 ± 0.40 mm for the Unity, 1.31 ± 0.56 mm for the GE Signa HDe, and 2.82 ± 1.48 mm for the GE Discovery-sim 750. Additionally, the geometric distortion slightly affects the actual planning dose of the radiotherapy.ConclusionGeometric distortion increases gradually from the center to the outside. The distortion values of the Unity were smaller than those of the GE Signa HDe, and the Unity has the smallest geometric distortion. Finally, the Unity’s dose variation best matched with the standard treatment plan.

Identification of Brain Damage after Seizures Using an MR-Based Electrical Conductivity Imaging Method.

Previous imaging studies have shown the morphological malformation and the alterations of ionic mobility, water contents, electrical properties, or metabolites in seizure brains. Magnetic resonance electrical properties tomography (MREPT) is a recently developed technique for the measurement of electrical tissue properties with a high frequency that provides cellular information regardless of the cell membrane. In this study, we examined the possibility of MREPT as an applicable technique to detect seizure-induced functional changes in the brain of rats. Ultra-high field (9.4 T) magnetic resonance imaging (MRI) was performed, 2 h, 2 days, and 1 week after the injection of N-methyl-D-aspartate (NMDA; 75 mg/kg). The conductivity images were reconstructed from B1 phase images using a magnetic resonance conductivity imaging (MRCI) toolbox. The high-frequency conductivity was significantly decreased in the hippocampus among various brain regions of NMDA-treated rats. Nissl staining showed shrunken cell bodies and condensed cytoplasm potently at 2 h after NMDA treatment, and neuronal cell loss at all time points in the hippocampus. These results suggest that the reduced electrical conductivity may be associated with seizure-induced neuronal loss in the hippocampus. Magnetic resonance (MR)-based electrical conductivity imaging may be an applicable technique to non-invasively identify brain damage after a seizure.

Quantitative sodium imaging using ultra‐high field magnetic resonance imaging in patients with Alzheimer's disease

AbstractBackgroundIn Alzheimer’s disease (AD), energy deficit is suspected to occur before clinical symptoms arise. Therefore, neuroimaging methods sensitive to metabolic alterations are attractive to improve diagnostics, therapeutics and follow‐ups of AD patients. An indirect measure of deficient Na+/K+‐ATPase‐activity during neurodegeneration is provided by the tissue sodium concentration (TSC) measured by Sodium‐(23Na)‐MRI.Method16 patients (7 Male, 71.7±8 years) diagnosed with AD (MoCA 15.1±7) were recruited from Ste. Anne Hospital in Paris as well as 16 cognitively healthy age‐matched control subjects (7 Male, 69±3.1 years; MoCA 28.1±1.8). Each subject underwent 23Na and 1H MRI examinations at the 7T MRI scanner (Siemens) at Neurospin, CEA. A dual‐resonance 1H/23Na volume coil (Rapid Biomedical) was used for a 23Na MRI protocol acquiring ultra‐short echo‐time images (3mm isotropic resolution) at two flip‐angles (a1=25º/a2=55º) (Coste et al., 2019). Briefly, processing steps comprised image reconstruction, denoising, motion‐ and B1‐inhomogeneities‐corrections, and a calibration step using 4 external references. Individual TSC maps were co‐registered to their T1‐weighted anatomical reference (MP2RAGE, 750 µm isotropic resolution) and a partial‐volume‐effect correction (Thomas et al., 2016) was implemented to limit the influence of sodium from cerebrospinal fluid. Anatomical and TSC images were normalized to the OASIS template using ANTs. A parameter free permutation analysis was performed voxel‐wise on normalized TSC images and on the LogJacobian of the deformation fields. After, region‐of‐interest‐analyses on hippocampus from VolBrain‐Atlas followed.ResultThe voxel‐based analysis showed significant widespread increases in TSC of AD patients, particularly in parietal, temporal and frontal regions. Interestingly, the observed TSC changes were located in areas not directly associated to significant structural changes (Fig 1). Furthermore, TSC in the hippocampus was found significantly higher in AD than in controls (42.9±4.3mmol/l; 35.8±3.9mmol/l; Wilcoxon‐rank‐sum; p=0.00015, z=3.8) and was correlated, after controlling for age, with both the MoCA‐scores (r=‐0.62; p=0.0002) and hippocampal volumes (r=‐0.39; p=0.032).ConclusionHigh‐field quantitative 23Na MRI in AD shows increased TSC values across a wide range of brain regions. These results may provide a deeper insight into metabolic alterations occurring during neurodegeneration. 23Na MRI could therefore serve as a useful tool to characterize disease progression or the impact of therapeutic intervention.

Noradrenergic contributions to cognitive decline and treatment potential in progressive supranuclear palsy and Parkinson’s disease

AbstractBackgroundThe Locus coeruleus is the principal source of Noradrenaline to the cerebrum, modulating diverse functions from attentional and behavioural control, learning and perception, arousal and autonomic control. The locus coeruleus is vulnerable to many neurodegenerative disorders, with post‐mortem evidence of early and substantial cell loss in Alzheimer’s disease, Parkinson’s disease (PD) and Progressive Supranuclear Palsy (PSP). The relevance of locus coeruleus pathology and noradrenergic denervation in vivo has come largely from psychopharmacological studies, and PET imaging of the noradrenergic transporter.MethodWe exploited advances in ultra‐high field magnetic resonance imaging at 7T that now provide excellent sensitivity to the loss of neuromelanin containing neurons in the locus coeruleus, enabling quantification of the spatial extent and signal intensity (cf. cell density) in patients. We developed an optimised atlas of locus coeruleus in older adults (>50), and applied this to independent cohorts of patients with idiopathic Parkinson’s disease and PSP (Richardson’s syndrome) with a magnetisation transfer weighted sequence to scan the brain stem at 7T.ResultPatients in both groups showed a marked reduction in locus coeruleus signal intensity, relative to a mid‐pontine reference regions, especially in the caudal locus coeruleus. In Parkinson’s disease, the contrast‐to‐noise of the locus coeruleus correlated with apathy and motor disease severity. A corresponding reduction of noradrenergic cells was confirmed at post‐mortem in a parallel group of patients with PSP, in whom cell loss was proportional to disease severity.Conclusion7T MRI is well tolerated and sensitive to pathology of the locus coeruleus in PSP and PD. We propose the use of 7T‐MRI to quantify the integrity of the locus coeruleus in stratified trials of therapeutic strategies for cognitive and motor control in neurodegenerative disease.

Clinical performance of contrast-enhanced spectral mammography in pre-surgical evaluation of breast malignant lesions in dense breasts: a single center study

PurposeTo compare the efficacy of contrast-enhanced spectral mammography, with ultrasound, full field digital mammography and magnetic resonance imaging in detection and size estimation of histologically proven breast tumors.MethodsThis open-label, single center, prospective study, included 160 dense breast women with at least one suspicious mammary lesion evaluated by ultrasound, full field digital mammography and magnetic resonance imaging in whom a mammary tumor was histologically proven after surgery performed at the European Institute of Oncology between January 2013 and December 2015. Following the complete diagnostic procedure, the patients were further investigated by contrast-enhanced spectral mammography prior to surgery.ResultsOverall, the detection rate of malignant breast lesions (in situ and invasive) was 93.8% (165/176) for contrast-enhanced spectral mammography, 94.4% (168/178) for ultrasound, 85.5 (147/172) for full field digital mammography and 97.7% (173/177) for magnetic resonance imaging. Radiological measurements were concordant with the post-surgical pathological measurements of the invasive tumor (i.e., within 5 mm) in: 64.6% for contrast-enhanced spectral mammography, 62.0% for ultrasound, 45.2% for full field digital mammography (p < 0.0001) and 69.9% for magnetic resonance imaging (p = 0.28); underestimated in: 17.4% for contrast-enhanced spectral mammography, 19.6% for ultrasound, 24.2% for full field digital mammography (p = 0.03) and 6.7% for magnetic resonance imaging (p = 0.0005); and overestimated in: 16.2% for contrast-enhanced spectral mammography, 16.6% for ultrasound, 16.6% for full field digital mammography and 22.7% for magnetic resonance imaging (p = 0.02).ConclusionsOur data suggest that contrast-enhanced spectral mammography improves on full field digital mammography and is comparable to ultrasound and magnetic resonance imaging in terms of detection sensitivity and size estimation of malignant lesions in dense breasts.

A Comparative Assessment Between High-resolution Ultrasonography and Field Magnetic Resonance Imaging in Supraspinatus Tear Cases and Its Arthroscopic Correlation.

BackgroundDiagnosis of a supraspinatus tear in patients presenting with shoulder pain is a difficult task and often requires the help of an MRI. However, in recent years, high-resolution ultrasonography (USG) has been utilized as a cheaper yet sensitive alternative. The aim of the study is to provide a comparative assessment of supraspinatus tears between USG and MRI in relation to arthroscopic results.MethodsA total of 60 patients with shoulder pain for the last three months or more scheduled to undergo arthroscopic surgery for their shoulder disorder were enrolled; those having any congenital deformity of the shoulder or having any contradiction to an MRI were excluded from the assessment. All the patients underwent high-resolution ultrasonography (HRUSG) and MRI evaluation. Both the USG and MRI findings were correlated with the arthroscopic findings.ResultsOn ultrasonography, 34 (56.67%) full-thickness tears and 22 (36.67%) partial-thickness tears of the supraspinatus were detected. On MRI, 36 (60.0%) were diagnosed as a full-thickness tear and 20 (33.33%) as a partial-thickness tear. After arthroscopy, 36 (60.00%) were confirmed as a full-thickness tear and 20 (33.33%) as a partial-thickness tear of the supraspinatus. For a full-thickness tear, the sensitivity and specificity of USG and MRI were 95.0% and 92.5%, and 85% and 92.5%, respectively. For a full-thickness tear, the sensitivity and specificity of the modalities were 94.4% and 100%, respectively.ConclusionHRUSG and MRI both had high comparable accuracy for detection of a supraspinatus tear, however, HRUSG had an edge over MRI in the detection of a partial tear.

Comparison of 12 Quadrature Birdcage Coils with Different Leg Shapes at 9.4 T

The purpose of this study was to analyse the relationship between the radio frequency (RF) coil performance and conductor surface shape for ultra-high field (UHF) magnetic resonance imaging. Twelve different leg-shaped quadrature birdcage coils were modeled and built, e.g., 4 mm-width-leg conventional birdcage coil, 7 mm-width-leg conventional birdcage, 10 mm-width-leg conventional birdcage coil, 13 mm-width-leg conventional birdcage coil, inside arc-shape-leg birdcage coil, outward arc-shape-leg birdcage coil, inside right angle-shape-leg birdcage coil, outward right angle-shape-leg birdcage coil, vertical 4 mm-width-leg vertical birdcage, 6 mm-width-leg vertical birdcage, 8 mm-width-leg vertical birdcage and 10 mm-width-leg vertical birdcage. Studies were carried out in both electromagnetic simulations with finite element method as well as in vitro saline phantom experiments at 9.4 T. Both the results of simulation and experiment showed that conventional birdcage coil produces the highest signal-to-noise ratio (SNR) while the vertical birdcage coil produces the most homogeneous RF magnetic (B 1) field at UHF. For conventional birdcage coils, as well as the vertical birdcage coils, only the proper width of legs results in the best performance (e.g., B 1 homogeneous and SNR). For vertical birdcage coils, the wider the leg size, the higher RF magnetic (B 1) field intensity distribution.

Contrast-Enhanced Magnetic Resonance Imaging at Earth’s Magnetic Field Using Trace Gd3+ and Ho3+ Salts

Here, we report a study of contrast-enhanced magnetic resonance imaging at Earth’s field. In this study, we performed magnetic relaxation measurements of protons in water in the presence of the lanthanide ions Gd3+ and Ho3+ using the nuclear magnetic resonance technique. The results suggest that Gd3+ is a more effective T1 and T2 relaxation agent than Ho3+ and is therefore a better contrast agent. We then confirmed the relaxation phenomenon by performing a T1-weighted-contrast magnetic resonance imaging (MRI) of samples containing water doped with Gd3+ at the Earth’s magnetic field. The T1-weighted imaging experimental result indicates that the intensity is the highest for the sample doped with the highest concentration of Gd3+ and lowest for the undoped sample. This work shows the feasibility of performing contrast-enhanced MRI in Earth’s magnetic field using relaxation agents such as lanthanide ions. In addition, this work also demonstrates that, although the Earth’s field MRI does not provide the strength and capability of a clinical MRI, it is still useful as a powerful demonstration tool, especially considering its low operating costs and portability.

Ultrasound and magnetic resonance imaging correlation of the wrist and metacarpophalangeal joints in fifty consecutive patients of rheumatoid arthritis

Background: Gray-scale ultrasound and Power Doppler ultrasound (GSUS, PDUS) and contrast Magnetic Resonance Imaging (MRI) are the imaging modalities to detect the disease in this early stage of rheumatoid arthritis (RA). This study was conducted to observe the advantages and disadvantages of USG and MRI of wrist and metacarpophalangeal joints in patients with rheumatoid arthritis. Methods: Clinically diagnosed cases of RA were included. GSUS-PDUS and high field (1.5T) MRI with contrast were used by two assessors. The evaluation and scoring was done using the RAMRIS score. Other assessed parameters included Joint space narrowing, GSUS bone erosions, Gray scale USG synovial hypertrophy, MRI tenosynovitis and tenosynovitis on GSUS. Results: Total 50 patients (44 female, 6 male; age 18-76 years) with 100 joints and 400 Metacarpophalangeal joints (2nd to 5th) including 2300 bone areas were evaluated. GSUS, PDUS evaluation was equal to contrast MRI evaluation in detecting joint space narrowing, effusion, flexor tenosynovitis (except for FPL tendon), extensor tenosynovitis. Whereas synovial thickening was better picked up in GSUS, PDUS than on contrast MRI. Contrast MRI picked up more cases of bone erosions, triangular fibro cartilage lesions and active synovitis as compared to GSUS, PDUS. Bone marrow edema which indicates active ostitis could only be directly detected on contrast MRI. Conclusions: GSUS, PDUS can be used as radiological investigative modality for the diagnosis of cases of early rheumatoid arthritis specially for synovial thickening, joint effusion, flexor and extensor tenosynovitis.

Multichannel ULF-MRI Study in Magnetic Unshielded Urban Laboratory Environment

Ultralow field (ULF) magnetic resonance imaging (MRI), which obtains images in the static magnetic field typically on the orders of tens to hundreds of microteslas, exhibits some potential advantages. However, the ULF-MRI system faces the challenge of poor signal-to-noise ratio (SNR). In addition to the introduction of a prepolarization technique and the usage of extremely sensitive superconducting quantum interference devices (SQUIDs), the multisensor parallel imaging technique can also improve the SNR and allow accelerated image acquisition. In this paper, a four-channel ULF-MRI system was built with low-T c SQUID-based second-order axial gradiometer in an urban laboratory environment without magnetic shield. To suppress the temporal field fluctuation and to balance the environment gradient field tensor, an active compensation and a gradient field shimming system were developed. Using the Fourier imaging method and weighted image superposition, the 2-D and 3-D four-channel MRI images of pepper pieces were obtained at a measurement field of 129 μT, i.e., a Larmor frequency of 5.5 kHz with an in-plane resolution of about 2 mm × 2 mm. These results demonstrated the feasibility of performing 2-D and 3-D multisensor parallel ULF MRI in the unshielded urban environment.

Diagnostic Capability of Low- Versus High-Field Magnetic Resonance Imaging for Lumbar Degenerative Disease

Cohort study. To investigate the diagnostic capability of low-field magnetic resonance imaging (MRI) compared with high-field MRI for degenerative disease of the lumbar spine. Low-field MRI has several advantages over high-field magnetic resonance systems (easier installation, lower purchase, and maintenance cost). The diagnostic capability of low-field MRI for degenerative disease of the lumbar spine has not been compared with that of high-field MRI. Hundred patients (mean age: 56.3 yr, range: 32-80; F:M = 59:41) with neurogenic claudication or sciatica were studied. All patients underwent MRI of the lumbar spine on both low-field (0.25T) and high-field (1.5T or 3.0T) magnetic resonance systems. Intervertebral disc herniation, central canal, lateral recess, and exit foraminal stenosis as well as nerve root compression at L3-L4, L4-L5, and L5-S1 were evaluated by 2 radiologists for both low- and high-field systems using established reliable grading systems. There was excellent agreement between low- and high- field MRI with regard to grading the presence and severity of disc herniation (r = 0.92-0.94; P < 0.05), central canal stenosis (r = 0.89-0.91; P < 0.05), lateral recess stenosis (r = 0.81-0.87; P < 0.05), and exit foramen stenosis (r = 0.81-0.89; P < 0.05). Descending or exiting nerve root compression occurred in 52% of patients at L3-L4, L4-L5, or L5-S1 levels, with good agreement between low-field and high-field MRI (r = 0.71-0.76; P < 0.05) for nerve root compression. Excellent reliability between low- and high- field MRI was found for most features of lumbar disc degeneration, with good agreement for nerve root compression. 0.25T MRI was more susceptible to motion artifact, probably due to longer scanning time. 3.

Do low field magnetic resonance imaging abnormalities correlate with macroscopical and histological changes within the equine deep digital flexor tendon?

Correlating magnetic resonance (MR) imaging and histopathological findings is essential to validate low field MR imaging in lame horses. This study aimed to compare signal changes in the deep digital flexor tendon (DDFT) of the distal limb on low field MR imaging with macroscopical and histological findings. Cadaver limbs from lame horses with DDFT lesions were selected. The DDFT MR imaging findings and histopathological results were graded, and macroscopical abnormalities were recorded. There was a strong correlation between MR imaging and histopathology grades (rs = 0.76, p < 0.001) in the foot. There was moderate agreement (Kappa statistic 0.52) between the MR and histopathology grades; agreement was superior further proximal in the foot. The presence and severity of pathology in the DDFT are well represented by the presence and severity of MR imaging signal changes. The study supports the use of low field MR imaging for diagnosis of equine distal limb DDFT lesions.

Ultrahigh field magnetic resonance and colour Doppler real-time fusion imaging of the orbit – a hybrid tool for assessment of choroidal melanoma

A combination of magnetic resonance images with real-time high-resolution ultrasound known as fusion imaging may improve ophthalmologic examination. This study was undertaken to evaluate the feasibility of orbital high-field magnetic resonance and real-time colour Doppler ultrasound image fusion and navigation. This case study, performed between April and June 2013, included one healthy man (age, 47 years) and two patients (one woman, 57 years; one man, 67 years) with choroidal melanomas. All cases underwent 7.0-T magnetic resonance imaging using a custom-made ocular imaging surface coil. The Digital Imaging and Communications in Medicine volume data set was then loaded into the ultrasound system for manual registration of the live ultrasound image and fusion imaging examination. Data registration, matching and then volume navigation were feasible in all cases. Fusion imaging provided real-time imaging capabilities and high tissue contrast of choroidal tumour and optic nerve. It also allowed adding a real-time colour Doppler signal on magnetic resonance images for assessment of vasculature of tumour and retrobulbar structures. The combination of orbital high-field magnetic resonance and colour Doppler ultrasound image fusion and navigation is feasible. Multimodal fusion imaging promises to foster assessment and monitoring of choroidal melanoma and optic nerve disorders. • Orbital magnetic resonance and colour Doppler ultrasound real-time fusion imaging is feasible • Fusion imaging combines the spatial and temporal resolution advantages of each modality • Magnetic resonance and ultrasound fusion imaging improves assessment of choroidal melanoma vascularisation.

Tibiofemoral joint osteoarthritis one year after anterior cruciate ligament reconstruction: a magnetic resonance imaging evaluation

s / Osteoarthritis and Cartilage 21 (2013) S63–S312 S196 371 TIBIOFEMORAL JOINT OSTEOARTHRITIS ONE YEAR AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION: A MAGNETIC RESONANCE IMAGING EVALUATION J. van Leeuwen y, N. Beck y, M. van Middelkoop y, A. Culvenor z, S. Bierma-Zeinstra y, E. Oei y, K. Crossley z. y ErasmusMC, Rotterdam, The Netherlands; zUniv. of Queensland, Brisbane, Australia Purpose: Radiographic tibiofemoral joint (TFJ) osteoarthritis (OA) is known to be common more than five years after anterior cruciate ligament injury and reconstruction (ACLR). Magnetic resonance (MR) imaging enables evaluation of early, pre-radiographic features of OA, which may be important for individuals at high risk of OA. Specifically, MR imaging may be useful to assess the onset of OA at an earlier stage after ACLR. A recently proposed tool to assess OA features and prevalence of TFJ OA from MR images is the MR Imaging Osteoarthritis Knee Score (MOAKS). This study aimed to (i) establish the reliability of the MOAKS in novice readers; (ii) describe the prevalence of OA features and TFJ OA one year after ACLR; and (iii) investigate the relationship between meniscal or cartilage damage at the time of ACLR and the presence of meniscal or cartilage damage one year later. Methods: One hundred and eighteen participants (65% male; age 31 9 years; BMI 26.1 4.0kg$m-2; median time from injury to surgery 3 months) who were approximately one year post ACLR with a single bundle hamstring tendon autograft were recruited from two orthopaedic surgery clinics. High field MR imaging at 3 Tesla was performed on all participants and the MOAKS was used by two novice readers (medical students), following an intensive training regimen by a musculoskeletal radiologist, to score specific features of OA and to evaluate the prevalence of TFJ OA based on published criteria. Interrater reliability was calculated using the kappa statistic. Binary logistic regression analysis was used to study the relationship between meniscal or cartilage damage at time of surgery and meniscal or cartilage damage on MR imaging one year later. Results: Most measures of inter-rater reliability from the MOAKS were substantial (78% of kappa values> 0.6). Osteoarthritis features appeared slightly more prevalent in the medial compartment than in the lateral compartment. Prevalence of bone marrow lesions in the medial and lateral compartment were 62% and 48%, respectively, with articular cartilage lesions (21% and 15%), osteophytes (30% and 26%) and meniscal damage (32% medial and 30% lateral) also frequently observed in both compartments. Of the 118 participants 17 (14%) met the criteria for TFJ OA, following the MOAKS scoring system. Cartilage damage one year post ACLR was predicted by cartilage damage present at time of surgery. Meniscal damage one year post ACLR observed from MR images was predicted by meniscal damage seen at time of surgery, age and gender. Conclusions: Inter-rater agreement between the two novice readers using the MOAKS instrument to evaluate OA features in the TFJ one year after ACLR was high. These results add to other data recently published on the MOAKS and indicate that the MOAKS may be used by different researchers with varying levels of experience and at the early stages of OA disease. Although TFJ OA and OA features identified on MR imaging are evident as early as one year after ACLR, the stability of these features, particularly BMLs, which may resolve or progress over time, is not well understood. Further research investigating whether these features are risk factors for disease progression is therefore warranted. Table 1 T1r, SNR, NRMS error values compared to 4 point full thickness standard.

3D gradient system for two B 0 field directions in earth’s field MRI

A new gradient system for earth's field magnetic resonance imaging (EFMRI) is presented that can be rotated relatively to the earth's field direction while maintaining the ability to encode images. Orthogonal components of the gradient field are exploited to reduce the number of gradient coils. Two favorable orientations of the gradient system relative to the earth's magnetic field (parallel and perpendicular) are discussed. We introduce the theory for the magnetic fields of the new gradient system and illustrate the design of the coil geometries which were worked out with the help of simulations and a numerical optimization algorithm. Field mapping measurements and imaging experiments in the two different orientations of the gradient system were carried out. Orthogonal components of the gradient field take over the role of the additionally needed gradient fields when the gradient system is rotated relative to the earth's magnetic field. The results from the field mapping and imaging experiments verify the presented theory and show the functionality of the new gradient system. The presented system demonstrates that gradient coils can be used for image encoding in multiple directions. This fact can be exploited to realize an EFMRI setup for parallel and perpendicular prepolarization with a single set of gradient coils.

High field magnetic resonance spectroscopy, imaging and elastography for cartilage tissue engineering

High field magnetic resonance spectroscopy, imaging and elastography for cartilage tissue engineering

Optimization of Flux Transformer for Optically Pumped Atomic Magnetometer in Ultra-Low Field MRI Systems

An ultra-low field (ULF) magnetic resonance imaging (MRI) system with an optically pumped atomic magnetometer (AM) has recently been proposed. Because AM does not require cryogenic cooling, it can easily measure extremely small magnetic fields. However, to measure magnetic resonance (MR) signals with high sensitivity in ULF-MRI systems with AMs, the resonant frequencies of the sample and alkali metal in the AM must be same. To satisfy this requirement, a flux transformer (FT) has been proposed to detect MR signals. In this study, the simulations in the output coil of the FT and pseudo-MR signal measurements were performed to improve the signal-to-noise ratio (SNR) in the remote detection of MR signals by using AM with FT. The simulations and measurement results indicate that, to improve the SNR of the detector, the output coil of the FT should be placed in the vicinity of a glass cell, and the number of turns and radius of the output coil need to be optimized.