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Aim: To propose a new multimodal imaging agent targeting amyloid-β (Aβ) plaques in Alzheimer’s disease. Materials & methods: A new generation of hybrid contrast agents, based on gadolinium fluoride nanoparticles grafted with a pentameric luminescent-conjugated polythiophene, was designed, extensively characterized and evaluated in animal models of Alzheimer’s disease through MRI, two-photon microscopy and synchrotron x-ray phase-contrast imaging. Results & conclusion: Two different grafting densities of luminescent-conjugated polythiophene were achieved while preserving colloidal stability and fluorescent properties, and without affecting biodistribution. In vivo brain uptake was dependent on the blood–brain barrier status. Nevertheless, multimodal imaging showed successful Aβ targeting in both transgenic mice and Aβ fibril-injected rats.

SummaryObjectiveThe purpose of this study was to evaluate meniscal degeneration in healthy subjects and subjects with osteoarthritis (OA) using T1ρ and T2 measurements and to examine the interrelationship between cartilage and meniscus abnormalities.MethodsQuantitative assessment of cartilage and meniscus was performed using 3T Magnetic Resonance Imaging (MRI) with a T1ρ and T2 mapping technique in 19 controls and 44 OA patients. A sagittal T2-weighted fast spin echo (FSE) fat-saturated image was acquired for cartilage and meniscal Whole-Organ Magnetic Resonance Imaging Score (WORMS) assessment. Western Ontario and McMasters Universities Arthritis Index (WOMAC) scores were obtained to assess clinical symptoms.ResultsThe posterior horn of the medial meniscus (PHMED) had the highest incidence of degeneration. Stratifying subjects on the basis of PHMED grade revealed that the T1ρ and the T2 measurements of the PHMED and the medial tibial (MT) cartilage were higher in subjects having a meniscal tear (meniscal grade 2–4) compared to subjects with a meniscal grade of 0 or 1 (P

SummaryObjectiveThe aim of this study was to assess the reproducibility of meniscus T1ρ measurements, and to study T1ρ relaxation time in the lateral meniscus (LM) and its relationship with adjacent cartilage T1ρ in knees with acute anterior cruciate ligament (ACL) injuries at 3T magnetic resonance imaging.MethodQuantitative assessment of the meniscus and cartilage was performed in 15 healthy controls and 16 ACL-injured patients using a T1ρ mapping technique. All ACL-injured patients were imaged prior to surgery within 1–3 months of injury. The anterior and posterior horns of LM and medial meniscus (MM) were associated with partitioned weight-bearing cartilage sub-compartments (anterior, central, and posterior).ResultsT1ρ measurements in the meniscus showed excellent reproducibility (coefficient of variation (CV)

SummaryObjectiveTo evaluate trabecular bone structure in relationship with cartilage parameters in distal femur and proximal tibia of the human knee at 3Tesla (3T) using high-resolution magnetic resonance imaging (MRI) with parallel imaging.MethodSixteen healthy controls and 16 patients with mild osteoarthritis (OA) were studied using a 3T magnetic resonance (MR) scanner and an eight-channel phased-array knee coil. Axial 3D GeneRalized Autocalibrating Partially Parallel Acquisition (GRAPPA)-based phase cycled Fast Imaging Employing Steady State Acquisition (FIESTA-c) images were acquired in order to quantify the trabecular bone structure. For assessing cartilage morphology (thickness, volume), sagittal high-resolution 3D spoiled gradient echo (SPGR) images were acquired. In a subset of the subjects, sagittal images were acquired for measuring T1ρ and T2 relaxation times, using 3D T1ρ and T2 mapping techniques.ResultsGood measurement reproducibility was observed for bone parameters, the coefficients of variations (CVs) ranging from 1.8% for trabecular number (app. Tb.N) to 5.5% for trabecular separation (app. Tb.Sp). Significant differences between control and OA groups were found for bone volume fraction bone volume over total volume (app. BV/TV) and app. Tb.Sp in all compartments. Significantly increased values in T1ρ and T2 were demonstrated in OA patients compared with controls at the femur, but not at the tibia. T1ρ was negatively correlated with app. BV/TV, app. Tb.N and app. Tb.Sp both at the medial femoral condyle (MFC) and lateral tibia (LT), while T2 was only correlated at the LT. Also, medial tibia (MT) T1ρ was negatively correlated with app. BV/TV (R2=−0.49, P

To assess the reproducibility of quantitative measurements of cartilage morphology and trabecular bone structure of the knee at 7 T, high-resolution sagittal spoiled gradient-echo images and high-resolution axial fully refocused steady-state free-precession (SSFP) images from six healthy volunteers were acquired with a 7-T scanner. The subjects were repositioned between repeated scans to test the reproducibility of the measurements. The reproducibility of each measurement was evaluated using the coefficient(s) of variation (CV). The computed CV were 1.13% and 1.55% for cartilage thickness and cartilage volume, respectively, and were 2.86%, 1.07%, 2.27% and 3.30% for apparent bone volume over total volume fraction (app.BV/TV), apparent trabecular number (app.Tb.N), apparent trabecular separation (app.Tb.Sp) and apparent trabecular thickness (app.Tb.Th), respectively. The results demonstrate that quantitative assessment of cartilage morphology and trabecular bone structure is reproducible at 7 T and motivates future musculoskeletal applications seeking the high-field strength's superior signal-to-noise ratio.

SummaryObjectiveThe aim of this study was to follow, over a 4½-month period, the medial tibia cartilage thickness on a meniscectomy (MNX) guinea pig osteoarthritis (OA) model and to compare with control animals, using three-dimensional high-resolution magnetic resonance imaging (3D HR-MRI).MethodsMRI experimentations were performed in vivo at 7T on guinea pig knee joints. 3D HR-MR images were acquired in 60 controls (SHAM) and 45 osteoarthritic animals (MNX) at four time-points (15, 45, 90 and 135 days) after surgery. Medial tibial cartilage thickness was measured from MRI images using in-house dedicated 3D software followed by a statistical analysis. At each time-point 15 SHAM and 15 MNX animals were sacrificed for histomorphometric assessments.ResultsNo significant difference of mean cartilage thickness between the groups was found at early stage (D45) using MRI; however, significant differences were found between the groups at D90 (P

The application of biomolecular magnetic resonance imaging becomes increasingly important in the context of early cartilage changes in degenerative and inflammatory joint disease before gross morphological changes become apparent. In this limited technical report, we investigate the correlation of MRI T1, T2 and T1 relaxation times with quantitative biochemical measurements of proteoglycan and collagen contents of cartilage in close synopsis with histologic morphology. A recently developed MR imaging sequence, T1, was able to detect early intracartilaginous degeneration quantitatively and also qualitatively by color mapping demonstrating a higher sensitivity than standard T2-w sequences. The results correlated highly with reduced proteoglycan content and disrupted collagen architecture as measured by biochemistry and histology. The findings lend support to a clinical implementation that allows rapid visual capturing of pathology on a local, millimeter level. Further information about articular cartilage quality otherwise not detectable in-vivo, via normal inspection, is needed for orthopedic treatment decisions in the present and future.

Purpose A direct correlation between T1ρ, T2 and quantified proteoglycan and collagen contents in human osteoarthritic cartilage has yet to be documented. We aimed to investigate the orientation effect on T1ρ and T2 values in human osteoarthritic cartilage and to quantify the correlation between T1ρ, T2 vs. biochemical composition and histology in human osteoarthritic cartilage. Materials and methods Thirty-three cartilage specimens were collected from patients who underwent total knee arthroplasty due to severe osteoarthritis and scanned with a 3T MR scanner for T1ρ and T2 quantification. Nine specimens were scanned at three different orientations with respect to the B0: 0°, 90° and 54.7°. Core punches were taken after MRI. Collagen and proteoglycan contents were quantified using biochemical assays. Histology sections were graded using Mankin scores. The correlation between imaging parameters, biochemical contents and histological scores were studied. Results Both mean T1ρ and T2 at 54.7° were significantly higher than those measured at 90° and 0°, with T1ρ showing less increase compared to T2. R1ρ (1/T1ρ) values had a significant but moderate correlation with proteoglycan contents (R=.45, P=.002), while R2 (1/T2) was not correlated with proteoglycan. No significant correlation was found between relaxation times (T1ρ or T2) and collagen contents. The T1ρ values of specimen sections with high Mankin scores were significantly higher than those with low Mankin scores (P Conclusions Quantitative MRI has a great potential to provide noninvasive imaging biomarkers for cartilage degeneration in osteoarthritis.

International audience; In the field of small animal studies, the array coil imaging has become increasingly important. In this paper, a dedicated two-channel array coil operating at 300 MHz (7 T) for high-resolution MRI (HR-MRI) of the rat knee cartilage is presented. The average gain in signal-to-noise ratio (SNR) compared to a 15-mm multipurpose surface coil was 2.2. This SNR gain was used to improve the spatial resolution of 3-D acquisitions by decreasing the voxel size from 59 x 59 x 156 microm(3) to 51 x 51 x 94 microm(3) without time penalty. Also, a set of two array coils was used to perform a simultaneous acquisition of both knee joints of a rat, maintaining the same scanning time without SNR or spatial resolution degradation compared to the single knee joint acquisition. This two-channel array coil is a key element to perform HR-MRI and extract cartilage morphological parameters such as thickness and volume.

OBJECTIVES to assess reliability and reproducibility of quantitative MRI (7 T) in assessing rat femoro-tibial cartilage volume. METHODS 5 healthy rat knees were scanned in vivo using a 7 T experimental imager. Sagittal high resolution 3D Gradient Echo with fat suppression sequences were performed with a dedicated home-made 2-elements array coil. 3D MRI sets were used to perform manual segmentation of the 3 cartilage compartments (femoral groove, medial and lateral tibial plateaus) by using a tactile screen. To evaluate inter- and intra-observer reproducibilities, the segmentation procedure was done blindly by two trained observers. One observer repeated the operation twice, with a period of 10 months between both readings. RESULTS the mean duration to manually segment all the slices covering the cartilaginous joint was 4 hours. On the one hand, the inter-observer root mean square of coefficients of variation was 9.1%, 6.2%, 9.6% for the femoral, medial and lateral tibial compartments respectively. On the other hand, the intra-observer reproducibility was 2.1%, 3.2%, 2.5% for these cartilage compartments cited above. CONCLUSION the image quality obtained at 7 Teslas with our dedicated coil allowed segmentation of the cartilage compartments with good reproducibility. This study demonstrated that MRI is a useful technology to provide a non-invasive and reliable assessment of rat knee cartilage volume.

Despite that on clinical systems phased array technology is now widely used, the high field MRI experimental systems with multiple receiver channels just became available few years ago. For this reason and due to the large range of magnetic field (frequencies between 200 and 500 MHz for proton resonance), commercial phased arrays implemented in narrow bore for high field applications are rare and relatively expensive. Array coil imaging is an advanced method for acquiring high resolution images with enhanced signal-to-noise ratio (SNR) and/or enlarged field of view (FOV) compared for example to single loop surface coil. The volume of interest is then covered by several coil elements and images reconstructed for every single channel are combined afterwards. The goal of this work was to develop a dedicated two-element array coil operating at 300 MHz (7 T) for high-resolution imaging of rat knee joint in order to quantify cartilage thickness and volume. A dedicated two-element array coil with two square elements encompassing knee joint was designed and built. Decoupling between elements was achieved with a capacitor inserted on the common leg of the two elements. The average gain in SNR compared to a 15 mm reference single loop coil was 2.2. This SNR gain was used to improve spatial resolution of 3D acquisition by decreasing the voxel size from 59 x 59 x 156 mum3 to 51 x 51 times 94 mum3 without time penalty. This two element array coil is a key element to perform HR-MRI and extract morphological parameters of animal cartilage. Finally, a set of two array coils were used to perform the acquisition of both rat knee joint at the same time with no additional acquisition time or resolution decrease.

Keywords: Mri ; cartilage ; articular contact ; morphology ; rat ; Articular-Cartilage Reference EPFL-CONF-169141doi:10.1080/10255840802298786View record in Web of Science Record created on 2011-09-29, modified on 2017-05-12