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Background Cartilage repair outcomes of matrix-associated stem cell implants (MASIs) in patients have been highly variable. Conventional MRI cannot help distinguish between grafts that will and grafts that will not repair the underlying cartilage defect until many months after the repair. Purpose To determine if ferumoxytol nanoparticle labeling could be used to depict successful or failed MASIs compared with conventional MRI in a large-animal model. Materials and Methods Between January 2016 and December 2017, 10 Göttingen minipigs ( n = 5 male; n = 5 female; mean age, 6 months ± 5.1; age range, 4-20 months) received implants of unlabeled ( n = 12) or ferumoxytol-labeled ( n = 20) viable and apoptotic MASIs in cartilage defects of the distal femur. All MASIs were serially imaged with MRI on a 3.0-T imaging unit at week 1 and weeks 2, 4, 8, 12, and 24, with calculation of T2 relaxation times. Cartilage regeneration outcomes were assessed by using the MR observation of cartilage repair tissue (MOCART) score (scale, 0-100), the Pineda score, and histopathologic quantification of collagen 2 production in the cartilage defect. Findings were compared by using the unpaired Wilcoxon rank sum test, a linear regression model, the Fisher exact test, and Pearson correlation. Results Ferumoxytol-labeled MASIs showed significant T2 shortening (22.2 msec ± 3.2 vs 27.9 msec ± 1.8; P < .001) and no difference in cartilage repair outcomes compared with unlabeled control MASIs ( P > .05). At week 2 after implantation, ferumoxytol-labeled apoptotic MASIs showed a loss of iron signal and higher T2 relaxation times compared with ferumoxytol-labeled viable MASIs (26.6 msec ± 4.9 vs 20.8 msec ± 5.3; P = .001). Standard MRI showed incomplete cartilage defect repair of apoptotic MASIs at 24 weeks. Iron signal loss at 2 weeks correlated with incomplete cartilage repair, diagnosed at histopathologic examination at 12-24 weeks. Conclusion Ferumoxytol nanoparticle labeling can accelerate the diagnosis of successful and failed matrix-associated stem cell implants at MRI in a large-animal model. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Sneag and Potter in this issue.

Objective: Aim of this study was, to demonstrate the feasibility of high-resolution grating-based X-ray phase-contrast computed tomography (PCCT) for quantitative assessment of cartilage., Materials and Methods: In an experimental setup, 12 osteochondral samples were harvested from n = 6 bovine knees (n = 2 each). From each knee, one cartilage sample was degraded using 2.5% Trypsin. In addition to PCCT and biomechanical cartilage stiffness measurements, 3T and 7T MRI was performed including MSME SE T2 and ME GE T2* mapping sequences for relaxationtime measurements. Paired t-tests and receiver operating characteristics (ROC) curves were used for statistical analyses., Results: PCCT provided high-resolution images for improved morphological cartilage evaluation as compared to 3T and 7T MRI. Quantitative analyses revealed significant differences between the superficial and the deep cartilage layer for T2 mapping as well as for PCCT (P<0.05). No significant difference was detected for PCCT between healthy and degraded samples (P>0.05). MRI and stiffness measurements showed significant differences between healthy and degraded osteochondral samples. Accuracy in the prediction of cartilage degradation was excellent for MRI and biomechanical analyses., Conclusion: In conclusion, high-resolution grating-based X-ray PCCT cartilage imaging is feasible. In addition to MRI and biomechanical analyses it provides complementary, water content independent, information for improved morphological and quantitative characterization of articular cartilage ultrastructure., Competing Interests: This work was supported in part by Arthrex GmbH (Munich, Germany). Dimitrios C. Karampinos and Peter B. Noël receive grant support from Philips Healthcare. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There are no patents, products in development or marketed products to declare. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials.

The objective of this work was to characterize tibial plateau coverage and morphometric differences of the medial (MM) and lateral meniscus (LM) in a male reference cohort using three-dimensional imaging. Coronal multiplanar reconstructions of a sagittal double-echo steady state with water excitation magnetic resonance sequence (slice thickness: 1.5 mm, and in-plane resolution: 0.37 × 0.70 mm) were analyzed in 47 male participants without symptoms, signs or risk factors of knee osteoarthritis of the reference cohort of the Osteoarthritis Initiative. The medial and lateral tibial (LT) plateau cartilage area and the tibial, femoral and external surfaces of the MM and LM were manually segmented throughout the entire knee. This process was assisted by parallel inspection of a coronal intermediately weighted turbo spin echo sequence. Measures of tibial coverage, meniscus size, and meniscus position were computed three-dimensionally for the total menisci, the body, and the anterior and the posterior horn. The LM was found to cover a significantly greater (p < 0.001) proportion of the LT plateau (59 ± 6.8%) than the MM of the medial plateau (50 ± 5.5%). Whereas the volume of both menisci was similar (2.444 vs. 2.438 ml; p = 0.92), the LM displayed larger tibial and femoral surface areas (p < 0.05) and a smaller maximal (7.2 ± 1.0 vs. 7.7 ± 1.1 mm; p < 0.01) and mean thickness (2.7 ± 0.3 vs. 2.8 ± 0.3 mm; p < 0.001) than the medial one. Also, the LM displayed less (physiological) extrusion than the medial one. These data may guide strategies for meniscal tissue engineering and transplantation aiming to restore normal joint conditions., (Copyright © 2011 S. Karger AG, Basel.)

MRI-based measures of cartilage morphology are being increasingly used as surrogate markers in osteoarthritis. In contrast to other knee joint surfaces, quantitative analysis of the femoral condyles from sagittal MRI suffers from limited precision. The objective, therefore, was to develop a technique for reproducible assessment of femoral cartilage morphology from coronal image data. Coronal MR images (3D T(1)-w FLASHwe) of the knee were obtained in 16 healthy volunteers and in 7 patients with severe osteoarthritis (OA, prior to knee arthroplasty), with repositioning between repeated scans. After segmentation the cartilage volume, thickness, and joint surface areas were quantified in the tibia and in an anatomically defined region of the femoral condyle. Immediate test-retest interscan precision errors (CV%) for femoral cartilage volume were 3.0% (SD = 26 microl) and 3.2% (29 microl) medially and laterally in volunteers, and 3.0% (34 microl) and 7.0% (37 microl) in OA patients. The estimated loss, from cross sectional data, in the patients in the medial femoral condyle (-61%/-4.4 SD) was higher than that in the medial tibia (-45%/-3.1 SD) and compared favorably with precision errors (ratio > 16:1). The technique proposed overcomes some of the problems associated with sagittal scans and thus shows high promise for reliable assessment of femoro-tibial cartilage loss in OA., (Copyright 2003 Wiley-Liss, Inc.)

Objective: T scores (an indicator of the difference between patients and young healthy subjects) and Z scores (an indicator of the difference between patients and age-matched healthy subjects) are used in the diagnosis of osteoporosis and form the current basis for the definition of osteoporosis by the World Health Organization. We tested the feasibility of using T and Z scores derived from quantitative cartilage imaging with magnetic resonance imaging (MRI) for the diagnosis of osteoarthritis (OA)., Methods: High-resolution MR images of tibial cartilage were acquired from 126 young healthy adults (ages 20-35 years), 24 age-matched elderly healthy adults (ages 50-75 years), 7 OA patients prior to tibial osteotomy, and 7 OA patients prior to knee arthroplasty. Cartilage volume, thickness, surface area, and original joint surface area (before onset of disease) were determined in the medial and lateral tibia., Results: The cartilage volume of the medial tibia of osteotomy patients with varus malalignment displayed moderate T scores (-1.0), and more negative T scores (-3.8) were observed in knee arthroplasty patients with varus malalignment. Normalization of the cartilage volume to the original joint surface area substantially enhanced the scores in patients undergoing osteotomy (-2.3) and in patients undergoing knee arthroplasty (-5.5), and this was superior to the normalization ratios of cartilage volume to body height and cartilage volume to body weight, in terms of distinguishing the loss of articular cartilage., Conclusion: Quantitative analysis of OA by MRI is feasible using T and Z scores. However, cartilage volume should be normalized to the individual joint surface area in order to maximize the discriminatory power of this technique for the diagnosis of OA.

The goal of this work is the design of highly accurate surgical navigation methods purely based on magnetic resonance imaging. In this context we numerically examine the geometrical distortions which occur in magnetic resonance imaging. We extend an existing method for computing magnitude and direction of distortions for any internal point. In particular, a multi-grid approach for a fast and efficient calculation of the static magnetic field throughout the imaging volume is presented and compared to the analytical solution for simple geometries. We found that shifts in the range of up to 2.5 mm occur in MRI of femur bones with 1.5 Tesla. Our new method was implemented and has been found capable of accurately correcting for geometrical distortions within reasonable computing times. In particular, we show that the registration accuracy for mutual information (MI) based MR-CT fusion can be much improved. Thus the value of the optimization functional in MI registration for MR-CT substantially increases after our distortion correction.

Objective: Follow up of osteoarthritis (OA) and evaluation of structure modifying OA drugs require longitudinal data on cartilage structure. The aim of this study was to analyse the long term and resegmentation precision of quantitative cartilage analysis with magnetic resonance imaging (qMRI) in vivo, and to relate precision errors to the estimated cartilage loss in OA., Method: Sagittal MR images of the knee were obtained in 14 individuals, four datasets being acquired in a first imaging session. In 12 subjects, two further datasets were acquired over the next months. Image analysis was performed in the same session for image data obtained under short-term and long-term imaging conditions, and in three different sessions (months apart) for the first data set (resegmentation precision)., Results: Long-term precision errors ranged from 1.4% (total knee) to 3.9% (total femur) for cartilage volume and thickness and were only marginally higher than those under short term conditions. In the medial tibia, the error was 84 mm(3) compared with an estimated loss of >1,200 mm(3) in varus OA. Precision errors for resegmentation were somewhat higher, but considerably smaller than the intersubject variability., Conclusions: Scanner drift and changes in imaging or patient conditions appear not to represent a critical problem in quantitative cartilage analysis with magnetic resonance imaging (qMRI). In longitudinal studies, image analysis of sequential data should be performed within the same post-processing session. Under these conditions, qMRI promises to be a very powerful method to assess structural change of cartilage in OA., (Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd.)

Objective: To examine the in vivo accuracy and precision of magnetic resonance imaging (MRI)-based assessment of cartilage loss in patients with severe osteoarthritis (OA) of the knee., Methods: High-resolution MRI images of the tibial cartilage were obtained in 8 patients prior to total knee arthroplasty, using a water-excitation gradient-echo MRI sequence (acquisition time 6 minutes 19 seconds; spatial resolution 1.2 x 0.31 x 0.31 mm3). The MRI measurements were repeated after joint repositioning. The precision of the cartilage volume and thickness computations was determined after 3-dimensional reconstruction. During surgery, the tibial plateaus were resected, and the MRI data were compared with water displacement of surgically retrieved cartilage., Results: The standard deviation (coefficient of variation) of repeated tibial cartilage volume measurements was 56 mm3 (5.5%) medially and 59 mm3 (3.8%) laterally. The deviation from surgically removed tissue was -13%, on average, with a high linear correlation between both methods (r = 0.98). In patients with varus OA, the tissue loss was estimated to be 1,290 mm3 in the medial tibia and 1,150 mm3 in the lateral tibia, compared with the data in healthy volunteers., Conclusion: Noninvasive quantitative MRI-based analysis of cartilage morphometry in severe OA is accurate, precise, and displays high potential diagnostic value.

The aim of this study was to analyze the precision of tibial cartilage morphometry, by using a fast, coronal water-excitation sequence with high spatial resolution, to compare the reproducibility of 3D thickness vs volume estimates, and to test the technique in patients with severe osteoarthritis. The tibiae of 8 healthy volunteers and 3 patients selected for total knee arthroplasty were imaged repeatedly with a water-excitation sequence (image time 6 h 19 min, resolution 1.2 x 0.31 x 0.31 mm(3)), with the knee being repositioned between each replicate acquisition. After 3D reconstruction, the cartilage volume, the mean, and the maximal tibial cartilage thickness were determined by 3D Euclidean distance transformation. In the volunteers, the precision of the volume measurements was 2.3 % (CV%) in the medial and 2.6 % in the lateral tibia. The reproducibility of the mean cartilage thickness was similar (2.6 and 2.5 %, respectively), and that of the maximal thickness lower (6.5 and 4.4 %). The patients showed a considerable reduction in volume and thickness, the precision being comparable with that in the volunteers. We find that, using a new imaging protocol and computational algorithm, it is possible to determine tibial cartilage morphometry with high precision in healthy individuals as well as in patients with osteoarthritis.

We assessed the anatomy of the anterior cruciate ligament (ACL) and femoral intercondylar notch on cryosections from one cadaveric knee specimen in the coronal oblique plane oriented parallel to the intercondylar roof. We determined the course of the ACL, the widths of the cruciate ligaments at intersection, and the intercondylar notch configuration on coronal oblique plane magnetic resonance images in 51 adult cruciate ligament-intact knees (25 women, 26 men; age range, 16 to 47 years). The intercondylar notch widths were measured at the notch entrance, at the intersection of the ACL and posterior cruciate ligament (PCL), and at the notch outlet. In the coronal oblique plane, the ACL exhibited a diagonal course from the central and medial part of the anterior intercondylar area of the tibia distally, across the lateral third of the intercondylar notch, to the intercondylar surface of the lateral femoral condyle proximally. At the cruciate ligament intersection, the absolute widths of the ACLs measured on average 6.1+/-1.1 mm in men and 5.2+/-1.0 mm in women representing 31.9% and 31.1% of the ACL/central intercondylar notch width ratios. The absolute widths of the PCLs measured on average 9.6+/-1.3 mm in men and 8.5+/-1.3 mm in women representing 50.4% and 51.4% of PCL/central intercondylar notch width ratios. On average for both groups, men and women, the absolute widths of the PCLs were significantly larger than the absolute widths of the ACLs. However, the relative widths of the cruciate ligaments with respect to corresponding intercondylar notch widths were not significantly different. In the coronal oblique plane, the intercondylar notch widths showed on average a significant decrease from posterior to intersection and from intersection to anterior. At notch outlet, the mean notch width measured 21.4 mm in men and 18.5 mm in women. At intersection, the mean notch width measured 19.1 mm in men and 16.6 mm in women. At notch entrance, the notch width measured 14.6+/-1.8 mm in men and 12.7+/-2.1 mm in women. We recommend magnetic resonance tomography of the knee in the coronal oblique plane oriented parallel to the intercondylar roof as the imaging modality of choice to visualize accurately the anatomic diagonal course of the ACL and its relation to the intercondylar notch and posterior cruciate ligament complex.

Ruptures of the cruciate ligaments continue to pose both diagnostic and therapeutic problems. On the basis of structural analysis of MR images obtained after the accident and the results of conservative treatment, it can be shown that function healing of the rupture can result, when, for example, the synovial membrane (capsule) is preserved (70%). It proved possible to show and objectify this using MRI and measurements.

Objective: Magnetic resonance imaging (MRI) of articular cartilage has evolved to be an important tool in research on cartilage (patho)physiology and osteoarthritis (OA). MRI provides a wealth of novel and quantitative information, but there exists no commonly accepted terminology for reporting these metrics. The objective of this initiative was to propose a nomenclature for definitions and names to be used in scientific communications and to give recommendations as to which minimal methodological information should be provided when reporting MRI-based measures of articular cartilage in OA.Methods: An international group of experts with direct experience in MRI measurement of cartilage morphology or composition reviewed the existing literature. Through an iterative process that included a meeting with a larger group of scientists and clinicians (December 2nd, 2004, Chicago, IL, USA), they discussed, refined, and proposed a nomenclature for MRI-based measures of articular cartilage in OA.Results: The group proposes a nomenclature that describes: (1) the anatomical location and (2) the structural feature being measured, each name consisting of a metric variable combined with a tissue label. In addition, the group recommends minimal methodological information that should be described.Conclusions: Utilization of this nomenclature should facilitate communication within the scientific community. Further, the uniform adoption of comprehensive nomenclature to describe quantitative MRI- features of articular cartilage should strengthen epidemiological, clinical, and pharmacological studies in OA. [ABSTRACT FROM AUTHOR]