Magnetic resonance imaging of articular cartilage and evaluation of cartilage disease

Insights into the Age Dependency of Compositional MR Biomarkers Quantifying the Health Status of Cartilage in Metacarpophalangeal Joints

(1) Background: We aim to investigate age-related changes in cartilage structure and composition in the metacarpophalangeal (MCP) joints using magnetic resonance (MR) biomarkers. (2) Methods: The cartilage tissue of 90 MCP joints from 30 volunteers without any signs of destruction or inflammation was examined using T1, T2, and T1ρ compositional MR imaging techniques on a 3 Tesla clinical scanner and correlated with age. (3) Results: The T1ρ and T2 relaxation times showed a significant correlation with age (T1ρ: Kendall-τ-b = 0.3, p < 0.001; T2: Kendall-τ-b = 0.2, p = 0.01). No significant correlation was observed for T1 as a function of age (T1: Kendall-τ-b = 0.12, p = 0.13). (4) Conclusions: Our data show an increase in T1ρ and T2 relaxation times with age. We hypothesize that this increase is due to age-related changes in cartilage structure and composition. In future examinations of cartilage using compositional MRI, especially T1ρ and T2 techniques, e.g., in patients with osteoarthritis or rheumatoid arthritis, the age of the patients should be taken into account.

Early diagnosis of degenerative changes in the articular/fibrocartilaginous disc of the temporomandibular joint in patients with temporomandibular disorders using delayed gadolinium-enhanced MRI at 3 Tesla - preliminary results

BACKGROUND

Delayed gadolinium enhanced MRI of cartilage (dGEMRIC) is a quantitative method for assessment of glycosaminoglycan content in connective tissues. We hypothesize that the early diagnosis of degenerative changes in the temporomandibular joint could be diagnosed using dGEMRIC technique.

PURPOSE

To test the compositional MRI technique, dGEMRIC, at 3 Tesla to diagnosis early the degenerative changes in the fibrocartilaginous disc of the temporomandibular joint (TMJ) in patients with temporomandibular disorders (TMD) and to compare the dGEMRIC index of patients to the healthy volunteers.

METHODS

Six volunteers (two men, four women; 20.8÷28.1 years) and eleven patients (22 TMJs, seven women, four men; 24÷54 years) were recruited for this prospective trial. Only patients with no morphological abnormality on MRI and without disc dislocations were included. Volunteers were used as a control group. The PD-weighted FSE sequence and the 3D GRE (DESS) sequence protocols were performed for morphological assessment. The Inversion recovery (IR) sequence was performed for T1 relaxation time measurements and intra-venous (IV) contrast agent administration was used according to the dGEMRIC protocol. T1 maps were calculated offline and ROIs were drawn on TMJ discs by a specialist trained in TMD disorders. Statistical evaluation was performed by ANOVA and correlations were calculated.

RESULTS

The difference between the dGEMRIC values in the TMJ articular discs of the patients and the volunteers was statistically significant (P = .019). After contrast agent administration the T1 values dropped in both groups. In patient group was the T1 drop stronger (-54% from initial pre-contrast value), while in control group was the T1 drop less pronounced (-46% from initial pre-contrast value).

CONCLUSIONS

dGEMRIC seems to be a useful, compositional, quantitative method, suitable also for small joints, such as the articular disc of the TMJ. The results of the dGEMRIC index in the articular disc of the TMJ imply a lower GAG content in patients with TMJ disorders.

Changes in Cartilage and Tendon Composition of Patients With Type I Diabetes Mellitus: Identification by Quantitative Sodium Magnetic Resonance Imaging at 7 T

OBJECTIVE

The aim of this study was to investigate possible biochemical alterations in tendons and cartilage caused by type 1 diabetes mellitus (DM1), using quantitative in vivo 7 T sodium magnetic resonance (MR) imaging.

MATERIALS AND METHODS

The institutional review board approved this prospective study, and written informed consent was obtained. Eight DM1 patients with no history of knee trauma and 9 healthy age- and weight-matched volunteers were examined at 7 T using dedicated knee coils.All participants underwent morphological and sodium MR imaging. Region-of-interest analysis was performed manually for the non-weight-bearing area of the femoral condyle cartilage and for the patella tendon. Two readers read the image data sets independently, twice, for intrareader and interreader agreement. Normalized mean sodium signal intensity (NMSI) values were compared between patients and volunteers for each reader using analysis of variance.

RESULTS

On morphological images, cartilage in the non-weight-bearing area and the patellar tendon was intact in all patients. On sodium MR imaging, bivariate analysis of variance showed significantly lower mean NMSI values in the cartilage (P = 0.008) and significantly higher values in the tendons (P = 0.025) of patients compared with those of volunteers.

CONCLUSION

Our study showed significantly different NMSI values between DM1 patients and matched volunteers. Differences observed in the cartilage and tendon might be associated with a DM1-related alteration of biochemical composition that occurs before it can be visualized on morphological MR sequences.

Preclinical evaluation of (99m)Tc labeled chondroitin sulfate for monitoring of cartilage degeneration in osteoarthritis

PURPOSE

In previous in-vitro and ex-vivo studies we proved the specific uptake of (99m)Tc radiolabeled chondroitin sulfate (CS) in human articular cartilage. As a logical next step for the clinical use for imaging osteoarthritis we investigated in-vivo uptake of (99m)TcCS in dogs.

PROCEDURES

The radiolabeling of CS Condrosulf (IBSA, Lugano, Switzerland) was performed using 25mg of CS and 20-40MBq/kg body weight of (99m)Tc by means of the tin method. In-vivo uptake of (99m)TcCS was evaluated in dogs (n=12, castrated males, 4-9years, with 15-51kg body weight). 6 healthy dogs served as controls and 6 with clinical and radiological signs of osteoarthritis in the carpal, elbow, and tarsal joint were examined. The tracer was i.v. injected into the external cephalic vein. The uptake was monitored after 2, 4, 6 and 24h in healthy and osteoarthritic dogs using a planar gamma camera by regional planar or whole body ventral and dorsal acquisition. For whole body scintigraphy animals were under general anesthesia, for planar under sedation only.

RESULTS

In healthy control dogs we did not detect any specific uptake of (99m)TcCS in the cartilage. In contrast, in the diseased dogs suffering from osteoarthritis a significant, specific, persistent uptake between 4 and 6h in tarsal, carpal and cubital joints was documented. Median target (joint) to background (mid antebrachium) ratio (T/B) in the OA joints after 4, 6, and 24h was significantly higher than in healthy controls. Target to background ratio using soft tissue as a background (T/S) a similar significantly higher than in healthy controls. In all osteoarthritic joints we found a significant positive correlation (r=0.8, n=20) between grade of disease (I-III) and T/B. When matching radiographic (X ray) changes in osteoarthritic joints (grade II and III) we found also a maximal uptake of (99m)TcCS at the specific anatomical site of highest cartilage degeneration. None of the dogs experienced any side effects.

CONCLUSION

These results suggest that (99m)TcCS might become a promising diagnostic tool for imaging osteoarthritis. More extensive and detailed examinations are required, however, before extending this methodology for application in humans.

Magnetic resonance imaging of the ear for patient-specific reconstructive surgery

Introduction

Like a fingerprint, ear shape is a unique personal feature that should be reconstructed with a high fidelity during reconstructive surgery. Ear cartilage tissue engineering (TE) advantageously offers the possibility to use novel 3D manufacturing techniques to reconstruct the ear, thus allowing for a detailed auricular shape. However it also requires detailed patient-specific images of the 3D cartilage structures of the patient’s intact contralateral ear (if available). Therefore the aim of this study was to develop and evaluate an imaging strategy for acquiring patient-specific ear cartilage shape, with sufficient precision and accuracy for use in a clinical setting.

Methods and Materials

Magnetic resonance imaging (MRI) was performed on 14 volunteer and six cadaveric auricles and manually segmented. Reproducibility of cartilage volume (Cg.V), surface (Cg.S) and thickness (Cg.Th) was assessed, to determine whether raters could repeatedly define the same volume of interest. Additionally, six cadaveric auricles were harvested, scanned and segmented using the same procedure, then dissected and scanned using high resolution micro-CT. Correlation between MR and micro-CT measurements was assessed to determine accuracy.

Results

Good inter- and intra-rater reproducibility was observed (precision errors <4% for Cg.S and <9% for Cg.V and Cg.Th). Intraclass correlations were good for Cg.V and Cg.S (>0.82), but low for Cg.Th (<0.23) due to similar average Cg.Th between patients. However Pearson’s coefficients showed that the ability to detect local cartilage shape variations is unaffected. Good correlation between clinical MRI and micro-CT (r>0.95) demonstrated high accuracy.

Discussion and Conclusion

This study demonstrated that precision and accuracy of the proposed method was high enough to detect patient-specific variation in ear cartilage geometry. The present study provides a clinical strategy to access the necessary information required for the production of 3D ear scaffolds for TE purposes, including detailed patient-specific shape. Furthermore, the protocol is applicable in daily clinical practice with existing infrastructure.

Ankle post-traumatic osteoarthritis: a CT arthrography study in patients with bi- and trimalleolar fractures

PURPOSE

To detect radiographically occult cartilage lesions using CT arthrography (CTa) in patients with malleolar fractures treated with open reduction internal fixation and to correlate the lesions with the functional outcome score.

MATERIALS AND METHODS

Twenty-one patients (13 men and 8 women, mean age 35 years, range 16-55) underwent ankle CTa after a mean postoperative period of 565 days (range 271-756). CTa images were analyzed by two radiologists. Articular surface post-traumatic collapse and subsequent cartilage defects or erosions were recorded in millimeters and in a binary mode (i.e., present if >50% of cartilage thickness) respectively. The functional outcome was assessed using the American Orthopedic Foot and Ankle Society (AOFAS) score by two orthopaedic surgeons. The statistical analysis correlated the AOFAS score with both imaging parameters and was performed with ANOVA using the MedCalc statistical package, version 11.3.

RESULTS

Of the total of 12 articular surface steps recorded, 2/12 (16.67%) were anterolateral, 4/12 (33.33%) posterolateral, 5/12 (41.67%) anteromedial, and 1/12(8.33%) posteromedial. Of the total of 42 cartilage lesions, 7/42 (16.67%) were anterolateral, 14/42 (33.33%) posterolateral, 12/42 (28.57%) anteromedial, and 9/42 (21.43%) posteromedial. The mean AOFAS score was 8.67 (range 5.95-9.70). There was no statistically significant correlation between the AOFAS score and the post-traumatic internal derangement of the ankle joint (p = 0.524).

CONCLUSION

CTa detects radiographically silent cartilage lesions in patients with fractures of the ankle joint. There is no correlation of the extent of lesions and the patient's AOFAS score.

Multichannel transceiver dual-tuned RF coil for proton/sodium MR imaging of knee cartilage at 3 T

Sodium magnetic resonance (MR) imaging is a promising technique for detecting changes of proteoglycan (PG) content in cartilage associated with knee osteoarthritis. Despite its potential clinical benefit, sodium MR imaging in vivo is challenging because of intrinsically low sodium concentration and low MR signal sensitivity. Some of the challenges in sodium MR imaging may be eliminated by the use of a high-sensitivity radiofrequency (RF) coil, specifically, a dual-tuned (DT) proton/sodium RF coil which facilitates the co-registration of sodium and proton MR images and the evaluation of both physiochemical and structural properties of knee cartilage. Nevertheless, implementation of a DT proton/sodium RF coil is technically difficult because of the coupling effect between the coil elements (particularly at high field) and the required compact design with improved coil sensitivity. In this study, we applied a multitransceiver RF coil design to develop a DT proton/sodium coil for knee cartilage imaging at 3 T. With the new design, the size of the coil was minimized, and a high signal-to-noise ratio (SNR) was achieved. DT coil exhibited high levels of reflection S11 (∼-21 dB) and transmission coefficient S12 (∼-19 dB) for both the proton and sodium coils. High SNR (range 27-38) and contrast-to-noise ratio (CNR) (range 15-21) were achieved in sodium MR imaging of knee cartilage in vivo at 3-mm(3) isotropic resolution. This DT coil performance was comparable to that measured using a sodium-only birdcage coil (SNR of 28 and CNR of 20). Clinical evaluation of the DT coil on four normal subjects demonstrated a consistent acquisition of high-resolution proton images and measurement of relative sodium concentrations of knee cartilages without repositioning of the subjects during the same MR scanning session.

Radiological evaluation of cartilage after microfracture treatment: a long-term follow-up study

INTRODUCTION

Recent literature revealed good short-term results after microfracturing (MFX) of isolated focal cartilage defects in the knee joint. Study purpose was a long-term evaluation of patients who received MFX through a multimodal approach, correlating clinical scores and morphological pre- and postoperative MRI-scans.

MATERIALS AND METHODS

Between 2000 and 2007 158 patients were treated with MFX for focal femoral or tibial defects at our department. Patients with instabilities, secondary surgical intervention, patellofemoral lesions, a plica mediopatellaris or more than one cartilage defect site and age >55 were excluded. 15 patients were included. Minimum postoperative follow-up (FU) was 18 months (18-78 m). Mean age at surgery was 45 years (27-54), mean FU-interval 48 months (18-78 m). Male to female ratio was 9:6. For clinical assessment the Knee Osteoarthritis Ou tcome Score (KOOS) and Lysholm Score were used, radiological evaluation was performed with radiographs and 3Tesla-MRI.

RESULTS

Clinical knee function was rated good to excellent in 1 patient, fair in 2 and poor in 10 patients. 2/15 patients received full knee replacement due to insufficient cartilage repair through MFX during FU period. Evaluation of pre- and postoperative MRI showed good cartilage repair tissue in 1 (7.7%), moderate repair in 2 (15.4%) and poor fill in 10 patients (76.9%). In these 10 patients the defect size increased. Average defect size preoperatively was 187 mm(2) (range 12-800 mm(2)) and postoperatively 294 mm(2) (40-800 mm(2)). The KOOS-Pain averaged 60 (39-94), KOOS-Symptoms 60.6 (21-100), KOOS-ADL 69 (21-91), KOOS-Sports 35.7 (5-60) and KOOS-QUL 37.2 (6-81). The average Lysholm Score was 73.9 (58-94). 10 patients showed a varus leg axis deviation (Ø 5.9°), 3 had a neutral alignment. The alignment correlated positively with KOOS and especially with the Lysholm Score.

CONCLUSION

Our study demonstrated that MFX as a treatment option for cartilage defect in the knee did not show the anticipated clinical and radiological long-term results. In 12 of 15 patients the cartilage defect size had increased after MFX, in 2 patients indicating full-knee replacement. Especially those with a leg malalignment >5° in varus were more prone to suffer from an increase in defect size. In our cohort the clinical scores correlated with the radiological findings.

The current state of imaging the articular cartilage of the upper extremity

MR imaging has increasingly been used to image joints since its inception. Historically, there has been more emphasis on the evaluation of internal derangement rather than cartilaginous disease. This article reviews cartilaginous diseases of the upper extremity emphasizing those that can be assessed using current clinical MR imaging protocols and addresses the limitations of current imaging techniques in evaluating the articular cartilage of smaller joints. It also provides a brief overview of novel techniques that may be instituted in the future to improve the diagnostic performance of MR imaging in the evaluation of the articular cartilage of the upper extremity.

Matrix-induced autologous chondrocyte implantation of the knee: mid-term and long-term follow-up by MR arthrography

OBJECTIVE

To define magnetic resonance (MR) arthrography imaging findings of matrix-induced autologous chondrocyte implantation (MACI) grafts of the knee in order to describe implant behaviour and to compare findings with validated clinical scores 30 and 60 months after MACI implant.

MATERIALS AND METHODS

Thirteen patients were recruited (10 male, 3 female) with a total number of 15 chondral lesions. Each patient underwent an MACI procedure and MR arthrography 30 and 60 months after surgery. MR arthrography was performed using a dedicated coil with a 1.5-Tesla unit. The status of the chondral implant was evaluated with the modified MOCART scoring scale. The lining of the implant, the integration to the border zone, the surface and structure of the repaired tissue were assessed, and the presence of bone marrow oedema and effusion was evaluated. For clinical assessment, the Cincinnati score was used.

RESULTS

At 60 months, the abnormality showed worsening in 1 out of 15 cases. Integration showed improvement in 3 out of 15 cases, and worsening in 3 out of 15 cases. Two surfaces of the implant showed further deterioration at 60 months, and 1 afflicted implant fully recovered after the same time interval. Implant contrast enhancement at 30 months was seen in 2 out of 15 cases, 1 of which recovered at 60 months. According to the MOCART score, 4 cases were rated 68.4 out of 75 at 30 months and 65 out of 75 at 60 months. The mean clinical score decreased from 8.6 out of 10 at 30 months to 8.1 out of 10 at 60 months.

CONCLUSION

Magnetic resonance arthrography improved the evaluation of implants and facilitated the characterisation of MACI integration with contiguous tissues. The follow-up showed significant changes in MACI, even at 60 months, allowing for useful long-term MR evaluations.

MR imaging of the knee: Improvement of signal and contrast efficiency of T1-weighted turbo spin echo sequences by applying a driven equilibrium (DRIVE) pulse

The purpose of this study was to assess the effect of a driven equilibrium (DRIVE) pulse incorporated in a standard T1-weighted turbo spin echo (TSE) sequence as used in our routine MRI protocol for examination of pathologies of the knee. Sixteen consecutive patients with knee disorders were examined using the routine MRI protocol, including T1-weighted TSE-sequences with and without a DRIVE pulse. Signal-to-noise ratios (SNRs) and contrast-to-noise ratio (CNR) of anatomical structures and pathologies were calculated and compared for both sequences. The differences in diagnostic value of the T1-weighted images with and without DRIVE pulse were assessed. SNR was significantly higher on images acquired with DRIVE pulse for fluid, effusion, cartilage and bone. Differences in the SNR of meniscus and muscle between the two sequences were not statistically significant. CNR was significantly increased between muscle and effusion, fluid and cartilage, fluid and meniscus, cartilage and meniscus, bone and cartilage on images acquired using the DRIVE pulse. Diagnostic value of the T1-weighted images was found to be improved for delineation of anatomic structures and for diagnosing a variety of pathologies when a DRIVE pulse is incorporated in the sequence. Incorporation of a DRIVE pulse into a standard T1-weighted TSE-sequence leads to significant increase of SNR and CNR of both, anatomical structures and pathologies, and consequently to an increase in diagnostic value within the same acquisition time.

Rapid isotropic 3D-sodium MRI of the knee joint in vivo at 7T

PURPOSE

To demonstrate the feasibility of acquiring high-resolution, isotropic 3D-sodium magnetic resonance (MR) images of the whole knee joint in vivo at ultrahigh field strength (7.0T) via a 3D-radial acquisition with ultrashort echo times and clinically acceptable acquisition times.

MATERIALS AND METHODS

Five healthy controls (four males, one female; mean +/- standard deviation [SD] age 28.7 +/- 4.8 years) and five patients with osteoarthritis (OA) (three males, two females; mean +/- SD age 52.4 +/- 5.6 years) underwent (23)Na MRI on a 7T, multinuclei equipped whole-body scanner. A quadrature (23)Na knee coil and a 3D-gradient echo (GRE) imaging sequence with a radial acquisition were utilized. Cartilage sodium concentration was measured and compared between the healthy controls and OA patients.

RESULTS

The average signal-to-noise ratio (SNR) for different spatial resolutions (1.2-4 mm) varied from approximately 14-120, respectively. The mean sodium concentration of healthy subjects ranged from approximately 240 +/- 28 mM/L to 280 +/- 22 mM/L. However, in OA patients the sodium concentrations were reduced significantly by approximately 30%-60%, depending on the degree of cartilage degeneration.

CONCLUSION

The preliminary results suggest that sodium imaging at 7T may be a feasible potential alternative for physiologic OA imaging and clinical diagnosis.

[Coxarthrosis--an update]

Degenerative osteoarthritis of the hip joint (coxarthrosis) is the most common disease of the hip joint in adults. The diagnosis is based on a combination of radiographic findings and characteristic clinical symptoms. The lack of a radiographic consensus definition has seemingly resulted in a variation of the published incidences and prevalence of degenerative osteoarthritis of the hip joint. The chronological sequence of degeneration includes the following basic symptoms on conventional radiographs and CT: joint space narrowing, development of osteophytes, subchondral demineralisation/sclerosis and cyst formation, as well as loose bodies, joint malalignment and deformity. MR imaging allows additional visualization of early symptoms and/or activity signs such as cartilage edema, cartilage tears and defects, subchondral bone marrow edema, synovial edema and thickening, joint effusion and muscle atrophy.The scientific dispute concerns the significance of (minimal) joint malalignment (e.g. impingement, dysplasia etc.) and forms of malpositioning which as possible prearthrosis have a high probability of leading to degenerative osteoarthritis. Moreover, without any question, the preservation of joint containment and gender differences are important additional basic diagnostic principles, which have gained great interest in recent years.In research different MR procedures such as Na and H spectroscopy, T2*-mapping etc. with ultrahigh field MR allow cartilage metabolism and its changes in early degenerative osteoarthritis ("biochemical imaging") to be studied. There is no doubt that even in a few years new profound knowledge is to be expected in this field.

Optimal 99mTc radiolabeling and uptake of glucosamine sulfate by cartilage. A potential tracer for scintigraphic detection of osteoarthritis

Glucosamine sulfate (GS) is used in treatment of human osteoarthritis, but no data for(99m)TcGS scintigraphy are available. Radiolabeling of GS was performed using the (99m)TcO(4)(-)/tin method. We applied two procedures for separation of free (99m)Tc using PD10 and G10 columns. In each eluted fraction, GS content was estimated by the Elson/Morgan method. For optimal radiolabeling, we varied the amount of GS, tin, (99m)Tc activity, and pH. For uptake age matched human rib cartilage (males, 78 and 63 years old) and 5-10 μCi/well of (99m)TcGS were used. Uptake was monitored up to 72 h. Also, washout of the tracer 3 h and 24 h after uptake was investigated. At pH 2, using PD10 column, the uptake of (99m)TcGS amounted to 100.8 ± 2.9%, n = 6 at saturation time of 72 h. Uptake was age-dependent; at pH 5, it amounted to 99.8% as compared to 66.1% at 78 vs 63 years old. When the amount of tin was varied at pH 2, the tracer uptake amounted to 21.37% (1 mg) vs 45.99% (2.5 mg) at saturation. At pH 7, the amount of needed tin was much lower and amounted to 42.50 ± 2.50% using 0.1 mg vs 25.11 ± 1.90% using 0.05 mg. Although the uptake at pH 7 (0.1 mg tin) is comparable with that at pH 2 (2.5 mg tin), the washout of the tracer amounted only to 4.10 ± 1.25% and 2.05 ± 0.65% after 3 h and 24 h, respectively. During degeneration of cartilage, incorporation of (99m)TcGS is high and could therefore be a promising tracer not only to target osteoarthritis but also to monitor the effects of therapy.

MRI evaluation of a new scaffold-based allogenic chondrocyte implantation for cartilage repair

AIM

The present study was designed to evaluate the implantation of alginate beads containing human mature allogenic chondrocytes for the treatment of symptomatic cartilage defects of the knee. MRI was used for the morphological analysis of cartilage repair. The correlation between MRI findings and clinical outcome was also studied.

METHODS

A biodegradable, alginate-based biocompatible scaffold containing human mature allogenic chondrocytes was used for the treatment of symptomatic chondral and osteochondral lesions in the knee. Twenty-one patients were prospectively evaluated with use of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Visual Analogue Scale (VAS) for pain preoperatively and at 3, 6, 9 and 12 months of follow-up. Of the 21 patients, 12 had consented to follow the postoperative MRI evaluation protocol. MRI data were analyzed based on the original MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) and modified MOCART scoring system. The correlation between the clinical outcome and MRI findings was evaluated.

RESULTS

A statistically significant clinical improvement became apparent after 6 months and patients continued to improve during the 12 months of follow-up. One of the two MRI scoring systems that were used, showed a statistically significant deterioration of the repair tissue at 1 year of follow-up. Twelve months after the operation complete filling or hypertrophy was found in 41.6%. Bone-marrow edema and effusion were seen in 41.7% and 25% of the study patients, respectively. We did not find a consistent correlation between the MRI criteria and the clinical results.

DISCUSSION

The present study confirmed the primary role of MRI in the evaluation of cartilage repair. Two MOCART-based scoring systems were used in a longitudinal fashion and allowed a practical and morphological evaluation of the repair tissue. However, the correlation between clinical outcome and MRI findings was poor. Further validation of these scoring systems is mandatory. The promising short-term clinical outcome of the allogenic chondrocytes/alginate beads implantation was not confirmed by the short-term MRI findings.

Longitudinal evaluation of cartilage composition of matrix-associated autologous chondrocyte transplants with 3-T delayed gadolinium-enhanced MRI of cartilage

OBJECTIVE

The purposes of this study were to use delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) to evaluate the zonal distribution of glycosaminoglycans (GAGs) in normal cartilage and repair tissue and to use 3-T MRI to monitor the GAG content in matrix-associated autologous chondrocyte transplants.

SUBJECTS AND METHODS

Fifteen patients who underwent matrix-associated autologous chondrocyte transplantation in the knee joint underwent MRI at baseline and 3-T follow-up MRI 1 year later. Total and zonal changes in longitudinal relaxivity (deltaR1) and relative deltaR1 were calculated for repair tissue and normal hyaline cartilage and compared by use of analysis of variance.

RESULTS

There was a significant difference between the mean deltaR1 of repair tissue and that of reference cartilage at baseline and follow-up (p < 0.001). There was a significant increase in deltaR1 value and a decrease in GAG content from the deep layer to the superficial layer in the reference cartilage and almost no variation and significantly higher values for the repair tissue at both examinations. At 1-year follow-up imaging, there was a 22.7% decrease in deltaR1 value in the deep zone of the transplant.

CONCLUSION

T1 mapping with dGEMRIC at 3 T shows the zonal structure of normal hyaline cartilage, highly reduced zonal variations in repair tissue, and a tendency toward an increase in global and zonal GAG content 1 year after transplantation.

Magnetic resonance imaging for diagnosis and assessment of cartilage defect repairs

Clinical magnetic resonance imaging (MRI) is the method of choice for the non-invasive evaluation of articular cartilage defects and the follow-up of cartilage repair procedures. The use of cartilage-sensitive sequences and a high spatial-resolution technique enables the evaluation of cartilage morphology even in the early stages of disease, as well as assessment of cartilage repair. Sequences that offer high contrast between articular cartilage and adjacent structures, such as the fat-suppressed, 3-dimensional, spoiled gradient-echo sequence and the fast spin-echo sequence, are accurate and reliable for evaluating intrachondral lesions and surface defects of articular cartilage. These sequences can also be performed together in reasonable examination times. In addition to morphology, new MRI techniques provide insight into the biochemical composition of articular cartilage and cartilage repair tissue. These techniques enable the diagnosis of early cartilage degeneration and help to monitor the effect and outcome of various surgical and non-surgical cartilage repair therapies.

Steady-state diffusion imaging for MR in-vivo evaluation of reparative cartilage after matrix-associated autologous chondrocyte transplantation at 3 tesla--preliminary results

OBJECTIVES

To demonstrate the feasibility of time-reversed fast imaging with steady-state precession (FISP) called PSIF for diffusion-weighted imaging of cartilage and cartilage transplants in a clinical study.

MATERIAL AND METHODS

In a cross-sectional study 15 patients underwent MRI using a 3D partially balanced steady-state gradient echo pulse sequence with and without diffusion weighting at two different time points after matrix-associated autologous cartilage transplantation (MACT). Mean diffusion quotients (signal intensity without diffusion-weighting divided by signal intensity with diffusion weighting) within the cartilage transplants were compared to diffusion quotients found in normal cartilage.

RESULTS

The global diffusion quotient found in repair cartilage was significantly higher than diffusion values in normal cartilage (p<0.05). There was a decrease between the earlier and the later time point after surgery.

CONCLUSIONS

In-vivo diffusion-weighted imaging based on the PSIF technique is possible. Our preliminary results show follow-up of cartilage transplant maturation in patients may provide additional information to morphological assessment.

Autologous chondrocyte implantation: Prospective MRI evaluation with clinical correlation

PURPOSE

This study was done to assess the progression of cartilage repair after autologous chondrocyte implantation (ACI) with magnetic resonance imaging (MRI) and to correlate the findings with the clinical outcome.

MATERIALS AND METHODS

Forty-one patients (mean age 30 years) affected by chondral defects of the knee (27 patients) and ankle joint (14 patients) who underwent arthroscopic autologous osteochondral grafting were studied 6 months and 1 year postoperatively with MRI. Cartilage repair after chondrocyte implantation was studied by assessing the degree of defect filling, graft integration, graft signal intensity, integrity of the subchondral lamina and trabecular oedema underneath the graft. MR findings were correlated with clinical data.

RESULTS

Postoperative MRI evaluation at 6 months demonstrated complete filling of the osteochondral defect in 12/41 cases, complete integration in 18/41, mild hyperintensity in 28/41, intact subchondral lamina in 38/41 and trabecular oedema in 11/41. Postoperative MRI evaluation at 1 year demonstrated complete filling of the osteochondral defect in 9/41 patients, complete integration in 22/41, mild hyperintensity in 23/41, intact subchondral lamina in 36/41 and trabecular oedema in 8/41. Filling of the osteochondral defect and incomplete integration, nonintact subchondral lamina, high signal intensity and absence of oedema were found to correlate with worse clinical-functional outcomes.

CONCLUSIONS

MRI shows direct prognostic signs of the clinical outcome of ACI.

Quantitative T2 mapping of matrix-associated autologous chondrocyte transplantation at 3 Tesla: an in vivo cross-sectional study

OBJECTIVES

To evaluate magnetic resonance (MR) T2 mapping for characterization of cartilage repair tissue following matrix-associated autologous cartilage transplantation (MACT).

MATERIALS AND METHODS

Fifteen patients were evaluated following MACT using a 3T MR scanner. Patients were categorized into 2 postoperative intervals: I: 3-13 months, II: 19-42 months. Mean T2 relaxation times calculated from multiple spin-echo sequence were determined in regions of interest (MACT and normal hyaline cartilage) and T2 line profiles through the repair tissue and control sites were acquired.

RESULTS

Mean global T2 values of repair tissue in group I were significantly higher than at control sites (P < 0.05). Repair tissue in group II showed no significant difference to control sites. Repair tissue T2 line profiles normalized over time toward the control sites.

CONCLUSIONS

T2 mapping allows visualization of cartilage repair tissue maturation. Global T2 repair tissue values approach that of control sites after more than 1.5 years, similar behavior is seen in the zonal organization.

Demonstration of the articular cartilage of the canine ulnar trochlear notch using high-field magnetic resonance imaging

The articular cartilage covering the ulnar trochlear notch (UTN) of both elbow joints from 25 adult canine cadavers was demonstrated by the use of high-field magnetic resonance imaging (MRI) with a fat-suppressed, three-dimensional, spoiled gradient echo sequence. The dogs used for this study were divided into five groups: giant, large, mid-sized, small, and chondrodystrophic breeds. The distribution of articular cartilage of the UTN was assessed on MR images. The joints were then opened, and the distribution of the articular cartilage of the UTN was verified. In 29/50 joints, there was good agreement between gross findings of the distribution of the articular cartilage of the UTN and MRI interpretation. Reasons for the poor results in small and chondrodystrophic breeds were decreased thickness of the articular cartilage, small size of the articular surface and of its structural features, and the frequent inability to visualize the joint space.

Rapid 3D-T1ρ mapping of the knee joint at 3.0T with parallel imaging

Three-dimensional spin-lattice relaxation time in the rotating frame (3D-T1rho) with parallel imaging at 3.0T was implemented on a whole-body clinical scanner. A 3D gradient-echo sequence with a self-compensating spin-lock pulse cluster was combined with generalized autocalibrating partially parallel acquisitions (GRAPPA) to acquire T1rho-weighted images. 3D-T1rho maps of an agarose phantom and three healthy subjects were constructed using an eight-channel phased-array coil without parallel imaging and with parallel imaging acceleration factors of 2 and 3, in order to assess the reproducibility of the method. The coefficient of variation (CV) of the median T1rho of the agarose phantom was 0.44%, which shows excellent reproducibility. The reproducibility of in vivo 3D-T1rho maps was also investigated in three healthy subjects. The CV of the median T1rho of the patellar cartilage varied between approximately 1.1% and 4.3%. Similarly, the CV varied between approximately 2.1-5.8%, approximately 1.4-8.7%, and approximately 1.5-4.1% for the biceps femoris and lateral and medial gastrocnemius muscles, respectively. The preliminary results demonstrate that 3D-T1rho maps can be constructed with good reproducibility using parallel imaging. 3D-T1rho with parallel imaging capability is an important clinical tool for reducing both the total acquisition time and RF energy deposition at 3T.

Incidence of chronic knee lesions in long-distance runners based on training level: Findings at MRI

PURPOSE

The purpose of this study was to evaluate the incidence of chronic knee changes in long-distance runners based on the training status, including distance, running frequency, training pace, and running experience.

METHODS

MRI of the knee was performed in 26 non-professional runners 5 days after their last training unit. Lesions of the menisci and cartilage (5-point scale), bone marrow and ligaments (3-point scale), and joint effusion were evaluated. A total score comprising all knee lesions in each runner was evaluated. The incidence of the knee changes was correlated with the training level, gender, and age of the runners.

RESULTS

Grade 1 lesions of the menisci were found in six runners with a high training level, and in only four runners with a low training level. Grade 1 cartilage lesions were found in three high-trained runners and in one low-trained runner, and grade 2 lesions were found in one high-trained runner and in two low-trained runners, respectively. Grade 1 anterior cruciate ligament lesions were seen in three runners with a high- and in two runners with a low-training level. Runners with a higher training level showed a statistically significant higher score for all chronic knee lesions than those with a lower training level (p<0.05).

CONCLUSIONS

MRI findings indicate that a higher training level in long-distance runners is a risk factor for chronic knee lesions.

Does marathon running cause acute lesions of the knee? Evaluation with magnetic resonance imaging

An investigation was conducted into whether running a marathon causes acute alterations in menisci, cartilage, bone marrow, ligaments, or joint effusions, which could be evaluated by magnetic resonance imaging (MRI). Twenty-two non-professional marathon runners underwent MRI of the knee before and immediately after running a marathon. Lesions of menisci and cartilage (five-point scale), bone marrow, ligaments (three-point scale), joint effusion, and additional findings were evaluated and a total score was assessed. Before the marathon, grade 1 lesions of the menisci were found in eight runners, and grade 2 lesions in five runners. After the marathon, an upgrading from a meniscal lesion grade 1 to grade 2 was observed in one runner. Before the marathon, grade 1 cartilage lesions were found in three runners, and grade 2 lesions in one runner, all of which remained unchanged after the marathon. Before and after the marathon, unchanged bone marrow edema was present in three runners and unchanged anterior cruciate ligament lesions (grade 1) were seen in two runners. Joint effusions were present in 13 runners in the pre-run scans, slightly increased in four runners after the marathon, and newly occurred in one runner after the marathon. A total score comprising all knee lesions in each runner showed an increase after the marathon in two runners, whereas no runner showed an improvement of the radiological findings (Wilcoxon signed-rank test, P>0.05). The evaluation of lesions of the knee with MRI shows that marathon running does not cause severe, acute lesions of cartilage, ligaments, or bone marrow of the knee in well-trained runners. Only subtle changes, such as joint effusions or increased intrameniscal signal alterations, were imaged after running a marathon.

3D-T1ρ quantitation of patellar cartilage at 3.0T

PURPOSE

To demonstrate the feasibility of three-dimensional (3D) T(1rho)-weighted imaging of human knee joint at 3.0T without exceeding the specific absorption rate (SAR) limits and the measurement of the baseline T(1rho) values of patellar cartilage and several muscles at the knee joint.

MATERIALS AND METHODS

3D gradient-echo sequence with a self-compensating spin-lock pulse cluster of 250 Hz power was used to acquire 3D-T(1rho)-weighted images of the knee joint of five healthy subjects. Global and regional analysis of patellar cartilage T(1rho) were performed. Furthermore, T(1rho) of several periarticular muscles were analyzed.

RESULTS

The global average T(1rho) value of the patellar cartilage varied from 39 to 43 msec. The regional average T(1rho) values varied from 38 to 42 msec, and from 42 to 44 msec for medial and lateral facets, respectively. In vivo reproducibility of average T(1rho) of patellar cartilage was found to be 5% (coefficient of variation). Similarly, the global average T(1rho) values for biceps femoris, lateral gastrocnemius, medial gastrocnemius, and sartorius varied between 31-46, 29-49, 35-48, and 32-50 msec, respectively.

CONCLUSION

We demonstrated the feasibility of 3D-T(1rho)-weighted imaging of the knee joint at 3.0T without exceeding SAR limits.

4 T MRI of chondrocalcinosis in combination with three-dimensional CT, radiography, and arthroscopy: a report of three cases

OBJECTIVE

To describe 4 T MRI techniques in imaging chondrocalcinosis within the knee and examine the results together with those demonstrated using three-dimensional (3D) computed tomography, conventional radiography, and arthroscopy.

DESIGN AND PATIENTS

From a larger clinical imaging study of early osteoarthritis, knee arthroscopy patients were imaged using high-field MRI and high-resolution 3D CT prior to their surgery. Retrospective review of the imaging data diagnosed three patients with chondrocalcinosis. Fat-suppressed 3D spoiled gradient (3D SPGR) and two-dimensional fat-suppressed fast spin echo (FSE) imaging was performed at 4 T. The MR images, multi-planar reformatted CT (MPR-CT) and maximum intensity projection CT (MIP-CT) images, and radiographs were examined by a musculoskeletal radiologist for the presence and location of chondrocalcinosis. The findings from arthroscopy were also included.

RESULTS

MRI showed 16 sites of punctate hypointense regions from 18 articular surfaces and five of six menisci with similar signal characteristics. Both meniscal chondrocalcinosis and meniscal tears were clearly visible using the 3D SPGR sequence. Only three sites were demonstrated to have calcification using MPR-CT and MIP-CT revealed an additional three. In articular cartilage surfaces showing surface disruption, arthroscopy demonstrated 11 sites with crystal deposition. Arthroscopy also revealed five menisci with calcification present.

CONCLUSION

Our preliminary findings suggest that imaging chondrocalcinosis using spoiled gradient 4 T MRI is superior and complementary to the other imaging modalities in the detection of crystal deposition in both articular cartilage and menisci.

Magnetic resonance observation of cartilage repair tissue (MOCART) for the evaluation of autologous chondrocyte transplantation: determination of interobserver variability and correlation to clinical outcome after 2 years

In an observational study, the validity and reliability of magnetic resonance imaging (MRI) for the assessment of autologous chondrocyte transplantation (ACT) in the knee joint was determined. Two years after implantation, high-resolution MRI was used to analyze the repair tissue with nine pertinent variables. A complete filling of the defect was found in 61.5%, and a complete integration of the border zone to the adjacent cartilage in 76.9%. An intact subchondral lamina was present in 84.6% and an intact subchondral bone was present in 61.5%. Isointense signal intensities of the repair tissue compared to the adjacent native cartilage were seen in 92.3%. To evaluate interobserver variability, a reliability analysis with the determination of the intraclass correlation coefficient (ICC) was calculated. An "almost perfect" agreement, with an ICC value >0.81, was calculated in 8 of 9 variables. The clinical outcome after 2 years showed the visual analog score (VAS) at 2.62 (S.D. +/-0.65). The values for the knee injury and osteoarthritis outcome score (KOOS) subgroups were 68.29 (+/-23.90) for pain, 62.09 (+/-14.62) for symptoms, 75.45 (+/-21.91) for ADL function, 52.69 (+/-28.77) for sport and 70.19 (+/-22.41) for knee-related quality of life. The clinical scores were correlated with the MRI variables. A statistically significant correlation was found for the variables "filling of the defect," "structure of the repair tissue," "changes in the subchondral bone," and "signal intensities of the repair issue". High resolution MRI and well-defined MRI variables are a reliable, reproducible and accurate tool for assessing cartilage repair tissue.

Cartilage MR imaging at 3.0 versus that at 1.5 T: preliminary results in a porcine model

PURPOSE

To compare 1.5- and 3.0-T magnetic resonance (MR) images of porcine knee specimens containing artificial cartilage lesions in terms of accuracy of lesion depiction, image quality, and signal-to-noise ratio (SNR).

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act-compliant study had institutional review board approval, and informed consent was obtained from the human volunteers. Two fat-saturated cartilage MR imaging sequences (an intermediate-weighted fast spin-echo [SE] sequence and a spoiled gradient-echo [GRE] sequence) were optimized for imaging at 3.0 T in two human volunteers and then used to image 10 porcine knees in which 29 artificial cartilage lesions had been created. Corresponding sequences were used at 1.5 T for all specimens. Images were assessed by two radiologists in consensus, and diagnostic performance in lesion depiction was determined by using macroscopic findings in specimen slices as a reference standard. SNRs were also calculated. For statistical analysis, the McNemar test of discordant pairs was used with a level of significance of P < .05.

RESULTS

The best diagnostic performance for both the intermediate-weighted fast SE and the spoiled GRE sequences was achieved at 3.0 T. With use of corresponding fat-saturated intermediate-weighted fast SE sequences with an identical acquisition time (9 minutes 44 seconds), 26 (90%) of 29 lesions were detected at 3.0 T, while 18 (62%) were detected at 1.5 T. With use of fat-saturated spoiled GRE sequences, 24 (83%) of 29 lesions were detected at 3.0 T (acquisition time, 8 minutes 48 seconds), and 23 (79%) lesions were detected at 1.5 T (acquisition time, 11 minutes 14 seconds). The rate of correct lesion grade assessment was 65% (17 of 26 lesions) at 3.0 T and 61% (11 of 18 lesions) at 1.5 T with the intermediate-weighted fast SE sequences and 83% (20 of 24 lesions) at 3.0 T and 70% (16 of 23 lesions) at 1.5 T with the spoiled GRE sequences. Both subjective evaluation of image quality and SNR values were significantly higher at 3.0 T (P < .05).

CONCLUSION

In this animal model, MR imaging at 3.0 T increased the accuracy of cartilage lesion assessment when compared with imaging at 1.5 T. Image quality and SNR were highest at 3.0 T.

Computer-aided quantification of focal cartilage lesions using MRI: accuracy and initial arthroscopic comparison

OBJECTIVE

The purpose of the study was to validate a Gradient Peak Method (GPM) by evaluating its accuracy and consistency at different magnetic field strengths. The GPM using magnetic resonance imaging (MRI) was previously proposed to quantitatively assess the morphology of focal cartilage lesions, and its feasibility was demonstrated.

METHODS

GPM quantifies the morphologic properties of cartilage lesions based on their three-dimensional geometry. Twenty-two conical and cylindrical lesions were surgically created on fresh porcine knees, and the results obtained by GPM were compared with manually measured lesion dimensions. Another 15 focal lesions of various shapes were created and scanned, and the quantification results were compared at 1.5 Tesla and 3 Tesla. Additionally, cartilage lesions in three patients were scanned, quantified by GPM, and compared with arthroscopic visualization and measurements.

RESULTS

The average absolute errors of GPM (depth: < or =0.4mm; diameter: < or =1.4mm) were within twice the in-plane resolution in depth estimates and within the slice thickness in diameter estimates. Analysis also suggested that the quantifications of GPM using 1.5 Tesla and 3 Tesla data were not statistically different. Moreover, the GPM results were shown to be consistent with the lesion measurements obtained arthroscopically.

CONCLUSIONS

The GPM using MRI provides estimates of lesion thickness, depth, diameter, and area. With this validation, the method can be potentially used as an auxiliary tool to help radiologists and physicians assess cartilage lesions quantitatively and monitor disease progression.

Definition of pertinent parameters for the evaluation of articular cartilage repair tissue with high-resolution magnetic resonance imaging

To evaluate articular cartilage repair tissue after biological cartilage repair, we propose a new technique of non-invasive, high-resolution magnetic resonance imaging (MRI) and define a new classification system. For the definition of pertinent variables the repair tissue of 45 patients treated with three different techniques for cartilage repair (microfracture, autologous osteochondral transplantation, and autologous chondrocyte transplantation) was analyzed 6 and 12 months after the procedure. High-resolution imaging was obtained with a surface phased array coil placed over the knee compartment of interest and adapted sequences were used on a 1 T MRI scanner. The analysis of the repair tissue included the definition and rating of nine pertinent variables: the degree of filling of the defect, the integration to the border zone, the description of the surface and structure, the signal intensity, the status of the subchondral lamina and subchondral bone, the appearance of adhesions and the presence of synovitis. High-resolution MRI, using a surface phased array coil and specific sequences, can be used on every standard 1 or 1.5 T MRI scanner according to the in-house standard protocols for knee imaging in patients who have had cartilage repair procedures without substantially prolonging the total imaging time. The new classification and grading system allows a subtle description and suitable assessment of the articular cartilage repair tissue.

Comparison of multislice CT arthrography and MR arthrography for the detection of articular cartilage lesions of the elbow

The objective of this study was to compare the value of multislice CT arthrography and MR arthrography in the assessment of cartilage lesions of the elbow joint. Twenty-six cadaveric elbow specimens were examined with the use of CT arthrography and MR arthrography prior to joint exploration and macroscopic inspection of articular cartilage. Findings at CT and MR arthrography were compared with macroscopic assessments in 104 cartilage areas. At macroscopic inspection, 45 cartilage lesions (six grade 2 lesions, 25 grade 3 lesions, 14 grade 4 lesions) and 59 areas of normal articular cartilage were observed. With macroscopic assessment as the gold standard CT and MR arthrography showed an overall sensitivity/specificity of 80/93% and 78/95% for the detection of cartilage lesions, respectively. Only two of six grade 2 lesions were detected by CT and MR arthrography. For the diagnosis of grade 3 and 4 lesions, the sensitivity/specificity was 87/94% with CT arthrography, and 85/95% with MR arthrography. In an experimental setting multislice CT arthrography and MR arthrography showed a similar performance in the detection of cartilage lesions. Both methods indicated limited value in the diagnosis of grade 2 articular cartilage lesions.

Magnetic resonance imaging of cartilage and cartilage repair

Magnetic resonance (MR) imaging of articular cartilage has assumed increased importance because of the prevalence of cartilage injury and degeneration, as well as the development of new surgical and pharmacological techniques to treat damaged cartilage. This article will review relevant aspects of the structure and biochemistry of cartilage that are important for understanding MR imaging of cartilage, describe optimal MR pulse sequences for its evaluation, and review the role of experimental quantitative MR techniques. These MR aspects are applied to clinical scenarios, including traumatic chondral injury, osteoarthritis, inflammatory arthritis, and cartilage repair procedures.

Early changes in experimental osteoarthritis using the Pond-Nuki dog model: technical procedure and initial results of in vivo MR imaging

The purpose of this study was to prove the feasibility of combining in vivo MR imaging with the Pond-Nuki animal model for the evaluation of osteoarthritis. In an experimental study, 24 beagle dogs underwent transection of the anterior cruciate ligament of the left leg (modified Pond-Nuki model). The dogs were randomly assigned into four groups and examined by MRI after 6, 12, 24 and 48 weeks. MR imaging of both knees was performed under general anesthesia with the contralateral joint serving as control. In group 1 (6 weeks postoperatively), the first sign detected on MRI was subchondral bone marrow edema in the posteromedial tibia. After 12 weeks, erosion of the posteromedial tibial cartilage could be observed, followed by meniscus degeneration and osteophytosis after 24 and 48 weeks. The contralateral knee joint showed transient joint effusion, but no significant signs of internal derangement (P<0.001). By combining in vivo MR imaging with the Pond-Nuki model, it is possible to detect early signs of osteoarthritis. The first sign was posteromedial subchondral bone marrow edema in the tibia followed by progressive cartilage degeneration and joint derangement. The in vivo model therefore seems to be suitable for longitudinal studies or monitoring the therapeutic effects of osteoarthritis.

Patellar articular cartilage lesions: in vitro MR imaging evaluation after placement in gadopentetate dimeglumine solution

PURPOSE

To evaluate T1-weighted magnetic resonance (MR) imaging after diffusion of gadopentetate dimeglumine for visualization of articular cartilage lesions.

MATERIALS AND METHODS

MR imaging was performed in eight human cadaveric patella specimens immediately and 4 hours after placement into a vessel filled with gadopentetate dimeglumine solution (2.5 mmol/L). T1-weighted spin-echo and inversion-recovery turbo spin-echo MR sequences with nulled cartilage signal (inversion time of 300 msec) were used. In a total of 128 articular cartilage areas, MR imaging findings were compared with macroscopic and histopathologic findings. Pathologic evaluation was performed by one musculoskeletal pathologist. With knowledge of pathologic observations, MR images were analyzed by one musculoskeletal radiologist with regard to intrinsic signal intensity characteristics and surface abnormalities of articular cartilage.

RESULTS

Histopathologic findings demonstrated 67 areas of normal articular cartilage and 66 cartilage lesions (grade 1, n = 19; grade 2, n = 15; grade 3, n = 26; grade 4, n = 6). All grade 3 and 4 lesions could be identified on MR images obtained immediately after submersion and after 4 hours. Ninety-four percent of grade 1 and 2 lesions were identified as areas of predominantly decreased contrast enhancement on delayed MR images obtained with both sequences. MR images obtained immediately after submersion demonstrated abnormal signal intensity in only 9% and 12% of grade 1 and 2 lesions, respectively.

CONCLUSION

T1-weighted MR images obtained in vitro after gadopentetate dimeglumine diffusion allow demonstration of articular cartilage surface lesions and early stages of cartilage degradation.

Inter-rater and intra-rater reliability of subchondral bone and cartilage thickness measurement from MRI☆

MRI is often used to visualize and quantify the articular cartilage layer of load bearing joints affected by degenerative diseases, such as osteoarthritis (OA). Although the role played by the subchondral bone in the etiology and/or progression of OA may be important, the ability to visualize and quantify subchondral bone with MRI has received little attention. In this report we examined the inter-rater and intra-rater reliability of subchondral bone and cartilage thickness measurements from MR images of cadaver femoral head specimens. A 3D-SPGR pulse sequence tuned to eliminate chemical shift artifact through phase cancellation was used to image the specimens. Three raters manually segmented four specimens on two different occasions. Subchondral bone and cartilage thickness measurements were calculated from the segmented images. Inter-rater and intra-rater reliabilities were very high (>.98) for both cartilage and subchondral bone thickness measurements. We conclude that subchondral bone thickness can be measured as reliably as cartilage thickness from MR images.

Relaxivity and diffusion of gadolinium agents in cartilage

Prior work indicates that the distribution of Gd(DTPA)(2-) (as measured by T(1)) is a good surrogate measure of the distribution of gycosaminoglycan (GAG) in cartilage. In addition to the measured T(1) in the presence of Gd(DTPA)(2-), the precision of the measurement of Gd(DTPA)(2-) concentration depends on the T(1) without Gd(DTPA)(2-) (T(o)(1)), and the relaxivity (r) of Gd(DTPA)(2-) in cartilage, parameters that are influenced by cartilage composition. These parameters were measured in native and GAG-depleted cartilage in order to estimate the bounds on the values one might expect for cartilage in arbitrary states of degeneration. The range of T(o)(1) was 0.3 sec; the range of r was 0.6 (mM*s)(-1) at 8.5 T and 1.4 (mM*s)(-1) at 2 T. These data suggest that Gd(DTPA)(2-) will be underestimated (and GAG overestimated) if the values for T(o)(1) and r are assumed to be those of native cartilage. (For example, in a severe case a 90% loss of GAG would be underestimated as a 70% loss.) Gd(HPDO3A) was investigated as a nonionic "control agent" and found to have relaxivity and diffusion properties that were comparable to Gd(DTPA)(2-) (r(Gd(HPDO3A))/r(Gd(DTPA)) approximately 1; D(Gd(HPDO3A))/D(Gd(DTPA)) approximately 0.85). Since Gd(HPDO3A) distributes uniformly through cartilage (independent of GAG), the distribution of T(1) with Gd(HPDO3A) can be used as a surrogate measure of variations in T(o)(1) and r, if present. From the perspective of transport, if Gd(HPDO3A) has fully penetrated the cartilage, Gd(DTPA)(2-) would have in the same time frame. Therefore, the data confirm the efficacy of using Gd(HPDO3A) as a "control agent" for dGEMRIC.

Magnetic resonance imaging of relative glycosaminoglycan distribution in patients with autologous chondrocyte transplants

RATIONALE AND OBJECTIVES

Autologous chondrocyte transplantation (ACT) is a potential treatment for full-thickness chondral lesions in the knee. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) has recently been developed as a sensitive and specific measure of cartilage glycosaminoglycans (GAGs). Under the conditions of dGEMRIC, T1 is directly related to the GAG concentration. Our aim for this study was to demonstrate the potential of dGEMRIC to evaluate ACT implants.

METHODS

Eleven ACT implants were studied 2 to 24 months postoperatively by dGEMRIC. T1 values from three regions of interest were obtained to examine GAG content (1) in the implant, (2) in native cartilage adjacent to the implant, and (3) in native cartilage further removed from the implant (as "control").

RESULTS

One implant failed and therefore was not included. Four of the implants were studied between 2 and 6 months postoperatively and showed low T1 (GAG), less than 80% of the control native cartilage. Five of the six implants studied between 12 and 24 months postoperativley showed T1 (GAG) comparable to (>80%) of control. One 18-month graft showed low T1 comparable to the surrounding native cartilage, with normal GAG seen in cartilage far from the graft site. The GAG index (T1 values of the graft normalized to control) from the group of implants 6 months or less was 59% +/- 5% of control, whereas those at 12 to 24 months were 91% +/- 18% of control. The two groups were statistically different with a P value of 0.005.

CONCLUSIONS

The GAG level in grafts that were implanted for less than 12 months appeared to be lower than that in the remote cartilage. At 12 months or greater, the grafts in this study had GAG levels that were comparable to both the adjacent and remote cartilage. This preliminary study of ACT implants has shown that it is feasible to apply the dGEMRIC technique in patients with ACT as a way to obtain information related to the composition of grafts. These results provide motivation and the pilot data with which to design further clinical studies.

MR imaging of changes of the growth plate after partial physeal removal and fat graft interposition in rabbits

RATIONALE AND OBJECTIVES

The most important complication of skeletal injuries involving the growth plate is growth disturbance. The purpose of this study was to evaluate MR features of growth plate modification after fat graft interposition in growth plate injury and to correlate these findings with pathological findings.

METHODS

A growth plate injury model was used in 12 skeletally immature rabbits. A longitudinal drill hole 5 mm in diameter was created in the central part of the growth plate in the distal femur, bilaterally. One side was filled with autologous fat, and the contralateral defect was left empty as a control. Magnetic resonance imaging was obtained 1, 3, and 6 months after surgery, and routine histological study was performed. The authors evaluated sequential changes in MR images and the histological basis of MR findings.

RESULTS

In grafted femur, the signal intensity of the grafted area was lower than that of the surrounding bone on T2-weighted images at 1 month. The growth plate defect at 3 to 6 months was modified and had a proximally tapering appearance. The ratio of the growth plate defect was smaller in the grafted femur than in the control femur after surgery. Histologically, the fat-grafted area was replaced by fibrous connective tissue. In the control femur, a bony bridge was rectangular in the longitudinal direction and showed isosignal intensity with a rim of low signal intensity on T1-weighted imaging. Histologically, the defect was filled with mature fatty marrow with new bone formation in the control femur.

CONCLUSIONS

The proximally pointing appearance and the low signal intensity of the grafted area on MR suggested fibrous degeneration of grafted fat that prevented solid bony bridge formation in experimentally induced growth plate injury.

MRI techniques in early stages of cartilage disease

Cartilage degenerative diseases affect millions of people. Our understanding of these diseases and our ability to establish efficacious treatment strategies have been confounded by the difficulty of nondestructively evaluating the state of cartilage. Imaging strategies that allow visualization of cartilage integrity would revolutionize the field by allowing us to visualize early stages of degeneration and thus to evaluate predisposing factors for cartilage disease and changes resulting from interventions (eg, therapies) in culture studies, tissue-engineered systems, animal models, and in vivo in humans. Here we briefly review current state-of-the-art MRI strategies relevant to understanding and following treatment in early cartilage degeneration. We review MRI as applied to the assessment of the whole joint, of cartilage as a whole (as an organ), of cartilage tissue, and of cartilage molecular composition and structure. Each of these levels is amenable to assessment by MRI and offers different information that, in the long run, will serve as an important element of cartilage imaging.

Anatomy, biochemistry, and physiology of articular cartilage

Articular cartilage serves as a load-bearing elastic material that is responsible for the frictionless movement of the surfaces of articulating joints. Its ability to undergo reversible deformation depends on its structural organization, including the specific arrangement of the matrix macromolecules and the chondrocytes. Interactions between the matrix and chondrocytes are responsible for the biological and mechanical properties of articular cartilage and enable it to respond by effecting a balance between anabolism and catabolism as well as continual internal remodeling. Age-related changes in the function of chondrocytes may contribute to the initiation and progression of osteoarthritis.

Physicochemical properties of normal articular cartilage and its MR appearance

Basic physical and physicochemical properties of articular cartilage are correlated with the MR parameters of this tissue. From these parameters, the typical appearance of cartilage in MR images is deduced. Some practical implications for clinical utilization of MRI of articular cartilage are summarized.

Magic-angle effect in magnetic resonance imaging of articular cartilage: a review

RATIONALE AND OBJECTIVES

The laminar appearance of articular cartilage in magnetic resonance (MR) images has been a source of confusion, especially concerning the number, intensity, thickness, and origin of the layers. The laminar appearance is associated with the magic-angle effect in the MR imaging (MRI) of articular cartilage.

METHODS

This article introduces the topic with background information about cartilage and the magic-angle effect and then reviews the literature about the magic-angle effect. The review concludes with a brief discussion of the future directions of study and the potential clinical relevance of the laminae in MR images of articular cartilage.

CONCLUSIONS

The magic-angle effect is commonly seen in MR images of several tissues. The direct cause of the laminar appearance of articular cartilage is the T2 relaxation anisotropy in the tissue, which is closely linked to the structure of the collagen fibers, their orientation in the magnetic field, and the water-proteoglycan interaction that amplifies the prevailing orientation of the collagen fiber network. The laminar appearance of cartilage has an intrinsic spatial heterogeneity over the two-dimensional joint surface, which leads to inconsistencies in the reported total number of cartilage laminae and the laminar patterns observable in MRI, depending on where the sample was taken. Two additional thin, low-intensity laminae may also be visible at the boundaries of the cartilage with fluid and with bone; whether these boundary laminae are identified and counted with the others may introduce inconsistency in the results reported by various researchers.