Biochemical MRI predicts hip osteoarthritis in an experimental ovine femoroacetabular impingement model.

BACKGROUND: Cam-type femoroacetabular impingement (FAI) resulting from an abnormal nonspherical femoral head shape leads to chondrolabral damage and is considered a cause of early osteoarthritis. A previously developed experimental ovine FAI model induces a cam-type impingement that results in localized chondrolabral damage, replicating the patterns found in the human hip. Biochemical MRI modalities such as T2 and T2* may allow for evaluation of the cartilage biochemistry long before cartilage loss occurs and, for that reason, may be a worthwhile avenue of inquiry. QUESTIONS/PURPOSES: We asked: (1) Does the histological grading of degenerated cartilage correlate with T2 or T2* values in this ovine FAI model? (2) How accurately can zones of degenerated cartilage be predicted with T2 or T2* MRI in this model? METHODS: A cam-type FAI was induced in eight Swiss alpine sheep by performing a closing wedge intertrochanteric varus osteotomy. After ambulation of 10 to 14 weeks, the sheep were euthanized and a 3-T MRI of the hip was performed. T2 and T2* values were measured at six locations on the acetabulum and compared with the histological damage pattern using the Mankin score. This is an established histological scoring system to quantify cartilage degeneration. Both T2 and T2* values are determined by cartilage water content and its collagen fiber network. Of those, the T2* mapping is a more modern sequence with technical advantages (eg, shorter acquisition time). Correlation of the Mankin score and the T2 and T2* values, respectively, was evaluated using the Spearman's rank correlation coefficient. We used a hierarchical cluster analysis to calculate the positive and negative predictive values of T2 and T2* to predict advanced cartilage degeneration (Mankin ≥ 3). RESULTS: We found a negative correlation between the Mankin score and both the T2 (p < 0.001, r = -0.79) and T2* values (p < 0.001, r = -0.90). For the T2 MRI technique, we found a positive predictive value of 100% (95% confidence interval [CI], 79%-100%) and a negative predictive value of 84% (95% CI, 67%-95%). For the T2* technique, we found a positive predictive value of 100% (95% CI, 79%-100%) and a negative predictive value of 94% (95% CI, 79%-99%). CONCLUSIONS: T2 and T2* MRI modalities can reliably detect early cartilage degeneration in the experimental ovine FAI model. CLINICAL RELEVANCE: T2 and T2* MRI modalities have the potential to allow for monitoring the natural course of osteoarthrosis noninvasively and to evaluate the results of surgical treatments targeted to joint preservation.

Direct comparison of intra-articular versus intravenous delayed gadolinium-enhanced MRI of hip joint cartilage.

PURPOSE: To investigate the potential of delayed gadolinium-enhanced magnetic resonance imaging in cartilage (dGEMRIC) after intra-articular (ia) contrast agent administration at 3 Tesla (T), a paired study comparing intravenous (iv) dGEMRIC (standard) with ia-dGEMRIC was performed. MATERIALS AND METHODS: Thirty-five symptomatic patients with suspected cartilage damage underwent ia- and iv-dGEMRIC. MRI was performed with a 3T system wherein the interval between both measurements was 2 weeks. For iv-dGEMRIC, FDA approved Gd-DOTA(-) was injected intravenously 45 min before the MRI scan. For ia-dGEMRIC, 10-20 mL of a 2 mM solution of Gd- DOTA(-) was injected under fluoroscopic guidance 30 min before the MRI scan. RESULTS: Both ia- and iv-dGEMRIC demonstrated the typical T1Gd pattern in hip joint cartilage with increasing values toward the superior regions in acetabular cartilage reflecting the higher glycosaminoglycan (GAG) content in the main weight-bearing area. Correlation analysis revealed a moderate correlation between both techniques (r = 0.439, P-value < 0.001), whereas the T1Gd values for iv-dGEMRIC were significantly higher than those for ia-dGEMRIC. This corresponds with the Bland-Altman plot analysis, which revealed a systemic bias (higher T1Gd values after iv gadolinium application) of ∼70 ms. CONCLUSION: Ia-dGEMRIC was able to reveal the characteristic T1Gd pattern in hip joint cartilage confirming the sensitivity of ia-dGEMRIC for GAG. In addition, there was a significant correlation between iv-dGEMRIC and ia-dGEMRIC. However, the T1Gd values after ia contrast media application were significantly lower than those after iv application that has to be considered for future studies.

Is the damage of cartilage a global or localized phenomenon in hip dysplasia, measured by dGEMRIC?

BACKGROUND: The mechanism of damage in osteoarthritis is believed to be multifactorial where mechanical and biological factors are important in its initiation and progression. Hip dysplasia is a classic model of increased mechanical loading on cartilage attributable to insufficient acetabular coverage that leads to osteoarthritis. If the damage is all attributable to direct mechanical damage then one initially would expect only local, not global changes. QUESTIONS/PURPOSES: We hypothesize that in hip dysplasia although the elevated cumulative contact stresses are localized, the damage to cartilage is biologically mediated, therefore, biochemical changes will be global. METHODS: Thirty-two patients with symptomatic hip dysplasia were scanned using a 1.5-T MRI scanner. We used a high-resolution three-dimensional dGEMRIC technique to characterize the distribution of cartilage damage in dysplastic hips. High-resolution isotropic acquisition was reformatted around the femoral neck axis and the dGEMRIC index was calculated separately for femoral and acetabular cartilages. Joint space widths also were evaluated in each reformatted slice. Each hip was characterized by the presence or absence of joint migration and by Tönnis grade. RESULTS: The global dGEMRIC index correlated with the dGEMRIC indices of individual regions with the highest correlations occurring in the anterosuperior to posterosuperior regions. The corresponding correlations for joint space width were uniformly lower, suggesting that tissue loss is a more local phenomenon. Higher Tönnis grades and hips with joint migration were associated with lower dGEMRIC indices. CONCLUSIONS: The dGEMRIC index shows a global decrease, whereas tissue loss is more localized. This suggests that hip osteoarthritis in acetabular dysplasia is a biologically mediated event that affects the entire joint.

Quantitative analysis of lumbar intervertebral disc abnormalities at 3.0 Tesla: value of T(2) texture features and geometric parameters.

T(2) relaxation time mapping provides information about the biochemical status of intervertebral discs. The present study aimed to determine whether texture features extracted from T(2) maps or geometric parameters are sensitive to the presence of abnormalities at the posterior aspect of lumbar intervertebral discs, i.e. bulging and herniation. Thirty-one patients (21 women and 10 men; age range 18-51 years) with low back pain were enrolled. MRI of the lumbar spine at 3.0 Tesla included morphological T(1) - and T(2) -weighted fast spin-echo sequences, and multi-echo spin-echo sequences that were used to construct T(2) maps. On morphological MRI, discs were visually graded into 'normal', 'bulging' or 'herniation'. On T(2) maps, texture analysis (based on the co-occurrence matrix and wavelet transform) and geometry analysis of the discs were performed. The three T(2) texture features and geometric parameters best-suited for distinguishing between normal discs and discs with bulging or herniation were determined using Fisher coefficients. Statistical analysis comprised ANCOVA and post hoc t-tests. Eighty-two discs were classified as 'normal', 49 as 'bulging' and 20 showed 'herniation.' The T(2) texture features Entropy and Difference Variance, and all three pre-selected geometric parameters differed significantly between normal and bulging, normal and herniated, and bulging and herniated discs (p < 0.05). These findings suggest that T(2) texture features and geometric parameters are sensitive to the presence of abnormalities at the posterior aspect of lumbar intervertebral discs, and may thus be useful as quantitative biomarkers that predict disease.

Axial T2 mapping in intervertebral discs: a new technique for assessment of intervertebral disc degeneration.

OBJECTIVES: To demonstrate the potential benefits of biochemical axial T2 mapping of intervertebral discs (IVDs) regarding the detection and grading of early stages of degenerative disc disease using 1.5-Tesla magnetic resonance imaging (MRI) in a clinical setting. METHODS: Ninety-three patients suffering from lumbar spine problems were examined using standard MRI protocols including an axial T2 mapping protocol. All discs were classified morphologically and grouped as "healthy" or "abnormal". Differences between groups were analysed regarding to the specific T2 pattern at different regions of interest (ROIs). RESULTS: Healthy intervertebral discs revealed a distinct cross-sectional T2 value profile: T2 values were significantly lower in the annulus fibrosus compared with the nucleus pulposus (P = 0.01). In abnormal IVDs, T2 values were significantly lower, especially towards the centre of the disc representing the expected decreased water content of the nucleus (P = 0.01). In herniated discs, ROIs within the nucleus pulposus and ROIs covering the annulus fibrosus showed decreased T2 values. CONCLUSIONS: Axial T2 mapping is effective to detect early stages of degenerative disc disease. There is a potential benefit of axial T2 mapping as a diagnostic tool, allowing the quantitative assessment of intervertebral disc degeneration.

Magnetic resonance imaging of the knee at 3 and 7 tesla: a comparison using dedicated multi-channel coils and optimised 2D and 3D protocols.

OBJECTIVES: To show the feasibility and possible superiority of two 7 Tesla knee protocols ("7 T high resolution" and "7 T quick") using a new 28-channel knee coil compared to an optimised 3 T knee protocol using an 8-channel knee coil. METHODS: The study was approved by the ethics committee. Both 3 T and 7 T MRI of the knee were performed in 10 healthy volunteers (29.6 ± 7.9 years), with two 2D sequences (PD-TSE and T1-SE) and three isotropic 3D sequences (TRUFI, FLASH and PD-TSE SPACE). Quantitative contrast-to-noise ratio (CNR) and qualitative evaluations were performed by different readers, and intra- and inter-rater agreement was assessed. RESULTS: The signal-to-noise ratio (SNR) as well as the CNR values for cartilage-bone, cartilage-fluid, cartilage-menisci and menisci-fluid were, in most cases, higher at 7 T compared to 3 T, and the 7 T quick measurement was slightly superior compared to the 7 T high-resolution measurement. The results of the subjective qualitative analysis were higher for the 7 T measurements compared to the 3 T measurements. Inter- and intra-observer reliability was high (0.884-0.999). CONCLUSIONS: Through higher field strength and an optimal coil, resolution at 7 T can be increased and acquisition time can be reduced, with superior quantitative and comparable qualitative results compared to 3 T.

Quantitative mapping of T2 using partial spoiling.

Fast quantitative MRI has become an important tool for biochemical characterization of tissue beyond conventional T1, T2, and T2*-weighted imaging. As a result, steady-state free precession (SSFP) techniques have attracted increased interest, and several methods have been developed for rapid quantification of relaxation times using steady-state free precession. In this work, a new and fast approach for T2 mapping is introduced based on partial RF spoiling of nonbalanced steady-state free precession. The new T2 mapping technique is evaluated and optimized from simulations, and in vivo results are presented for human brain at 1.5 T and for human articular cartilage at 3.0 T. The range of T2 for gray and white matter was from 60 msec (for the corpus callosum) to 100 msec (for cortical gray matter). For cartilage, spatial variation in T2 was observed between deep (34 msec) and superficial (48 msec) layers, as well as between tibial (33 msec), femoral, (54 msec) and patellar (43 msec) cartilage. Excellent correspondence between T2 values derived from partially spoiled SSFP scans and the ones found with a reference multicontrast spin-echo technique is observed, corroborating the accuracy of the new method for proper T2 mapping. Finally, the feasibility of a fast high-resolution quantitative partially spoiled SSFP T2 scan is demonstrated at 7.0 T for human patellar cartilage.

Gadolinium diethylenetriaminepentaacetate enhancement kinetics in the menisci of asymptomatic subjects: a first step towards a dedicated dGEMRIC (delayed gadolinium-enhanced MRI of cartilage)-like protocol for biochemical imaging of the menisci.

It was our aim to investigate the gadolinium diethylenetriaminepentaacetate (Gd-DTPA(2-) ) enhancement kinetics in the menisci of the knee joint over a prolonged period of time. Six asymptomatic volunteers (four men and two women; mean age, 25 ± 2.4 years) were enrolled. Sagittal, T(1) -weighted, spin-echo MR sequences of the right knee joint were obtained at 3 T. Imaging was performed before (baseline), 1 h after and in half-hour intervals up to 9 h after the intravenous administration of 0.2 mmol/kg of Gd-DTPA(2-) . To measure the rates of contrast enhancement relative to the baseline, regions of interest that covered the anterior and posterior horns of the medial and lateral meniscus were defined on each of two adjacent sections, and enhancement curves were constructed. An enhancement peak between 2.5 and 4.5 h after Gd-DTPA(2-) administration was observed, and analysis of variance also revealed no significant difference (p=0.94), in terms of enhancement, within this time interval. Pair-wise, post hoc testing also revealed no significant differences between 2.5 and 3, 3 and 3.5, 3.5 and 4, and 4 and 4.5 h post Gd-DTPA(2-) application. Our preliminary data therefore suggest that the time window suitable for a dGEMRIC (delayed gadolinium-enhanced MRI of cartilage)-like T(1) mapping of the menisci is relatively short, and lies between 2.5 and 4.5 h after Gd-DTPA(2-) injection.

dGEMRIC and subsequent T1 mapping of the hip at 1.5 Tesla: normative data on zonal and radial distribution in asymptomatic volunteers.

PURPOSE: To characterize the zonal distribution of three-dimensional (3D) T1 mapping in the hip joint of asymptomatic adult volunteers. MATERIALS AND METHODS: This study included 10 volunteers (3 males and 7 females with a mean age of 26.5 years; range, 24-31 years). MRI protocol included standard sequences for hip imaging and a dual-flip-angle 3D gradient-echo (GRE) sequence with volumetric interpolated breathhold examination (VIBE) postcontrast administration. Seven radial cuts were created clockwise around the femoral neck by using multi-planar reconstruction. RESULTS: Analysis of the radial distribution revealed an increase of T1-values toward the superior regions. T1-values differed between the peripheral and central portions. The standard deviation (SD) ranged from 76.2 ms to 124.1 ms in the peripheral zone, and from 69.1 ms to 112.9 ms in the central zone. In both zones, SD was low in the superior regions compared with the anterior and posterior regions of the joint. Based on the high intra- (0.95) and interobserver (0.87) agreement, normative data from this study will prepare the foundation for further studies of dGEMRIC and T1 in the hip. CONCLUSION: We noted a radial T1 mapping pattern with higher values in the superior zone that was not statistically significant and a notable trend in zonal distribution between peripheral and central zones. These findings are critical while outlining future studies for detailed objective evaluation of zonal cartilage lesions due to varying pathologies.

Morphological and biochemical T2 evaluation of cartilage repair tissue based on a hybrid double echo at steady state (DESS-T2d) approach.

PURPOSE: To use a new approach which provides, based on the widely used three-dimensional double-echo steady-state (DESS) sequence, in addition to the morphological information, the generation of biochemical T2 maps in one hybrid sequence. MATERIALS AND METHODS: In 50 consecutive MRIs at 3.0 Tesla (T) after matrix-associated autologous chondrocyte transplantation (MACT) of the knee, by the use this new DESS-T2d approach, the morphological Magnetic resonance Observation of CArtilage Repair Tissue (MOCART) score, as well as biochemical T2d values were assessed. Furthermore, these results were correlated to standard morphological sequences as well as to standard multi-echo spin-echo T2 mapping. RESULTS: The MOCART score correlated (Pearson:0.945; P < 0.001) significantly as assessed with standard morphological sequences (68.8 ± 13.2) and the morphological images of the DESS T2d sequence (68.7 ± 12.6). T2 and T2d relaxation times (ms) were comparable in between the control cartilage (T2: 52.5 ± 11.4; T2d: 46.6 ± 10.3) and the repair tissue (T2: 54.4 ± 11.4; T2d: 47.5 ± 13.0) (T2: P = 0.157; T2d: P = 0.589). As expected, T2d values were lower than the standard-T2 values, however, both functional relaxation times correlated significantly (Pearson:0.429; P < 0.001). CONCLUSION: The presented hybrid approach provides the possibility to combine morphological and biochemical MRI in one fast 3D sequence, and thus, may attract for the clinical use of biochemical MRI.

Advanced morphological 3D magnetic resonance observation of cartilage repair tissue (MOCART) scoring using a new isotropic 3D proton-density, turbo spin echo sequence with variable flip angle distribution (PD-SPACE) compared to an isotropic 3D steady-state free precession sequence (True-FISP) and standard 2D sequences.

PURPOSE: To evaluate a new isotropic 3D proton-density, turbo-spin-echo sequence with variable flip-angle distribution (PD-SPACE) sequence compared to an isotropic 3D true-fast-imaging with steady-state-precession (True-FISP) sequence and 2D standard MR sequences with regard to the new 3D magnetic resonance observation of cartilage repair tissue (MOCART) score. MATERIALS AND METHODS: Sixty consecutive MR scans on 37 patients (age: 32.8 ± 7.9 years) after matrix-associated autologous chondrocyte transplantation (MACT) of the knee were prospectively included. The 3D MOCART score was assessed using the standard 2D sequences and the multiplanar-reconstruction (MPR) of both isotropic sequences. Statistical, Bonferroni-corrected correlation as well as subjective quality analysis were performed. RESULTS: The correlation of the different sequences was significant for the variables defect fill, cartilage interface, bone interface, surface, subchondral lamina, chondral osteophytes, and effusion (Pearson coefficients 0.514-0.865). Especially between the standard sequences and the 3D True-FISP sequence, the variables structure, signal intensity, subchondral bone, and bone marrow edema revealed lower, not significant, correlation values (0.242-0.383). Subjective quality was good for all sequences (P ≥ 0.05). Artifacts were most often visible on the 3D True-FISP sequence (P < 0.05). CONCLUSION: Different isotropic sequences can be used for the 3D evaluation of cartilage repair with the benefits of isotropic 3D MRI, MPR, and a significantly reduced scan time, where the 3D PD-SPACE sequence reveals the best results.

Biochemical (T2, T2* and magnetisation transfer ratio) MRI of knee cartilage: feasibility at ultra-high field (7T) compared with high field (3T) strength.

OBJECTIVE: This study compares the performance and the reproducibility of quantitative T2, T2* and the magnetisation transfer ratio (MTR) of articular cartilage at 7T and 3T. METHODS: Axial MRI of the patella was performed in 17 knees of healthy volunteers (25.8 ± 5.7 years) at 3T and 7T using a comparable surface coil and whole-body MR systems from the same vendor, side-by-side. Thirteen knee joints were assessed once, and four knee joints were measured three times to assess reproducibility. T2 relaxation was prepared by a multi-echo, spin-echo sequence and T2* relaxation by a multi-echo, gradient-echo sequence. MTR was based on a magnetisation transfer-sensitized, steady-state free precession approach. Statistical analysis-of-variance and coefficient-of-variation (CV) were prepared. RESULTS: For T2 and T2*, global values were significantly lower at 7T compared with 3T; the zonal evaluation revealed significantly less pronounced stratification at 7T (p < 0.05). MTR provided higher values at 7T (p < 0.05). CV, indicating reproducibility, showed slightly lower values at 7T, but only for T2 and T2*. CONCLUSION: Although lower T2 and T2* relaxation times were expected at 7T, the differences in stratification between the field strengths were reported for the first time. The assessment of MT is feasible at 7T, but requires further investigation.

Hip arthroscopy after surgical hip dislocation: is predictive imaging possible?

PURPOSE: Our purpose was to study the sensitivity, specificity, and predictive values for hip adhesions, labral tears, and articular cartilage lesions in patients who had open treatment for femoroacetabular impingement, had persistent symptoms, and had both magnetic resonance arthrography (MRA) with radial slices and hip arthroscopy. METHODS: Of 750 patients, 21 patients (6 male and 15 female patients; mean age, 28 years [range, 16 to 41 years]) with persistent groin pain after open osteochondroplasty and femoroacetabular impingement were included. The mean time between open osteochondroplasty and hip arthroscopy was 19 months (range, 4 to 79 months). At index surgery, patients had open osteochondroplasty of the femoral head-neck junction, as well as resection of the acetabular rim with reattachment of the labrum. All patients had preoperative MRA. RESULTS: At hip arthroscopy, 1 tear of the labrum was verified on MRA. MRA showed in all patients adhesions between the neck of the femur and joint capsule, which were confirmed at arthroscopy and removed. Sensitivity of MRA for tears and adhesions was 100%; specificity, 100% and positive predictive value (PPV), 100%. For acetabular cartilage damage, sensitivity was 66.7%; specificity, 77.8%; and PPV, 63.6%. For femoral cartilage damage, sensitivity was 80%; specificity, 100%; and PPV, 20%. Postoperative alpha angles were significantly decreased. Of 21 patients, 3 had persisting groin pain. DISCUSSION: Persistent groin pain after open osteochondroplasty of the hip could result from pathologic changes such as intra-articular adhesions with concomitant soft-tissue impingement. This pathology, as well as cartilage damage and labral tears, can be shown on MRA with radial slices. CONCLUSIONS: Twenty-one patients with persistent groin pain after open osteochondroplasty of the hip had adhesions identified by MRA with radial slices. At hip arthroscopy, these adhesions were removed and 18 of 21 patients had relief of their symptoms. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Quantitative T2 mapping of knee cartilage: differentiation of healthy control cartilage and cartilage repair tissue in the knee with unloading--initial results.

PURPOSE: To prospectively determine on T2 cartilage maps the effect of unloading during a clinical magnetic resonance (MR) examination in the postoperative follow-up of patients after matrix-associated autologous chondrocyte transplantation (MACT) of the knee joint. MATERIALS AND METHODS: Ethical approval for this study was provided by the local ethics commission, and written informed consent was obtained. Thirty patients (mean age, 35.4 years +/- 10.5) with a mean postoperative follow-up period of 29.1 months +/- 24.4 were enrolled. A multiecho spin-echo T2-weighted sequence was performed at the beginning (early unloading) and end (late unloading) of the MR examination, with an interval of 45 minutes. Mean and zonal region of interest T2 measurements were obtained in control cartilage and cartilage repair tissue. Statistical analysis of variance was performed. RESULTS: The change in T2 values of control cartilage (early unloading, 50.2 msec +/- 8.4; late unloading, 51.3 msec +/- 8.5) was less pronounced than the change in T2 values of cartilage repair tissue (early unloading, 51.8 msec +/- 11.7; late unloading, 56.1 msec +/- 14.4) (P = .024). The difference between control cartilage and cartilage repair tissue was not significant for early unloading (P = .314) but was significant for late unloading (P = .036). Zonal T2 measurements revealed a higher dependency on unloading for the superficial cartilage layer. CONCLUSION: Our results suggest that T2 relaxation can be used to assess early and late unloading values of articular cartilage in a clinical setting and that the time point of the quantitative T2 measurement affects the differentiation between native and abnormal articular cartilage. (c) RSNA, 2010.

Synthetic-echo time postprocessing technique for generating images with variable T2-weighted contrast: diagnosis of meniscal and cartilage abnormalities of the knee.

PURPOSE: To assess the feasibility and accuracy of a synthetic-echo time (TE) magnetic resonance (MR) postprocessing technique for the diagnostic evaluation of abnormalities of menisci and articular cartilage in the knee. MATERIALS AND METHODS: This study was approved by the institutional review board. Twenty-four patients (three women, 21 men; mean age, 44.8 years) gave informed written consent to prospectively undergo evaluation of their knees (10 left and 14 right knees) with standard sagittal intermediate-weighted (repetition time msec/TE msec, 2200/17) and fat-saturated T2-weighted (3600/88) fast spin-echo sequences. In addition, sagittal multiecho fast gradient-echo sequences were performed for the generation of synthetic-TE images with variable T2- or T2(*)-weighted contrast by using a newly developed synthetic-TE analysis tool that was incorporated directly into the picture archiving and communication system. Sensitivity, specificity, and accuracy values for detection of lesions in menisci and articular cartilage were calculated by using findings at surgery as reference standard. RESULTS: The standard intermediate-weighted and fat-suppressed T2-weighted MR sequences had overall sensitivity, specificity, and accuracy values of 100% and 100%, 88% and 93%, and 95% and 95% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 82%, 97%, and 95%, respectively, for articular cartilage defects. Corresponding sensitivity, specificity, and accuracy values for multiecho MR imaging with synthetic-TE MR image generation were 92% and 100%, 88% and 87%, and 90% and 90% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 70%, 99%, and 95%, respectively, for articular cartilage defects. CONCLUSION: For the evaluation of menisci and articular cartilage, images generated with the synthetic-TE technique are a potentially viable alternative to standard T2-weighted images obtained at different TEs. Furthermore, the synthetic-TE approach allowed assessment of abnormalities of menisci and articular cartilage with high sensitivity and specificity.

Metacarpophalangeal joints in rheumatoid arthritis: delayed gadolinium-enhanced MR imaging of cartilage--a feasibility study.

PURPOSE: To evaluate the feasibility of delayed gadolinium-enhanced magnetic resonance (MR) imaging of the cartilage of metacarpophalangeal (MCP) joints in patients with rheumatoid arthritis (RA) compared with that in control subjects. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Thirty-one MCP joints in 10 patients with RA (mean age, 59 years; range, 35-77 years) and six healthy volunteers (mean age, 51 years; range, 30-71 years) were examined with delayed gadolinium-enhanced MR imaging of cartilage. Sagittal images of the second and third MCP joints (hereafter, MCP II and MCP III) were acquired with a three-dimensional dual-flip-angle gradient-echo sequence at 3.0 T. B(1) field inhomogeneity-corrected T1 maps were calculated, and delayed gadolinium-enhanced MR imaging of cartilage values for phalangeal and metacarpal cartilage were determined. In addition, cartilage thickness was measured. A nonparametric Mann-Whitney U test was used to assess differences between groups. RESULTS: Phalangeal and metacarpal delayed gadolinium-enhanced MR imaging of cartilage values in patients with RA (MCP II: 388 msec ± 105 [standard deviation] and 342 msec ± 79, respectively; MCP III: 409 msec ± 96 and 371 msec ± 89, respectively) were significantly lower than in control subjects (MCP II: 598 msec ± 62 and 560 msec ± 51, respectively; MCP III: 586 msec ± 57 and 561 msec ± 80, respectively). Cartilage thickness of both joints was comparable in patients with RA (MCP II: 1.28 mm ± 0.50, MCP III: 1.17 mm ± 0.24) and control subjects (MCP II: 1.42 mm ± 0.33, MCP III: 1.18 mm ± 0.26). CONCLUSION: Delayed gadolinium-enhanced MR imaging of cartilage of the MCP joints is feasible at 3.0 T. Delayed gadolinium-enhanced MR imaging of cartilage may help to assess cartilage degeneration in morphologically normal-appearing MCP II and III cartilage in patients with RA.

23Na MR imaging at 7 T after knee matrix-associated autologous chondrocyte transplantation preliminary results.

PURPOSE: To evaluate the feasibility of sodium 7-T magnetic resonance (MR) imaging in repaired tissue and native cartilage of patients after matrix-associated autologous chondrocyte transplantation (MACT) and compare results with delayed gadolinium-enhanced MR imaging of cartilage (dGEMRIC) at 3 T. MATERIALS AND METHODS: Ethical approval was provided by the local ethics committee; written informed consent was obtained from all patients. Six women and six men (mean age, 32.8 year ± 8.2 [standard deviation] and 32.3 years ± 12.7, respectively) were included. Mean time between MACT and MR was 56 months ± 28. A variable three-dimensional (3D) gradient-echo (GRE) dual-flip-angle technique was used for T1 mapping before and after contrast agent administration at 3 T. All patients were also examined at 7 T (mean delay, 70.5 days ± 80.1). A sodium 23-only transmit-receive knee coil was used with the 3D GRE sequence. A statistical analysis of variance and Pearson correlation were applied. RESULTS: Mean signal-to-noise ratio (SNR) was 24 in native cartilage and was 16 in transplants (P < .001). Mean sodium signal intensities normalized with the reference sample were 174 ± 53 and 267 ± 42 for repaired tissue in the cartilage transplant and healthy cartilage, respectively (P < .001). Mean postcontrast T1 values were 510 msec ± 195 and 756 msec ± 188 for repaired tissue and healthy cartilage, respectively (P = .005). Mean score of MR observation of cartilage repair tissue was 75 ± 14. Association between postcontrast T1 and normalized sodium signal values showed a high Pearson correlation coefficient (R) of 0.706 (P = .001). A high correlation of R = 0.836 (P = .001) was found between ratios of normalized sodium values and ratios of T1 postcontrast values. CONCLUSION: With the modified 3D GRE sequence at 7 T, a sufficiently high SNR in sodium images was achieved, allowing for differentiation of repaired tissue from native cartilage after MACT. A strong correlation was found between sodium imaging and dGEMRIC in patients after MACT.

T1 assessment of hip joint cartilage following intra-articular gadolinium injection: a pilot study.

This pilot study defines the feasibility of cartilage assessment in symptomatic femoroacetabular impingement patients using intra-articular delayed gadolinium-enhanced MRI of cartilage (ia-dGEMRIC). Nine patients were scanned preliminary to study the contrast infiltration process into hip joint cartilage. Twenty-seven patients with symptomatic femoroacetabular impingement were subsequently scanned with intra-articular delayed gadolinium-enhanced MRI of cartilage. These T(1) findings were correlated to morphological findings. Zonal variations were studied. This pilot study demonstrates a significant difference between the pre- and postcontrast T(1) values (P < 0.001) remaining constant for 45 min. We noted higher mean T(1) values in morphologically normal-appearing cartilage than in damaged cartilage, which was statistically significant for all zones except the anterior-superior zone. Intraobserver (0.972) and interobserver correlation coefficients (0.933) were statistically significant. This study outlines the feasibility of intra-articular delayed gadolinium-enhanced MRI of cartilage for assessment of cartilage changes in patients with femoroacetabular impingement. It can also define the topographic extent and differing severities of cartilage damage.

T2 and T2* mapping in patients after matrix-associated autologous chondrocyte transplantation: initial results on clinical use with 3.0-Tesla MRI.

OBJECTIVES: To use T2 and T2* mapping in patients after matrix-associated autologous chondrocyte transplantation (MACT) of the knee, and to compare and correlate both methodologies. METHODS: 3.0-Tesla MRI was performed on 30 patients (34.6 +/- 9.9 years) with a follow-up period of 28.1 +/- 18.8 months after MACT. Multi-echo, spin-echo-based T2 mapping using six echoes and gradient-echo-based T2* mapping using six echoes were prepared. T2 and T2* maps were obtained using a pixel-wise, mono-exponential, non-negative least-squares fit analysis. Region-of-interest analysis was performed for mean (full-thickness) as well as deep and superficial aspects of the cartilage repair tissue and control cartilage sites. RESULTS: Mean T2 values (ms) were comparable for the control cartilage (53.4 +/- 11.7) and the repair tissue (55.5 +/- 11.6) (p > 0.05). Mean T2* values (ms) for control cartilage (30.9 +/- 6.6) were significantly higher than those of the repair tissue (24.5 +/- 8.1) (p < 0.001). Zonal stratification was more pronounced for T2* than for T2. The correlation between T2 and T2* was highly significant (p < 0.001), with a Pearson coefficient between 0.276 and 0.433. CONCLUSION: T2 and T2* relaxation time measurements in the evaluation of cartilage repair tissue and its zonal variation show promising results, although the properties visualised by T2 and T2* may differ.

Lumbar intervertebral disc abnormalities: comparison of quantitative T2 mapping with conventional MR at 3.0 T.

OBJECTIVE: To assess the relationship of morphologically defined lumbar disc abnormalities with quantitative T2 mapping. METHODS: Fifty-three patients, mean age 39 years, with low back pain were examined by MRI at 3 T (sagittal T1-fast spin echo (FSE), three-plane T2-FSE for morphological MRI, multi-echo spin echo for T2 mapping). All discs were classified morphologically. Regions of interest (ROIs) for the annulus were drawn. The space in between was defined as the nucleus pulposus (NP). To evaluate differences between the classified groups, univariate ANOVA with post hoc Games-Howell and paired two-tailed t tests were used. RESULTS: In 265 discs we found 39 focal herniations, 10 annular tears, 123 bulging discs and 103 "normal discs". T2 values of the NP between discs with annular tear and all other groups were statistically significantly different (all p ≤ 0.01). Discs with annular tears showed markedly lower NP T2 values than discs without. The difference in NP T2 values between discs with focal herniation and normal discs (p = 0.005) was statistically significant. There was no difference in NP T2 values between bulging and herniated discs (p = 0.11) CONCLUSION: Quantitative T2 mapping of the nucleus pulposus of the intervertebral disc in the lumbar spine at 3 T reveals significant differences in discs with herniation and annular tears compared with discs without these abnormalities.