Fast diffusion-weighted steady state free precession imaging of in vivo knee cartilage.

Quantification of molecular diffusion with steady state free precession (SSFP) is complicated by the fact that diffusion effects accumulate over several repetition times (TR) leading to complex signal dependencies on transverse and longitudinal magnetization paths. This issue is commonly addressed by setting TR > T(2), yielding strong attenuation of all higher modes, except of the shortest ones. As a result, signal attenuation from diffusion becomes T(2) independent but signal-to-noise ratio (SNR) and sequence efficiency are remarkably poor. In this work, we present a new approach for fast in vivo steady state free precession diffusion-weighted imaging of cartilage with TR << T(2) offering a considerable increase in signal-to-noise ratio and sequence efficiency. At a first glance, prominent coupling between magnetization paths seems to complicate quantification issues in this limit, however, it is observed that diffusion effects become rather T(2) (ΔD ≈ 1/10 ΔT(2)) but not T(1) independent (ΔD ≈ 1/2 ΔT(1)) for low flip angles α ≈ 10 - 15°. As a result, fast high-resolution (0.35 × 0.35 - 0.50 × 0.50 mm(2) in-plane resolution) quantitative diffusion-weighted imaging of human articular cartilage is demonstrated at 3.0 T in a clinical setup using estimated T(1) and T(2) or a combination of measured T(1) and estimated T(2) values.

Patterns of joint damage seen on MRI in early hip osteoarthritis due to structural hip deformities.

OBJECTIVE: The aim of this study was to evaluate differences in damage patterns assessed using magnetic resonance imaging (MRI) between hips with femoroacetabular impingement (FAI) and developmental dysplasia of the hip (DDH) as well as to correlate MRI findings with delayed Gadolinium enhanced MRI of cartilage (dGEMRIC) and with patient pain. DESIGN: This retrospective study included 40 patients (mean age 28.6 ± 11.2 years) who underwent dGEMRIC and morphological MRI of the hip. Twenty-one hips with FAI and 19 with DDH were investigated. A self-developed morphological grading (MRI score) and dGEMRIC evaluation were done on seven radial reformats obtained from an isotropic 3D True-fast imaging with steady state precession (FISP) sequence and an isotropic T1-mapping sequence. The observed damage patterns were summed up into sub-scores and a total MRI score. RESULTS: Labrum damage, paralabral cysts, and acetabular rim bone cysts were more common in DDH patients than in FAI patients. No significant differences were seen in the occurrence of cartilage damage, bone cysts, or osteophytes. In DDH (but not in FAI), the dGEMRIC index demonstrated a tendency for lower values in areas next to cartilage defects. There was no association between labrum damage and dGEMRIC index. A moderate correlation was seen between Western Ontario and McMaster Universities (WOMAC) pain score and cartilage damage, paralabral cysts, and the total MRI score. CONCLUSIONS: This study confirms a higher prevalence of labrum damage but not cartilage damage in patients with DDH in comparison to patients with FAI. In addition, our data suggests an association of cartilage damage and paralabral cysts with patient reported pain.

A new method to analyze dGEMRIC measurements in femoroacetabular impingement: preliminary validation against arthroscopic findings.

OBJECTIVE: To validate a new method to analyze delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) measurements in the hip for early assessment of cartilage defects in femoroacetabular impingement (FAI). METHODS: We performed a retrospective review of 10 hips in 10 FAI patients, who underwent hip arthroscopy. T1-weighted images and dGEMRIC T(1) maps were acquired at 1.5 T on coronal planes, including the anterior-superior, superior, posterior-superior hip cartilage. For all slices, a region of interest (ROI) was defined over the central portion of the femoral cartilage, assumed to be healthy, and T1 values (x) were transformed to standard scores (z) using z = (x -µ)/σ, where µ and σ are the average and standard deviation of T1 in the femoral ROI. Diagnostic performance of the resulting standardized dGEMRIC maps was evaluated against intraoperative findings and compared with that of a previously proposed dGEMRIC analysis as well as morphologic assessment. RESULTS: Assuming z = -2 or z = -3 as the threshold between normal and degenerated cartilage, sensitivity, specificity and accuracy were 88%, 51% and 62%, and 71%, 63% and 65%, respectively. By using T1 = 500 ms as single threshold for all dGEMRIC T1 maps, these values became 47%, 58% and 55%, whereas they were 47%, 79% and 70% for morphologic evaluation. CONCLUSIONS: Standardized dGEMRIC can increase the sensitivity in detecting abnormal cartilage in FAI and has the potential to improve the clinical interpretation of dGEMRIC measurements in FAI, by removing the effect of inter- and intra-patient T1 variability.

Evaluation of articular cartilage in patients with femoroacetabular impingement (FAI) using T2* mapping at different time points at 3.0 Tesla MRI: a feasibility study.

OBJECTIVES: To define the feasibility of utilizing T2* mapping for assessment of early cartilage degeneration prior to surgery in patients with symptomatic femoroacetabular impingement (FAI), we compared cartilage of the hip joint in patients with FAI and healthy volunteers using T2* mapping at 3.0 Tesla over time. MATERIALS AND METHODS: Twenty-two patients (13 females and 9 males; mean age 28.1 years) with clinical signs of FAI and Tönnis grade ≤ 1 on anterior-posterior x-ray and 35 healthy age-matched volunteers were examined at a 3 T MRI using a flexible body coil. T2* maps were calculated from sagittal- and coronal-oriented gradient-multi-echo sequences using six echoes (TR 125, TE 4.41/8.49/12.57/16.65/20.73/24.81, scan time 4.02 min), both measured at beginning and end of the scan (45 min time span between measurements). Region of interest analysis was manually performed on four consecutive slices for superior and anterior cartilage. Mean T2* values were compared among patients and volunteers, as well as over time using analysis of variance and Student's t-test. RESULTS: Whereas quantitative T2* values for the first measurement did not reveal significant differences between patients and volunteers, either for sagittal (p = 0.644) or coronal images (p = 0.987), at the first measurement, a highly significant difference (p ≤ 0.004) was found for both measurements with time after unloading of the joint. Over time we found decreasing mean T2* values for patients, in contrast to increasing mean T2* relaxation times in volunteers. CONCLUSION: The study proved the feasibility of utilizing T2* mapping for assessment of early cartilage degeneration in the hip joint in FAI patients at 3 Tesla to predict possible success of joint-preserving surgery. However, we suggest the time point for measuring T2* as an MR biomarker for cartilage and the changes in T2* over time to be of crucial importance for designing an MR protocol in patients with FAI.

Hip Osteoarthritis MRI Scoring System (HOAMS): reliability and associations with radiographic and clinical findings.

OBJECTIVE: To develop a semiquantitative MRI-based scoring system (HOAMS) of hip osteoarthritis (OA) and test its reliability and validity. DESIGN: Fifty-two patients with chronic hip pain were included. 1.5T magnetic resonance imaging (MRI) was performed on all patients. Pelvic radiographs were scored according to the Kellgren-Lawrence (KL) system. Clinical outcomes were assessed by the hip osteoarthritis outcome score (HOOS). MRIs were analyzed using a novel whole-joint MRI score that incorporated 13 articular features. Reliability was determined on a random subset of 15 cases. Weighted-kappa statistics and overall agreement were used as a measure of intra- and inter-observer reliability. Associations between MRI features and radiographic OA severity were calculated using Cochran-Armitage test for trend. Ordinal logistic regression was used to assess associations between MRI features and severity of pain and functional limitation. RESULTS: Distribution of radiographic grading was: KL 0=12 (27%), KL 1=11 (25%), KL 2=14 (32%), KL 3=5 (11%) and KL 4=2 (5%). Intra-reader reliability for the different features ranged from 0.18 (cysts) to 0.85 (cartilage). Inter-reader reliability ranged between 0.15 (cysts) and 0.85 (BMLs). Low kappas were due to low frequencies of some features as overall percent agreement was good to excellent (83.8% and 83.1%). There was a strong association between MRI-detected lesions and radiographic severity (P=0.002). Non-significant trends were observed between MRI features and clinical outcomes. CONCLUSION: MRI-based semiquantitative assessment of the hip shows adequate reliability. Presence of more severe MRI-detected intraarticular pathology shows a strong association with radiographic OA. The results suggest possible associations between MRI-detected pathology and clinical symptoms.

The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity.

BACKGROUND: The prevalence of a cam-type deformity in athletes and its association with vigorous sports activities during and after the growth period is unknown. QUESTIONS/PURPOSES: We therefore compared the prevalence and occurrence of a cam-type deformity by MRI in athletes during childhood and adolescence with an age-matched control group. PATIENTS AND METHODS: We retrospectively reviewed 72 hips in 37 male basketball players with a mean age of 17.6 years (range, 9-25 years) and 76 asymptomatic hips of 38 age-matched volunteers who had not participated in sporting activities at a high level. RESULTS: Eleven (15%) of the 72 hips in the athletes were painful and had positive anterior impingement tests on physical examination. Internal rotation of the hip averaged 30.1° (range, 15°-45°) in the control group compared with only 18.9° (range, 0°-45°) in the athletes. The maximum value of the alpha angle throughout the anterosuperior head segment was larger in the athletes (average, 60.5° ± 9°), compared with the control group (47.4° ± 4°). These differences became more pronounced after closure of the capital growth plate. Overall, the athletes had a 10-fold increased likelihood of having an alpha angle greater than 55° at least at one measurement position. CONCLUSIONS: Our observations suggest a high intensity of sports activity during adolescence is associated with a substantial increase in the risk of cam-type impingement. These patients also may be at increased risk of subsequent development of secondary coxarthrosis. LEVEL OF EVIDENCE: Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Radial dGEMRIC in developmental dysplasia of the hip and in femoroacetabular impingement: preliminary results.

OBJECTIVE: To assess the pattern of cartilage damage in symptomatic cases of developmental dysplasia of the hip (DDH) and of femoroacetabular impingement (FAI) with a novel three-dimensional (3D) delayed Gadolinium enhanced magnetic resonance imaging of cartilage (dGEMRIC) technique. METHODS: After clinical diagnosis with conventional radiographs, two consecutive series of each 20 patients with DDH or FAI were assessed with 3D dGEMRIC. Radial T1 maps were reconstructed and region of interest analysis of the central and peripheral cartilage was carried out. RESULTS: The dGEMRIC index was mean 531 ± 92.7 (391-729) ms in DDH and 551 ± 95.7 (372-694) ms in FAI, respectively (P=0.507). Subgroup analysis showed higher T1 in the weight-bearing areas and significantly higher values in the central areas (DDH P<0.0001, N=11; FAI P=0.036, N=14) of the acetabulum in pre-arthritic cases (dGEMRIC index>500 ms) both in DDH and FAI. A breakdown of this distribution was found both in DDH and FAI cases with dGEMRIC index<500 ms. Pearson correlation analysis demonstrated the dGEMRIC index had a poor predictive value for the anterior-superior quadrant of the hip joint in FAI (r=0.482, P=0.031, r(2)=0.233). CONCLUSION: Radial dGEMRIC allows for the assessment of cartilage damage in the entire hip; different patterns of T1 distribution are found in DDH and FAI at progressed stages. The assessment of the anterior-superior quadrant of the acetabulum can be considered a fundamental advantage of the 3D dGEMRIC protocol.

Detection of degenerative cartilage disease: comparison of high-resolution morphological MR and quantitative T2 mapping at 3.0 Tesla.

OBJECTIVE: The aim of the study was to investigate the association of T2 relaxation times of the knee with early degenerative cartilage changes. Furthermore the impact of unloading the knee on T2 values was evaluated. METHODS: Forty-three patients with knee pain and an ICRS (International Cartilage Repair Society) cartilage defect grade

Multimodal approach in the use of clinical scoring, morphological MRI and biochemical T2-mapping and diffusion-weighted imaging in their ability to assess differences between cartilage repair tissue after microfracture therapy and matrix-associated autologous chondrocyte transplantation: a pilot study.

OBJECTIVE: The aim of the present pilot study is to show initial results of a multimodal approach using clinical scoring, morphological magnetic resonance imaging (MRI) and biochemical T2-relaxation and diffusion-weighted imaging (DWI) in their ability to assess differences between cartilage repair tissue after microfracture therapy (MFX) and matrix-associated autologous chondrocyte transplantation (MACT). METHOD: Twenty patients were cross-sectionally evaluated at different post-operative intervals from 12 to 63 months after MFX and 12-59 months after MACT. The two groups were matched by age (MFX: 36.0+/-10.4 years; MACT: 35.1+/-7.7 years) and post-operative interval (MFX: 32.6+/-16.7 months; MACT: 31.7+/-18.3 months). After clinical evaluation using the Lysholm score, 3T-MRI was performed obtaining the MR observation of cartilage repair tissue (MOCART) score as well as T2-mapping and DWI for multi-parametric MRI. Quantitative T2-relaxation was achieved using a multi-echo spin-echo sequence; semi-quantitative diffusion-quotient (signal intensity without diffusion-weighting divided by signal intensity with diffusion weighting) was prepared by a partially balanced, steady-state gradient-echo pulse sequence. RESULTS: No differences in Lysholm (P=0.420) or MOCART (P=0.209) score were observed between MFX and MACT. T2-mapping showed lower T2 values after MFX compared to MACT (P=0.039). DWI distinguished between healthy cartilage and cartilage repair tissue in both procedures (MFX: P=0.001; MACT: P=0.007). Correlations were found between the Lysholm and the MOCART score (Pearson: 0.484; P=0.031), between the Lysholm score and DWI (Pearson:-0.557; P=0.011) and a trend between the Lysholm score and T2 (Person: 0.304; P=0.193). CONCLUSION: Using T2-mapping and DWI, additional information could be gained compared to clinical scoring or morphological MRI. In combination clinical, MR-morphological and MR-biochemical parameters can be seen as a promising multimodal tool in the follow-up of cartilage repair.

Cartilage damage in femoroacetabular impingement (FAI): preliminary results on comparison of standard diagnostic vs delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC).

OBJECTIVES: To study the three-dimensional (3D) T1 patterns in different types of femoroacetabular impingement (FAI) by utilizing delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) and subsequent 3D T1 mapping. We used standard grading of OA by Tonnis grade on standard radiographs and morphological grading of cartilage in MRI for comparative analysis. METHODS: dGEMRIC was obtained from ten asymptomatic young-adult volunteers and 26 symptomatic FAI patients. MRI included the routine hip protocol and a dual-flip angle (FA) 3D gradient echo (GRE) sequence utilizing inline T1 measurement. Cartilage was morphologically classified from the radial images based on the extent of degeneration as: no degeneration, degeneration zone measuring <0.75 cm from the rim, >0.75 cm, or total loss. T1 findings were evaluated and correlated. RESULTS: All FAI types revealed remarkably lower T1 mean values in comparison to asymptomatic volunteers in all regions of interest. Distribution of the T1 dGEMRIC values was in accordance with the specific FAI damage pattern. In cam-types (n=6) there was a significant drop (P<0.05) of T1 in the anterior to superior location. In pincer-types (n=7), there was a generalized circumferential decrease noted. High inter-observer (intra-observer) reliability was noted for T1 assessment using intra-class correlation (ICC):intra-class coefficient=0.89 (0.95). CONCLUSIONS: We conclude that a pattern of zonal T1 variation does seem to exist that is unique for different sub-groups of FAI. The FA GRE approach to perform 3D T1 mapping has a promising role for further studies of standard MRI and dGEMRIC in the hip joint.

[Radiological diagnosis of femoroacetabular impingement]. / Radiologische Diagnose des femoroazetabulären Impingements.

Femoroacetabular impingements (FAI) are due to an anatomical disproportion between the proximal femur and the acetabulum which causes premature wear of the joint surfaces. An operation is often necessary in order to relieve symptoms such as limited movement and pain as well as to prevent or slow down the degenerative process. The result is dependent on the preoperative status of the joint with poor results for advanced arthritis of the hip joint. This explains the necessity for an accurate diagnosis in order to recognize early stages of damage to the joint. The diagnosis of FAI includes clinical examination, X-ray examination and magnetic resonance imaging (MRI). The standard X-radiological examination for FAI is carried out using two X-ray images, an anterior-posterior view of the pelvis and a lateral view of the proximal femur, such as the cross-table lateral or Lauenstein projections. It is necessary that positioning criteria are adhered to in order to avoid distortion artifacts. MRI permits an examination of the pelvis on three levels and should also include radial planned sequences for improved representation of peripheral structures, such as the labrum and peripheral cartilage. The use of contrast medium for a direct MR arthrogram has proved to be advantageous particularly for representation of labrum damage. The data with respect to cartilage imaging are still unclear. Further developments in technology, such as biochemical-sensitive MRI applications, will be able to improve the diagnosis of the pelvis in the near future.

[Delayed gadolinium enhanced MRI of cartilage (dGEMRIC): molecular MRI of hip joint cartilage]. / "Delayed Gadolinium Enhanced MRI of Cartilage" (dGEMRIC): Molekulare MRT-Bildgebung des Hüftgelenkknorpels.

Factors such as instability and impingement lead to early cartilage damage and osteoarthritis of the hip joint. The surgical outcome of joint-preserving surgery about the hip joint depends on the preoperative quality of joint cartilage.For in vivo evaluation of cartilage quality, different biochemically sensitive magnetic resonance imaging (MRI) procedures have been tested, some of which have the potential of inducing a paradigm shift in the evaluation and treatment of cartilage damage and early osteoarthritis.Instead of reacting to late sequelae in a palliative way, physicians could assess cartilage damage early on, and the treatment intensity could be adequate and based on the disease stage. Furthermore, the efficiency of different therapeutic interventions could be evaluated and monitored.This article reviews the recent application of delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and discusses its use for assessing cartilage quality in the hip joint. dGEMRIC is more sensitive to early cartilage changes in osteoarthritis than are radiographic measures and might be a helpful tool for assessing cartilage quality.

[High-field and ultrahigh-field magnetic resonance imaging: new possibilities for imaging joints]. / Hochfeld- und Ultrahochfeldmagnetresonanztomographie. Neue Möglichkeiten für die Bildgebung der Gelenke.

Whole-body MR tomography at 3 T is moving steadily from research into routine clinical practice. The most important advantage of high-field MRI is the higher signal to noise ratio, which allows acquisitions in the musculo-skeletal system with higher resolution within the same scan time. The imaging of small joints, the visualization of labral anatomy and pathology in the shoulder and hip joints, as well as cartilage imaging will benefit from higher resolution protocols. In addition to improved morphological imaging of articular cartilage, the higher sensitivity of 3 T allows the clinical use of advanced MR techniques of cartilage such as T1 and T2 mapping, diffusion and sodium imaging. The improved spectral resolution with the higher field may improve metabolic imaging of tumors of the skeleton and soft tissues.

Biochemical evaluation of articular cartilage in patients with osteochondrosis dissecans by means of quantitative T2- and T2-mapping at 3T MRI: a feasibility study.

OBJECTIVE: To perform an in vivo evaluation comparing overlying articular cartilage in patients suffering from osteochondrosis dissecans (OCD) in the talocrural joint and healthy volunteers using quantitative T2 mapping at 3.0 T. METHOD AND MATERIALS: Ten patients with OCD of Grade II or lower and 9 healthy age matched volunteers were examined at a 3.0 T whole body MR scanner using a flexible multi-element coil. In all investigated persons MRI included proton-density (PD)-FSE and 3D GRE (TrueFisp) sequences for morphological diagnosis and location of anatomical site and quantitative T2 and T2 maps. Region of interest (ROI) analysis was performed for the cartilage layer above the OCD and for a morphologically healthy graded cartilage layer. Mean T2 and T2 values were then statistically analysed. RESULTS: The cartilage layer of healthy volunteers showed mean T2 and T2 values of 29.4 ms (SD 4.9) and 11.8 ms (SD 2.7), respectively. In patients with OCD of grade I and II lesions mean T2 values were 40.9 ms (SD 6.6), 48.7 ms (SD 11.2) and mean T2 values were 16.1 ms (SD 3.2), 16.2 ms (SD 4.8). Therefore statistically significantly higher mean T2 and T2 values were found in patients suffering from OCD compared to healthy volunteers. CONCLUSION: T2 and T2 mapping can help assess the microstructural composition of cartilage overlying osteochondral lesions.

Quantitative T2 mapping of the patella at 3.0T is sensitive to early cartilage degeneration, but also to loading of the knee.

OBJECTIVE: The aim of the study was to explore the sensitivity and robustness of T2 mapping in the detection and quantification of early degenerative cartilage changes at the patella. MATERIALS AND METHODS: Forty-two patients (22 women, 20 men) with a mean age of 30.3 years and a symptomatic cartilage defect of ICRS grade ≤2 were examined using a 3T MRI with an 8-channel knee coil. The cartilage lesion was graded based on high-resolution PD TSE and 3D isotropic TrueFISP images. T2 maps were calculated from a standard MESE-sequence, performed at the beginning and at the end of the scan (40min in-between). Depending on the defect size, a region-of-interest (ROI) analysis was performed on 1-3 consecutive slices. Mean T2 values for the deep, superficial, and global layer as well as the zonal variation were compared among defect grades (ANOVA, post hoc Duncan-test) and over time (Student's t-test). RESULTS: T2-measurements directly correlated with the extent of cartilage defect (ICRS grade) at all layers and at both time-points. However, correlations were closer for the second measurement at the end of the scan. In this unloaded state, differences in T2-values became more pronounced and were significant even between cartilage of normal appearance adjacent to the defect and healthy cartilage of control patients (both ICRS grade 0). In contrast, there were no such differences among grades in the zonal variation at any time. CONCLUSION: T2 mapping might be a sensitive method for the detection of early cartilage degeneration at the patella in the unloaded joint.

Microfracture in the Ankle: Clinical Results and MRI with T2-Mapping at 3.0 T after 1 to 8 Years.

BACKGROUND: Microfracture (MFX) is frequently used to treat deep cartilage defects in the ankle; however, the data on repair tissue (RT) quality after MFX are very limited at this time. T2-mapping at 3 T has been optimized for the ankle and can be used to noninvasively evaluate cartilage collagen and water content. The aim of this study was to determine if the RT after MFX in the ankle had T2 properties similar to the adjacent reference cartilage (RC). METHODS: Fourteen cases after MFX in the ankle were assessed with morphological MRI and T2-mapping at 3 T. The American Orthopaedic Foot and Ankle Society (AOFAS) score and a modified Cinicinnati Knee Rating System rating were used to evaluate the clinical outcome. The MRI protocol included a 3-dimensional sequence and a proton-density sequence for morphological evaluation and a multiecho spin echo sequence for T2-mapping. Region of interest analyses were carried out in accordance with the morphological images to ensure complete coverage of the defect site. RESULTS: Both clinical scores demonstrated significant improvement at the time of the MR examination (P < 0.001). RT T2 was 49.3 ± 10.1 (range, 35.7-69.3) milliseconds, and RC T2 was 49.9 ± 8.2 (range, 38.4-63.7) milliseconds (P = 0.838). Relative T2 (rT2) was 1.00 ± 0.20 (range, 0.72-1.36). CONCLUSION: MFX in the ankle can provide RT with T2 properties similar to adjacent cartilage.

Femoroacetabular cam-type impingement: diagnostic sensitivity and specificity of radiographic views compared to radial MRI.

PURPOSE: To retrospectively assess the diagnostic sensitivity of 45° Dunn view and cross-table lateral radiographs for the assessment of cam deformity by comparison with radial MRI. MATERIALS AND METHODS: 60 cases with radiographs (38 a-p and 45° Dunn views, 22 a-p and cross-table lateral views) and radial MRI were assessed. Alpha angle measurements were obtained both for radiographs and radial MRI. Statistics included frequency analysis, bivariate linear correlation analyses of MRI and radiograph measurements and cross-table analyses testing for the sensitivity and specificity of radiographs for the detection of an alpha angle larger than 55°. RESULTS: 53.3% had the maximum alpha angle in the superior-anterior aspect of the femoral head-neck junction. Cam deformity was found in 45/60 cases (75%) in radial MRI. Pearson correlation demonstrated the Dunn view was most accurate for the superior-anterior aspect (.772, P<.001). The cross-table lateral views were best suited for the anterior-superior aspect (.511, P<.05). The sensitivity for cam deformity in the Dunn view was 96.4% vs. 70.6% in the cross-table lateral view. CONCLUSION: The 45° Dunn view can improve the first line of impingement diagnostics. Radial MRI however remains indispensable for pre-operative planning and the evaluation of symptomatic cases without obvious deformity.

T2 mapping and dGEMRIC after autologous chondrocyte implantation with a fibrin-based scaffold in the knee: preliminary results.

OBJECTIVE: To assess repair tissue (RT) after the implantation of BioCartII, an autologous chondrocyte implantation (ACI) technique with a fibrin-hyaluronan polymer as scaffold. T2 mapping and delayed Gadolinium Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) were used to gain first data on the biochemical properties of BioCartII RT in vivo. METHODS: T2 mapping and dGEMRIC were performed at 3T in five patients (six knee joints) who had undergone ACI 15-27 months before. T2 maps were obtained using a pixel wise, mono-exponential non-negative least squares fit analysis. For quantitative T1 mapping a dual flip angle 3D GRE sequence was used and T1 maps were calculated pre- and post-contrast using IDL software. Subsequent region of interest analysis was carried out in comparison with morphologic MRI. RESULTS: A spatial variation of T2 values in both hyaline, normal cartilage (NC) and RT was found. Mean RT T2 values and mean NC T2 values did not differ significantly. Relative T2 values were calculated from global RT and NC T2 and showed a small range (0.84-1.07). The relative delta relaxation rates (rDeltaR1) obtained from the T1 maps had a wider range (0.77-4.91). CONCLUSION: T2 mapping and dGEMRIC provided complementary information on the biochemical properties of the repair tissue. BioCartII apparently can provide RT similar to hyaline articular cartilage and may become a less-invasive alternative to ACI with a periosteal flap.

[Cartilage quality in finger joints: delayed Gd(DTPA)²-enhanced MRI of the cartilage (dGEMRIC) at 3T]. / Knorpelqualität an den Fingergelenken: delayed Gd(DTPA)²-enhanced MRI of the cartilage (dGEMRIC) bei 3T.

PURPOSE: To evaluate the feasibility of molecular cartilage MRI in finger joints. MATERIALS AND METHODS: Delayed Gd(DTPA)²-enhanced MRI of the cartilage (dGEMRIC) using a variable flip angle approach (VFA) was performed for the metacarpophalangeal (MCP) joints II and III in nine healthy volunteers and eighteen patients with rheumatoid arthritis (RA). The cartilage thickness was measured. Additionally, dGEMRIC was performed on proximal interphalangeal joints (PIP) in two patients with finger osteoarthritis (OA). RESULTS: the dGEMRIC index of the four evaluated cartilage areas was significantly decreased in RA patients compared to healthy subjects. The dGEMRIC index of MCP II phalangeal cartilage was 389.6 ± 85.5 msec vs. 558.7 ± 74.4 msec in healthy subjects. The metacarpal MCP II cartilage dGEMRIC index was 357.3 msec ± 97.1 msec vs. 490.0 ± 86.6 msec. The dGEMRIC indices of MCP III were: phalangeal 436.2 ± 113.6 msec in RA, 558.8 ± 115.5 msec in healthy subjects and metacarpal 398.0 ± 97.6 msec in RA and 529.6 ± 111.0 msec in healthy subjects. Age and cartilage thickness were not significantly different. In PIP joints of finger osteoarthritis patients, low dGEMRIC indices were noted, compared to the controls. CONCLUSION: The dGEMRIC of finger joints is feasible in patients with RA and finger OA. Morphologically normal cartilage shows significantly decreased dGEMRIC values in RA, pointing towards cartilage degeneration on a molecular level. Further studies are needed to establish the usefulness of this technique for early diagnosis, prognosis and therapy monitoring.

Experimental model to evaluate in vivo and in vitro cartilage MR imaging by means of histological analyses.

OBJECTIVES: Implementation of an experimental model to compare cartilage MR imaging by means of histological analyses. MATERIAL AND METHODS: MRI was obtained from 4 patients expecting total knee replacement at 1.5 and/or 3T prior surgery. The timeframe between pre-op MRI and knee replacement was within two days. Resected cartilage-bone samples were tagged with Ethi-pins to reproduce the histological cutting course. Pre-operative scanning at 1.5 T included following parameters for fast low angle shot (FLASH: TR/TE/FA=33 ms/6 ms/30 degrees, BW=110 kHz, 120 mm x 120 mm FOV, 256 x 256 matrix, 0.65 mm slice-thickness) and double echo steady state (DESS: TR/TE/FA=23.7 ms/6.9 ms/40 degrees, BW=130 kHz, 120 x 120 mm FOV, 256 x 256 matrix, 0.65 mm slice-thickness). At 3T, scan parameters were: FLASH (TR/TE/FA=12.2 ms/5.1 ms/10 degrees, BW=130 kHz, 170 x 170 mm FOV, 320 x 320, 0.5mm slice-thickness) and DESS (TR/TE/FA=15.6 ms/4.5 ms/25 degrees, BW=200 kHz, 135 mm x 150 mm FOV, 288 x 320 matrix, 0.5mm slice-thickness). Imaging of the specimens was done the same day at 1.5 T. MRI (Noyes) and histological (Mankin) score scales were correlated using the paired t-test. Sensitivity and specificity for the detection of different grades of cartilage degeneration were assessed. Inter-reader and intra-reader reliability was determined using Kappa analysis. RESULTS: Low correlation (sensitivity, specificity) was found for both sequences in normal to mild Mankin grades. Only moderate to severe changes were diagnosed with higher significance and specificity. The use of higher field-strengths was advantageous for both protocols with sensitivity values ranging from 13.6% to 93.3% (FLASH) and 20.5% to 96.2% (DESS). Kappa values ranged from 0.488 to 0.944. CONCLUSIONS: Correlating MR images with continuous histological slices was feasible by using three-dimensional imaging, multi-planar-reformat and marker pins. The capability of diagnosing early cartilage changes with high accuracy could not be proven for both FLASH and DESS.