Tallal C. Mamisch

Cartilage T2 Assessment at 3-T MR Imaging: In Vivo Differentiation of Normal Hyaline Cartilage from Reparative Tissue after Two Cartilage Repair Procedures—Initial Experience

PURPOSE To prospectively compare cartilage T2 values after microfracture therapy (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) repair procedures. MATERIALS AND METHODS The study had institutional review board approval by the ethics committee of the Medical University of Vienna; informed consent was obtained. Twenty patients who underwent MFX or MACT (10 in each group) were enrolled. For comparability, patients of each group were matched by mean age (MFX, 40.0 years +/- 15.4 [standard deviation]; MACT, 41.0 years +/- 8.9) and postoperative interval (MFX, 28.6 months +/- 5.2; MACT, 27.4 months +/- 13.1). Magnetic resonance (MR) imaging was performed with a 3-T MR imager, and T2 maps were calculated from a multiecho spin-echo measurement. Global, as well as zonal, quantitative T2 values were calculated within the cartilage repair area and within cartilage sites determined to be morphologically normal articular cartilage. Additionally, with consideration of the zonal organization, global regions of interest were subdivided into deep and superficial areas. Differences between cartilage sites and groups were calculated by using a three-way analysis of variance. RESULTS Quantitative T2 assessment of normal native hyaline cartilage showed similar results for all patients and a significant trend of increasing T2 values from deep to superficial zones (P < .05). In cartilage repair areas after MFX, global mean T2 was significantly reduced (P < .05), whereas after MACT, mean T2 was not reduced (P > or = .05). For zonal variation, repair tissue after MFX showed no significant trend between different depths (P > or = .05), in contrast to repair tissue after MACT, in which a significant increase from deep to superficial zones (P < .05) could be observed. CONCLUSION Quantitative T2 mapping seems to reflect differences in repair tissues formed after two surgical cartilage repair procedures. (c) RSNA, 2008.

Three‐dimensional delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) for in vivo evaluation of reparative cartilage after matrix‐associated autologous chondrocyte transplantation at 3.0T: Preliminary results

To use a 3D gradient‐echo (GRE) sequence with two flip angles for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) to evaluate relative glycosaminoglycan content of repair tissue after matrix‐associated autologous chondrocyte transplantation (MACT).

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.

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.

T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study

PurposeT2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage.Materials and methodsThe knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue.ResultsThere was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX.ConclusionsWithin this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface.

Evaluation of Cartilage Repair Tissue After Matrix-Associated Autologous Chondrocyte Transplantation Using a Hyaluronic-Based or a Collagen-Based Scaffold With Morphological MOCART Scoring and Biochemical T2 Mapping Preliminary Results

Background In cartilage repair, bioregenerative approaches using tissue engineering techniques have tried to achieve a close resemblance to hyaline cartilage, which might be visualized using advanced magnetic resonance imaging. Purpose To compare cartilage repair tissue at the femoral condyle noninvasively after matrix-associated autologous chondrocyte transplantation using Hyalograft C, a hyaluronic-based scaffold, to cartilage repair tissue after transplantation using CaReS, a collagen-based scaffold, with magnetic resonance imaging using morphologic scoring and T2 mapping. Study Design Cohort study; Level of evidence, 3. Methods Twenty patients after matrix-associated autologous chondrocyte transplantation (Hyalograft C, n = 10; CaReS, n = 10) underwent 3-T magnetic resonance imaging 24 months after surgery. Groups were matched by age and defect size/localization. For clinical outcome, the Brittberg score was assessed. Morphologic analysis was applied using the magnetic resonance observation of cartilage repair tissue score, and global and zonal biochemical T2 mapping was performed to reflect biomechanical properties with regard to collagen matrix/content and hydration. Results The clinical outcome was comparable in each group. The magnetic resonance observation of cartilage repair tissue score showed slightly but not significantly (P = .210) better results in the CaReS group (76.5) compared to the Hyalograft C group (70.0), with significantly better (P = .004) constitution of the surface of the repair tissue in the CaReS group. Global T2 relaxation times (milliseconds) for healthy surrounding cartilage were comparable in both groups (Hyalograft C, 49.9; CaReS, 51.9; P = .398), whereas cartilage repair tissue showed significantly higher results in the CaReS group (Hyalograft C, 48.2; CaReS, 55.5; P = .011). Zonal evaluation showed no significant differences (P ≥ .05). Conclusion Most morphologic parameters provided comparable results for both repair tissues. However, differences in the surface and higher T2 values for the cartilage repair tissue that was based on a collagen scaffold (CaReS), compared to the hyaluronic-based scaffold, indicated differences in the composition of the repair tissue even 2 years postimplantation. Clinical Relevance In the follow-up of cartilage repair procedures using matrix-associated autologous chondrocyte transplantation, differences due to scaffolds have to be taken into account.

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.

Feasibility of T2* mapping for the evaluation of hip joint cartilage at 1.5T using a three-dimensional (3D), gradient-echo (GRE) sequence: a prospective study.

This study defines the feasibility of utilizing three‐dimensional (3D) gradient‐echo (GRE) MRI at 1.5T for T  2* mapping to assess hip joint cartilage degenerative changes using standard morphological MR grading while comparing it to delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC). MRI was obtained from 10 asymptomatic young adult volunteers and 33 patients with symptomatic femoroacetabular impingement (FAI). The protocol included T  2* mapping without gadolinium‐enhancement utilizing a 3D‐GRE sequence with six echoes, and after gadolinium injection, routine hip sequences, and a dual‐flip‐angle 3D‐GRE sequence for dGEMRIC T1 mapping. Cartilage was classified as normal, with mild changes, or with severe degenerative changes based on morphological MRI. T1 and T  2* findings were subsequently correlated. There were significant differences between volunteers and patients in normally‐rated cartilage only for T1 values. Both T1 and T  2* values decreased significantly with the various grades of cartilage damage. There was a statistically significant correlation between standard MRI and T  2* (T1) (P < 0.05). High intraclass correlation was noted for both T1 and T  2* . Correlation factor was 0.860 to 0.954 (T  2* ‐T1 intraobserver) and 0.826 to 0.867 (T  2* ‐T1 interobserver). It is feasible to gather further information about cartilage status within the hip joint using GRE T  2* mapping at 1.5T. Magn Reson Med, 2009.

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.

Comparison of delayed gadolinium enhanced MRI of cartilage (dGEMRIC) using inversion recovery and fast T1 mapping sequences.

The delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) technique has shown promising results in pilot clinical studies of early osteoarthritis. Currently, its broader acceptance is limited by the long scan time and the need for postprocessing to calculate the T1 maps. A fast T1 mapping imaging technique based on two spoiled gradient echo images was implemented. In phantom studies, an appropriate flip angle combination optimized for center T1 of 756 to 955 ms yielded excellent agreement with T1 measured using the inversion recovery technique in the range of 200 to 900 ms, of interest in normal and diseased cartilage. In vivo validation was performed by serially imaging 26 hips using the inversion recovery and the Fast 2 angle T1 mapping techniques (center T1 756 ms). Excellent correlation with Pearson correlation coefficient R2 of 0.74 was seen and Bland‐Altman plots demonstrated no systematic bias. Magn Reson Med 60:768–773, 2008.