Longitudinal quantitative MR imaging of cartilage morphology in the presence of gadopentetate dimeglumine (Gd‐DTPA)

MRI‐based cartilage morphometry can monitor cartilage loss in osteoarthritis. Intravenous Gd‐DTPA injection is needed for compositional (proteoglycan) cartilage imaging with delayed gadolinium enhanced MRI (dGEMRIC). However, longitudinal changes of cartilage morphology have not been compared in the presence and absence of Gd‐DTPA. Baseline and 2‐year follow‐up images were acquired in 41 female participants with definite medial radiographic osteoarthritis, both before and 2 h after Gd‐DTPA injection, and cartilage thickness was measured. In the absence of Gd‐DTPA, a 2.6% reduction in cartilage thickness was observed between baseline and follow‐up in the central subregion of the medial femorotibial compartment (standardized response mean [SRM] = ?0.33; P < 0.05), but only a 0.7% reduction (SRM = ?0.10; P = 0.51) in the presence of Gd‐DTPA. The findings suggest that morphometric cartilage measurement in the presence of Gd‐DTPA needs to undergo further validation, before one can recommend longitudinal dGEMRIC and morphological cartilage imaging to be performed in a single session. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Rapid 3D-T(1) mapping of cartilage with variable flip angle and parallel imaging at 3.0T

PURPOSE: To rapidly acquire T(1)-weighted images using a three-dimensional fast low angle shot (3D FLASH) sequence in combination with generalized autocalibrating partially parallel acquisitions (GRAPPA) and variable flip angle (VFA) method at 3.0T. MATERIALS AND METHODS: 3D T(1) maps of model systems (gadolinium [Gd] and agarose phantoms), bovine cartilage, and human subjects were constructed on a 3.0T clinical whole-body MR scanner. The T(1) values of model systems measured using the 2D inversion-recovery fast-spin-echo (IR-FSE) sequence were considered as a reference method to validate the rapid 3D method for comparison. RESULTS: The root mean square coefficient of variation percentage (RMS-CV%) of the median T(1) of agarose phantom across different acquisition methods was approximately 6.2%. The RMS-CV% of the median T(1) of bovine cartilage across different acquisition methods was approximately 4.1%. The RMS-CV% of median T(1) of the cartilages among the subjects was between approximately 7.3% to 11.1%. In our study, rapid 3D-T(1) mapping with VFA and parallel imaging with different acceleration factors (AFs) (AF = 1, 2, 3, and 4) seems to have no obvious influence on the T(1) mapping (before and after contrast agent administration). CONCLUSION: The preliminary results demonstrate that it is possible to quantify 3D-T(1) mapping of the whole knee joint (with 0.7 mm(3) isotropic resolution) under approximately five minutes with excellent in vivo reproducibility at 3.0T.     

Low-dose gadobenate dimeglumine versus standard-dose gadopentate dimeglumine for delayed contrast-enhanced cardiac magnetic resonance imaging

RATIONALE AND OBJECTIVES: The purpose of our study was to compare gadopentate dimeglumine (Gd-DTPA) and gadobenate dimeglumine (Gd-BOPTA) for the evaluation of myocardial infarction (MI) and in the grading transmural extent on late-contrast enhanced cardiac magnetic resonance imaging. MATERIALS AND METHODS: Twenty-three patients with clinically proven MI were examined with the use of 0.2 mmol/kg Gd-DTPA and 0.1 mmol/kg Gd-BOPTA in 2 days interval. All patients were examined with the use of segmented two-dimensional inversion-recovery turbo fast-field echo pulse sequence with an inversion time 210-300 milliseconds. Fifteen minutes time delay was used on both examinations after the injection of contrast agent. Contrast-to-noise ratio between normal myocardium and infarcted myocardium and signal intensity ratio (SIR) of the enhanced myocardium to blood pool was derived and compared for each contrast agent. RESULTS: A total of 61 infarcted segments were analyzed. All of the infarcted segments were visualized on both Gd-BOPTA and Gd-DTPA enhanced images. There was statistically no significant difference between 0.2 mmol/kg Gd-DTPA and 0.1 mmol/kg Gd-BOPTA in the mean contrast-to-noise ratio (10.19 versus 10.22; P = .96), SNR (14.29 versus 14.25; P = .96), and SIR (4.34 versus 4.21; P = .38) of the infarcted segments. Intraobserver agreement (kappa) between Gd-DTPA and Gd-BOPTA were R1 = 91% and R2 = 86%. Interobserver agreements between the readers were Gd-DTPA = 85% and Gd-BOPTA = 88%. CONCLUSION: According to our data, the diagnostic efficacy of 0.1 mmol/kg dose Gd-BOPTA is equivalent to that of 0.2 mmol/kg Gd-DTPA for the assessment of MI on delayed enhanced magnetic resonance images.     

In vivo transport of Gd-DTPA(2-) in human knee cartilage assessed by depth-wise dGEMRIC analysis

Purpose:

To investigate the transport of Gd‐DTPA^2? in different layers of femoral knee cartilage in vivo.

Materials and Methods:

T₁ measurements (1.5 Tesla) were performed in femoral knee cartilage of 23 healthy volunteers. The weight‐bearing central cartilage was analyzed before contrast and at eight time points after an intravenous injection of Gd‐DTPA^2?: 12–60 min (4 volunteers) and 1–4 h (19 volunteers). Three regions of interest were segmented manually: deep, middle, and superficial.

Results:

Before contrast injection, a depth‐wise variation of T₁ was observed with 50% higher values in the superficial region compared with the deep region. In the deep region, the uptake of Gd‐DTPA^2? was not detected until 36 min and the concentration increased until 240 min, whereas in the superficial region, the uptake was seen already at 12 min and the concentration decreased after 180 min (P < 0.01). There was a difference between medial and lateral compartment regarding bulk, but not superficial Gd‐DTPA^2? concentration. The bulk gadolinium concentration was negatively related to the cartilage thickness (r = ?0.68; P < 0.01).

Conclusion:

The depth‐wise and thickness dependent variations in Gd‐DTPA² transport influence the interpretation of bulk dGEMRIC analysis in vivo. In thick cartilage, incomplete penetration of Gd‐DTPA² will yield a falsely too long T₁. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

     

T2 of articular cartilage in the presence of Gd-DTPA2-.

T(2) information and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) are both used to characterize articular cartilage. They are currently obtained in separate studies because Gd-DTPA(2-) (which is needed for dGEMRIC) affects the inherent T(2) information. In this study, T(2) was simulated and then measured at 8.45 T in 20 sections from two human osteochondral samples equilibrated with and without Gd-DTPA(2-). Both the simulations and data demonstrated that Gd-DTPA(2-) provides a non-negligible mechanism for relaxation, especially with higher (1 mM) equilibrating Gd-DTPA(2-) concentrations, and in areas of tissue with high T(2) (due to weak inherent T(2) mechanisms) and high tissue Gd-DTPA(2-) (due to a low glycosaminoglycan concentration). Nonetheless, T(2)-weighted images of cartilage equilibrated in 1 mM Gd-DTPA(2-) showed similar T(2) contrast with and without Gd-DTPA(2-), demonstrating that the impact on T(2) was not great enough to affect identification of T(2) lesions. However, T(2) maps of the same samples showed loss of conspicuity of T(2) abnormalities. We back-calculated inherent T(2)'s (T(2,bc)) using a T(2)-relaxivity value from a 20% protein phantom (r(2) = 9.27 +/- 0.09 mM(-1)s(-1)) and the Gd-DTPA(2-) concentration calculated from T(1,Gd). The back-calculation restored the inherent T(2) conspicuity, and a correlation between T(2) and T(2,bc) of r = 0.934 (P < 0.0001) was found for 80 regions of interest (ROIs) in the sections. Back-calculation of T(2) is therefore a viable technique for obtaining T(2) maps at high equilibrating Gd-DTPA(2-) concentrations. With T(2)-weighted images and/or low equilibrating Gd-DTPA(2-) concentrations, it may be feasible to obtain both T(2) and dGEMRIC information in the presence of Gd-DTPA(2-) without such corrections. These conditions can be designed into ex vivo studies of cartilage. They appear to be applicable for clinical T(2) studies, since pilot clinical data at 1.5 T from three volunteers demonstrated that calculated T(2) maps are comparable before and after "double dose" Gd-DTPA(2-) (as utilized in clinical dGEMRIC studies). Therefore, it may be possible to perform a comprehensive clinical examination of dGEMRIC, T(2), and cartilage volume in one scanning session without T(2) data correction.     

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) in early knee osteoarthritis.

Delayed contrast-enhanced MRI of cartilage (dGEMRIC) is a noninvasive technique to study cartilage glycosaminoglycan (GAG) content in vivo. This study evaluates dGEMRIC in patients with preradiographic degenerative cartilage changes. Seventeen knees in 15 patients (age 35-70) with arthroscopically verified cartilage changes (softening and fibrillations) in the medial or lateral femoral compartment, knee pain, and normal weight-bearing radiography were included. MRI (1.5 T) was performed precontrast and at 1.5 and 3 hr after an intravenous injection of Gd-DTPA(2-) at 0.3 mmol/kg body weight. T(1) measurements were made in regions of interest in medial and lateral femoral cartilage using sets of five turbo inversion recovery images. Precontrast, R(1) (R(1) = 1/T(1), 1/s) was slightly lower in diseased compared to reference compartment, indicating increased hydration (P = 0.01). Postcontrast, R(1) was higher in diseased than in reference compartment at 1.5 hr, 3.45 +/- 0.90 and 2.64 +/- 0.58 (mean +/- SD), respectively (P < 0.01), as well as at 3 hr, 2.94 +/- 0.60 and 2.50 +/- 0.37, respectively (P = 0.01). The washout of the contrast medium was faster in diseased cartilage as shown by a higher R(1) at 1.5 than at 3 hr in the diseased but not in the reference compartment. In conclusion, dGEMRIC can identify GAG loss in early stage cartilage disease with a higher sensitivity at 1.5 than 3 hr.     

Parallel imaging of knee cartilage at 3 Tesla

PURPOSE: To evaluate the feasibility and reproducibility of quantitative cartilage imaging with parallel imaging at 3T and to determine the impact of the acceleration factor (AF) on morphological and relaxation measurements. MATERIALS AND METHODS: An eight-channel phased-array knee coil was employed for conventional and parallel imaging on a 3T scanner. The imaging protocol consisted of a T2-weighted fast spin echo (FSE), a 3D-spoiled gradient echo (SPGR), a custom 3D-SPGR T1rho, and a 3D-SPGR T2 sequence. Parallel imaging was performed with an array spatial sensitivity technique (ASSET). The left knees of six healthy volunteers were scanned with both conventional and parallel imaging (AF = 2). RESULTS: Morphological parameters and relaxation maps from parallel imaging methods (AF = 2) showed comparable results with conventional method. The intraclass correlation coefficient (ICC) of the two methods for cartilage volume, mean cartilage thickness, T1rho, and T2 were 0.999, 0.977, 0.964, and 0.969, respectively, while demonstrating excellent reproducibility. No significant measurement differences were found when AF reached 3 despite the low signal-to-noise ratio (SNR). CONCLUSION: The study demonstrated that parallel imaging can be applied to current knee cartilage quantification at AF = 2 without degrading measurement accuracy with good reproducibility while effectively reducing scan time. Shorter imaging times can be achieved with higher AF at the cost of SNR.     

Delayed contrast enhanced MRI of meniscus with ionic and non-ionic agents

Purpose:

To evaluate the potential difference in post‐contrast T₁ relaxation time of the meniscus (T_1Gd) between osteoarthritic patients (OA) and healthy subjects (HS), and to verify if charge density has any influence on meniscal T_1Gd.

Materials and Methods:

We performed a retrospective analysis of meniscal T₁ relaxation time on data previously acquired for studying articular cartilage with both ionic and non‐ionic contrast media. MR imaging was performed in 10 OA and 8 HS at 120 min following administration of double‐dose ionic Gd‐DTPA^2? on one day and non‐ionic Gd‐DTPA‐BMA on a different day. A three‐dimensional Look‐Locker sequence with echo time of 2 ms was used for data acquisition to allow T₁ mapping of the meniscus.

Results:

Compared with HS, significantly lower meniscal T_1Gd was observed in OA with either ionic Gd‐DTPA^2? (P < 0.01) or non‐ionic Gd‐DTPA‐BMA (P < 0.001) contrast agent. There was a correlation between meniscal T₁(Gd‐DTPA^2?) versus T₁(Gd‐DTPA‐BMA). Meniscal T₁(Gd‐DTPA‐BMA) showed a larger difference and smaller overlap between OA and HS. No significant differences in either pre‐contrast T₁ or post‐contrast T_1Gd were observed between inner and outer zones of the meniscus with either agent.

Conclusion:

Significant differences in meniscal T_1Gd between OA and HS were observed with both ionic and non‐ionic contrast agents, suggesting that charge density is not responsible for the observed differences. J. Magn. Reson. Imaging 2011;33:731–735. © 2011 Wiley‐Liss, Inc.

     

Three-dimensional delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) at 1.5T and 3.0T

PURPOSE: To implement and validate a three-dimensional (3D) T1 measurement technique that is suitable for delayed gadolinium (Gd)-enhanced MRI of cartilage (dGEMRIC) and can be easily implemented with clinically available pulse sequences at 1.5T and 3.0T. MATERIALS AND METHODS: A 3D inversion-recovery prepared spoiled gradient-echo (IR-SPGR) imaging pulse sequence with variable TR was used to implement a 3D T1 measurement protocol. The 3D T1 measurements were validated against a gold-standard single-slice 2D IR T1 measurement protocol in both phantoms and in vivo, in both asymptomatic volunteers and volunteers with osteoarthritis (OA). RESULTS: T1 measurements in phantoms showed a statistically significant correlation between the 2D and 3D measurements at 1.5T (R2=0.993, P<0.001) and 3.0T (R2=0.996, P<0.001). In vivo application demonstrated the feasibility of using this 3D IR-SPGR sequence to evaluate the molecular status of articular cartilage throughout the knee joint with 0.63x0.63x3.0 mm spatial resolution within a 20-minute acquisition, even with the measurement parameters set for the higher T1(Gd) of cartilage at 3T (range=400-900 msec mean T1 within a region of interest (ROI) in cartilage, compared to 200-600 msec mean T1 at 1.5T). CONCLUSION: This 3D T1 measurement protocol may prove useful for the evaluation and follow-up of cartilage dGEMRIC indices in clinical studies of OA.     

Differentiating normal hyaline cartilage from post-surgical repair tissue using fast gradient echo imaging in delayed gadolinium-enhanced MRI (dGEMRIC) at 3 Tesla

The purpose was to evaluate the relative glycosaminoglycan (GAG) content of repair tissue in patients after microfracturing (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) of the knee joint with a dGEMRIC technique based on a newly developed short 3D-GRE sequence with two flip angle excitation pulses. Twenty patients treated with MFX or MACT (ten in each group) were enrolled. For comparability, patients from each group were matched by age (MFX: 37.1 ± 16.3 years; MACT: 37.4 ± 8.2 years) and postoperative interval (MFX: 33.0 ± 17.3 months; MACT: 32.0 ± 17.2 months). The Δ relaxation rate (ΔR1) for repair tissue and normal hyaline cartilage and the relative ΔR1 were calculated, and mean values were compared between both groups using an analysis of variance. The mean ΔR1 for MFX was 1.07 ± 0.34 versus 0.32 ± 0.20 at the intact control site, and for MACT, 1.90 ± 0.49 compared to 0.87 ± 0.44, which resulted in a relative ΔR1 of 3.39 for MFX and 2.18 for MACT. The difference between the cartilage repair groups was statistically significant. The new dGEMRIC technique based on dual flip angle excitation pulses showed higher GAG content in patients after MACT compared to MFX at the same postoperative interval and allowed reducing the data acquisition time to 4 min.     

应用磁共振生理学成像定量测定兔膝关节软骨退变的研究

目的：探讨磁共振生理学成像技术在检测关节软骨退变中的应用价值。方法：20只新西兰大白兔随机分为甲、乙、丙、丁四组。甲组左膝关节行常规磁共振成像后即刻处死,取股骨髁软骨行苏木素和伊红染色（hematoxylln and eosin,HE）、阿利辛兰染色（alcian blue,AB）及蛋白多糖含量测定。乙、丙、丁各组每只兔左膝关节内注射0．2na（10U）木瓜蛋白酶,并于注射前及注射后分别于24、48、72h先行相同常规磁共振成像及磁化传递对比成像（magnetization transfer contrast。MTC）,后行磁共振延迟增强软骨成像（delayed gadolimum enhanced MRI of cartilage,dGEMRIC）,测定关节软骨磁化传递率和L驰豫时间值。扫描结束后处死动物,取左膝股骨髁部软骨行大体观察、HE、AB染色及蛋白多糖含量测定。结果：注射木瓜蛋白酶后24、48h,蛋白多糖含量与甲组比较,统计学均有差异（P=0．048和0．045,P〈0．05）,注射后72h,统计学没有差异（P=0．455,P〉0．05）。注射木瓜蛋白酶后24、48、72h的T1弛豫率分别降低了316．09ms、244．01ms和143．98ms,注射后24、48h与注射前比较有统计学差异（P=0．047和0．045,P〈0．05）。注射木瓜蛋白酶前后相比,各组关节软骨磁化传递率不同程度地降低,但均没有统计学差异。结论：本研究采用的dGEMRIC、MTC成像技术能够通过定量检测T1弛豫时间值、磁化传递率反映软骨退变早期的生化改变。     

Strain‐dependent T1 relaxation profiles in articular cartilage by MRI at microscopic resolutions

To investigate the dependency of T₁ relaxation on mechanical strain in articular cartilage, quantitative magnetic resonance T₁ imaging experiments were carried out on cartilage before/after the tissue was immersed in gadolinium contrast agent and when the tissue was being compressed (up to ～48% strains). The spatial resolution across the cartilage depth was 17.6 μm. The T₁ profile in native tissue (without the presence of gadolinium ions) was strongly strain‐dependent, which is also depth‐dependent. At the modest strains (e.g., 14% strain), T₁ reduced by up to 68% in the most surface portion of the tissue. Further compression (e.g., 45% strain) reduced T₁ mostly in the middle and deep portions of the tissue. For the gadolinium‐immersed tissue, both modest and heavy compressions (up to 48% strain) increased T₁ slightly but significantly, although the overall shapes of the T₁ profiles remained approximately the same regardless of the amount of strains. The complex relationships between the T₁ profiles and the mechanical strains were a direct consequence of the depth‐dependent proteoglycan concentration in the tissue, which determined the tissue's mechanical properties. This finding has potential implications in the use of gadolinium contrast agent in clinical magnetic resonance imaging of cartilage (the dGEMRIC procedure), when the loading or loading history of patients is considered. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Variable flip angle‐based fast three‐dimensional T1 mapping for delayed gadolinium‐enhanced MRI of cartilage of the knee: Need for B1 correction

Delayed gadolinium‐enhanced MRI of cartilage is a technique, which involves T₁ mapping to identify changes in the structural integrity of cartilage associated with osteoarthritis. Currently, the gold standard is 2D inversion recovery turbo spin echo, which suffers from long acquisition times and limited coverage. Three‐dimensional variable flip angle (VFA) is an alternate technique, which has been shown to be accurate when an estimate of T₁ is available a priori. This study validates the variable flip angle method for delayed gadolinium‐enhanced MRI of cartilage of the femoro‐tibial knee cartilage. When amplitude of (excitation) radiofrequency field inhomogeneities were minimized using nonselective pulses and amplitude of (excitation) radiofrequency field correction using an additional acquisition of a amplitude of (excitation) radiofrequency field map, the accuracy of T₁ measurements were improved, and slice‐to‐slice variations over the 3D volume were minimized. In conclusion, fast 3D T₁ mapping using the variable flip angle method with amplitude of (excitation) radiofrequency field correction appears to be an efficient and accurate method for delayed gadolinium‐enhanced MRI of cartilage of the knee. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

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

PURPOSE: 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). MATERIALS AND METHODS: In a phantom study, T1-mapping based on a 3D-GRE sequence with different flip angle combinations was compared with a standard inversion recovery (IR) sequence at 3.0T. Fifteen patients were examined after MACT in the knee at "3-13 months" (group I) and "19-42 months" (group II). The delta relaxation rate (deltaR1) calculated for repair tissue and normal hyaline cartilage was measured and mean values were compared in different postoperative intervals using analysis of variance. RESULTS: The flip angle combination 35/10 degrees provided the best agreement with IR sequence for short and long T1 values. The mean deltaR1 for repair tissue was 2.49 versus 1.04 at the intact control site in group I and 1.90 compared with 0.81 in group II. Differences from repair tissue to control sites showed statistically significance for both groups; no significant difference was found between groups. CONCLUSION: The 3D dual flip angle dGEMRIC technique optimized for cartilage imaging is comparable to standard T1 IR technique for T1 mapping. Furthermore, the preliminary in vivo study demonstrates the feasibility of the technique in the evaluation of MACT patients.     

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), after slipped capital femoral epiphysis

Objective

The aim of this study was to assess the glycosaminoglycan (GAG) content in hip joint cartilage in mature hips with a history of slipped capital femoral epiphysis (SCFE) using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC).

Methods

28 young-adult subjects (32 hips) with a mean age of 23.8 ± 4.0 years (range: 18.1-30.5 years) who were treated for mild or moderate SCFE in adolescence were included into the study. Hip function and clinical symptoms were evaluated with the Harris hip score (HHS) system at the time of MRI. Plain radiographic evaluation included Tonnis grading, measurement of the minimal joint space width (JSW) and alpha-angle measurement. The alpha-angle values were used to classify three sub-groups: group 1 = subjects with normal femoral head-neck offset (alpha-angle <50°), group 2 = subjects with mild offset decrease (alpha-angle 50°-60°), and group 3 = subjects with severe offset decrease (alpha-angle >60°).

Results

There was statistically significant difference noted for the T1_Gd values, lateral and central, between group 1 and group 3 (p-values = 0.038 and 0.041). The T1_Gd values measured within the lateral portion were slightly lower compared with the T1_Gd values measured within the central portion that was at a statistically significance level (p-value <0.001). HHS, Tonnis grades and JSW revealed no statistically significant difference.

Conclusion

By using dGEMRIC in the mid-term follow-up of SCFE we were able to reveal degenerative changes even in the absence of joint space narrowing that seem to be related to the degree of offset pathology. The dGEMRIC technique may be a potential diagnostic modality in the follow-up evaluation of SCFE.     

Delayed contrast‐enhanced MRI of cartilage: Comparison of nonionic and ionic contrast agents

The objective of this study was to evaluate if cartilage fixed charge density is the only factor determining the distribution of the measured delayed gadolinium‐enhanced magnetic resonance imaging of cartilage index, T₁(Gd‐DTPA^2?), across cartilage in the clinical delayed gadolinium‐enhanced magnetic resonance imaging of cartilage protocol. Nineteen subjects with osteoarthritis and 14 controls were included. Cartilage T₁(Gd) was measured following administration of 0.2 mmol kg^?1 of nonionic (Gd‐DTPA‐BMA) and, at a different date, anionic (Gd‐DTPA^2?). T₁(Gd‐DTPA‐BMA) was plotted against T₁(Gd‐DTPA^2?); a slope of 0 would indicate domination by charge effects; a nonzero slope would suggest that other factors influence T₁(Gd‐DTPA‐BMA), and hence potentially T₁(Gd‐DTPA^2?). The low slope of the curve found in osteoarthritis subjects (0.31) indicates that Gd‐DTPA‐BMA penetrated most osteoarthritis cartilage to the same extent, and T₁(Gd‐DTPA‐BMA) did not differentiate cartilages, which were differentiated by T₁(Gd‐DTPA^2?). The higher slopes in control subjects (0.88) are possibly due to inhibited transport of contrast agent into healthier cartilage, potentially exaggerated by the fast body clearance of the nonionic contrast agent. Overall, the use of anionic Gd‐DTPA^2? for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage is indicated for better discrimination of the health status of cartilage. Future studies could be designed to use contrast‐enhanced dynamics to understand the transport properties of tissues in the joint and to evaluate the concentration of tissue constituents. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Suitability of T(1Gd) as the dGEMRIC index at 1.5T and 3.0T.

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is based on the theory that Gd-DTPA(2-) will distribute in inverse relation to cartilage glycosaminoglycan (GAG). T(1Gd) (T(1) after penetration of a 0.2 mmol/kg dose of Gd-DTPA(2-)) has been used as the dGEMRIC index, although (1/T(1Gd)-1/T(1o)) should be more representative of Gd-DTPA(2-) concentration (where T(1o) = T(1) before contrast). T(1o) and T(1Gd) were measured in 20 volunteers at both 1.5T and 3T and the correlation between the metrics of T(1Gd) and (1/T(1Gd)-1/T(1o)) was calculated. There was a high correlation coefficient between the two metrics at both field strengths, with R = 0.94, 0.93, and 0.90 for central medial femur, posterior medial femur, and medial tibia, respectively, at 1.5T and 0.87, 0.94, 0.96 at 3T. In all cases P < 0.0001. Therefore, these data suggest that, for native cartilage, the current practice of measuring T(1Gd) (but not also T(1o)) is adequate at both 1.5T and 3T.     

Cartilage morphology at 3.0T: Assessment of three‐dimensional magnetic resonance imaging techniques

Purpose:

To compare six new three‐dimensional (3D) magnetic resonance (MR) methods for evaluating knee cartilage at 3.0T.

Materials and Methods:

We compared: fast‐spin‐echo cube (FSE‐Cube), vastly undersampled isotropic projection reconstruction balanced steady‐state free precession (VIPR‐bSSFP), iterative decomposition of water and fat with echo asymmetry and least‐squares estimation combined with spoiled gradient echo (IDEAL‐SPGR) and gradient echo (IDEAL‐GRASS), multiecho in steady‐state acquisition (MENSA), and coherent oscillatory state acquisition for manipulation of image contrast (COSMIC). Five‐minute sequences were performed twice on 10 healthy volunteers and once on five osteoarthritis (OA) patients. Signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) were measured from the volunteers. Images of the five volunteers and the five OA patients were ranked on tissue contrast, articular surface clarity, reformat quality, and lesion conspicuity. FSE‐Cube and VIPR‐bSSFP were compared to IDEAL‐SPGR for cartilage volume measurements.

Results:

FSE‐Cube had top rankings for lesion conspicuity, overall SNR, and CNR (P < 0.02). VIPR‐bSSFP had top rankings in tissue contrast and articular surface clarity. VIPR and FSE‐Cube tied for best in reformatting ability. FSE‐Cube and VIPR‐bSSFP compared favorably to IDEAL‐SPGR in accuracy and precision of cartilage volume measurements.

Conclusion:

FSE‐Cube and VIPR‐bSSFP produce high image quality with accurate volume measurement of knee cartilage. J. Magn. Reson. Imaging 2010;32:173–183. © 2010 Wiley‐Liss, Inc.     

Magnetic resonance imaging of knee cartilage using a water selective balanced steady-state free precession sequence

PURPOSE: To compare an optimized water selective balanced steady-state free precession sequence (WS-bSSFP) with conventional magnetic resonance (MR) sequences in imaging cartilage of osteoarthritic knees. MATERIALS AND METHODS: Flip angles of sagittal and axial WS-bSSFP sequences were optimized in three volunteers. Subsequently, the knees of 10 patients with generalized osteoarthritis were imaged using sagittal and axial WS-bSSFP and conventional MR imaging techniques. We calculated contrast-to-noise ratios (CNR) between cartilage and its surrounding tissues to quantitatively analyze the various sequences. Using dedicated software we compared, in two other patients, the accuracy of cartilage volume measurements with anatomic sections of the tibial plateau. RESULTS: CNRtotal eff (CNR efficiency between cartilage and its surrounding tissue) using WS-bSSFP was maximal with a 20-25 degrees flip angle. CNRtotal eff was higher in WS-bSSFP than in conventional images: 6.1 times higher compared to T1-weighted gradient echo (GE) images, 5.1 compared to proton-density (PD) fast spin echo (FSE) images, and 4.8 compared to T2-weighted FSE images. The mean difference of cartilage volume measurement on WS-bSSFP and anatomic sections was 0.06 mL compared to 0.24 mL for T1-GE and anatomic sections. CONCLUSION: A WS-bSSFP sequence is superior to conventional MR imaging sequences in imaging cartilage of the knee in patients with osteoarthritis.