Delayed gadolinium-enhanced magnetic resonance imaging (dGEMRIC) of hip joint cartilage: better cartilage delineation after intra-articular than intravenous gadolinium injection

PURPOSE: To investigate and compare delayed gadolinium (Gd-DTPA)-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) in the hip joint using intravenous (i.v.) or ultrasound-guided intra-articular (i.a.) Gd-DTPA injection. MATERIAL AND METHODS: In 10 patients (50% males, mean age 58 years) with clinical and radiographic hip osteoarthritis (OA; Kellgren score II-III), MRI of the hip was performed twice on a clinical 1.5T MR scanner: On day 1, before and 90-180 min after 0.3 mmol/kg body weight i.v. Gd-DTPA and, on day 8, 90-180 min after ultrasound-guided i.a. injection of a 4 mmol/l Gd-DTPA solution. Coronal STIR, coronal T1 fat-saturated spin-echo, and a cartilage-sensitive gradient-echo sequence (3D T1 SPGR) in the sagittal plane were applied. RESULTS Both the post-i.v. and post-i.a. Gd-DTPA images showed significantly higher signal-to-noise (SNR) and contrast-to-noise (CNR) in the joint cartilage compared to the non-enhanced images (P < 0.002). I.a. Gd-DTPA provided significantly higher SNR and CNR compared to i.v. Gd-DTPA (P < 0.01). Furthermore, a better delineation of the cartilage in the synovial/cartilage zone and of the chondral/subchondral border was observed. CONCLUSION: The dGEMRIC MRI method markedly improved delineation of hip joint cartilage compared to non-enhanced MRI. The i.a. Gd-DTPA provided the best cartilage delineation. dGEMRIC is a clinically applicable MRI method that may improve identification of early subtle cartilage damage and the accuracy of volume measurements of hip joint cartilage.     

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.     

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.     

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.     

dGEMRIC (delayed gadolinium-enhanced MRI of cartilage) indicates adaptive capacity of human knee cartilage.

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is a new imaging technique to estimate joint cartilage glycosaminoglycan content by T1-relaxation time measurements after penetration of the hydrophilic contrast agent Gd-DTPA(2-). This study compares dGEMRIC in age-matched healthy volunteers with different levels of physical activity: Group 1 (n = 12): nonexercising individuals; Group 2 (n = 16): individuals with physical exercise averaging twice weekly; Group 3 (n = 9): male elite runners. dGEMRIC was performed 2 hr after an intravenous injection of Gd-DTPA(2-) at 0.3 mmol/kg body weight. T1 differed significantly between the three different levels of physical exercise. T1 values (mean of medial and lateral femoral cartilage) for Groups 1, 2, and 3 were: 382 +/- 33, 424 +/- 22 and 476 +/- 36, respectively (ms, mean +/- SD) (P = 0.0004, 1 vs. 2 and 0.0002, 2 vs. 3). Irrespective of the exercise level, T1 was longer in lateral compared to medial femoral cartilage (P = 0.00005; n = 37). In conclusion, this cross-sectional study indicates that human knee cartilage adapts to exercise by increasing the glycosaminoglycan content. Furthermore, results suggest a compartmental difference within the knee with a higher glycosaminoglycan content in lateral compared to medial femoral cartilage. A higher proportion of extracellular water, i.e., larger distribution volume, may to some extent explain the high T1 in the elite runners.     

Accuracy of T1 measurement with 3-D Look-Locker technique for dGEMRIC

PURPOSE: To validate the accuracy of T1 measurement by three-dimensional Look-Locker method (3D LL) for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of human subjects with and without osteoarthritis (OA), as compared with two-dimensional inversion recovery fast spin-echo (2D IR-FSE) technique. MATERIALS AND METHODS: MR sagittal images of the knees were acquired for T1 mapping in 29 subjects with standard 2D IR-FSE and 3D LL sequences 90-135 min following administration of 0.2 mmol/kg Gd-DTPA(2-). T1 maps of femoral and tibial cartilage were generated using custom software. Comparisons in T1 values between the two techniques were performed using regression analysis. RESULTS: Good agreement in T1 values between 2D IR-FSE and 3D LL was observed (R values of 0.90, and 0.85, and 0.86 for all, OA, and control subjects, respectively) when acquired within 15 min. CONCLUSION: The 3D LL sequence provides accurate T1 estimates of articular cartilage with advantages of entire joint coverage, shorter acquisition time, and a wide range of inversion times sampled within a single acquisition.     

Relaxivity and diffusion of gadolinium agents in cartilage.

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

Reproducibility of dGEMRIC in assessment of hip joint cartilage: A prospective study

Purpose

To investigate the reproducibility of dGEMRIC in the assessment of cartilage health of the adult asymptomatic hip joint.

Materials and Methods

Fifteen asymptomatic volunteers (mean age, 26.3 years ± 3.0) were preliminarily studied. Any volunteer that was incidentally diagnosed with damaged cartilage on MRI (n = 5) was excluded. Ten patients that had no evidence of prior cartilage damage (mean age, 26.2 years ± 3.4) were evaluated further in this study. The reproducibility of dGEMRIC was assessed with two T1_Gd exams performed 4 weeks apart in these volunteers. The protocol involved an initial standard MRI to confirm healthy cartilage, which was then followed by dGEMRIC. The second scan included only the repeat dGEMRIC. Region of interest (ROI) analyses for T1_Gd‐measurement was performed in seven radial reformats. Statistical analysis included the student's t‐test and intra‐class correlation (ICC) measurement to assess reproducibility.

Results

Overall 70 ROIs were studied. Mean cartilage T1_Gd values at various loci ranged from 560.9 ms to 684.4 ms at the first set of readings and 551.5 ms to 662.2 ms in the second one. The mean difference per region of interest between the two T1_Gd‐measurements ranged from 21.4 ms (3.7%) to 45.0 ms (6.8%), which was not found to be statistically significant (P = 0.153). There was a high reproducibility detected (ICC range, 0.667–0.915). Intra‐ and Inter‐observer analyses proved a high agreement for T1_Gd assessment (0.973 and 0.932).

Conclusion

We found dGEMRIC to be a reliable tool in the assessment of cartilage health status in adult hip joints. J. Magn. Reson. Imaging 2009;30:224–228. © 2009 Wiley‐Liss, Inc.     

Three-dimensional delayed gadolinium-enhanced magnetic resonance imaging of hip joint cartilage at 3T: A prospective controlled study

Purpose

To assess acetabular and femoral hip joint cartilage with three-dimensional (3D) delayed gadolinium-enhanced magnetic resonance imaging (dGEMRIC) in patients with degeneration of hip joint cartilage and asymptomatic controls with morphologically normal appearing cartilage.

Methods and materials

A total of 40 symptomatic patients (18 males, 22 females; mean age: 32.8 ± 10.2 years, range: 18–57 years) with different hip joint deformities including femoroacetabular impingement (n = 35), residual hip dysplasia (n = 3) and coxa magna due to Legg–Calve–Perthes disease in childhood (n = 2) underwent high-resolution 3D dGEMRIC for the evaluation of acetabular and femoral hip joint cartilage. Thirty-one asymptomatic healthy volunteers (12 males, 19 females; mean age: 24.5 ± 1.8 years, range: 21–29 years) without underlying hip deformities were included as control. MRI was performed at 3 T using a body matrix phased array coil. Region of interest (ROI) analyses for T1_Gd assessment was performed in seven regions in the hip joint, including anterior to superior and posterior regions.

Results

T1_Gd mapping demonstrated the typical pattern of acetabular cartilage consistent with a higher glycosaminoglycan (GAG) content in the main weight-bearing area. T1_Gd values were significantly higher in the control group than in the patient group whereas significant differences in T1_Gd values corresponding to the amount of cartilage damage were noted both in the patient group and in the control group.

Conclusions

Our study demonstrates the potential of high-resolution 3D dGEMRIC at 3 T for separate acetabular and femoral hip joint cartilage assessment in various forms of hip joint deformities.     

Feasibility and reproducibility of relaxometry, morphometric, and geometrical measurements of the hip joint with magnetic resonance imaging at 3T

PURPOSE: To test the feasibility of in vivo magnetic resonance T(1rho) relaxation time measurements of hip cartilage, and quantify the reproducibility of hip cartilage thickness, volume, T(2), T(1rho), and size of femoral head measurements. MATERIALS AND METHODS: The hip joint of five human healthy volunteers, one subject with mild hip osteoarthritis (OA) and one subject with advanced hip OA, was imaged with magnetic resonance imaging (MRI) at 3T. Hip cartilage thickness, volume, T(1rho), and T(2) were quantified, as well as the size of the femoral head. All imaging and analysis procedures were performed twice for the healthy volunteers to assess reproducibility. RESULTS: In vivo MR T(1rho) measurements of hip cartilage at 3T were feasible as demonstrated by high quality images and relaxation time maps. High levels of reproducibility were obtained for measurements of hip cartilage thickness (CV(SD) = 2.19%), volume (CV(SD) = 3.5%), T(2) (CV(SD) = 5.89%), T(1rho) (CV(SD) = 2.03%), and size of femoral head (CV(SD) = 0.49%). Mean T(2) and T(1rho) relaxation time values for human healthy subjects were 28.38 (+/-2.66) msec and 38.72 (+/-3.84) msec, respectively. Mean T(2) and T(1rho) relaxation time values for subjects with OA were 34.78 (+/-8.36) msec and 44.07 (+/-0.99) msec, respectively. T(2) and T(1rho) values increased from the deep to the superficial layers. CONCLUSION: Qualitative and quantitative results indicate that the MRI techniques presented in this study may be applied clinically to patients with OA of the hip to investigate these parameters at different stages of disease.     

Cartilage quality in rheumatoid arthritis: comparison of T2* mapping, native T1 mapping, dGEMRIC, ΔR1 and value of pre-contrast imaging

Purpose

To prospectively evaluate four non-invasive markers of cartilage quality—T2* mapping, native T1 mapping, dGEMRIC and ΔR1—in healthy volunteers and rheumatoid arthritis (RA) patients.

Materials and methods

Cartilage of metacarpophalangeal (MCP) joints II were imaged in 28 consecutive subjects: 12 healthy volunteers [9 women, mean (SD) age 52.67 (9.75) years, range 30–66] and 16 RA patients with MCP II involvement [12 women, mean (SD) age 58.06 (12.88) years, range 35–76]. Sagittal T2* mapping was performed with a multi-echo gradient-echo on a 3?T MRI scanner. For T1 mapping the dual flip angle method was applied prior to native T1 mapping and 40?min after gadolinium application (delayed gadolinium-enhanced MRI of cartilage, dGEMRIC, T1_Gd). The difference in the longitudinal relaxation rate induced by gadolinium (ΔR1) was calculated. The area under the receiver operating characteristic curve (AROC) was used to test for differentiation of RA patients from healthy volunteers.

Results

dGEMRIC (AUC 0.81) and ΔR1 (AUC 0.75) significantly differentiated RA patients from controls. T2* mapping (AUC 0.66) and native T1 mapping (AUC 0.66) were not significantly different in RA patients compared to controls.

Conclusions

The data support the use of dGEMRIC for the assessment of MCP joint cartilage quality in RA. T2* and native T1 mapping are of low diagnostic value. Pre-contrast T1 mapping for the calculation of ΔR1 does not increase the diagnostic value of dGEMRIC.     

In vivo qualitative assessments of articular cartilage in the rabbit knee with high-resolution MRI at 3 T.

Proteoglycan (PG) loss and disruption of the collagen framework in cartilage are early events associated with osteoarthritis (OA). The feasibility of in vivo high-resolution MRI assessments probing both macromolecules was explored in articular cartilage of the rabbit knee. One-millimeter thick coronal images were obtained at 3 T with a 97 x 97 microm(2) pixel size. A 22% decrease in the magnetization transfer (MT) exchange rate along with an approximately 2-fold greater Gd(DTPA)(2-)-induced decrease in T(1) relaxation time were measured in response to papain injection 1 day prior to the MRI session, indicative of an alteration of collagen integrity and PG depletion, respectively. A two-point method was tested as an alternative to the more time-consuming multipoint method typically used to measure T(1) changes. Kinetics of Gd(DTPA)(2-) uptake were observed with a 10-min time resolution. The diffusive transport of Gd(DTPA)(2-) was characterized by a T(1) decrease approximately 2-fold faster in papain-treated knees. These data suggest that kinetics of tracer diffusion may be used as an informative marker of PG loss, in addition to the amplitude of T(1) variations. When applied to a relevant OA model, the combination of MT and Gd(DTPA)(2-)-MRI may help in identifying new active compounds during efficacy studies on cartilage protection.     

Three-dimensional T1 mapping for dGEMRIC at 3.0 T using the Look Locker method

OBJECTIVE: The objective of this study was to implement a three-dimensional (3-D) T1 mapping sequence (3DLL) at 3.0 T for dGEMRIC based on the Look Locker scheme. MATERIALS AND METHODS: Because all current reports on dGEMRIC are at 1.5 T and mostly using 2-D IR fast spin echo (FSE), data were acquired at 1.5 T and 3.0 T with both 3DLL and 2-D IR-FSE sequence. Phantoms with different concentrations of Gd(DTPA) were used and seven subjects (three asymptomatic, four symptomatic) were scanned using the dGEMRIC technique. RESULTS: The T1 measurements obtained on the phantom with 3DLL show very good agreement with those acquired with 2-D IR-FSE. Using a two-tailed paired t test, the T1 (Gd) measurements in two sections obtained in all subjects with both sequences were found to be statistically indistinguishable at either field strength (P = 0.07 at 1.5 T and P = 0.07 at 3.0 T). CONCLUSIONS: The preliminary data presented here suggest that the 3DLL sequence provides accurate T1 values with sufficient in-plane resolution and allows full joint coverage in less than 10 minutes.     

Dynamic contrast-enhanced MRI of the pancreas: initial results in healthy volunteers and patients with chronic pancreatitis

PURPOSE: To characterize pancreatic perfusion in volunteers and patients with chronic pancreatitis (CP) by dynamic contrast-enhanced (DCE) MRI. MATERIALS AND METHODS: Pancreatic enhancement after bolus injection of Gd-DTPA with a three-dimensional ultrafast partial-Fourier radiofrequency (RF) spoiled gradient-echo (GE) acquisition was examined prospectively. An acquisition volume of the pancreatic parenchyma was obtained every 4.2 seconds during a single breath-hold in 31 volunteers and 19 patients with CP. We calculated the wash-in rate and a newly defined parameter, the "time-to-inflow deceleration" (TID). A statistical analysis of the differences between both groups was performed with the use of Student's t-test. RESULTS: Significant differences in the TID and wash-in rate were found for the head and body of the pancreas: the TID was 22.4 sec +/- 4.4 sec and 23.5 sec +/- 6.1 sec in the pancreatic head and body of the healthy volunteers, and 29.8 sec +/- 8.6 sec and 29.4 sec +/- 3.8 sec in patients with CP. The wash-in rate was 96 +/- 37 sec(-1) and 101 +/- 27 sec(-1) in controls, and 62 +/- 17 sec(-1) and 75 +/- 27 sec(-1) in CP. CONCLUSION: CP can be identified by semiquantitative changes on DCE-MRI. Whether DCE-MRI of the pancreas can be used to detect early CP remains to be validated.     

Reproducibility of 3D delayed gadolinium enhanced MRI of cartilage (dGEMRIC) of the knee at 3.0 T in patients with early stage osteoarthritis

European Radiology - To assess the reproducibility of 3D delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) at 3 T in early stage knee osteoarthritis (OA) patients. In 20 patients, 3D dGEMRIC...     

Glomerular filtration rate measured using the Patlak plot technique and contrast-enhanced dynamic MRI with different amounts of gadolinium-DTPA

We determined the optimum gadolinium (Gd)-DTPA dose and time window for calculating the glomerular filtration rate (GFR) using contrast-enhanced (CE) dynamic MRI and the Patlak plot technique. Twelve adult volunteers with healthy kidneys were included in the study. As a reference method the GFR was measured by iopromide plasma clearance. A three-dimensional gradient-echo (GRE) sequence with a flip angle of 50 degrees was used for MRI. Signal was measured using a body surface coil with four elements. Each volunteer was examined on four days using 2 mL, 4 mL, 8 mL, or 16 mL of Gd-DTPA 0.5 mmol/mL dissolved with sodium chloride (NaCl) 0.9% to a total of 60 mL. The injection rate was 1 mL/second. A Patlak plot was calculated from the kidney and aorta signals. The mean reference GFR was 133 mL/min (min-max, 116-153 mL/min). The best correlation of GFR calculated from MRI data compared to the reference method was found in a time window 30-90 seconds after aortic signal rise using 16 mL Gd-DTPA. Pearson's correlation coefficient was r = 0.83, and the standard deviation (SD) from the line of regression was 10.5 mL/minute. We found a significantly lower average GFR(MR) using 16 mL Gd-DTPA compared to 4 mL and 2 mL in the late time window 60-120 seconds post aortic rise. A dose of 16 mL Gd-DTPA was optimal for measuring GFR using dynamic MRI and the Patlak plot technique. The slope should be measured in a time window of 30-90 seconds post aortic rise.     

Gd-DTPA relaxivity depends on macromolecular content.

Gd-DTPA T(1) relaxivity of water protons was measured at 1.5 T and room temperature as a function of macromolecular content in model systems. Gd-DTPA relaxivity was found to increase with macromolecular concentration. The results of this study indicate that the Gd-DTPA relaxivity in tissue extracellular compartment could be as much as 30-70% higher than that of Gd-DTPA in saline. Quantitative MR analyses that use T(1) as an estimation of local Gd-DTPA concentration require a priori determination of the Gd relaxivity in tissue.     

磁共振延迟增强软骨成像技术对正常及退变软骨的定量研究

目的：探讨磁共振延迟增强软骨成像对正常及退变软骨的定量研究价值。方法：69例正常及OA（退行性骨关节炎,osteoarthritis）患者经静脉注射Gd-DTPA对比剂1．5—2h后在3．0T磁共振下扫描,包括正常组（n=29）和0A组（n=40）。其中OA组按照kellgren-Lawrence评分又分为轻度OA组（n=20）、中度OA组（n=11）及重度OA组（n=9）。采用3DLL技术及后处理软件得到T,mapping图像,测量中层面内侧、中问及外侧T1值及上、中及下层面平均T1值,并进行统计学分析。结果：正常组、轻度OA组、中度OA组及重度OA组平均T1驰豫值分别为（512．59±72．30）ms、（458．03±55．89）in8、（405．89±57．30）ms及（357．92±36．74）ms。采用单因素方差分析,正常及OA组髌软骨Tl值有明显的差异（F=17．70,P=0．00〈0．05）。结论：磁共振延迟增强软骨成像技术可以敏感反映出关节软骨生化成分的改变,对关节软骨退变诊断具有一定指导价值。     

High resolution fast T1 mapping technique for dGEMRIC

Purpose

To determine the feasibility of using a high resolution isotropic three‐dimensional (3D) fast T1 mapping sequence for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) to assess osteoarthritis in the hip.

Materials and Methods

T1 maps of the hip were acquired using both low and high resolution techniques following the administration of 0.2 mmol/kg Gd‐DTPA^2‐ in 35 patients. Both T1 maps were generated from two separate spoiled GRE images. The high resolution T1 map was reconstructed in the anatomically equivalent plane as the low resolution map. T1 values from the equivalent anatomic regions containing femoral and acetabular cartilages were measured on the low and high resolution maps and compared using regression analysis.

Results

In vivo T1 measurements showed a statistically significant correlation between the low and high resolution acquisitions at 1.5 Tesla (R² = 0.958, P < 0.001). These results demonstrate the feasibility of using a fast two‐angle T1 mapping (F2T1) sequence with isotropic spatial resolution (0.8 × 0.8 × 0.8 mm) for quantitative assessment of biochemical status in articular cartilage of the hip.

Conclusion

The high resolution 3D F2T1 sequence provides accurate T1 measurements in femoral and acetabular cartilages of the hip, which enables the biochemical assessment of articular cartilage in any plane through the joint. It is a powerful tool for researchers and clinicians to acquire high resolution data in a reasonable scan time (< 30 min). J. Magn. Reson. Imaging 2009;30:896–900. © 2009 Wiley‐Liss, Inc.     

Quantitative imaging of cartilage morphology at 3.0 Tesla in the presence of gadopentate dimeglumine (Gd-DTPA).

MRI-based cartilage morphometry was previously validated in the absence of gadopentate dimeglumine (Gd-DTPA). However, Gd-DTPA is required for compositional (proteoglycan) imaging using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). Therefore, the effect of Gd-DTPA on cartilage morphometry was studied. A total of 165 female participants (67 with and 98 without osteoarthritis [OA]) were imaged at 3.0 Tesla before and 2 hr after intravenous Gd-DTPA injection. Flip angles in post-Gd-DTPA scans varied between 12 degrees and 35 degrees . Cartilage volume and thickness of post- vs. pre-Gd-DTPA scans showed intraclass correlation coefficients (ICCs) of 0.85 > or = r > or = 0.95, mean differences between -2.1% and +1.1%, and standard deviations (SDs) of differences between 4.7% and 9.2%. Mixed-effect models found no consistent impact of flip angle and OA status on post- vs. pre-Gd-DTPA differences. Accurate morphological measurements of cartilage can be obtained after Gd-DTPA injection, allowing compositional and morphological imaging to be combined into one session.