Liver,bone marrow,pancreas and pituitary gland iron overload in young and adult thalassemic patients: a T2 relaxometry study

Thirty-seven patients with β-thalassemia major, including 14 adolescents (15.2 ± 3.0 years) and 23 adults (26.4 ± 6.9 years), were studied. T2 relaxation time (T2) of the liver, bone marrow, pancreas and pituitary gland was measured in a 1.5-Tesla magnetic resonance (MR) imager, using a multiecho spin-echo sequence (TR/TE 2,000/20, 40, 60, 80, 100, 120, 140, 160 ms). Pituitary gland height was evaluated in a midline sagittal scan of a spin-echo sequence (TR/TE, 500/20 ms). The T2 of the pituitary gland was higher in adolescents (59.4 ± 15 ms) than in adults (45.3 ± 10.4 ms), P < 0.05. The T2 of the pancreas was lower in adolescents (43.6 ± 10.3 ms) than in adults (54.4 ± 10.4 ms). No difference among groups was found in the T2 of the liver and bone marrow. There was no significant correlation of the T2 among the liver, pancreas, pituitary gland and bone marrow. There was no significant correlation between serum ferritin and T2 of the liver, pancreas and bone marrow. Pituitary T2 showed a significant correlation with pituitary gland height (adolescents: R = 0.63, adults: R = 0.62, P < 0.05) and serum ferritin (adolescents: R = −0.60, adults: R = −0.50, P < 0.05). In conclusion, iron overload evaluated by T2 is organ specific. After adolescence, age-related T2 changes are predominantly associated with pituitary siderosis and fatty degeneration of the pancreas. Pituitary size decreases with progressing siderosis.     

Initial results of in vivo high-resolution morphological and biochemical cartilage imaging of patients after matrix-associated autologous chondrocyte transplantation (MACT) of the ankle

Objective  The aim of this study was to use morphological as well as biochemical (T2 and T2* relaxation times and diffusion-weighted imaging (DWI)) magnetic resonance imaging (MRI) for the evaluation of healthy cartilage and cartilage repair tissue after matrix-associated autologous chondrocyte transplantation (MACT) of the ankle joint. Materials and methods  Ten healthy volunteers (mean age, 32.4 years) and 12 patients who underwent MACT of the ankle joint (mean age, 32.8 years) were included. In order to evaluate possible maturation effects, patients were separated into short-term (6–13 months) and long-term (20–54 months) follow-up cohorts. MRI was performed on a 3.0-T magnetic resonance (MR) scanner using a new dedicated eight-channel foot-and-ankle coil. Using high-resolution morphological MRI, the magnetic resonance observation of cartilage repair tissue (MOCART) score was assessed. For biochemical MRI, T2 mapping, T2* mapping, and DWI were obtained. Region-of-interest analysis was performed within native cartilage of the volunteers and control cartilage as well as cartilage repair tissue in the patients subsequent to MACT. Results  The overall MOCART score in patients after MACT was 73.8. T2 relaxation times (~50 ms), T2* relaxation times (~16 ms), and the diffusion constant for DWI (~1.3) were comparable for the healthy volunteers and the control cartilage in the patients after MACT. The cartilage repair tissue showed no significant difference in T2 and T2* relaxation times (p ≥ 0.05) compared to the control cartilage; however, a significantly higher diffusivity (~1.5; p < 0.05) was noted in the cartilage repair tissue. Conclusion  The obtained results suggest that besides morphological MRI and biochemical MR techniques, such as T2 and T2* mapping, DWI may also deliver additional information about the ultrastructure of cartilage and cartilage repair tissue in the ankle joint using high-field MRI, a dedicated multichannel coil, and sophisticated sequences.     

An in vitro comparative study of T2 and T2* mappings of human articular cartilage at 3-Tesla MRI using histology as the standard of reference

Objective

The aim of this study was to evaluate the correlations between T2 value, T2* value, and histological grades of degenerated human articular cartilage.

Materials and methods

T2 mapping and T2* mapping of nine tibial osteochondral specimens were obtained using a 3-T MRI after total knee arthroplasty. A total of 94 ROIs were analyzed. Histological grades were assessed using the David–Vaudey scale. Spearman’s rho correlation analysis and Pearson’s correlation analysis were performed.

Results

The mean relaxation values in T2 map with different histological grades (0, 1, 2) of the cartilage were 51.9?±?9.2 ms, 55.8?±?12.8 ms, and 59.6?±?10.2 ms, respectively. The mean relaxation values in T2* map with different histological grades (0, 1, 2) of the cartilage were 20.3?±?10.3 ms, 21.1?±?12.4 ms, and 15.4?±?8.5 ms, respectively. Spearman’s rho correlation analysis confirmed a positive correlation between T2 value and histological grade (ρ?=?0.313, p?<?0.05). Pearson’s correlation analysis revealed a significant negative correlation between T2 and T2* (r?=??0.322, p?<?0.05). Although T2* values showed a decreasing trend with an increase in cartilage degeneration, this correlation was not statistically significant in this study (ρ?=??0.192, p?=?0.129).

Conclusions

T2 mapping was correlated with histological degeneration, and it may be a good biomarker for osteoarthritis in human articular cartilage. However, the strength of the correlation was weak (ρ?=?0.313). Although T2* values showed a decreasing trend with an increase in cartilage degeneration, the correlation was not statistically significant. Therefore, T2 mapping may be more appropriate for the initial diagnosis of articular cartilage degeneration in the knee joint. Further studies on T2* mapping are needed to confirm its reliability and mechanism in cartilage degeneration.     

Gd-BOPTA for assessment of myocardial viability on MRI: changes of T1 value and their impact on delayed enhancement

Gadobenate (Gd-BOPTA), injected at a dose of 0.1 mmol/kg body weight, was compared with gadopentetate (Gd-DTPA), injected at a dose of 0.2 mmol/kg body weight, for delineation of myocardial infarction interindividually in two groups of 26 patients each. Delayed enhancement images were assessed subjectively for image quality, and measured for regional T1 values before, 3 min after and 25 min after the injection of each contrast agent. In the 26 patients who received Gd-BOPTA, T1 values of remote myocardium were 1,070 ± 125 ms, 358 ± 78 ms and 562 ± 108 ms before, 3 min after and 25 min after injection, respectively. Infarcted myocardium values were 1,097 ± 148 ms, 246 ± 68 ms and 373 ± 84 ms and left ventricular blood pool 1,238 ± 95 ms, 194 ± 47 ms and 373 ± 72 ms. In the 26 patients who received Gd-DTPA, T1 values were 1,087 ± 96 ms, 325 ± 60 ms and 555 ± 108 ms for remote myocardium; 1,134 ± 109, 210 ± 43 ms and 304 ± 57 ms for infarcted myocardium; and 1,258 ± 104 ms, 166 ± 27 ms and 351 ± 73 ms for left ventricular blood pool. Delayed enhancement image quality showing myocardial infarction was rated good (54%) and excellent (46%) after Gd-BOPTA, and good (58%) and excellent (42%) after Gd-DTPA (no significant differences). A single dose of Gd-BOPTA compared with a double dose of Gd-DTPA causes similar changes of T1 values in infarcted and remote myocardium and provides fairly similar contrast between infarcted and remote myocardium (0.64 ± 14 versus 0.71 ± 11) and slightly higher contrast between left ventricular blood and infarcted myocardium (0.22 ± 17 versus 0.14 ± 6; p < 0.05). Administration of 0.1 mmol/kg body weight Gd-BOPTA can provide similar late enhancement images compared with the standard 0.2 mmol/kg body weight dose of Gd-DTPA due to the higher T1 relaxivity associated with the former. Peter Lodemann is an employee of Bracco Deutschland GmbH.     

Can T2 relaxation values and color maps be used to detect chondral damage utilizing subchondral bone marrow edema as a marker?

Objective  This study aimed to investigate whether a commercially available time-efficient T2 mapping sequence will demonstrate findings of articular cartilage degeneration based on T2 relaxation values (RV) and color maps, using subchondral bone marrow edema (BME) as a marker for chondral damage. Materials and methods  The patient group consisted of 88 subjects who underwent knee magnetic resonance imaging at 1.5 T who had subchondral BME evident on fat-suppressed T2-weighted sequences. The control group was comprised of 60 subjects with no evidence of subchondral BME. A commercially available eight echo T2 relaxation sequence (acquisition time 8:36 min) was used to construct a T2 color map and to determine T2 RVs. T2 RVs were determined on cartilage overlying subchondral BME in patients and in eight pre-determined anatomical regions in controls. T2 color maps in the patient and control groups were analyzed for degree of color stratification (presence = two or more colors) at the same anatomic site as that used for T2 RV determination. Results  T2 RVs were significantly increased in patients compared to controls for the medial femoral condyle (MF; p < 0.01), medial patellar facet (MP; p < 0.01), lateral patellar facet (LP; p < 0.01), lateral femoral condyle (LF; p < 0.01) and lateral tibial plateau (LT; p < 0.01). Loss of color stratification was noted in patients compared to controls in the medial tibial plateau (MT; p = 0.01), LF (p < 0.01), and LT (p < 0.01). In the patient group, increase in T2 RVs was associated with corresponding decrease in color stratification in MF (p < 0.01), MT (p < 0.01), MP (p < 0.01), medial femoral trochlear groove (p = 0.02), and lateral femoral trochlear groove (p < 0.01). Conclusion  Subchondral BME was associated with an increase in adjacent articular cartilage T2 RVs at some sites. Also, elevated T2 RVs were associated with loss of color stratification.     

MR imaging of hyaline cartilage at 0.5 T: a quantitative and qualitative in vitro evaluation of three types of sequences

Objective. To identify an optimal pulse sequence for in vitro imaging of hyaline cartilage at 0.5 T. Materials and methods. Twelve holes of varying diameter and depth were drilled in cartilage of two pig knees. These were submerged in saline and scanned with a 0.5-T MR system. Sixteen T1-weighted gradient echo (GE), two T2-weighted GE, and 16 fast spin echo sequences were used, by varying repetition time (TR), echo time (TE), flip angle (FA), echo train length, profile order, and by use of fat saturation. Contrast-to-noise ratios (CNR) of cartilage versus saline solution and cartilage versus subchondral bone were measured. Cartilaginous lesions were evaluated separately by three independent observers. Interobserver variability and correlation between the quantitative and qualitative analyses were calculated. Results. The mean CNRs of two specimens of cartilage versus saline solution ranged from 6.3 (±2.1) to 27.7 (±2.5), and those of cartilage versus subchondral bone from 0.3 (±0.2) to 22.5 (±1.4). The highest CNR was obtained with a T1-weighted spoiled 3D-GE technique (TR 65 ms, TE 11.5 ms, FA 45°). The number of lesions observed per sequence varied from 35 to 69. Observer agreement was fair to good. The T1-weighted spoiled GE sequences with a TR of 65 ms, TE of 11.5 ms and FA of 30° and 45° were significantly superior to the other 34 sequences in the qualitative analysis. Conclusion. T1-weighted spoiled 3D-GE sequences with a TR of 65 ms, a TE of 11.5 ms, and a FA of 30–45° were found to be optimal for in vitro imaging of cartilage at 0.5 T.     

MRI evaluation of the patellar articular cartilage in patients with subluxation of the patella

In patients with subluxation of the patella, injury of the patellar articular cartilage is frequently observed and correct evaluation is important to manage these patients. We examined 11 patients with subluxation of the patella and five normal volunteers. In 12 patellofemoral joints of seven patients with subluxation of the patella, the abnormalities observed on MRI were compared with those on arthroscopy and/or at operation. MRI was performed with a Magnetom 1.5 T (Siemens) using the round surface coil. Pulse sequences were SE (TR 400 ms/TE 19 ms), FLASH (TR 320 ms/TE 15 ms FA 90 degrees and 40 degrees), and SE (TR 2000 ms/TE 26, 70 ms). We analysed MR findings of the 12 abnormal joints and 10 normal joints according to the following classification of abnormalities observed on arthroscopy. (1) normal appearance (n = 3 joints), (2) softening and fibrillation (n = 6), (3) fragmentation (n = 3), and (4) erosion to bone (n = 0). In only one of the six cases with softening and fibrillation observed on arthroscopy, MRI could visualize the thickening of patellar articular cartilage, but in all three cases with fragmentation observed on arthroscopy, MRI could visualize the thin inhomogenous cartilage with irregular surface. The combination of SE (TR 400 ms/TE 19 ms) and FLASH (TR 320 ms/TE 15 ms FA 90 degrees) are extremely effective pulse sequence to detect the abnormalities of patellar articular cartilage. We conclude that MRI is a useful noninvasive method of detecting advanced changes in patellar articular cartilage.     

正常人胫股关节软骨T2及T2*弛豫值的比较研究

目的:探讨正常志愿者膝关节软骨的T2及T2*弛豫值范围、影响因素及其内在相关程度。方法:将63名健康人胫股关节按照年龄分为青少年组(<35岁)18人、中年组(36~55岁)28人和老年组(56~78岁)17人,计算体重指数(BMI)并行T2图、T2*图成像,按照全器官磁共振成像评分(WORMS)规定的软骨分区法测量胫股关节软骨10个感兴趣区的T2、T2*弛豫率并取平均值,然后进行统计学分析。结果:健康人胫股关节软骨T2、T2*值分别为(42.98±4.19)ms、(19.75±2.43)ms。左右膝胫股关节T2、T2*值分别为(43.60±4.08 ms,42.37±4.26 ms)、(19.29±2.48 ms,20.21±2.37 ms),经检验两者均无明显统计学差异(P>0.05)。女性及男性胫股关节软骨T2、T2*值分别为(44.28±5.14 ms,41.86±4.09 ms)、(19.36±2.48 ms、20.09±2.42 ms),亦无明显统计学差异(P>0.05)。青少年组、中年组及老年组胫股关节软骨的T2、T2*值分别为(37.45±1.76 ms,41.29±2.13 ms,44.98±4.73 ms)、(17.95±1.58 ms,20.76±1.52 ms,22.30±2.08 ms),三组间有明显统计学差异(P<0.01)。青少年组、中年组及老年组三组内T2、T2*值均呈显著相关(P<0.05,Pearson相关系数分别为0.61、0.63、0.55)。结论:正常人胫股关节软骨T2及T2*弛豫值研究可以为关节软骨早期病变的诊断提供相似的参考价值,定量测定T2*值有望替代传统的T2值用于研究软骨形态学改变之前软骨内生化成分的变化。     

Utility of delayed gadolinium-enhanced MRI (dGEMRIC) for qualitative evaluation of articular cartilage of patellofemoral joint

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) was used for the measurement of relative proteoglycan depletion of articular cartilage in the patellofemoral (PF) joint following a proprietary protocol, which was compared with the X-ray images, proton density weighted MR images (PDWI) and arthroscopic findings. The study examined 30 knees. The ages ranged from 16 to 74 (average 40.3) years. The Gd-DTPA^2–containing contrast medium was used in a single dose. The subjects were made to exercise the knee joint for 10 min; and MR images were taken 2 h after intravenous injection of contrast medium. T1-calculated images were produced and the region of interest (ROI) was set as follows. (1) ROI1: entire articular cartilage in a slice through the center of the patella. (2) ROI2: low signal region in T1-calculated images, which were set in a blind fashion by two observers. (3) ROI3: articular cartilage on one side that includes ROI2 where low signal region were detected (medial or lateral). ROI3 was set to examine the contrast of ROI2 with surrounding articular cartilage. The average T1 values of ROI1 was 393.5±33.6 ms for radiographic grade 0 and 361.3±11.1 ms for grade I, which showed a significant difference (P=0.036). The T1 value of ROI2 was 351.6±28.2 ms for grade I, 361.9±38.3 ms for grade II, 362.1±67.7 ms for grade III, and 297.8±54.1 ms for grade IV according to arthroscopic Outerbridge classification. All cases, that demonstrated decrease of T1 values on dGEMRIC (ROI2), showed abnormal arthroscopic or direct viewing findings. The ratio (ROI3/ROI2) in cases of only slight damage classified as Outerbridge grade I (6 cases) was an average of 1.04±0.02 and was 1.0 or greater in all cases, thereby indicating well-defined contrast with the surrounding cartilage. The diagnosis of damage in articular cartilage was possible in all 16 cases with radiographic K–L grade I on dGEMRIC, while the intensity changes were not found in 10 of 16 cases on PDWI. The dGEMRIC with a single-dose would be useful on a diagnosis of the area demonstrating early relative proteoglycan depletion in the articular cartilage of the PF joint prior to any discernible changes in the subchondral bone on X-ray images and exceeds to plain MR images for examining deterioration of articular cartilage.     

Intraindividual comparison of myocardial delayed enhancement MR imaging using gadobenate dimeglumine at 1.5 T and 3 T

For contrast-enhanced imaging techniques relying on strong T1 weighting, 3 T provides increased contrast compared with 1.5 T. The aim of our study was the intraindividual comparison of delayed enhancement MR imaging at 1.5 T and at 3 T. Twenty patients with myocardial infarction were examined at 1.5 T and 3 T. Fifteen minutes after injection of contrast agent (0.1 mmol gadobenate dimeglumine per kg body weight), inversion recovery gradient recalled echo (IR-GRE) sequences were acquired (1.5 T/3 T: TR 11.0/9.9 ms, TE 4.4/4.9 ms, flip 30°/30°, slice thickness 6/6 mm) to assess myocardial viability. Two observers rated image quality (Wilcoxon signed rank test). Quantification of hyperenhanced myocardium and standardized SNR/CNR measurements were performed (Student’s t test). There was no significant difference with respect to image quality (1.5 T/3 T: 3.5/3.3, p = 0.34, reader 1; 2.4/2.7, p = 0.12, reader 2) and infarction size (760 ± 566/828 ± 677 mm² at 1.5 T, 808 ± 639/826 ± 726 mm² at 3 T, reader 1/reader 2, p > 0.05). Mean SNR in hyperenhanced/normal myocardium was 19.2/6.2 at 1.5 T and 29.5/8.8 at 3 T (p < 0.05). Mean CNR was 14.3 at 1.5 T and 26.0 at 3 T (p < 0.05). Delayed enhancement MR imaging at 3 T is a robust procedure yielding superior tissue contrast at 3 T compared with 1.5 T which is, however, not reflected by increased image quality.     

Mapping T2 relaxation time in the pediatric knee: feasibility with a clinical 1.5-T MR imaging system

PURPOSE: To determine the feasibility of mapping the spatial variation of cartilage T2 relaxation time in vivo in the pediatric knee with a 1.5-T clinical magnetic resonance (MR) imaging system and the manufacturer's body gradient coil. MATERIALS AND METHODS: Twenty-five children and adolescents (age range, 5-17 years; mean age, 11.8 years) underwent a multisection-multiecho MR sequence for T2 relaxation time mapping. Quantitative transverse T2 maps of the patellar cartilage were calculated for 15 of the subjects. Sagittal T2 maps were calculated for the remaining 10 subjects. T2 profiles were generated for the patellar and distal femoral weight- and non-weight-bearing unossified epiphyseal and articular hyaline cartilage and for the distal femoral and proximal tibial physes. The Mann-Whitney U test was used to test for differences between paired profiles. RESULTS: Femoral non-weight-bearing unossified epiphyseal and articular cartilage showed spatial variation similar to that of weight-bearing unossified epiphyseal and articular cartilage, but with increased T2 values (P <.001). T2 spatial variations of the distal femoral and proximal tibial physes were similar to those of epiphyseal and articular cartilage but had a different pattern and increased magnitude (P <.001). The highest T2 values were measured in the distal femoral physis. CONCLUSION: T2 spatial variation of patellar hyaline cartilage in children is similar to that of patellar articular cartilage in adults. Mapping of spatial variation of T2 relaxation time of cartilage in the pediatric knee in vivo is feasible with a clinical 1.5-T MR imaging system and a body gradient coil.     

Evaluation and comparison of cartilage repair tissue of the patella and medial femoral condyle by using morphological MRI and biochemical zonal T2 mapping

The objective of this study was to use advanced MR techniques to evaluate and compare cartilage repair tissue after matrix-associated autologous chondrocyte transplantation (MACT) in the patella and medial femoral condyle (MFC). Thirty-four patients treated with MACT underwent 3-T MRI of the knee. Patients were treated on either patella (n = 17) or MFC (n = 17) cartilage and were matched by age and postoperative interval. For morphological evaluation, the MR observation of cartilage repair tissue (MOCART) score was used, with a 3D-True-FISP sequence. For biochemical assessment, T2 mapping was prepared by using a multiecho spin-echo approach with particular attention to the cartilage zonal structure. Statistical evaluation was done by analyses of variance. The MOCART score showed no significant differences between the patella and MFC (p ≥ 0.05). With regard to biochemical T2 relaxation, higher T2 values were found throughout the MFC (p < 0.05). The zonal increase in T2 values from deep to superficial was significant for control cartilage (p < 0.001) and cartilage repair tissue (p < 0.05), with an earlier onset in the repair tissue of the patella. The assessment of cartilage repair tissue of the patella and MFC afforded comparable morphological results, whereas biochemical T2 values showed differences, possibly due to dissimilar biomechanical loading conditions.     

Patellar cartilage lesions: comparison of magnetic resonance imaging and T2 relaxation-time mapping

PURPOSE: To evaluate the detection and the size of focal patellar cartilage lesions in T2 mapping as compared to standard clinical magnetic resonance imaging (MRI) at 1.5T. MATERIAL AND METHODS: Fifty-five consecutive clinical patients referred to knee MRI were imaged both with a standard knee MRI protocol (proton-density-weighted sagittal and axial series, T2-weighted sagittal and coronal series, and T1-weighted coronal series) and with an axial multislice multi-echo spin-echo measurement to determine the T2 relaxation time of the patellar cartilage. MR images and T2 maps of patellar cartilage were evaluated for focal lesions. The lesions were evaluated for lesion width (mm), lesion depth (1/3, 2/3, or 3/3 of cartilage thickness), and T2 value (20-40 ms, 40-60 ms, or 60-80 ms) based on visual evaluation. RESULTS: Altogether, 36 focal patellar cartilage lesions were detected from 20 human subjects (11 male, nine female, mean age 40+/-15 years). Twenty-eight lesions were detected both on MRI and T2 maps, while eight lesions were only visible on T2 maps. Cartilage lesions were significantly wider (P = 0.001) and thicker (P<0.001) on T2 maps as compared to standard knee MRI. Most lesions 27 had moderately (T2 40-60 ms) increased T2 values, while two lesions had slightly (T2 20-40 ms) and seven lesions remarkably (T2 60-80 ms) increased T2 relaxation times. CONCLUSION: T2 mapping of articular cartilage is feasible in the clinical setting and may reveal early cartilage lesions not visible with standard clinical MRI.     

Cardiac T2* and lipid measurement at 3.0 T-initial experience

This study was designed to assess whether breath-hold cardiac multiecho imaging at 3.0 T is achievable without significant image artefacts and if fat/water phase interference modulates the exponential T2* signal decay. Twelve healthy volunteers (mean age 39) were imaged on a Philips Intera 3.0 T MRI scanner. Multiecho imaging was performed with a breath-hold spoiled gradient echo sequence with a seven echo readout (echo times 1.15–8.05 ms, repetition time 11 ms) using a black-blood prepulse and volume shimming. T2* values were calculated with both mono- and biexpoential fits from the mean signal intensity of the interventricular septum. The global mean T2* was 27.3 ms ± 6.4. The mean signal-to-noise ratio (SNR) of the septum was 22.8 ± 9.9, and the contrast-to-noise ratio (CNR) of the septum to the left ventricular cavity 20.3 ± 9.4. A better fit was obtained with a biexponential model and the mean fat fraction derived was 3.7%. Cardiac functional parameters were in the normal range and showed no correlation with T2*. Cardiac T2* estimation with gradient multiecho imaging at 3.0 T can be achieved with minimal artefact and modelling the signal decay with a biexponential function allows estimation of myocardial lipid content as well as T2* decay.     

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.     

T2* measurement of the knee articular cartilage in osteoarthritis at 3T

Purpose:

To measure reproducibility, longitudinal and cross‐sectional differences in T2* maps at 3 Tesla (T) in the articular cartilage of the knee in subjects with osteoarthritis (OA) and healthy matched controls.

Materials and Methods:

MRI data and standing radiographs were acquired from 33 subjects with OA and 21 healthy controls matched for age and gender. Reproducibility was determined by two sessions in the same day, while longitudinal and cross‐sectional group differences used visits at baseline, 3 and 6 months. Each visit contained symptomological assessments and an MRI session consisting of high resolution three‐dimensional double‐echo‐steady‐state (DESS) and co‐registered T2* maps of the most diseased knee. A blinded reader delineated the articular cartilage on the DESS images and median T2* values were reported.

Results:

T2* values showed an intra‐visit reproducibility of 2.0% over the whole cartilage. No longitudinal effects were measured in either group over 6 months. T2* maps revealed a 5.8% longer T2* in the medial tibial cartilage and 7.6% and 6.5% shorter T2* in the patellar and lateral tibial cartilage, respectively, in OA subjects versus controls (P < 0.02).

Conclusion:

T2* mapping is a repeatable process that showed differences between the OA subject and control groups. J. Magn. Reson. Imaging 2012;35:1422–1429. © 2012 Wiley Periodicals Inc.     

T2 quantitation of human articular cartilage in a clinical setting at 1.5 T: implementation and testing of four multiecho pulse sequence designs for validity

RATIONALE AND OBJECTIVES: Evaluation of the T2 relaxation time of articular cartilage holds great potential for quantitative assessment of internal changes of the cartilage matrix. The purpose of the present study was to assess the validity of multiecho-based cartilage T2 quantitation in a clinical MRI setting at 1.5 T. METHODS: Four multisection multiecho sequence variants dedicated for quantitative T2 mapping of human articular cartilage were implemented on a 1.5 T whole-body imager and tested for accuracy in CuSO4-agarose gel phantoms and human patellar cartilage. Sequence design was varied to minimize errors in T2 quantitation due to stimulated echoes. RESULTS: As compared with single spin-echo experiments, the apparent T2 values calculated from the multiecho sequence variants showed mean deviations ranging from +26% to -32% (phantoms) and from +42% to -18% (cartilage). The patellar cartilage T2 covered a range from about 25 milliseconds to 55 milliseconds, with longer T2 values observed in the more superficial layers. In cartilage, best results were obtained from the sequence design using improved section profiles and a spoiler gradient scheme for suppression of stimulated echoes. CONCLUSIONS: Our results revealed a clear dependence of apparent T2 relaxation times on the pulse sequence design, emphasizing that the "true" T2 is hard to find. In addition, the effect on the apparent T2 values resulting from the specific modification of any sequence variant varied according to the respective tissue's properties. Therefore, the acquisition technique in conjunction with the specific tissue on which T2 mapping is performed need to be reported in detail and should kept consistent to allow large-scale comparisons and monitoring of treatment strategies, e.g., in osteoarthritis.     

1.5T MR研究健康人膝关节软骨T_2值空间分布

目的 研究健康成人膝关节软骨T2弛豫时间(T2值)空间分布.方法 1.5T场强下对21名健康男性(年龄24～39岁,平均30岁±4岁)行膝关节矢状位多回波多层面SE序列扫描,使用Profile软件测量股骨非承重软骨的前部、股骨承重软骨、胫骨承重软骨、髌软骨的T2弛豫时间(即T2值),采用方差分析检验各部位软骨深层和浅层T2值、承重软骨和非承重软骨的T2值空间分布的差异.结果 健康人膝关节软骨T2值空间分布呈浅凹形曲线,即近软骨下骨质T2值较高,随后T2值从软骨深层到浅层逐渐增高,并且各层T2值存在差异(F=70.892,P＜0.05).髌软骨T2值空间分布变化最大,股胫关节承重软骨和股骨前部非承重软骨T2值的空间分布变化较平缓.髌软骨深层T2值[(26.56±4.4) ms]明显低于所有软骨深层T2值(P=0.001).股骨外髁承重软骨浅层T2值[(35.2±6.31) ms]明显低于髌软骨[(40.78±3.56) ms]和股骨非承重软骨前部[(42.31±2.4) ms](P=0.002,P=0.000).胫骨外髁承重部软骨浅层T2值[37.11±6.6) ms]明显低于股骨非承重前部(P=0.000).结论 1.5T 场强下健康人膝关节软骨T2值具有特定空间分布,对量化研究退行性骨关节炎和其他关节病变具有参考价值.     

Selective water excitation for faster MR imaging of articular cartilage defects: initial clinical results

Our objective was to compare a water-excitation (WE) 3D fast low-angle shot (FLASH) MR sequence for faster imaging of articular cartilage defects of the knee to a conventional fat-saturated (FS) 3D FLASH MR sequence. This prospective study included 16 knees of 16 patients with suspected cartilage lesions. The MR imaging in transverse and sagittal planes included (a) FS 3D FLASH (TR/TE: 45 ms/11 ms, scan time 8 min, flip angle 50°), and (b) WE 3D FLASH (TR/TE: 28 ms/11 ms, scan time 4 min 58 s, flip angle 40°). For each sequence signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were quantified. The detected cartilage lesions were evaluated using a semi-quantitative four-scale scoring system (grades 0–III). The data were compared between the sequences using the paired Student's t-test. No statistically significant differences between the sequences were found for SNR, CNR, and cartilage defect grading (p=0.14–0.8). The WE 3D FLASH MR imaging seems to be promising for fast imaging of articular cartilage lesions of the knee. Electronic Publication     

Spatial variation in cartilage T2 of the knee.

Technical limitations imposed by resolution and B1 homogeneity have thus far limited quantitative in vivo T2 mapping of cartilage to the patella. The purpose of this study is to develop T2 mapping of the femoral/tibial joint and assess regional variability of cartilage T2 in the knee. Quantitative in vivo T2 mapping of the knee was performed on 15 asymptomatic adults (age, 22-44) using a 3T MR scanner. There is a consistent pattern of spatial variation in cartilage T2 with longer values near the articular surface. The greatest variation occurs in the patella, where T2 increases from 45.3 +/- 2.5 msec at a normalized distance of 0.33-67 +/- 5.5 msec at a distance of 1.0. These results demonstrate feasibility of performing in vivo T2 mapping of femoral tibial cartilage. Except for the superficial 15% where T2 values are lower, the spatial variation in T2 of femoral and tibial cartilage is similar to patellar cartilage.