T2 Mapping Of Articular Cartilage Research Articles

Fast, Accurate, and Robust T2 Mapping of Articular Cartilage by Neural Networks.

For T2 mapping, the underlying mono-exponential signal decay is traditionally quantified by non-linear Least-Squares Estimation (LSE) curve fitting, which is prone to outliers and computationally expensive. This study aimed to validate a fully connected neural network (NN) to estimate T2 relaxation times and to assess its performance versus LSE fitting methods. To this end, the NN was trained and tested in silico on a synthetic dataset of 75 million signal decays. Its quantification error was comparatively evaluated against three LSE methods, i.e., traditional methods without any modification, with an offset, and one with noise correction. Following in-situ acquisition of T2 maps in seven human cadaveric knee joint specimens at high and low signal-to-noise ratios, the NN and LSE methods were used to estimate the T2 relaxation times of the manually segmented patellofemoral cartilage. In-silico modeling at low signal-to-noise ratio indicated significantly lower quantification error for the NN (by medians of 6–33%) than for the LSE methods (p < 0.001). These results were confirmed by the in-situ measurements (medians of 10–35%). T2 quantification by the NN took only 4 s, which was faster than the LSE methods (28–43 s). In conclusion, NNs provide fast, accurate, and robust quantification of T2 relaxation times.

Is T2 mapping reliable in evaluation of native and repair cartilage tissue of the knee?

PurposeTo evaluate the effect of imaging plane and experience of observers on the reliability of T2 mapping of native and repair cartilage tissue of the knee.MethodsFifteen consecutive patients from two randomised controlled trials (RCTs) were included in this cross-sectional study. Patients with an isolated knee cartilage lesion were randomised to receive either debridement or microfracture (RCT 1) or debridement or autologous chondrocyte implantation (RCT 2). T2 mapping was performed in coronal and sagittal planes two years postoperatively. A musculoskeletal radiologist, a resident of radiology and two orthopaedic surgeons measured the T2 values independently. Intraclass Correlation Coefficient (ICC) with 95% Confidence Intervals was used to calculate the inter- and intraobserver agreement.ResultsMean age for the patients was 36.8 ± 11 years, 8 (53%) were men. The overall interobserver agreement varied from poor to good with ICCs in the range of 0.27– 0.76 for native cartilage and 0.00 – 0.90 for repair tissue. The lowest agreement was achieved for evaluations of repair cartilage tissue. The estimated ICCs suggested higher inter- and intraobserver agreement for radiologists. On medial femoral condyles, T2 values were higher for native cartilage on coronal images (p < 0.001) and for repair tissue on sagittal images (p < 0.001).ConclusionsThe reliability of T2 mapping of articular cartilage is influenced by the imaging plane and the experience of the observers. This influence may be more profound for repair cartilage tissue. This is important to consider when using T2 mapping to measure outcomes after cartilage repair surgery.Trial registrationClinicalTrials.gov, NCT02637505 and NCT02636881, registered December 2015.Level of evidenceII, based on prospective data from two RCTs.

Resolution-dependent influences of compressed sensing in quantitative T2 mapping of articular cartilage.

This study evaluates the resolution-dependent influences of compressed sensing (CS) in MRI quantification of T2 mapping in articular cartilage with osteoarthritis (OA). T2-weighed 2D experiments of healthy and OA cartilage were fully sampled in k-space with five echo times at both 17.6 μm and 195.3 μm in-plane resolutions; termed as microscopic MRI (μMRI) and macroscopic MRI (mMRI) respectively. These fully sampled k-space data were under-sampled at various 2D CS accelerating factors (AF = 4-32). The under-sampled data were reconstructed individually into 2D images using nonlinear reconstruction, which were used to calculate the T2 maps. The bulk and zonal variations of T2 values in cartilage were evaluated at different AFs. The study finds that the T2 images at AFs up to 8 preserved major visual information and produced negligible artifacts for μMRI. The T2 values remained accurate for different sub-tissue zones at various AFs. The absolute difference between the CS (AF up to 32) and the Ground Truth (i.e., using 100% of the k-space data) of the mean T2 values through the whole tissue depth was higher in mMRI versus μMRI. For mMRI (where the resolution mimics the clinical MRI of human cartilage), the quantitative T2 mapping at AFs up to 4 showed negligible variations. This study demonstrates that both clinical MRI and μMRI can benefit from the use of CS in image acquisition, and μMRI benefits more from the use of CS by acquiring much less data, without losing significant accuracy in the quantification of T2 maps in osteoarthritic cartilage.

T1 and T2 mapping of articular cartilage and menisci in early osteoarthritis of the knee using 3-Tesla magnetic resonance imaging

Purpose3-Tesla magnetic resonance imaging (MRI) T1 and T2 mapping to detect and quantify cartilage matrix and meniscal degeneration between normal healthy volunteers and early osteoarthritis patients.Material and methodsA prospective study including 25 patients and 10 healthy volunteers was done. Patients with symptoms of early osteoarthritis and Kellgren-Lawrence grade I-II on plain radiograph were included for MRI knee. Patients with inflammatory arthritis, infection, trauma, and history of knee surgery were excluded. Healthy, normal adult volunteers (preferably age and sex matched) without symptoms of osteoarthritis of the knee were drawn from patient’s relatives/hospital employees/colleagues for MRI knee.ResultsT1 and T2 relaxation time values of articular cartilage and menisci were significantly higher in osteoarthritis patients as compared to healthy volunteers. No significant difference was found in morphological thickness of articular cartilage and menisci in early osteoarthritis patients and healthy volunteers.ConclusionsT1 and T2 mapping are noninvasive MRI techniques reflecting changes in the biochemical composition of cartilage and menisci. T1 values reflect changes in proteoglycan content, and T2 values are sensitive to interaction between water molecules and collagen network. Mapping techniques assess early cartilage and meniscal matrix degeneration in osteoarthritis of the knee, and help in initiating treatment and monitoring disease progression. MRI is a sensitive modality for assessment of pathological changes in articular cartilage. With use of T1 and T2 mapping techniques, it is possible to evaluate the collagen network and proteoglycan content in articular cartilage and meniscal matrix.

Quantitative T2 Mapping of Articular Cartilage of the Glenohumeral Joint at 3.0T in Rotator Cuff Disease Patients: the Evaluation of Degenerative Change of Cartilage

Quantitative T2 Mapping of Articular Cartilage of the Glenohumeral Joint at 3.0T in Rotator Cuff Disease Patients: the Evaluation of Degenerative Change of Cartilage

T2 mapping of articular cartilage of the glenohumeral joint at 3.0T in healthy volunteers: a feasibility study.

The purpose of this study was to assess the T2 values of the glenohumeral joint cartilage in healthy asymptomatic individuals at 3.0T and to analyze the T2 profile of the humeral cartilage. This prospective study was approved by our institutional review board and written informed consent was obtained. Thirteen subjects (mean age, 28.6years; age range, 24-33 years) were included and underwent multiecho spin-echo T2-weighted MR imaging and T2 mapping was acquired. Regions of interest were placed on the humeral cartilage and glenoid cartilage on oblique coronal images. T2 profiles of humeral cartilage were measured from the bone-cartilage interface to the articular surface. Intra-observer agreement was analyzed using intraclass correlation coefficient (ICC). All 13 joints showed normal appearance on conventional T2-weighted images. The mean T2 values of humeral and glenoid cartilage were 50.5 ± 12.1 and 49.0 ± 9.9ms, respectively. Intra-observer agreement was good, as determined by ICC (0.736). Longer T2 values were observed at the articular surface with a tendency to decrease toward the bone-cartilage interface. The mean cartilage T2 value was 69.03 ± 21.2ms at the articular surface and 46.99 ± 19.6ms at the bone-cartilage interface. T2 values of the glenohumeral joint cartilage were similar to reported values of cartilage in the knee. The T2 profile of normal humeral cartilage showed a spatial variation with an increase in T2 values from the subchondral bone to the articular surface.

T2 mapping of articular cartilage in knee osteoarthritis using a magnetic resonance staging.

To evaluate T2 mapping of articular cartilage in knee osteoarthritis (OA). Totally 38 healthy subjects (group H) and 53 OA patients received scoring with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)and underwent T2 mapping of tibiofemoral articular cartilages. The T2 values in 10 subregions of the cartilages were measured. Patients in the OA group were further divided into OA1 group and OA2 group using the modified Magnetic Resonance Recht Grading System. In OA group, the fat-suppressed three-dimensional fast spoiled gradient echo MRI was performed to obtain the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). The differences of T2 values among group H, group OA1, and group OA2 were compared. The correlation between T2 value and WORMS/WOMAC scores was analyzed. The intra- and inter-observer reproducibility of measurement was calculated. The T2 values in all the subregions ranged 43.9-53.6ms in group H, 41.1-55.0 ms in group OA1, and 45.6-56.1ms in group OA2. T2 values in group OA2 were significantly higher in central medial femoral subregion, central medial, and lateral tibial subregions compared with group H, also significantly higher in central medial femoral subregion, anterior and central medial tibial subregions compared with group OA1 (P<0.05). T2 values were significantly correlated with WORMS scores (R=0.307-0.811, P<0.01) except in posterior lateral femoral subregion, but not with WOMAC scores. The correlation coefficients for intra- and inter-observer measurement showed good reproducibility (R>0.740, P<0.05) except in anterior lateral tibial subregion for inter-observer of measurement. T2 mapping can differentiate the OA severity of knee cartilage using a magnetic resonance staging, and therefore can be a sensitive technique for monitoring the severity of OA.

T2 mapping of articular cartilage in the healthy knee using a magnetic resonance segmentation.

To evaluate T2 mapping of the healthy knee articular cartilage in different subregions using a magnetic resonance segmentation. T2 mapping was performed to 77 healthy tibiofemoral cartilages, which were divided into group H1 ( <40 years old) and group H2 (≥ 40 years old). T2 values of cartilage IN 10 subregions based on the Whole-Organ Magnetic Resonance Imaging Score (WORMS) segmentation and body mass index (BMI) were calculated. T2 values of cartilage in 10 subregions were compared. The association between T2 value and BMI/age was analyzed. The intra- and inter-observer reproducibility of measurement was calculated. The T2 values of all the subregions ranged 40. 3-53.5 ms. T2 values of group H2 were significantly higher than those in group H1 (P ≤ 0.032) except in posterior lateral femoral subregion. The inter-subregion differences within group were significant (P ≤ 0.001). The inter-gender differences were significant only in posterior medial tibial subregion of group H2 (P=0.048). No correlation of T2 values with BMI was found except in cetral lateral tibial subregion of group H2 (P=0.050, R=0.308). T2 values were correlated with age in anterior medial (P=0.004, R=-0.467) and anterior lateral P = 0.024, R=-0.375) tibial subregion of group H1 , and in all tibial subregion except anterior lateral tibial subregion of group H2 , and central medial femoral subregion of group H2 (P=0.004~0.015, R=0.376~0.437). The correlation coefficients for intra- and inter-observer of measurement showed good reproducibility (R>0.809, P ≤ 0.005). T2 mapping of the healthy knee articular cartilage based on the WORMS segmentation can effectively reflect the changes and correlations of T2 values with risk factors by focusing on the functional weight-bearing subregions.

T2 Mapping of Articular Cartilage of Glenohumeral Joint with Routine MRI Correlation—Initial Experience

The evaluation of articular cartilage currently relies primarily on the identification of morphological alterations of the articular cartilage. Unlike anatomic imaging, T2 mapping is sensitive to changes in the chemical composition and structure of the cartilage. Clinical evaluation of T2 mapping of the glenohumeral joint has not been previously reported. The objectives of this study were to evaluate the feasibility of magnetic resonance T2 mapping of the glenohumeral joint in routine clinical imaging, to assess the normal T2 mapping appearance of the glenohumeral joint, and to compare the findings on T2 maps to conventional MR pulse sequences. Magnetic resonance imaging (MRI) examinations of 27 shoulders were performed in a routine clinical setting. All studies included acquisition of T2 mapping using a dedicated software. The T2 maps were analyzed along with the routine MR exam and correlation of cartilage appearance on T2 map and on conventional MR sequences. T2 imaging maps were obtained successfully in all patients. T2 maps and routine MRI correlated in cases of normal cartilage and prolonged T2 values and cartilage defects. In four cases, increased T2 relaxation times in the cartilage and cartilage defects were more apparent on T2 maps. Acquisition of T2 maps at the time of routine MRI scanning is feasible and not time-consuming.

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

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. 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. 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. T2 mapping of articular cartilage is feasible in the clinical setting and may reveal early cartilage lesions not visible with standard clinical MRI.

T2 quantitation of articular cartilage at 1.5 T.

To evaluate sources of error when using a multiecho sequence for quantitative T2 mapping of articular cartilage at 1.5 T. Phantom measurements were used to assess the contribution of stimulated echoes to inaccuracy of T2 measurements in cartilage using a multiecho sequence. Five volunteer studies compared in vivo single-echo spin echo results to multiecho, single-slice and multiecho, multislice acquisitions for assessment of both the stimulated echo and magnetization transfer contrast (MTC) contributions to T2 measurement inaccuracy. Phantom experiments demonstrated that substantial inaccuracy (10%-13% longer T2 values) is introduced from stimulated echoes with a multiecho sequence with slice-selective refocusing pulses. The in vivo volunteer studies also demonstrated increases in measured T2 by up to 48% with a multiecho sequence. Use of the multiecho sequence in the multislice mode resulted in T2 values closer to the single-echo standards for the volunteer studies. However, this apparent increased accuracy should be regarded as circumstantial, as it only occurs because the error due to MTC has the opposite sign compared to the error due to the stimulated echo contribution. Use of a multiecho, multislice sequence for cartilage T2 measurements should be undertaken with the caution that substantial inaccuracy is introduced from stimulated echoes and MTC.