T2 and T2* Mapping

Background. New quantitative magnetic resonance imaging (MRI) techniques are increasingly applied as outcome measures after cartilage repair. Objective. To review the current literature on the use of quantitative MRI biomarkers for evaluation of cartilage repair at the knee and ankle. Methods. Using PubMed literature research, studies on biochemical, quantitative MR imaging of cartilage repair were identified and reviewed. Results. Quantitative MR biomarkers detect early degeneration of articular cartilage, mainly represented by an increasing water content, collagen disruption, and proteoglycan loss. Recently, feasibility of biochemical MR imaging of cartilage repair tissue and surrounding cartilage was demonstrated. Ultrastructural properties of the tissue after different repair procedures resulted in differences in imaging characteristics. T2 mapping, T1rho mapping, delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), and diffusion weighted imaging (DWI) are applicable on most clinical 1.5 T and 3 T MR scanners. Currently, a standard of reference is difficult to define and knowledge is limited concerning correlation of clinical and MR findings. The lack of histological correlations complicates the identification of the exact tissue composition. Conclusions. A multimodal approach combining several quantitative MRI techniques in addition to morphological and clinical evaluation might be promising. Further investigations are required to demonstrate the potential for outcome evaluation after cartilage repair.

Cartilage injuries are common, especially in athletes. Because these injuries frequently affect young patients, and they have the potential to progress to osteoarthritis, treatment to alleviate symptoms and delay joint degeneration is warranted. A number of surgical techniques are available to treat focal chondral defects, including marrow stimulation, osteochondral auto- and allografting, and autologous chondrocyte implantation. Although arthroscopy is considered the standard of reference for the evaluation of cartilage before and after repair, it is invasive with associated morbidity and cannot adequately depict the deep cartilage layer and underlying bone. Magnetic resonance (MR) imaging provides unparalleled noninvasive assessment of the repair site and all other joint tissues. MR observation of cartilage repair tissue is a well-established semiquantitative scoring system for repair tissue that has primarily been used in clinical research studies. The cartilage repair osteoarthritis knee score (CROAKS) optimizes comprehensive morphologic assessment of the knee joint after cartilage repair. Furthermore, quantitative, compositional MR imaging measurements (eg, T2, T2*, T1ρ), delayed gadolinium-enhanced MR imaging of cartilage (dGEMRIC), and sodium imaging are available for biochemical assessment. These quantitative MR imaging techniques help assess collagen content and orientation, water content, and glycosaminoglycan and/or proteoglycan content both in the repair tissue as it matures and in the "native" cartilage. In this review, the authors discuss the principles of state-of-the-art morphologic and compositional MR imaging techniques for imaging of cartilage repair and their application to longitudinal studies.

Engineering Stem and Stromal Cell Therapies for Musculoskeletal Tissue Repair.

Follow-up of a New Arthroscopic Technique for Implantation of Matrix-Encapsulated Autologous Chondrocytes in the Knee

The composition of extracellular matrix was studied at 11 different sites in the knee (stifle) articular cartilage of young beagle dogs after running exercise of 15 weeks, 20 km/day. Water content was significantly elevated by 5-17% in the patellofemoral groove and in anterior and intermediate sites on the lateral condyle of femur. Collagen content was decreased by 14 to 20% in the same sites of the lateral condyle. Proteoglycan (PG) content was not significantly changed except in the posterior edge of the medial condyle of femur with a 30% decrease. The proportion of PGs capable of reaggregation with hyaluronan was increased in tibial and femoral surfaces (mean of all sites +18%). Also, the aggregating PG monomers were larger at all sites, as studied by agarose gel electrophoresis. The chondroitin-6 to 4-sulphate ratio was reduced at the summits of femoral condyles and patella by 10 to 25%, but increased in the patellar surface of femur and tibial medial condyle, fitting to a previous finding that strenuous running depleted proteoglycans at the summits of femoral condyle from the superficial zone that is rich in chondroitin-6-sulphate. The increased water content, accompanied with a decreased concentration of collagen in the lateral femoral condyle, suggests loosening of the collagenous framework, an idea compatible with an earlier notion of superficial depletion of PGs in these sites, and possibly predisposing to degeneration. The size increase of the aggregating PGs probably indicate that a larger proportion of matrix PGs were newly synthesized and hence the turnover rate of the PGs was enhanced. It is concluded that the strenuous running program induced locally restricted changes resembling early degeneration of articular cartilage, while simultaneously caused alterations that suggest a general stimulation of proteoglycan metabolism.

Minimal hepatic encephalopathy (MHE) is a frequent neurocognitive complication in chronic hepatic schistosomiasis (CHS) patients. Conventional diagnostic tools are time-consuming and influenced by education level. Quantitative MRI mapping offers a potential non-invasive biomarker for MHE, but its role in CHS remains unclear. This study aimed to evaluate the diagnostic value of quantitative T1 and T2 mapping for detecting MHE in CHS patients. This prospective cross-sectional observational study was conducted from August 2023 to July 2024. A total of 88 CHS patients were enrolled and divided into MHE (n = 50) and non-MHE group (n = 38). MHE was assessed using the number connection test-A (NCT-A) and digit symbol test (DST). All participants underwent 3.0T MRI with T1 and T2 mapping. Group comparisons, correlation analyses, logistic regression, and receiver operating characteristic (ROC) curve analyses were performed. MHE patients exhibited significantly lower T1 values across multiple brain regions, particularly the globus pallidus (all p < 0.001). T2 values showed no significant differences between groups. Multivariable regression confirmed that lower T1 values were independently associated with MHE (p = 0.009). ROC analysis demonstrated excellent diagnostic performance of globus pallidus T1 values (AUC = 0.92, 95% CI: 0.86-0.99), with sensitivity of 0.97 and specificity of 0.90. T1 values were also correlated with neuropsychological tests (NCT-A: r = -0.345, p < 0.001; DST: r = 0.232, p = 0.029). However, T2 values showed no significant group differences or diagnostic value. Quantitative T1 mapping, rather than T2 mapping, could be used as a potential non-invasive biomarker for detecting MHE in CHS patients. This approach offers an objective complement to psychometric testing and may facilitate earlier diagnosis and monitoring of MHE progression.

Anterior cruciate ligament (ACL) injuries are associated with a risk of post-traumatic osteoarthritis due to chondral damage. Magnetic resonance imaging (MRI) techniques provide excellent visualization and assessment of cartilage and can detect subtle and early chondral damage. This is often preceding clinical and radiographic post-traumatic osteoarthritis. Morphologic and quantitative MRI techniques can assess early and progressive degenerative chondral changes after acute ACL injury. Prospective longitudinal cohort. Level 3. Sixty-five participants with acute unilateral ACL injuries underwent bilateral knee MRI scans within 1 month of injury. Fifty-seven participants presented at 6 months, while 54 were evaluated at 12 months. MRI morphologic evaluation using a modified Noyes score assessed cartilage signal alteration, chondral damage, and subchondral bone status. Quantitative T1ρ and T2 mapping at standardized anatomic locations in both knees was assessed. Participant-reported outcomes at follow-up time points were recorded. Baseline Noyes scores of MRI detectable cartilage damage were highest in the injured knee lateral tibial plateau (mean 2.5, standard error (SE) 0.20, P < 0.01), followed by lateral femoral condyle (mean 2.1, SE 0.18, P < 0.01), which progressed after 1 year. Longitudinal prolongation at 12 months in the injured knees was significant for T1ρ affecting the medial and lateral femoral condyles (P < 0.01) and trochlea (P < 0.01), whereas T2 values were prolonged for medial and lateral femoral condyles (P < 0.01) and trochlea (P < 0.01). The contralateral noninjured knees also demonstrated T1ρ and T2 prolongation in the medial and lateral compartment chondral subdivisions. Progressive chondral damage occurred despite improved patient-reported outcomes. After ACL injury, initial and sustained chondral damage predominantly affects the lateral tibiofemoral compartment, but longitudinal chondral degeneration also occurred in other compartments of the injured and contralateral knee. Early identification of chondral degeneration post-ACL injury using morphological and quantitative MRI techniques could enable interventions to be implemented early to prevent or delay PTOA.

Although quantitative T2 mapping magnetic resonance imaging (MRI) is recognized as a non-invasive method for assessing graft maturity after anterior cruciate ligament (ACL) reconstruction, its longitudinal changes and association with clinical outcomes within the first postoperative year are not well established. The purpose of this study was to prospectively investigate hamstring autograft maturity via sequential quantitative T2 mapping and to examine its relationship with patient-reported outcomes and return to sports during the first year after ACL reconstruction. Twenty-seven patients undergoing primary ACL reconstruction with hamstring tendon autografts were enrolled for MRI scans at 3, 6, and 12months after surgery, and 15 patients with healthy ACLs served as controls. The quantitative MRI-based T2 relaxation time and conventional MRI-based signal/noise quotient (SNQ) of the graft were calculated and correlated with the Lysholm score, International Knee Documentation Committee (IKDC) subjective score, Knee Injury and Osteoarthritis Outcome Score (KOOS), and return to preinjury sports levels. T2 relaxation times and SNQ values of the grafts increased from 3 to 6months (p < 0.01) and then decreased from 6 to 12months postoperatively (p < 0.05). Graft T2 relaxation times were significantly lower than those of native ACLs at 3, 6, and 12months postoperatively (p < 0.01). A significant negative correlation was observed between graft T2 relaxation time and the Lysholm score at 6months postoperatively (p = 0.028), as well as with the KOOS pain subscale at 12months (p = 0.023). Patients returning to preinjury sports levels at 12months postoperatively had relatively lower graft T2 relaxation times (p = 0.045) and SNQ values (p = 0.043) compared to those who did not. The graft T2 relaxation time and SNQ value increased during the first 6months, followed by a subsequent reduction from 6 to 12months after ACL reconstruction, and graft T2 relaxation time showed significant negative correlations with the Lysholm score at 6months and with the KOOS pain subscale at 12months postoperatively. Successful return to preinjury sports levels at 12months was associated with lower graft T2 relaxation times and SNQ values. Quantitative MRI T2 mapping may provide an important assessment technique for monitoring graft maturation and guiding return to sports.

ObjectiveThe aim of this study was to investigate texture features from T2 maps as a marker for distinguishing the maturation of repair tissue after 2 different cartilage repair procedures.DesignSeventy-nine patients, after either microfracture (MFX) or matrix-associated chondrocyte transplantation (MACT), were examined on a 3-T magnetic resonance (MR) scanner with morphological and quantitative (T2 mapping) MR sequences 2 years after surgery. Twenty-one texture features from a gray-level co-occurrence matrix (GLCM) were extracted. The texture feature difference between 2 repair types was assessed individually for the femoral condyle and trochlea/anterior condyle using linear regression models. The stability and reproducibility of texture features for focal cartilage were calculated using intra-observer variability and area under curve from receiver operating characteristics.ResultsThere was no statistical significance found between MFX and MACT for T2 values (P = 0.96). There was, however, found a statistical significance between MFX and MACT in femoral condyle in GLCM features autocorrelation (P < 0.001), sum of squares (P = 0.023), sum average (P = 0.005), sum variance (P = 0.0048), and sum entropy (P = 0.05); and in anterior condyle/trochlea homogeneity (P = 0.02) and dissimilarity (P < 0.001).ConclusionTexture analysis using GLCM provides a useful extension to T2 mapping for the characterization of cartilage repair tissue by increasing its sensitivity to tissue structure. Some texture features were able to distinguish between repair tissue after different cartilage repair procedures, as repair tissue texture (and hence, probably collagen organization) 24 months after MACT more closely resembled healthy cartilage than did MFX repair tissue.

Early detection of disc degeneration and categorizing them is very important for the treatment plan and better prognosis. We aimed to assess the efficacy of apparent diffusion coefficient (ADC) mapping and T2 mapping in the early detection and grading of the severity of degenerative disc disease. In this review, the articles published until July 2022, from the PubMed database were used. All articles contained information about the application of ADC and T2 mapping in the detection of disc degeneration. A total of 40 articles were included in this review. We assessed each article for the feasibility of both techniques to categorize the degeneration. ADC values of nucleus pulposus (NP) showed a negative correlation with Pfirrmann grades and age. T2 values of NP and annulus fibrosus (AF) are significantly decreased with an increase in Pfirrmann grades. And also, as age increases, T2 values of NP and posterior AF decreased significantly. ADC and T2 mapping techniques are sensitive in the detection and categorization of disc degeneration. It is highly recommended to include quantitative magnetic resonance imaging techniques in routine spine imaging protocol in a patient with complaints of back pain.

Articular cartilage plays pivotal roles in securing smooth joint kinematics and act as a shock absorber, however, it has minimal healing potential. Chondral injury could lead to the development of osteoarthritis (OA) and therefore is a major clinical concern. There have been marrow stimulating technique and osteochondral transplantation explored to promote cartilage repair. In addition, autologous chondrocyte implantation (ACI) has been developed by Peterson and Brittberg and more than 20,000 cases underwent the procedure all over the world. Recent progress in stem cell research has raised the potential application of stem cell therapy to cartilage repair. In this review, potential application of bone marrow or synovial-derived mesenchymal cells to promote cartilage repair would be discussed.

BackgroundMinimal hepatic encephalopathy (MHE) is a frequent neurocognitive complication in chronic hepatic schistosomiasis (CHS) patients. Conventional diagnostic tools are time-consuming and influenced by education level. Quantitative MRI mapping offers a potential non-invasive biomarker for MHE, but its role in CHS remains unclear.AimThis study aimed to evaluate the diagnostic value of quantitative T1 and T2 mapping for detecting MHE in CHS patients.MethodsThis prospective cross-sectional observational study was conducted from August 2023 to July 2024. A total of 88 CHS patients were enrolled and divided into MHE (n = 50) and non-MHE group (n = 38). MHE was assessed using the number connection test-A (NCT-A) and digit symbol test (DST). All participants underwent 3.0T MRI with T1 and T2 mapping. Group comparisons, correlation analyses, logistic regression, and receiver operating characteristic (ROC) curve analyses were performed.ResultsMHE patients exhibited significantly lower T1 values across multiple brain regions, particularly the globus pallidus (all p < 0.001). T2 values showed no significant differences between groups. Multivariable regression confirmed that lower T1 values were independently associated with MHE (p = 0.009). ROC analysis demonstrated excellent diagnostic performance of globus pallidus T1 values (AUC = 0.92, 95% CI: 0.86–0.99), with sensitivity of 0.97 and specificity of 0.90. T1 values were also correlated with neuropsychological tests (NCT-A: r = −0.345, p < 0.001; DST: r = 0.232, p = 0.029). However, T2 values showed no significant group differences or diagnostic value.ConclusionQuantitative T1 mapping, rather than T2 mapping, could be used as a potential non-invasive biomarker for detecting MHE in CHS patients. This approach offers an objective complement to psychometric testing and may facilitate earlier diagnosis and monitoring of MHE progression.

Background: Quantitative magnetic resonance imaging (MRI) techniques such as T2 mapping may detect early tendon changes following biologic therapies. This study aimed to assess the structural remodeling of the supraspinatus tendon using mean T2 values and T2 distribution profiles after an ultrasound (US)-guided single platelet-rich plasma (PRP) injection. Methods: Twenty-six patients with symptomatic supraspinatus tendinopathy were divided into tendinosis (n = 9) and partial tear (n = 13) groups. T2 mapping and clinical evaluations (shoulder pain and disability index questionnaire (SPADI), Constant-Murley score) were conducted at baseline and 6 months post-PRP. Mean T2 values were measured in three tendon segments (lateral, middle, and medial), and T2 profiles were compared to asymptomatic controls. Results: Clinical outcomes showed significant improvement in both the tendinosis and partial tear groups at the 6-month follow-up. Although no significant changes were observed in the mean T2 relaxation times across tendon segments following PRP treatment, T2 distribution profiling revealed statistically significant alterations in both groups. In the tendinosis group, post-treatment T2 profiles approached those of the asymptomatic controls, suggesting structural remodeling consistent with tendon healing. Conclusions:T2 mapping is an effective tool for detecting tendon remodeling following PRP therapy. Structural improvements indicative of tissue healing were observed in cases of tendinosis, but not in partial tendon tears. These findings support the use of T2 mapping-particularly the T2 distribution profiling-as a quantitative biomarker for assessing treatment response to PRP.

The relationship between early degeneration of articular cartilage and the energyabsorbing abilities of its subchondral bony bed was studied in specimens obtained at autopsy from the knees of 43 male patients. Subchondral bone plugs from patients whose cartilage had only mild mucopolysaccharide loss absorbed relatively less energy on impact than the normals. There was no apparent difference in energy absorption among the bone plugs of the normal, the moderate, and the markedly altered cartilage groups. These changes were not age related.

Comparison of quantitative T2 and ADC mapping in the assessment of 3-nitropropionic acid-induced neurotoxicity in rats