Quantifiable Imaging Biomarkers for Evaluation of the Posterior Cruciate Ligament Using 3-T Magnetic Resonance Imaging: A Feasibility Study.

BACKGROUND: Quantitative magnetic resonance imaging (MRI) techniques, such as T2 and T2 star (T2*) mapping, have been used to evaluate ligamentous tissue in vitro and to identify significant changes in structural integrity of a healing ligament. These studies lay the foundation for a clinical study that uses quantitative mapping to evaluate ligaments in vivo, particularly the posterior cruciate ligament (PCL). To establish quantitative mapping as a clinical tool for identifying and evaluating chronic or acute PCL injuries, T2 and T2* values first must be determined for an asymptomatic population. PURPOSE: To quantify T2 and T2* mapping properties, including texture variables (entropy, variance, contrast, homogeneity), of the PCL in an asymptomatic population. It was hypothesized that biomarker values would be consistent throughout the ligament, as measured across 3 clinically relevant subregions (proximal, middle, and distal thirds) in the asymptomatic cohort. STUDY DESIGN: Cross-sectional study; Level of evidence, 4. METHODS: Unilateral knee MRI scans were acquired for 25 asymptomatic subjects with a 3.0-T MRI system using T2 and T2* mapping sequences in the sagittal plane. The PCL was manually segmented and divided into thirds (proximal, middle, and distal). Summary statistics for T2 and T2* values were calculated. Intra- and interrater reliability was assessed across 3 raters to 2 time points. RESULTS: The asymptomatic PCL cohort had mean T2 values of 36.7, 29.2, and 29.6 ms in the distal, middle, and proximal regions, respectively. The distal PCL exhibited significantly higher mean, variance, and contrast and lower homogeneity of T2 values than the middle and proximal subregions (P < .05). T2* results exhibited substantial positive skew and were therefore presented as median and quartile (Q) values. Median T2* values were 7.3 ms (Q1-Q3, 6.8-8.9 ms), 7.3 ms (Q1-Q3, 7.0-8.5 ms), and 7.3 ms (Q1-Q3, 6.4-8.2 ms) in the distal, middle, and proximal subregions, respectively. CONCLUSION: This is the first study to identify T2 and T2* mapping values, and their texture variables, for the asymptomatic PCL. The distal third of the PCL had significantly greater T2 values than the proximal or middle thirds. CLINICAL RELEVANCE: T2 and T2* values of the asymptomatic PCL can provide a baseline for comparison with acute and chronic PCL injuries in future studies.

Quantitative MRI characterization of arthroscopically verified supraspinatus pathology: comparison of tendon tears, tendinosis and asymptomatic supraspinatus tendons with T2 mapping.

PURPOSE: Quantitative MRI T2 mapping is a non-invasive imaging technique sensitive to biochemical changes, but no studies have evaluated T2 mapping in pathologic rotator cuff tendons. It was sought to evaluate the efficacy of T2 mapping in detecting differences in the supraspinatus tendon (SST) among patients with tendinosis, partial tears and minimally retracted full-thickness tears, relative to asymptomatic volunteers. METHODS: The pathologic cohort consisted of two arthroscopically verified groups: tendinosis and a tear group of partial tears or minimally retracted full-thickness tears, and was compared to an asymptomatic cohort with no prior history of shoulder pathology. The SST was manually segmented from the footprint to the medial humeral head in the coronal and sagittal planes and divided into six clinically relevant subregions. Mean T2 values and inter- and intra-rater reliability were assessed. RESULTS: In the anterolateral subregion, the tear group exhibited significantly higher mean T2 values (43.9 ± 12.7 ms) than the tendinosis (34.9 ± 3.9 ms; p = 0.006) and asymptomatic (33.6 ± 5.3 ms; p = 0.015) groups. In the posterolateral subregion, the tear group had higher mean T2 values (45.2 ± 13.7) than the asymptomatic group (34.7 ± 6.7; p = 0.012). Inter- and intra-rater reliability was mostly excellent (ICC > 0.75). CONCLUSION: T2 mapping is an accurate non-invasive method to identify quantitatively early rotator cuff pathology. The lateral region in the coronal plane in particular may differentiate partial and small minimally retracted full-thickness tears from tendinosis and asymptomatic tendons. Understanding and being able to measure quantitatively the process of tendon degeneration and subsequent tearing may help clinicians to better predict at-risk groups and to stratify treatment options. LEVEL OF EVIDENCE: III.

Subregional Anatomical Distribution of T2 Values of Articular Cartilage in Asymptomatic Hips.

OBJECTIVE: A standardized definition of normative T2 values across the articular surface of the hip must be defined in order to fully understand T2 values for detecting early degeneration. Therefore, in this article, we seek to lay foundational methodology for reproducible quantitative evaluation of hip cartilage damage using T2 mapping to determine the normative T2 values in asymptomatic individuals. DESIGN: Nineteen prospectively enrolled asymptomatic volunteers (age 18-35 years, males 10, females 9, alpha angle 49.3º ± 7.2º) were evaluated with a sagittal T2 mapping sequence at 3.0 T magnetic resonance imaging. Acetabular and femoral cartilage was manually segmented directly on the second echo of the T2 mapping sequence by 3 raters, twice. Segmentations were divided into 12 subregions modified from the geographic zone method. Median T2 values within each subregion were compiled for further analysis and interrater and intrarater reliability was assessed. RESULTS: In the femur, the posterior-superior subregion was significantly higher (P ≤ 0.05) than those in the posterior-inferior and anterior-inferior subregions. In the acetabulum, the anterior-inferior subregion was significantly higher (P ≤ 0.001) than in the anterior-superior, middle, and posterior-inferior subregions. T2 values of the posterior-superior subregion were significantly higher (P ≤ 0.05) than the anterior-superior, middle, and posterior-inferior subregions. Interrater agreement was generally fair to good.