T1rho relaxation quantification using spiral imaging: a preliminary study

Do cartilage repair procedures prevent degenerative meniscus changes?: longitudinal t1ρ and morphological evaluation with 3.0-T MRI

BACKGROUND

Cartilage repair (CR) procedures are widely accepted for treatment of isolated cartilage defects in the knee joint. However, it is not well known whether these procedures prevent degenerative joint disease.

HYPOTHESIS

Cartilage repair procedures prevent accelerated qualitative and quantitative progression of meniscus degeneration in individuals with focal cartilage defects.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Ninety-four subjects were studied. Cartilage repair procedures were performed on 34 patients (osteochondral transplantation, n = 16; microfracture, n = 18); 34 controls were matched. An additional 13 patients received CR and anterior cruciate ligament (ACL) reconstruction (CR&ACL), and 13 patients received only ACL reconstruction. Magnetic resonance imaging at 3.0-tesla with T(1ρ) mapping and sagittal fat-saturated intermediate-weighted fast spin echo (FSE) sequences was performed to quantitatively and qualitatively analyze menisci (Whole-Organ Magnetic Resonance Imaging Score [WORMS] assessment). Patients in the CR and CR&ACL groups were examined 4 months (n = 34; n = 13), 1 year (n = 21; n = 8), and 2 years (n = 9; n = 5) after CR. Control subjects were scanned at baseline and after 1 and 2 years, ACL patients after 1 and 2 years.

RESULTS

At baseline, global meniscus T(1ρ) values (mean ± SEM) were higher in individuals with CR (14.2 ± 0.5 ms; P = .004) and in individuals with CR&ACL (17.1 ± 0.9 ms; P < .001) when compared with controls (12.8 ± 0.6 ms). After 2 years, there was a statistical difference between T(1ρ) at the overlying meniscus above cartilage defects (16.4 ± 1.0 ms) and T(1ρ) of the subgroup of control knees without cartilage defects (12.1 ± 0.8 ms; P < .001) and a statistical trend to the CR group (13.3 ± 1.0 ms; P = .09). At baseline, 35% of subjects with CR showed morphological meniscus tears at the overlying meniscus; 10% of CR subjects showed an increase in the WORMS meniscus score within the first year, and none progressed in the second year. Control subjects with (without) cartilage defects showed meniscus tears in 30% (5%) at baseline; 38% (19%) increased within the first year, and 15% (10%) within the second year.

CONCLUSION

This study demonstrated more severe meniscus degeneration after CR surgery compared with controls. However, progression of T(1ρ) values was not observed from 1 to 2 years after surgery. These results suggest that CR may prevent degenerative meniscus changes.

Relationship between knee kinetics during jumping tasks and knee articular cartilage MRI T1rho and T2 relaxation times

BACKGROUND

Articular cartilage of young healthy individuals is dynamic and responsive to loading behaviors. The purpose of this study was to evaluate the relationship of cartilage T(1ρ) and T(2) relaxation times with loading kinetics during jumping tasks in healthy young individuals.

METHODS

Fourteen healthy subjects underwent: 1) motion analysis while performing a unilateral hopping task and bilateral drop jumping task; and 2) quantitative imaging using a 3 Tesla MRI for T(1ρ) and T(2) relaxation time analysis. Three dimensional net joint moments and angular impulse was calculated using standard inverse dynamics equations. Average T(1ρ) and T(2) relaxation times and medial-lateral ratios for each were calculated. Multiple regression was used to identify predictors of cartilage relaxation times.

FINDINGS

Average knee flexion moment during hopping was observed to best predict overall T(1ρ) (R(2)=.185) and T(2) (R(2)=.154) values. Peak knee adduction moment during a drop jump was the best predictor of the T(1ρ) medial-lateral ratio (R(2)=.220). The T(2) medial-lateral ratio was best predicted by average internal rotation moment during the drop jump (R(2)=.174).

INTERPRETATION

These data suggest that loads across the knee may affect the biochemistry of the cartilage. In young healthy individuals, higher flexion moments were associated with decreased T(1ρ) and T(2) values, suggesting a potentially beneficial effect. The medial-to-lateral ratio of T(1ρ) and T(2) times appears to be related to the frontal and transverse plane joint mechanics. These data offer promising findings of potentially modifiable parameters associated with cartilage composition.

Comparison of T1rho measurements in agarose phantoms and human patellar cartilage using 2D multislice spiral and 3D magnetization prepared partitioned k-space spoiled gradient-echo snapshot techniques at 3 T

OBJECTIVE

The purpose of this article is to compare in vitro T1rho measurements in agarose phantoms and articular cartilage specimens using 2D multislice spiral and 3D magnetization prepared partitioned k-space spoiled gradient-echo snapshot MRI sequences.

MATERIALS AND METHODS

Six phantoms (agarose concentration, 2%, 3%, and 4%; n = 2 each) and 10 axially sliced patellar specimens from five cadaveric donors were scanned at 3 T. T1rho-weighted images were acquired using 2D spiral and 3D magnetization prepared partitioned k-space spoiled gradient-echo snapshot sequences. Regions of interest were analyzed to measure T1rho values centrally within phantoms, to evaluate effects of pulse sequence and agarose concentration. In patellar specimens, regions of interest were analyzed to measure T1rho values with respect to anatomic location (the medial and lateral facets and the median ridge in deep and superficial halves of the cartilage) as well as location that exhibited magic angle effect in proton density-weighted images, to evaluate the effects of pulse sequence, anatomic location, and magic angle.

RESULTS

In phantoms, T1rho values were similar (p = 0.9) between sequences but decreased significantly (p < 0.001), from ∼55 to ∼29 milliseconds, as agarose concentration increased from 2% to 4%. In cartilage specimens, T1rho values were also similar between sequences (p = 0.3) but were significantly higher (p < 0.001) in the superficial layer (95-120 milliseconds) compared with the deep layer (45-75 milliseconds).

CONCLUSION

T1rho measurements of human patellar cartilage specimens and agarose phantoms using 2D spiral and 3D magnetization prepared partitioned k-space spoiled gradient-echo snapshot sequences gave similar values. Lower T1rho values for phantoms with higher agarose concentrations and proteoglycan concentrations that are higher in deeper layers of cartilage than in superficial layers suggest that our method is sensitive to concentration of macromolecules in biologic tissues.