UC San Diego

Purpose

The development of ultrashort echo time (UTE) MRI sequences has led to improved imaging of tissues with short T₂ relaxation times, such as the deep layer cartilage and meniscus. UTE combined with adiabatic T_1ρ preparation (UTE-Adiab-T_1ρ) is an MRI measure with low sensitivity to the magic angle effect. This study aimed to investigate the sensitivity of UTE-Adiab-T_1ρ to mechanical load-induced deformations in the tibiofemoral cartilage and meniscus of human cadaveric knee joints.

Methods

Eight knee joints from young (42 ± 12 years at death) donors were evaluated on a 3 T scanner using the UTE-Adiab-T_1ρ sequence under four sequential loading conditions: load = 0 N (Load0), load = 300 N (Load1), load = 500 N (Load2), and load = 0 N (Unload). UTE-Adiab-T_1ρ was measured in the meniscus (M), femoral articular cartilage (FAC), tibial articular cartilage (TAC), articular cartilage regions uncovered by meniscus (AC-UC), and articular cartilage regions covered by meniscus (AC-MC) within region of interests (ROIs) manually selected by an experienced MR scientist. The Kruskal-Wallis test, with corrected significance level for multiple comparisons, was used to examine the UTE-Adiab-T_1ρ differences between different loading conditions.

Results

UTE-Adiab-T_1ρ decreased in all grouped ROIs under both Load1 and Load2 conditions (-18.7% and - 16.9% for M, -18.8% and - 12.6% for FAC, -21.4% and - 10.7% for TAC, -26.2% and - 13.9% for AC-UC, and - 16.9% and - 10.7% for AC-MC). After unloading, average UTE-Adiab-T_1ρ increased across all ROIs and within a lower range compared with the average UTE-Adiab-T_1ρ decreases induced by the two previous loading conditions. The loading-induced differences were statistically non-significant.

Conclusions

While UTE-Adiab-T_1ρ reduction by loading is likely an indication of tissue deformation, the increase of UTE-Adiab-T_1ρ within a lower range by unloading implies partial tissue restoration. This study highlights the UTE-Adiab-T_1ρ technique as an imaging marker of tissue function for detecting deformation patterns under loading.