UC San Diego

Background

T_1ρ has been extensively reported as a sensitive biomarker of biochemical changes in the nucleus pulposus (NP) and annulus fibrosis of intervertebral discs (IVDs). However, no T_1ρ study of cartilaginous endplates (CEPs) has yet been reported because the relatively long echo times (TEs) of conventional clinical T_1ρ sequences cannot effectively capture the fast-decaying magnetic resonance signals of CEPs, which have very short T₂/T₂*s. This can be overcome by using ultrashort echo time (UTE) T_1ρ acquisitions.

Methods

Seventeen subjects underwent UTE with adiabatic T_1ρ preparation (UTE-Adiab-T_1ρ) and T₂-weighted fast spin echo imaging of their lumbar spines. Each IVD was manually segmented into seven regions (i.e., outer anterior annulus fibrosis, inner anterior annulus fibrosis, outer posterior annulus fibrosis, inner posterior annulus fibrosis, superior CEP, inferior CEP, and NP). T_1ρ values of these sub-regions were correlated with IVD modified Pfirrmann grades and subjects' ages. In addition, T_1ρ values were compared in subjects with and without low back pain (LBP).

Results

Correlations of T_1ρ values of the outer posterior annulus fibrosis, superior CEP, inferior CEP, and NP with modified Pfirrmann grades were significant (P<0.05) with R values of 0.51, 0.36, 0.38, and -0.94, respectively. Correlations of T_1ρ values of the outer anterior annulus fibrosis, outer posterior annulus fibrosis, and NP with ages were significant with R equal to 0.52, 0.71, and -0.76, respectively. T_1ρ differences of the outer posterior annulus fibrosis, inferior CEP, and NP between the subjects with and without LBP were significant (P=0.005, 0.020, and 0.000, respectively).

Conclusions

The UTE-Adiab-T_1ρ sequence can quantify T_1ρ of whole IVDs including CEPs. This is an advance, and of value for comprehensive assessment of IVD degeneration.