In vivo 3T spiral imaging based multi‐slice T1ρ mapping of knee cartilage in osteoarthritis

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Abstract
T1ρ describes the spin‐lattice relaxation in the rotating frame and has been proposed for detecting damage to the cartilage collagen‐proteoglycan matrix in osteoarthritis. In this study, a multi‐slice T1ρ imaging method for knee cartilage was developed using spin‐lock techniques and a spiral imaging sequence. The adverse effect of T1 regrowth during the multi‐slice acquisition was eliminated by RF cycling. Agarose phantoms with different concentrations, 10 healthy volunteers, and 9 osteoarthritis patients were scanned at 3T. T1ρ values decreased as agarose concentration increased. T1ρ values obtained with imaging methods were compared with those obtained with spectroscopic methods. T1ρ values obtained during multi‐slice acquisition were validated with those obtained in a single slice acquisition. Reproducibility was assessed using the average coefficient of variation of median T1ρ, which was 0.68% in phantoms and 4.8% in healthy volunteers. There was a significant difference (P = 0.002) in the average T1ρ within patellar and femoral cartilage between controls (45.04 ± 2.59 ms) and osteoarthritis patients (53.06 ± 4.60 ms). A significant correlation was found between T1ρ and T2; however, the difference of T2 was not significant between controls and osteoarthritis patients. The results suggest that T1ρ relaxation times may be a promising clinical tool for osteoarthritis detection and treatment monitoring. Magn Reson Med, 2005.