In vivo 3T spiral imaging based multi‐slice T 1ρ mapping of knee cartilage in osteoarthritis

T 1ρ 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 T 1ρ imaging method for knee cartilage was developed using spin‐lock techniques and a spiral imaging sequence. The adverse effect of T 1 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. T 1ρ values decreased as agarose concentration increased. T 1ρ values obtained with imaging methods were compared with those obtained with spectroscopic methods. T 1ρ 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 T 1ρ , which was 0.68% in phantoms and 4.8% in healthy volunteers. There was a significant difference ( P = 0.002) in the average T 1ρ 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 T 1ρ and T 2 ; however, the difference of T 2 was not significant between controls and osteoarthritis patients. The results suggest that T 1ρ relaxation times may be a promising clinical tool for osteoarthritis detection and treatment monitoring. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.