MRI characteristics and transverse relaxation time measurements in normal growing cartilage

To determine the characteristics of magnetic resonance (MR) signals of normal growing cartilage and identify the difference in transverse relaxation times between physeal and epiphyseal cartilage in vivo. 24 distal femora of 12 two-week-old piglets were imaged on a 1.5 Tesla GE MR scanner. Comparison was made between signal intensity on MR images and the structure shown in corresponding histologic sections. T2 values were measured in eight piglets by means of multiecho spin-echo sequences. Our results showed that MR imaging delineated five regions between the secondary ossification center and the metaphysis, which histologically correspond to the zone of provisional calcification of the secondary ossification center, physis of the secondary ossification center, epiphyseal cartilage, physis and zone of provisional calcification. The T2 value in the physeal cartilage was much larger than that in the epiphyseal cartilage (P<0.05). It is concluded that MRI findings could differentiate the different regions of growing cartilage. T2 is longer in physeal than in epiphyseal cartilage, perhaps reflecting differences in water binding by proteoglycans.