Published online before print August 26, 2002, 10.1148/radiol.2251011461
Mapping T2 Relaxation Time in the Pediatric Knee: Feasibility with a Clinical 1.5-T MR Imaging System1
Bernard J. Dardzinski, PhD,
Tal Laor, MD,
Vincent J. Schmithorst, PhD,
Lance Klosterman, MD and
T. Brent Graham, MD
1 From the Department of Pediatrics (B.J.D., T.L., V.J.S., L.K.), Department of Radiology (B.J.D., T.L., V.J.S., L.K., T.B.G.), Imaging Research Center (B.J.D., V.J.S.), and Division of Rheumatology (T.B.G.), Children’s Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229. Received August 30, 2001; revision requested October 26; final revision received March 11, 2002; accepted March 25. Supported by an Arthritis Foundation clinical science grant. Address correspondence to B.J.D. (e-mail: bjd@athena.chmcc.org).
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Figure 1. MR images show examples of the six ROIs used for calculations of T2 relaxation time profiles in cartilage. a, Patellar cartilage in the transverse plane, b, patellar cartilage in the sagittal plane, c, non-weight-bearing femoral cartilage, d, weight-bearing femoral cartilage, e, distal femoral physis, f, proximal tibial physis. Yellow lines indicate outlines of the ROIs as generated with CCHIPS/IDL, and red lines indicate example locations of the profiles computed for each ROI. There is no differentiation between unossified epiphyseal and apophyseal cartilage and articular cartilage.
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Figure 2a. Images in a 12-year-old girl with knee pain. (a) Gray-scale transverse T2 relaxation time map through the patella. (b) Transverse T2 relaxation time map through the patella. The color-coded T2 relaxation time map demonstrates the spatial variation in T2 relaxation time values throughout the knee. There is a spatial variation in T2 relaxation time values (range, 37-54 msec) from the subchondral bone toward the articular surface within the patellar cartilage (arrow); this result is similar to those previously published in studies of adult articular cartilage.
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Figure 2b. Images in a 12-year-old girl with knee pain. (a) Gray-scale transverse T2 relaxation time map through the patella. (b) Transverse T2 relaxation time map through the patella. The color-coded T2 relaxation time map demonstrates the spatial variation in T2 relaxation time values throughout the knee. There is a spatial variation in T2 relaxation time values (range, 37-54 msec) from the subchondral bone toward the articular surface within the patellar cartilage (arrow); this result is similar to those previously published in studies of adult articular cartilage.
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Figure 3a. Images in an 8-year-old boy with knee pain. (a) Gray-scale sagittal T2 relaxation time map through the knee. (b) Sagittal T2 relaxation time map through the knee. The color-coded T2 relaxation time map demonstrates spatial variation of T2 relaxation time values throughout the knee. The distal femoral (dashed arrow; T2, 70-87 msec) and proximal tibial (open arrow; T2, 61-72 msec) physes and the non-weight-bearing femoral cartilage (curved arrow; T2, 52-85 msec) have longer T2 values than the weight-bearing femoral cartilage (solid arrow; 40-60 msec).
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Figure 3b. Images in an 8-year-old boy with knee pain. (a) Gray-scale sagittal T2 relaxation time map through the knee. (b) Sagittal T2 relaxation time map through the knee. The color-coded T2 relaxation time map demonstrates spatial variation of T2 relaxation time values throughout the knee. The distal femoral (dashed arrow; T2, 70-87 msec) and proximal tibial (open arrow; T2, 61-72 msec) physes and the non-weight-bearing femoral cartilage (curved arrow; T2, 52-85 msec) have longer T2 values than the weight-bearing femoral cartilage (solid arrow; 40-60 msec).
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Figure 4. Graph shows average T2 relaxation time as a function of normalized distance from the subchondral bone to the articular surface of the patellar cartilage as acquired in two image planes (presented as mean ± SEM). Note the similar spatial variation between transverse and sagittal images. There is a trend toward higher T2 relaxation time values in the sagittal plane. This might reflect the slightly older patient group imaged in the transverse plane or a difference in the orientation of cartilage when imaged in orthogonal planes.
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Figure 5. Graph shows average T2 relaxation time as a function of normalized distance from the subchondral bone to the articular surface of the femur as a function of weight bearing (presented as mean ± SEM). The shorter T2 relaxation time values of weight-bearing cartilage likely reflect compressive effects and resultant decrease in water content.
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Figure 6. Graph shows average T2 relaxation time as a function of normalized distance from the metaphysis to the epiphysis in the distal femoral and proximal tibial physes (presented as mean ± SEM). The relatively longer T2 relaxation times observed in the distal femoral physis may be due to the increased rate of endochondral ossification in the femur compared with that in the tibia at the knee.
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Figure 7. Graph shows average T2 relaxation time profiles as a function of normalized distance in the pediatric knee. This graph is a composite of Figures 4-6 and indicates the trend of the spatial variations. This graph shows the overall trends and ranges of T2 relaxation time values obtained in the pediatric knee. Black line = patellar cartilage imaged in transverse plane, red line = patellar cartilage imaged in sagittal plane, green line = weight-bearing femoral cartilage, orange line = non-weight-bearing femoral cartilage, blue line = distal femoral physis, pink line = proximal tibial physis.
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Copyright © 2002 by the Radiological Society of North America.
