Feasibility of using limited-population-based average R10 for pharmacokinetic modeling of osteosarcoma dynamic contrast-enhanced magnetic resonance imaging data

Retrospective analyses of clinical dynamic contrast-enhanced (DCE) MRI studies may be limited by failure to measure the longitudinal relaxation rate constant (R1) initially, which is necessary for quantitative analysis. In addition, errors in R1 estimation in each individual experiment can cause inconsistent results in derivations of pharmacokinetic parameters, Ktrans and ve, by kinetic modeling of the DCE-MRI time course data. A total of 18 patients with lower extremity osteosarcomas underwent multislice DCE-MRI prior to surgery. For the individual R1 measurement approach, the R1 time course was obtained using the two-point R1 determination method. For the average R10 (precontrast R1) approach, the R1 time course was derived using the DCE-MRI pulse sequence signal intensity equation and the average R10 value of this population. The whole tumor and histogram median Ktrans (0.57±0.37 and 0.45±0.32 min−1) and ve (0.59±0.20 and 0.56±0.17) obtained with the individual R1 measurement approach are not significantly different (paired t test) from those (Ktrans: 0.61±0.46 and 0.44±0.33 min−1; ve: 0.61±0.19 and 0.55±0.14) obtained with the average R10 approach. The results suggest that it is feasible, as well as practical, to use a limited-population-based average R10 for pharmacokinetic modeling of osteosarcoma DCE-MRI data.