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 (R(1)) initially, which is necessary for quantitative analysis. In addition, errors in R(1) estimation in each individual experiment can cause inconsistent results in derivations of pharmacokinetic parameters, K(trans) and v(e), 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 R(1) measurement approach, the R(1) time course was obtained using the two-point R(1) determination method. For the average R(10) (precontrast R(1)) approach, the R(1) time course was derived using the DCE-MRI pulse sequence signal intensity equation and the average R(10) value of this population. The whole tumor and histogram median K(trans) (0.57+/-0.37 and 0.45+/-0.32 min(-1)) and v(e) (0.59+/-0.20 and 0.56+/-0.17) obtained with the individual R(1) measurement approach are not significantly different (paired t test) from those (K(trans): 0.61+/-0.46 and 0.44+/-0.33 min(-1); v(e): 0.61+/-0.19 and 0.55+/-0.14) obtained with the average R(10) approach. The results suggest that it is feasible, as well as practical, to use a limited-population-based average R(10) for pharmacokinetic modeling of osteosarcoma DCE-MRI data.