Repeatability of dynamic contrast enhanced v parameter in healthy subjects and patients with brain tumors.

PURPOSE

To study the repeatability of plasma volume (v) extracted from dynamic-contrast-enhanced (DCE) MRI in order to define threshold values for significant longitudinal changes, and to assess changes in patients with high-grade-glioma (HGG).

METHODS

Twenty eight healthy subjects, of which eleven scanned twice, were used to assess the repeatability of v within the normal-appearing brain tissue and to define threshold values for significant changes based on least-detected-differences (LDD) of mean v values and histogram comparisons using earth-mover's-distance (EMD). Sixteen patients with HGG were scanned longitudinally with eight patients scanned before and following bevacizumab therapy. Longitudinal changes were assessed based on defined threshold values in comparison to RANO criteria.

RESULTS

The threshold values for significant changes were: LDD = 0.0024 (ml/100 ml, 21%) for mean v and EMD = 4.14. In patients, in 20/24 comparisons, no significant longitudinal changes were detected for v within the normal-appearing brain tissue. Concurring results were obtained between changes in lesion volume (RANO criteria) and LDD or EMD values in cases diagnosed with progressive-disease, yet in about 50% of cases diagnosed with partial-response preliminary results demonstrated significant increase in v despite significant reductions in lesion volume. In two patients, these changes preceded progression detected at follow-up scans. In general, a good concordance was obtained between LDD and EMD.

CONCLUSION

This study shows high repeatability of v and provides threshold values for significant changes in longitudinal assessment of patients with brain tumors. Preliminary results suggest the use of v-DCE parameter to improve assessment of therapy response in patients with high-grade-glioma.