Rationale and objectives: Dynamic contrast material-enhanced magnetic resonance (MR) imaging may be used to quantify fractional blood volume (fBV) and microvascular permeability in human brain tumors. Hypothesis is that these measurements correlate with tumor histologic grade and immunohistologically assessed mitotic activity.
Materials and methods: Thirty-eight patients with newly diagnosed gliomas underwent MR imaging consisting of dynamic three-dimensional spoiled gradient-recalled acquisition in the steady state image sets following bolus injections of a single dose of gadodiamide. Signal intensity changes in blood and tissue were kinetically analyzed, yielding estimates of fBV and microvascular permeability (k). Tumor specimens were graded with the World Health Organization-II four-point grading score. MIB-1 immunohistochemical labeling (anti-Ki-67 monoclonal antibody) was performed in 22 patients to evaluate mitotic activity.
Results: Histologic study revealed nine grade 2, 14 grade 3, and 15 grade 4 tumors. fBV ranged from 0.4% to 24%, k from -0.4 to 31.4 mL/100 cm3 x min, and MIB-1 labeling indexes from 1.7% to 42.8%. Correlation to the tumor grade was highest for permeability (r = 0.73), followed by the MIB-1 index (r = 0.63), and fBV (r = 0.48). Correlation between k and MIB-1 index was strong (r = 0.84). There was no statistically significant difference between the fBV of any of the groups. Despite some overlap between the permeability values of specific tumors from different grades, differences were statistically significant. The MIB-1 index was significantly different between grades 3 and 4 but not between grades 2 and 3.
Conclusion: Dynamic contrast-enhanced MR imaging allows noninvasive determination of tumor fBV and microvascular permeability k. k is more reliable than the MIB-1 labeling index for differentiating grade 2 from grade 3 tumors.