Abnormalities in the recirculation phase of contrast agent bolus passage in cerebral gliomas: comparison with relative blood volume and tumor grade.

BACKGROUND AND PURPOSE Abnormalities in the recirculation phase of the passage of a contrast agent bolus have been identified in tumors and have been suggested to represent vascular tortuosity and hypoperfusion in areas of angiogenic neovascularization. This study was performed to examine the hypothesis that these abnormalities provide information concerning the microcirculation related to tumor grade in patients with cerebral glioma. METHODS Contrast-enhanced dynamic susceptibility MR imaging was performed in 27 patients with glioma. Residual relaxivity effects were minimized by injection of contrast agent before dynamic imaging. Maps of relative cerebral blood volume (rCBV) and relative recirculation (rR) were calculated, and values from enhancing tumor tissue were compared with tumor grade. RESULTS Histologic grades were grade II, astrocytoma (n = 3); grade III, anaplastic astrocytoma (n = 10); and grade IV, glioblastoma multiforme (n = 14). rCBV values varied among tumor grades, with higher mean values in higher grade tumors (P <.001). Mean rR values in grade II tumors were not significantly different from those in normal gray and white matter. Mean rR values in grades III and IV tumors were similar and were significantly higher than those in grade II tumors (P <.01). The distribution of the pixel values of rR showed significant differences between grades III and IV tumors (P <.001), with low values of skewness in keeping with a normal distribution in grade III tumors and higher values in grade IV tumors. CONCLUSION Variation in the recirculation characteristics of a contrast agent bolus is related to tumor grade in gliomas. This supports the hypothesis that abnormalities in contrast agent recirculation provide independent information concerning the microcirculation in imaging studies of angiogenesis and may be of value as surrogate markers in trials of antiangiogenic therapy.