Object: The. diagnosis of low-grade glioma (LGG) cannot be based exclusively on conventional magnetic resonance (MR) imaging studies, and target selection for stereotactic biopsy is a crucial issue given the high risk of sampling errors. The authors hypothesized that perfusion-weighted imaging could provide information on the microcirculation in presumed supratentorial LGGs.
Methods: All adult patients with suspected (nonenhancing) supratentorial LGGs on conventional MR imaging between February 2001 and February 2004 were included in this study. Preoperative MR imaging was performed using a dynamic first-pass gadopentate dimeglumine-enhanced spin echo-echo planar perfusion-weighted sequence, and the tumors' relative cerebral blood volume (rCBV) measurements were expressed in relation to the values observed in contralateral white matter. In patients with heterogeneous tumors a stereotactic biopsy was performed in the higher perfusion areas before resection. Among 21 patients (16 men and five women with a mean age of 36 years, range 23-60 years), 10 had diffuse astrocytomas (World Health Organization Grade II) and 11 had other LGGs and anaplastic gliomas. On perfusion-weighted images demonstrating heterogeneous tumors, areas of higher rCBV focus were found to be oligodendrogliomas or anaplastic astrocytomas on stereotactic biopsy; during tumor resection, however, specimens were characterized predominantly as astrocytomas. Diffuse astrocytomas were associated with significantly lower mean rCBV values compared with those in the other two lesion groups (p < 0.01). The rCBV ratio cutoff value that permitted better discrimination between diffuse astrocytomas and the other lesion groups was 1.2 (80% sensitivity and 100% specificity).
Conclusions: Perfusion-weighted imaging is a feasible method of reducing the sampling error in the histopathological diagnosis of a presumed LGG, particularly by improving the selection of targets for stereotactic biopsy.