Usefulness of perfusion- and diffusion-weighted imaging to differentiate between pilocytic astrocytomas and high-grade gliomas. A multicenter study in Japan

Imaging findings of pilocytic astrocytoma (PA) vary widely, sometimes resembling those of high-grade glioma (HGG). This study aimed to identify the imaging parameters that can be used to differentiate PA from HGG. Altogether, 60 patients with PAs and 138 patients with HGGs were included in the study. Tumor properties and the presence of hydrocephalus, peritumoral edema, and dissemination were evaluated. We also measured the maximum relative cerebral blood flow (rCBF_max) and volume (rCBV_max) and determined the minimum apparent diffusion coefficient (ADC_min) in the tumor's solid components. The relative T1 (rT1), T2 (rT2), and contrast-enhanced T1 (rCE-T1) intensity values were evaluated. Parameters were compared between PAs and HGGs using the Mann-Whitney U test. Receiver operating characteristic (ROC) curve analysis was also used to evaluate these imaging parameters. A value of P <.05 was considered to indicate significance. Intratumoral hemorrhage and calcification were observed in 10.0% and 21.7% of PAs, respectively. The rCBF_max and rCBV_max values were significantly lower in PAs (0.50 ± 0.35, 1.82 ± 1.21) than those in HGGs (2.98 ± 1.80, 9.54 ± 6.88) (P <.0001, P =.0002, respectively). The ADC_min values were significantly higher in PAs (1.36 ± 0.56 x 10^-3 mm²/s) than those in HGGs (0.86 ± 0.37 x 10^-3 mm²/s) (P <.0001). ROC analysis showed that the best diagnostic performance was achieved with rCBF_max. The rCBF_max, rCBV_max, and ADC_min can differentiate PAs from HGGs. (orig.)