Perfusion and diffusion MR imaging in enhancing malignant cerebral tumors

Abstract

Objective Common contrast-enhancing malignant tumors of the brain are glioblastoma multiforme (GBMs), anaplastic astrocytomas (AAs), metastases, and lymphomas, all of which have sometimes similar conventional MRI findings. Our aim was to evaluate the role of perfusion MR imaging (PWI) and diffusion-weighted imaging (DWI) in the differentiation of these contrast-enhancing malignant cerebral tumors. Materials and methods Forty-eight patients with contrast-enhancing and histologically proven brain tumors, 14 AAs, 17 GBMs, nine metastases, and eight lymphomas, were included in the study. All patients have undergone routine MR examination where DWI and PWI were performed in the same session. DWI was performed with b values of 0, 500, and 1000 mm 2/s. Minimum ADC values (ADC min) of each tumor was later calculated from ADC map images. PWI was applied using dynamic susceptibility contrast technique and maximum relative cerebral blood volume (rCBV max) was calculated from each tumor, given in ratio with contralateral normal white matter. Comparisons of ADC min and rCBV max values with the histological types of the enhancing tumors were made with a one-way analysis of variance and Bonferroni test. A P value less than 0.05 indicated a statistically significant difference. Results The ADC min values (mean ± S.D.) in GBMs, AAs, lymphomas, and metastases were 0.79 ± 0.21 (×10 −3 mm 2/s), 0.75 ± 0.21 (×10 −3 mm 2/s), 0.51 ± 0.09 (×10 −3 mm 2/s), and 0.68 ± 0.11 (×10 −3 mm 2/s), respectively. The difference in ADC min values were statistically significant between lymphomas and GBMs ( P < 0.05). It was also statistically significant between lymphomas and AAs ( P < 0.03). However, there were no differences between lymphomas and metastasis, and between GBMs, AAs, and metastasis. The rCBV max ratio (mean ± S.D.) in GBMs were 6.33 ± 2.03, whereas it was 3.66 ± 1.79 in AAs, 2.33 ± 0.68 in lymphomas, and 4.45 ± 1.87 in metastases. These values were statistically different between GBMs and AAs ( P < 0.001), GBMs and lymphoma ( P < 0.0001). Although there seemed to be difference between GBMs and metastases, it was not statistically significant ( P < 0.083). Conclusion Combination of DWI and PWI, with ADC min and rCBV max calculations, may aid routine MR imaging in the differentiation of common cerebral contrast-enhancing malignant tumors.