[en] Objective: To investigate the value of perfusion MR imaging in differential diagnosis between primary central nervous system lymphomas (PCNSL)and high grade astrocytomas. Methods: Twelve patients with PCNSL and 23 patients with high grade astrocytomas were preoperatively examined using a 1.5T MR unit. Routine MR sequences were performed followed by dynamic susceptibility contrast- enhanced MR perfusion imaging. The perfusion color images and the time-signal intensity curves of the two tumor groups were compared. The relative cerebral blood volume (rCBV)within the tumor parenchyma was measured and the data were analyzed with unpaired Student's t-test. Results: The rCBVs within the tumor parenchyma of the PCNSL and high grade astrocytomas were 1.78 ± 0.51 and 3.87 ± 0.87 respectively. The rCBV in the PCNSL was significantly lower than that of the high grade astrocytoma (P<0.05). When the time-signal intensity curves were compared, the PCNSL showed a trend towards the baseline after the first pass and the curves even overshot above the baseline in 7 out of 12 cases, whereas the high grade astrocytoma showed a trend to be close to the baseline but couldn't return to the baseline completely. Conclusion: The MR perfusion imaging can be very useful in distinguishing the PCNSL from high grade astrocytomas. (authors)