[en] Purpose: The aim was to investigate the use of perfusion CT of the brain in the assessment of flow alterations during brachytherapy of meningiomas. Material and Methods: Six patients with an intracranial meningioma were investigated during brachytherapy treatment by sterotactic implantation of I-125 seeds. Cerebral blood flow (CBF) in the tumour centre and the tumour periphery as well as in the normal brain parenchyma was determined by perfusion CT. Follow-up examinations were performed during the first year after the implantation. The CBF of the normal brain parenchyma was used as control. Results: In the beginning of therapy, the mean ±SEM blood flow in the tumour centre was 231.4±58.1 ml/100 g/min and in the periphery 223.5±53.8 ml/100 g/min. Within three months after the iodine seed implantation, the tumour blood flow had decreased 41%. At the one-year follow-up, the tumour blood flow in the centre had decreased to 68.7±45.9 ml/100 g/min. In the periphery of the tumour, it remained nearly unchanged (199.3±101.0 ml/100 g/min). The CBF values obtained form normal brain parenchyma did not decrease during the treatment. Throughout the study, the mean CBF for the normal grey matter was 38.5±2.9 ml/100 g/min, and 22.3±1.2 ml/100 g/min for the normal white matter. Conclusion: Perfusion CT seems to enable accurate monitoring of the blood flow of meningiomas during brachytherapy, and could be used in clinical situations where blood flow changes in brain and tumours should be investigated. (orig.)