A technique is described for the detection and vascular characterisation of intracranial lesions which consists of the administration of 99mTc (15 mCi) by intravenous bolus injection followed by rapid sequential recording using an Anger Camera, 1600 channel analyser and a magnetic tape transport and memory system. Using this method, and after correlation with 10 normals it was possible to demonstrate in 46 patients with proved intracranial lesions an increase or decrease of activity corresponding to the nature of the lesion.