Late temporal lobe necrosis in patients with nasopharyngeal carcinoma: evaluation with combined multi-section diffusion weighted. and perfusion weighted MR imaging

Late temporal lobe necrosis is a well-known and serious complication in pat ients with nasopharyngeal carcinoma (NPC) following radiotherapy. Owing to the close proximity to the skull base, the medial temporal lobes are inevit ably included in the target volume of irradiation. Patients with NPC provid e a unique opportunity in study of delay radiation effect in normal human b rain. The objective of this study was to evaluate late temporal lobe radiat ion injury by combined multi-section diffusion weighted and perfusion weigh ted MR imaging. We prospectively studied 16 patients with typical clinical symptoms of late temporal lobe necrosis or other abnormalities in the tempo ral lobes incidentally detected by conventional MR imaging. All patients ha d a previous history of radiotherapy for histologically proven NPC. Convent ional T1- and T2-weighted images, fast gradient echo with echo-planar diffu sion-weighted and perfusion-weighted MR imaging were performed. Apparent di ffusion coefficient (ADC) map and relative cerebral blood volume (rCBV) map were computed via commercially available software. MR diffusion and perfus ion images were then analyzed and graded by two independent observers with focusing on the diffusion and perfusion mismatch. The temporal lobe lesions displayed marked high diffusion on the ADC map. The rCBV map also revealed marked hypoperfusion in these temporal lobe lesions in all patients. The a reas of abnormality on the rCBV map were significantly larger than the lesi ons on the ADC map in 14 patients (observer 1) and 13 patients (observer 2) . Since late temporal lobe necrosis is probably caused by damage of the end othelium of vessels and ischemia, perfusion and diffusion mismatch might im ply injured tissue but potentially salvageable brain tissue. A mismatch may be potentially used to predict the response to treatment in-patients with late temporal lobe necrosis. (C) 2001 Elsevier Science Ireland Ltd. All rig hts reserved.