Aim: Investigating the incidence of non-renal acute adverse events (AAEs) in patients undergoing unenhanced or enhanced computed tomography (CT) or magnetic resonance (MR) (four groups) using the active interview-method. Methods: The imaging procedure followed the standards of the department. Furthermore, the iodine-based (nonionic monomer) and gadolinium-based (cyclic) contrast agent was the same as used for all other examinations in the department. All patients were interviewed for 72 hours

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... ter the MR or CT examination regarding occurrence of AAEs using a structured questionnaire. Results: A total of 1358 patients (259 with enhanced MR, 434 with unenhanced MR, 450 with enhanced CT and 215 with unenhanced CT) were enrolled. AAEs were significantly higher (P < 0.05) in the contrast enhanced MR [48 (18.5%)] and CT [35 (7.7%)] groups compared to unenhanced MR [39 (9.0%)] and CT [5 (2.3%)] groups. Dizziness was significantly [19 (7.3%), (P < 0.05)] more frequent in the enhanced MR. The same AAEs were reported in both contrast groups and control groups. Conclusion: AAEs which are mainly considered to be caused by the contrast medium are also experienced by patients undergoing CT or MR without contrast. Enhanced MR is correlated with more reactions than unenhanced MR and enhanced CT. Dizziness was reported more frequently after MR than CT, both with and without contrast; more patients were CNS examined with MR and with CT.