Vesna Gershan


Computed Tomography scanners equipped with system for Automatic Exposure Control (AEC) have been recently installed into clinical practice in Macedonia. Assessment of their AEC settings and performances is important task from patient doses and images quality point of view. This study was done by analyzing of CT examinations in patients in the City Hospital "8 September" in Skopje. The examinations were carried out by GE Bright Speed 16 slices scanner equipped with AEC system. In all patients were applied the same protocol with constant acquisition parameters was applied, and images were reconstructed by standard mode. Patient dimensions and image noise were measured from the scouts and axial images. From DICOM header the information related to dose, TCM and slice position were extracted. It was found that scanner automatic exposure system adjusts exposure mainly according to maximal patient lateral dimension (LR) and applying the same Noise Index (NI) value in patients with different size does not provides necessarily the same image noise level. In patients which LR dimension was less than 30 cm it was found that AEC adjusts tube current at the minimum of mA interval with no modulation throughout different body parts.


AEC response in CT; tube current modulation; image noise; noise index

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