Objectives: We sought to determine whether radiation dose can be reduced and image quality improved in computed tomography (CT) images of the brain that were acquired with automated exposure control (AEC), organ-based tube current modulation (TCM), multiband filtration (MBF), and iterative reconstruction in image space (IRIS).
Methods: An Alderson-Rando-phantom, equipped with thermoluminescent dosimeters, was used to determine the radiation exposure of organs within the head and neck by different CT brain scan modes. We measured the noise and signal-to-noise ratios and subjectively graded quality criteria in different territories of the brain in spiral CT images of 150 patients. We also derived the radiation exposure from the patient protocols.
Results: In the phantom, AEC and TCM reduced the radiation exposure of the lenses, cerebrum, cerebellum, and thyroid gland by 41.9%, 34.5%, 30.5%, and 34.9%, respectively. Brain CT scans from patients investigated with AEC, TCM, MBF, and IRIS were found to have significantly better image quality than with conventional filtered back projection. In addition, the CT dose index and dose-length product were significantly lower with AEC, TCM, MBF, and IRIS by 24.1% and 20.2%, respectively.
Conclusion: The combination of AEC, TCM, MBF, and IRIS improves image quality while radiation exposure can be reduced, particularly in dose-sensitive organs, such as the lenses and thyroid gland.