Radiation Dose Modulation Techniques in the Multidetector CT Era: From Basics to Practice

Abstract

Radiation exposure to the patient has become a concern for the radiologist in the multidetector computed tomography (CT) era. With the introduction of faster multidetector CT scanners, various techniques have been developed to reduce the radiation dose to the patient; one method is automatic exposure control (AEC). AEC systems make use of different types of control, including patient-size AEC, z-axis AEC, rotational or angular AEC, or a combination of two or more of these types. AEC systems operate on the basis of several methods: standard deviation, noise index, reference milliamperage, and reference image. A clear understanding of how to use different AEC systems on different multidetector CT scanners will allow users to modulate radiation dose, reduce photon starvation artifacts, and maintain image quality throughout the body. Further development of AEC systems and their successful introduction into clinical practice will require user education and good communication between users and manufacturers.

Comparison of Radiation Dose and Image Quality with Various Computed-Tomography Scout Views: The Angular Modulation Technique Based on Information Calculated from Scout Views

“…This using only single scout view can lead to inappropriate CT scanning and dose reduction failure using SmartmA. As the frontal scout view alone, without information from lateral scout views, failed to achieve a suitable noise index at the center of the y-axis of the patient in CT scanning, two-scout views are necessary to obtain quality CT images while limiting patient radiation exposure to a proper dose (9,15).…”

“…This variation was most likely due to the properties of the unit that could affect CT studies involving scouts. The CTDI results did not differ significantly between using AutomA alone and using both AutomA and SmartmA, likely because this test was conducted in a single phantom rather than in diverse human body types (8,9,14). In general, AEC adjusts the tube current to the regional body anatomy for the purpose of reducing radiation doses in projection angles.…”

“…Using chest CT, causing the lateral reduction to be more significant than the anteroposterior (AP) reduction (11). Consequently, in CT involving the AEC technique, the radiation dose in scout scanning is determined by the patient's body type, including body size, body shape, and anatomic location, as well as by the fixed noise index (9)(10)(11)(12). As the scout information determines the radiation dose for a CT scan in the AEC technique, we speculated that the location and order of the X-ray tubes could also affect the radiation dose during a CT scan (13).…”

Reproducibility and variability of very low dose hepatic perfusion CT in metastatic liver disease

“…All perfusion scans were performed successfully and analyzed by the software. The mean effective dose of all perfusion studies was 2.9 mSv, calculated as the dose-length product (DLP) multiplied by a tissue weighting factor for the abdomen (k=0.015) (17). DLP was obtained from the dose report of each CT scan.…”

Investigation of the characteristics of Automatic Exposure Control (AEC) of a Computed Tomography (CT) scanner by utilising cylindrical and anthropomorphic phantoms

“…The modulation of tube current can be influenced by patient positioning [6][7][8], size, attenuation properties in different regions of the body, and technical factors such as tube potential (kVp), Quality reference mAs (QRM) and pitch [9][10][11]. QRM is the technical factor used by Siemens AEC system (CARE Dose4D) to represent the required image quality.…”