Practical experiences in the transfer of clinical protocols between CT scanners with different ATCM systems

Abstract

Automatic tube current modulation (ATCM) systems to aid in optimizing dose and image noise have become standard on computed tomography (CT) scanners over the last decade. ATCM systems of the main vendors modulate tube current in slightly different ways, with some using a control parameter related to image noise (e.g. Toshiba, GE) while others use a quality reference image mAs (e.g. Siemens). The translation of clinical protocols including ATCM operation between CT scanners from different manufacturers in order to obtain similar levels of image quality with optimized exposure variables has become an important issue. In this study, cylindrical phantoms of different sizes representing small, average and large patients, have been combined into one phantom, which has been scanned on Siemens, Toshiba and GE CT scanners with the full ranges of ATCM image quality settings. The volume weighted CT dose index (CTDI) and image noise over each section of the phantom were recorded for every setting. Relationships between the image quality level settings, and CTDI and measured image noise were analysed in order to investigate ATCM performance. Equations were developed from fits of the data to enable CTDI and image noise to be expressed in terms of the image quality parameters for different size phantoms on each scanner. The Siemens scanner protocol was chosen as the reference, as it avoided high doses for large patients, while allowing full modulation of tube current for patients of all sizes, and so was considered to provide optimized performance. The equations derived were used to equate the noise parameters on Toshiba and GE scanners to the quality reference mAs on the Siemens scanner, so that clinical protocols incorporating similar levels of optimization could be obtained on the three CT scanners.

Explore the Value of Dual Source Computer Tomography Automatic Tube Current Regulation in Reducing the Radiation Dose of CTA in Lower Extremity Vessels

“…Applying the technique of automatic tube current adjustment, appropriately increase the tube current of iliac artery and appropriately decreasing the tube current of thigh and calf artery can ensure the noise consistency of the whole lower limb scanning range and reduce unnecessary radiation dose ( 22 – 24 ). The results of this study showed that there was no significant differences in CT, SD, SNR, and CNR values of femoral artery, popliteal artery and posterior tibial artery between the two groups.…”

Hounsfield Units Measured in Low Dose CT Reliably Assess Vertebral Trabecular Bone Density Changes Over Two Years in Axial Spondyloarthritis

“…The sensitivity analysis excluding vertebrae with incident density abnormalities and artefacts added robustness to the assessment of true changes in trabecular bone density. On the other hand, the sensitivity analysis stratified by centres from different countries (Leiden, Netherlands and Herne, Germany) added to the external validity of the results, limiting the concerns regarding HU values obtained from distinct automatic exposure control implementation and iterative reconstruction algorithms [18,39]. Moreover, the results coming from different CT scanners in different centres (Canon in Leiden, and Siemens in Herne), likely represent the most feasible approach for HU measurements in future studies (especially if multicentric).…”

A study to determine whether the volume-weighted computed tomography dose index gives reasonable estimates of organ doses for thai patients undergoing abdomen and pelvis computed tomography examinations

“…From a previous study on transferring of CT protocols for CT ATCM system, the protocols for both scanners were matched for noise in patients who had cross-sectional areas that approximated to that of the trunk for a large adult Thai patient. [ 10 ] The minimum mAs for the GE scanner was set at 80 mAs to restrict modulation that can affect image quality for small patients, and this resulted in the mAs remaining constant throughout scans for some patients, so data for these individuals were excluded from the study. There is no option for users to select the mAs range for the Siemens scanner, because of the mode of operation, as described above.…”