Objectives: The aim of this study is to evaluate the various automatic tube current modulation combined with iterative reconstruction (iDose4) in commercially available positron emission computed tomography/computed tomography (PET/CT, Philips healthcare) imaging scanner. Methods: A Rando phantom was scanned according to the high dose routine protocol (CTDI=19.3 mGy) using Atomic Exposure Control (Dose Right) with two different dose right modulation Z and 3D modulation.
At each modulation, four different values of Dose right index 5, 10, 15, 20 and 30 were applied. Raw data were reconstructed with 4 iDose4 levels (0, 2, 4 and 6).
Results: We found that no significant difference in image noise (SD) of bone, lung, liver issue between the two ATCM including 3D-DOM and Z-DOM (p>0.05). However, significant difference in SD measurements was found in soft tissue (p < 0.05). A significant image noise improvement on iDose4 L2 images at DRI 5 and Z-DOM modulation represented by a reduction in SD of 10.1%, 18.5%, 12.8% and 17.5% for bone, soft tissue, lung and liver respectively.
The greatest reduction of image noise was observed when using iDose4 L6 by 20.9%, 39.3%, 40.7 and 72.7% for bone, soft tissue, lung and liver respectively. Z-DOM and 3D-DOM protocols were observed to lead significant reduction in CTDI vol, DLP and effective dose. The reduction in effective radiation exposure was between 15% and 63% according to the value of DRI used. Conclusion: While maintaining a diagnostic level of image quality, combining AEC software with iDose4 levels can effectively reduce the radiation effective dose significantly (up to 60%) in comparison with constant tube current (AEC-off). The results demonstrate also that no significant reduction in radiation dose exposure between using Z-DOM and 3D-DOM modulation.