Room: AAPM ePoster Library
Purpose: CT images reconstructed at high iterative reconstruction (IR) strength show “plastic” image texture, which is deemed unacceptable by radiologists and limits the dose-reducing potential of IR technology. This study is to optimize the use of high IR strength in abdominal CT by understanding its interdependent relationship with radiation exposure using a live animal model.
Methods: The upper abdomen of a 4-year-old sheep was scanned under anesthesia on a Siemens Force CT scanner using 100 ml of intravenous iodinated contrast at different exposures (120kV, effective mAs ranging from 30 to 300mAs). Images were reconstructed using both Filtered Back Projection (FBP) and Advanced Modeled Iterative Reconstruction (ADMIRE) at each exposure with various strengths (levels 1-5). The enhanced abdominal CT images at different combinations of exposure and ADMIRE strength were rated by two radiologists for image texture using the FBP image at highest radiation dose as the reference image. Subjective assessment of additional parameters such as liver, spleen, muscle and subcutaneous fat were performed. Signal-to-noise (SNR) and contrast-to-noise (CNR) were measured across all technique combinations.
Results: Image texture acquires excessive smoothness with the use of higher ADMIRE strength but can be mitigated with lower radiation doses. Radiologists observed diagnostic quality of comparable image textures to FBP at 300mAs for the following exposure-strength combinations with Br40 kernel: 240mAs with level 1, 180mAs with level 2, 150mAs with level 3, 120mAs with level 4, and 60mAs with level 5. Therefore, contrast enhanced Abdominal CT images acquired with 60mAs and reconstructed with IR strength 5 were found to match those acquired at 300mAs and reconstructed with FBP, yielding approximately 80% radiation dose reduction.
Conclusion: The use of high IR strength with appropriate low radiation exposure can yield similar diagnostic quality with comparable image texture in abdominal CT.