SU‐C‐134‐02: Radiation Dose Reduction for CT Lung Cancer Screening Using Advanced Image Reconstruction Techniques

Purpose: To reduce radiation dose to patients undergoing computed tomography (CT) for lung cancer screening while maintaining overall diagnostic image quality and definition of ground‐glass opacities (GGOs). Methods: A Catphan phantom, a Kyoto Kagaku lung screening phantom, and a Kyoto Kagaku multipurpose chest phantom were scanned on a GE Discovery CT750 HD scanner to quantitatively assess the performance of two image reconstruction algorithms (adaptive statistical iterative reconstruction [ASIR] and model‐based iterative reconstruction [MBIR]) used in conjunction with reduced tube currents relative to a standard clinical lung cancer screening protocol (51 mAs and filtered back projection [FBP] reconstruction; CTDIvol = 3.9 mGy). To further assess the algorithms performances, qualitative image analysis was conducted (in the form of a reader study) using the multipurpose chest phantom, which was implanted with eight GGOs of two densities. Results: Our quantitative image analysis indicated that tube current, and thus radiation dose, could be reduced by at least 60% from MBIR while maintaining similar noise and spatial resolution (as determined from the CT images) compared with conventional FBP. The reader study indicated that dose could be reduced by 40% (to 30 mAs or 2.3 mGy) or 60% (to 20 mAs or 1.5 mGy) from using ASIR or MBIR, respectively, while maintaining GGO definition. Additionally, the readers ratings for overall image quality were equal or better (for a given dose) when using ASIR or MBIR compared with FBP. Conclusion: Combining ASIR or MBIR with reduced tube current may allow for lower doses while maintaining overall diagnostic image quality, as well as GGO definition during CT lung cancer screening. Dr. Adam Chandler is an employee of GE Healthcare. Dr. Tinsu Pan is the owner of Texas Medical Imaging Consultants.