Ct-less direct correction of attenuation and scatter in the image space using deep learning for whole-body fdg pet: Potential benefits and pitfalls

Purpose: To demonstrate the feasibility of CT-less attenuation and scatter correction (ASC) in the image space using deep learning for whole-body PET, with a focus on the potential benefits and pitfalls. Materials and Methods: In this retrospective study, 110 whole-body fluorodeoxyglucose (FDG) PET/CT studies acquired in 107 patients (mean age ± standard deviation, 58 years ± 18; age range, 11–92 years; 72 females) from February 2016 through January 2018 were randomly collected. A total of 37.3% (41 of 110) of the studies showed metastases, with diverse FDG PET findings throughout the whole body. A U-Net–based network was developed for directly transforming noncorrected PET (PET_NC ) into attenuation-and scatter-corrected PET (PET_ASC ). Deep learning–corrected PET (PET_DL ) images were quantitatively evaluated by using the standardized uptake value (SUV) of the normalized root mean square error, the peak signal-to-noise ratio, and the structural similarity index, in addition to a joint histogram for statistical analysis. Qualitative reviews by radiologists revealed the potential benefits and pitfalls of this correction method. Results: The normalized root mean square error (0.21 ± 0.05 [mean SUV ± standard deviation]), mean peak signal-to-noise ratio (36.3 ± 3.0), mean structural similarity index (0.98 ± 0.01), and voxelwise correlation (97.62%) of PET_DL demonstrated quantitatively high similarity with PET_ASC . Radiologist reviews revealed the overall quality of PET_DL . The potential benefits of PET_DL include a radiation dose reduction on follow-up scans and artifact removal in the regions with attenuation correction– and scatter correction–based artifacts. The pitfalls involve potential false-negative results due to blurring or missing lesions or false-positive results due to pseudo–low-uptake patterns. Conclusion: Deep learning–based direct ASC at whole-body PET is feasible and potentially can be used to overcome the current limitations of CT-based approaches, benefiting patients who are sensitive to radiation from CT.