Discussion
kidney diseases, contrast-induced AKI, CM, HCC, AKI, contrast-associated or contrast-induced AKI, renal dysfunction
HYPERSENSITIVITY REACTIONS, KIDNEY DISEASES, KIDNEY, EXTRAVASATION, IMPAIRED RENAL FUNCTION
Our study demonstrated that the diminished image contrast resulting from a reduction in iodinated CM could be restored through 50-keV reconstruction or DL-based iodine-boosting techniques. These alternative image reconstruction methods were particularly effective in participants with impaired renal function. Images from the RPP group with 50-keV reconstruction or the DL-based iodine-boosting techniques exhibited higher image contrast scores in both arterial and portal venous phases compared to the standard group, despite a 43% reduction in CM dose. Furthermore, both the 50-keV and DL-based iodine-boosting techniques in the RPP group provided superior overall image quality compared to the standard group for both phases. These findings suggest that the RPP protocol can potentially improve image quality through advanced reconstruction techniques, such as 50-keV imaging and DL-iodine-boosting, even with a smaller CM dose. This is particularly important for patients with kidney diseases or other conditions for which the administration of CM is a concern. Ensuring patient safety is especially crucial for these individuals, as they often require repeated scans as part of their oncological care. Considering that our study population consisted of patients at risk of developing HCC who had impaired renal function, minimizing the contrast dose administered during CT examinations is crucial. We firmly believe that our results support the effectiveness of our RPP protocol, which combines a reduced CM dose and less conventional image reconstruction techniques, for enhancing patient safety while still maintaining adequate image quality for diagnostic purposes.In our study, we compared the image quality of the standard group with hybrid iterative reconstruction and the RPP group with DL-based iodine-boosting reconstruction, as well as low monoenergetic images (50 keV). Notably, the subjective image quality was significantly better in the DL-based iodine-boosting reconstruction images, despite the reduction in CM dose, which is consistent with a recent study [Recent technical developments have demonstrated another approach to enhance the contrast resolution in CECT. In these studies, low monoenergetic images (< 70 keV) could boost iodine contrast and provide higher SNR and CNR [Although image quality improved, we did not observe a significant difference in lesion conspicuity and lesion detection rates between the standard CT images and 50-keV or DL-based iodine-boosting reconstruction images in the RPP group. Both 50-keV and DL-based iodine-boosting reconstruction in the RPP group tended to display higher lesion conspicuity than the standard group in both arterial and portal venous phases, but this finding was not statistically significant. This may have been due to the relatively small number of FLLs in each group and the associated low statistical power. Since we could not predict the occurrence of HCC before CT examination, the discrepancy of the FLL size and number between the groups caused a challenge of simple comparison for diagnostic performance. Despite the statistical insignificance, we cautiously suggest that the tendency for similar to higher lesion conspicuity in the RPP group on size-stratified comparison implies that diagnostic performance might not be compromised by the use of a reduced CM dose.Notably, in the intra-individual comparison between 50-keV and DL-based iodine-boosting reconstructed images, the DL-based iodine-boosting reconstructed images exhibited higher SNR and CNR in both the arterial and portal venous phases than the 50-keV images. However, the 50-keV images demonstrated better subjective image quality and higher lesion conspicuity than the DL-based iodine-boosting images. This may have been due to the alteration of image texture in DL-based iodine-boosting images. As discussed above, DL-based iodine-boosting was performed in two steps, and the initial denoising step may introduce additional texture alteration compared to low monoenergetic images. Further studies are needed to determine the effects of reduced CM and reconstruction methods on FLL detection.Recently developed techniques, such as dual-energy CT and DL-based image reconstruction, have been directed towards improving not only the performance of CECT, but also examination-related safety. Our study results, which demonstrate restored image contrast and quality, suggest that a low CM dose protocol could be prioritized for patients at risk of developing AKI. The necessity of this low CM dose protocol may be debatable due to a recent paradigm shift regarding contrast-induced AKI. Recent studies have shown that the risk of CM for inducing AKI has been overstated by comorbidities and high-osmolar CM, which is no longer used. As a result, recent guidelines have relaxed the criteria for instances requiring prophylaxis for AKI. Even the American College of Radiology-National Kidney Foundation has stated that a reduced CM dose is not specifically required for those at risk of AKI due to concerns about suboptimal image quality, and a single diagnostic dose should be administered [In addition to reducing the risk of contrast-associated or contrast-induced AKI, lowering the CM dose can potentially decrease the risk of extravasation and hypersensitivity reactions, which have been reported to be CM dose-related [Our study had several limitations. First, the small number of participants could affect the statistical power. Although the sample size was calculated for the primary endpoint, the low incidence of non-cystic FLLs might have weakened the statistical significance of comparisons between the standard and RPP groups in terms of lesion conspicuity and lesion detection. Furthermore, we had an imbalance of FLL size and number between the two groups. It is inevitable since we could not predict which patients would have HCC at the time of enrollment. Second, most participants had moderate renal dysfunction, as patients with significantly decreased eGFR (< 30 mL/min/1.73 m