Impact of image reconstruction algorithms on histogram analysis of iodine concentration for assessing chemotherapy response in pancreatic ductal adenocarcinoma.

PURPOSE: To evaluate the impact of image reconstruction algorithms on histogram analysis of iodine concentration (IC) derived from dual-energy CT (DECT) to assess response to first-line chemotherapy in patients with pancreatic ductal adenocarcinoma (PDAC). METHODS: We retrospectively analyzed 41 patients with PDAC who underwent pancreatic protocol DECT during first-line chemotherapy between January 2021 and January 2024. Iodine-based material decomposition images at the pancreatic phase were reconstructed using hybrid-iterative reconstruction (Hybrid-IR) and deep-learning image reconstruction at medium- and high-intensity levels (DLIR-M and DLIR-H). A region of interest was placed on PDAC, and histogram parameters of tumor IC were extracted from all three reconstructed image sets. These parameters were compared between the response (complete response [CR], partial response [PR], and stable disease [SD]) and non-response (progressive disease [PD]) groups. Receiver-operating-characteristic (ROC) curve analysis was conducted to evaluate the diagnostic performance of significant histogram parameters for differentiating the response and non-response groups. RESULTS: The response and non-response groups were found to differ significantly in standard deviation, energy, and entropy of the Hybrid-IR (P < .001 for all); standard deviation (P = .002), energy (P < .001), and entropy (P < .001) of the DLIR-M; and standard deviation (P = .003), energy (P < .001), entropy (P < .001), and kurtosis (P = .01) of the DLIR-H. Among these 10 parameters, the entropy of the Hybrid-IR (area under the ROC curve, 0.94) and DLIR-M (0.91) demonstrated high and comparable diagnostic performance for differentiating the two groups, with no statistical difference (P = .20), while both outperformed DLIR-H (0.85) (P = .02-.04). CONCLUSION: The entropy of IC reconstructed with either Hybrid-IR or DLIR-M may serve as an imaging biomarker for assessing chemotherapy response in patients with PDAC. In contrast, DLIR-H may reduce diagnostically relevant texture information and should be used with caution for histogram-based tumor assessment.