Development of hepatopancreatic arterial-dominant phase (HPAP) images using partial downslope injection technique and application to evaluation of pancreatic ductal adenocarcinoma.

BACKGROUND: There is frequently ambiguity regarding the optimal utilization of the liver protocol or the pancreas protocol, and the selection between HAP and PPP is often the subject of controversy. The purpose of this study is to evaluate the validity and efficacy of newly developed hepatopancreatic arterial-dominant phase (HPAP) imaging, which synchronizes HAP and PPP using the partial downslope injection technique (pDiT), compared with conventional HAP and PPP in detecting pancreatic ductal adenocarcinoma.

MATERIALS AND METHODS: This retrospective study included 130 examinations with pancreatic ductal adenocarcinoma who underwent pancreatic CT using either pDiT or a standard injection technique between November 2023 and June 2025. The injection duration was 30-second. The pDiT used 360 mgI/kg at 80 kVp, consisting of a 10-second constant injection followed by a 20-second downslope injection with a slope index (end injection rate / initial injection rate) of 0.3. The standard injection technique used 600 mgI/kg at 120 kVp with a constant rate. Pancreas-to-lesion contrast (PLC), contrast-to-noise ratio (CNR), lesion conspicuity, and sensitivity were compared among HAP, PPP, and HPAP.

RESULTS: Mean PLC and CNR were significantly higher with HPAP than with HAP (p = .03 and p = .04, respectively) and comparable to PPP (p = .79 and p = .94, respectively). Lesion conspicuity showed no significant difference among the three (p = .30). Lesion sensitivity with HPAP was significantly higher than with HAP (p = .03) and not significantly different between HPAP and PPP (p = .56).

CONCLUSION: HPAP generated using the pDiT provides optimal arterial-phase imaging for pancreatic CT.