Differential diagnosis of solid pancreatic lesions (SPLs) using B-mode endoscopic ultrasonography (EUS) is challenging. Detective flow imaging (DFI) offers the potential for detecting low-flow vessels in the pancreas, thus enhancing diagnostic accuracy. This study aimed to investigate DFI-EUS findings of SPLs and analyze their differential diagnostic accuracy for pancreatic cancer. This retrospective study included patients with pathologically confirmed SPLs who underwent EUS between April 2021 and June 2023. Expert endosonographers, blinded to the patients’ clinical data, evaluated images obtained through B-mode, eFLOW, and DFI-EUS. Frame rate and vessel detection sensitivity between eFLOW and DFI were compared, and diagnostic criteria for pancreatic cancer were established. This study included 104 patients, most diagnosed with pancreatic cancer. DFI-EUS demonstrated a significantly higher vessel visualization rate (96%) in SPLs compared to eFLOW (27%). Additionally, DFI showed a superior frame rate, sensitivity (99%), and accuracy (88%) in detecting pancreatic cancer, although with a modest specificity (43%). On DFI-EUS, characteristics such as hypovascular, peritumoral, or spotty vessel findings were suggestive of pancreatic cancer. DFI-EUS significantly improved the visualization of vascular structures within the SPLs, highlighting its efficacy as a diagnostic modality for pancreatic cancer.

For a single exposure in radiography, a dual-layer flat-panel detector (DFD) can provide spectral images based on copper filtering or beam hardening, and efficiently utilize the transmitted x-ray photons to improve the detective quantum efficiency (DQE) performance. In this paper, we present a registration method for x-ray images acquired from DFD considering only spatial translations and scale factors. Note that the spatial translation difference between the upper and lower detector layers arises when attaching the layers, and the scale difference arises from the x-ray projection relative to the source and detector distances. The conventional registration methods have inconsistent estimate accuracies depending on the captured object scene even when using entire pixels, and have deteriorated frequency performance due to the interpolation method employed. The proposed method consists of two steps; the first step is conducting a spatial translation according to the Fourier shift theorem with a subpixel registration, and the second step is conducting a scale transformation using cubic interpolation to process the x-ray projections. To estimate the subpixel spatial translation, a maximum-amplitude method using a small portion of the slant-edge phantom is used. The performance of the proposed two-step method is first theoretically analyzed, and then observed by conducting extensive experiments and measuring the noise power spectrum and DQE. An example for registering chest images is also shown. For DFD, it is shown that the proposed method shows a better registration result than the conventional one-step registration.