Independent assessment of duct-focused digital subtraction pancreatography for pancreatic duct visualization: a retrospective pilot study

Independent assessment of duct-focused digital subtraction pancreatography for pancreatic duct visualization: a retrospective pilot study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Independent assessment of duct-focused digital subtraction pancreatography for pancreatic duct visualization: a retrospective pilot study Akihiro Maruyama, Ryota Tagawa, Sakurako Isobe, Junya Yamada, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9250142/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 29 Apr, 2026 Read the published version in BMC Gastroenterology → Version 1 posted 10 You are reading this latest preprint version Abstract Background Digital subtraction pancreatography (DSP) has been proposed as a technique to reduce background interference and facilitate pancreatic duct visualization during endoscopic procedures. However, objective evaluation of DSP image interpretability and its clinical applicability remains limited. Methods This single-center retrospective cohort study included 21 pancreatic ductography procedures performed between September 2022 and October 2025, comprising 11 DSP cases and 10 conventional pancreatography cases. Two independent endoscopists evaluated DSP images using predefined criteria for main pancreatic duct (MPD) visualization, background suppression, and branch duct visualization on a 3-point scale. Interobserver agreement was assessed. Secondary outcomes included technical feasibility, radiation exposure, and procedure-related adverse events. Results DSP was technically feasible in all cases (11/11, 100%), with successful acquisition of subtracted images using a single acquisition per procedure. Independent evaluation demonstrated that MPD visualization was acceptable in 91% and 100% of cases for the two reviewers, respectively. Background suppression was rated as acceptable in 82% and 100% of cases, while branch duct visualization showed greater variability (82% acceptable for both reviewers). Interobserver agreement was 91% for MPD visualization, 82% for background suppression, and 64% for branch duct visualization. Median total radiation dose did not differ significantly between DSP and conventional groups (31.0 vs. 48.3 mGy, p = 0.65). No procedure-related adverse events were observed. Conclusions DSP provided generally interpretable pancreatic duct visualization with background suppression and was feasible without increasing radiation exposure. Although no clear advantage over conventional pancreatography was demonstrated, DSP may serve as a supplementary imaging technique in selected cases where background interference limits duct visualization. Further studies are warranted to define its clinical indications. Digital subtraction pancreatography Endoscopic retrograde cholangiopancreatography Pancreatic duct intervention Figures Figure 1 Figure 2 Introduction Endoscopic retrograde cholangiopancreatography (ERCP) has evolved into a predominantly therapeutic procedure, as purely diagnostic ERCP carries a non-negligible risk of complications, including post-ERCP pancreatitis (PEP).[1] When cross-sectional imaging reveals equivocal main pancreatic duct (MPD) abnormalities, pancreatography via ERCP can provide high spatial resolution and enable simultaneous therapeutic maneuvers such as stenting. However, conventional fluoroscopic pancreatography is often limited by overlapping structures, including the spine, ribs, and bowel gas, which may obscure subtle ductal changes. In addition, high-pressure contrast injection leading to complete pancreatic duct opacification can increase intraductal pressure and potentially contribute to PEP. Consequently, purely diagnostic ERCP has largely been supplanted by less invasive imaging modalities. Magnetic resonance cholangiopancreatography (MRCP) has emerged as a noninvasive alternative for pancreatic duct imaging. Using heavily T2-weighted sequences, MRCP visualizes static or slow-moving fluid within the pancreatic and biliary ducts without the need for contrast injection.[2] Although MRCP demonstrates diagnostic performance comparable to that of diagnostic ERCP for certain indications,[3] its spatial resolution remains inferior to direct pancreatography, and subtle side-branch abnormalities or mild ductal irregularities may be missed in selected cases. These limitations suggest that ERCP-based pancreatography may still have a role in carefully selected patients, provided that ductal visualization can be optimized while maintaining procedural safety. Digital subtraction imaging (DSI) is a radiologic technique widely used in angiography to enhance visualization of contrast-filled structures by subtracting a pre-contrast “mask” image from subsequent contrast-enhanced images, thereby eliminating background interference.[4] With the advent of modern flat-panel fluoroscopy systems, digital subtraction techniques have recently been reintroduced into the hepatopancreatobiliary field, including applications using carbon dioxide and iodinated contrast in the biliary and pancreatic ducts.[5] Digital subtraction methods were first applied to ERCP pancreatography in the 1980s. Lavelle et al. and Yamashita et al. demonstrated that digital subtraction endoscopic retrograde pancreatography could enhance pancreatic parenchymal visualization.[6,7] However, these earlier approaches focused primarily on pancreatic parenchymography and required relatively high-pressure contrast injection, raising concerns regarding pancreatitis risk. More recently, a duct-focused concept of digital subtraction pancreatography (DSP) using modern flat-panel fluoroscopy systems has been proposed. In a prior case report, DSP performed with intentional cessation of contrast injection before parenchymal opacification improved visualization of the MPD and secondary branches without procedure-related complications.[8] Nevertheless, available evidence remains limited to isolated reports and small case series, and concerns persist regarding the potential increase in radiation exposure when subtraction imaging is incorporated into routine ERCP procedures. Despite these observations, objective evaluation of the interpretability of DSP images has not been adequately performed, and the extent to which DSP contributes to practical duct visualization remains unclear. In particular, independent image assessment and interobserver agreement—key elements for evaluating the reliability of a novel imaging technique—have not been systematically investigated. Therefore, the present study was designed to evaluate the interpretability of duct-focused DSP using independent assessment by experienced endoscopists, based on predefined criteria focusing on key aspects of pancreatic duct visualization. As secondary objectives, we assessed the technical feasibility, radiation profile, and procedural safety of DSP, and performed an exploratory comparison of radiation exposure with conventional pancreatic ductography in a single-center retrospective cohort. Methods 1. Study Design and Patients This was a single-center retrospective cohort study conducted at Yokkaichi Municipal Hospital. We reviewed all consecutive patients who underwent duct-focused digital subtraction pancreatography (DSP) during pancreatic duct interventions between September 2022 and October 2025. Clinical data, fluoroscopy time, and radiation dose parameters were extracted from electronic medical records and fluoroscopy dose reports. Nine patients underwent DSP for the evaluation of suspected early pancreatic cancer based on main pancreatic duct (MPD) abnormalities on cross-sectional imaging. The remaining two patients underwent DSP during therapeutic pancreatic duct interventions: one during transpapillary ERCP for postoperative pancreatic duct leakage and one during endoscopic ultrasound–guided pancreatic duct drainage (EUS-PD) for obstructive pancreatitis. No patient was excluded, and all consecutive cases in which DSP was performed during the study period were included in this analysis. This study was conducted in accordance with the Declaration of Helsinki and was approved by the institutional review board of Yokkaichi Municipal Hospital. Given the retrospective nature of the study, the requirement for written informed consent was waived, and an opt-out approach was implemented through public disclosure in accordance with institutional policy. 2. Digital Subtraction Pancreatography All pancreatography procedures were performed using a flat-panel fluoroscopy system (Ultimax-i DREX-U180; Canon, Tokyo, Japan). Patients were examined in the prone position under conscious sedation with intravenous midazolam and pethidine. Selective cannulation of the pancreatic duct was achieved primarily via standard transpapillary ERCP using either a Tandem XL ERCP cannula (Boston Scientific, Marlborough, MA, USA) or an MTW ERCP catheter (MTW Endoskopie, Wesel Büderich, Germany), according to operator preference. Alternative access routes were used when clinically indicated. In the DSP group, iodinated contrast medium (amidotrizoic acid; diatrizoate) was injected slowly into the pancreatic duct under fluoroscopic guidance. Contrast injection was intentionally stopped before pancreatic parenchymal opacification to avoid acinar filling and excessive intraductal pressure. A single DSP run was performed in each case, consisting of 20 images acquired over 10 seconds. A mask image was obtained prior to contrast injection, and subtracted images were generated by subtracting the mask from contrast-enhanced frames to eliminate background structures. In the conventional group, standard fluoroscopic pancreatography was performed without digital subtraction imaging using routine contrast injection. Routine prophylactic administration of rectal nonsteroidal anti-inflammatory drugs for PEP prevention was not implemented during the study period in accordance with institutional practice. 3. Outcome Measures The primary outcome of this study was the interpretability of duct-focused DSP images, assessed by independent review. Two experienced endoscopists, who were not involved in the procedures, independently evaluated DSP images using predefined criteria focusing on key aspects of pancreatic duct visualization. The following three domains were assessed: Visualization of the main pancreatic duct (MPD); Degree of background suppression; Visualization of branch ducts. Each domain was scored using a 3-point ordinal scale: 1 = insufficient for interpretation; 2 = acceptable for clinical interpretation; 3 = clearly interpretable. Interobserver agreement was assessed for each domain. Secondary outcomes included: Technical feasibility of DSP, defined as successful acquisition of subtracted images allowing anatomical assessment of the MPD; Total radiation dose per procedure (air-kerma, mGy); Radiation dose attributable to DSP in the DSP group (mGy); The proportion of DSP-related dose relative to total radiation exposure (%); Procedure-related adverse events, including post-ERCP pancreatitis, bleeding, perforation, and infection. For exploratory analysis, total radiation dose was compared between the DSP and conventional pancreatography groups. 4. Statistical Analysis Continuous variables are presented as median and interquartile range (IQR) when appropriate. Categorical variables are expressed as counts and percentages. Given the small sample size and non-normal distribution of radiation dose values, comparisons between the DSP and conventional groups were performed using the Mann–Whitney U test for continuous variables. A two-sided p value < 0.05 was considered statistically significant. Interobserver agreement was assessed using percentage agreement. (Cohen’s kappa coefficient was not calculated due to the limited variability in scoring.) Statistical analyses were performed using Microsoft Excel 365 (Microsoft Corp., Redmond, WA, USA). Results 1. Patient Characteristics (Table 1) A total of 21 pancreatic ductography procedures performed between September 2022 and October 2025 were included in this analysis, comprising 11 procedures in the DSP group and 10 in the conventional group. The median age was 72.0 years in the DSP group and 76.5 years in the conventional group. Female patients accounted for 45% (5/11) in the DSP group and 20% (2/10) in the conventional group. The primary indication for pancreatic ductography was evaluation of suspected pancreatic neoplasia in 9 of 11 procedures (82%) in the DSP group and 7 of 10 procedures (70%) in the conventional group. Pancreatic duct stent placement was performed in 2 procedures (18%) in the DSP group and 3 procedures (30%) in the conventional group (Table 1). 2. Independent Image Assessment Independent image evaluation demonstrated that DSP images were generally interpretable across all assessed domains. For MPD visualization, Reviewer 1 rated 10 of 11 cases (91%) as acceptable and 1 case (9%) as insufficient, whereas Reviewer 2 rated all cases (11/11, 100%) as acceptable. No cases were rated as clearly interpretable (score 3) by either reviewer. Background suppression was rated as acceptable in 9 of 11 cases (82%) by Reviewer 1 and in all cases (11/11, 100%) by Reviewer 2. Visualization of branch ducts showed greater variability, with both reviewers rating 9 of 11 cases (82%) as acceptable and 2 cases (18%) as insufficient. Interobserver agreement was 91% for MPD visualization, 82% for background suppression, and 64% for branch duct visualization. 3. DSP Performance and Technical Success DSP was successfully performed in all 11 patients. Technical feasibility—defined as acquisition of subtracted images permitting anatomical assessment of the MPD—was achieved in all cases (11/11, 100%). In each patient, a single DSP acquisition (20 images over 10 seconds) was sufficient, and no additional subtraction runs were required. Representative cases are shown in Figures 1 and 2. In selected cases, subtraction imaging reduced background interference from overlapping structures and allowed visualization of ductal morphology that was difficult to appreciate on conventional fluoroscopy. 4. Radiation Exposure and Adverse Events The median total radiation dose was 31.0 mGy (IQR, 13.7–61.2) in the DSP group and 48.3 mGy (IQR, 30.7–56.1) in the conventional group. There was no statistically significant difference in total radiation dose between the two groups (p = 0.65). In the DSP group, the median DSP-attributable radiation dose was 3.7 mGy, corresponding to a median of 7.3% of the total procedural radiation exposure. No procedure-related adverse events, including post-ERCP pancreatitis, bleeding, perforation, or infection, were observed in either group. Discussion In this single-center retrospective cohort study, independent image evaluation demonstrated that duct-focused digital subtraction pancreatography (DSP) provided generally interpretable visualization of the main pancreatic duct (MPD) with background suppression across most cases. DSP was technically feasible in all patients in whom it was attempted, and subtracted images allowing anatomical assessment of the MPD were successfully obtained in 11 of 11 procedures without the need for additional subtraction runs. When compared with conventional pancreatography performed during the same period, incorporation of DSP was not associated with a statistically significant increase in total radiation exposure. Furthermore, no procedure-related adverse events were observed in either group. Collectively, these findings suggest that DSP can be integrated into routine pancreatic duct interventions as a supplementary imaging technique without compromising procedural safety or substantially increasing radiation burden. A central concern regarding the use of subtraction imaging during ERCP is the potential for increased radiation exposure. Digital subtraction techniques inherently require acquisition of mask images and subsequent contrast-enhanced frames, which may raise concerns about cumulative dose. In the present study, however, total radiation exposure in the DSP group did not differ significantly from that in the conventional group. Although the sample size limits definitive statistical interpretation, the absence of a detectable increase in total dose suggests that carefully implemented DSP does not necessarily translate into additional radiation risk. Importantly, several procedural features likely contributed to this observation. DSP was performed using a single subtraction run per procedure, and image acquisition was limited to a short predefined sequence (20 images over 10 seconds). Contrast injection was intentionally terminated prior to parenchymal opacification, thereby minimizing prolonged fluoroscopic monitoring. These measures align with radiation-conscious ERCP practice. Previous studies have demonstrated that reduction of fluoroscopy frame rate is an effective strategy for decreasing radiation exposure during ERCP,[ 9 ] and reported air-kerma values for ERCP vary widely depending on procedural complexity, with typical ranges between approximately 50 and 150 mGy.[ 10 ] Within this broader clinical context, the radiation exposure observed in the DSP group appears to fall within acceptable limits. Historically, digital subtraction techniques were introduced into pancreatography in the 1980s. Lavelle et al. and Yamashita et al. demonstrated that subtraction imaging could enhance visualization of pancreatic structures, particularly the pancreatic parenchyma.[ 6 , 7 ] However, these early applications emphasized parenchymography and often required relatively high-pressure contrast injection, which raised concerns regarding post-ERCP pancreatitis (PEP).[ 1 ] The current approach differs conceptually from those earlier reports. Rather than aiming for parenchymal enhancement, the present study focused on duct-level subtraction imaging using modern flat-panel fluoroscopy systems. By deliberately avoiding complete acinar filling and limiting contrast volume, DSP was applied as a duct-focused adjunct. A more recent report utilizing contemporary imaging systems suggested that such duct-focused subtraction imaging may improve delineation of ductal morphology without evident complications.[ 8 ] The present study extends these observations by providing not only feasibility data but also objective information regarding image interpretability and comparative radiation exposure, thereby offering a more comprehensive assessment of procedural integration in routine practice. From a broader clinical perspective, ERCP has evolved into a predominantly therapeutic modality, as purely diagnostic ERCP carries a non-negligible risk of complications.1 Noninvasive imaging techniques such as magnetic resonance cholangiopancreatography (MRCP) provide valuable ductal assessment without the need for contrast injection.[ 2 , 3 ] Nevertheless, certain clinical scenarios still require high-resolution intraprocedural evaluation of the pancreatic duct. Subtle MPD irregularities, short-segment strictures, or detailed branch morphology may be difficult to appreciate on cross-sectional imaging alone. During therapeutic procedures such as stent placement, accurate delineation of upstream ductal anatomy can also facilitate procedural precision. In such selected situations, background interference from vertebral structures, ribs, or bowel gas may limit interpretation of conventional fluoroscopy. By subtracting non-contrast background structures, DSP may provide incremental visualization that assists anatomical understanding. It is important to emphasize, however, that DSP did not demonstrate a clear advantage over conventional pancreatography in terms of overall image quality in the present study. Accordingly, DSP should not be interpreted as a replacement for conventional imaging or cross-sectional modalities, but rather as a potential adjunct in selected cases where improved separation from background structures may be beneficial. Technical limitations must also be acknowledged. Motion-related misregistration is a recognized challenge in temporal subtraction imaging. [ 11 , 12 ] Respiratory movement during ERCP may degrade alignment between mask and contrast-enhanced images, potentially reducing subtraction quality. Although DSP images were generally interpretable in this series, variability in branch duct visualization and interobserver agreement suggests that image quality may be influenced by case-specific factors. In the radiologic literature, various motion-correction and image registration techniques have been proposed to mitigate such artifacts, including non-rigid registration and respiratory phase–matching algorithms.[ 13 – 15 ] While implementation of such advanced techniques was beyond the scope of the present study, ongoing refinement of motion compensation strategies may further enhance the reliability of ductal subtraction imaging in endoscopic practice. The comparative nature of this study warrants careful interpretation. Although total radiation exposure did not significantly differ between groups, the small sample size limits statistical power, and the absence of a significant difference should not be equated with definitive equivalence. Moreover, DSP was performed at the discretion of the endoscopist, introducing potential selection bias. It is possible that DSP was preferentially applied in cases in which enhanced visualization was anticipated to be useful, potentially reflecting greater procedural complexity. Conversely, in some instances, operators may have limited fluoroscopic duration because subtraction imaging provided sufficient anatomical information. These factors cannot be fully disentangled in a retrospective design. Therefore, while the present findings suggest that DSP does not markedly increase radiation exposure, larger prospective studies with predefined inclusion criteria and standardized imaging protocols are required to confirm these observations. Additional limitations should be considered. This was a single-center study with a limited number of patients, restricting generalizability. Diagnostic performance, impact on clinical decision-making, and long-term outcomes were not assessed. Interobserver agreement was evaluated; however, the limited variability in scoring and small sample size constrain definitive conclusions regarding reproducibility. Future investigations incorporating larger cohorts, refined scoring systems, and multicenter enrollment would provide a more robust evaluation of the clinical role of DSP. Conclusions Duct-focused digital subtraction pancreatography was technically feasible and provided generally interpretable pancreatic duct visualization without a measurable increase in total radiation exposure compared with conventional pancreatography in this small retrospective cohort. Although a clear advantage over conventional imaging was not demonstrated, DSP may serve as a supplementary imaging technique in selected pancreatic duct interventions where background interference limits visualization. Further prospective and adequately powered studies are warranted to clarify its clinical role and optimal indications. Declarations Ethics approval and consent to participate This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Yokkaichi Municipal Hospital, Japan (Approval No. 2024-39). The requirement for written informed consent was waived due to the retrospective observational nature of the study. An opt-out approach was implemented through public disclosure in accordance with institutional policy. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Authors’ contributions AM: conceptualization, methodology, investigation, formal analysis, visualization, writing—original draft. RT, SI, JY, HK, KT: data curation, investigation. MK: supervision, validation, writing—review and editing. All authors read and approved the final manuscript. Acknowledgements Not applicable. References Freeman ML, DiSario JA, Nelson DB, et al. Risk factors for post-ERCP pancreatitis: a prospective multicenter study. Gastrointest Endosc. 2001;54(4):425–34. Griffin N, Charles-Edwards G, Grant LA. Magnetic resonance cholangiopancreatography: the ABC of MRCP. Insights Imaging. 2012;3(1):11–21. Kaltenthaler EC, Walters SJ, Chilcott J, et al. MRCP compared to diagnostic ERCP for biliary obstruction: a systematic review. BMC Med Imaging. 2006;6:9. Modic MT, Weinstein MA, Chilcote WA, et al. Digital subtraction angiography of the intracranial vascular system: comparative study in 55 patients. AJNR Am J Neuroradiol. 1981;2(6):527–34. Maruyama A, Kobayashi M, Takeshima H, et al. Digital subtraction imaging with carbon dioxide and liquid contrast in the biliary and pancreatic ducts. Endoscopy. 2025;57:E388–9. Lavelle MI, Tait NP, Walsh T, et al. Demonstration of pancreatic parenchyma by digital subtraction techniques during ERCP. Clin Radiol. 1985;36(4):405–7. Yamashita Y, Araki Y, Kawamura M, et al. Digital subtraction endoscopic retrograde pancreatography for pancreatic parenchymal imaging: experience in 59 patients. Gastrointest Endosc. 1987;29:198–203. Maruyama A, Kato H, Tominaga S, et al. Digital subtraction pancreatography enhances ductal visualization in high-grade PanIN. Endoscopy. 2025;57:E1184–5. Hasegawa Y, Nakai Y, Oyama H, et al. Reduction of fluoroscopy frame rate decreases radiation exposure during ERCP. Am J Gastroenterol. 2021;116:S115. Takenaka M, Hosono M, Hayashi S, et al. Radiation doses and radiation protection in ERCP procedures. Br J Radiol. 2021;94(1126):20210399. Meijering EH, Niessen WJ, Bakker J, et al. Reduction of patient motion artifacts in DSA: automatic technique vs pixel-shifting. Radiology. 2001;219(1):288–93. Meijering EH, Niessen WJ, Viergever MA. Retrospective motion correction in digital subtraction angiography: a review. IEEE Trans Med Imaging. 1999;18(1):2–21. Liu B, Zhang B, Wan C, Dong Y. Non-rigid registration method for cerebral DSA images to reduce motion artifacts. Biomed Mater Eng. 2014;24(1):1149–55. Ohnishi T, Takano Y, Kato H, et al. Respiratory-synchronized DSA based on respiratory phase matching. Signal Image Video Process. 2018;12(3):539–47. Sekiguchi Y, Okamoto T, Matsuzawa T, et al. PatchDSA: improving DSA with patch-based phase-matching under free breathing. Radiol Phys Technol. 2025;18(4):698–706. Table Table 1 DSP (n=11) Conventional (n=10) Age, median (years) 72 76.5 Female, n (%) 5 (45%) 2 (20%) Indication, n (%) – Pancreatic juice cytology 9 (82%) 7 (70%) – Stent placement 2 (18%) 3 (30%) Total radiation dose (mGy), median (IQR) 31.0 (13.7–61.2) 48.3 (30.7–56.1) Additional Declarations No competing interests reported. Supplementary Files supplementaryvideo.mp4 Supplementary material legend Supplementary Video 1. Duct-focused digital subtraction pancreatography (DSP) during transpapillary pancreatic duct stent placement. The video demonstrates a single DSP acquisition (20 images over 10 seconds) during ERCP. Subtraction imaging eliminates background bony structures and enhances delineation of the main pancreatic duct, facilitating precise stent deployment. Cite Share Download PDF Status: Published Journal Publication published 29 Apr, 2026 Read the published version in BMC Gastroenterology → Version 1 posted Editorial decision: Revision requested 13 Apr, 2026 Reviews received at journal 12 Apr, 2026 Reviews received at journal 12 Apr, 2026 Reviewers agreed at journal 06 Apr, 2026 Reviewers agreed at journal 06 Apr, 2026 Reviewers invited by journal 06 Apr, 2026 Editor invited by journal 01 Apr, 2026 Editor assigned by journal 31 Mar, 2026 Submission checks completed at journal 31 Mar, 2026 First submitted to journal 28 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9250142","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":619699498,"identity":"fb84e09d-4ef4-4aa5-9940-2a2fb787c65d","order_by":0,"name":"Akihiro 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06:23:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9250142/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9250142/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12876-026-04872-9","type":"published","date":"2026-04-29T15:57:19+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":106703207,"identity":"c1538c12-8620-42bf-9056-ec0fba2a3504","added_by":"auto","created_at":"2026-04-12 07:39:44","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":135980,"visible":true,"origin":"","legend":"\u003cp\u003eDigital subtraction pancreatography improves visualization compared with conventional pancreatography.\u003c/p\u003e\n\u003cp\u003e(a) Conventional pancreatography showing limited delineation of the main pancreatic duct due to overlapping vertebral structures.\u003cbr\u003e\n(b) DSP image obtained in the same patient, demonstrating clear visualization of the main pancreatic duct and secondary branches after subtraction of bony and soft-tissue backgrounds.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9250142/v1/ce8cd7024cf6db5ba4873e51.jpeg"},{"id":106703210,"identity":"bc648b8f-dc29-483c-8091-314ba5531760","added_by":"auto","created_at":"2026-04-12 07:39:45","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":128606,"visible":true,"origin":"","legend":"\u003cp\u003eDSP findings in patients requiring therapeutic pancreatic duct interventions.\u003c/p\u003e\n\u003cp\u003e(a) Conventional pancreatography in a patient with postoperative pancreatic fistula (POPF), showing poor visualization of the leak site.\u003cbr\u003e\n(b) DSP in the same case clearly delineates the pancreatic juice leakage by eliminating background structures.\u003cbr\u003e\n(c) DSP image acquired during EUS-guided pancreatic duct drainage (EUS-PD), providing enhanced visualization of the upstream duct and leak site to facilitate guidewire manipulation and stent placement.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9250142/v1/56c7fe31968d33d2d37f34a5.jpeg"},{"id":109203976,"identity":"fc7b9e62-346c-452e-ae42-8262a8f5f488","added_by":"auto","created_at":"2026-05-13 14:51:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":452739,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9250142/v1/22b40bed-eed7-4c58-9a8c-976b51bc51a1.pdf"},{"id":106703202,"identity":"96f5412f-ac5b-4932-8c6e-3bdce35e632a","added_by":"auto","created_at":"2026-04-12 07:39:43","extension":"mp4","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":156263442,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary material legend\u003c/p\u003e\n\u003cp\u003eSupplementary Video 1. Duct-focused digital subtraction pancreatography (DSP) during transpapillary pancreatic duct stent placement.\u003c/p\u003e\n\u003cp\u003eThe video demonstrates a single DSP acquisition (20 images over 10 seconds) during ERCP. Subtraction imaging eliminates background bony structures and enhances delineation of the main pancreatic duct, facilitating precise stent deployment.\u003c/p\u003e","description":"","filename":"supplementaryvideo.mp4","url":"https://assets-eu.researchsquare.com/files/rs-9250142/v1/0bc0ef8eb1437996fa868823.mp4"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eIndependent assessment of duct-focused digital subtraction pancreatography for pancreatic duct visualization: a retrospective pilot study\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eEndoscopic retrograde cholangiopancreatography (ERCP) has evolved into a predominantly therapeutic procedure, as purely diagnostic ERCP carries a non-negligible risk of complications, including post-ERCP pancreatitis (PEP).[1] When cross-sectional imaging reveals equivocal main pancreatic duct (MPD) abnormalities, pancreatography via ERCP can provide high spatial resolution and enable simultaneous therapeutic maneuvers such as stenting. However, conventional fluoroscopic pancreatography is often limited by overlapping structures, including the spine, ribs, and bowel gas, which may obscure subtle ductal changes. In addition, high-pressure contrast injection leading to complete pancreatic duct opacification can increase intraductal pressure and potentially contribute to PEP. Consequently, purely diagnostic ERCP has largely been supplanted by less invasive imaging modalities.\u003c/p\u003e\n\u003cp\u003eMagnetic resonance cholangiopancreatography (MRCP) has emerged as a noninvasive alternative for pancreatic duct imaging. Using heavily T2-weighted sequences, MRCP visualizes static or slow-moving fluid within the pancreatic and biliary ducts without the need for contrast injection.[2] Although MRCP demonstrates diagnostic performance comparable to that of diagnostic ERCP for certain indications,[3] its spatial resolution remains inferior to direct pancreatography, and subtle side-branch abnormalities or mild ductal irregularities may be missed in selected cases. These limitations suggest that ERCP-based pancreatography may still have a role in carefully selected patients, provided that ductal visualization can be optimized while maintaining procedural safety.\u003c/p\u003e\n\u003cp\u003eDigital subtraction imaging (DSI) is a radiologic technique widely used in angiography to enhance visualization of contrast-filled structures by subtracting a pre-contrast “mask” image from subsequent contrast-enhanced images, thereby eliminating background interference.[4] With the advent of modern flat-panel fluoroscopy systems, digital subtraction techniques have recently been reintroduced into the hepatopancreatobiliary field, including applications using carbon dioxide and iodinated contrast in the biliary and pancreatic ducts.[5] Digital subtraction methods were first applied to ERCP pancreatography in the 1980s. Lavelle et al. and Yamashita et al. demonstrated that digital subtraction endoscopic retrograde pancreatography could enhance pancreatic parenchymal visualization.[6,7] However, these earlier approaches focused primarily on pancreatic parenchymography and required relatively high-pressure contrast injection, raising concerns regarding pancreatitis risk.\u003c/p\u003e\n\u003cp\u003eMore recently, a duct-focused concept of digital subtraction pancreatography (DSP) using modern flat-panel fluoroscopy systems has been proposed. In a prior case report, DSP performed with intentional cessation of contrast injection before parenchymal opacification improved visualization of the MPD and secondary branches without procedure-related complications.[8] Nevertheless, available evidence remains limited to isolated reports and small case series, and concerns persist regarding the potential increase in radiation exposure when subtraction imaging is incorporated into routine ERCP procedures.\u003c/p\u003e\n\u003cp\u003eDespite these observations, objective evaluation of the interpretability of DSP images has not been adequately performed, and the extent to which DSP contributes to practical duct visualization remains unclear. In particular, independent image assessment and interobserver agreement—key elements for evaluating the reliability of a novel imaging technique—have not been systematically investigated.\u003c/p\u003e\n\u003cp\u003eTherefore, the present study was designed to evaluate the interpretability of duct-focused DSP using independent assessment by experienced endoscopists, based on predefined criteria focusing on key aspects of pancreatic duct visualization. As secondary objectives, we assessed the technical feasibility, radiation profile, and procedural safety of DSP, and performed an exploratory comparison of radiation exposure with conventional pancreatic ductography in a single-center retrospective cohort.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e1. Study Design and Patients\u003c/p\u003e\n\u003cp\u003eThis was a single-center retrospective cohort study conducted at Yokkaichi Municipal Hospital. We reviewed all consecutive patients who underwent duct-focused digital subtraction pancreatography (DSP) during pancreatic duct interventions between September 2022 and October 2025. Clinical data, fluoroscopy time, and radiation dose parameters were extracted from electronic medical records and fluoroscopy dose reports.\u003c/p\u003e\n\u003cp\u003eNine patients underwent DSP for the evaluation of suspected early pancreatic cancer based on main pancreatic duct (MPD) abnormalities on cross-sectional imaging. The remaining two patients underwent DSP during therapeutic pancreatic duct interventions: one during transpapillary ERCP for postoperative pancreatic duct leakage and one during endoscopic ultrasound–guided pancreatic duct drainage (EUS-PD) for obstructive pancreatitis. No patient was excluded, and all consecutive cases in which DSP was performed during the study period were included in this analysis.\u003c/p\u003e\n\u003cp\u003eThis study was conducted in accordance with the Declaration of Helsinki and was approved by the institutional review board of Yokkaichi Municipal Hospital. Given the retrospective nature of the study, the requirement for written informed consent was waived, and an opt-out approach was implemented through public disclosure in accordance with institutional policy.\u003c/p\u003e\n\u003cp\u003e2. Digital Subtraction Pancreatography\u003c/p\u003e\n\u003cp\u003eAll pancreatography procedures were performed using a flat-panel fluoroscopy system (Ultimax-i DREX-U180; Canon, Tokyo, Japan). Patients were examined in the prone position under conscious sedation with intravenous midazolam and pethidine.\u003c/p\u003e\n\u003cp\u003eSelective cannulation of the pancreatic duct was achieved primarily via standard transpapillary ERCP using either a Tandem XL ERCP cannula (Boston Scientific, Marlborough, MA, USA) or an MTW ERCP catheter (MTW Endoskopie, Wesel Büderich, Germany), according to operator preference. Alternative access routes were used when clinically indicated.\u003c/p\u003e\n\u003cp\u003eIn the DSP group, iodinated contrast medium (amidotrizoic acid; diatrizoate) was injected slowly into the pancreatic duct under fluoroscopic guidance. Contrast injection was intentionally stopped before pancreatic parenchymal opacification to avoid acinar filling and excessive intraductal pressure. A single DSP run was performed in each case, consisting of 20 images acquired over 10 seconds. A mask image was obtained prior to contrast injection, and subtracted images were generated by subtracting the mask from contrast-enhanced frames to eliminate background structures.\u003c/p\u003e\n\u003cp\u003eIn the conventional group, standard fluoroscopic pancreatography was performed without digital subtraction imaging using routine contrast injection.\u003c/p\u003e\n\u003cp\u003eRoutine prophylactic administration of rectal nonsteroidal anti-inflammatory drugs for PEP prevention was not implemented during the study period in accordance with institutional practice.\u003c/p\u003e\n\u003cp\u003e3. Outcome Measures\u003c/p\u003e\n\u003cp\u003eThe primary outcome of this study was the interpretability of duct-focused DSP images, assessed by independent review.\u003c/p\u003e\n\u003cp\u003eTwo experienced endoscopists, who were not involved in the procedures, independently evaluated DSP images using predefined criteria focusing on key aspects of pancreatic duct visualization. The following three domains were assessed:\u003c/p\u003e\n\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003eVisualization of the main pancreatic duct (MPD);\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eDegree of background suppression;\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eVisualization of branch ducts.\u0026nbsp;\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eEach domain was scored using a 3-point ordinal scale:\u003cbr\u003e\u0026nbsp;1 = insufficient for interpretation;\u003cbr\u003e\u0026nbsp;2 = acceptable for clinical interpretation;\u003cbr\u003e\u0026nbsp;3 = clearly interpretable.\u003c/p\u003e\n\u003cp\u003eInterobserver agreement was assessed for each domain.\u003c/p\u003e\n\u003cp\u003eSecondary outcomes included:\u003c/p\u003e\n\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003eTechnical feasibility of DSP, defined as successful acquisition of subtracted images allowing anatomical assessment of the MPD;\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eTotal radiation dose per procedure (air-kerma, mGy);\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eRadiation dose attributable to DSP in the DSP group (mGy);\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eThe proportion of DSP-related dose relative to total radiation exposure (%);\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eProcedure-related adverse events, including post-ERCP pancreatitis, bleeding, perforation, and infection.\u0026nbsp;\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eFor exploratory analysis, total radiation dose was compared between the DSP and conventional pancreatography groups.\u003c/p\u003e\n\u003cp\u003e4. Statistical Analysis\u003c/p\u003e\n\u003cp\u003eContinuous variables are presented as median and interquartile range (IQR) when appropriate. Categorical variables are expressed as counts and percentages.\u003c/p\u003e\n\u003cp\u003eGiven the small sample size and non-normal distribution of radiation dose values, comparisons between the DSP and conventional groups were performed using the Mann–Whitney U test for continuous variables. A two-sided p value \u0026lt; 0.05 was considered statistically significant.\u003c/p\u003e\n\u003cp\u003eInterobserver agreement was assessed using percentage agreement. (Cohen’s kappa coefficient was not calculated due to the limited variability in scoring.)\u003c/p\u003e\n\u003cp\u003eStatistical analyses were performed using Microsoft Excel 365 (Microsoft Corp., Redmond, WA, USA).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e1. Patient Characteristics (Table 1)\u003c/p\u003e\n\u003cp\u003eA total of 21 pancreatic ductography procedures performed between September 2022 and October 2025 were included in this analysis, comprising 11 procedures in the DSP group and 10 in the conventional group.\u003c/p\u003e\n\u003cp\u003eThe median age was 72.0 years in the DSP group and 76.5 years in the conventional group. Female patients accounted for 45% (5/11) in the DSP group and 20% (2/10) in the conventional group. The primary indication for pancreatic ductography was evaluation of suspected pancreatic neoplasia in 9 of 11 procedures (82%) in the DSP group and 7 of 10 procedures (70%) in the conventional group. Pancreatic duct stent placement was performed in 2 procedures (18%) in the DSP group and 3 procedures (30%) in the conventional group (Table 1).\u003c/p\u003e\n\u003cp\u003e2. Independent Image Assessment\u003c/p\u003e\n\u003cp\u003eIndependent image evaluation demonstrated that DSP images were generally interpretable across all assessed domains.\u003c/p\u003e\n\u003cp\u003eFor MPD visualization, Reviewer 1 rated 10 of 11 cases (91%) as acceptable and 1 case (9%) as insufficient, whereas Reviewer 2 rated all cases (11/11, 100%) as acceptable. No cases were rated as clearly interpretable (score 3) by either reviewer.\u003c/p\u003e\n\u003cp\u003eBackground suppression was rated as acceptable in 9 of 11 cases (82%) by Reviewer 1 and in all cases (11/11, 100%) by Reviewer 2.\u003c/p\u003e\n\u003cp\u003eVisualization of branch ducts showed greater variability, with both reviewers rating 9 of 11 cases (82%) as acceptable and 2 cases (18%) as insufficient.\u003c/p\u003e\n\u003cp\u003eInterobserver agreement was 91% for MPD visualization, 82% for background suppression, and 64% for branch duct visualization.\u003c/p\u003e\n\u003cp\u003e3. DSP Performance and Technical Success\u003c/p\u003e\n\u003cp\u003eDSP was successfully performed in all 11 patients. Technical feasibility—defined as acquisition of subtracted images permitting anatomical assessment of the MPD—was achieved in all cases (11/11, 100%). In each patient, a single DSP acquisition (20 images over 10 seconds) was sufficient, and no additional subtraction runs were required.\u003c/p\u003e\n\u003cp\u003eRepresentative cases are shown in Figures 1 and 2. In selected cases, subtraction imaging reduced background interference from overlapping structures and allowed visualization of ductal morphology that was difficult to appreciate on conventional fluoroscopy.\u003c/p\u003e\n\u003cp\u003e4. Radiation Exposure and Adverse Events\u003c/p\u003e\n\u003cp\u003eThe median total radiation dose was 31.0 mGy (IQR, 13.7–61.2) in the DSP group and 48.3 mGy (IQR, 30.7–56.1) in the conventional group. There was no statistically significant difference in total radiation dose between the two groups (p = 0.65).\u003c/p\u003e\n\u003cp\u003eIn the DSP group, the median DSP-attributable radiation dose was 3.7 mGy, corresponding to a median of 7.3% of the total procedural radiation exposure.\u003c/p\u003e\n\u003cp\u003eNo procedure-related adverse events, including post-ERCP pancreatitis, bleeding, perforation, or infection, were observed in either group.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this single-center retrospective cohort study, independent image evaluation demonstrated that duct-focused digital subtraction pancreatography (DSP) provided generally interpretable visualization of the main pancreatic duct (MPD) with background suppression across most cases. DSP was technically feasible in all patients in whom it was attempted, and subtracted images allowing anatomical assessment of the MPD were successfully obtained in 11 of 11 procedures without the need for additional subtraction runs. When compared with conventional pancreatography performed during the same period, incorporation of DSP was not associated with a statistically significant increase in total radiation exposure. Furthermore, no procedure-related adverse events were observed in either group. Collectively, these findings suggest that DSP can be integrated into routine pancreatic duct interventions as a supplementary imaging technique without compromising procedural safety or substantially increasing radiation burden.\u003c/p\u003e \u003cp\u003eA central concern regarding the use of subtraction imaging during ERCP is the potential for increased radiation exposure. Digital subtraction techniques inherently require acquisition of mask images and subsequent contrast-enhanced frames, which may raise concerns about cumulative dose. In the present study, however, total radiation exposure in the DSP group did not differ significantly from that in the conventional group. Although the sample size limits definitive statistical interpretation, the absence of a detectable increase in total dose suggests that carefully implemented DSP does not necessarily translate into additional radiation risk. Importantly, several procedural features likely contributed to this observation. DSP was performed using a single subtraction run per procedure, and image acquisition was limited to a short predefined sequence (20 images over 10 seconds). Contrast injection was intentionally terminated prior to parenchymal opacification, thereby minimizing prolonged fluoroscopic monitoring. These measures align with radiation-conscious ERCP practice. Previous studies have demonstrated that reduction of fluoroscopy frame rate is an effective strategy for decreasing radiation exposure during ERCP,[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] and reported air-kerma values for ERCP vary widely depending on procedural complexity, with typical ranges between approximately 50 and 150 mGy.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] Within this broader clinical context, the radiation exposure observed in the DSP group appears to fall within acceptable limits.\u003c/p\u003e \u003cp\u003eHistorically, digital subtraction techniques were introduced into pancreatography in the 1980s. Lavelle et al. and Yamashita et al. demonstrated that subtraction imaging could enhance visualization of pancreatic structures, particularly the pancreatic parenchyma.[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] However, these early applications emphasized parenchymography and often required relatively high-pressure contrast injection, which raised concerns regarding post-ERCP pancreatitis (PEP).[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] The current approach differs conceptually from those earlier reports. Rather than aiming for parenchymal enhancement, the present study focused on duct-level subtraction imaging using modern flat-panel fluoroscopy systems. By deliberately avoiding complete acinar filling and limiting contrast volume, DSP was applied as a duct-focused adjunct. A more recent report utilizing contemporary imaging systems suggested that such duct-focused subtraction imaging may improve delineation of ductal morphology without evident complications.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] The present study extends these observations by providing not only feasibility data but also objective information regarding image interpretability and comparative radiation exposure, thereby offering a more comprehensive assessment of procedural integration in routine practice.\u003c/p\u003e \u003cp\u003eFrom a broader clinical perspective, ERCP has evolved into a predominantly therapeutic modality, as purely diagnostic ERCP carries a non-negligible risk of complications.1 Noninvasive imaging techniques such as magnetic resonance cholangiopancreatography (MRCP) provide valuable ductal assessment without the need for contrast injection.[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] Nevertheless, certain clinical scenarios still require high-resolution intraprocedural evaluation of the pancreatic duct. Subtle MPD irregularities, short-segment strictures, or detailed branch morphology may be difficult to appreciate on cross-sectional imaging alone. During therapeutic procedures such as stent placement, accurate delineation of upstream ductal anatomy can also facilitate procedural precision. In such selected situations, background interference from vertebral structures, ribs, or bowel gas may limit interpretation of conventional fluoroscopy. By subtracting non-contrast background structures, DSP may provide incremental visualization that assists anatomical understanding. It is important to emphasize, however, that DSP did not demonstrate a clear advantage over conventional pancreatography in terms of overall image quality in the present study. Accordingly, DSP should not be interpreted as a replacement for conventional imaging or cross-sectional modalities, but rather as a potential adjunct in selected cases where improved separation from background structures may be beneficial.\u003c/p\u003e \u003cp\u003eTechnical limitations must also be acknowledged. Motion-related misregistration is a recognized challenge in temporal subtraction imaging. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] Respiratory movement during ERCP may degrade alignment between mask and contrast-enhanced images, potentially reducing subtraction quality. Although DSP images were generally interpretable in this series, variability in branch duct visualization and interobserver agreement suggests that image quality may be influenced by case-specific factors. In the radiologic literature, various motion-correction and image registration techniques have been proposed to mitigate such artifacts, including non-rigid registration and respiratory phase\u0026ndash;matching algorithms.[\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] While implementation of such advanced techniques was beyond the scope of the present study, ongoing refinement of motion compensation strategies may further enhance the reliability of ductal subtraction imaging in endoscopic practice.\u003c/p\u003e \u003cp\u003eThe comparative nature of this study warrants careful interpretation. Although total radiation exposure did not significantly differ between groups, the small sample size limits statistical power, and the absence of a significant difference should not be equated with definitive equivalence. Moreover, DSP was performed at the discretion of the endoscopist, introducing potential selection bias. It is possible that DSP was preferentially applied in cases in which enhanced visualization was anticipated to be useful, potentially reflecting greater procedural complexity. Conversely, in some instances, operators may have limited fluoroscopic duration because subtraction imaging provided sufficient anatomical information. These factors cannot be fully disentangled in a retrospective design. Therefore, while the present findings suggest that DSP does not markedly increase radiation exposure, larger prospective studies with predefined inclusion criteria and standardized imaging protocols are required to confirm these observations.\u003c/p\u003e \u003cp\u003eAdditional limitations should be considered. This was a single-center study with a limited number of patients, restricting generalizability. Diagnostic performance, impact on clinical decision-making, and long-term outcomes were not assessed. Interobserver agreement was evaluated; however, the limited variability in scoring and small sample size constrain definitive conclusions regarding reproducibility. Future investigations incorporating larger cohorts, refined scoring systems, and multicenter enrollment would provide a more robust evaluation of the clinical role of DSP.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eDuct-focused digital subtraction pancreatography was technically feasible and provided generally interpretable pancreatic duct visualization without a measurable increase in total radiation exposure compared with conventional pancreatography in this small retrospective cohort. Although a clear advantage over conventional imaging was not demonstrated, DSP may serve as a supplementary imaging technique in selected pancreatic duct interventions where background interference limits visualization. Further prospective and adequately powered studies are warranted to clarify its clinical role and optimal indications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Yokkaichi Municipal Hospital, Japan (Approval No. 2024-39).\u003cbr\u003e\u0026nbsp;The requirement for written informed consent was waived due to the retrospective observational nature of the study. An opt-out approach was implemented through public disclosure in accordance with institutional policy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAM: conceptualization, methodology, investigation, formal analysis, visualization, writing—original draft.\u003cbr\u003e\u0026nbsp;RT, SI, JY, HK, KT: data curation, investigation.\u003cbr\u003e\u0026nbsp;MK: supervision, validation, writing—review and editing.\u003cbr\u003e\u0026nbsp;All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFreeman ML, DiSario JA, Nelson DB, et al. 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Reduction of fluoroscopy frame rate decreases radiation exposure during ERCP. Am J Gastroenterol. 2021;116:S115.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTakenaka M, Hosono M, Hayashi S, et al. Radiation doses and radiation protection in ERCP procedures. Br J Radiol. 2021;94(1126):20210399.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeijering EH, Niessen WJ, Bakker J, et al. Reduction of patient motion artifacts in DSA: automatic technique vs pixel-shifting. Radiology. 2001;219(1):288\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeijering EH, Niessen WJ, Viergever MA. Retrospective motion correction in digital subtraction angiography: a review. IEEE Trans Med Imaging. 1999;18(1):2\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu B, Zhang B, Wan C, Dong Y. Non-rigid registration method for cerebral DSA images to reduce motion artifacts. Biomed Mater Eng. 2014;24(1):1149\u0026ndash;55.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOhnishi T, Takano Y, Kato H, et al. Respiratory-synchronized DSA based on respiratory phase matching. Signal Image Video Process. 2018;12(3):539\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSekiguchi Y, Okamoto T, Matsuzawa T, et al. PatchDSA: improving DSA with patch-based phase-matching under free breathing. Radiol Phys Technol. 2025;18(4):698\u0026ndash;706.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"406\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDSP (n=11)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eConventional (n=10)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eAge, median (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e76.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eFemale, n (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e5 (45%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e2 (20%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eIndication, n (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026ndash; Pancreatic juice cytology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e9 (82%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e7 (70%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026ndash; Stent placement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2 (18%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e3 (30%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal radiation dose (mGy), median (IQR)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e31.0 (13.7\u0026ndash;61.2)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 161px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e48.3 (30.7\u0026ndash;56.1)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-gastroenterology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmge","sideBox":"Learn more about [BMC Gastroenterology](http://bmcgastroenterol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmge/default.aspx","title":"BMC Gastroenterology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Digital subtraction, pancreatography, Endoscopic retrograde cholangiopancreatography, Pancreatic duct intervention","lastPublishedDoi":"10.21203/rs.3.rs-9250142/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9250142/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eDigital subtraction pancreatography (DSP) has been proposed as a technique to reduce background interference and facilitate pancreatic duct visualization during endoscopic procedures. However, objective evaluation of DSP image interpretability and its clinical applicability remains limited.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis single-center retrospective cohort study included 21 pancreatic ductography procedures performed between September 2022 and October 2025, comprising 11 DSP cases and 10 conventional pancreatography cases. Two independent endoscopists evaluated DSP images using predefined criteria for main pancreatic duct (MPD) visualization, background suppression, and branch duct visualization on a 3-point scale. Interobserver agreement was assessed. Secondary outcomes included technical feasibility, radiation exposure, and procedure-related adverse events.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eDSP was technically feasible in all cases (11/11, 100%), with successful acquisition of subtracted images using a single acquisition per procedure. Independent evaluation demonstrated that MPD visualization was acceptable in 91% and 100% of cases for the two reviewers, respectively. Background suppression was rated as acceptable in 82% and 100% of cases, while branch duct visualization showed greater variability (82% acceptable for both reviewers). Interobserver agreement was 91% for MPD visualization, 82% for background suppression, and 64% for branch duct visualization. Median total radiation dose did not differ significantly between DSP and conventional groups (31.0 vs. 48.3 mGy, p\u0026thinsp;=\u0026thinsp;0.65). No procedure-related adverse events were observed.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eDSP provided generally interpretable pancreatic duct visualization with background suppression and was feasible without increasing radiation exposure. Although no clear advantage over conventional pancreatography was demonstrated, DSP may serve as a supplementary imaging technique in selected cases where background interference limits duct visualization. Further studies are warranted to define its clinical indications.\u003c/p\u003e","manuscriptTitle":"Independent assessment of duct-focused digital subtraction pancreatography for pancreatic duct visualization: a retrospective pilot study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-12 07:39:02","doi":"10.21203/rs.3.rs-9250142/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-13T10:31:29+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-12T20:40:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-12T08:17:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"191104654954654559531940311548780903566","date":"2026-04-06T11:25:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"23222164887579441712295860370254783705","date":"2026-04-06T10:09:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-06T09:44:55+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-01T09:12:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-31T11:00:17+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-31T10:59:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Gastroenterology","date":"2026-03-28T06:10:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-gastroenterology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmge","sideBox":"Learn more about [BMC Gastroenterology](http://bmcgastroenterol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmge/default.aspx","title":"BMC Gastroenterology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"94cd96e1-a838-4e31-9f66-a31cc8650008","owner":[],"postedDate":"April 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-05-04T16:18:57+00:00","versionOfRecord":{"articleIdentity":"rs-9250142","link":"https://doi.org/10.1186/s12876-026-04872-9","journal":{"identity":"bmc-gastroenterology","isVorOnly":false,"title":"BMC Gastroenterology"},"publishedOn":"2026-04-29 15:57:19","publishedOnDateReadable":"April 29th, 2026"},"versionCreatedAt":"2026-04-12 07:39:02","video":"","vorDoi":"10.1186/s12876-026-04872-9","vorDoiUrl":"https://doi.org/10.1186/s12876-026-04872-9","workflowStages":[]},"version":"v1","identity":"rs-9250142","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9250142","identity":"rs-9250142","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}