Fluoroscopy Time Required for Each Step of Interventional Endoscopic Ultrasonography

Abstract

Objectives

Interventional endoscopic ultrasonography (I-EUS) exposes patients to high levels of radiation exposure. However, no research on the fluoroscopy time required for each step of I-EUS has been published. That was the aim of this study.

Materials and Methods

We retrospectively included patients who underwent endoscopic ultrasonography-guided biliary drainage (EUS-BD) and pancreatic duct drainage (EUS-PDD) in our hospital from October 2022 to November 2024. The procedure was categorized into four steps: step 1, transmural puncturing; step 2, guidewire placement; step 3, tract creation; and step 4, stent placement. We measured the fluoroscopy time required for each step via the fluoroscopic videos.

Statistical Analysis

Continuous variables were described using medians and the first to third quartiles (Q1–Q3).

Results

The study included 36 participants (EUS-BD: 33, EUS-PDD: 3). The median [Q1–Q3] fluoroscopy times required for steps 1 to 4 were 120 [96–152], 175 [123–449], 194 [101–303], and 171 [90–208] seconds, respectively, for EUS-BD and 169 [119–195], 302 [234–529], 435 [430–477], and 233 [170–266] seconds, respectively, for EUS-PDD.

Conclusions

In I-EUS, the fluoroscopy time required for step 3, tract creation, was the longest. The technique needs to be improved, new devices developed, and clear communication be established among the operating team to prevent unnecessary fluoroscopy.

 

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Keywords

fluoroscopy - interventional endoscopic ultrasonography - radiation exposure

Introduction

Interventional endoscopic ultrasonography (I-EUS) has rapidly spread as a novel drainage method for cases in which endoscopic retrograde cholangiopancreatography (ERCP) is challenging.[1] [2] [3] However, studies have revealed higher levels of radiation exposure during I-EUS than those during ERCP.[4] [5] Radiation exposure may cause direct DNA damage and DNA damage due to free radicals,[6] leading to tissue reactions and stochastic effects in organs throughout the body.[7] [8] Therefore, radiation protection is important for both patients and medical professionals.[6] [8] [9] The American Society for Gastrointestinal Endoscopy has defined the best practices for radiation protection in endoscopic therapy in terms of distance, time, shielding, the gantry angle, and magnification, among other considerations.[6] Notably, reducing fluoroscopy time (FT) for unneeded radiation is the simplest method to reduce radiation exposure.[8]

I-EUS includes the following four main steps[10]: step 1, transmural puncturing; step 2, placement of a guidewire (GW); step 3, creation of a tract; and step 4, placement of a stent. Although each of these steps involves fluoroscopy, the required FT for each step has not been reported. Evaluation of the FT of each step may enable optimization of the I-EUS procedure or development of novel equipment to reduce radiation exposure. Therefore, we aimed to evaluate the FT required for each step of I-EUS.

 

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Materials and Methods

Study Design

This single-center, retrospective study was approved by our institutional review board (approval number: KMEO B24–161) and conducted according to the tenets of the Declaration of Helsinki of 1975, as revised in 2000. Written informed consent for the procedure was obtained from all patients. For publication of this study, we used the opt-out method to gain patient consent. Specifically, we posted an announcement on our institution's Web site to inform patients about the study, and those who opted out were excluded from the study.

 

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Patient Eligibility

For this study, we included patients who underwent endoscopic ultrasonography (EUS)-guided biliary drainage (EUS-BD), EUS-guided hepaticogastrostomy (EUS-HGS), EUS-HGS with antegrade stenting, EUS-guided choledochoduodenostomy (EUS-CDS), and EUS-guided pancreatic duct drainage (EUS-PDD) from October 2022 to November 2024 in Kitasato University Hospital. We excluded cases in which determination of the FT was difficult and those in which the rendezvous technique was performed.

 

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I-EUS

I-EUS was performed with the patient under conscious sedation with concomitant pethidine hydrochloride and midazolam. The GF-UCT260 (Olympus Medical Systems, Tokyo, Japan) endoscope was used. The procedure was performed by board-certified fellows of the Japan Gastroenterological Endoscopy Society (experienced endoscopists) in all cases. As a general rule, a 19-gauge (G) needle was used for puncturing (step 1). For cases in which puncturing was difficult with a 19-G needle or the puncture target was too small, a 22-G needle was used at the discretion of the operator. In general, 0.025-inch GWs were used (step 2); however, 0.018-inch GWs were used if a 22-G needle was used for puncturing. For tract dilation (step 3), mechanical dilators were prioritized, and cautery dilation was performed in difficult cases. For minimal dilation, a standard ERCP cannula, bougie dilator (ES DILATOR; Zeon Medical Inc., Tokyo, Japan), balloon dilator (REN; Kaneka Medix Corporation, Osaka, Japan), and drill dilator (Tornus; Asahi Intecc Co., Ltd., Aichi, Japan) were selected at the discretion of the operator. If the stent was difficult to insert with one device or the operator judged the dilation insufficient for stent placement, additional dilation was conducted using another device. As a general rule, a 7-Fr Through and Pass Type IT stent (Gadelius Medical K.K., Tokyo, Japan) was placed (step 4). The procedure time (PT; min) was defined as the time from insertion to removal of the scope.

 

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Radiation Exposure

We used an over-couch X-ray system, the CUREVISTA (Hitachi Ltd., Tokyo, Japan), which was introduced in 2015. The default frame-rate setting was 6.3 frames per second (FPS); however, it was changed to 12.5 FPS when required for high-precision operation. The measurement items included the air kerma at the patient entrance reference point (K _a,r; mGy), air kerma–area product (P _KA; Gy·cm²), PT (min), and FT (s).[11] In all cases, fluoroscopy was performed by gastrointestinal endoscopists who had undertaken an e-learning course about the safe use of radiation at our institute.

 

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Measurement of FT

The FT required for each step was measured by evaluating the fluoroscopy videos taken during I-EUS ([Fig. 1]). For step 1, the duration of transmural puncture was defined as the time from the start of the examination, through puncturing and the contrast study, until the GW emerged from the tip of the puncturing needle. For step 2, the duration of placement of a GW was defined as the time from emergence of the GW from the tip of the puncture needle until the tip of the dilator emerged from the scope channel. For step 3, the duration of tract creation was defined as the time from emergence of the tip of the dilator from the scope until the tip of the stent emerged from the scope. For step 4, the duration of stent placement was defined as the time from emergence of the stent tip from the scope until the end of the procedure. If a step had to be repeated during the procedure, the time was added to the step that was repeated.

Fig. 1 Measurement of fluoroscopy time for each step of interventional endoscopic ultrasonography. (A, E) Step 1: transmural puncture; from the start of the examination, through puncturing and the contrast study, until the GW emerged from the tip of the puncturing needle. (B, F) Step 2: placement of a GW; from immediately after the GW emerged from the puncturing needle until the tip of the dilator emerged from the scope. (C, G) Step 3: creation of a tract; from immediately after the tip of the dilator emerged from the scope until the tip of the stent emerged from the scope. (D, H) Step 4: placement of a stent; from immediately after the tip of the stent emerged from the scope until the end of the procedure. GW, guidewire.

 

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Data Analyses

Statistical comparisons were performed using Mann–Whitney U-tests. Continuous variables were described using medians and the first to third quartiles (Q1–Q3). BellCurve for Excel Ver 4.08 (Social Survey Research Information Co., Ltd., Tokyo, Japan) was used for all the data analyses.

 

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Results

Patient Characteristics

The characteristics of the 36 participants are summarized in [Table 1]. Twenty-three were men (64%), the median age [Q1–Q3] was 72 [63–75] years, and the most common underlying diseases were pancreatic cancer (33%), biliary tract cancer (25%), and other malignant biliary obstruction (19%). Puncturing was performed with a 19-G needle in most cases (92%). Multiple needle punctures were necessary in 7/33 (21%) cases of EUS-BD and 1/3 (33%) cases of EUS-PDD. Eight patients required one dilator each (22%), 19 required two (53%), and 9 required three (25%). None of the cases required the use of a cautery dilator. Cases with multiple dilators were significantly associated with a longer FT in step 3 compared with the use of a single dilator (p < 0.001). Most of the placed stents were plastic (75%). The incidence of adverse events (AEs) in EUS-BD cases was 15% (5/33 cases), and that in EUS-PD was 0% ([Table 2]). All AEs were mild and resolved rapidly with conservative treatment. Patients with AEs tended to have a longer FT at all steps compared with patients without AEs ([Table 3]).

Table 1 Patient characteristics

	EUS-BD (n = 33)	EUS-PDD (n = 3)
Sex
Male	21 (64%)	2 (67%)
Female	12 (36%)	1 (33%)
Median age, years [Q1–Q3]	72 [63–74]	77 [63–82]
Type of biliary drainage
EUS-HGS	26 (79%)	0
EUS-HGS + AS	3 (9%)	0
EUS-CDS	4 (12%)	0
Primary disease
Pancreatic cancer	12 (36%)	0
Biliary cancer	9 (27%)	0
Other MBO	7 (21%)	0
Benign biliary stricture	3 (9%)	0
Benign pancreatic stricture		3 (100%)
Intrahepatic bile duct stone	2 (6%)	0
Puncturing needle
19-gauge needle	30 (91%)	3 (100%)
22-gauge needle	2 (6%)	0
19- + 22-gauge needle	1 (3%)	0
Number of dilators used
1	8 (24%)	0
2	18 (55%)	1 (33%)
3	7 (21%)	2 (67%)
Stent type
PS	24 (73%)	3 (100%)
SEMS	6 (18%)	0
PS + SEMS	3 (9%)	0

Abbreviations: AS, antegrade stenting; EUS-BD, endoscopic ultrasonography-guided biliary drainage; EUS-CDS, endoscopic ultrasonography-guided choledochoduodenostomy; EUS-HGS, endoscopic ultrasonography-guided hepaticogastrostomy; EUS-PDD, endoscopic ultrasonography-guided pancreatic duct drainage; MBO, malignant biliary obstruction; PS, plastic stent; Q1, first quartile; Q3, third quartile; SEMS, self-expandable metallic stent.

Table 2 Adverse events of interventional EUS

	EUS-BD				EUS-PDD
	EUS-HGS		EUS-HGS with AS	EUS-CDS
	Plastic stent, n = 21	SEMS, n = 2	Plastic stent + SEMS, n = 3	SEMS, n = 4	Plastic stent, n = 3
Fever	2 (10%)	0	0	0	0
Peritonitis	0	1 (50%)	1 (33%)	0	0
Pneumonia	0	0	0	1 (25%)	0

Abbreviations: AS, antegrade stenting; EUS, endoscopic ultrasonography; EUS-BD, endoscopic ultrasonography-guided biliary drainage; EUS-CDS, EUS-guided choledochoduodenostomy; EUS-HGS, endoscopic ultrasonography-guided hepaticogastrostomy; EUS-PDD, endoscopic ultrasonography-guided pancreatic duct drainage; SEMS, self-expandable metallic stent.

Table 3 Fluoroscopy times according to adverse events

	AE group, median [Q1–Q3]	No AE group, median [Q1–Q3]	p-Value
Step 1	210 [139–413]	112 [88–144]	0.01
Step 2	482 [450–749]	167 [121–269]	0.07
Step 3	309 [211–474]	193 [80–259]	0.07
Step 4	261 [198–626]	135 [81–185]	0.01

Abbreviations: AE, adverse event; Q1, first quartile; Q3, third quartile.

Note: Step 1: transmural puncture; step 2: guidewire placement; step 3: tract creation; step 4: stent placement.

 

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Radiation Exposure

The median [Q1–Q3] values of K _a,r, P _KA, PT, and FT were 69.1 [50.0–163.1] mGy, 14.2 [9.6–23.2] Gy·cm², 28 [21–45] minutes, and 652 [542–1242] seconds, respectively, for EUS-BD and 204.2 [182.3–259.8] mGy, 24.8 [23.3–31.3] Gy·cm², 30 [30–38] minutes, and 1,105 [1,032–1,369] seconds, respectively, for EUS-PDD. The median [Q1–Q3] FT for steps 1 to 4 of I-EUS were 120 [96–152], 175 [123–449], 194 [101–303], and 171 [90–208] seconds, respectively, for EUS-BD and 169 [119–195], 302 [234–529], 435 [430–477], and 233 [170–266] seconds, respectively, for EUS-PDD ([Tables 4] and [5]). For EUS-BD and EUS-PD, step 3 required the longest FT. However, when limited to EUS-CDS and EUS-HGS with antegrade stenting, step 2 required the longest FT.

Table 4 Radiation exposure and procedure time per procedure

	K a,r (mGy), median [Q1–Q3]	P KA (Gy/cm2), median [Q1–Q3]	PT (min), median [Q1–Q3]	FT (s), median [Q1–Q3]
EUS-BD (n = 33)	69.1 [50.0–163.1]	14.2 [9.6–23.2]	28 [21–45]	652 [542–1,242]
EUS-PDD (n = 3)	204.2 [182.3–259.8]	24.8 [23.3–31.3]	30 [30–38]	1,105 [1,032–1,369]

Abbreviations: EUS-BD, endoscopic ultrasonography-guided biliary drainage; EUS-PDD, endoscopic ultrasonography-guided pancreatic duct drainage; FT, fluoroscopy time; K _a,r, air kerma at the patient entrance reference point; P _KA, air kerma–area product; PT, procedure time; Q1, first quartile; Q3, third quartile.

Table 5 Fluoroscopy time at each step in interventional EUS

	Step 1 (s), median [Q1–Q3]	Step 2 (s), median [Q1–Q3]	Step 3 (s), median [Q1–Q3]	Step 4 (s), median [Q1–Q3]
EUS-BD (n = 33)	120 [96–152]	175 [123–449]	194 [101–303]	171 [90–208]
EUS-HGS (n = 26)	114 [96–142]	155 [116–212]	195 [112–308]	112 [78–185]
EUS-HGS + AS (n = 3)	163 [108–307]	449 [385–599]	211 [181–240]	374 [318–407]
EUS-CDS (n = 4)	156 [109–196]	370 [215–484]	134 [76–389]	192 [186–201]
EUS-PDD (n = 3)	169 [119–195]	302 [234–529]	435 [430–477]	233 [170–266]

Abbreviations: AS, antegrade stenting; EUS, endoscopic ultrasonography; EUS-BD, endoscopic ultrasonography-guided biliary drainage; EUS-CDS, EUS-guided choledochoduodenostomy; EUS-HGS, endoscopic ultrasonography-guided hepaticogastrostomy; EUS-PDD, endoscopic ultrasonography-guided pancreatic duct drainage; Q1, first quartile; Q3, third quartile.

Note: Step 1: transmural puncture; step 2: placement of a guidewire; step 3: creation of a tract; step 4: placement of a stent.

 

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Discussion

Time, distance, and shield are considered important factors for optimization in terms of radiation protection. Time, in particular, is believed to have the biggest influence on the radiation dose because the radiation dose and FT are directly proportional.[6] [12] Reducing the time is especially important because it can reduce radiation exposure of both patients and medical professionals, unlike the other optimization factors. Although several studies have been conducted on radiation exposure with I-EUS,[4] [5] [13] [14] the FT required for each step of I-EUS was not previously reported.

In this study, the median FT in both EUS-BD and EUS-PDD was the longest for step 3 (tract creation), followed by that for steps 2 (GW placement), 4 (stent placement), and 1 (transmural puncturing). Dilation performed for tract creation is considered one of the most difficult steps of the procedure,[15] complicating I-EUS because of solid organs that need to be punctured owing to inflammation and fibrosis, for example. Even though a dilator can be inserted, re-dilation may be required owing to the failure of subsequent stent insertion. In fact, successful stent placement with only one dilation attempt was achieved in only 22% of cases in this study. In addition, cases with multiple dilations had a significantly higher FT (p < 0.001) than those with a single dilation. Itonaga et al[16] reported that stent placement is significantly more successful without tract dilation when self-expandable metallic stents (SEMSs) were placed with a delivery system <7.5 Fr than that when SEMSs were placed with a delivery system ≥7.5 Fr (82% vs. 33%, p < 0.001), indicating that a narrower delivery system may reduce the PT by removing the dilation step. Taken together, fluoroscopic confirmation is needed both for device switching and tract creation itself. Therefore, the development of a stent with a narrow delivery system may lead to a shortened dilation step.

The FT required for step 2 (GW placement) was the longest in EUS-CDS and EUS-HGS with antegrade stenting. This may be because, in EUS-CDS, the GW must be placed in the biliary branch to straighten the bile duct and ease the dilation process, which increases placement time. Moreover, in EUS-HGS with antegrade stenting, the GW must pass through severe strictures. Fluoroscopy is necessary not only in step 3 but in all the steps, as the median FT exceeded 100 seconds in each I-EUS step. Additionally, patients with AEs tended to have a longer FT in all steps than those without AEs. Therefore, a longer PT might have led to an increased FT and, thus, higher AE rates. For this reason, the entire procedure needs to be shortened. We believe that PT reduction and communication improvements are vital for FT reduction.

Both technical[17] [18] and device-related aspects[19] must be understood if the I-EUS PT is to be reduced. In terms of technical aspects, for the puncture step, only an angle between the needle and echoendoscope >135° was independently associated with successful GW insertion (odds ratio: 0.03, 95% confidence interval: 0.01–0.14; p < 0.05) in EUS-HGS in one study.[20] In EUS-PDD, the area between the gastric body and cardia is deemed the best region for puncturing.[18] [21] I-EUS is a highly complex procedure that should be performed by experienced endoscopists.[22] [23] The fact that I-EUS involves higher levels of radiation exposure than ERCP[4] [5] further underlines this necessity. In this study, the overall FT of EUS-PDD was long, 1,105 seconds. Given that the scope used for EUS-PDD is unstable and that the pancreatic parenchyma is hard and fibrotic, it is considered the most difficult ultrasonic endoscopy technique to master.[18] Therefore, this technique should also be performed by experienced endoscopists to minimize the FT.

As for device-related aspects, various devices have been developed in recent years,[19] such as a drill dilator,[15] [24] one-step tract dilation using a long balloon catheter,[25] and a new stent placement method using a tapered-sheath dilator.[26] These devices are mainly evaluated in terms of their success rate and the prevalence of complications, but the FT and PT should be included in future evaluations. Recently, drainage via lumen-apposing metal stents (LAMSs) has attracted attention. EUS-CDS via LAMSs may enable stent placement without fluoroscopy.[27] [28] In a multicenter, randomized controlled trial of patients with malignant biliary obstruction who were randomized to undergo EUS-CDS using a LAMS or to undergo ERCP for comparison, drainage was performed without fluoroscopy in 40% of the EUS-CDS group.[29] Thus, understanding both technical and device-related aspects may lead to a reduction in PT and, ultimately, a reduction in the FT.

Along with reduction of the PT, communication is vital. Generally, the fluoroscopy technician is a different person from the operator and assistant, which may lead to unnecessarily prolongation of the FT unless communication is clear. A clear discussion of procedural details and expected issues during a preliminary conference may improve a team's ability to perform I-EUS in a short time. A new eye-tracking fluoroscopy system that uses artificial intelligence has recently been developed to reduce the time of exposure to endoscopic radiation. It informs the fluoroscopy technician when the operator's line of sight is directed toward the monitor, which may be useful to reduce the FT.[30] Patients requiring I-EUS often need to undergo multiple endoscopic procedures. Medical staff are also exposed to radiation during repeated procedures. Therefore, we believe that the cumulative effect of even a small reduction in the FT will reduce patients' and medical staff's lifetime radiation exposure.

This study has several limitations. First, it was a single-center study with a small number of participants. The procedures were biased toward EUS-HGS (only three cases of EUS-PDD). Because of the small sample size, we were unable to compare the dilation process between EUS-PDD and EUS-BD, such as the reasons why multiple dilations were required or which dilators were used and in what order. Second, it was a retrospective study, and the dilators were selected based on the operator's experience and judgment. These selections might have biased our results and limited their interpretability. Additionally, the PT could not be measured in each step, and the measurement of FT was reviewed using videos; therefore, the correlation between PT and FT could not be examined. To solve these limitations, a multi-center, prospective study with standardized criteria is needed to confirm our results.

 

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Conclusion

Among the steps in I-EUS, the FT required for step 3, tract creation (dilation), was the longest. However, the FT can only be reduced if all steps are shortened. The technique needs to be improved and clear communication among the operating team is necessary to prevent any unnecessary fluoroscopy.

 

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Conflict of Interest

None declared.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Authors' Contributions

M.W. designed the study and drafted the initial manuscript. K.O., M.K., and H.I. contributed to data analysis and interpretation and assisted in manuscript preparation. All other authors participated in data collection and interpretation and critically reviewed the manuscript. All authors approved the final version and agreed to be accountable for all aspects of the work, ensuring that any questions regarding accuracy or integrity are properly investigated and resolved.

Ethical Approval

This study was approved by our institutional review board (approval number: KMEO B24–161) and conducted according to the tenets of the Declaration of Helsinki of 1975, as revised in 2000. Written informed consent for the procedure was obtained from all patients. For publication of this study, authors used the opt-out method to gain patient consent. Specifically, they posted an announcement on our institution's Web site to inform patients about the study, and those who opted out were excluded from the study.

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Publication History

Article published online:
22 August 2025