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Time-limited fluoroscopy to reduce radiation exposure during ERCP: a prospective randomized trial
ORIGINAL ARTICLE: Clinical Endoscopy
Time-limited fluoroscopy to reduce radiation exposure during ERCP: a prospective randomized trial Lance T. Uradomo, MD, MPH, Eric M. Goldberg, MD, Peter E. Darwin, MD Baltimore, Maryland, USA
Background: Measures should be used to limit radiation exposure of the staff and patients during ERCP. Objective: To determine whether ‘‘time-limited fluoroscopy’’ reduces radiation exposure and fluoroscopy time (FT) compared with continuous fluoroscopy. Design: Prospective randomized trial. Setting: Tertiary academic medical center. Patients: Consecutive adult patients presenting for ERCP. Interventions: Subjects were randomized into 2 fluoroscopy setting groups: (1) time-limited, where x-ray exposure is limited to 3 seconds each time the foot-operated switch is depressed; (2) continuous, where xray exposure continues for as long as the switch is depressed. Main Outcomes Measurements: FT, patient, and procedure-related data were recorded. Radiation dosimetry badges were used to estimate cumulative exposure. Results: Ninety-nine procedures were performed in the time-limited group and 100 by using continuous fluoroscopy. The mean FT for time-limited fluoroscopy was 284.4 seconds (95% confidence interval [CI] 247.1-321.6) and for continuous fluoroscopy was 314 seconds (95% CI 265.6-362.4; P Z .34). Longer FT was associated with moderate or difficult cannulation (P Z.008), lithotripsy (P !.001), stent placement (P Z.007), sphincterotomy (P ! .001), and longer overall procedure length (P ! 0.001). After controlling for confounding factors and interactions with a multiple linear regression model, time-limited fluoroscopy was associated with a 16.4% lower FT (P Z .029). The average radiation dose was not amenable to multivariate analysis, and, therefore, no significant difference between groups was found. Limitations: Endoscopists were not blinded to the study group assignments. Conclusions: FT and radiation exposure are dependent upon numerous patient-, operator-, and procedurerelated factors. This study found that, after controlling for the impact of confounding factors, time-limited fluoroscopy significantly decreases FTs. (Gastrointest Endosc 2007;66:84-9.)
During ERCP, fluoroscopy is used to obtain cholangiograms and/or pancreatograms via the injection of radiopaque contrast into the desired duct. ERCP, like all fluoroscopic procedures, carries the risk of exposure of patients and the staff to radiation.1-4 Ionizing radiation can have a harmful impact on health, including immediate effects and long-term consequences.5 Steps should, there-
See CME section; p. 126. Copyright ª 2007 by the American Society for Gastrointestinal Endoscopy 0016-5107/$32.00 doi:10.1016/j.gie.2006.10.055
84 GASTROINTESTINAL ENDOSCOPY Volume 66, No. 1 : 2007
fore, be taken to minimize radiation exposure to patients and staff.
PATIENTS AND METHODS Patients Consecutive adult patients who presented to a single university-based endoscopy unit for ERCP between September 2004 and March 2005 were eligible for enrollment. Participants included both inpatients and outpatients. Patient age, race, and sex were recorded. The study was approved by the institutional review board of the www.giejournal.org
Uradomo et al
Timed fluoroscopy to reduce radiation exposure during ERCP
University of Maryland, Baltimore. Written informed consent was obtained from all participants.
Capsule Summary
Procedures
What is already known on this topic
Patients were prospectively randomized into 2 groups: (1) ‘‘time-limited fluoroscopy,’’ where a timer terminates x-ray exposure 3 seconds after the foot-operated switch is depressed and further exposure requires reactivation of the switch; (2) continuous fluoroscopy, the standard setting where x-ray exposure continues for as long as the switch is depressed. The fluoroscopy equipment was adjusted after randomization, immediately before beginning each ERCP. The endoscopist was not blinded to group assignment, because the fluoroscopy setting was obvious once the pedal was depressed. All procedures were performed by using the same fluoroscopy equipment, OEC series 9600 C-arm (OEC Medical, Salt Lake City, Utah). The fluoroscopy pedal switch was controlled by the attending gastroenterologist. Neither a radiologist nor a radiology technician was involved in the procedures. All procedures were performed by 1 of 2 attending gastroenterologists. The majority of procedures included the participation of 1 of 3 gastroenterology fellows in their third years of subspecialty training. Each fellow participated in between 37 and 102 procedures before the initiation of this study. There was no preestablished protocol to determine the level of fellow participation. This was determined by the attending physician on a case-by-case basis. Most procedures used nurse-administered conscious sedation. General anesthesia was used in a minority of procedures. The reason for the use of general anesthesia was not recorded for this study. Two of these cases (1%) were first attempted with conscious sedation. A sample-size calculation before the initiation of the study identified a requirement of 99 procedures per group to measure a 20% difference in mean fluoroscopy time (FT) with a power of 0.80.
Data collection Immediately after each procedure, FT, patient, and procedure-related data were recorded on a standard datacollection form. Procedure data included endoscopist, assistants, indication, procedure duration (from endoscope insertion to removal), sedation drugs and doses, and complications. In addition, the following technical components were recorded by the endoscopist as successful, failed, or not attempted: cholangiography, sphincterotomy, pancreatography, stone extraction, dilation, minor papilla, stent insertion, Billroth II anatomy, lithotripsy, cytology, manometry, pseudocyst drainage. A scoring system rated cannulation of the desired duct as easy (!5 touches), moderate (6-15 touches), or difficult (O15 touches).6 Radiation dosimetry badges were also positioned during each case to estimate exposure to (1) patients, (2) sedation nurse, and (3) endoscopist. The patient badge was placed at the bedside at the edge of the www.giejournal.org
d
The use of fluoroscopy during ERCP exposes patients and staff to ionizing radiation, but modifications in unit settings can reduce exposure times and radiation dose.
What this study adds to our knowledge d
In a prospective randomized study of 100 ERCP cases with time-limited fluoroscopy and 99 cases with standard, continuous fluoroscopy, procedure time was 16.4% lower in the time-limited group after controlling for the confounding factors.
radiation-beam field. The nurse badge was placed at the head of the patient’s bed, and the endoscopist badge was worn outside of the physician’s lead apron. These were analyzed in a blinded fashion by the university’s radiation safety department.
Statistical analysis Mean FT (and 95% confidence intervals [CI]) is expressed in seconds. Parametric data were compared by using the t test. Dichotomous variables were analyzed with the Pearson c2 test and the Fisher exact test. Simple linear regression models identified variables that predicted the FT. A 2-sided P value !.05 was considered significant. If significant interaction was found between a variable and a group assignment, an interaction term was created. Finally, a stepwise multiple linear regression analysis was performed to control for the effect of demographic and procedure-related factors on the association between the study group and the FT. Variables were used if they were significant on simple linear regression. Variables were included in the final model if the P value was !.05. All analyses were performed by using statistical software (Intercooled Stata, version 8.2; StataCorp LP, College Station, Tex).
RESULTS Patient characteristics Patients, undergoing a total of 199 procedures, were enrolled: 99 in the continuous fluoroscopy group and 100 in the ‘‘time-limited’’ fluoroscopy group (Table 1). Forty-seven percent were women. The mean age of the patients was 58.6 years. Patients in the time-limited group had a higher mean age compared with the continuous group, 62.5 years vs 54.6 years (P Z .003). Whites comprised 77% of the patient population. African Americans, Latinos, and Asian Americans accounted for 19%, 2%, and 2%, respectively. There was no significant difference in the racial composition of the groups (P Z .96). Volume 66, No. 1 : 2007 GASTROINTESTINAL ENDOSCOPY 85
Timed fluoroscopy to reduce radiation exposure during ERCP
Uradomo et al
Procedure characteristics The ERCPs were performed by 2 attending gastroenterologists. There was no significant difference in the distribution of the time-limited and the continuous fluoroscopy cases between the physicians (P Z .58). Gastroenterology fellows were involved in 98% of procedures, with no difference between the study groups (P Z .67). The vast majority of cases were performed with the patient under conscious intravenous sedation; general anesthesia was used in only 7% of cases. No difference was found in the rate of general anesthesia use between groups (P Z .79). The mean procedure duration (endoscope insertion to removal) was 39.3 minutes. There was no significant difference between groups (P Z .48). The most common technical component performed was cholangiography, performed in 89% of cases. Sphincterotomy (59%), stent placement (59%), and pancreatography (50%) were also frequently performed. Despite similar proportions of cases where each maneuver was performed, in 36 cases (18.1%), a sphincterotomy was performed without stent insertion, and, in 35 cases (17.6%), a stent was placed without performing a sphincterotomy. When comparing the 2 study groups, cytology brushing was significantly more common in the time-limited group (26.7% vs 15.2%, P Z .044). Pancreatography was performed significantly more in the continuous group (57.6% vs 42.6%, P Z .034). A trend toward more sphincterotomies was seen in the continuous group (65.7% vs 52.5%, P Z .058). Cannulation difficulty was measured on a scale according to the number of touches on the papilla required for successful cannulation. The scale ranged from easy (score, 1) to difficult (score, 3). This variable was analyzed in 2 ways. First the mean score between the 2 groups was compared. Cases in the continuous fluoroscopy group had a mean cannulation difficulty score of 1.52. Those in the time-limited group had a mean score of 1.3 (P value for difference, .026). The variable was also dichotomized by grouping moderate and difficult cannulations and comparing them with an easy cannulation. Easy cannulations were observed in 60.1% and 73.3% of cases in the continuous and time-limited groups, respectively (P Z .057).
Bivariate analyses The mean FTs were analyzed with respect to each recorded patient and procedure-related variable (Table 2). Significant predictors of FT were attending physician (P Z .038), cannulation difficulty (P Z .008), stent insertion (P Z .008), lithotripsy (P ! .001), sphincterotomy (P % .001), and total procedure duration (P ! .001). Bivariate analysis found that the fluoroscopy group was not a significant predictor of FT. The mean time was 314 seconds (95% CI 265.6–362.4) in the continuous group and 284.4 seconds (95% CI 247.1–321.6) in the time-limited group (P Z .34). Despite randomization, this finding 86 GASTROINTESTINAL ENDOSCOPY Volume 66, No. 1 : 2007
TABLE 1. Patient and procedure characteristics Group
Total subjects Mean age (95% CI), y Female, no. (%)
Continuous
Time limited
99
100
P
54.59 (50.7-58.4) 62.51 (59.1-65.9) .003 54 (54.6)
41 (41.0)
.056
6 (6.0)
7 (7.0)
.789
A
59 (48.0)
64 (52.0)
.580
B
40 (52.0)
37 (48.0)
General anesthesia, no. (%) Endoscopist, no. (%)
Cannulation difficulty, mean score
1.52
1.3
.026
Easy cannulation, no. (%)
60 (60.6)
74 (73.3)
.057
Fellow involvement, no. (%)
97 (98.0)
98 (97.0)
.667
Cholangiogram
88 (88.9)
89 (88.1)
.864
Sphincterotomy
65 (65.7)
53 (52.5)
.058
Pancreatogram
57 (57.6)
43 (42.6)
.034
Stent
54 (54.6)
63 (62.4)
.261
Stone extraction
24 (24.2)
29 (28.7)
.474
Cytology
15 (15.2)
27 (26.7)
.044
Dilation
10 (10.1)
9 (8.9)
.774
Lithotripsy
7 (7.1)
12 (11.9)
.246
Manometry
4 (4.0)
3 (3.0)
.681
Minor papilla cannulation
3 (3.0)
4 (4.0)
.720
0 (0.0)
3 (3.0)
.084
Pseudocyst drainage
0
1 (1.0)
.321
Mean procedure duration, min
38.13
40.45
.480
Intervention attempted, no. (%)
Billroth anatomy
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Uradomo et al
Timed fluoroscopy to reduce radiation exposure during ERCP
TABLE 2. Associations of patient and procedure characteristics with the mean FT
N
Mean fluoroscopy time, sec
Continuous
99
314.0
265.6362.4
Time limited
100
284.4
247.1321.6
95% CI
TABLE 2 (continued )
P
N
Mean fluoroscopy time, sec
99
305.6
266.5344.7
No
180
290.4
259.1321.7
Yes
19
381.5
264.9498.1
No
83
250.8
201.9299.6
Yes
116
333.7
295.8371.5
No
181
279.4
248.9- !.001 309.8
Yes
18
497.3
390.9603.8
No
82
234.2
193.0- !.001 275.4
Yes
117
344.6
303.4385.8
No
147
287.1
251.6322.7
Yes
52
332.9
273.9392.0
No
157
295.0
258.4331.5
Yes
42
314.5
267.7361.3
%Mean
115
187.4
168.3- !.001 206.4
OMean
84
452.1
400.5503.7
Yes
Group .337
77
339.2
289.6388.9
B
122
273.7
235.6311.9
.038
186
297.2
266.7327.7
General anesthesia
13
326.5
145.1507.8
.639
Cannulation difficulty Moderate, difficult, or failed Easy
.082
Stent
Anesthesia Moderate sedation
P
Dilation
Endoscopist A
95% CI
.008
Lithotripsy
Sphincterotomy 65
357.0
300.6413.3
134
271.0
235.7306.3
.008
Stone extraction
Sex Male Female
104
313.4
273.1353.7
95
283.5
237.2329.7
.332
Fellow involvement No fellow Fellow
.192
Cytology 5
224.4
131.3317.5
194
301.0
270.0332.0
.437
.606
Total procedure duration
Maneuver Cholangiogram No
23
270.9
174.6367.2
Yes
176
302.8
270.6335.0
100
292.7
245.8339.6
.509
Pancreatogram No
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.676
was confounded by the interaction between the group assignment and factors significantly associated with FT. Cannulation difficulty is the most notable example, showing associations with both group and FT. Sphincterotomy Volume 66, No. 1 : 2007 GASTROINTESTINAL ENDOSCOPY 87
Timed fluoroscopy to reduce radiation exposure during ERCP
TABLE 3. Independent predictors of FT during ERCP: results of a stepwise linear regression analysis Variable Time-limited fluoroscopy Procedure duration Stent placement Lithotripsy Overall model
Coefficient -51.6
P
95% CI
.029 -97.5 to -5.8
5.5
!.001
4.4-6.5
47.3
.048
147.6
!.001
66.8-228.5
69.6
.075
15.6-123.5
0.5-94.2
showed a trend toward significant association with group assignment (P Z .058).
Multivariate analysis To account for these confounders and interactions, a multiple linear regression model was created (Table 3). The model was constructed in a stepwise fashion to include all factors found to be significantly predictive of FT. Interaction terms were created for group assignment with cannulation difficulty and sphincterotomy. Factors found to be significant independent predictors of FT were group assignment (P Z .029), procedure duration (P ! .001), lithotripsy (P!.001), and stent placement (P Z.048). The regression coefficient for the use of time-limited fluoroscopy was –51.6. In other words, controlling for the variables in the model, time-limited fluoroscopy was associated with a 51.6-second (16.4%) lower mean FT.
Dose comparison Radiation dose badges were collected throughout the study period. Doses were then calculated cumulatively for each group. The average dose per procedure was nearly identical for the groups. The physician’s mean dose per case was 3.67 mrem and 4.24 mrem for the time-limited and continuous groups, respectively. Estimated nurse doses were 2.72 mrem and 2.80 mrem, whereas estimated patient doses were 50.6 mrem and 46.6 mrem. Further analysis was not performed because the dose was not calculated for each individual procedure.
DISCUSSION Physician experience, radiation-beam strength, type of fluoroscopy equipment, and shielding of patients and staff have been previously shown to impact radiation exposure.3,7-10 Intermittent or pulsed fluoroscopy is another method that substantially reduces the radiation dose without sacrificing image quality.11 A study of GI radiologic procedures found that the diagnostic acceptability of studies with fluoroscopy frame rates as low as 3.5 frames per second was statistically equivalent to those performed at 15 frames per second.12 88 GASTROINTESTINAL ENDOSCOPY Volume 66, No. 1 : 2007
Uradomo et al
Perhaps the most readily modifiable method of reducing x-ray exposure is the reduction of the FT. A complex combination of patient- and procedure-related factors combine to determine the final FT. As expected, longer procedures and those with difficult cannulations or complex interventions were found in this study to have significantly longer FTs. On initial bivariate analysis, a significant association was not found between the time-limited setting and the FT. This negative finding can be traced to difficulty of controlling for every relevant factor that determines the FT. Despite the randomized design of the study, an uneven distribution of key variables occurred. This issue was overcome by the creation of a robust multivariate model. That analysis showed the independent FT-lowering effect of the fluoroscopy setting, with a significant (P Z .029) 51.6 seconds (16.4%) lower FT in the time-limited group. This difference is clinically meaningful as well. The average output of the fluoroscopy equipment used in this study was 1.5 rem per minute. The use of the time-limited setting could, therefore, result in a dose reduction of 1.29 rem per case or the equivalent of approximately 13 abdominal radiographs. One of the limitations of the study was that the endoscopists were not blinded to the study group assignment. Blinding was impossible, because the fluoroscopy setting is readily apparent once the activation pedal is depressed. In fact, one likely mechanism of its FT-lowering effect is that the time-limited setting functions as a reminder and a training reinforcement tool. The need to repeatedly redepress the fluoroscopy pedal can be a difficult adjustment for the endoscopist. Although this did not result in longer overall procedure times or increased failure rates, the consensus of the endoscopists was that using the time-limited setting was cumbersome. Alteration of the timer to allow for 4 or 5 seconds of fluoroscopy, rather than the arbitrarily chosen 3 seconds used in this study, would, perhaps, address this issue while still providing the reminder to limit the FT. This study also did not directly measure the dose for each procedure. Only aggregate dose data were collected. Because the unadjusted mean FT was not significantly different between groups, there was no difference in the radiation dose. All endoscopists who use fluoroscopy should strive to minimize radiation exposure during their procedures. This study shows that FT is a modifiable component in that process and proposes one method, the time-limited fluoroscopy setting, of achieving that goal.
DISCLOSURE The authors have no financial disclosures or conflicts of interest. www.giejournal.org
Uradomo et al
REFERENCES 1. McParland B. A study of patient radiation doses in interventional radiological procedures. Br J Radiol 1998;71:175-85. 2. Buls N, Pages J, Mana F, et al. Patient and staff exposure during endoscopic retrograde cholangiopancreatography. Br J Radiol 2002;75: 435-43. 3. Chen M, Van Swearingen F, Mitchell R, et al. Radiation exposure during ERCP: effect of a protective shield. Gastrointest Endosc 1996;43:1-5. 4. Larkin C, Workman A, Wright R, et al. Radiation doses to patients during ERCP. Gastrointest Endosc 2001;53:161–114. 5. Miller DL, Balter S, Noonan PT, et al. Minimizing radiation-induced skin injury in interventional radiology procedures. Radiology 2002;225: 329-36. 6. Freeman ML, Nelson DB, Sherman S, et al. Complications of endoscopic biliary sphincterotomy. N Engl J Med 1996;335:909-19. 7. Uradomo LT, Lustberg ME, Darwin PE. Effect of physician training on fluoroscopy time during ERCP. Dig Dis Sci 2006;51:909-14. 8. Johlin F, Pelsang R, Greenleaf M. Phantom study to determine radiation exposure to medical personnel involved in ERCP fluoroscopy and its reduction through equipment and behavior modifications. Am J Gastroenterol 2002;97:893-7.
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Timed fluoroscopy to reduce radiation exposure during ERCP 9. Campbell N, Sparrow K, Fortier M, et al. Practical radiation safety and protection for the endoscopist during ERCP. Gastrointest Endosc 2002;55:552-7. 10. Cohen R, Aldred M, Paes W, et al. How safe is ERCP to the endoscopist? Surg Endosc 1997;11:615-7. 11. Martin CJ. A review of factors affecting patient doses for barium enemas and meals. Br J Radiol 2004;77:864-8. 12. Boland GWL, Murphy B, Arellano R, et al. Dose reduction in gastrointestinal and genitourinary fluoroscopy: use of grid-controlled pulsed fluoroscopy. AJR Am J Roentgenol 2000;175:1453-7.
Received August 23, 2006. Accepted October 23, 2006. Current affiliations: Division of Gastroenterology and Hepatology, University of Maryland Medical Center, Baltimore, Maryland, USA. Presented at Digestive Disease Week, May 21-24, 2006, Los Angeles, California (Gastrointest Endosc 2006;63:AB104). Reprint requests: Lance T. Uradomo, MD, Division of Gastroenterology and Hepatology, University of Maryland Medical Center, Rm N3W62, 22 South Green St, Baltimore, MD 21201.
Volume 66, No. 1 : 2007 GASTROINTESTINAL ENDOSCOPY 89
Time-limited fluoroscopy to reduce radiation exposure during ERCP: a prospective randomized trial Lance T. Uradomo, MD, MPH, Eric M. Goldberg, MD, Peter E. Darwin, MD Baltimore, Maryland, USA
Background: Measures should be used to limit radiation exposure of the staff and patients during ERCP. Objective: To determine whether ‘‘time-limited fluoroscopy’’ reduces radiation exposure and fluoroscopy time (FT) compared with continuous fluoroscopy. Design: Prospective randomized trial. Setting: Tertiary academic medical center. Patients: Consecutive adult patients presenting for ERCP. Interventions: Subjects were randomized into 2 fluoroscopy setting groups: (1) time-limited, where x-ray exposure is limited to 3 seconds each time the foot-operated switch is depressed; (2) continuous, where xray exposure continues for as long as the switch is depressed. Main Outcomes Measurements: FT, patient, and procedure-related data were recorded. Radiation dosimetry badges were used to estimate cumulative exposure. Results: Ninety-nine procedures were performed in the time-limited group and 100 by using continuous fluoroscopy. The mean FT for time-limited fluoroscopy was 284.4 seconds (95% confidence interval [CI] 247.1-321.6) and for continuous fluoroscopy was 314 seconds (95% CI 265.6-362.4; P Z .34). Longer FT was associated with moderate or difficult cannulation (P Z.008), lithotripsy (P !.001), stent placement (P Z.007), sphincterotomy (P ! .001), and longer overall procedure length (P ! 0.001). After controlling for confounding factors and interactions with a multiple linear regression model, time-limited fluoroscopy was associated with a 16.4% lower FT (P Z .029). The average radiation dose was not amenable to multivariate analysis, and, therefore, no significant difference between groups was found. Limitations: Endoscopists were not blinded to the study group assignments. Conclusions: FT and radiation exposure are dependent upon numerous patient-, operator-, and procedurerelated factors. This study found that, after controlling for the impact of confounding factors, time-limited fluoroscopy significantly decreases FTs. (Gastrointest Endosc 2007;66:84-9.)
During ERCP, fluoroscopy is used to obtain cholangiograms and/or pancreatograms via the injection of radiopaque contrast into the desired duct. ERCP, like all fluoroscopic procedures, carries the risk of exposure of patients and the staff to radiation.1-4 Ionizing radiation can have a harmful impact on health, including immediate effects and long-term consequences.5 Steps should, there-
See CME section; p. 126. Copyright ª 2007 by the American Society for Gastrointestinal Endoscopy 0016-5107/$32.00 doi:10.1016/j.gie.2006.10.055
84 GASTROINTESTINAL ENDOSCOPY Volume 66, No. 1 : 2007
fore, be taken to minimize radiation exposure to patients and staff.
PATIENTS AND METHODS Patients Consecutive adult patients who presented to a single university-based endoscopy unit for ERCP between September 2004 and March 2005 were eligible for enrollment. Participants included both inpatients and outpatients. Patient age, race, and sex were recorded. The study was approved by the institutional review board of the www.giejournal.org
Uradomo et al
Timed fluoroscopy to reduce radiation exposure during ERCP
University of Maryland, Baltimore. Written informed consent was obtained from all participants.
Capsule Summary
Procedures
What is already known on this topic
Patients were prospectively randomized into 2 groups: (1) ‘‘time-limited fluoroscopy,’’ where a timer terminates x-ray exposure 3 seconds after the foot-operated switch is depressed and further exposure requires reactivation of the switch; (2) continuous fluoroscopy, the standard setting where x-ray exposure continues for as long as the switch is depressed. The fluoroscopy equipment was adjusted after randomization, immediately before beginning each ERCP. The endoscopist was not blinded to group assignment, because the fluoroscopy setting was obvious once the pedal was depressed. All procedures were performed by using the same fluoroscopy equipment, OEC series 9600 C-arm (OEC Medical, Salt Lake City, Utah). The fluoroscopy pedal switch was controlled by the attending gastroenterologist. Neither a radiologist nor a radiology technician was involved in the procedures. All procedures were performed by 1 of 2 attending gastroenterologists. The majority of procedures included the participation of 1 of 3 gastroenterology fellows in their third years of subspecialty training. Each fellow participated in between 37 and 102 procedures before the initiation of this study. There was no preestablished protocol to determine the level of fellow participation. This was determined by the attending physician on a case-by-case basis. Most procedures used nurse-administered conscious sedation. General anesthesia was used in a minority of procedures. The reason for the use of general anesthesia was not recorded for this study. Two of these cases (1%) were first attempted with conscious sedation. A sample-size calculation before the initiation of the study identified a requirement of 99 procedures per group to measure a 20% difference in mean fluoroscopy time (FT) with a power of 0.80.
Data collection Immediately after each procedure, FT, patient, and procedure-related data were recorded on a standard datacollection form. Procedure data included endoscopist, assistants, indication, procedure duration (from endoscope insertion to removal), sedation drugs and doses, and complications. In addition, the following technical components were recorded by the endoscopist as successful, failed, or not attempted: cholangiography, sphincterotomy, pancreatography, stone extraction, dilation, minor papilla, stent insertion, Billroth II anatomy, lithotripsy, cytology, manometry, pseudocyst drainage. A scoring system rated cannulation of the desired duct as easy (!5 touches), moderate (6-15 touches), or difficult (O15 touches).6 Radiation dosimetry badges were also positioned during each case to estimate exposure to (1) patients, (2) sedation nurse, and (3) endoscopist. The patient badge was placed at the bedside at the edge of the www.giejournal.org
d
The use of fluoroscopy during ERCP exposes patients and staff to ionizing radiation, but modifications in unit settings can reduce exposure times and radiation dose.
What this study adds to our knowledge d
In a prospective randomized study of 100 ERCP cases with time-limited fluoroscopy and 99 cases with standard, continuous fluoroscopy, procedure time was 16.4% lower in the time-limited group after controlling for the confounding factors.
radiation-beam field. The nurse badge was placed at the head of the patient’s bed, and the endoscopist badge was worn outside of the physician’s lead apron. These were analyzed in a blinded fashion by the university’s radiation safety department.
Statistical analysis Mean FT (and 95% confidence intervals [CI]) is expressed in seconds. Parametric data were compared by using the t test. Dichotomous variables were analyzed with the Pearson c2 test and the Fisher exact test. Simple linear regression models identified variables that predicted the FT. A 2-sided P value !.05 was considered significant. If significant interaction was found between a variable and a group assignment, an interaction term was created. Finally, a stepwise multiple linear regression analysis was performed to control for the effect of demographic and procedure-related factors on the association between the study group and the FT. Variables were used if they were significant on simple linear regression. Variables were included in the final model if the P value was !.05. All analyses were performed by using statistical software (Intercooled Stata, version 8.2; StataCorp LP, College Station, Tex).
RESULTS Patient characteristics Patients, undergoing a total of 199 procedures, were enrolled: 99 in the continuous fluoroscopy group and 100 in the ‘‘time-limited’’ fluoroscopy group (Table 1). Forty-seven percent were women. The mean age of the patients was 58.6 years. Patients in the time-limited group had a higher mean age compared with the continuous group, 62.5 years vs 54.6 years (P Z .003). Whites comprised 77% of the patient population. African Americans, Latinos, and Asian Americans accounted for 19%, 2%, and 2%, respectively. There was no significant difference in the racial composition of the groups (P Z .96). Volume 66, No. 1 : 2007 GASTROINTESTINAL ENDOSCOPY 85
Timed fluoroscopy to reduce radiation exposure during ERCP
Uradomo et al
Procedure characteristics The ERCPs were performed by 2 attending gastroenterologists. There was no significant difference in the distribution of the time-limited and the continuous fluoroscopy cases between the physicians (P Z .58). Gastroenterology fellows were involved in 98% of procedures, with no difference between the study groups (P Z .67). The vast majority of cases were performed with the patient under conscious intravenous sedation; general anesthesia was used in only 7% of cases. No difference was found in the rate of general anesthesia use between groups (P Z .79). The mean procedure duration (endoscope insertion to removal) was 39.3 minutes. There was no significant difference between groups (P Z .48). The most common technical component performed was cholangiography, performed in 89% of cases. Sphincterotomy (59%), stent placement (59%), and pancreatography (50%) were also frequently performed. Despite similar proportions of cases where each maneuver was performed, in 36 cases (18.1%), a sphincterotomy was performed without stent insertion, and, in 35 cases (17.6%), a stent was placed without performing a sphincterotomy. When comparing the 2 study groups, cytology brushing was significantly more common in the time-limited group (26.7% vs 15.2%, P Z .044). Pancreatography was performed significantly more in the continuous group (57.6% vs 42.6%, P Z .034). A trend toward more sphincterotomies was seen in the continuous group (65.7% vs 52.5%, P Z .058). Cannulation difficulty was measured on a scale according to the number of touches on the papilla required for successful cannulation. The scale ranged from easy (score, 1) to difficult (score, 3). This variable was analyzed in 2 ways. First the mean score between the 2 groups was compared. Cases in the continuous fluoroscopy group had a mean cannulation difficulty score of 1.52. Those in the time-limited group had a mean score of 1.3 (P value for difference, .026). The variable was also dichotomized by grouping moderate and difficult cannulations and comparing them with an easy cannulation. Easy cannulations were observed in 60.1% and 73.3% of cases in the continuous and time-limited groups, respectively (P Z .057).
Bivariate analyses The mean FTs were analyzed with respect to each recorded patient and procedure-related variable (Table 2). Significant predictors of FT were attending physician (P Z .038), cannulation difficulty (P Z .008), stent insertion (P Z .008), lithotripsy (P ! .001), sphincterotomy (P % .001), and total procedure duration (P ! .001). Bivariate analysis found that the fluoroscopy group was not a significant predictor of FT. The mean time was 314 seconds (95% CI 265.6–362.4) in the continuous group and 284.4 seconds (95% CI 247.1–321.6) in the time-limited group (P Z .34). Despite randomization, this finding 86 GASTROINTESTINAL ENDOSCOPY Volume 66, No. 1 : 2007
TABLE 1. Patient and procedure characteristics Group
Total subjects Mean age (95% CI), y Female, no. (%)
Continuous
Time limited
99
100
P
54.59 (50.7-58.4) 62.51 (59.1-65.9) .003 54 (54.6)
41 (41.0)
.056
6 (6.0)
7 (7.0)
.789
A
59 (48.0)
64 (52.0)
.580
B
40 (52.0)
37 (48.0)
General anesthesia, no. (%) Endoscopist, no. (%)
Cannulation difficulty, mean score
1.52
1.3
.026
Easy cannulation, no. (%)
60 (60.6)
74 (73.3)
.057
Fellow involvement, no. (%)
97 (98.0)
98 (97.0)
.667
Cholangiogram
88 (88.9)
89 (88.1)
.864
Sphincterotomy
65 (65.7)
53 (52.5)
.058
Pancreatogram
57 (57.6)
43 (42.6)
.034
Stent
54 (54.6)
63 (62.4)
.261
Stone extraction
24 (24.2)
29 (28.7)
.474
Cytology
15 (15.2)
27 (26.7)
.044
Dilation
10 (10.1)
9 (8.9)
.774
Lithotripsy
7 (7.1)
12 (11.9)
.246
Manometry
4 (4.0)
3 (3.0)
.681
Minor papilla cannulation
3 (3.0)
4 (4.0)
.720
0 (0.0)
3 (3.0)
.084
Pseudocyst drainage
0
1 (1.0)
.321
Mean procedure duration, min
38.13
40.45
.480
Intervention attempted, no. (%)
Billroth anatomy
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Timed fluoroscopy to reduce radiation exposure during ERCP
TABLE 2. Associations of patient and procedure characteristics with the mean FT
N
Mean fluoroscopy time, sec
Continuous
99
314.0
265.6362.4
Time limited
100
284.4
247.1321.6
95% CI
TABLE 2 (continued )
P
N
Mean fluoroscopy time, sec
99
305.6
266.5344.7
No
180
290.4
259.1321.7
Yes
19
381.5
264.9498.1
No
83
250.8
201.9299.6
Yes
116
333.7
295.8371.5
No
181
279.4
248.9- !.001 309.8
Yes
18
497.3
390.9603.8
No
82
234.2
193.0- !.001 275.4
Yes
117
344.6
303.4385.8
No
147
287.1
251.6322.7
Yes
52
332.9
273.9392.0
No
157
295.0
258.4331.5
Yes
42
314.5
267.7361.3
%Mean
115
187.4
168.3- !.001 206.4
OMean
84
452.1
400.5503.7
Yes
Group .337
77
339.2
289.6388.9
B
122
273.7
235.6311.9
.038
186
297.2
266.7327.7
General anesthesia
13
326.5
145.1507.8
.639
Cannulation difficulty Moderate, difficult, or failed Easy
.082
Stent
Anesthesia Moderate sedation
P
Dilation
Endoscopist A
95% CI
.008
Lithotripsy
Sphincterotomy 65
357.0
300.6413.3
134
271.0
235.7306.3
.008
Stone extraction
Sex Male Female
104
313.4
273.1353.7
95
283.5
237.2329.7
.332
Fellow involvement No fellow Fellow
.192
Cytology 5
224.4
131.3317.5
194
301.0
270.0332.0
.437
.606
Total procedure duration
Maneuver Cholangiogram No
23
270.9
174.6367.2
Yes
176
302.8
270.6335.0
100
292.7
245.8339.6
.509
Pancreatogram No
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.676
was confounded by the interaction between the group assignment and factors significantly associated with FT. Cannulation difficulty is the most notable example, showing associations with both group and FT. Sphincterotomy Volume 66, No. 1 : 2007 GASTROINTESTINAL ENDOSCOPY 87
Timed fluoroscopy to reduce radiation exposure during ERCP
TABLE 3. Independent predictors of FT during ERCP: results of a stepwise linear regression analysis Variable Time-limited fluoroscopy Procedure duration Stent placement Lithotripsy Overall model
Coefficient -51.6
P
95% CI
.029 -97.5 to -5.8
5.5
!.001
4.4-6.5
47.3
.048
147.6
!.001
66.8-228.5
69.6
.075
15.6-123.5
0.5-94.2
showed a trend toward significant association with group assignment (P Z .058).
Multivariate analysis To account for these confounders and interactions, a multiple linear regression model was created (Table 3). The model was constructed in a stepwise fashion to include all factors found to be significantly predictive of FT. Interaction terms were created for group assignment with cannulation difficulty and sphincterotomy. Factors found to be significant independent predictors of FT were group assignment (P Z .029), procedure duration (P ! .001), lithotripsy (P!.001), and stent placement (P Z.048). The regression coefficient for the use of time-limited fluoroscopy was –51.6. In other words, controlling for the variables in the model, time-limited fluoroscopy was associated with a 51.6-second (16.4%) lower mean FT.
Dose comparison Radiation dose badges were collected throughout the study period. Doses were then calculated cumulatively for each group. The average dose per procedure was nearly identical for the groups. The physician’s mean dose per case was 3.67 mrem and 4.24 mrem for the time-limited and continuous groups, respectively. Estimated nurse doses were 2.72 mrem and 2.80 mrem, whereas estimated patient doses were 50.6 mrem and 46.6 mrem. Further analysis was not performed because the dose was not calculated for each individual procedure.
DISCUSSION Physician experience, radiation-beam strength, type of fluoroscopy equipment, and shielding of patients and staff have been previously shown to impact radiation exposure.3,7-10 Intermittent or pulsed fluoroscopy is another method that substantially reduces the radiation dose without sacrificing image quality.11 A study of GI radiologic procedures found that the diagnostic acceptability of studies with fluoroscopy frame rates as low as 3.5 frames per second was statistically equivalent to those performed at 15 frames per second.12 88 GASTROINTESTINAL ENDOSCOPY Volume 66, No. 1 : 2007
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Perhaps the most readily modifiable method of reducing x-ray exposure is the reduction of the FT. A complex combination of patient- and procedure-related factors combine to determine the final FT. As expected, longer procedures and those with difficult cannulations or complex interventions were found in this study to have significantly longer FTs. On initial bivariate analysis, a significant association was not found between the time-limited setting and the FT. This negative finding can be traced to difficulty of controlling for every relevant factor that determines the FT. Despite the randomized design of the study, an uneven distribution of key variables occurred. This issue was overcome by the creation of a robust multivariate model. That analysis showed the independent FT-lowering effect of the fluoroscopy setting, with a significant (P Z .029) 51.6 seconds (16.4%) lower FT in the time-limited group. This difference is clinically meaningful as well. The average output of the fluoroscopy equipment used in this study was 1.5 rem per minute. The use of the time-limited setting could, therefore, result in a dose reduction of 1.29 rem per case or the equivalent of approximately 13 abdominal radiographs. One of the limitations of the study was that the endoscopists were not blinded to the study group assignment. Blinding was impossible, because the fluoroscopy setting is readily apparent once the activation pedal is depressed. In fact, one likely mechanism of its FT-lowering effect is that the time-limited setting functions as a reminder and a training reinforcement tool. The need to repeatedly redepress the fluoroscopy pedal can be a difficult adjustment for the endoscopist. Although this did not result in longer overall procedure times or increased failure rates, the consensus of the endoscopists was that using the time-limited setting was cumbersome. Alteration of the timer to allow for 4 or 5 seconds of fluoroscopy, rather than the arbitrarily chosen 3 seconds used in this study, would, perhaps, address this issue while still providing the reminder to limit the FT. This study also did not directly measure the dose for each procedure. Only aggregate dose data were collected. Because the unadjusted mean FT was not significantly different between groups, there was no difference in the radiation dose. All endoscopists who use fluoroscopy should strive to minimize radiation exposure during their procedures. This study shows that FT is a modifiable component in that process and proposes one method, the time-limited fluoroscopy setting, of achieving that goal.
DISCLOSURE The authors have no financial disclosures or conflicts of interest. www.giejournal.org
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REFERENCES 1. McParland B. A study of patient radiation doses in interventional radiological procedures. Br J Radiol 1998;71:175-85. 2. Buls N, Pages J, Mana F, et al. Patient and staff exposure during endoscopic retrograde cholangiopancreatography. Br J Radiol 2002;75: 435-43. 3. Chen M, Van Swearingen F, Mitchell R, et al. Radiation exposure during ERCP: effect of a protective shield. Gastrointest Endosc 1996;43:1-5. 4. Larkin C, Workman A, Wright R, et al. Radiation doses to patients during ERCP. Gastrointest Endosc 2001;53:161–114. 5. Miller DL, Balter S, Noonan PT, et al. Minimizing radiation-induced skin injury in interventional radiology procedures. Radiology 2002;225: 329-36. 6. Freeman ML, Nelson DB, Sherman S, et al. Complications of endoscopic biliary sphincterotomy. N Engl J Med 1996;335:909-19. 7. Uradomo LT, Lustberg ME, Darwin PE. Effect of physician training on fluoroscopy time during ERCP. Dig Dis Sci 2006;51:909-14. 8. Johlin F, Pelsang R, Greenleaf M. Phantom study to determine radiation exposure to medical personnel involved in ERCP fluoroscopy and its reduction through equipment and behavior modifications. Am J Gastroenterol 2002;97:893-7.
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Timed fluoroscopy to reduce radiation exposure during ERCP 9. Campbell N, Sparrow K, Fortier M, et al. Practical radiation safety and protection for the endoscopist during ERCP. Gastrointest Endosc 2002;55:552-7. 10. Cohen R, Aldred M, Paes W, et al. How safe is ERCP to the endoscopist? Surg Endosc 1997;11:615-7. 11. Martin CJ. A review of factors affecting patient doses for barium enemas and meals. Br J Radiol 2004;77:864-8. 12. Boland GWL, Murphy B, Arellano R, et al. Dose reduction in gastrointestinal and genitourinary fluoroscopy: use of grid-controlled pulsed fluoroscopy. AJR Am J Roentgenol 2000;175:1453-7.
Received August 23, 2006. Accepted October 23, 2006. Current affiliations: Division of Gastroenterology and Hepatology, University of Maryland Medical Center, Baltimore, Maryland, USA. Presented at Digestive Disease Week, May 21-24, 2006, Los Angeles, California (Gastrointest Endosc 2006;63:AB104). Reprint requests: Lance T. Uradomo, MD, Division of Gastroenterology and Hepatology, University of Maryland Medical Center, Rm N3W62, 22 South Green St, Baltimore, MD 21201.
Volume 66, No. 1 : 2007 GASTROINTESTINAL ENDOSCOPY 89