Article, Emergency Medicine

Radiation exposure in emergency physicians working in an urban ED: a prospective cohort study

Original Contribution

radiation exposure.in emergency physicians working in an urban ED: a prospective cohort study

Brent E. Gottesman MD a,?, Amy Gutman MD a,

Christopher J. Lindsell PhD a, Hollynn Larrabee MD a,b

aUniversity of Cincinnati College of Medicine, Department of Emergency Medicine, Cincinnati OH 45267-0769, USA bWest Virginia University, Robert C. Byrd Health Sciences Center, Department of Emergency Medicine, Morgantown, WV 26506, USA

Received 29 May 2009; revised 29 June 2009; accepted 29 June 2009

Abstract

Objective: The National Council on Radiation Protection (NCRP) limits health care-associated occupational exposures to radiation to 5000 mrem/y. Previous studies suggested that emergency physicians were not exposed over this limit. Their relevance to contemporary practice is unknown. We hypothesized that emergency physicians are currently exposed to radiation levels above the NCRP limits. Methods: This prospective cohort study was conducted at an urban, academic, level I trauma center emergency department (ED). Thermoluminescent dosimeter radiation badges were placed on the torso and ring finger of all physicians staffing the ED during May 2008. Thermoluminescent dosimeter badges were affixed to 8 portable phones that are carried by physicians in the ED 24 hours a day. At the end of the study period, exposure dose for each subject was estimated.

Results: Seventy-five physicians enrolled in the study; 41 residents worked a median of 94 hours and 34 attendings worked a median of 54 hours. Compliance for physician badge wearing was 99%, ring wearing was 98%, and phone wearing was 100%. Two subjects had detectable levels of radiation on their torso thermoluminescent dosimeters of 4 and 1 mrem, respectively. One phone badge had a detectable level of 1 mrem. The annual extrapolated exposure for the subject with the highest radiation level would have been 50 mrem, below the 5000 mrem exposure limit for health care workers.

Conclusion: Emergency physicians working in an urban, academic, level I trauma center ED do not appear to be at risk of exceeding the NCRP dose limits for ionizing radiation exposure to their torso or extremities.

(C) 2010

Introduction

Health care workers in emergency medicine are routinely exposed to environmental hazards, including those posed by ionizing radiation. Although modern imaging technology has revolutionized the evaluation of patients in the

* Corresponding author. Tel.: +1 513 558 5281; fax: +1 513 558 5791.

E-mail address: [email protected] (B.E. Gottesman).

emergency department (ED), it may also increase the risk of radiation exposure.

Importance

The consequences of ionizing radiation exposure can be significant; the major concerns are for development of cataracts, increased risk of cancer, and genetic defects or fetal damage within offspring of pregnant workers [1-3].

The National Council on Radiation Protection and Measurements (NCRP) has set the total body dose exposure

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limit for health care workers to 5000 mrem/y, based on equating the probability of radiation-induced cancer mortality with the annual accidental mortality rate in safe industries [3,4].

Prior research evaluating whether health care workers in the emergency department setting are exposed to radiation beyond these limits have suffered from various limitations, including small sample sizes [5,6], placing badges under protective lead garments [6], using a nonclinical scenario [7], not explicitly recording compliance [5,8], using expired thermoluminescent dosimeters (TLDs) [9], and isolating the study to trauma resuscitations [5,7,8]. More important, even the most recent of these studies was conducted 2 decades ago and the generalizability of prior studies to contemporary practice is unknown.

Significant changes in clinical practice patterns have occurred over the last 20 years. Increased use of cross- sectional computed tomography (CT) scans in lead shielded rooms has likely reduced exposure from cervical spine film radiation as physicians do not have to hold the cervical spine stable during these studies [10]. Conversely, as imaging technology has become more portable, use of plain films (especially portable radiographs) has likely increased and most areas of the ED are not lead shielded. Furthermore, many physicians do not wear lead shielding while in the ED. The goal of this study was to evaluate whether physicians practicing in the ED are currently exposed to ionizing radiation beyond the NCRP’s stated limits.

Materials and methods

Setting and study design

This prospective cohort study was approved by the institutional review board. The study was conducted in the ED of an academic, urban, level I trauma center. Annual census is approximately 85 000 patients per year, with 60 beds divided into 3 main treatment areas, a minor care area, and a shock resuscitation unit. At any given time, there are 4 or 5 residents and 2 or 3 attending physicians on duty. There is both stationary (lead shielded) and portable radiography in the ED, an on-site 32-slice lead shielded CT scanner, and an offsite MRI machine. Standard lead aprons are available in the trauma bay.

All emergency medicine attending physicians and residents assigned to the ED during May 2008 were eligible for inclusion in this study. Off-service residents and consulting physicians were excluded. Shift lengths for eligible physicians varied from 6 to 12 hours. Physicians are typically not in the CT room during studies, and no fluoroscopy machine is present in the ED. Physicians typically step away from portable x-ray machines unless they cannot leave the patient’s side, during which time a lead apron is available. Physicians set their own practice pattern as to whether they wore the apron.

Protocol and methods

Radiation exposure was quantified using standard TLD badges (Landauer Company, Glenwood, IL). Three sets of radiation exposure data were tracked: (i) resident exposure,

(ii) attending exposure, and (iii) standardized wireless telephone exposure. Each subject wore 2 badges, one on the torso at the collar or lapel and one as a ring on the finger. Residents were provided with personal torso and ring badges assigned specifically to that individual. Attending physicians wore collar and ring badges and passed the badges on to their replacement physician at the end of each shift. In addition, we attached radiation badges to all 8 ED wireless telephones that are handed off between shifts so we would have a default “24/7” exposure TLD in all clinical areas. Four control badges and one ring control were placed in a nonclinical area in a sealed box.

Study investigators were on hand to remind physicians to wear the badges at the beginning of each shift and to take them off at the end of each shift. All telephones were checked at shift changes to ensure that the badges were still attached. Badges were stored in a secure box in a nonclinical area when not in use. Unique study identification numbers were used to link badges and rings with a telephone, an attending role, or a resident.

Torso badges were designed to detect doses of 1 mrem and above [11], and ring badges were designed to detect 30 mrem and above [12]. Badges were analyzed at the end of the study month for a Cumulative dose by the Landauer Company, which is a National Voluntary Laboratory Accredited Program for quantifying radiation absorption. Measurements can be made for deep (radiation penetration up to 10 mm), eye (3 mm), and shallow (0.07 mm) tissue effective radiation; our study was designed to measure the torso badges according to the deep classification and ring badges according to the shallow classification. The deep classification corresponds to the measurements used for total exposure limits for health care workers. The primary outcome was defined as the radiation exposure of emergency medicine physicians.

Analysis

For each badge set, the measured exposure was used to derive predicted maximum radiation exposures for 1- and 4-year periods for different provider types and ED location assignments.

Results

All eligible subjects consented to participate in the study. There were 29 residents (10 PGY4, 8 PGY3, 6 PGY2, and 5 PGY1) and 34 attending physicians scheduled to work in the ED. Twelve residents who were not working in the ED during the study month were

consented in case backup coverage was used. The study lasted 29 days in May 2008, following the resident academic schedule for a spring month. Residents worked a mean of 106 hours (median, 94 hours; range, 24-186 hours) and attendings worked a mean of 58 hours (median, 54 hours; range, 12-162 hours). The maximum cumulative body or ring TLD exposure was 696 hours.

The total number of TLD badges was 46; ring TLDs was

32. During the study, no body TLDs were lost. Ten ring TLDs were lost, primarily during resuscitations. Six were replaced within 2 hours by an on-site investigator. Four rings were not replaced due to a limited ring supply. These 10 ring TLDs accounted for 142 shifts of cumulative data loss. Four body TLD changeovers were unwitnessed. None of the badges affixed to phones were lost during the study.

Compliance for physician badge wearing was 99% (531/ 535). Compliance with ring wearing was 98% (525/535). After accounting for loss of accumulated data on rings, ring compliance was 73% (393/535).

The minimum detectable radiation level for rings or control badges was 1 mrem. No control TLDs had any detectable level of radiation; 1 telephone and 2 torso TLDs did have detectable levels of radiation. The telephone carried by the PGY4 resident indicated 1-mrem exposure. One PGY3 had 1 mrem of exposure and a PGY2 had an exposure of 4 mrem. No ring TLDs had any radiation detected.

Extrapolation exposure for the subject with the highest measured dose (4 mrem) to a yearly dose would have resulted in a level of 50 mrem per year, and 200 mrem for 4 years; none of these levels exceeded NCRP standards for any health care worker, including those set for pregnant workers, at a total body dose limit of 500 mrem per mother per 9 months, or 50 mrem per month of pregnancy.

Discussion

In our busy, urban, academic trauma center ED, no emergency physician exceeded the NCRP dose limit for ionizing radiation for health care workers. The vast majority of residents (27/29, 93%) and no attending physicians (34/34 100%) had any detectable deep ionizing radiation. Further- more, of 8 phones present in the ED in clinical areas 24 hours a day, 7 days a week, 7 (87.5%) had no detectable deep ionizing radiation and one had minimal detection. This was the case even in the absence of mandatory lead protection, and without any protocol for subject positioning in relation to radiation sources.

Previous research evaluating emergency physicians’ work-related radiation exposure resulted in differing conclu- sions over the need for continuous radiation monitoring for emergency physicians [5,7,8,13,14]. Our study provides a more contemporary assessment of emergency physicians’ exposure to work-related ionizing radiation, and the design incorporated both measurements at different body locations as well as subject and work space (resident role, attending

role, phone area) specific exposures. Because measured exposure to ionizing radiation was well below the acceptable limits, the current practice at our institution of not wearing TLD badges and not requiring lead aprons for standard (excluding procedural or CT) ED radiographic studies remains justifiable.

Our results should be interpreted in light of several limitations. Placement of badges had some variability. No physician resisted wearing ring badges, but some clipped the ring to their watches. Torso badges were worn appropriately except on 4 shifts. Phones were occasionally placed in pockets. The primary unanticipated problem was loss of ring TLDs. Ring loss occurred predominantly within the context of being worn underneath gloves. With no means to recover cumulative exposure data, ring exposure data were therefore available only for 78% of the time. It is possible that in trauma resuscitation scenarios, more portable x-rays were taken than normal, and the loss of rings at these times would result in an underestimate of ionizing radiation. However, multiple times the rings were not lost in these situations and no ionizing radiation was recorded, suggesting underestima- tion is unlikely.

Another possible source of bias may have arisen from participants changing their behavior to either artificially increase or decrease their radiation exposure as a result of wearing the badges, the so-called Hawthorne effect. Subjects were not observed during their routine clinical duties so any impact is unknown. In addition, data on the wearing of lead shielding were not recorded. Lead aprons when worn would typically have covered the torso and telephone badges, which would have limited the radiation exposure. Future studies that follow a group of health care workers for longer periods, and simultaneously at multiple institutions, would overcome the study limitation of having only 1 month of data at a single institution.

Conclusions

The results of this study should reassure emergency physicians that routine activities during clinical shifts in the ED do not appear to increase the risk of receiving ionizing radiation dosages in excess of those set by the NCRP. Physicians should nonetheless remain cognizant of radiation sources to maintain minimal exposure.

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