Introduction
As in human medicine, diagnostic fluoroscopy is used to continuously visualize dynamic processes of internal structures, such as the gastrointestinal and respiratory tracts, in veterinary patients and to record static images of these processes.1,2,3 An x-ray tube operator's radiation exposure is usually higher for diagnostic fluoroscopic procedures than for diagnostic radiographic procedures because, during fluoroscopy, the operator stands closer to the primary beam and the patient (a source of scattered x-rays) and the exposure times are longer.1 Interventional fluoroscopy involves the use of fluoroscopic imaging to guide small instruments, such as catheters, stents, and guidewires, through blood vessels or other body orifices and is primarily used in veterinary medicine for therapeutic purposes.4,5,6 Compared with noninterventional fluoroscopy, interventional fluoroscopy has an even greater potential for high radiation exposure to operators. Because interventional fluoroscopic procedures are complex and the number of static images needed for the medical record is often large, the duration of the procedures is prolonged; moreover, the hands of the operators are in close proximity to or at times within the primary beam. Additionally, the required level of image detail may be high, necessitating use of higher current settings. In combination, these factors result in high radiation exposure among operators during interventional fluoroscopy.6,7
Interventional fluoroscopy has several potential advantages over invasive surgical procedures, including shorter hospitalization times, lower postoperative morbidity and mortality rates, reduced procedure-related pain, and, for some disease conditions, improved outcomes.4,8 The types of interventional fluoroscopic procedures and the number of workers performing these procedures are rapidly increasing in veterinary medicine.9,10.11 As a result, exposure of veterinary workers to ionizing radiation is also increasing. There are limited reports regarding operator radiation doses during veterinary fluoroscopic procedures. Median effective radiation doses per procedure of 4.93 µSv for residents and 3.46 µSv for faculty during interventional cardiological procedures performed on dogs and cats have been reported.a Procedure duration and radiation dose (determined from patient dose reports) were examined in another study12 of 360 fluoroscopic procedures on dogs and cats. The median duration of fluoroscopic procedures ranged from 1.6 minutes for orthopedic procedures to 35.8 minutes for vascular procedures, and the median patient dose ranged from 2.27 mGy for orthopedic procedures to 137 mGy for vascular procedures. Although the operator dose from scatter radiation is lower than the radiation dose received by a patient, operator dose is quantitatively related to patient dose,13 which further supports a relationship of veterinary interventional fluoroscopy with the potential for high occupational radiation doses. A study14 of worker exposure during equine fluoroscopic procedures revealed that radiation exposure to the operator during carpal joint examination was 25 to 40 times the exposure during a comparable radiographic examination, and that annual radiation exposure for operators was more than twice the recommended dose limit. On a per-procedure basis, dose ranges (measured on the outside of personal protective shielding) to operators (excluding cardiologists) performing interventional fluoroscopy on human patients are reported to be 19 to 800 µSv at eye level, 6 to 1,180 µSv at neck level, 2 to 1,600 µSv at trunk level, and 30 to 5,800 µSv at hand level.15 The radiation exposure of operators performing interventional cardiological procedures on humans is typically near the annual occupational effective dose limit of 20 mSv recommended by the ICRP.16 The equivalent doses to an operator performing 100 cardiac angioplasty procedures are estimated to be 86 mSv to the eye and head region and 301 mSv to the extremity region, with an estimated whole-body effective dose of 14 mSv.16
The potential for high occupational radiation doses to veterinarians performing fluoroscopy raises concern for the harmful effects associated with long-term radiation exposures. Compared with findings for workers who do not perform fluoroscopically guided procedures in human patients, the risks of stochastic effects (which are risks at any radiation dose) and deterministic effects (for which a threshold dose must be reached before there is a risk) in workers who do perform such procedures are elevated.17 An increased incidence of cancer, which is a stochastic effect, has been reported for workers involved in fluoroscopically guided interventional procedures in humans.13,17,18 Heritable effects are another stochastic risk of ionizing radiation exposure.19 Deterministic effects reported for workers performing interventional fluoroscopy in human medicine include increased risk of cardiovascular effects20,21and cataracts.22,23
Given the growing number of conditions treated with interventional fluoroscopy in veterinary medicine, the potential for high radiation doses to operators, particularly during interventional fluoroscopic procedures, is a concern. The cumulative radiation dose over an operator's career and the known risks associated with that exposure, as well as optimal radiation safety practices of veterinarians performing these procedures, are important considerations. The objective of the cross-sectional survey study reported here was to describe the radiation safety behaviors of veterinary specialists and residents performing fluoroscopic procedures, including the frequency of use of personal protective equipment. Potential risk factors for these radiation safety behaviors, including knowledge of radiation risk, employer requirement that workers wear personal protective equipment, and training regarding machine operating parameters, were also investigated.
Materials and Methods
This study was approved by the University of Saskatchewan Behavioral Ethics Board (BEH ID 1580). An electronic questionnaire developed in web-based softwareb was distributed to ACVIM cardiology diplo-mates (n = 362) and residents (106), ACVIM small animal internal medicine diplomates (1,531) and residents (358), ACVR diplomates (725) and residents (218), and ACVS diplomates (763) and residents (211). The questionnaire was designed to investigate radiation safety behaviors, including frequency of personal protective equipment use and knowledge of ionizing radiation risks. The study invitation and questionnaire link were distributed to ACVIM cardiology, ACVIM small animal internal medicine, and ACVR members through the professional colleges' electronic diplomate and resident mailing lists. For ACVS diplomates and residents, the invitation and link were distributed through their Facebook groups because an electronic mailing list was not available. The initial invitation was followed with a reminder after 1 week. The survey was open for completion between December 2019 and January 2020.
Questionnaire
The questionnaire was developed by all authors. The questionnaire (Supplementary Appendix S1) initially asked respondents whether they had been the operator of an x-ray unit during a small animal fluoroscopic procedure in the preceding year, and only respondents who answered yes were able to complete the remainder of the questionnaire. Respondents were asked to complete the survey only one time. Respondents were asked how often they were involved in small animal fluoroscopic procedures, what type of fluoroscopic procedures they performed (percentage of their time spent on cardiac, gastrointestinal, hepatobiliary, orthopedic, respiratory, urinary, vascular, or other procedures), the location of the viewing monitor relative to their position during the procedure, what personal protective equipment their employer required them to wear (lead apron, thyroid shield, gloves, or eyeglasses), and for which body locations they had been assigned a personal dose monitoring device (dosimeter). Respondents were asked how often they wore an apron, thyroid shield, gloves, eyeglasses, body dosimeter, and ring dosimeter and how often they used radiation-attenuating hand cream or a lead shielding curtain during the x-ray exposure period (response options were always, > 75% of the time, between 50% and 75% of the time, < 50% of the time, or never). Respondents were also asked what type of gloves (0.5-mm lead equivalent radiology gloves or radiation-attenuating surgical gloves) and eyeglasses (with or without side shielding) they used, whether they used a dosimeter to estimate radiation dose to the eyes, and the percentage of procedures in which an unshielded body part (eg, fingers) was visible on an acquired image. Respondents were then asked whether they had received formal training regarding fluoroscopy machine operating parameters in relation to radiation exposure, and how often they adjusted those operating parameters during procedures to reduce their radiation dose. Respondents were also asked to describe their knowledge of the risks of ionizing radiation and the annual occupational dose limits for the whole body and lens of the eye recommended by the ICRP. Respondents were asked to state whether they knew their last reported whole-body and lens doses and if they believed that radiation exposure increases the risk of cancer and cataracts. Finally, respondents were asked to select the 3 most important reasons for not wearing eyeglasses during a fluoroscopic procedure, with reason 1 being most important and reason 3 being least important; respondents who did wear eyeglasses during all procedures were not asked this question. Eight reasons were provided as response options: eyeglasses interfere with performing my task, eyeglasses are uncomfortable to wear, wearing eyeglasses is not required by my employer, there are not enough pairs of eyeglasses for all workers, I am not concerned about the adverse health effects of ionizing radiation, my coworkers do not wear eyeglasses during fluoroscopic procedures, eyeglasses are unhygienic, and eyeglasses do not fit properly.
Data analyses
All data analyses were completed by an analytical epidemiologist (CLW) using commercial software.c Examined radiation safety outcomes included frequency of use of personal protective equipment (gloves and eyeglasses), lead shielding curtain, and dosimeters (ring and body) and frequency of adjusting machine operating parameters to reduce radiation exposure. Potential risk factors considered for radiation safety outcomes were respondents' knowledge of radiation risk (self-assessments and ability to correctly identify ICRP-recommended dose limits), employer requirement that workers wear personal protective equipment, belief that radiation exposure can cause cataracts, professional college affiliation (ACVIM cardiology, ACVIM small animal internal medicine, ACVR, or ACVS), resident versus diplomate, age (≤ 45 years vs > 45 years), gender, practice type (private vs academic), and country (US vs Canada). The age categories ≤ 45 years and > 45 years were used for the analysis because there were 0 respondents in the age category of 18 to 24 years and 1 respondent in the age category of > 65 years. Countries other than the US and Canada were not included in the analysis because the 14 respondents who selected the response of other country were from 6 countries. Training regarding machine operating parameters in relation to radiation exposure was only considered as a risk factor for frequency of adjusting machine operating parameters to reduce radiation dose. The effect of risk factors on frequency of apron and thyroid shield use was not examined in the analysis because > 95% of respondents always wore these types of shielding. As well, belief that radiation causes cancer was not considered as a risk factor in the analysis because > 95% of respondents believed that radiation causes cancer.
The respective associations between risk factors of interest and frequency outcomes were assessed by means of appropriate nonparametric tests because each of those outcomes was reported on a 5-point ordinal scale. The Kruskal-Wallis test was used with post hoc protected Wilcoxon rank sum tests to identify significant pairwise comparisons. Outcomes were then recoded into 3 groups (never, inconsistent, and always), and multivariable ordinal logistic regression models were built by means of stepwise, manual, backward elimination to identify final models and account for potential confounders. Interactions were not examined. Only variables with a value of P ≤ 0.10 in the nonparametric analysis were considered in building the final model. In the remaining analyses, a value of P ≤ 0.05 was considered significant.
Results
The electronic questionnaire was distributed to 4,274 potential study participants; there were 240 respondents (overall survey response rate, 6%). By professional college and certification, the response rates were as follows: ACVIM cardiology, 18% (86/468 invitees); ACVR, 10% (95/943 invitees); ACVIM small animal internal medicine, 2% (39/1,889 invitees); and ACVS, 2% (20/974 invitees). Three respondents reported board certification in both ACVIM cardiology and ACVIM small animal internal medicine; these 3 persons were categorized as ACVIM cardiology respondents. Of the 240 persons who agreed to participate in the survey, 43 (18%) had not operated an x-ray unit during a small animal fluoroscopic procedure in the preceding year; the questionnaire for those participants was terminated after the first question. The other 197 (82%) persons who agreed to participate in the survey had operated an x-ray unit for a small animal fluoroscopic procedure in the preceding year; these persons completed the remainder of the questionnaire. Characteristics of these 197 workers were summarized (Table 1). Not all respondents completed every question; therefore, the denominator for some reported percentages was < 197.
Characteristics of members of the ACVIM cardiology subspecialty, ACVIM small animal internal medicine sub-specialty, ACVR, and ACVS who completed a questionnaire regarding radiation safety practices during small animal fluoroscopic procedures (n = 197 respondents).
| Characteristic | No. of respondents (%) |
|---|---|
| Professional college* | |
| ACVIM cardiology | 79 (42) |
| ACVIM small animal internal medicine | 28 (15) |
| ACVIM cardiology and small animal internal medicine | 3 (2) |
| ACVR | 69 (36) |
| ACVS | 14 (7) |
| Position† | |
| Diplomate | 145 (75) |
| Resident | 48 (25) |
| Practice type | |
| Private practice | 88 (45) |
| Academic institution | 108 (55) |
| Other | 1 (< 1) |
| Gender | |
| Female | 117 (59) |
| Male | 77 (39) |
| Prefer not to say and other | 3 (2) |
| Age (y) | |
| 24–44 | 144 (73) |
| 45–65 | 51 (26) |
| > 65 | 2 (l) |
| Country | |
| US | 160 (81) |
| Canada | 23 (12) |
| Other | 14 (7) |
The 3 persons who reported board certification in both ACVIM cardiology and ACVIM small animal internal medicine were included as ACVIM cardiology respondents for purposes of subsequent data analysis.
Four participants indicated that they were neither a diplomate nor a resident or did not select a professional college; therefore, the number of respondents in this category was 193.
Among the 197 respondents, 41 (21%) were involved as an operator in < 1 fluoroscopic procedure/ mo, 119 (60%) were involved as an operator in 1 to 4 fluoroscopic procedures/mo, 35 (18%) were involved as an operator in 5 to 10 fluoroscopic procedures/ mo, 1 (< 1%) was involved as an operator in 11 to 15 fluoroscopic procedures/mo, 1 (< 1%) was involved as an operator in 16 to 20 fluoroscopic procedures/ mo, and no workers were involved as an operator in > 20 fluoroscopic procedures/mo. The percentages of time spent on different types of fluoroscopic procedures for all respondents and for members of each professional college were summarized (Table 2). One hundred ninety-three respondents provided information regarding the location of the viewing monitor relative to the operator of the fluoroscopic unit; monitor positioning was immediately in front for 48 (25%) respondents, at an angle of 45° for 123 (64%) respondents, and at an angle of 90° for 22 (11%) respondents. With regard to personal protective equipment that their employer required them to wear, 194 of 197 respondents were required to wear an apron during fluoroscopic procedures, 190 (96%) were required to wear a thyroid shield, 55 (28%) were required to wear gloves, and 49 (25%) were required to wear eyeglasses. Frequencies of use of personal protective equipment (apron, gloves, thyroid shield, and eyeglasses), use of a mobile or fixed lead shielding curtain, and presence of an unshielded body part in at least 1 acquired image/ procedure were summarized (Table 3).
Percentage of time that operators spent performing different small animal fluoroscopic procedures reported by ACVIM, ACVR, and ACVS diplomates and residents.
| Procedure types | All respondents (n = 193) | ACVIM cardiology (n = 82) | ACVIM small animal internal medicine (n = 28) | ACVR (n = 69) | ACVS (n = 14) |
|---|---|---|---|---|---|
| Cardiac | 42 | 95 | 3 | 2 | < 1 |
| Gastrointestinal | 16 | < 1 | 12 | 39 | 0 |
| Hepatobiliary* | 2 | 2 | 2 | < 1 | 7 |
| Orthopedic | 6 | 0 | 0 | 2 | 65 |
| Respiratory | 17 | 1 | 23 | 36 | 7 |
| Urinary | 15 | < 1 | 58 | 17 | 14 |
| Vascular | 1 | < 1 | 2 | 1 | < 1 |
| Other | 1 | < 1 | < 1 | 2 | 6 |
Includes portocaval shunt attenuation.
Frequency of shielding use and other radiation safety behaviors during small animal fluoroscopic procedures reported by 197 ACVIM, ACVR, and ACVS diplomates and residents.
| Type of shielding or behavior | Frequency | Item not available | ||||
|---|---|---|---|---|---|---|
| Always | > 75% | 50%-75% | < 50% | Never | ||
| Wearing apron | 197 (100) | 0 | 0 | 0 | 0 | 0 |
| Wearing thyroid shield | 191 (97) | 5 (3) | 0 | 0 | 1 (< 1) | 0 |
| Wearing gloves | 39 (20) | 10 (5) | 4 (2) | 27 (14) | 95 (48) | 22 (11) |
| Wearing eyeglasses | 41 (21) | 11 (6) | 7 (4) | 19 (10) | 79 (40) | 40 (20) |
| Use of lead curtain* | 26 (13) | 4 (2) | 7 (4) | 20 (10) | 76 (39) | 64 (32) |
| Body part in primary beam | 4 (2) | 0 | 2 (1) | 63 (32) | 128 (65) | — |
| Adjustment of machine operating parameters† | 48 (24) | 24 (12) | 31 (16) | 39 (20) | 55 (28) | — |
| Wearing whole-body dosimeter | 162 (82) | 18 (9) | 3 (2) | 4 (2) | 5 (3) | 5 (3) |
| Wearing extremity dosimeter | 105 (53) | 19 (10) | 2 (1) | 8 (4) | 19 (10) | 44 (22) |
Data are reported as the number (percentage) of respondents unless otherwise indicated.
Participants were asked how often they use a lead shielding curtain (fixed or mobile) during the period of x-ray exposure.
Participants were asked how often they adjusted the operating parameters on the fluoroscopy machine for the purpose of reducing their radiation exposure.
— = Not applicable.
Among the 197 respondents, 129 (65%) never wore radiation-attenuating hand cream during x-ray exposure, 1 (< 1%) always wore radiation-attenuating hand cream, and 67 (34%) did not have radiation-attenuating hand cream available. Eighty respondents had gloves available and at times wore gloves. These 80 respondents reported using radiology (gauntlet-type) gloves 87% of the time and radiation-attenuating surgical gloves 13% of the time. Of the 77 respondents who had eyeglasses available and at times wore eyeglasses, 58 (75%) most often used eyeglasses without lead side shielding, and 19 (25%) most often used eyeglasses with lead side shielding.
One hundred twenty-six (64%) respondents were assigned a whole-body dosimeter, 66 (34%) were assigned a thyroid dosimeter, and 138 (70%) were assigned an extremity dosimeter. Frequencies of whole-body and extremity dosimeter use were summarized (Table 3). Eleven percent (22/197) of respondents used a dosimeter to estimate the annual equivalent dose to their eyes, 74% (146/197) did not use a dosimeter to estimate the annual equivalent eye dose, and 15% (29/197) did not know if a dosimeter was used to estimate their annual equivalent eye dose.
Among the 197 respondents, 98 (50%) had and 99 (50%) had not received formal training at their hospital regarding fluoroscopy machine operating parameters that could be adjusted to reduce radiation exposure. One hundred forty-two (72%) respondents reported that at times they adjusted the fluoroscopy machine operating parameters for the purpose of reducing their radiation exposure. Frequency of machine operating parameter adjustment was summarized (Table 3). Of these 142 respondents, 49 (35%) adjusted pulse rate frequency (number of pulses per second), 78 (55%) adjusted frame-rate frequency (frame rate per second), 126 (89%) adjusted collimation, and 33 (23%) adjusted tube current (mA) or tube voltage (kV) settings or both.
Knowledge of personal radiation dose and radiation risks was summarized (Table 4). The annual occupational effective radiation dose limit (averaged over 5 years) recommended by the ICRP was correctly identified by 41 of 197 (21%) respondents. The annual occupational equivalent radiation dose limit for the lens of the eye recommended by the ICRP was correctly identified by 15 of 197 (8%) respondents. The most important reasons respondents selected for not wearing eyeglasses during fluoroscopic procedures were summarized (Table 5).
Knowledge of personal radiation dose and radiation risks reported by ACVIM, ACVR, and ACVS diplomates and residents who participate in small animal fluoroscopic procedures.
| Question | No. of respondents (%) |
|---|---|
| How would you rate your knowledge of the risks of ionizing radiation (n = 197)? | |
| Excellent | 45 (23) |
| Good | 93 (47) |
| Fair | 46 (23) |
| Poor | 13 (7) |
| Do you know your last reported whole-body effective dose from occupational radiation exposure (n = 197)? | |
| Yes, I know my exact reported dose | 19 (10) |
| I have a rough idea of my last reported dose | 33 (17) |
| I do not know, but I know how to look it up easily | 76 (39) |
| I do not know, and I don't know how to look it up easily | 42 (21) |
| I don't receive reports on my whole-body effective dose | 27 (14) |
| Do you know your last reported equivalent dose to the lens of your eye from occupational radiation exposure (n = 196)? | |
| Yes, I know my exact reported dose | 4 (2) |
| I have a rough idea of my last reported dose | 4 (2) |
| I do not know, but I know how to look it up easily | 31 (16) |
| I do not know, and I don't know how to look it up easily | 42 (21) |
| I don't receive reports on the equivalent dose to the lens of my eye | 115 (59) |
| Do you believe that radiation exposure increases the risk of cancer (n = 196)? | |
| Yes | 190 (97) |
| No | 3 (2) |
| I don't know | 3 (2) |
| Do you believe that radiation exposure increases the risk of cataracts (n = 197)? | |
| Yes | 175 (89) |
| 0 (0) | |
| I don't know | 22 (11) |
The 3 most important reasons (with reason 1 being the most important and reason 3 being the least important) that radiation-attenuating eyeglasses were not worn when operating a fluoroscopic unit* reported by ACVIM, ACVR, and ACVS diplo-mates and residents who participate in small animal fluoroscopic procedures.
| Reason | Response option | No. of respondents who selected the response option |
|---|---|---|
| 1 (n = 76 respondents) | Eyeglasses are not required by my employer | 29 |
| Eyeglasses are uncomfortable or do not fit properly | 17 | |
| Eyeglasses interfere with performing my task | 16 | |
| Not enough eyeglasses for all workers | 6 | |
| I am not concerned about the adverse health effects | 5 | |
| 2 (n = 60 respondents) | Eyeglasses are uncomfortable or do not fit properly | 19 |
| Eyeglasses interfere with performing my task | 10 | |
| Not enough eyeglasses for all workers | 10 | |
| Eyeglasses are not required by my employer | 9 | |
| My coworkers do not wear eyeglasses | 8 | |
| 3 (n = 52 respondents) | Eyeglasses are uncomfortable or do not fit properly | 20 |
| My coworkers do not wear eyeglasses | 8 | |
| Not enough eyeglasses for all workers | 7 | |
| Eyeglasses are not required by my employer | 7 | |
| Eyeglasses interfere with performing my task | 6 |
This question was presented to 116 of 197 respondents; respondents who always wore eyeglasses (n = 40) or who did not have eyeglasses available (41) were not asked this question. Only reasons selected by 5 or more respondents are shown.
Factors associated with radiation safety behaviors
Unconditional associations between risk factors of interest and frequency of radiation safety behaviors were assessed (Supplementary Table S1). The final multivariable model of the associations was generated (Table 6).
Final multivariable model of the associations between risk factors of interest and frequency of radiation safety behaviors reported by 197 ACVIM, ACVR, and ACVS diplomates and residents who participate in small animal fluoroscopic procedures.
| Variable | OR | 95% CI | P value | ||
|---|---|---|---|---|---|
| Use of gloves | |||||
| Employer requirement that shielding be worn (vs no requirement) | 28 | 9.5–84 | < 0.001 | ||
| Professional college* | |||||
| ACVIM cardiology | Reference category | ||||
| ACVIM small animal internal medicine | 8.6 | 1.6–46 | 0.013 | ||
| ACVR | 108 | 21–573 | < 0.001 | ||
| ACVS | 9.9 | 1.5–67 | 0.019 | ||
| Use of eyeglasses | |||||
| Employer requirement that shielding be worn (vs no requirement) | 29 | 13–65 | < 0.001 | ||
| Lead curtain use | |||||
| Correctly identified ICRP-recommended annual occupational effective dose limit (vs not correctly identified) | 4.4 | 1.9–9.9 | < 0.001 | ||
| Professional college* | |||||
| ACVIM cardiology | Reference category | ||||
| ACVIM small animal internal medicine | 1.5 | 0.49–4.6 | 0.49 | ||
| ACVR | 4.2 | 1.8–9.9 | 0.001 | ||
| ACVS | 0.81 | 0.14–4.6 | 0.81 | ||
| Body dosimeter use | |||||
| Professional college* | |||||
| ACVIM cardiology | Reference category | ||||
| ACVIM small animal internal medicine | 0.43 | 0.15–1.2 | 0.12 | ||
| ACVR | 2.5 | 0.75–8.1 | 0.14 | ||
| ACVS | 0.11 | 0.03–0.39 | 0.001 | ||
| Ring dosimeter use | |||||
| Self-reported knowledge of radiation risk | |||||
| Poor | Reference category | ||||
| Fair | 2.1 | 0.56–7.9 | 0.27 | ||
| Good | 4.2 | 1.2–14 | 0.02 | ||
| Excellent | 8.2 | 2.0–34 | 0.004 | ||
| Country (Canada vs US) | 0.27 | 0.10–0.78 | 0.02 | ||
| Adjustment of machine operating parameters to reduce radiation dose | |||||
| Trained with regard to machine operating parameters (vs not trained) | 2.69 | 1.59–4.54 | < 0.001 | ||
| Diplomate (vs resident) | 2.43 | 1.31–4.51 | 0.005 | ||
| Professional college* | |||||
| ACVIM cardiology | Reference category | ||||
| ACVIM small animal internal medicine | 0.59 | 0.27–1.28 | 0.18 | ||
| ACVR | 0.56 | 0.31–1.01 | 0.054 | ||
| ACVS | 0.18 | 0.06–0.53 | 0.002 |
See Table 1 for key.
The final multivariable analysis revealed that during small animal fluoroscopic procedures, respondents wore gloves significantly more frequently if their employer required that gloves be worn (OR, 28 [95% CI, 9.5 to 84]), compared with frequency of glove wearing by respondents whose employer did not require that gloves be worn. Members of ACVIM small animal internal medicine, ACVR, and ACVS wore gloves significantly more frequently than did members of ACVIM cardiology (OR, 8.6 [95% CI, 1.6 to 46], 108 [95% CI, 21 to 573], and 9.9 [95% CI, 1.5 to 67], respectively [Table 6]).
Respondents wore eyeglasses significantly more frequently if their employer required that eyeglasses be worn (OR, 29 [95% CI, 13 to 65]), compared with the frequency of eyeglasses wearing by respondents whose employer did not require that eyeglasses be worn. Respondents who correctly identified the ICRP-recommended annual occupational effective dose limit used a lead curtain significantly more frequently (OR, 4.4 [95% CI, 1.9 to 9.9]), compared with respondents who did not correctly identify the ICRP-recommended annual occupational effective dose limit. Members of the ACVR used a lead curtain significantly more frequently than members of the ACVIM cardiology sub-specialty (OR, 4.2 [95% CI, 1.8 to 9.9]).
Members of the ACVS wore a body dosimeter significantly less frequently than members of the ACVIM cardiology subspecialty (OR, 0.11 [95% CI, 0.03 to 0.39]). Compared with respondents who rated their knowledge of radiation risks as poor, respondents who rated their knowledge of radiation risks as good or excellent wore a ring dosimeter significantly more frequently (OR, 4.2 [95% CI, 1.2 to 14] and 8.2 [95% CI, 2.0 to 34], respectively). Respondents working in Canada wore a ring dosimeter significantly less frequently than those working in the US (OR, 0.27 [95% CI, 0.10 to 0.78]).
Respondents who had received training regarding machine operating parameters adjusted those parameters to reduce their dose during procedures significantly more frequently than respondents who had not received similar training (OR, 2.7 [95% CI, 1.59 to 4.54]). Board-certified specialists adjusted machine operating parameters to reduce their radiation dose during procedures significantly more frequently than residents (OR, 2.4 [95% CI, 1.31 to 4.51]). Members of the ACVS adjusted machine operating parameters to reduce their dose during procedures significantly less frequently than members of the ACVIM cardiology subspecialty (OR, 0.18 [95% CI, 0.06 to 0.53]).
Discussion
To the authors' knowledge, self-reported radiation safety behaviors among veterinary board-certified specialists and residents performing small animal fluoroscopic procedures have not been previously examined. Despite the potential for high radiation doses received by the operator associated with fluoroscopic procedures, the survey of the present report identified that the usage frequency of hand and eye protection and other radiation dose–reducing practices among the respondents was suboptimal.
The radiation dose received by operators during fluoroscopic procedures can be substantially reduced by use of shielding; lead curtains, aprons, and thyroid shields can reduce the radiation dose to specific body regions by 85% to > 99%, depending on the lead equivalence of the shielding and incident xray energy.7 In the present study, the questionnaire responses indicated that use of aprons and thyroid shields among respondents was optimal. Although operators' hands may receive a radiation dose that is much higher than that received by their trunks,15 hand shielding was not consistently used by the respondents in the present study. Gauntlet-type gloves are not suitable for interventional procedures when fine manipulation of equipment and sterile conditions are needed; however, use of flexible radiation-attenuating gloves or radiation-attenuating hand cream has been reported to reduce scatter radiation dose to the hands by 25% to 70%.24 Possible reasons for the low frequency of use of any type of gloves by operators in the present study included lack of awareness of the hand shielding options available, belief that hand shielding is not needed because of high occupational dose limits for extremities, or concern that radiation-attenuating gloves interfere with the ability to perform procedures. The need for a high level of dexterity and tactile sensation during interventional cardiac procedures was likely a reason for the finding that respondents in all other specialties were significantly more likely to use gloves than were cardiologists. Operators who do not wear hand shielding for this reason could consider application of a radiation-attenuating cream to their hands prior to donning surgical gloves. A commercially available bismuth oxide cream reduces radiation dose by approximately 40% and does not interfere with tactile sensitivity or ability to perform interventional cardiac procedures.25 Given that approximately a third of the respondents in the present study reported placing a body part in the primary x-ray beam at times, it is important to emphasize that hand shielding is designed to reduce an operator's dose of scatter radiation and that the level of attenuation will be reduced when hands are exposed to the higher-energy primary beam.
Eye shielding also attenuates scatter radiation to a variable degree, although the reduction in dose depends on fit and shape of the eyewear and angle of exposure.26 Only 25% of respondents in the present study viewed procedures on a monitor located straight in front of them. During fluoroscopic procedures, the radiation dose to the eyes may be reduced if the head is turned to the side relative to the source of radiation because the sides of leaded eyeglasses do not attenuate radiation as effectively as does the front. The percentage of operators in the present study who always wore eye shielding during fluoroscopic procedures was higher than findings among operators performing diagnostic radiography27,28; however, the overall frequency of eye shielding use in the present study was suboptimal, and 20% of respondents did not have access to eye shielding. The top reasons for not wearing eyeglasses given by respondents included the recognized problems of poor fit and interference with performance of tasks; it is recommended that workers try on different types of eyeglasses prior to purchase to ensure comfort and good fit.26 In the present study, a requirement by employers that eye (or hand) shielding be worn was reflected in its greater use; respondents who reported that their employer required them to use the shielding were approximately 28 times as likely to do so as were respondents who reported that their employer did not require them to use the shielding.
Seventy-one percent of the study respondents reported that they never used a lead curtain or did not have one available for use. The ICRP recommends use of radiation shielding screens wherever feasible to reduce operator exposure.7 The present study revealed that lead curtains were used significantly more frequently by radiologists than by cardiologists. This may have been related to differences in procedures performed by these 2 types of operators; interventional cardiac procedures require the operator to be in closer proximity to the patient. A lightweight, disposable, sterile shield placed on the patient significantly reduces the radiation dose to human cardiologists29 and could be considered for veterinary interventional fluoroscopic procedures for which use of mobile or mounted lead screens is not feasible.
Although shielding effectively reduces an operator's radiation dose, shielding cannot protect all parts of an operator's body; hence, other measures for radiation dose reduction are important. Machine operating parameters that can be adjusted to reduce operator dose include but are not limited to pulse rate, frame rate, beam collimation, and tube voltage and current. Appropriate manipulation of these operating parameters can dramatically reduce operators' radiation dose16,30; however, more than a quarter of the study respondents never adjusted machine operating parameters to reduce their radiation dose. Use of pulsed fluoroscopy, wherein the beam is composed of a series of short x-ray pulses, may reduce operator dose by > 50%, depending on the method used to achieve the pulsed mode.16,30 In a study12 of fluoroscopic procedures at 2 veterinary institutions, median radiation exposures for any given median dynamic fluoroscopy time (the time spent obtaining a series of images during a procedure) at the institution that performed most procedures with a continuous mode were higher, compared with data for the institution that used only a pulsed mode. A lower frame rate (the number of images recorded per second) will also reduce operator dose but can compromise image quality.16 The lowest frame rate needed to achieve the diagnostic or therapeutic intent of the procedure should be used. Because scatter radiation increases linearly with increasing field size, the x-ray beam should be collimated to the smallest size needed to provide the required image.7 Reduction of tube voltage and current to the lowest settings that would provide an adequate image for the purpose of the procedure rather than an image of optimal quality will also reduce operator dose.16 In the present study, 89% of respondents who adjusted machine operating parameters reduced the field size to reduce their radiation dose; however, the other operating parameters were modified less frequently. Diplomates were twice as likely as residents to adjust machine operating parameters to reduce their radiation dose, possibly because of more training and experience with maximizing dose reduction while achieving acceptable image quality for the purpose of the procedure. Results of the present study indicated that machine operating parameters were adjusted to reduce radiation dose significantly more frequently if respondents had received training on how to do so; this type of training is a potentially modifiable factor that could be implemented to reduce operator radiation exposure at all veterinary workplaces where fluoroscopy is performed.
The ICRP recommends that a person's level of training in radiological protection be commensurate with that person's use of radiation; however, veterinary fluoroscopy is increasingly performed by nonradiologists, who may have minimal to no formal training in radiological protection.6,7,12 Although the ACVR radiology qualifying examination study guide includes principles of radiation physics, radiation biology, and radiation protection, no mention of these topics could be found by the authors in the residency training requirements available for other veterinary specialties, including cardiology, small animal internal medicine, and small animal surgery. Trainees likely receive some level of radiation safety orientation during their residencies, but there does not appear to be a formal requirement or examination of this knowledge other than for radiology trainees. Radiation safety training and increased awareness of factors influencing radiation dose have the potential to reduce operator radiation exposure through behavior modification.31,32 In the present study, 2 measures of respondent knowledge about radiation safety, namely correct identification of the ICRP-recommended annual effective dose and self-reported knowledge of radiation risk, were associated with improved radiation safety behaviors (frequency of lead curtain and ring dosimeter use). On the basis of the study finding of suboptimal radiation safety practices among veterinary fluoroscopy users, the authors recommend formal incorporation of radiation safety into residency training programs, particularly for the specialties performing interventional fluoroscopic procedures.
In the present study, examination of behaviors to reduce operator radiation exposure was limited to use of personal shielding and adjustment of machine operating parameters. However, there are many other measures that operators can implement to reduce their radiation exposure, including choice of fluoros-copy system.a Sampling bias was introduced when members of the ACVS were invited to participate by a method (Facebook groups) that differed from the invitation process for the other professional colleges; this was unavoidable because an electronic mail list was not available for ACVS members. This alternative invitation method likely contributed to the low response rate for ACVS members. Nonresponse bias, in which people who participate in a study systematically differ from people who do not respond, is more likely when response rates are very low, such as for members of the ACVIM small animal internal medicine subspecialty and ACVS in the present study. As with any self-reported safety behavior study, there was the potential for response bias; selective suppression of information about suboptimal radiation safety behaviors by respondents may have resulted in an underestimation of behaviors that increase radiation doses to workers. As well, the surveyed population included specialists who perform a wide variety of fluoroscopic procedures, and the effect of procedure on the differences in findings among members of the 4 professional colleges could not be assessed.
Supplementary Materials
Supplementary materials are available online at: avmajournals.avma.org/doi/suppl/10.2460/javma.259.5.518.
Acknowledgments
This research was supported with funds from WorkSafeBC through the Innovation at Work Program.
The views, findings, opinions, and conclusions expressed herein do not represent the views of WorkSafeBC.
Footnotes
Pierce KV, Scansen BA, Maddox N. Real-time dosimetry monitoring in the interventional catheterization laboratory (abstr). J Vet Intern Med 2020;34:2861.
SurveyMonkey Enterprise, Ottawa, ON, Canada.
Stata SE, version 16, StataCorp, College Station, Tex.
Abbreviations
| ACVIM | American College of Veterinary Internal Medicine |
| ACVR | American College of Veterinary Radiology |
| ACVS | American College of Veterinary Surgery |
| ICRP | International Commission on Radiological Protection |
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