British Journal of Radiology (2003) 76, 653-655
© 2003 British Institute of Radiology
doi: 10.1259/bjr/29454996
Do radiologists' radiation-related opinions predict their fluoroscopy doses?
T Vehmas, MD
Department of Radiology, Helsinki University and Radiology Unit, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, FIN-00250 Helsinki, Finland
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Abstract
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The influence of radiologists' radiation-related opinions to fluoroscopy doses was studied. Dose–area products (DAP), screening times and the number of exposures per patient were recorded in 528 barium enema examinations performed by 23 residents (14 female, 9 male). The residents' scored opinions (on the general radiation risk in radiology, the importance of radiation protection in radiology and their estimate of their own dose level on which they operate when compared with their colleagues) were correlated with these radiation variables. Residents' opinion on the importance of radiation protection correlated positively with screening time (r=0.402, p=0.008) and with DAP (r=0.333, p=0.028). The female residents (score 8.3) considered radiation protection more important than the males (score 7.4, p=0.029). The stability of these opinions was suggested by finding them not to correlate with residents' age or radiological experience. Residents could not reliably estimate their true dose levels, which were compared with the estimated dose levels. Fluoroscopy behaviour and doses seem to be affected by psychological factors. Further psychologically oriented studies might assist in revealing such factors and in developing proper teaching methods for radiologists to control their doses.
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Introduction
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Although the use of traditional contrast studies under fluoroscopy has been declining owing to modern sectional imaging and other alternative diagnostic modalities, interventional radiology increasingly uses fluoroscopic techniques. In a large, comprehensive tertiary medical care centre serving more than 340 000 patients in 1997, angiographic procedures contributed 42% and other fluoroscopy 5% to collective effective dose equivalent [1]. Fluoroscopy exposes both the patients, radiologists and sometimes even assistants to radiation. Radiation protection has traditionally been regarded as a technical matter and optimizing the equipment [2–4] and use of innovations such as pulsed fluoroscopy [5] have been recommended. The need to standardize the technique in barium examinations has been recognised because of a large variation in doses [6], and special training of residents and senior radiologists has been suggested [7]. However, a previous study indicated no dose reducing benefit from attending general radiation protection lectures [8].
Personality traits of the radiologist may play a role in explaining the wide variation in radiologists' use of fluoroscopy. Factors influencing radiation behaviour need to be known in order to guide radiologists properly and to control doses. This study aims to correlate radiologists' radiation-related opinions with their fluoroscopy doses. This is an extension of a previous study investigating the influence of radiologists' sex and training on fluoroscopy doses [8].
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Materials and methods
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23 radiology residents (14 female, 9 male, age 26–40 years) performed 528 double contrast barium enemas, 2 to 33 studies each (mean 23). The residents participated in the study as a part of their training in gastrointestinal radiology. The patients (336 female, 192 male, mean age 62 years) examined over a 2 year period were unselected and represented both hospital in-patients and out-patients. They were studied for various gastrointestinal symptoms. Shimadzu fluoroscopy equipment (Shimadzu, Kyoto, Japan) with an undercouch tube was used in all cases. The radiographs were inspected usually under supervision of a senior radiologist to decide whether the images were of sufficient quality or whether further fluoroscopy and extra images were needed.
Screening times on the Shimadzu control panel were recorded and dose–area products (DAP) were measured with a DAP meter (DAP-S Model 841-S; Gammex-RMI Inc., Middleton, USA). The number of images exposed with the fluoroscopy device was recorded.
Before the study, the residents were asked to give their opinion on
- the general radiation risk in radiology, 0 indicating no risk and 1 indicating extreme risk
- the importance of radiation protection in radiology, 0 indicating no importance and 1 indicating extreme importance
- the radiation dose they generally use in radiological work when compared with their colleagues, 0 indicating the lowest radiation dose and 1 indicating the highest radiation dose
These opinions were evaluated by using a linear analogue scale 56 mm long. The residents were asked to mark a point on a line. The distance was then measured and adjusted so that the opinions of the resident could be expressed on a scale from 0 to 10. Mean screening times, DAPs and the number of exposures per patient were computed for each radiologist. Female and male radiologists were compared with respect to their screening times, DAPs, the number of exposures per patient, and with respect to the above three opinions by using the Mann–Whitney U-test. The radiation-related variables and the opinions were correlated with each other by using the Kendall tau correlation.
The opinions were also correlated with the residents' age and radiological experience. The relative contribution (r2=coefficient of determination) of fluoroscopy time and the number of exposures to DAP were computed by using linear regression after the logarithmic transformation of DAP. SPSS 10.0 software (SPSS Inc., Milwaukee, IL) was used.
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Results
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Female residents used more radiation in terms of both DAP, screening time and the number of radiographs per patient (Table 1
) [8]. However, they considered the radiation risk greater, estimated their own use of radiation greater and judged the radiation protection more important than males did. The last item was significantly different (p=0.029) between sexes. Radiologists' opinion on the importance of radiation protection correlated significantly with screening times and with DAP (Table 2). Residents could not estimate their use of radiation when compared with their colleagues.
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Table 2. Correlations (Kendall's tau) between radiation-related variables and radiologists' opinions. Correlation coefficients (normal lettering) and corresponding p-values (in italics)
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Both the number of exposures per patient and the screening time correlated strongly with DAP (p<0.001), as expected, because they are its major determinants. Screening time contributed 57% and the number of exposures 55% of the variance in DAP. Their combined effect was 68%. The first two also correlated strongly with each other (p<0.001) indicating that radiologists who expose a great number of images in each examination also tend to have longer fluoroscopy times.
Correlations between residents' age and radiation-related opinions (risk: r=0.255, p=0.098; protection: r=0.203, p=0.191; own estimated dose: r=-0.004, p=0.979) as well as radiological experience and opinions (r=0.232, p=0.125; r=0.133, p=0.382; r=-0.109, p=0.474, respectively) were not significant.
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Discussion
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The present study found positive associations between radiologists' radiation-related opinions and their doses, a fact not previously reported.
The results should be regarded as preliminary due to the small size of the sample studied. The primary study [8] found several patient-related factors which influenced dose-related variables: patient's anteroposterior thickness, age and the radiological diagnosis. These factors were not included in the present analysis because averaged data (including several patient's colon examinations) were used for each resident. The residents' age or radiological experience seemed to have no straightforward influence on doses in the primary study and could also be omitted in the present analyses. Simple bivariate correlations could consequently be used in this study. There was no equipment-related biasing factor in doses, because all residents used the same basic fluoroscopy equipment. The system had no special dose saving options and thus no scope for technology driven dose reduction. The variation in the residents' mean dose-related variables is likely to be due to their personal screening technique possibly related to psychological factors. Both screening time and the number of exposures contributed almost equally to DAP.
This positive correlation between doses and the estimated hazard in radiology was not expected. Surprisingly, it was found that radiologists well aware of the radiation risks would use the highest doses, not the lowest. Strong recognition of radiation hazard may be associated with personality traits such as carefulness and conscientiousness. Such radiologists might also use more fluoroscopy than others to make their radiological diagnoses as sure as possible. Female residents estimated the radiation risk generally higher than males did, although there was a considerable variation within sexes. Females also operated on higher dose levels than males did.
There was little if any correlation between residents' own estimation on their radiation use and the measured radiation variables. This indicates that radiologists are not able to estimate their own doses. Even those who use high fluoroscopy doses may do so unrecognised and are not able to optimize their technique without external intervention. Radiologists' doses should therefore be measured in departments with a heavy fluoroscopy load.
Radiologists' doses and their estimation of radiation risk did not show any significant mutual relationship either. The estimated risk and the importance of radiation protection showed a positive correlation, however. These two findings are difficult to explain.
Radiation opinions did not correlate significantly with residents' age or radiological experience. This may indicate that these opinions and possibly all radiation behaviour are relatively constant with time. Adult personality traits show little change with age [9], especially after the age of 30 years [10]. Radiologists who tend to operate with high doses may continue this practise. During a long period, such a radiologist will harm both himself/herself and the patients. The extra collective dose from excess fluoroscopy delivered to patients during a career of decades should be cut down.
Changing behaviour is usually difficult and the optimal intervention to reduce doses may not yet have been found. The best teaching method may also have to address the role that personality plays in radiation protection. Psychological tests may help to clarify personality traits behind radiation behaviour in order to develop proper teaching methods for radiologists to reduce their doses.
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Acknowledgments
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I wish to thank the residents and the departmental staff for co-operation as well as Dr Taina Autti and Dr Katariina Luoma for their valuable comments.
Received for publication November 22, 2002.
Revision received May 29, 2003.
Accepted for publication June 10, 2003.
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References
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Abstract
Introduction
