British Journal of Radiology 75 (2002),748-753 © 2002 The British Institute of Radiology
Does cardiologist- or radiographer-operated fluoroscopy and image acquisition influence optimization of patient radiation exposure during routine coronary angiography?
W R Arthur, MBBS, MRCP
1
J Dhawan, MD, FRCP
2
M S Norell, MD, FRCP
3
A J Hunter
3 and
A L Clark, MD, MRCP
3
1 Department of Cardiology, Papworth Hospital, Cambridgeshire CB8 8RE, 2 Scunthorpe General Hospital, Scunthorpe, North Lincolnshire DN15 7BH and 3 Department of Cardiology, Castle Hill Hospital, Cottingham, East Yorkshire HU16 5JQ, UK
Correspondence: Wayne Arthur, MBBS, MRCP, Cardiology Specialist Registrar, Papworth Hospital, Papworth Everard, Cambridgeshire CB8 8RE, UK
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Abstract
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The operator of radiation exposure during coronary angiography varies between different centres. The purpose of this study was to explore whether radiation dose was lower during cardiologist- or radiographer-controlled radiation exposure and to determine if the grade of cardiologist performing angiography influenced radiation dose. Patients were randomly allocated either to cardiologist- or radiographer-controlled radiation exposure during coronary angiography. Screening time and radiation dose during fluoroscopy and image acquisition, measured by dose–area product meter, were recorded. Mean radiation dose during cardiologist-controlled radiation exposure (n=176) of 15.6 Gy cm2 (95% confidence interval (CI), 14.4–16.8) was significantly lower than that produced by the radiographer-controlled group (n=192) of 17.3 Gy cm2 (95% CI, 16.2–18.6) (p<0.044). There was no significant difference in screening times produced by the two groups of radiation exposure operators. The difference in radiation dose produced by the two operator groups was principally owing to exposure produced at image acquisition. Irrespective of radiation exposure operator, consultant cardiologists produced significantly lower screening times and radiation doses compared with registrars. During routine coronary angiography, radiographer-controlled radiation exposure does not reduce screening time or radiation dose. Senior cardiologists produce the lowest radiation doses during coronary angiography when they are responsible for radiation exposure.
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Introduction
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The EURATOM treaty governs European Community (EC) legislation on radiation protection. The most recent EC Directive (97/43/Euratom) was implemented in Great Britain on 13th May 2000. The Ionising Radiation (Medical Exposure) Regulations 2000 [1] lays down measures on health protection of individuals against the dangers of ionizing radiation in relation to medical exposure. Statutory regulations place an additional burden on cardiologists to meet and maintain the training requirements met by other health professionals routinely involved with radiation exposure.
At the core of the EC regulations is the optimization process, which ensures that radiation doses arising from exposures are kept as low as reasonably practicable. Technical advances such as digital imaging, pulse fluoroscopy and reduction of frame rates substantially reduce radiation doses [2]. However, there are no data available comparing radiation doses produced by cardiologists and radiographers when they operate X-ray equipment during routine coronary angiography. We designed a randomized, prospective single blind study to find out whether radiation exposure was lower during cardiologist- or radiographer- operated fluoroscopy and image acquisition.
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Methods
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Prior to the current study it was standard practice at Castle Hill Hospital for the radiographer to operate the foot pedal controlling radiation exposure during routine coronary angiography. The cardiologist performing coronary angiography would verbally request screening and image acquisition to commence and cease, with discretion given to the radiographer to terminate prolonged, unnecessary radiation exposure. For a 7-month period, from 1st February 2000 to 31st August 2000, patients were randomly allocated either to cardiologist- or radiographer-controlled radiation exposure. Before the study commenced, approval was obtained from the local research ethics committee. Only patients due to have routine coronary angiography of native vessels from the femoral approach were included. Written informed consent was obtained from each patient prior to the randomization procedure. Those patients who declined to consent had fluoroscopy operated by the radiographer and were excluded from further statistical analysis.
The cardiac catheterization laboratory studied is equipped with a single plane angiocardiographic system (Phillips Integris 3000; Phillips Medical Systems, Best, The Netherlands). Radiation dose is measured directly during each procedure with a dose–area product (DAP) meter (Diamentor M1; PTW, Freiburg, Germany). DAP readings were independently obtained during fluoroscopy screening and image acquisition, their sum giving the total DAP. Patient height and weight, screening time and DAP readings were recorded for each procedure. Body mass index (BMI) and body surface area (BSA) were calculated for each patient. It was also noted if a left ventriculogram or an aortogram was performed. The radiation exposure operator was registered as being either "cardiologist" or "radiographer"; the initials of the cardiologist were recorded.
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Statistical analysis
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Data were entered into a database (Microsoft Excel 97) for statistical analysis. Patient characteristics were normally distributed and these results are shown as mean (±standard deviation). Screening times and DAP readings were log normally distributed. Comparisons between groups were made with Student's t-test. One-way analysis of variance was used for sub-group analysis. Results of screening times and DAP readings are shown as geometric means with 95% confidence intervals (CIs). A p-value of <0.05 was taken to be statistically significant.
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Results
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368 coronary angiograms in total were randomized, of which 192 (52.2%) were radiographer-operated procedures. A left ventriculogram was performed in 330 (89.7%) cases and an aortogram in 17 (4.6%) cases. 13 cardiologists performed coronary angiography during the study; 6 consultants and 7 registrars in-training. Four radiographer operators of equivalent seniority and experience took part in the study. 40 (11%) coronary angiograms were randomly selected for review by a consultant cardiologist who was not part of the study and was not aware of who had controlled radiation exposure (19 radiographer, 21 cardiologist). All angiograms were of sufficient quality to be diagnostic examinations.
64.9% of patients were males. There was no significant difference in screening time between men and women; 1.77 min (95% CI, 1.61–1.94 min) for men vs 1.67 min (95% CI, 1.47–1.88 min) for women. However, men received a significantly higher radiation dose; 17.2 Gy cm2 (95% CI, 16.2–18.3 Gy cm2) for men vs 15.2 Gy cm2 (95% CI, 13.9–16.8 Gy cm2) for women (p<0.03). Average patient height was 1.69±0.1 m, and average patient weight was 81.1±14 kg. Females had a significantly higher BMI compared with males; 29.2±5.5 for females vs 27.9±4.5 for males (p<0.02). Conversely, males had a greater BSA than females; 1.99±0.15 m2 for males vs 1.77±0.17 for females (p<0.0001). There was a correlation between DAP and BMI (correlation coefficient (r)=0.45, p<0.0001) and a weaker relationship between DAP and BSA (r=0.36, p<0.0001).
Data for clinical characteristics of the patients in the radiographer- and cardiologist-controlled radiation exposure groups are shown in Table 1
. Left ventriculography was performed in 90.3% and aortography in 4.5% of the cardiologist-operated cases and in 89.1% and 4.7%, respectively, of the radiographer-operated cases. Mean screening times and mean radiation doses for coronary angiography are demonstrated in Table 2. Radiation dose in the cardiologist-controlled group was significantly lower than in the radiographer-controlled group. The shorter mean screening time during cardiologist-controlled procedures was not significant. We examined radiation dose during fluoroscopy screening and image acquisition and found that during screening there was no significant difference in radiation exposure between the two operator groups. Radiation exposure during image acquisition was higher in the radiographer-controlled group (Table 3).
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Table 1. Proportion of angiograms performed by consultant cardiologists and clinical characteristics of the patients enrolled
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Table 2. Comparison of mean screening time and mean radiation dose during radiographer- and cardiologist-controlled radiation exposure. 95% confidence intervals in parentheses
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Table 3. Analysis of constituents of total radiation exposure during radiographer- and cardiologist-operated coronary angiography (95% confidence intervals in parentheses)
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Sub-group analysis of the two operator groups was performed to examine the influence of the grade of cardiologist on screening time and radiation dose (Table 4). Consultant cardiologists performed 246 (66.8%) of the coronary angiograms and were the radiation exposure operator in 120 cases. Cardiology registrars performed the remaining 122 (33.2%) angiograms and were radiation exposure operator on 56 occasions. Irrespective of radiation exposure operator status, consultants produced significantly lower mean screening times and mean radiation doses, respectively, compared with registrars; 1.42 min (95% CI, 1.30–1.54 min) for consultants vs 2.59 min (95% CI, 2.29–2.92 min) for registrars (p<0.00001), and 14.7 Gy cm2 (95% CI, 13.8–15.6 Gy cm2) for consultants vs 20.7 Gy cm2 (95% CI, 19.1–22.5 Gy cm2) for registrars (p<0.00001). The combination of consultant cardiologist performing coronary angiography and operating fluoroscopy produced the shortest screening time and lowest radiation dose. Screening time was slightly longer when the cardiologist in-training operated fluoroscopy. Radiation dose was not significantly influenced by fluoroscopy operator status when a non-consultant performed angiography.
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Table 4. Subgroup analysis examining the effect of cardiologist grade on mean screening time and mean radiation dose during radiographer- and cardiologist-controlled radiation exposure (95% confidence intervals in parentheses)
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The average number of angiograms per cardiologist was 25±24 with a median of 12. Screening times for individual cardiologists who operated radiation exposure varied from a mean of 0.92 min (median 0.71 min) to 4.71 min (median 3.8 min) (Figure 1). When a radiographer operated radiation exposure, screening times varied for each cardiologist from a mean of 0.86 min (median 0.71 min) to 4.14 min (median 4.57 min). DAP scores for individual cardiologists varied from a mean of 11.9 Gy cm2 (median 10 Gy cm2) to 40.4 Gy cm2 (median 40.7 Gy cm2) during cardiologist-controlled radiation exposure and from a mean of 8.9 Gy cm2 (median 8.9 Gy cm2) to 27.1 Gy cm2 (median 35.9 Gy cm2) with radiographer-controlled radiation exposure.
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Figure 1. Box plot of screening times for individual operators who performed over 20 coronary angiograms. The first four operators were consultants (C1–4), and the remainder registrars in-training (R1–3). The median, 25th and 75th percentiles are shown by the boxes. Error bars are the 10th and 90th percentiles. Individual outliers are shown. Screening times are measured in minutes, therefore log[0] corresponds to 1 min screening time, log[1.0] to 10 min screening time etc.
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Seven cardiologists performed more than 20 coronary angiograms. We found no significant difference in average screening times (p<1.0) or radiation dose (p<0.8) between the two groups of radiation exposure operators (Figures 2 and 3). Mean cardiologist screening time was 1.92 min (95% CI, 1.38–2.66 min) and mean radiographer screening time was 1.92 min (95% CI, 1.33–2.76 min). Mean cardiologist radiation dose was 16.5 Gy cm2 (95% CI, 13.7–19.9 Gy cm2) and mean radiographer radiation dose was 17.2 Gy cm2 (95% CI, 13.6–21.8 Gy cm2). Non-consultants consistently produced longer screening times and higher radiation doses regardless of fluoroscopy operator status. Of note; two of three cardiologists in-training who performed more than 20 angiograms produced lower radiation doses and screening times when the radiographer was radiation operator.
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Discussion
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The effects of radiation below which the threshold level for deterministic effects occur are cumulative and permanent [3]. The new statutory regulations aim to reduce radiation doses arising from medical exposure. It is now the responsibility of the employer (each respective NHS Trust in the UK) to ensure that diagnostic reference levels measuring radiation exposure, such as DAP or screening time, are set for each radiological investigation or procedure. To ensure these requirements are met and sustained, regular clinical audit is required as part of the quality assurance programme [1].
Several terms have been defined to identify those who require specialist training. The "operator" is anyone who operates radiological equipment. Examples of operators include doctors, medical physicists and radiographers. The "practitioner" has the clinical responsibility for the exposure. The practitioner is required to have full knowledge of the potential benefit and detriment associated with the procedure under consideration. With regard to coronary angiography, the practitioner is the cardiologist. In some cases the practitioner may also undertake practical aspects of an exposure, such as fluoroscopic screening. In these circumstances the practitioner then becomes an operator [1].
The new regulations lay out details of adequate training that a practitioner or operator must have successfully completed in order to be permitted to carry out medical exposures. These include theoretical knowledge and practical experience in a number of aspects of radiation production and protection. It is the responsibility of the employer to keep, and have available for inspection, an up to date record showing the nature of training and the date on which training was completed.
The implications of the new regulations for cardiologists performing coronary angiography and other fluoroscopic procedures are two-fold. Regular clinical audit of screening times will be mandatory and further radiation training programmes will be required, perhaps on an annual basis. Adequate extra resources and supplementary time allocation will therefore be needed.
Theoretically, radiation exposure controlled by the radiographer has both positive and negative connotations. During coronary angiography the cardiologist has multiple duties to perform to safely obtain high quality images of the coronary anatomy. By giving discretion of screening time to the radiographer, prolonged inappropriate exposure by the cardiologist owing to inattention or incoordinate foot peddle activity might be avoided. Conversely, there is an inevitable delay between the cardiologist's request for screening to start and finish and the action being fulfilled by another individual. The delay in communication between the cardiologist and radiographer might cancel out any other advantage of radiographer led radiation exposure.
The overall patient radiation dose for routine coronary angiography in the Castle Hill laboratory lies towards the bottom of the range reported from other centres [4–8]. We have demonstrated that radiographer led radiation exposure during routine coronary angiography offers no advantage in lowering screening time and radiation dose. The principle finding was that radiation doses were lowest when cardiologists were responsible for radiation exposure. This finding was predominantly owing to the consultant group producing lower total DAP scores when they independently operated fluoroscopy and image acquisition. Non-consultant cardiologists in this study produced longer screening times and radiation doses than their consultant colleagues, irrespective of their status as radiation exposure operator.
It was found that cardiologist operators generated lower radiation doses at image acquisition than radiographer operators. Results were concordant with previous data demonstrating that total radiation exposure during routine coronary angiography is principally influenced by the radiation dose produced at image acquisition [8]. It was found that there was no difference between the two operator groups in radiation exposure during fluoroscopy and that the difference between the groups was owing to differences in image acquisition. Zorzetto et al [9] demonstrated that during coronary angiography 70% of radiation dose resulted from image acquisition, with the figure dropping to 48% during percutaneous transluminal coronary angioplasty. Further studies during prolonged interventional revascularization procedures, renowned for producing higher radiation doses [8, 9], might prove agreeable to radiographer-controlled radiation exposure. In the setting of routine coronary angiography, the role of the radiographer as the radiation operator is less favourable, probably owing to the summation of communication delays between cardiologist and radiographer at image acquisition.
The results of this study raise a number of concerns regarding training of cardiologists. Senior cardiologists produce the lowest radiation doses during coronary angiography when they are responsible for radiation exposure. This may be because, during their training, they were solely responsible for operation of X-ray equipment. In this study, two of three cardiologists in-training improved their screening times and radiation exposure when the radiographer took control of exposure. Both of these cardiology trainees were experienced operators approaching the latter stages of their training and likely to take senior posts in other centres where radiation exposure is solely under cardiologist control. Radiographer-controlled radiation exposure, which may be welcomed by many cardiologists and cardiologists in-training, may in fact be detrimental to radiation exposure levels in the long-term. Without adequate opportunity to operate radiation exposure, cardiologists in-training may progress to the consultant grade bypassing the learning curve necessary to reduce radiation doses. Similarly, the advantage held by present day consultant staff may be blunted in time if radiographer-controlled exposure is imposed on them. What then is the best mechanism to train cardiology registrars and maintain the performance of the consultant? Across the EC, training methods for radiation protection in the past have been disappointing and have lacked a practical component [10].
The Ionising Radiation (Protection of Persons Undergoing Medical Examinations or Treatment) Regulations (POPUMET) [11], which preceded the current EC directive and became defunct as of the 13th May 2000, included radiation training requirements. Quinn et al [12] examined radiation protection awareness in non-radiologists and found that the majority of clinicians did not receive adequate radiation protection teaching and that even if a POPUMET course had been attended overall knowledge was still poor. Practical training should be directed primarily at the registrar grade in the catheter laboratory. Moves to improve radiation safety awareness by forcing all practitioners to attend annual training courses will undoubtedly be expensive, take up valuable time and may misdirect resources to the wrong target population. Regular clinical audit of radiation doses and screening times produced by all clinical practitioners, followed by further training or retraining, may be more appropriate. Audit, for example, shows that left ventriculography adds little to the assessment of coronary disease but significantly increases radiation exposure [4, 13].
In addition to the points mentioned, training in radiation exposure is also dependent on a number of other factors, including ease of use of equipment and the baseline skills of the persons involved. Adequate provision of catheter laboratory time to allow training, as well as to provide a service, is dependent on workload, hospital setting, e.g. teaching hospital or district general hospital, and the number of laboratories in service at any one time.
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Acknowledgments
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The authors would like to thank Dr C J Brophy, Research & Development Department, Castle Hill Hospital, for statistical advice.
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Footnotes
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The work for this study was performed at the Department of Cardiology, Castle Hill Hospital, Cottingham, East Yorkshire HU16 5JQ, UK. 
Received for publication March 30, 2001.
Accepted for publication April 15, 2002.
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References
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- Statutory Instrument 2000. No 1059. The Ionising Radiation (Medical Exposure) Regulations 2000. London: HMSO, 2000.
- Aldridge HE, Chisholm RJ, Dragatakis L, Roy L. Radiation safety in the cardiac catheterization laboratory. Can J Cardiol 1997;13:459–67.[Medline]
- Johnson LW, Moore RJ, Balter S. Review of radiation safety in the cardiac catheterization laboratory. Cathet Cardiovasc Diagn 1992;25:186–90.[Medline]
- Clark AL, Brennan AG, Robertson LJ, McArthur JD. Factors affecting patient radiation exposure during routine coronary angiography in a tertiary referral centre. Br J Radiol 2000;73:184–9.[Abstract]
- Leung KC, Martin CJ. Effective doses for coronary angiography. Br J Radiol 1996;69:426–31.[Abstract/Free Full Text]
- Vañó E, González L, Fernández JM, Guibelalde E. Patient dose values in interventional radiology. Br J Radiol 1995;68:1215–20.[Abstract/Free Full Text]
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- Zorzetto M, Bernardi G, Morocutti G, Fontanelli A. Radiation exposure to patients and operators during diagnostic catheterization and coronary angioplasty. Cathet Cardiovasc Diagn 1997;40:348–51.[Medline]
- Leppek R, Klose KJ, Habermehl A, Ziegler A. Status of radiation protection courses for physicians—plea for a change in paradigm. Z Arztl Fortbild (Jena) 1996;90:414–22.
- Statutory Instrument 1988. No 778. The Ionising Radiation (Protection of Persons Undergoing Medical Examinations or Treatment) Regulations. London: HMSO, 1988.
- Quinn AD, Taylor CG, Sabharwal T, Sikdar T. Radiation protection awareness in non-radiologists. Br J Radiol 1997;70:102–6.[Abstract]
- Khan MA, Sinha S, Hayton S, Fynn S, Henderson RA, Bennett DH. A normal electrocardiogram precludes the need for left ventriculography in the assessment of coronary artery disease. Heart 1998;79:262–7.[Abstract/Free Full Text]
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Abstract
Introduction
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