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Time of day influences patient radiation exposure from percutaneous cardiac interventions

¹ Department of Cardiology, Klinik Fraenkische Schweiz, Feuersteinstr. 2, D-91320 Ebermannstadt, ² Department of Cardiology, Ernst Moritz Arndt University, Friedrich-Loeffler Str. 23, 17487 Greifswald, and ³ Institute for Computer Sciences, Biometry and Epidemiology, Friedrich Alexander University Erlangen-Nuernberg, Waldstr. 6, 91054 Erlangen, Germany

Correspondence: Dr Eberhard Kuon, Klinik Fraenkische Schweiz, Feuersteinstr. 2, D-91320 Ebermannstadt, Germany

	Abstract

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The objective of this study was to investigate the influence of time of day on patient radiation exposure due to cardiac interventions. The elective interventional workload of one experienced cardiologist documented over the course of 4 months amounted to 325 diagnostic catheterizations and 145 percutaneous coronary interventions (PCI). All radiation parameters documented during diagnostic coronary angiography remained constant throughout the entire day. In contrast, for PCI measurements made from 7:00 a.m. to 1:00 p.m., our study revealed a mean overall dose–area product (DAP) of 11.8±6.8 Gy cm² (n=115). These radiation exposure levels increased significantly later in the afternoon (n=30) by 28% to a level of 15.0±11.1 Gy cm² (p<0.045). Cinegraphic DAP increased from 3.7±2.7 Gy cm² to 5.0±3.2 Gy cm² (p<0.033). The number of cinegraphic runs and frames rose from 7.9±2.9 to 9.1±3.1 (p<0.025), and from 136±63 to 164±70 (p<0.014), respectively. The following conclusion is warranted by our data and should now be confirmed in a wider multicentre study: radiation protection of the patients could be influenced by the fatigue of the cardiologist conducting the procedure. To enhance patient radiation safety, elective percutaneous angioplasty should be scheduled for the first 6 h of the interventionalist's occupational workload. Diagnostic interventions may be safely scheduled later.

	Introduction

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It is of course undisputed that radiation protection for patients in cardiac catheterization laboratories is a matter of primary concern. Modern coronary angiography and percutaneous transluminal coronary angioplasty (PTCA), as currently performed, induce mean patient dose–area products (DAPs) of 57±31 Gy cm² and 80±39 Gy cm² [1–6], equivalent to effective doses of 11.4±6.2 mSv and 16.0±7.8 mSv, respectively [1, 7]. The relevance of this exposure is evident from the fact that an effective dose of 1 mSv is equivalent to 20–50 chest X-rays [8]. No investigation, however, has been conducted on the effects on patient radiation exposure from workload-related fatigue, which may indeed be considerable, among interventional cardiologists in high-volume laboratories. The goal of this study was to assess the influence of the time of day on patient radiation exposure owing to elective diagnostic as well as interventional cardiac catheterizations.

	Methods, patients and materials

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The elective interventional workload of one experienced cardiologist documented here, performed in the form of femoral access over the course of 4 months, amounted to 325 diagnostic catheterizations and 145 percutaneous coronary interventions (PCI). A single-arm Integris H3000 undercouch tube and overcouch intensifier system (Philips Medical Systems, Eindhoven, The Netherlands) was used. All interventions entailed selection of the lowest of three grid-controlled fluoroscopy modes, with 0.4 mm copper filter and 1.5 mm aluminium filter installed in the X-ray beam. The DAP was measured by an ionization Diamentor (M2; PTW, Freiburg, Germany), calibrated in situ on the X-ray tube (reliability for repetition <3%; total uncertainty for linearity (60–150 kV) <5%). Table attenuation was equivalent to 0.6 mm aluminium. Calibration factors at 70–90 kV were 1.10 for direct lateral exposures and 0.97 for undercouch exposures perpendicular to the couch. The electrical charge generated by the X-ray beam is directly proportional to the collimated radiation beam passing the cross-sectional chamber area and the patient's body surface area. We measured the total dose–area product (DAP) from cinematography (DAP^C) and fluoroscopy (DAP^F), the number of cinegraphic runs and frames, as well as fluoroscopic time. DAP^C frame^-1 and DAP^F s^-1 were calculated to indicate the quality of localization of the radiation beam to the coronary region of interest by using movable lateral lead blinds.

We compared retrospectively the parameters of all elective interventions performed between 7:00 a.m. and 1:00 p.m., with the parameters of those performed later in the afternoon. The experienced interventional cardiologist was not informed that his radiation exposure data would be subsequently analyzed according to time of day. Emergency interventions were excluded, since they entail significantly higher radiation exposure, as recently reported [9]. We based statistical comparison of the two samples of the continuously measured parameters on Student's t-test, in cases in which distribution of the parameters in both groups demonstrated normal distribution with equal variance. Normality was checked by the Shapiro–Wilk test and homoscedasticity, by a conventional F-test. In cases of heteroscedasticity, the Welch–Satterthwaite t-test was employed insofar as data from both groups still met the normality assumption. For non-normal samples, the Wilcoxon–Mann–Whitney test was employed instead as a non-parametric alternative to the t-tests. Our reports of p-values describe the results of statistical testing; we considered those results lower than 0.05 to be statistically significant. All statistical computations were performed using the SAS statistical package, Version 8.2 (SAS Institute Inc., Cary, NC).

	Results

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All radiation parameters documented during diagnostic coronary angiography remained constant throughout the documented day (Table 1). In contrast, patient radiation exposure due to PCI significantly increased after an interventional workload of 6 h: the mean overall DAP by 28%, and the cinegraphic DAP by 34%. The number of cinegraphic runs and frames during this period rose by 15% and 20%, respectively. In addition, fluoroscopic DAP^F s^-1 and cinegraphic DAP^C frame^-1, both additional indicators of effective localization of the beam to the region of interest by using lateral lead blinds, slightly increased, by 19% and 16%, respectively. This finding, however, did not attain a level of statistical significance (Table 1). Age and sex of the patients were comparable for the respective study groups, and body mass index did not increase throughout the afternoon (Table 1). The levels of cinegraphic contribution to radiation exposure for coronary angiography and PTCA were 62% and 32%, respectively.

	Discussion

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Low framing speed, self-surveillance by electronic radiation dosimeters, rotational coronary angiography, and not least consistent followship training have all proved beneficial in the context of patient dose reduction [10–13]. In the present study, improvements based on recently published insights and consistent radiation reduction techniques [9, 14] enabled mean DAPs from coronary angiography and PCI well below other reported levels [1–6]. This was possible through reduction of fluoroscopy time and above all, of cinegraphic frames for coronary angiography, from the range of 1000–2300 as typically reported [5], to approximately 150–200 (Table 1) [9, 14]. Digital documentation of short cinegraphic loops of one heart cycle length, repeated as often as necessary, accordingly provides comparable picture quality and adequate visual impressions, but undoubtedly challenges the operator's concentration.

Prior to our study there had been no investigations or publications on the influence of intervention time of day on patient radiation exposure. None of the relevant radiation parameters relating to diagnostic interventions performed by an experienced operator was influenced by the length of time that the interventionalist had worked. Our retrospective investigation is the first study, however, to demonstrate a significant and noteworthy increase of radiation exposure to patients from PCIs as a result of intervention performed later than 1:00 p.m. It is unlikely that variation in either interventional complexity or radiation-intensive X-ray projections influenced patients' DAP, since, over the course of the day, the operator performed his interventional workload in random order and did not change his standard and favourite angulations for diagnostic and interventional tasks.

Our result can accordingly be interpreted as an effect of interventionalist occupational fatigue after performing continuous PCIs for more than the equivalent of 6 h; a workload not exceptional in high-volume catheterization laboratories. Greater exposure results from significantly higher DAP^C due to significantly longer cinegraphic runs and in turn, more frames (Table 1). Since the consistency of implementation of radiation-reducing techniques in performing coronary interventions depends upon the operator's care and concentration, a fatigue effect in the afternoon will more readily become apparent for coronary interventions. These are, indeed, typically more complex and accordingly more tiring to the operator than routinely performed coronary angiographies. For obvious reason, this fatigue effect might well be absent in departments with less optimized procedures.

The following conclusion is warranted by our data, and should now be confirmed in a wider multicentre study: "To enhance patient radiation safety, elective percutaneous angioplasty should be scheduled for the first 6 h of the interventionalist's occupational workload. Diagnostic interventions may be safely scheduled later."

Received for publication May 16, 2002. Revision received September 9, 2002. Accepted for publication January 23, 2003.

	References

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1. Betsou S, Efstathopoulos EP, Katritsis D, Faulkner K, Panayiotakis G. Patient radiation doses during cardiac catheterization procedures. Br J Radiol 1998;71:634–9.[Abstract]
2. 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]
3. Cusma JT, Bell MR, Wondrow MA, Taubel JP, Holmes DR Jr. Real-time measurement of radiation exposure to patients during diagnostic coronary angiography and percutaneous interventional procedures. J Am Coll Cardiol 1999;33:427–35.[Abstract/Free Full Text]
4. Fransson SG, Persliden J. Patient radiation exposure during coronary angiography and intervention. Acta Radiol 2000;41:142–4.[CrossRef][Medline]
5. Lobotessi H, Karoussou A, Neofotistou V, Louisi A, Tsapaki V. Effective dose to a patient undergoing coronary angiography. Radiat Prot Dosim 2001;94:173–6.[Abstract]
6. Van de Putte S, Verhaegen F, Taeymans Y, Thierens H. Correlation of patient skin doses in cardiac interventional radiology with dose-area product. Br J Radiol 2000;73:504–13.[Abstract]
7. Leung KC, Martin CJ. Effective doses for coronary angiography. Br J Radiol 1996;69:426–31.[Abstract]
8. Announcement to the German Parliament by the German Federal Ministry for Environment, Natural Conservation, and Nuclear Safety, dated 10 September 2001; Letter No 14/6905:30.
9. Kuon E, Dahm JB. Variablen der Patienten-Strahlenexposition invasiver Verfahren: Diagnostik, PTCA, Laserangioplastie und Rotablation. Analyse 1929 koronarer Interventionen an 1550 Patienten. Z Kardiol 1999;88(Suppl. 2):22.
10. Steffenino G, Rossetti V, Ribichini F, Dellavalle A, Garbarino M, Cerati R, et al. Short communication: staff dose reduction during coronary angiography using low framing speed. Br J Radiol 1996;69:860–4.[Abstract]
11. Kuon E, Niederst PN, Dahm JB. Usefulness of rotational spin for coronary angiography in patients with advanced renal insufficiency. Am J Cardiol 2002;90:369–73.[CrossRef][Medline]
12. Coulden R, Readman LP. Coronary angiography: an analysis of radiographic practice in the UK. Br J Radiol 1993;66:327–33.[Abstract]
13. Kuon E, Dahm JB. Effective training in radiation attenuating techniques requires long-term cardiology fellowship supervision. Eur J Allied Health 2002;3:20–5.
14. Kuon E, Schmitt M, Dahm JB. Significant reduction of radiation exposure to operator and staff during cardiac interventions by analysis of radiation leakage and improved lead shielding. Am J Cardiol 2002;89:44–9.[CrossRef][Medline]

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