Brennan, Patrick

D'helft, Catherine

Hughes, Ciara

Mc Gee, Alison

McFadden, Sonyia

Rainford, Louise

Winder, J. R.

English

Ulster University's Research Portal

A SURVEY OF RADIATION DOSE AND IMAGE OPTIMISATION FOR CARDIAC INTERVENTIONAL PROCEDURES A collaborative study between University College Dublin, Ireland and the University of Ulster at Jordanstown, Belfast.C. D’helft, S. Mc Fadden, A. McGee, L. Rainford, C. Hughes, J. Winder & P. Brennan. Part funded by The Health Research Board, Dublin. PURPOSEThis study outlines a proposed investigation to establish local and national x-ray dose reference levels for cardiology examinations.  and produce This will provide a benchmark in Irish Cardiovascular centres against which individual performance can be judged.  This will and hence encourage centres to take corrective action if deemed necessary. The study also aims to determine methods of reducing the radiation dose for given interventional cardiology procedures, whilst maintaining image quality and diagnostic efficacy of examinations. The project involves collaboration between University College Dublin, University of Ulster at Jordanstown and hospitals throughout the island of Ireland. It is part funded by the Health Research Board (HRB).Ireland has the highest rate of heart disease in Europe, accounting for 42% of all deaths [1]. Interventional cardiology procedures are recognised as an important component of healthcare given the high incidence of cardiovascular disease in this country. The number of patients referred for interventional cardiology procedures has increased in recent years as a result of the cost-effectiveness of these techniques relative to the surgical alternative of invasive surgical procedures [2]. Patients undergoing interventional techniques can be treated as outpatients or day-cases, requiring a reduced hospital stay compared with surgical candidates.  The advantages of reduced cost, increased patient throughput and fewer complications have driven the increased need for various interventional cardiology procedures worldwide.All x-ray examinations represent a biological risk proportional to the radiation dose delivered to an individual [3]. Radiation doses should therefore be kept as low as reasonably achievable, consistent with good diagnostic image quality. The potential for high patient doses, and variability both within and between cardiac imaging centres during cardiac interventional procedures have already been  identified [4]. Radiation dose optimisation and standardisation of practice have become critically important, representing an essential component of any health strategy aimed at improving the quality of health care provision. Due to the involvement of prolonged fluoroscopic exposure times, interventional procedures, particularly cardiovascular studies, are often responsible for some of the highest patient and staff radiation doses experienced in diagnostic radiology [5]. Such exposures increase the risk of stochastic radiation effects (cancer), and regularly cross the threshold dose, above which direct, deterministic effects such as erythema, epilation and ulceration are experienced by the patient [6]. It has been estimated that in the UK, interventional cardiology studies are responsible annually for a collective effective dose of 914 manSieverts [7] and deterministic effects involving the skin such as tissue desquamation, ulceration and necrosis, sometimes requiring skin graft therapy are being increasingly reported [8, 9]. Based on data collected in a preliminary survey performed for this study, and data available in other countries, it is estimated that the Republic of Ireland’s population of about 4 million will undergo a minimum of 15,000 cardiac interventional examinations per year, resulting in an annual collective dose of about 165 manSieverts.  Recent HRB-funded work and other studies [10] have identified major causal agents responsible for high radiation doses in non-interventional fluoroscopy and have established cost-effective methods of reducing patient dose for non-fluoroscopic work [11]. These methods include increasing tube potential, variable FFD, patient positioning and tube filtration [11, 12]. If similar dose reducing methods can be established for interventional cardiology, reduction in terms of manSieverts may be substantial.  This project aims to provide a framework both nationally and globally for patient dose optimisation during interventional cardiovascular examinations. Through cross-border collaboration, “diagnostic reference levels” for cardiac interventional procedures that truly reflect national clinical practice in the field of cardiac imaging will be proposed. To date no such reference dose levels have been established in this country for cardiac interventional radiological procedures despite these being required under current legislation [13]. In the UK, implementation of diagnostic reference levels for general radiography and non-interventional fluoroscopic examinations has been shown to contribute at least in part to a radiation exposure reduction of up to 45% [14]. Dose reductions of this magnitude would substantially reduce the risk of cancer induction, and minimise, deterministic radiation effects, thereby offering important benefits for patients and cardiological staff. The Department of Health and Children’s strategy is to provide a healthcare system, which ensures equity, quality and accountability, the fulfilment of which requires evidence-based research in order to define best practice. National Reference Doses	Reference doses were first identified by in 1990 by NRPB and the Royal College of Radiologists (RCR) [15]. The aim was to indicate abnormally high doses for common examinations by using the third-quartile of the distributions of the mean doses for a particular examination.	The International Commission on Radiological Protection (ICRP) also used the concept of reference doses but referred to them as “Diagnostic Reference Levels” (DRL’s) which should be calculated by professional medical bodies [16].	The DRL has been recommended by the UK Institute of Physics and Engineering in Medicine Report 88 [17] and implemented as a requirement in hospitals by the Ionising Radiation (Medical Exposure) Regulations IR(ME)R [18]. 	DRL’S are - Defined as dose levels in medical radiodiagnostic practices to patients of standard-sized groups or standard phantoms, for typical examinations.They act as an indicator of patient dose that can be used as a benchmark to prevent excessive exposure.	Currently no set Diagnostic Reference Levels.-	Required by law – Council Directive 97/43/EURATOM [19]	EU legislation (97 / 43 / EURATOM) [19]:Incorporated into Irish law;S.I. 478 of 2002. European Communities (Medical Ionising Radiation Protection) Regulations 2002. [13]Aims 	To quantify the ionising radiation exposure to patients during common interventional cardiology procedures- namely; Coronary angiograms, Percutaneous coronary intervention & Pacemaker insertions  	To compare these radiation dose levels with nationally established Diagnostic Reference Levels (DRL’s) for other x-ray examinations as stipulated by the National Radiation Protection Board (NRPB), UK [20].Risks	Average effective dose for angiography- 6 mSv	Risk of fatal cancer from 6 mSv only 1 in 3,300	Approx 14,100 angiography procedures, 1,200 pacemaker insertions in Ireland per annum 	Statistically almost 5 people in Ireland develop cancer following these procedures every yearLIFETIME CANCER MORTALITY FROM X-RAY RADIATION[21] The Linear No-Threshold (LNT) Debate.Threshold Doses*	500 mGy - impairment of haemopoiesis.*	2,000mGy - erythema.*	2,000mGy - cataract formation.*	7,000mGy - permanent epilation.*	10,000-12,000mGy - skin atrophy with telangiectasia.[22] VANO*	Direct deterministic effects associated with cardiac interventional procedures are well documented in literature.[5,6]U.S. figures Percutaneous transluminal coronary angioplasty (PTCA)608,000 procedures per year in U.S. (1997)effective (whole-body) dose per procedure 5.0  1.9 mSvCardiac catheterization, coronary arteriography & angiography (CA)may include ventriculography, left- and/or right-heart studies3,870,000 procedures per year in U.S. (1997)effective (whole-body) dose per procedure 3.1  1.3 mSv [23]METHODS & MATERIALSProcedural data and radiation levels are being determined and compared for coronary angiograms (CA), percutaneous coronary intervention (PCI) and permanent pacemaker insertion procedures (PPI). Other factors such as*	Patient data.*	Grade of cardiologist.*	Projections acquired/technique. *	Eequipment used*	Complexity score for all examinations. [4,24] *	Exposure factors:kVp / mA / Fluoroscopic exposure time / Length of cine run / Single and Biplane options / DAP meter reading are also recordedDose measurements from dose-area product meters will be collated from participating centres in the Republic of Ireland and Northern Ireland. Work practices for the examinations will be recorded and techniques associated with low radiation dose and acceptable/high image quality will be identified. From the information gathered diagnostic reference levels will be established. Following this initial study, a series of experimental dose reducing studies using tissue equivalent anthropomorphic phantoms and psychophysical tests will be performed. Cost-effective, dose-reducing measures will be introduced both singularly and in combination, and both radiation dose and image quality levels will be measured. Based on the results of this experimental work, proposed optimum practice for each interventional examination will be tested. It is anticipated that data provided by this study will result in optimised techniques for cardiovascular interventional procedures, and will benefit the large numbers of patients in Ireland and elsewhere undergoing interventional cardiology procedures.Steps*	Retrospective study.*	Pilot study.*	QA tests.*	Data collection & analysis.*	Image quality tests.*	Set DRLs.*	Implement findings in clinical departments.RESULTSTo Date, the results demonstrate a mean dose for CA procedures 7,426cGycm2, for PCI procedures 10,744cGycm2, for PPI procedures 3,705cGycm2.However large intra and inter hospital variations were noted. The time varied by a procedure specific extent and shows a strong relationship with radiation dose delivered; there are also other causal agents being investigated which account for some variation in the DAP readings.RETROSPECTIVE STUDY RESULTS:  DAP METER READINGS &FLUOROSCOPY TIMES*	CA:*	 Average: 		7,426cGycm²				8.7 mins. *	 Range:		1,899cGycm² -17,930cGycm² 	2 - 15.5 mins.*	PCI:*	Average:		10,744cGycm² 			15 mins. *	Range:		2,848 cGycm² - 126,252cGycm² 	3.9 - 47.9 mins.*	PPI: *	Average:		3,705cGycm²				8.7 mins.*	Range:		356 cGycm2 - 24,294cGycm²		1.1 - 43.1 mins. 	*	Fluoroscopy time was a key determinant of radiation dose variation.COMPARISON OF REFERENCE LEVELSProcedures:	CA	PTCADAP (cGycm²)Study (avg)	5700*7426	9400*10744Screening time (Min)Study (avg)	6*8.7	16*15*Values as proposed by the DIMOND EU PROJECT [25]Study findingsClose correlations were noted between Screening time, Complexity and their effect on the DAP readings- lower complexity and reduced time procedures had lower DAP readings.There was however some variation on the effect that the grade of the operator & patient BMI had on the DAP.Some possible Confounders were also noted procedures with increased complexity were performed by a higher grade of operator, also procedures with a variable number of projections/devices used also have  their effect on the DAP of the procedure.PILOT STUDY:    CA ResultsPILOT STUDY:  PCI ResultsPILOT STUDY:  PI ResultsCONCLUSIONDue to the risks associated with X-ray exposure radiation doses should be kept as low as reasonably achievable, consistent with good image quality. However significant variations in radiation dose and image quality for coronary interventional procedures have been shown within and between hospitals in Ireland for the first time. This all Ireland study aims to further explore radiation dose levels for cardiac interventional procedures in 15 hospitals, possible areas of standardisation and potential Diagnostic Reference Levels will be proposed. A wide range of x-ray doses were recorded for interventional cardiology procedures. National or local reference dose levels need to be established and implemented for these high-risk procedures.Best current practice must be identified Through experimental dose reduction strategies “optimised practice” can be established for each procedure allowing DRLs to be established and reduce radiation doses.The ALARA principle will be adhered to consistent with optimal image quality allowing us to address the lack of standardisation which can be seen during these proceduresFurther developments*	Quality assurance tests*	Data collection:*	16 hospitals;*	Approx. 120 patients per hospital*	Data analysis.*	Estimate DRL’s.*	Image quality evaluation:*	Phantom trails;-Clinical trials.REFERENCES1. Irish health.com. Heart disease- facts and figures. http://www.irishhealth.com/clin/cholesterol/chol-facts.html (​http:​/​​/​www.irishhealth.com​/​clin​/​cholesterol​/​chol-facts.html​) (date accessed)2. Faulkner K, Vano E (2001). Deterministic Effects in Interventional Radiology. Radiat Prot Dosim; 94(1-2), 95-98.  3. Lindell B (1996). The risk philosophy of radiation protection. Radiat Prot Dosim, 157-163.4. Bernardi G, Padovani R, Morocutti G, Vano E, et al (2000). Clinical and Technical Determinants of the Complexity of Percutaneous Transluminal Coronary Angioplasty: Analysis in relation to radiation exposure. Catheterization and Cardiovascular Interventions; 51, 1-9.5. Vano E, Gonzalez L, Fernandez JM, Guibelalde E (1995). Patient dose values in interventional radiology.  Br J Radiol; Nov; 68(815): pp 1215-20.   6. Vlietstra RE, Wagner LK, Koenig T, Mettler F (2004) Radiation burns as a severe Complication of Fluoroscopically Guided Cardiological Interventions. J. Interv Cardiol; 17(3); pp 131-142.7. Broadhead DA, Chapple CL, Faulkner K, Davies ML, McCallum H (1997). The impact of cardiology on the collective effective dose in the North of England.  Br J Radiol; May; 70(833): pp 492-7.8. Koenig TR, Wolff D, Mettler FA, Wagner LK (2001). Skin injuries from fluoroscopically guided procedures part 1, characteristics of radiation injury. Am J Roentgenol. Jul; 177(1); pp 3-11.9. Koenig TR, Mettler FA, Wagner LK (2001) Skin injuries from fluoroscopically guided procedures part 2, review of 73 cases and recommendations for minimizing dose delivered to patient. Am J Roentgenol.  Jul; 177(1); pp 13-20.10. Carroll E & Brennan PC (2000). The establishment of diagnostic reference levels for barium enemas and barium meals. British Journal of Radiology; 73(supp):  10111. Rainford L, Stack J, Brennan PC (2001). Optimisation of X-ray beam filtration as a method of patient dose reduction whilst maintaining image quality. Radiography Ireland; Vol 5 Issue2, August 2001, 25-2712. Martin CJ, Darragh CL, Mc Kenzie GA, Bayliss AP (1993). Implementation of a programme for reduction of radiographic doses and results achieved through increases in tube potential. Br J Radiol: 66,228-223.13. SI 478 of 2002. European Communities (Medical Ionising Radiation Protection) Regulations 2002. Government Statutory Office: Dublin14. National Radiological Protection Board, Doses to Patients from medical X-ray examinations in the UK-1995 review. NRPB Chilton. 15.  RCR/NRPB 1990 Patient Dose Reduction in Diagnostic Radiology Doc. NRPB 1 No. 3 (NRPB, Chilton)16.  International Commission on Radiological Protection 1996. Radiological Protection and safety in medicine ICRP. Publication 73 Annals of the ICRP 26 No. 217.  Institute of Physics and Engineering in Medicine- Report 88. 2004. Guidance on the establishment and Use of Diagnostic Reference Levels for Medical X-ray Examinations.18.  Ionising Radiation (Medical Exposure) Regulations 2000, Statutory Instrument 2000 No. 105919. European Commission. Council Directive 97/43/EURATOM of 30th June 1997 on health protection of Individuals Against the Dangers of Ionising Radiation in Relation to Medical Exposure. Official journal of the European Communities, L 180:22-7 (1997) 20.  Hart D, Hillier MC, Wall BF, Doses to Patients from Medical x-ray Examinations in the UK-2000 Review. National Radiation Protection Board –W14. 21. The Linear No-Threshold (LNT) Debate, in Medical Physics, Vol. 25, No. 3, March 1998: Strom et al 22.  Vano E, Arranz L, Sastre J M, Moro C, Ledo A, Garate M T,  Minguez I. Dosimetric and radiation protection considerations based on some cases of  patient skin injuries in interventional cardiology. The British Journal of Radiology 71 (1998), 510-51623.  Nationwide Inpatient Sample Release 6 for 1997, compiled by HCUPnet, Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality, Rockville, MD, http://www.ahrq.gov/data/hcup/ (​http:​/​​/​www.ahrq.gov​/​data​/​hcup​/​" \t "_parent​) (August 2000). 24. Padovani R, Bernardi G, Malison M R, Vano E, Morocutti G, Fioretti PM. (2001) Patient dose related to the complexity of interventional cardiology procedures. Radiation Protection Dosimetry. Vol. 94, No.1-2, pp. 189-192 25. The DIMOND EU PROJECT. E Neoffotistou et al, Preliminary reference levels in Interventional Cardiology 

A survey of radiation dose and image optimisation for cardiac interventional procedures

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A survey of radiation dose and image optimisation for cardiac interventional procedures

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