Establishing the Greek National Reference Levels for Interventional Cardiology procedures

Transcription

1 Establishing the Greek National Reference Levels for Interventional Cardiology procedures George Simantirakis*, Christina Koukorava, Maria Kalathaki, Christos Pa<ilis, Ioannis Kaisas, Sotirios Economides, Costas J. Hourdakis and Vassiliki Kamenopoulou Greek Atomic Energy Commission * T: , F: , E: gsim@eeae.gr

2 Contents of the presentation Introduction Methods Measurements related to the performance of the X- ray systems Reference Levels related to the clinical procedures Results Discussion 2

3 Introduction The frequency of <luoroscopically guided Interventional Cardiology (IC) procedures has seen signi<icant growth over the past decade. The extended use of these procedures raises various radiation protection issues, as they result in high radiation dose to the patient as well as to the medical personnel. Speci<ically the dose to the patients skin can, in some cases, even exceed the threshold of tissue reactions. As a consequence, optimisation of radiation protection on IC procedures is of great importance. Vliestra et al. (2004) 3

4 Introduction Directive 97/43/EURATOM introduced the concept of Diagnostic Reference Levels as a tool for optimisation for typical examinations. They are de<ined as dose levels in medical radiodiagnostic practices to patients of standard- sized groups or standard phantoms. Although IC procedures can hardly be standardized because of the variations of patients anatomy and pathology, the adoption of Reference Levels (RLs) for these procedures seems feasible and has been investigated in the literature. The establishment of RLs in image guided interventional procedures at a national level is required in the recent revision of the BSS*. * ΙΑΕΑ (2011) Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards Interim Edition, Safety Series No. GSR Part 3 (Interim), IAEA, Vienna 4

5 Introduction The purpose of this speech is to present the results of a national survey that was performed in Greece for the establishment of national RLs for the most common IC procedures. 5

6 Methods Two types of Reference Levels were set, as suggested in the literature*: RLs related to the performance of the X- ray systems used in IC, RLs related to the clinical procedures. For this purpose, the study included collection and analysis of clinical data as well as measurements related to the performance of the X- ray systems used in IC. * Vano E, Gonzalez L (2001) Approaches to establishing reference levels in interventional radiology. Radiat Prot Dosimetry 94: * Padovani R et al. (2008) Reference levels at European level for cardiac interventional procedures. Radiat Prot Dosimetry 129:

7 Measurements related to the performance of the X- ray systems The performance of 30 systems that are used in IC was evaluated in respect to the following parameters: Phantom entrance dose rate during <luoroscopy Phantom entrance dose rate and dose per frame during image acquisition (CINE) Air kerma- area product (P KA ) meter accuracy Image quality [Low Contrast Sensitivity (LCS) and High Contrast Resolution (HCR)] 7

8 Measurements related to the performance of the X- ray systems Dose measurements* 20 cm of water 60 cm 90 cm Typical PA projection Measurements were performed without magni<ication(20-25 cm FoV) and with magni<ication to cm FoV. All exposure parameters (<luoroscopy and CINE mode, pulse and frame rate, <iltration etc.) during the measurements were those that are used in typical clinical cases on each system. The accuracy of the P KA meters was evaluated using the beam area method (i.e. by measuring the air kerma and the <ield area at the plane of measurement) without the presence of the patient table (free- in- air). * International Atomic Energy Agency (2007) Dosimetry in Diagnostic Radiology: An International Code of Practice. Technical Reports Series 457, IAEA, Vienna 8

9 RLs related to the clinical procedures The total <luoroscopy time and the P KA of a total of 5250 IC procedures from 26 hospitals were recorded and analyzed. Classi<ication of procedures: i) diagnostic Coronary Angiography (CA), ii) Percutaneous Coronary Intervention (PCI): any therapeutic procedure (with or without a diagnostic component)* iii) Pacemaker Implantation (PMI) iv) Radiofrequency Cardiac Ablation (RFCA). *ΙΑΕΑ (2009) Establishing Guidance Levels in X Ray Guided Medical Interventional Procedures: A Pilot Study. Safety Reports Series No. 59, IAEA, Vienna. 9

10 RLs related to the clinical procedures The P KA meter accuracy that was assessed during the systems performance evaluation, was used in order to investigate the need for applying corrective factors to the collected data. The minimum sample size for each procedure was 30 patients per hospital. For each type of procedure, the mean <luoroscopy time and P KA values were calculated for each hospital. The rounded 3 rd quartile of the mean values was set as the RL for each procedure.* *Hart D, Hillier MC, Wall BF (2002), Doses to patients from medical X-ray Examinations in the UK 2000 Review, NRPB-W14 edition, National Radiation Protection Board, Chilton. 10

11 Results Systems measurements 120,00 100,00 Fluoroscopy - Phantom entrance dose rate FoV Signi<icant differences 1/ FoV on the dose rates and dose per frame values were observed, even for systems of the same type: 80,00 mgy/min 60,00 40,00 20,00 0,00 A1 A2 B1 B2 C1 C2 C3 C4 C5 C6 C7 C8 D1 D2 E1 F1 G1 H1 H2 H3 H4 I1 I2 I3 K1 L1 L2 L3 L4 M1 Each letter on the horizontal axis represents a specific system model 11

12 Results Systems measurements CINE - Phantom entrance dose per frame 1/ FoV FoV μgy/fr A1 A2 B1 B2 C1 C2 C3 C4 C5 C6 C7 C8 D1 D2 E1 F1 G1 H1 H2 H3 H4 I1 I2 I3 K1 L1 L2 L3 L4 M1 Each letter on the horizontal axis represents a specific system model 12

13 Results Systems measurements The accuracy of all P KA meters lied within the ± 35% tolerance* Eight systems presented inaccuracies greater than the estimated uncertainty of the P KA measurement (6.4%). A respective correction factor was applied to the clinical P KA data that was collected from these systems. Flat Detector systems presented better high contrast resolution against those with Image Intensi<iers (mean values were 2.4 lp/mm and 1.5 lp/mm respectively). No signi<icant differences were observed for the rest of the measured parameters. * International Electrotechnical Commission (2010) Medical electrical equipment - Part 2 43: Particular requirements for the basic safety and essential performance of X-ray equipment for interventional procedures, IEC Report No Ed. 2.0, Geneva. 13

14 Results Clinical data PCI - Mean DAP values per center PCI and RFCA were the procedures with the highest P KA mean values (112.0 mgy cm 2 and 98.3 mgy cm 2 respectively). 200 Gy cm

15 Results Clinical data 250 RFCA - Mean DAP values per center 200 Gy cm pps fluoroscopy (provides adequate image quality for RFCA) 15

16 Suggested national RLs Other studies 1.CA: 50 Gycm 2, PCI: 125 Gycm CA: Gycm 2 PTCA: Gycm PMI: 38 Gycm 2, 27 Gycm 2 1. ΙΑΕΑ (2009) Establishing Guidance Levels in X Ray Guided Medical Interventional Procedures: A Pilot Study. Safety Reports Series No. 59, IAEA, Vienna. 2. Neofotistou V et al. (2003) Preliminary reference levels in interventional cardiology. Eur Radiol 13: Padovani R et al. (2008) Reference levels at European level for cardiac interventional procedures. Radiat Prot Dosimetry 129: Aroua A et al. (2004) Adult reference levels in diagnostic and interventional radiology for temporary use in Switzerland. Radiat Prot Dosimetry 111: Hart D et al. (2002), Doses to patients from medical X- ray Examinations in the UK 2000 Review, NRPB- W14 edition, National Radiation Protection Board, Chilton. 16

17 Discussion The wide range of the dose rate and dose per frame values of the systems that were evaluated, represent differences not only in the systems dosimetric performance, but also in the protocols used by the operating staff during the clinical work. Optimisation by changing the systems settings used during the clinical practice seems feasible in some cases. Scaling of the RLs according to the complexity of the procedures was not feasible during the present study (no such information was available in the collected data). Each individual facility should compare its own values against the suggested RLs, after applying an adjustment for complexity to the local data. 17

18 Procedure complexity PTCA Complexity Index (CI)* CI = No.ves 1 + No.LesType No.Occl3m No.SevTort No.BifSt 0.58 (a) Simple PTCA procedures: CI = 1; (b) Medium complex PTCA procedures: 1 < CI < 2; (c) Complex PTCA procedures: CI > 2. *ΙΑΕΑ (2009) Establishing Guidance Levels in X Ray Guided Medical Interventional Procedures: A Pilot Study. Safety Reports Series No. 59, IAEA, Vienna. PMI: type of implanted device (conventional or biventricular) RFCA: type of treated arrhythmia Padovani R et al. (2008) Reference levels at European level for cardiac interventional procedures. Radiat Prot Dosimetry 129:

19 Discussion Future re- evaluation of the suggested RLs should take into account The complexity of the procedures The number of acquired frames per procedure The patient s morphometric characteristics (e.g. Body Mass Index) More information: Simantirakis G., Koukorava C., Kalathaki M., Pa<ilis C., Kaisas I., Economides S., Hourdakis C. J., Kamenopoulou V., Georgiou E. "Reference levels and patient doses in interventional cardiology procedures in Greece", Eur Radiol (2013) 23:

20 Thank you Greek Atomic Energy Commission P.O Box Agia Paraskevi 15310, Athens T: F: E: facebook.com/eeaegr twitter.com/#eeaegr 20