Contents lists available at ScienceDirect Physica Medica journal homepage: www.elsevier.com/locate/ejmp Original paper Conversion factors to estimate effective doses from kerma area product in interventional cardiology. Impact of added filtration Eliseo Vano a,b, ⁎ , Roberto M. Sánchez a,b , José.M. Fernández a , José I. Ten c a Medical Physics Service, Hospital Clínico San Carlos and IdISSC, 28040 Madrid, Spain b Radiology Department, Medicine Faculty, Complutense University, 28040 Madrid, Spain c Diagnostic Radiology Service. Hospital Clínico San Carlos and IdISSC, 28040 Madrid, Spain ARTICLE INFO Keywords: Interventional cardiology Patient dose Effective dose Population dose Filtration ABSTRACT There is a large variation in the factors used to estimate effective doses from kerma area product (KAP) for interventional cardiology. These factors are required to estimate population doses. This paper presents the re- sults for this conversion factor for cardiac procedures using tissue weighting factors of ICRP-103 and the impact of the added copper filtration in the X-ray beam. The data from 925 cardiac procedures and 75,347 radiation events were collected from two angiography laboratories using the DICOM Radiation Dose Structured Reports (RDSR). Effective doses were calculated with Monte Carlo software and the dosimetric, technical and geometrical information included in the RDSR. In one laboratory, with an X-ray system without Cu filtration for the cine runs, a factor of 0.21 ± 0.05 mSv/ (Gy·cm 2 ) was obtained. In other laboratory, incorporating a patient dose reduction technique, and 0.4 mm of Cu filtration for cine runs, the conversion factor was 0.29 ± 0.05 mSv/(Gy·cm 2 ). The analysis of the radiation events for the different Cu filtrations (0.0; 0.1; 0.4 and 0.9 mm) resulted in conversion factors of: 0.16; 0.27; 0.34 and 0.40 mSv/(Gy·cm 2 ) respectively. The estimation of effective and population doses from KAP should take into account the Cu filtration in the X- ray beam. For the X-ray system with patient dose reduction technique, using 0.4 mm Cu for cine runs, the global conversion factor increased by 38%, from 0.21 to 0.29 mSv/(Gy·cm 2 ) in comparison to the standard X-ray system with a protocol that did not include copper filtration for cine acquisitions. 1. Introduction The X-ray systems used for interventional procedures are able to give patient exposure indexes during and at the end of the procedures. In the most recent models, the X-ray systems are able to transfer this dosimetric and other technical and geometrical information to the DICOM radiation dose structured reports (RDSR). The dosimetric data, kerma area product –KAP– and air kerma –AK– at the patient entrance reference point [1], are used for optimisation of the radiation protection of patients. Now, with the information con- tained in the RDSR (kV, filtration, C-arm angulation, radiation field size, etc) the optimisation actions may be improved. For specific clinical indications, their median values should be periodically compared with the diagnostic reference levels (DRLs) [2]. Population doses are estimated using the frequency of the proce- dures and the quantity effective dose. The Monte Carlo software [3] allows organ and effective doses to be calculated from the primary dosimetric quantities reported by the X-ray systems, from all the in- formation on the X-ray beam quality (kV and filtration) and from other geometrical and technical factors. According to the recommendations of the International Commission on Radiological Protection (ICRP), effective doses should not be used to estimate individual radiation risks to patients but may be useful to compare the relative risks when different imaging procedures with different modalities (e.g. X-ray catheterization, computed tomography and nuclear medicine) are performed on the same patient [4,5]. The new European Directive on Basic Safety Standards [6] requires patient dose audits and the use of DRLs for optimisation, and in addi- tion, this regulation requires that “population doses derived from medical exposures be estimated for radiodiagnostic and interventional radiology”. Such a requirement makes it necessary to estimate effective doses and the frequency of the procedures. The UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) collects and periodically publishes the worldwide https://doi.org/10.1016/j.ejmp.2019.11.013 Received 17 September 2019; Received in revised form 24 October 2019; Accepted 15 November 2019 ⁎ Corresponding author. E-mail address: eliseov@med.ucm.es (E. Vano). Physica Medica 68 (2019) 104–111 1120-1797/ © 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved. T