Flat detector versus image intensifier in cardiology. Why are patient doses initially higher?

Our purpose in this paper is to study the differences in patient doses imparted using dynamic flat detectors (FD) as opposed to using image intensifier (II) technology for interventional cardiology within two different European Centres, and then analyse the reasons for such differences. Several x-ray systems from two different manufacturers equipped with FDs ands IIs were used over the last 4 years in two separate interventional cardiology services both subject to common quality assurance programmes agreed during the European SENTINEL Coordination Action. The same team of cardiologists worked simultaneously or in sequence in laboratories equipped with FD and II technologies. No differences were found regarding specific patient characteristics in the different catheterisation laboratories. Kerma area product (KAP) values were measured and analysed for large samples of procedures. In centre M, median KAP values were consistently and significantly higher with FD than with II, with percentages of 55-113%. In centre U, the KAP increase was 7-29% comparing FD with II. Without a dedicated optimisation programme, initial patient dose values can result significantly higher with FD technology in comparison with II. This might be related to the use of non optimum initial setting protocols of the x-ray systems (dose per frame, pulses/s, filtration etc), bigger radiation filed sizes for FD and the scarce use of collimation and wedge filters in the new systems equipped with FDs. Preventing this problem and improving the management of patient doses warrant further studies. (author)